Understanding Solar Energy | Hacker News Reader

Understanding Solar Energy

construction-physics.com

261 pointschmaynard258 comments

Great article. Unfortunately his California duck curve graph only shows 2023. A graph including 2024 shows how batteries are dramatically flattening the duck curve:

https://cdn-ilcjnih.nitrocdn.com/BVTDJPZTUnfCKRkDQJDEvQcUwtA...

https://reneweconomy.com.au/battery-storage-is-dramatically-...

And similarly the battery prices are very outdated. I don't blame the author for using those estimates, I frequently do too just because getting access to current data usually requires paying money.

But making decisions on that data without understanding that current prices and near-term prices will be about half of that price will lead to bad decisions. And when thinking 5-10 years out, not taking the full exponential drop in battery and solar prices is beyond foolish.

Actual battery prices may be dropping but cost to install batteries to your solar installation in CA have not dropped - in fact they've gone up.

Not sure why this is the case.

This is by design in the regulatory infrastructure, from local permitting offices all the way up to CPUC and rate structures.

We pay about $3/W for solar installation in the US, but Australia pays about $1/W.

For batteries, there's still a supply crunch and the only people getting really good prices are those people who buy in huge bulk or are willing to take a risk on a lesser known manufacturer. If you want well-proven brands the prices can still be very high for small purchases, and a solar installer is not going to want to take a risk with a new supplier.

These systems are not super complex, most technical people could figure them out fairly easily, and in fact off-grid disconnected systems are really easy to do. It's the grid tie that will kill you or first responders to your house, we have made the process of setting the whole thing up very expensive because nobody on the regulatory side has an incentive to make it straightforward and cheap. And since NEM3 killed solar in California, all the installers are barely scraping by and need to rely on very high margins on few projects.

> This is by design in the regulatory infrastructure

I don't see how this can be true. I installed my own ground mount array, and the costs directly attributable to regulatory infrastructure were about US$35 (for the permit). It would have been no higher if I had added batteries. The material costs were completely comparable with AU, CAN and UK pricing.

Perhaps you're arguing that the certification and licensing regulations for paid installers drives the installation cost up (i.e. that labor costs for US solar installs are too expensive) ?

> and the costs directly attributable to regulatory infrastructure were about US$35 (for the permit)

That may be true if your time is free, but for a company, they must deal with a permitting scheme for every county and city that they do business in. Additionally, unpredictable changes to rate structures will drastically change the demand for solar in areas year to year, and so the solar installers that survive are the ones who are well attuned to that change, and pounce on new markets that are suddenly opened up by new rate structures that make solar easy to finance or pay off quickly. That means that about $1/W of the $3/W that installers charge actually goes to customer acquisition costs.

Most areas do not have super onerous labor requirements for solar installers, and generally the contractor licensing part is quite reasonable. But perhaps insurance like workers comp and disability is a lot higher in the US than in Australia.

I'm surprised that US tariffs have not resulted in higher materials costs than in the other anglophone countries!

I installed my system 5 years ago, when no particularly unusual tariff structure was in place.

Your reply seems to indicate that "regulatory infrastructure" is not responsible for the bulk of the cost, but rather traditional concerns of for-profit business, in this case, the business of solar PV installation.

The same price difference exists with things like heat pumps - I've seen people in the US talking about installing single-head Japanese brand mini-split systems for US$5000 to even over US$10,000, when I can get the same sized units fully installed for AU$1600 to AU$2500 (about US$1000 to US$1600).

Just makes no sense why it should be that different. The units seem to cost similar prices in Europe to what we pay here in Australia so why is it so much more in North America? I assume part of it is that they are not quite as common but it still boggles the mind.

Fossil fuel companies choose the president and legislature in the US—not exclusively, but they do evidently at least have veto power, and the current president campaigned on an anti-renewables platform which he has delivered on. Bipartisan tariff policy in the US is basically completely locking Chinese solar panels and EVs out of the market, doubling the costs of those products to US consumers and sabotaging any chance of future competitiveness in heavy industry. I don't know if the same thing is happening with Japanese air conditioning systems.

Drives me bananas. Aussie in the US - I’m very reluctantly going to spend 4-5x what I would pay in au for a heat pump. I have no explanation for why it can possibly cost so much more, it’s infuriating. You can DIY for a lot less but it’s a big complicated project

> And when thinking 5-10 years out, not taking the full exponential drop in battery and solar prices is beyond foolish.

The curve on solar is gradually getting flatter, though. Lazard's last LCOE report even saw it increase, partly because of inflation.

PV panels have dropped in cost in nominal euros by 21% over the last year, which is roughly the long-term trend since solar became profitable without subsidies around 02014: https://www.solarserver.de/photovoltaik-preis-pv-modul-preis...

Possibly you are only looking at prices inside the US, where anti-renewable-energy regulations drive the cost of solar energy through the roof.

Which does not really matter anymore though. In almost all installations the panels are already negligible for the total cost. This is especially true for rooftops and small installations

People often point to how electric motors revolutionized industrial productivity, but not until about 30 years after their introduction. Because that's when factories were redesigned around the flow of products instead of the flow of line shaft power, using small electric motors at every workstation instead of just powering the line shaft with a big one. You might have pointed out at the time that electric motors had a negligible cost compared to the factories they were installed in, but from that you should have concluded that huge changes were in the works, not that further reductions in motor costs were unimportant.

Today the module cost is far from negligible (the article shows SEIA data showing that, even in the US, modules are a third of the cost of recent utility-scale solar) and it's only small because the other parts of the installation are badly lagging behind. If you need to heat or cool your house or train your neural networks, you really just need the energy those panels can provide, and somewhere to store it. Other balance-of-system costs like microinverters, racking, most wiring, transmission, design, civil engineering, land, installation labor, and regulatory approval are only useful as means to that end; they are not strictly necessary to receive the benefit.

If avoiding those forms of waste means you can get energy for a negligible cost, more and more people will find ways to do it.

How can you avoid them?

Well, you can avoid the cost of inverters by using low-voltage dc power, as off-grid enthusiasts, RV retirees, and Google data centers have been doing for decades. You can avoid racking by laying the panels on the ground, as the article mentions, or hanging them on an exterior wall of a house or an existing fence. These also avoid civil engineering and land and labor costs, and also falling off your roof. You can't avoid wiring but you can reduce its cost by using higher voltages (even low-voltage dc can use 48 volts instead of 12) and mounting the panels close to the point of use. You avoid transmission (and distribution) costs by siting the panels onsite instead of in a faraway solar farm. You avoid design costs by buying an off-the-shelf modular power system instead of paying someone to design a custom one. You avoid regulatory approval most obviously by breaking the law, probably more feasible in a slum apartment or an RV than in a utility-scale power plant, or by avoiding doing regulated things like connecting to the electrical grid or running 120VAC or 240VAC wiring.

This clearly points to a near future of ridiculously abundant energy, at what we would have previously considered a negligible cost.

> hanging them on an exterior wall of a house or an existing fence

You can avoid racking by installing them as the fence when you install a new fence.

I mean you don't literally, but the installation cost is a cost you were going to pay anyways.

Maybe so. It might depend on the winds in your area.

To expand on this 21% yearly rate, my notes say that in July 02014 the price on the Solarserver page was €0.55/Wp, presumably for the "low cost" category, which is now (February) at €0.070/Wp. That drop by a factor of 7.86 over 10 years and 8 months (128 months) works out to 1.62% per month (√√√√√√√7.86 ≈ 1.0162) which is coincidentally 21.3% yearly growth in watts per euro (a 17.6% cost reduction per year).

This is staggering, even at its current level. €0.070/Wp at a nominal 15% capacity factor is €0.46/W; at a 5% interest rate, assuming no aging, that's €0.74 per gigajoule, or, in the quaint non-SI units more commonly used for trading energy, €0.0027/kWh†, €0.029 per liter of diesel, 10¢ per gallon of gasoline, or US$4.60 per barrel of oil. And it's pure, undiluted exergy; you incur no Carnot losses to use it to drive motors or train neural networks.

The current WTI oil price is US$68.20 per barrel of oil: https://markets.businessinsider.com/commodities/oil-price?ty.... That makes solar energy fourteen times cheaper than oil, or more than thirty times cheaper if you're using it for transport or electricity.

The US's current policy of imposing prohibitive import tariffs on solar panels is similar to the Arab oil embargo of 01973, but self-imposed, attempting to prolong the energy crisis that began at that time.

______

† Not €0.27/kWh or even €0.027/kWh. €0.0027/kWh. 0.28¢/kWh.

Hot water tank heated by electricity and powering on at noon is flattening curve. You can say hot water tanks are cheapest, simplest and fastest deployed energy storage device.

Solar + hot water tank can provide any house in US with 100% solar hot water (from PV!) for 80% of time, remaining 20 % of time you can have 10-99% solar heated water.

So we should focus on saying to people that if they buy solar and add electric heating element to hot water tank, then PV system will pay itself much sooner and their batteries will last longer. Becasue it is known and predictable load, you need hot water every day. And hot water is order of magnitude more energy then TV, lighting...

By lowering household usage like this we can make energy transition faster, cheaper.

Also proper construction - house heated only 10 days in a year - https://www.youtube.com/watch?v=5KHScgjTJtE

I installed PV solar hot water at my house, works great. Makes about $2 a day worth of power.

Congrats, using as much energy directly on site is crucial for fast and cheap energy transition of economy.

Converting a gas water heater to electric and/or solar is one of the best bang for the buck on decarbonization too. Something that should be done before buying an electric car or swapping out your gas furnace for a heat pump. Though I'm terrible at following my own advice, I still have a gas water heater, just because I needed to replace my car and furnace before I needed to replace my water heater. That said, the sunk cost fallacy applies to carbon emissions just as hard as it does to dollars so I have little excuse for not replacing it except laziness (and space on the breaker panel...)

Is it a fallacy though? It doesn't make sense to buy a new EV if you still have a gas car that's working fine. In the same vein, I wouldn't want to throw out my gas furnace or water heater to replace with electric, creating waste and requiring the manufacturing of a new unit

That only applies if you're only going to get less than 1 year of use out of a heat pump. A heat pump has an "embodied CO2" of 1.7t, which is about the same as the annual CO2 emissions of a gas furnace.

Can you explain how it's not a fallacy? Compare your lifetime emissions of replacing a gas car with an EV now versus at the "end of life" of the gas car. Emissions will always be lower if you replace now rather than later.

Imagine if everybody switched to EVs right now, en masse. Emissions over the next decade, and every subsequent decade, would be massively lower. Waiting for every gas car to reach end of life before switching is always going to be higher emissions, always.

Similarly, the "waste" already happened when the gas heater was manufactured. There's no additional waste when it's decommissioned. It's a sunk cost, there's no getting that back. The only question is if you switch to lower emissions now, or you switch to lower emissions later.

Now, if you bring money into it, sure, there could be a financial motivation to keep emitting higher amounts of emissions. But if you take monetary considerations out of it, it's always better to stop emitting sooner rather than later.

I'd love to have some serious push back against this. The best I've ever got is "that doesn't sound right..." without any engagement with the quantitation or the ideas. Which is exactly what I would expect if it was a fallacy.

I think you’re assuming when you switch to EV the ICE car disappears. But more likely it got traded to someone else who has less money, eventually making it possible for someone to own a car who otherwise wouldn’t have.

So the emissions stayed the same and you added the carbon embedded in the new EV.

What would that person have bought otherwise? Another ICE. If Person A kept the ICR there would be two people driving them instead of one ICE, one EV.

I do really appreciate shifting this from the "the consumer must make the right choice" to "what choices result in overall better outcomes" but we must do the full accounting.

not necessarily. if he bought your car and traded up from a real clunker with worse fuel efficiency the net result is likely better.

And maybe the clunker was junked, orrrrr it was subsequently resold, or put on a ship to the global south and it’s clunkers the whole way down…

Cars don’t last forever, and shipping junk cars from the US to the global south doesn’t make economic sense. Eventually there’s a bottom of the chain.

It does and they do. A used car is cheaper to source than a new one which means it can be sold to more consumers at higher margin.

Every taxi I rode in the Bahamas was a 2nd gen Jeep Grand Cherokee with the CEL on.

The bottom exists, but it’s not here.

I don’t doubt used cars are shipped out of the US, but I’m pretty confident quite a few cars are junked in the US as well, as any junkyard demonstrates. I’d be pretty surprised to hear that junk cars (a subset of used cars) are shipped and resold.

> So the emissions stayed the same and you added the carbon embedded in the new EV.

Well no, there will be a chain of people all upgrading their cars to better ones. The final car will drop off the bottom of the chain, so you trade an EV for what is likely to be the worst performing car environmentally.

> The final car will drop off the bottom of the chain

Maybe not. The $500 used car lot will take them, and some will get shipped off to third world countries.

But now you're dealing with probabilities, weighed against the certainty of the original EV purchaser emitting less.

Try this: if everyone in the US suddenly purchased EVs, and ditched their ICE cars, flooding the market with old ICE vehicles, would emissions decrease in the world or increase? I think it's pretty clear that the vast majority of the old ICE vehicles would be junked, and there'd be marginally more vehicle-miles-travelled, so the huge wins of everyone using EVs would counteract any increase in vehicle miles from suddenly having cheaper ICE available around the world.

So I would argue that the single person doing that action would have the general same trend as if everyone did it.

> But now you're dealing with probabilities, weighed against the certainty of the original EV purchaser emitting less.

Welcome to public policy.

> Try this:

No, I’ll stay in the real world. Your thought experiment isn’t possible, and extrapolating from it isn’t useful.

> Maybe not. The $500 used car lot will take them, and some will get shipped off to third world countries.

If you're saying electric cars are pointless, and we should keep making ICE cars, because for a period of transition from ICE to EV some older ICE cars will go overseas, then I'm not sure there's much else to say. I disagree that that's good logic, I suppose.

Yes, but same logic can be applied to EVs.

Someone that that switches to EV today will pass that EV to a second owner down the line. The sooner the fleet starts switching to electric, the sooner the carbon emissions, primary energy needs, gas usage and particle emissions dive.

> But if you take monetary considerations out of it, it's always better to stop emitting sooner rather than later.

No, it might or might not, depending on (a) the embodied emissions of creating the new product and (b) how soon it will be replaced by something even more efficient.

It's easiest to understand the importance of point (b) by going to extremes: Suppose that, every week, a new model of EV comes out that uses 99% as much energy as the previous year's model. If some nonzero proportion of electricity is generated from fossil fuels, then ignoring point (b) would imply that the rational thing to do would be to buy the new car each week, regardless of how much CO2 went into building it.

You’re incorrect, buying a new EV when you have an ICE car doesn’t actually destroy the ICE vehicle.

There’s a bunch of different possibilities to consider, but if you drive more than the average person buying an EV and selling your ICE is great for the environment. If you rarely drive then keeping an old ICE car out of the hands of a frequent driver has real value etc.

As to the environmental impact vs retrofitting an ICE vehicle into an EV, the grid has gotten a lot cleaner over time so many of the old assumptions around EV’s are outdated. Comparing the emissions from extracting, transporting, refining, and then burning gas vs the same with EV’s built with a cleaner grid and more electrified infrastructure now heavy favors EV’s. And these calculations just keep favoring EV’s more every year.

If you want to DIY a solar PV water heater I made a whole website about it with instructions and a simulator to estimate what your payback period could be.

https://www.pvh2o.com/

Resistance heating is so 20th century. Granted, you likely cannot do a DIY air source heat pump build, but the COP is so high for such systems, that it's probably worth it to just buy it.

My mom had a Heat Pump water heater at her house and I was always having to go and fix it or clean the filter. It would start beeping loudly in the middle of the night when it wanted attention. The hot water was frequently not very hot.

Hopefully the new heat pump water heaters are better. The advantage of resistance heating is simplicity and cost, with no moving parts. Solar panels are so cheap now they make it hard to justify the expense of the heat pump, assuming you have room to mount the panels.

a COP of 4 can certainly justify having to install 3-4x less panels.

it disappoints me (but thrills me) that improvements in PV efficiency and cost have made solar thermal hot water more or less pointless.

Heat pumps have COP of 4 when reaching temperatures needed for room heating. Hot water is way hotter than that. The more the difference between outside air and heated water, the less the COP becomes. I don't expect COP of 4 at 200 fahrenheit

True, but you never need 200F for DHW. This is even dangerous (scalding) and harmful to the piping. Typical temperatures for heat pump derived DHW are around 120F (45-50C), with some (bi)weekly cycles to avoid legionella build up at 150F(65C). Your statement is generally true, because a heating installation that is optimized for heat pump works at 85-100F, however in practice not many installations in old buildings are like that.

If your concern is storage you want as hot as possible, less boiling. Thermostatic mixing valves can bring the temp down to a safe temperature for use.

Losses are higher but you store more energy per L, which is often the limiting factor.

But you only need to store enough for a day or two. So you can alternatively just go bigger

Is energy per liter often the limiting factor? Suppose a 70m² apartment with 3-meter ceilings costs US$3000 a month because it's in an expensive city center like San Francisco or Manhattan. That's still only 17¢/liter/year. Expanding your hot water storage space from 45 liters to 200 liters consumes space worth US$27 per year of your rent. Even that cost seems far too low to be a limiting factor, and the vast majority of people live somewhere much cheaper than that.

I think that what actually costs money is not the space but the tank. Higher temperatures mean not only more expensive materials and shorter lifetimes for tanks and piping but also higher conductive losses.

As hot as possible is not the way to go. Heat pump COP will degrade dramatically if you try to boil the water. It is not even possible with the popular refrigerants (R32, R410a and even R143a), because they will exceed their critical temperature. If you cannot afford the space for a bigger DHW tank, then there are two options:

1. Consider PCM heat storage (still relatively new technology, but works well with heat pumps)

2. Maybe the problem shall be solved at the building level, not individual apartments.

Problem being that electric water heating is a lot more expensive in e.g. Germany where gas prices are lower than electricity prices per kWh delivered. (~12 vs. 39 eurocent per kWh)

So blindly converting a gas water heater to electric will roughly quadruple your water heating cost.

Only a problem when you're limiting yourself to resistive heating. Heat pumps can heat water, not just air, and are several times more efficient than resistive.

I've got a heat pump, and I'm in Germany.

Also, if you're in Germany, you can get a balcony PV system from half the supermarkets a few hundred euros, and those are designed to be installed DIY without needing an electrician. Limited power, sure, but way cheaper than €0.39/kWh delivered:

• https://www.lidl.de/p/vale-balkonkraftwerk-ecoflow-820-w-800...

• https://www.kaufland.de/product/502015379/?search_value=balk...

Your first link seems to be 349€ for 800Wp including microinverter. German utility-scale PV has a capacity factor averaging about 12% IIRC, but presumably a balcony system will be lower because it isn't optimally angled for the sun, say 8%. Then that's about 64W, which is 560 kWh per year. 349€ over 10 years would be 35€ per year, about 0.06€/kWh.

That's still about six times the cost of wholesale low-cost solar panels: https://www.solarserver.de/photovoltaik-preis-pv-modul-preis...

64 watts is about 40–50 liters per day of hot water heated resistively, presumably closer to 150 liters per day with a heat pump. But it seems like the heat pump is only saving you the 700€ for two more such balcony systems, assuming you have the space. Moreover, you don't need a microinverter for a resistive heater.

Oh indeed, balcony systems are small and limited — the constraints that led to them are: (1) DIY-safe, (2) useful for rented apartments (limited window or balcony fencing space, may not be allowed to fix something to an exterior wall).

I'm not sure if you're allowed to just resistively dump an off-grid PV system into a resistive heating system, but I guess if you did, you could indeed save on the cost of the inverter.

I believe that even in Germany you can connect a low-voltage solar panel to a battery or heating element without any licensing approvals beyond CE. Low-voltage wiring poses much less risk of electrical shock and is consequently exempt from most safety regulations.

efficiency of no MPPT is around 10 percent lower then with MPPT system so no issue. 2000 watt is maybe max what you can have on balcony - physical size, and 2000 watt inverters are like 20 $. well connecting anything to grid is/should issue, offgrid noone cares.

You might be able to hang an additional balcony system out a non-balcony window or something, or just keep it inside the window. Less insolation, but maybe not so much less that it's unprofitable.

Interesting note: this is about six times cheaper per watt than residential solar systems in the US.

We actually do have a Balkonkraftwerk im Garten :-)

Now that the sun is out for longer periods each day we are "wasting" energy to the grid a lot. I don't really see how to capture that energy though.

1. Buying a battery quickly shifts the break even points to decades. Without a battery I estimate 3-4 years. 2. I would love to heat water, but renting a place limits my options a lot. I was looking at electrical boilers to supplement the gas heater. But we are limited on space for small heaters below the sink and big heaters in the main water path. (Also we can't change the plumbing for legal reasons.) 3. The next best thing is some imaginary insulated water heating kettle that I can control to only use exactly the excess energy. No idea if such a thing exists.

You should calculate the battery parts again. I'm currently installing mine in Germany and the cost parity is getting close.

You probably thought of this already but we mostly do load shifting. If you have moderate PV output (like with balcony solar) that can probably use up most of your production.

Consider running the dishwasher (if you have one) or washing machine / dryer (if you don't dry that in the sun directly) during the day.

Granted, we work from home _a lot_ and also have an EV so it's a lot easier to do load shifting for us, but just shifting the dishwasher and washing machine to 'sunlight hours' already made a pretty decent difference.

Yeah, we do that. Given that most home appliances use more than 800W (even in Eco modes) we often use more than our production.

E.g. our washing machine uses 1000W over a prolonged period of time which would be perfect to run on a sunny day. But it does so by switching the 2000W heating element so it averages to 1000W ...

So we repeatedly export 800W (without any form of reimbursement) and import the missing 1200W back.

And that is the case for all of our appliances. (I have a sensor to monitor that)

Don't know if more modern machines are better in this regard, our machines are about 5 years old now.

edit: I don't want to sound bitter about it. The Balkonkraftwerk works perfectly fine to power our base energy load.

solar pv heating.

my PV system is paid after 6 years of use. if i use current prices for energy. last two years market/spot prices were even higher than that. so in reality it was paid even sooner.

and pv system does not disappear as soon as it is paid, it continues to work. so i have next 4-10 years remaining of lifetime of a inverter.

so for next 4-10 years i am having 100% REALLY REALLY FREE hot water, again for 80% of time... etc vis original comment.

when inverter ends its life in next 4-10 years then i will buy new one, without changing panels. so payback time will be even quicker.

calculations/models of biggest engineers, experts, etc. do not involve thinking about using pv system after it is paid... ( not insult, just exposing state of things )

Yes, but ... A PV system is not accessible to many. We have a small 800W system in our garden, but for many the price or just getting permissions from their landlords makes a PV system unfeasible.

Also, if you are heating with solar you could heat water directly. But that path is also only available to house owners.

PV + heatpump maybe. PV + resistive heater yes. solar thermal is not worth price wise. solar thermal can be feasible only for big installations as is in stralsund, leipzig... - megawatts.

solar PV is order of magnitude cheaper in small systems (per actual provided output per year, not just rated wattage)

AND because hot water energy needs are much higher than for example tv, notebook etc, so after your hot water is heated, you can charge your devices with it, you can not do that with solar thermal. so if people size their systems for winter sunny day, they will have excess in summer so you can use that for other things like bikes, lawnmowers ...

of course there is ratio of people living in blocks of flats / townhouses and people living in family houses / rural, so every situation is unique. so townhouses should be connected to central heating network and heating network provider should chase efficiencies of scale, that is better, faster, cheaper for everyone ( europe / germany context ) if urban density does not allow otherwise.

similar situation with electric cars, a lot of people is crying that there are not enough chargers for them, those are "city" people, but in reality most people live in rural setting or family houses and in germany every house already has more than enough electrical capacity to charge from outlet, you can charge car from 2.5kW which is same wattage as most electric kettles. yes it charges over night (10 hours) only 100 km but every house can do that already. faster charger can be bought. of course situation in cities is quite different, you can not just put extension cord from window. which is feasible in rural setting / family houses. even in berlin roughly 50 % of people do not live in townhouses / high rises.

Not so great in areas with winter.

if it works in germany, czech republic, poland

which is higher latitude than 99.99999999% of USA or 80% of canada population

then it will work even in USA too.

Again read my first post, it is NOT about reaching 100% offgrid which is expensive, and nonsensical for most people

it is about reaching 100% offgrid for 80 % of time and 10-99% offgrid 20 % of time. Which is so cheap in europe that youre generating totally free energy after 6-7 years PV system paid for itself.

Slightly less convenient/has more impact on how we percieve our environment, but HVAC (the number 1 power use, hot water is #2), can also be a decently good battery, if your house is well insulated. Where I live, power is incredibly cheap over night, so I over-heat or over-cool my house (depending on season) overnight, and then let it gradually equilibrate during the day.

I realize that some people won't be willing to have a very warm/very cold house that gradually shifts to the more ideal comfortable range, but for people who are willing to deal with that (it personally doesn't bother me), it's a pretty easy way to shift a lot of power use and, if you have Solar or Time of Use billing, save a lot of money.

Yeah that too, but that has limits, for example european union regulates building industry in such way that every new build, rebuild has to be done in a way that your heating energy requirement is already lower than your hot water energy requirement. Because hot water energy usage can not go lower in current society, but buildings can be improved a lot. So yes as you said if building is modeled in software tools like OpenStudio ( Revit, archicad uses this sw developed in collaboration by NREL, ANL, LBNL, ORNL, and PNNL ) before build, to make building not waste energy and capture as much sun in cold period as possible then even such strategies can be used. You can not preheat/ precool 1870s handhewn cabin, all energy will be lost very fast. It sounds obvious to you and me but most people do not really understand this deeply enough to "click" in their heads.

time of use billing - tool to incentivie you to use "off-peak" power, but i guess it will be deprecated in favor of "realtime" billing in future, because there will be so much solar (almost zero $ per kWh on market) that your energy provider will incentivize you to draw energy during peak solar "activity" AND off-peak hours. it will be simpler for them to give you market price every 15 minutes window than 4hour window at same time every day.

> Because hot water energy usage can not go lower in current society

Couldn't heat energy in waste water be recovered? Or is that already maxed out?

noone recovers wastewater energy,

energy generated by big wastewater plants is methane from microbial activity. also waste water plant can not remove a lot of stuff like medicine, hormones...

you can construct wastewater tank with integrated coil connected to heat pump. so you can take all heat back. if you have house with integrated waste water treatment, this should be no brainer. houses with existing heat pumps can "just add another heat exchanger circuit"

but i do not personally like heatpumps because working fluid can be in orders of 10 000 times more harmful to greenhouse effect than co2. and compressors using CO2 as a working fluid are rare.

heatexchangers connected to vertical wastewater pipe are showed in tradeshows. but i do not understand how that makes sense price wise. im not sure they recover as much heat as advertised.

> noone recovers wastewater energy,

You seem to have concluded energy use for hot water cannot go lower by excluding any approach that would lower it, not because it's physically impossible, but simply because such technology isn't being used.

Isn't this a vacuous argument?

has PV finally overtaken solar hot water?

well just piping for hot water system is more expensive then PV panels.

But biggest expense is instalation costs(humans) so it depends how you calculate. But PV system can be used for hot water, tv, car, charging kids bikes, lawnmower etc. Solar thermal can be used only for hot water (or cooling if you use multistage heat pump but that is viable only in office buildings or hockey stadiums and such).

by multistage heat pump i meant https://en.wikipedia.org/wiki/Absorption_refrigerator

i.e. rv propane refrigerator.

How much does the piping cost?

even with tariffs in place, whole PV system will provide you more kWh per year

per $ invested

then solar thermal system.

rated output is not what you get 100% of time. price per performance is crucial. price per imaginary watts is nonsense.

You're probably right, but do you have some idea how much the piping costs for a solar thermal hot water system? Because that's what I was asking about.

Using a hot water tank as a battery is an incredibly simple idea. I wonder how much electric hot water heaters on a timer could flatten California's duck curve.

There’s a company doing that in Hawaii, I think it’s called “shift energy”. I interviewed with them, it seemed like a great operation, but a bit hobbled by being a startup in Hawaii. I respect it though, I’d do the same.

They have been controlling hot water tanks in New Zealand for decades… probably since the 70s. They use what they call a ripple signal by adding 400 hz on top of the 60 and then relays on your hot water tank detect the 400hz and switch it off

We also control (or used to control) our street lights in AoNZ using ripple control (it was implemented with a tuned reed relay in some towns). Back in the 70s friends built a ripple transmitter and sent morse across Ōtepoti by turning on/off their suburb's street lights (at 2am)

My hot water heats up in less than 2 hours and if I don’t fire it up at night I won’t have hot water in morning.

At this point getting some batteries would likely be cheaper than new boiler + plumber to install it.

It loses heat overnight, or you use all the hot water contents overnight?

Sun stops producing useful amount after 6pm which coincides with dinner and whole family taking a shower.

Increasing water heater capacity might be cheaper than increasing battery capacity.

New cylinder - 1.5k NZD + half day of labour (so another $500). My current one stores about 6-8 kWh.

15kWh battery - 5.5k NZD + and hour of DIY.

So technically battery is more expensive but more useful.

Also easiest with water heater would be cranking up the temperature, but I really hate dealing with scolding water coming from taps (especially with small kids around).

Another thing with battery I can charge with whatever solar excess I have, but with hot water my only option is 16A.

Either way I do not care ATM - I export using spot price which has been 2x of what I actually pay for power - https://www.emi.ea.govt.nz/Wholesale/Reports/W_P_C?DateFrom=...

Higher temperature hot water requires more expensive plumbing, too.

FWIW you can get thermostatic mixing valves that limits the maximum temperature of the water by mixing in cold water. Lets you run the tank hotter but have the same outlet temp. Fairly cheap I believe.

>Also easiest with water heater would be cranking up the temperature, but I really hate dealing with scolding water coming from taps (especially with small kids around).

Your water heater temperature isn't exactly my business but please look into sanitary norms on minimum safe temperature. Water heaters have standing water and bacteria might start living there if the temperature isn't sufficient. I think legionnaires' disease is one of the most prevalent dangers.

Can you legally put a 15kWh battery on your system without anyone signing off on it?

48 volts bby

Photovoltaic water heating is the worst possible idea (and use) for solar panels. Frankly, I have no clue why they are pushing this concept. Add to that electric stoves, ovens and cars and you have an expensive disaster in your hands.

Most of the homes around me have somewhere around 3.5 to 6.0 kW of installed solar. This is barely enough to support these homes. With changing rates and TOU billing, everyone is paying hundreds of dollars per month for electricity (between billed power and leasing costs). Wasting --because it would be wasting-- the energy they produce to heat water would cause every single one of these homes to go back to bills they were getting in the pre-solar era.

Electric water heaters run somewhere between 3KW and 5KW...which is crazy. In a place like SoCal, in the summer, your air conditioning system is going to consume that much power. The monumental increase in energy usage cannot be understated.

I have THERMAL hot water heating, similar to this:

https://www.stiebel-eltron-usa.com/products/solar-thermal-ho...

Just two to four panels are enough for most homes. Instead of burning gas or electricity to heat water, you run a little circulation pump and get water hotter than you can handle, by far. This is supplemented with gas to keep the desired temperature when the sun isn't up. I've been using these systems for well over 30 years, they work well and they are the smart way to make hot water from the sun. My 13 kW solar array isn't being used to inefficiently turn photons into electrons to then burn the energy making water hot.

This is what I thought originally, too, because it's just common sense, and it was true 30 years ago. But that common sense turns out to be wrong now, as you'll see if you do the math.

The manufacturer-suggested retail price of the Stiebel Eltron SOLkit 2 you link is US$7870, according to https://www.stiebel-eltron-usa.com/sites/default/files/pdf/s.... This includes two SOL 27 Premium flat-plate solar thermal collector panels, about which that page says, "The net absorber surface of over 25 square feet results in a maximum output of 31,300 btu/day per panel (SRCC clear day rating)."

In modern units, that's 2.3m² (per panel) and 382 watts (per panel), so you're paying US$7870 for 764 watts (on a clear day). That's US$10.30 per average watt. We don't really care about peak power, since the system comes with thermal energy storage built in, but if we assume a capacity factor of 20% (which would be about right if it were fixed photovoltaic) then it's about US$2 per peak watt. (Incidentally, that's a very-well-designed panel, because, assuming the same 20% capacity factor, it's about 80% efficient!)

That's a very high price. The SEIA calculated a cost breakdown for US residential solar PV installations in early 02024 (https://www.seia.org/research-resources/solar-market-insight...), of which 20¢ per peak watt (Wp) was the PV module. The rest of the US$3.25/Wp price (even higher than Stiebel Eltron's!) was things like batteries, inverters, installation labor, etc. You don't need those for water heating; you only need low-voltage wiring, an electric heating element (a resistor) in the water tank, and some kind of safety thermal cutoff. So if all you're interested in is getting a solar water heater, you can almost certainly get it more cheaply by running wires to your roof, or to panels in your yard, instead of pipes.

20¢/Wp at a 20% capacity factor would give you a nice round US$1 per round-the-clock watt, so 764 round-the-clock watts would cost you US$764 of panels, as compared to Stiebel Eltron's US$7870 MSRP. (Which one were you saying was "the smart way to make hot water from the sun" again?)

But the situation actually favors solar PV much more strongly than that, for two reasons. First, PV modules are cheaper than that; the "mainstream" price on https://www.solarserver.de/photovoltaik-preis-pv-modul-preis... is now 0.115€/Wp (US$0.125/Wp) wholesale, though the US's anti-renewable-energy policies presumably make them a little less cheap than that where you live. Second, in most cases, even if a home PV system provides less power than you need on average, it still provides more power than you need at times. If you're choosing between turning some of the panels off in the daytime and heating up the hot-water heater, the latter sounds like a better choice. If you're just burning up surplus energy, instead of buying extra panels just for your hot water, it won't even cost you US$764.

But wait, you might ask, why not batteries? And batteries are certainly more flexible than a hot-water heater. If you use your excess solar power production to charge batteries, you can use the energy later to run your computer, cool your house, run a circular saw, heat your house, or take a hot shower. If you use it to heat up a hot-water heater, you can only use it to heat your house or take a hot shower.

But batteries have a countervailing disadvantage: they're expensive. If your hot-water tank is at 65° when incoming water is at 20°, and the tank is 300 liters like the one in the Stiebel Eltron system you linked, it's storing 56MJ of energy, or, in cursed folk units, 16kWh. Lead–acid or lithium-ion batteries generally cost in the range of US$50–150/kWh (US$15–40/MJ) so the same amount of energy storage in batteries would cost US$700–2400. The hot-water tank only costs about US$500, if you don't have it already.

There are cheaper solar hot-water systems than Stiebel Eltron's. Looking locally, this no-brand locally-made 300-liter one sold by "Energía al Sol" only costs about $2.1 million: https://articulo.mercadolibre.com.ar/MLA-1683162470-termotan...

That's about US$1600 at today's exchange rate, one fifth of the much more complex system you're talking about. Still more expensive than the PV option.

The solar-thermal option might still beat PV if you're limited on space, because, at around 80% efficiency, it requires about a fourth of the area as the equivalent mainstream 23%-efficient photovoltaic panels. Even garden-variety solar thermal collectors can often exceed 50%. They're just much more expensive than photovoltaic. I know that's crazy, but what can I say? We live in a crazy world.

As for your unfortunate neighbors, I suspect that the reason they are paying hundreds of dollars a month for under 6kW is that they installed their solar systems when prices were much higher than they are today, and that all their energy storage is in electrical batteries. Some thermal energy storage—whether in primitive "sensible heat storage" systems like an insulated tank full of hot water, or more advanced phase-change and TCES systems—would probably have gone a long way toward bringing those costs down. See https://news.ycombinator.com/item?id=43468177 for a recent comment where I did a brief sketch of an LCoE estimate.

Why are people even considering an electric heating element, when you can get at least 2-3 times the efficiency of a DHW heat pump that would probably cost you ~ $4000. In my experience, I have found that for PV panels it is often the roof area / orientation that limits the energy capacity that you can install. Installing a heat pump instead of resistive heater can effectively reduce this 2-3 times.

Yes, heating DHW with a heat pump is not that trivial. There could be problems when the tap water is hard (limescale problems in heat exchangers), you often need 2-3 times larger tank in order to cover the daily cycle, but still looks more efficient than a big battery and an electric heater.

PS: I've accumulated lots of knowledge on the topic. DM me if you are interested in exchanging on this.

What size of DHW heat pump costs you ≈$4000? Which currency are we talking about here?

If you aren't limited by roof and other outdoor area for PV panels, US$4000 buys you about 50000 watts of "low cost" solar panels at current wholesale prices: https://www.solarserver.de/photovoltaik-preis-pv-modul-preis...

At a nominal capacity factor of 15%, that works out to about 5000 liters per day of domestic hot water:

    ~ $ units -t '50000W 15%/(30K 1kcal/kg/K)' kg/day
    5162.5239

Even in countries like the US with aggressive anti-renewable-energy regulation, it's hard to see how the heat pump comes out cheaper.

USD 4000 will buy you something like 12 - 16Kw R32 heat pump. If you have enough roof area to install 50kW PVs then you must live in a mansion :). Another thing is that heat pump installations are usually dual purpose (space heating/cooling and DHW).

Thanks! That's about US$0.20-US$0.40 per watt, which is probably cheap enough to compete with overprovisioning solar panels. What's the usual duty cycle for such a heat pump? Can you buy smaller ones? 12kW seems like it could provide 8000 liters of hot water per day, which seems like a lot even for a mansion. Maybe a public bathhouse.

It is certainly true that energy-intensive buildings cannot be self-sufficient on solar, but perhaps you can put the solar panels near your house instead of on it.

You can buy smaller ones. Domestic heat pumps usually start around 6-8 kW for single phase ones and go up to ~20kw for 3-phase units. Keep in mind that these values are the peak power of the heat pump, which you would rarely use. Modern units have inverter motor driven compressors, which can modulate their power output in the range 25%-100%. 100% is not a happy place for the heat pump if it is cold (and humid) outside, because it will quickly accumulate ice on the outdoor unit and start doing many defrost cycles per hour, which lowers the COP (efficiency).

With respect to the duty cycle, obviously if you have solar power, you would prefer to use it predominantly and only add up some extra power from the grid when needed. This is the essence of the sizing problem, because that leads you to 2-3x power overprovisioning and the need for heat/cold storage. Heat storage can be two types - DHW and space heating. Space heating is the easiest to estimate. You need to know your house's heat loss (either by specification or just figure it out empirically if you have already lived in it). DHW storage is more difficult to estimate, because it depends on the usage (e.g. how many showers per day). Cold storage is the most problematic, because the fluid needs to be at least 16C or lower to do useful cooling work, however you cannot go much lower than 7C unless you are using propylene glycol (expensive) and even then your indoor units may start to freeze (I am not even mentioning indoor humidity management and dew points).

Lately, the industry has been exploring PCMs (phase change materials). The idea is to store heat/cold not as sensible heat, but as latent heat of the phase change. In practice the substances used are either salts (efficient, but corrosive to the storage tank) or paraffins (more expensive, less efficient, but still viable). These come rated at a specific temperature, but usually have some hysteresis/drift and other issues. I guess you are now feeling a bit frustrated from the engineering complexity :). If batteries were cheap, long lasting and environmentally friendly, this complexity would not be needed. However, I really doubt it that in the foreseeable future batteries will beat heat storage. Given that most of our domestic energy use is space heating/cooling and DHW, I think that PCMs may actually have some moat. There are already offerings on the market, but IMHO they are still not very compelling. What I see lacking is some integrated offering, that would take into account the PV schedule and also grid prices. One a side not, batteries still have an advantage if you can sell back to the grid at a high premium or if you need to e.g. charge your car in the night. So these technologies may be complementary, rather than competitive.

A very big factor is climate. Just to give you an example, I live in the mountain with a colder climate. Cold water from the faucet is around 10C. I rarely need cooling if at all, but I need space heating around 8-9 months during the year. Just 300 km south and by the sea (Greece), cold water from the faucet is around 20-25C, you need 4-5 months of cooling and only ~4 months of heating. Some countries, such as UK have very moderate climate without extremes and things are more predictable. Where I live, we get -15C in the winter and 38C in the summer.

Thank you!

It sounds like you might be interested in my notes and calculations on thermal energy storage in phase change materials, some of which are listed at https://dercuano.github.io/topics/phase-change-materials.htm.... But I think TCES systems are likely to be more significant because of their technical advantages, among other things for managing indoor humidity and possibly even for seasonal thermal stores; some of my notes on the topic are at https://derctuo.github.io/notes/desiccant-climate-control.ht... and https://dernocua.github.io/notes/shower-heating-tces.html. Various kinds of thermal energy storage do seem to beat batteries on cost by around three orders of magnitude; some of my relevant notes are listed at https://derctuo.github.io/topics/thermal-storage.html. I agree with you that there is no real prospect of batteries catching up with thermal energy storage in the foreseeable future.

With respect to the particular problem you mention with needing expensive propylene glycol in your heat transfer fluid to keep it from freezing, ice rinks commonly use brine systems instead, despite the corrosion problems you mention. Brines are very cheap, some like dipotassium phosphate are minimally corrosive, and the commonly used ones are pretty nontoxic.

Wow! Your notes look like a treasure trove on the topic(s)!. I will definitely read them. Ironically, my heat pump just failed yesterday and now I am going through the service manual, so the resistance heater proponents may have some merit :)

Hopefully they're correct!

Just FYI, it turned out to be a bad connection between the controler PCB and the NTC temperature sensor that measures the condensation temperature at the plate heat exchanger.

So it was easy to fix? What a relief!

Heat pumps come with a lot of restrictions. What about constant noise? Plus stating that they are cheap ain't correct. Our housing unit in Switzerland recently needed to replace older oil heater and one of the options was heat pump... which was by far the worst choice based on various criteria and we at the end voted for the oil again.

How much was the cost, for how much heating capacity?

Sorry don't remember exactly, it was for 17 rather large apartments/semi houses (120-190m2), IIRC to the tune of 200k. Heat pumps would also require additional space to be put in, something we didn't have easily (not without some remodeling of whole area). They would be in the face of everybody's windows, another drawback combined with noise that was unavoidable as per proposition from vendor.

Another issue was that they were not available for a long time (around 6 months delivery time with no guarantee), something not relevant here but it also affected decision of owners.

I appreciate the information!

Thanks for the info! Now it is much easier to understand your concerns. It is a rather big installation that you have here, in the range around 100kW (if both space heating and DHW are considered). Such systems (aka chillers) are usually installed away from buildings or on the rooftop if local regulations allow it.

Noise could be a problem, but it is often the result of a bad installation. I'd be curious how much was the quote for the heat pump vs the oil heater.

How about lifetime costs? A resistive water heater is going to last longer and you can get non-metallic water heaters for extremely long life.

If you don't have net metering (or just a terrible power purchase rate), why not just sink that extra solar energy into a water heater?

That is a good question. The usable life of a combined heat pump (space heating/cooling + DHW) is somewhere between 10-15 years. For the ones, dedicated to DHW, I cannot really tell, but I would expect it to be longer, because they are usually less heavily loaded. Then the answer of your question will depend on the price of installation (e.g. heat pump vs 3 x extra PVs), local climate (affects efficiency) and price of electricity. Heat pumps don't work well in very cold climates, but for most US/EU cities they will work fine. For very hot climates it may be better to use solar water heaters, although for commercial installations there is the option to use the exhaust heat from cooling to heat DHW (it is essentially free energy).

They also use the duck curve to represent energy demand, when it only reflects grid demand minus utility solar and wind.

There's nothing particularly confusing about the duck curve but it must be the most misunderstood (and/or misrepresented) graph in all energy.

The company I work for (as a data engineer) does utility scale solar + battery installation and site management. We recently finished a large scale installation just outside of Las Vegas (by some measures the largest in the US). It was backed by a PE firm. Costs are getting so low, the tech so predictable, and with battery warranties around 20 years the PE firm is able to get pretty high return with a fairly low risk. They enter into a "power purchase agreement" with the utility so they know how much they will be able to sell the power for, and as long as we collect data on the batteries they will be able to be warrantied if there is an issue (but there rarely are issues).

The batteries are by far the most expensive portion of the setup. The solar by comparison is dirt cheap. We have single axis tracking like mentioned in the article. Every day we fully charge the batteries, and discharge them in the evening.

> I work for (as a data engineer) does utility scale solar + battery installation and site management.

Did you build your own excel/python nightmare or is everyone using 3rd party management software for this?

> as long as we collect data on the batteries they will be able to be warrantied

Can you share some of the data? Beyond power in/out, do you monitor humidity, vibrations, temperature ?

Our data pipeline looks like this:

hardware/PLC --modbus--> kepware --mqtt--> mosquito broker --mqtt--> mqtt2prometheustool --http--> Victoria Metrics

The mqtt2prometheustool is something we developed in house. I am looking at removing one or more of the above steps and using telegraf instead, as it can ingest OPCUA or modbus data directly.

We use excel files just as the output of our reporting tools. For analysis it's the standard python data science stack of pands/numpy/scipy. Most people work in Jupyter notebooks, and their tools are eventually moved to services in our k8s cluster.

Temp and voltage are the main "cell level" datapoints we collect. I don't think we have any vibration sensors at site now.

I'm working in the IIoT domain too. Your workflow is interesting towards the end. Any particular reason, why you don't write it to some db like Timescale or Influx at the end without any prometheus conversion?

Victoria Metrics is a Prometheus compatible time series database and was being used before I joined the company. I haven’t had any issues with it so I didn’t see a reason to pull it from our stack. Are you saying Timescale or Influx can natively ingest MQTT messages?

Similar to your mqtt converter you can make them ingest via Kafka or some other adapter in between. EMQX broker can directly write into TSDB but did not research into others whether they can or not.

Is there any pros to use PostgreSQL for metrics in 2025?

Not the OTEL "telemetry" but sensors sending measurements from the field "telemetry". IT tech is, as usual, stealing perfectly defined engineering words and making them something else.

TimescaleDB is perfect if you also have relational data that you need to join with field data to the point that there no pros of using anything else for this use case, say you have 100000+ sensors and you need to group them by the customer site relations while aggregating per day statistics.

Does this include thermals on batteries? And how much power is spent on keeping them at the optimals? What about SoC/SoD figures?

Because without that the 20 year promise is bullshit.

I can sort of name ballpark figures for the above, the thing I can't get is how this can even approach profitable w/o hype and subsidies.

> Does this include thermals on batteries?

Yes, not just batteries, but we collect cell level temperature for all cells in all batteries.

> And how much power is spent on keeping them at the optimals?

We run an AC unit on every container to keep them cool. (Its in the NV desert so never any need for a heater)

> What about SoC/SoD figures?

We do compute estimates of SoC but as you probably know charge state isn't always easy to estimate. All we really know is voltage, c rate and time.

> I can sort of name ballpark figures for the above, the thing I can't get is how this can even approach profitable w/o hype and subsidies.

There is certainly risk involved with any investment. But when you are buying batteries at the scale we do the price is probably much lower than you are thinking. And if we do properly gather all the warranty data then the risk of loss on battery failure is minimized.

well.. okay.

NV looks like similar enough to mid-to-southern-africa where we did stuff.

an AC unit (6KW? 24KW?) (per what, TEU or double-TEU) doesn't look like something sustainable. but we had much less dense installs, so I'm not really ready to argue that

SoC vs thermals vs load/charge profile is very not-a-single-number, but when the battery banks suddenly start demanding replacement (+ african logistics ) one develops models for the monitoring dashboards quite fast indeed.

I still believe that 20 yr warranty is bullshit on any serious load cycle. But if the manufacturers are willing to swap them, then no problem of course.

As someone working in the IoT space - why pay for kepware for something that can be done in a few weeks by a developer? Telegraf or even a bit of programming will save a lot of pain

I am actively exploring replacing kepware with telegraf. It seems very promising. Kepware was purchased and deployed before I joined the company. I think it's the defacto standard in the controls world and they never really considered anything else.

Do you have experience with modbus in telegraf? If so I'd love to chat for a bit to learn what you've learned.

It's just making mqtt messages from modbus is such a simple task that you can just write the software yourself. There are many intricate stuff in modbus that maybe does not translate too well for generic translators and where you want to have full control. For example messages over multiple registers, breaking interfaces between vender versions and all that legacy stuff.

Telegraf is also nice (but only used it for mqtt topics) but the same applies here. The functionality is fairly simple. In telegraf depending on your data your .conf file gets fairly large and has to be maintained. If you have your data model already in code it's fairly easy to just write it yourself and gain the simplicity of just using the classes you have anyway.

In my current stack the data ingestion both the initial data->mqtt and mqtt-> database/cloud is just small programs that share their internal data objects. It's very easy to maintain for a small team imo.

how do you like it? I have a 20 year career in large scale consumer app/web/b2c tech, but i've always wanted to work in renewables. Is it easy enough to break into? Is there many non-hardware roles (i have no hardware skills)? any advice / vibes?

It's a great job. I joined with no prior experience in the field, and none of the positions on my team require hardware experience.

Personal energy abundance and off grid independence is the good life and it means using all electric appliances and vehicles, heat pump and hot tub, powered by nonpolluting energy generation.

As the article alluded to, scale is important for this to work (although I get by fine using only thirty 400 watt panels (12kw) and this covers less than 30% of my roof).

As a remote worker, not commuting daily large distances is key to this system working. If I had to commute 60 miles every day I would need additional 10-15 panels to power the Ford Lightning EV truck, and if I was charging at night I would need six additional 100A 48v batteries.

If you had to commute daily, wouldn't you buy a smaller commuter EV? Something from Hyunda or Nissan? The depreciation on that Lighting will be rough if you had to drive it 80 miles/day.

Yes, utility vehicles are by definition not ideal for personal commuting.

In Czech republic - europe - they made law that says anyone can built up to 100 kWp solar array, without any building permits, township meetings, HOA nonsense etc. You want it, you can build it.

Best way to be independent of your neighbors polluting your air with their wood burning furnace is show them PV works, and is cheap.

Yes, this wasn't economically feasible 10 years ago due to the rapid improvement in batteries, inverters, heat pumps for air conditioning and water heating, etc. I've been living off grid over 20 years but its only recently that its at least as good as a connected 200 amp grid power service with ample 220v for residential needs.

The bit how about incredibly quickly PV has grown is a figurative slap in the face to Vaclav Smil. He had just ten years earlier said PV wasn't going to grow quickly because historically energy replacements took a long time.

https://vaclavsmil.com/wp-content/uploads/2024/10/scientific...

This retrospective on Smil's predictions four years ago is notable:

https://www.quora.com/Is-Vaclav-Smil-right-in-his-criticisms...

"To get 1 PWh/year of electricity you need to install about 450 GW worth of solar panels. You need dozens of years to acomplish such task. Reality check: 3 years in current speed, in the future probably faster."

Indeed, as the thread top link shows in 2024 the world installed 595 GW of PV.

As John Kenneth Galbraith said, "If all else fails, immortality can always be assured by spectacular error."

What people tend to forget is, that coal, oil and gas are all restricted by mining or drilling as the old are consumed, and it gets harder to access new oil wells etc. For PV there is no such limit (only copper basically, but this is recyclable and aluminum can do many tasks.) For batteries, there is lithium (lifepo4) and even that is questionable (sodium batteries) and again there is the potential for recycling. Hence, I do not see anything stopping the exponential growth of PV and batteries.

You are right.

But one misconception I often read is that everyone focuses on batteries. It would make more sense in general to talk about energy storage instead of just batteries. Like Kinetic, chemical, thermal and so on.

Batteries cannot be solely responsible for back-up. You need different types of storage: short term, medium term and long term storage.

There are different concepts for each application. Batteries, compressed air storage, pumped storage, kinetic, thermal storage as well as power-to-X systems are able to absorb the increasing summer power and provide the energy again in the medium term or seasonally shifted.

https://doi.org/10.3929/ethz-b-000445597

There are only three energy storage forms that are relevant for the next decade. All the others looked promising, but the learning curve on batteries has rendered them irrelevant. Your link is from 2020, it is out of date.

The best energy storage form is "final form". Some energy products can be stored. For example if you are using the energy to create heat, you can store heat for use in the future. Heat storage sucks as a way to store energy destined for electricity, but is a great way to store energy destined for use as heat.

The utility of batteries for daily storage is obvious and well proven.

Thirdly, the best annual storage is pumped hydro. It's the cheapest and it can be used pretty much everywhere -- all you need is water at one end of an elevation change and a way to build storage at the other end.

All the other forms that you'd think would fit in between the two are being quickly subsumed by the rapid price drops in battery pricing. The cutover points are rapidly shifting -- batteries are now cheapest for biweekly-ish.

And the primary sources are getting so cheap that overbuilding is an alternative to storage. Rather than storing for the reduced amount of daylight in the winter, just overbuild. More overbuilding and a few days of storage will let you handle a stretch of cloudy, windless days in January. No annual storage required.

Don’t get me wrong—I’d be all for batteries ruling the world if they were both affordable and technically advanced enough to meet various demands. That means they shouldn’t degrade too quickly, for example, when capturing and releasing wind energy in milliseconds. Or they shouldn’t lose too much energy over time due to self-discharge. Or they should be able to supply large amounts of energy instantly. Overbuilding is also a valid approach, especially in connection with a smart grid spanning multiple countries. All of that is fine.

However, the point of the study is different, and that makes it still relevant today: The barrier to expanding energy storage isn’t a technical one—it’s a political one. The study also shows that there is a great deal of variability, and the often-used argument that there’s not enough lithium or rare earth elements doesn’t hold up. More recent studies validate different storage technologies depending on their specific use case, showing that they can complement batteries in a meaningful way—also from a financial perspective.

Another perspective is that we still have a long way to go before full electrification. Right now, batteries are used in suitable scenarios, but many other areas haven’t been electrified or optimized at all. Other storage technologies might still become relevant. Building a house around a 20,000-liter tank to store energy for heating in Alaska over six months might already be financially and technically viable. But whether the logistical challenges of such solutions will ever make them truly feasible—that’s something I neither want nor can predict.

> Thirdly, the best annual storage is pumped hydro.

I strongly dispute this. E-fuels like hydrogen would be much superior to PHES for annual storage.

https://x.com/iain_staffell/status/1722544993179504965

Only if we have more than enough renewable energy to spend making hydrogen. Hydrogen storage has a round-trip efficiency of 40%-50%, leading to significant energy losses. Partly by: Electrolysis requires 50-55 kWh to produce 1 kg of hydrogen, which only contains about 40 kWh, resulting in a 20%-30% energy loss upfront. It’s low energy density requires high-pressure or cryogenic storage, increasing costs and energy use, while leakage further reduces efficiency. Limited pipelines and refueling stations make hydrogen adoption costly and complex. Highly flammable hydrogen demands a lot of safety measures adding even more cost and complexity.

At the current exponential growth rate, PV will reach the point of supplying the entire world primary energy demand in a decade and a half.

Yes, hydrogen has low round trip efficiency. But it comes out cheaper than PHES. The "cost of inefficiency" is proportional to the number of charge/discharge cycles. For annual storage, efficiency is 365x less impactful than it is for diurnal storage. What matters for annual storage is capex of storage capacity.

> What matters for annual storage is capex of storage capacity.

Which is exactly why PHES wins the cost comparison for annual storage. Open air water storage is ridiculously cheap compared to hydrogen storage.

I dispute this as well. From what I see, the very best case per kWh cost of just the reservoirs and waterways for PHES is about $10/kWh. Hydrogen stored as compressed gas in solution mined salt caverns would be an order of magnitude cheaper. For storage of liquid e-fuels in tanks, tank capex would be another order of magnitude cheaper still. This assessment is consistent with the link I posted earlier.

If you want something that may compete with hydrogen for annual storage, consider bulk thermal storage (using artificially injected heat, not naturally occurring heat). The thermal time constant of a very large object increases quadratically with radius, if everything is scaled proportionally, and can easily reach many years. This is why geothermal works at all -- there's plenty of heat stored in the near crust ready to be mined.

You're comparing using an existing reservoir for hydrogen to building a new reservoir for PHES. There similarly exist dry lake beds that could be used for water storage. But generally they're not in suitable locations, which is the same problem that salt mines will have.

You're also comparing hypothetical costs to historical costs. Hypothetical costs put out by industry are usually out by about an order of magnitude.

There's a reason that PHES is the only one with historical costs.

No, I was describing the cost of constructing a new hydrogen storage reservoir in a salt formation by solution mining. Of course existing natural gas storage caverns could be repurposed; that would be even cheaper.

These are not hypothetical costs. Construction of these caverns is state of the practice for natural gas storage. Vast volumes of gas are stored in these things, allowing steady production of natural gas and constrained pipeline capacity to serve seasonally unsteady consumption patterns.

The reason PHES is the only one with historical costs is that, historically, PHES has been used for diurnal storage, from the days when baseload plants were cheaper. There was never a market for long term storage via hydrogen (although some hydrogen storage has been constructed and used to help steady the hydrogen input to ammonia plants); why bother for the grid when just varying the use of fossil fuels would serve that function just as well?

I'd be curious if either of you would have a link to actual projects (projected or realised) with their respective costs?

Here's a presentation of a comprehensive NREL study from 2018, but I don't know the source of the numbers. It finds hydrogen and flexible generation (that is, natural gas turbines) are best for long duration storage. Notice the slides on page 13. PHS is way out of the running for the storage case being discussed here; it's not close.

https://www.nrel.gov/docs/fy21osti/77833.pdf

Thanks. I mean it’s from 2018 and that is ancient history as far as storage costs are concerned. But yeah those $/kWh numbers for PHS are orders of magnitude higher. Thanks for the link, I’ll try to find the final study tomorrow

> Thirdly, the best annual storage is pumped hydro. It's the cheapest and it can be used pretty much everywhere -- all you need is water at one end of an elevation change and a way to build storage at the other end.

Pumped hydro is primarily used for short term storage. The vast majority of pumped hydro installations around the world operate on an intra-day cycle.

For storage systems generally (not just electricity), profitability is a linear function of capacity, the possible price arbitrage AND how frequently you charge and discharge. Nobody is going to build a pumped hydro storage facility with the intension of operating a single charge/discharge cycle per year.

Nor are pumped hydro facilities cheap to build and certainly cannot be deployed everywhere as they require particular geographic and geologic conditions and mostly locations suitable for pumped hydro are few and far between and those locations that are suitable are generally far away from population centers where the demand for electricity is.

Batteries are often cheaper than pumped hydro, they can be located near demand, they scaled down as well as up and can be distributed around the grid to provide "virtual transmission". They are quick to deploy and require little maintenance or staffing.

The solution for "long term" storage will be massive over-provision of wind and solar and more grid interconnections. Batteries will take care of everything else.

I think this is going to turn out like the exotic panel chemistries: batteries are simple and have powerful continual improvement in performance and price, while the others turn out to be more complicated. In particular solid state wins over mechanical anything almost every time.

I am on you side (but not all are more complicated and there are mechanical variations that are better than batteries for some scenarios) but the takeaway of that study is described here: https://news.ycombinator.com/item?id=43425560

PV doesn't require much copper, either. Maybe for front contact wires, if silver gets too expensive? But if it can afford to use silver now, copper won't be a huge ask (basically just need to deposit a barrier layer to keep the copper from reacting with the silicon.)

The cables connecting PV to the grid, as well as the grid itself, can all use aluminum conductors. Even large transformers can be designed with aluminum if copper gets too expensive.

The IPCC & IEA grossly underestimates PV (and Wind) by any metric for years. Many scenarios assumed costs for 2050 that are already outdated today.

In the same time they overestimate Nuclear Energy and carbon capture by any metric (debatable). It’s getting so bad that there are numerous studies about that problem.

https://www.carbonbrief.org/guest-post-why-solar-keeps-being...

https://www.pv-magazine.com/2021/03/31/solar-still-largely-u...

https://www.theenergymix.com/leading-climate-models-underest...

https://climatenexus.org/climate-change-news/iea-historicall...

I think a lot this comes down to huge cultural biases. And the two cultures are "hard energy" and "soft energy" folks. Coal, gas, fission, fusion, etc. are all hard energy. Coupled GDP and energy consumption was a core assumption. Renewables, energy efficiency, technological advancement via learning curves all fall under "soft energy".

Most of the energy industry was hard energy because that's what paid everyone's bills. Any estimates that did not cater at least a bit to those biases would just be completely ignored.

But there's another effect too: solar just completely outperforms even the most optimistic assessments. There's one famous solar financial analyst, whose name I'm blanking on, who continues to underestimate even though she knows the effect.

It was also underestimation of China. Outright chauvinism there.

iCal them „simple“ and „complex“ power. For someone who isn’t truly informed, a „Simple Energy“ solution seems much simpler than one based on renewable energy. With „simple“ power, solving climate change appears straightforward: just build more nuclear plants, which conveniently replace coal and gas on a 1:1 basis since they are baseload power generators.

Renewable energy, on the other hand, is (for now, the transition time) complex. It requires a better, smarter, and much larger interconnected grid, as well as intelligent management of supply, demand, and storage. It means considering and understanding multiple aspects at once. This complexity often leads people who are convinced that more simple power is the answer to dismiss the idea of renewables too quickly—because nuclear seems so much simpler.

I understand the appeal of simple energy. The sad part is that many people likely believe this is the scientifically correct position. And they are often so convinced that, even when presented with current studies and reasonable arguments against new nuclear plants, they quickly assume that the other person is just an irrational, biased anti-nuclear activist. After all, the simplest solution must also be the right one, right?

Being informed in this context doesn’t just mean knowing the pros and cons of nuclear, wind, or solar power. It requires a deep understanding of what is technically and financially feasible today—including energy forms, grid transformation, storage solutions (not just lithium-ion batteries), follow-up costs, sustainability (mining, waste disposal), as well as political, economic, military, and social implications. And how all of these factors interact.

But none of that is necessary if you just want to build more simple power plants.

The transition to 100% renewable energy is as complex as the development of the internet. If we were still relying on letters, telephones, fax machines, newspapers, radio, and TV, the idea of transitioning to a globally available, instant multimedia internet would have seemed just as utopian and impossible.

Nuclear can’t (cheaply) replace gas.

Indeed. Particularly in the US, fracking was an extinction-level event for new nuclear construction.

https://pubs.aip.org/physicstoday/article/71/12/26/904707/US...

“The cost of new nuclear is prohibitive for us to be investing in,” says Crane. Exelon considered building two new reactors in Texas in 2005, he says, when gas prices were $8/MMBtu and were projected to rise to $13/MMBtu. At that price, the project would have been viable with a CO2 tax of $25 per ton. “We’re sitting here trading 2019 gas at $2.90 per MMBtu,” he says; for new nuclear power to be competitive at that price, a CO2 tax “would be $300–$400.” Exelon currently is placing its bets instead on advances in energy storage and carbon sequestration technologies.

Jenny Chase perhaps:

> On Friday my colleagues suggested I get a tattoo reading "COWARDS", to save me time saying it in solar forecast calibration meetings.

That's her! She's done really amazing work for BloombergNEF.

There is a lot of stuff that people said about this solar that got overtaken by reality. And some of those people were proponents even.

People have underestimated economics, learning effects, and the effects of increased scale. Mostly the exponentials were actually pretty clear to some investors as early as 15 years ago. And the success those investors have had, has driven more investment.

The thing with exponential trends is that doubling a little bit results in a little bit more. It doesn't add up to something people notice until suddenly it jumps from fractions of a percent, to full percents, to double digit percentages in the space of a few years. That threshold got crossed a few years ago and people started to notice. And that's now leading to further price drops and more adoption. Of course, it's not a real exponential but an s-curve. But until the curve flattens, you won't be able to tell the difference.

Back of the envelope calculations can be misleading because they tend over simplify and make silly assumptions. Like assuming we are going to move 100% of energy to solar all at once. In reality, what we're doing is a decades long transition where most of the decision making is cost driven and the energy supply is coming from mixed sources.

We don't have just solar. We have existing nuclear. Existing deployments of coal and gas, which like them or not are not going to disappear overnight. And a lot of onshore and offshore wind. And a rapidly growing amount of batteries and cables which give us the ability to time shift supply and demand and move energy around over large distances.

The world's electricity consumption is about 30 PWh per year and will probably grow to 35 or 40 soonish. Most of that growth (>90%) will be powered by renewables. It's outgrowing everything else by a large margin. And because they are cheaper, there is also pressure to replace existing generation with renewables. That basically happens based on cost and age of plants.

This is another effect that people keep underestimating. The reason coal generation is rapidly disappearing from many markets (and is completely gone in some of them) is that replacing them with cheap renewables is cheaper than continuing to operate them.

That same effect is going to affect gas generation. Anyone building gas plants with the expectation that they'll have a 60 year life span is dreaming at this point. These investments should be considered as under water at this point. By the 2050s, most currently new gas plants will have probably have been mothballed (maybe kept around as rarely used peaker plants) or demolished. They are simply too expensive to operate relative to renewables. Some places keep gas prices low via subsidies (the US for example). But even there gas plants are going to face a reality check. And for a lot of countries, gas imports are a drag on their economy. Germany is a good example.

Worth observing what investors do here. They tend to have long term outlooks.

Smil was just bullshitting though, really poor quality arguments made for rhetorical effect with a side helping of smug fake reasonableness.

He's a cranky old academic propelled to fame because he said what the establishment wanted to hear like an energy Jordan Peterson.

One thing I haven't seen much coverage on is how to tap into the giant batteries we're driving around in our electric vehicles. These are much bigger than what's currently being deployed in houses.

The V2H standards are just now coming online: https://electrek.co/2025/02/21/nema-bidirectional-ev-chargin...

There might not even be any need for V2G or V2H.

Just charging your car when the demand is low is probably enough to drastically reduce the overall cost of the system. And this has basically no impact on the battery lifespan.

A trial in the UK resulted in customers earning up to £725/year [1]. With increased renewables on the grid leading to increased flutucations in the wholesale price of electricity, providing V2G/V2H will further reduce a customer's electricity bill on top of the savings offered by smart charging eg. Charge Anytime Tariff is 7p per kWh for EV charging [2] vs 27p kWh average Apr - Jun 2025 [3].

1. https://www.kaluza.com/case-studies/case-study-kaluza-enable...

2. https://www.ovoenergy.com/electric-cars/charge-anytime

3. https://www.nimblefins.co.uk/average-cost-electricity-kwh-uk

High demand is not the sole reason for outages.

V2L is one of the reasons I bought the car I did - instead of getting battery backup for the random outages that PG&E gifts us (literally power drops likely to happen whenever we gust over 25mph), I installed a 12 circuit transfer switch and my 75kWh battery in the car can provide reasonable backup without running cables throughout the house (reasonable = 1.9kW max so no hair dryers or running toaster oven + microwave at the same time).

Newer vehicles (like 2025 Ioniq5) can do 12kW throughput (and many trucks can do 9+ kW already).

Once V2H standards are confirmed and deployed I would be able to integrate the Car batteries with home batteries and solar.

A Generlink would have simplied your transfer switch rewiring. Just connect the external 240V supply (be it your vehicle, batteries, or a fossil fuel powered generator), and the Generlink shuts down the grid connection and delivers to your regular main service panel. You might need to turn some circuits off when using it, but which circuits and when remains flexible and context dependent.

Arbitrary vehicle to home/home battery/grid connection is indeed coming in very short order.

https://enphase.com/ev-chargers/bidirectional

There are other products already available to do it (DCBel), and it can be hacked of course, but at the current moment everything comes with substantial corner case blind spots, mostly related to grid-forming/following switching and to the resilience of the power electronics.

The author misses a perhaps unintuitive point: the cost of storage depends also on the cost of energy. By the time you've overbuilt 2x, a full extra 100% of your demand is sitting around literally free at odd hours.

Traditionally, moving energy around means batteries, and yes maybe your battery costs more than just generating new electricity from a less efficient new solar panel at odd hours. But batteries are optimized for energy being expensive, where losses are wasteful.

Consider this really simple, dirt cheap alternative: plug your free energy into a pool of water and collect the hydrogen from it. Burn the hydrogen later, and point the light at your idle solar panels. It's hellishly inefficient, but I repeat: the energy is free. You are only minimizing capital costs, at least until other people catch up and start shifting load some other way.

The sane point on this curve probably looks something along the lines of a mix of batteries and synthetic fuels powering existing fossil fuel plants. The nice thing about going all the way to synthetic fuels and not hydrogen is that long term storage becomes trivially cheap, so it starts offsetting your winter load as well.

It's a very long stretch from "generate hydrogen" to "powering existing fossil fuel plants".

The most unlikely part is not even creating renewable fuels (that is a stretch already), but the idea that those fuels are going to be compatible with existing plants and infrastructure. It's not impossible, but it would probably be the least economical way to go about it. I recommend reading some industrydecarbonization.com articles for going a bit more in-depth about the why.

Hydrogen-ready power plants are already being built, so that’s actually the least difficult part of the problem. The current bottleneck is actually producing the hydrogen, and next will be building the transport infrastructure.

https://www.latitudemedia.com/news/hydrogen-ready-power-plan...

> It's hellishly inefficient, but I repeat: the energy is free.

Can you give pointers about who gives away hydrogen generation systems for free?

Because the cost of energy usually factors in the cost of amortizing equipment required to produce and distribute it.

> The nice thing about going all the way to synthetic fuels and not hydrogen is that long term storage becomes trivially cheap

Once you've financed all of the horribly expensive capital expenditure, and provided you disregard that operating costs actually require paying people to monitor, repair and operate that infrastructure, the rest is basically free.

> Can you give pointers about who gives away hydrogen generation systems for free?

If you don't care about efficiency (because the electricity is free), a 9 year old can make hydrogen generators out of old pencils and jam jars.

Citation: me, I did that.

I can also make some methane depending on what's on the lunch menu, but that doesn't mean cheap renewable natural gas is a solved problem.

Do you really not understand the point I'm making here?

The technical skills needed to make a device that turns water and electricity into hydrogen are so minimal that they can be performed by someone too young for you to be allowed to employ them.

When you don't care about efficiency, hydrogen is trivial.

The limiting factor is how much electricity you can shove through the water, not human effort.

To be fair the problem with hydrogen isn't the production (that is ~free, once you have free energy at least some amount of time) but it's storage and then usage. Storage is a fundamental physics problem. Usage is something where low efficiency may or may not be a problem, depending on the over provisioning that we applied at the generation and storage stages.

Production is trivial, but storage and transport really isn't: https://climate.mit.edu/ask-mit/can-we-use-pipelines-and-pow...

first of all, youre spreading misinformation.

storage is CHEAP AF. BUT not kind every misinfo guru from youtube tells you about.

this is cheaper - https://ethz.ch/en/news-and-events/eth-news/news/2024/08/iro...

also https://www.rotterdaminnovationcity.com/co2-neutral-living-i...

AND most importantly, WHY do you need to transport hydrogen ? You do not need. think about it. you get electricity to your plant, make hydrogen on site, store hydrogen on site for almost nothing. why do you need to transport anything ? you do not.

Oh wow. I read about that project some time last year. But I didn't do the calculations back then. If I did my math correctly then this H2-in-iron comes out to 2EUR/kWh_el. I wonder what the catch is

how much of kWh is your house needing for heating, hot water and how much for tv,notebook etc ? calculate what percentage / ratio your tv is. caring about electricity is nonsense, care about 95% of your household consumption. and yes your cooling bill is 0 dollars because you have PV on roof.

Interesting references, thanks. But both seem to be at the research and feasibility stage. From the ETH group's web page: (https://fml.ethz.ch/research/ses.html)

> To demonstrate the technical feasability of this process, we buildt a 10MWh pilot plant at ETH Hönggerberg. The first charing cycle, using hydrogen to reduce iron oxide to iron, was successfully completed over a time span of 4 months. The discharging cycle is currently ongoing.

So either they haven't managed to do a full cycle yet, or they are not updating their research page. It sounds like this should work, so I'm tentatively optimistic. But this looks like a technology you'd have to bet on, not yet a certain path to a commercial seasonal battery just waiting for mass deployment.

ETH zurich is not inventing new reaction, google "reducing iron oxide by hydrogen". it is well known and already used technology. nothing new about this reaction, way they use it is new. all your concerns are answered in next article :

another university - university of eindhoven is using same reaction but totally different way - they just burn iron oxide in air ... https://www.youtube.com/watch?v=Qm0sIN-KhUo same thing same people - https://newatlas.com/energy/bavarian-brewery-carbon-free-ren... it is just totally primitive way and THAT is actually benefit. because it can be deployed fast and wide.

people seems to not understand how big of a energy demand is for hot water. and this can make hot water from renewable sources a reality. in most houses hot water need is roughly 50% of energy need. in low carbon houses / LEED / BREAM /Passive house / or what EU regulations already require, is energy need for hot water multiples of all other energy needs of household, because with better houses, youre lowering energy required for heating, cooling, but hot water stays same amount but bugger percentage.

planetary - with better buildings, we can lower house heating by 70-80 % no price problem, hassle free, that means we need less electricity generation for houses. + adding hydrogen generation / iron oxide reduction into mix we can just burn it and make hot water and electricity in winter from spring, summer, autumn sun.... in spring,summer,autumn you use PV for hot water + hydrogen to store for winter. booom 95+% of household consumption is gone from grid. household energy need is how much of total planetary energy need ? 20 or 40 % ? no one cares.

you do not need to transport anything if you think about this as for seasonal storage. but you can transport raw iron like university of eidhoven is proposing if your mission is to provide heat but reduce iron oxide close to renewable generation. your tansporting iron (Fe), NOT iron oxide(FeO,FeO2,FeO3)...

> youre spreading misinformation

> every misinfo guru from youtube tells you

Please don't cross into personal attack in HN comments and please edit out swipes and name-calling. Your post would be fine without those bits.

If you'd please review https://news.ycombinator.com/newsguidelines.html and stick to the rules when posting here, we'd appreciate it.

youtuber - it is not personal attack it is commentary on state of world, im saying to him that he should recalculate, review information he gets from youtubers.

every youtuber who says hydrogen storage, transport is not cheap is spreading misinformation. or if youre angry because you know youtubers are saying it because it as a desinformation, then feel free to chime in about it. or report those youtubers directly inside of a youtube platform.

not personal attack, i am not cute, i am not smart. they are saying nonsense. i provided links showing price for transport, storage is orders of magnitude lower than what any of top 50 science youtubers are saying it is.

you can correct previous statement by providing link for any video of any top 50 science youtuber providing correct numbers.

I meant "misinfo guru" in that case, especially because you directed that at the other person ("tells you").

You don't need to say things like "they are saying nonsense" - it's enough to provide correct information that addresses incorrect information.

but he will just go back to youtube. that is why i need to say youtube guru is wrong to make clear what exactly is harmful.

Storage matters for widespread direct-consumer use of hydrogen, but in the example I gave it's not a big deal: just put the electrolyzer next to the solar panels. You only need to store ~12h of hydrogen production, and burn it onsite.

A more realistic world won't be implementing the Dumbest Possible Refutation, and would overbuild solar less than this in the first place. In that case you do care a lot more about storage, and that's a large part of why I suggested ‘synthetic fuels powering existing fossil fuel plants’ would be a saner strategy. But what exactly that world looks like is in the details, and not critical to the broad point I was making.

> Do you really not understand the point I'm making here?

This is the sort of thing that the site guidelines ask you to edit out of your comments here (https://news.ycombinator.com/newsguidelines.html). Your post would be just fine without that bit.

Oops, noted.

Hydrogen generation systems exist on the same balance. When the input electricity is expensive, you want to build them to be more efficient, and that costs money, in catalysts and low-loss reaction chambers and such. If a huge amount of energy at peak times is free, then the optimal point is very different, and indeed if you try to minimize capital costs you end up needing something barely more sophisticated than a kettle. Kettles aren't particularly expensive to run!

While competition will quickly drive this towards a more even balance, as cheap storage displaces yet-more excess solar buildout, the point of the argument was just to show why naïvely extrapolating to extreme overproduction (>2x) is misleading.

Less than 1% of all the hydrogen produced worldwide is from "green" sources [1].

If your dirt cheap alternative is really so dirt cheap, why doesn't anybody do it?

[1]: https://www.iea.org/reports/global-hydrogen-review-2024/hydr...

We don't yet live in a world where electricity is reliably overproduced by 2x. Renewables are ~100% of the US's new electricity production, but still only a small fraction of its total electricity production.

Good longread.

What I'd like to have a better understanding of, and I'm hoping to crowdsource here, is exactly how the solar panel cost has come down so precipitously. Part of it is simply manufacture scaling - almost everything is much cheaper in large quantities. But part of it must be a thousand incremental tech advances. Things like the reduced kerf diamond wire saw.

Also of note: I think monocrystalline has won completely? People experimented with all sorts of alternate chemistries and technologies, like ion deposition and the extremely poisonous CIGS, but good old "Czochralski process + slice thinly" has won despite being energy intensive itself.

Perovskites remain an unknown quantity.

CdTe is still out there, from First Solar, but it's not much of the market (and has scalability problems due to the need for tellurium, even if the active layer is much thinner than in silicon cells.)

One little advance that swept the industry a couple of years ago was replacement of boron as a dopant by gallium. Boron doped silicon has light induced degradation, which was determined to cause a small loss in efficiency due to formation of boron trapping centers under prolonged light exposure. Gallium-doped silicon doesn't have this problem.

You're in luck! The author's earlier piece on the subject attempts to address that exact question. Learning curve effects and piggy backing off the computer chip industry are major factors if I recall, but I haven't reread the piece in a while.

https://www.construction-physics.com/p/how-did-solar-power-g...

My understanding is that China recognized the potential of solar power around 20 years ago and decided they wanted to be the world's manufacturing hub for solar panels. The government invested in R&D early, and today we are reaping the fruits of that investment.

The same thing is happening now with storage, but western governments are weary of losing that battle as well. To address this massive tariffs were put in place by the previous US administration, and are likely to be increased by the current administration. Hopefully this doesn't slow down the production of batteries, but instead just moves the production out of China and into other countries, but that remains to be seen.

Wary not weary

The US policy doesn't seem very smart.

invest in R&D -> reap fruit

tariff barriers -> inefficient industries

The current administration seems to be doubling down on that.

The article posted by wolfram74 is part one of two, covering solar PV history up through the early 1980s.

Here's part two of the series with more recent history: https://www.construction-physics.com/p/how-did-solar-power-g...

Even this fairly long two-part discussion misses some of the more important technical developments of the past 20 years.

Converting trichlorosilane to pure silicon via CVD growth in Siemens-type reactors is now much more energy efficient due to changes in rod geometry and heat trapping via reactor design. A significant minority of purified silicon is now manufactured via even more efficient fluidized bed reactors.

The solar industry is dominated by Czochralski process monocrystalline silicon, but it's now continuous Czochralski: multiple crystals grown from a single crucible, recharging the molten silicon over time; the traditional process used a crucible once and then discarded it.

The dominant silicon material has switched from boron doped p-type silicon to gallium doped p-type silicon (mentioned by pfdietz) to phosphorus doped n-type silicon (used by the currently dominant TOPCon cell technology as well as heterojunction (HJT) cells and most back contact cells).

Changes in wafering that you mentioned (like the reduced kerf diamond wire saw) have reduced silicon consumption per wafer and therefore per watt, even holding cell technology constant.

The dominant cell technology has moved from Al-BSF to PERC to mono-PERC to TOPCon. Heterojunction and back-contact cells are not yet dominant, but they are manufactured on a multi-gigawatt scale and will probably overtake TOPCon eventually. Each one of these changes has eked out more light conversion efficiency from the same area of silicon.

Cells mostly still use screen-printed contacts made from conductive silver pastes, much like 20 years ago, but there has been continuous evolution of the geometry and composition of applied pastes so that silver consumption per watt is now much lower than it used to be. This is important because silver has the highest cost per kilogram of any material in a typical solar panel, and it's the bottleneck material for plans to expand manufacturing past the terawatt scale.

Wafer, cell, and module manufacturing have become much more automated. That reduced labor costs, increased throughput, and increased uniformity.

In terms of resource extraction needed for the batteries and the panels, how sustainable is it? The way I understand it is that you can't really repair broken panels and batteries... Can we still make these after, let's say, 500 years? I have no conception at all in this topic...

No, but I don't see a good reason why you can't recycle the cells especially given they contain a thin layer of silver. Google already finds local recycling firms, since it's required by WEEE.

(The 500 years question has issues for all the other sources of energy as well!)

Yes, batteries are getting better at such a rate that you can recycle old batteries at end of life, lose 10% of the material in that process and build a new battery with new tech and less material that is better than the original.

The resource extraction issue is more than these are so useful we're going to build an ever growing amount of them.

Luckily they're made from widely available materials, with even more widely available substitutions possible e.g sodium batteries.

You can't repair, but you can recycle (although doing so likely isn't very profitable until the exponential price decrease stops)

The resources all start off chemically bound in rocks that aren't famous for spontaneously generating or storing electricity.

I don't see it being meaningfully more expensive to process smashed up old PV or batteries than starting from the natural state, and my expectation is that it would be easier.

The exception would be if some of the chemical pathways turn into low-concentration atmospheric gasses that then diffuse all over the world, which is how we got the problem with CO2 (and unrelated problems with CFCs).

Aside from silver for contact wires, PV panels are made (or could be made) with mundane materials available in essentially unlimited amounts. The total mass flowing through new PV panels each year if the US were fully solar powered would be much less than the volume of mundane material flowing through the system already. For example, the EPA estimated that in 2018 the US generated 600 million tons of construction and demolition waste (of which 143 million tons went to landfills.)

https://www.epa.gov/facts-and-figures-about-materials-waste-...

Thank you and other commenters for the great rundowns here. I'm interested in a related question and I wonder if you or others could point me in the right direction: why was the mainstream consensus around solar power (and/or batteries) apparently so wrong for so long? More specifically -- and maybe a better question -- why didn't progress in solar and batteries happen sooner?

I'm less interested in blame than in a systems analysis of how in the last half century powerful players seem to have missed the opportunity to start earlier investment in solar and battery technology. Solar and batteries are unique in energy infrastructure, as even any casual observer knows by now, and is certain to change many aspects of politics, industry and culture. It seems an inevitability that energy infrastructure will evolve from large complex components towards small and simple components, and I'm interested in engaging with the history of why "now" is the moment, rather than decades ago.

It's a false assumption that technological progress happens automatically or even that it's based upon the passage of time.

Progress happens as a result of many choices made by individuals to invest time and energy solving problems. Why is solar rapidly improving now? Because way more people are invested in making it better.

Nascent technologies almost always face an uphill battle because they compete against extremely optimized legacy technologies while themselves having no optimization at first. We only get to the current rapid period of growth because enough people pushed us through the early part of the S curve.

Sure, that makes sense. This is where I'm coming from with my interest in history:

I heard an interesting argument somewhere that solar cells are an ideal manufactured good. Whether you are building a module for a calculator or a GW scale plant, the modules are the same. This is fundamentally different for steam turbines. On the "concrete-internal combustion engine" spectrum of complexity, solar modules are closer to concrete and turbines are closer to ICEs.

Shouldn't this have led to a special interest in advancing solar module research? Or widespread understanding that eventually the unique set of attributes that define a solar module would lead to it's takeover of a significant portion of global energy generation? Shouldn't that have been apparent from the earliest days of photovoltaic research as a sort of philosophical truth before the advances in material science, extraction or manufacturing of the last fifty years?

I think another important part is that solar has low minimum useful quantities and customization. Lots of the problem with nuclear power is that you only need ~100 to power the US, and each one takes years to build, so getting scale is basically impossible. With a 50-100 year lifespan per plant, that means you only get to build 1-2 a year, and you can't learn much from the 5 you've most recently started since they're still under construction.

Solar and batteries got cheaper when we scaled up and built a lot. You have to pay current prices to get the next price drop, because it's all learning by doing.

If we had pushed harder in the 80s, 90s, and 2000s, solar might have gotten cheaper sooner. Solar fit in at the edges of the market as it grew: remote locations for power, or small scale settings where running a wire is inconvenient or impractical. The really big push that put solar over the edge was Germany's energiwende public policy that encouraged deploying a ton of solar in a country with exceptionally poor solar resources; but even with that promise of a market, massive scale up was guaranteed.

It's in many ways a collective action problem. Even in this thread, in 2025 you will see people wondering when we will have effective battery technology, because they have been misinformed for so long that batteries are ineffective that they don't see the evidence even in the linked article.

Also, most people do not understand technology learning curves, and how exponential growth changes things. Even in Silicon Valley, where the religion of the singularity is prevalent and where everyone is familiar with Moore's law, the propaganda against solar and batteries has been so strong that many do not realize the tech curves that solar and batteries enjoy.

A lot of this comes down to who has the money to spend on public influence too, which is largely the fossil fuel industry, who spends massive amounts on both politicians and in setting up a favorable information environment in the media. Solar and batteries are finally getting significant revenues, but they have been focused more on execution than on buying politics and buying media. They have benefited from environmental advocates that want to decarbonize, without a doubt, but that doesn't have the same effect as a very targeted media propaganda campaign that results in zealots that, whenever they see an article about climate change, call up their local paper and chew out the management with screaming. Much of the media is very afraid of right wing nuts on the matter and it puts a huge tilt on the coverage in the mass media in favor of fossil fuels and against climate science.

Indeed. You widen the conversation here, and remind me of the idea that moneyed influence is underrepresented in analysis and understanding of the world. Maybe the most appropriate way to understand big questions is who is funding the various players.

I like to think about "learn by doing". While I have of course lived it, I try to think of counterpoints. It seems clear that solar owes it's growth to Germany and California policies which subsidized the global solar industry with taxes on their economies, most disproportionately placed on individual ratepayers. But why couldn't solar research have been long-term funded based on it's fundamental value? Talk about national security, or geopolitical stability -- especially post 1970s! Skip the intermediate and expensive buildouts of the 2000s, failed companies heavily subsidized and fund research instead to hopefully bring the late 2010s forward in time?

What's a good model here, or concrete example? We see the same side of the history in electric vehicles. I think Tesla and Rivian, to pick two, both lost money on every sale in early years. Why not skip that expensive step in company history, and develop better products to sell at a profit from the beginning of mass manufacturing? Are there industries or technologies where this expensive/slow process went the other way?

> It seems clear that solar owes it's growth to Germany and California policies which subsidized the global solar industry with taxes on their economies, most disproportionately placed on individual ratepayers. But why couldn't solar research have been long-term funded based on it's fundamental value

I think this is a really important distinction, that between research in the lab versus research on the factory floor. Tesla in particular has talked about how much they value engineers that get down in to the production process versus those that are working in the lab. That's the "doing" that needs to happen. As well as shaking out parts of the upstream supply chains and making all that cheaper.

We can theorize about what's going to work in practice, but the price drops are the combination of 1% savings here, 0.75% savings there, 0.5% there, and until you have the full factory going you won't be able to fully estimate your actual numbers, much less come up with all the sequential small improvements that build on each other. And all that comes together in the design of the next factory that's the next magnitude up in size.

I hear that, it seems a common observation. Maybe a fundamental truth of enterprise.

> until you have the full factory going you won't be able to fully estimate your actual numbers, much less come up with all the sequential small improvements that build on each other.

Why not? Is there a theory or school of management or industry that establishes this foundational principle that seems so commonly invoked? It feels true, but I don't really know why it might be true. There must also be great examples of counterpoints in this too!

Maybe it goes back to learn by doing: it's a common refrain in outdoor recreation that safety rules are written in blood; that many of our guidelines directly follow from bad things that happened. But certainly we can also design safety rules by thinking critically about our activities. Learn by doing vs theory.

It's literally studied as "learning" in the management science literature.

For example: https://pubsonline.informs.org/doi/abs/10.1287/mnsc.2015.235...

> We find that productivity improves when multiple generations of the firm’s primary product family are produced concurrently, reflecting the firm’s ability to augment and transfer knowledge from older to newer product generations.

> why didn't progress in solar and batteries happen sooner?

The rate of progress in cost reduction has been astonishing. It's unlike anything except Moore's Law. This catches people out.

As well as the usual suspects: cheap fossil fuels, failure to take global warming seriously, belief that nuclear power would see similar exponential cost reduction rather than opposite, and of course anti green politics.

But if 95% cost reduction is the result of not taking it seriously, would taking it seriously earlier have been even better? Hard to say.

Right! Good points for optimism here, and acknowledging broken mental models.

We have silicon solar modules in the 1950s, Moore's law in the 1960s. Another take on the question then: today we use Moore's law to describe progress in solar modules, to what extent was that realization possible in the 1960s from the fundamentals, or "first principles"?

If it was clear, why did we not see rapid prioritization of solar and energy storage technology research? Or did we and I don't know the actual history? Or what influences am I undervaluing or not recognizing?

If it wasn't clear, why not? Gaming out many positive impacts of solar technology feels easy today in a way it appears was not easy in the past. Why wasn't it clear in the past?

Battery progress was in some ways slowed but also accelerated by oil companies who kept buying up patents on solar and battery stuff that looked promising, and then sat on the patents, refusing to license it.

One oil company bought Cobasys, which owned all the NiMH patents. Thereafter, Cobasys refused to license NiMH batteries to anyone making a vehicle, except large ones like transit busses. Several early EVs used NiMH batteries until Cobasys was acquired and set up the restrictions.

This really lit a fire under researchers and battery industry to try and improve lithium ion, which had hit the market in the early 90's. Once the price of Lithium Ion started falling, the market very quickly forgot about NiMH batteries. In about ten years prices have fallen to one fifth of what they were. That fall has slowed, but it's still dropping.

I have been off-grid with a small solar generation system of 2.5kwh of solar and 3.6kwh of battery storage for a year.

I had to run a generator a number of times during the darker weeks, but now we have longer days. I don't recall when I last ran it.

With solar, or any off-grid system, the number one thing that needs to change is you.

Switch stuff off, get energy efficient things, use power tools and charge their batteries when the sun is shining, use gas for hot water and cooking, and a log burner for heat (If I had my time again I would use a back boiler for water heating during the winter, and solar for water heating the rest of the time).

When I lived in a typical house, I averaged around 12.5kwh per day. Now, it's around 2.5kwh per day.

> a log burner for heat

for areas that experience winter, this is a decisive issue.

If you live in a passivhause-style home, air source heat pumps ("minisplits" for our US readers) may work, and you might be able (at least in the southwest of the USA, with high insolation during winter) to get away with local battery storage to cover your heating needs with PV.

But if you don't, PV-driven heating during the winter, even with the very high COP's of air source heat pumps, is not realistic without much larger battery systems than you could reasonably have on site.

Covering non-heating domestic electricity costs with PV these days is relatively easy, and we should do it as much as possible. Covering the heating part for places with winter climates (especially in areas with low insolation) is much, much harder and really requires effective grid infrastructure.

Ground source heat pump might help close the gap

> Therefore, they believe, we should deemphasize solar in favor of “firm” sources of energy like gas turbines, next-generation nuclear or advanced geothermal.

One cool thing about advanced geothermal is that it can load follow solar like natural gas does today: ramp down when solar is abundant and ramp up when it is not. That could come from slowing the turbines, or even by storing the extracted heat (in molten salt) during peak solar hours and using it to turn the turbines to meet peak demand or overnight.

They are in many ways a great complement for each other.

This is a great summary of the situation. I've been thinking about installing solar panels on my house, and been thinking about these same sorts of issues. Unfortunately, for my situation here near Chicago, things are much worse than the author's Atlanta: winter requires tons of energy here because it's very cold, and we have even less sun then.

It's one of the things that makes me think about wanting to move to Texas or Phoenix or something. Ample year round sun, and the big energy expense: climate control, corresponds much better to when you have it (you need to "cool" in the summer and the day). It rubs me the wrong way that here, our big energy cost is heating in the winter. It doesn't fit well with the utopian solar future I'm envisioning.

Assuming you would stay in Chicago for other reasons, the solution for a high heating bill is 1) air seal and upgrade insulation in your house, and then 2) replace your furnace with a low temperature heat pump.

Chicago has electricity prices 25% lower than the national average. If you want to see an example in your area, watch Technology Connections heat pump videos on YouTube.

Air seal and upgrading insulation: correct me if I'm wrong, but that implies either tearing open all of the exterior walls or ripping off all of the siding, no? If so, it feels like it would take a LONG time to recoup the cost of materials and labor for that job, unless there was literally no insulation in there to begin with.

Alex is a smart guy, and he makes a lot of convincing agruments in favor of heat pumps, but the thing he consistently sweeps under the rug is that for about half the US (and all of Canada), the annual cost to run a heat pump sits well between a natural gas furnace and resistive heating. And the further north you go, the more it shifts to the right. I run the numbers every few years and for my specific house, I'd pay 30% more to run a heat pump instead of a furnace. (Before factoring in the cost of the unit itself and installation labor.)

Where I live, the only way heat pumps make economical sense is if natural gas gets dramatically more expensive, or if solar gets cheap enough that every household can afford a roof full of solar panels and a basement full of batteries. (Which to be honest is kinda my dream situation anyway.)

We had an insulation upgrade recently when we ripped out our gas furnace and put in a heat pump. The biggest improvement was from spraying foam into the space below the first floor, where it rests on the outer basement walls. There had been too much air leakage there. There was also attic insulation upgrading. No walls had to be penetrated.

The house (built just a decade ago) feels much better insulated now.

> Air seal and upgrading insulation: correct me if I'm wrong, but that implies either tearing open all of the exterior walls or ripping off all of the siding, no?

If you do the exterior walls yes, but most heat loss is through the attic and roof. Air sealing and super- insulating the attic floor is pretty cost effective. Likewise sealing cracks around windows and doors.

> the annual cost to run a heat pump sits well between a natural gas furnace and resistive heating.

Why is that? Maybe I'm missing something fundamentally, but this should be a strict function of COP, $/kWh (elect.) and $/kWh (gas) right? The insolation thing is kind of red herring, because that saves kWh-needed and that goes into both, right?

And yes COP will probably be bad/worst on some days of the year. But on most days even Chicago should get a pretty decent COP from a low-temperature heat pump. Is natural gas just so cheap in Chicago?

for price of heat pump you can buy 3-6 times bigger PV array.

heatpumps are not expensive but they are not cheap COMPARED to other alternative. cop is not constant, it changes. closer the outside temperature and indoor temperate is, less work is needed / higher COP heat pump provides.

buying 4 times more panels gives you always 4 times more energy. in -40F you get 4 times more energy from 4 times bigger pv array. heat pump will probably just start running integrated resistive heater IN THESE temperatures.

heat pump can be configured in a way that it not only heats but also cools, so yes in that situation heat pump can be cheaper. then not having one and be less comfortable / productive because of it.

you can buy PV system and after it paid itself, it still works, still generates electricity. gas can not be 0 $. so depends what / how you calculate things.

I second the other reply. I live in Chicago and installed an air source heat pump. (Mitsubishi hyper heat). Its served me well for two winters so far. My next step is probably to replace all my windows and doors to get better efficiency.

The great (!) article misses the holy grail of the Energiewende in the chapter „Addressing the challenges of solar intermittency“: a intercontinental smart grid. As shown by data of ENTSO-E in Europe a power system plays a crucial part to overcome intermittency problems of renewables.

How do the costs of long distance, high voltage lines compare to batteries for addressing solar intermittency?

It really depends on what you call "long distance". Anyway, transportation loss for entsoe is public data [1]. You'd need to cross it with production/consumption data [2] in order to get relative numbers.

For instance, France consumed 442 TWh and reported 1.07TWh of losses in 2022, which would be about 2.5% transportation losses.

[1]: https://eepublicdownloads.blob.core.windows.net/public-cdn-c... [2]: https://eepublicdownloads.blob.core.windows.net/public-cdn-c...

Keep also in mind that batteries do two things: They can move loads in time, but they can also reduce transmission capacity requirements by increasing utilisation. As long as there is some time where the transmission line is not fully loaded (which today is true for _any_ transmission line even the limiting ones), then a battery on both ends allows you to use the capacity longer by charging the battery before the bottleneck with excess and once the input falls below discharging the battery to keep the line utilisation high.

The downside of this is that you now have a system that comes with all kinds of nasty additional complexities and failure cases from control theory.

I mentioned this yesterday, but storage is the new holy grail for cheap energy. If humans could focus on building safe and reliable battery tech instead of AI and bitcoin, we will have solved the energy crisis until fusion is ready.

There are studies (at the bottom of my post: https://news.ycombinator.com/item?id=43424310) showing that storage is mostly a political issue.

We already have safe and reliable battery tech being deployed in massive amounts as is in plentiful evidence in this article.

Solar with IRA subsidies is $30/MWh in the US, without subsidies it's $50/MWh. Current storage prices are probably no more than $60-$70/MWh for storing solar for later. New natural gas is $95/MWh at current gas prices.

Similarly, fusion does not promise cheaper energy, at least I have never seen a numerical argument that could support that. If you have one, I'd love to see it. Fusion is mostly interesting because it doesn't exist so people can project whatever characteristics they want on it.

Helion hasn't released details, but they imply they'd be much cheaper. At this point I can't disprove that, as their scheme does do away entirely with turbines and generators and could have much lower cooling requirements.

Fusion is ready, and it's been ready for about 4-ish billion years. Once you deploy the panels needed to collect space-based fusion, there will likely never be an economical argument for Earth-based fusion. There's only so much simplication you can apply to a machine designed to contain a miniaturized star, especially compared to a dead-simple dirt-cheap solar panel.

You say "likely never" but eventually we'll have covered the earth's surface in solar panels. Unless we are transitioning to space based solar and transmission we'll want fusion to increase energy generation beyond surface irradience of earth.

In the meantime, solar panels for massive generation also incur transmission costs to centralize that energy for any major energy usages. We might want to keep having high power generators next to super-high energy consumers. For instance our (theoretical) hyperspace communication and computation array. Right now those usages are things like Arc Furnaces, Aluminum smelters, data-centers, ...

Plus, we'll want to have figured out that fusion tech so we can build it into our spaceships travelling out beyond Mars as an energy source and hopefully also a thrust source. We want to master that tech on Earth's surface for sure.

> covered the earth's surface

In any discussion of far-future considerations like this we need to remember that thermodynamics requires all energy used for work to become heat. Covering the Earth's surface in solar panels is one thing, but by the time we're covering every inch in fusion power plants, we've turned the Earth's surface to lava from all the waste heat. There's a physical upper bound on energy usage within the Earth's biosphere that prevents useful energy production from scaling to infinity, and as a result we'll find ourselves optimizing for economics rather than being limited by energy production per unit of area.

As for industry, yes, it seems likely that industry will still represent a large and relatively centralized consumer of power which may benefit from a large dedicated installation. But I'm not convinced that fusion will ever be more economical than even traditional nuclear fission energy (just because your fuel is relatively cheap doesn't mean a thing if the plant itself is essentially disposable because of the energies involved).

As for space, maybe, though considerations of space exploration aren't driven by economics, so whether or not anybody ever figures out a viable fusion reactor design for a spaceship could have as little relevance to civilian power generation as your classic RTG did.

Plot twist: the death star was originally conceived as a contraption to regulate waste heat in artificial planets.

> You say "likely never" but eventually we'll have covered the earth's surface in solar panels. Unless we are transitioning to space based solar and transmission we'll want fusion to increase energy generation beyond surface irradience of earth.

> In the meantime, solar panels for massive generation also incur transmission costs to centralize that energy for any major energy usages. We might want to keep having high power generators next to super-high energy consumers. For instance our (theoretical) hyperspace communication and computation array. Right now those usages are things like Arc Furnaces, Aluminum smelters, data-centers, ...

Well before we cover the entire globe in PV, the mere fact that the panels absorb a lot of light means they will change the planet's albedo, heating things up.

But any source of power on that scale will also increase the planet's equilibrium temperature (regardless of if it's PV, fusion, or even if we figure out how to harness dark energy/zero point shenanigans) so we want space-based power before then — and the industrial capacity to use that power in space, because simply beaming it down to Earth is still going to heat up the planet just like any other power source.

Before we even get to that point (in fact, already today) humanity is manufacturing enough metal to make a global power grid with only 1 Ω of resistance the long way around. The limiting factor is geopolitical, not technical, because it's literally just China making enough of the relevant metals.

There seems to be a real cultural obsession with going off grid, that this article reflects.

It's therefore confusing if they're talking about a nation/state or a household.

For a household, assuming you don't want to disconnect from the grid, the calculation is about how to offset as much of your energy costs you can displace with solar, and how to shift cheap energy from overnight with batteries as well as time shift solar generstion. A different and in many ways more interesting question in the abstract while also more practical too.

With net metering going away now people want batteries for self consumption, then the grid becomes a backup.

In my area we still have net metering but the grid tends to go down a lot with even a mild storm, so many have backup propane generators, however some like me are doing whole house solar with batteries for backup instead, it cost 3x as much but pays you back over time with little maintenance compared to a generator.

I will admit there is a prepper aspect, with well and septic and solar the only thing I need is food which I can try and grow. The Sol-Ark inverter in my install even offers EMP hardening which I almost went for :).

Getting grid hookup in rural property can be expensive or impossible depending on where you are at, solar with satellite internet means no problem wherever you want to build if done right.

Evolving this line of thought further, if you do not want to disconnect from the grid, there's also an option to participate in the electricity market.

Someone with a battery can buy up cheap electricity at night or whenever their electricity supplier deems it off-peak and thus cheap, so a battery can heavily influence the average price of energy as calculated here by Michael de Podesta: https://protonsforbreakfast.wordpress.com/2025/02/16/the-mos...

The other way to participate in the electricity market is that in EU the end users can access a plan that in some way reflects day-ahead market prices. If you have a battery, you can now buy the midday solar dip around 0 eur/mwh energy plus network charges and sell at the evening price of 300 eur/mwh.

The duck curve can be easily flattened by using vertical panels which extend the production of solar a few hours in each direction. Vertical panels take no space (think every fence; or on farmland with enough space for big machinery to move), better performance (because heat isn't trapped), panels are always clean (daily gust of wind takes care of it). I'm sure there are many HN discussions on vertical panels.

There's really no such thing as the California grid from a reliability stand point.

California is on the western interconnect, which is organized by wecc.

The power on the western interconnect is more like 20% wind/solar.

https://wecc-spdp-weccgeo.hub.arcgis.com/pages/power-generat...

Great article. I'd be interested with something similar for industrial and public transit cases.

I totally get that it's feasible to run a common household with 100% solar+batteries, but I'm less convinced a train or an hospital can be run during a winter evening with solar+batteries alone. Let alone one of those new fancy AI datacenter.

other way to deal with intermittency is to dynamically price electricity. then people can shut off/on usage in response. many activities do not need to be done exactly at a certain time.

it doesn’t all need to be fixed on the supply side

solar is nice for residential. you will still need gas for cooking + water heating. ohh yeah plus transportation i.e hybrid for long distance travellers or pure electric for city travellers.

anything else i.e industrial both heavy & light manufacturing nothing beats hydrocarbons

This article is good overall, and the map of solar capacity factor by US state is especially good, but it does have some flaws.

First, and most trivially, Potter's plot of PV module prices overstates their cost by a factor of about three to five. His last data point is US$0.31 per (peak) watt in 02023. https://www.solarserver.de/photovoltaik-preis-pv-modul-preis... shows a price of 0.26€ per peak watt in June 02023 for "mainstream" solar panels, which is in reasonably good agreement. But "low cost" panels were only €0.16/Wp, and since then prices have dropped by more than half, to €0.110/Wp for mainstream panels and €0.070/Wp for low-cost. (A footnote misstates this cost as $36 per megawatt, which would be $0.000036/W.)

Prices in the US are of course much higher, but that's due to inefficient regulatory interference in the market to protect uncompetitive and environmentally destructive fossil-fuel interests.

Another weak point is that the article doesn't consider thermal energy storage systems, neither sensible heat energy storage systems like a hot water heater or a sand battery, nor phase-change energy storage like the ice chillers used for decades in many office buildings and the MIT Solar I house built in 01939†, nor TCES systems using desiccants such as muriate of lime, carnallite, or tachyhydrite. Sensible heat energy storage has been a crucial part of domestic climate control for millennia, for example in the form of adobe, and can time-shift your entire HVAC energy load to hours when your solar panels are producing. The newer systems may be able to do the same at a lower cost and are certainly easier to retrofit into existing construction. This will dramatically drop the storage requirements for things like his example house, though it will not help with transportation and much industrial energy consumption.

Maybe its most glaring weak point, though, is that it compares costs in the US and Europe, but entirely ignores China, where the vast majority of new power plants are being built, where the majority of world coal consumption happens, and where the overwhelming majority of photovoltaic panels are made. (India and the Middle East are also ignored and may turn out to be very important, but at present their potential is largely unrealized.) Writing an article about understanding solar energy this year without talking about China is like writing an article about understanding automobiles in 01940 without talking about the US. You can probably find a magazine article from 01940 that does that, but probably only in French.

______

† You could argue that the qanat represents a form of ancient Zarathustran phase-change energy storage that is much older than MIT Solar I, but I think that only applies if your buildings are responsible for condensing the water to fill the qanat.

There is also a risk factor to be considered before we decide to add massive energy storage within residential area. I've hear that one of the reason why the recent wildfires in LA had been so devastating was because the amount of available energy to fuel the fire (tanks, batteries) around modern homes is much larger than in the past.

I'm extremely skeptical of that claim. I'd buy that, on the scale of individual houses, a large battery bank could make a fire worse. Once you get to the point of whole cities burning, I just don't buy that batteries make a difference. I _might_ be willing to believe that in some narrow technical sense some homes burned hotter or faster because they had batteries. I don't buy at all that, at the big scale, number of homes burned or total damage incurred was higher.

That being said, yes, utility scale batteries do pose somewhat of a novel risk, especially as they are new and we are figuring out the engineering. A new installation in Moss Landing has burned twice in the past several months, although according to reports, the damage was entirely contained to the facility.

A 40 kWh battery stores about as much energy as the bag of coal in your garage for the next barbecue.

If you could efficiently extract the energy, which you can't. A typical coal plant is 33% efficient. You can get 100% efficiency converting the coal to heat, but a heat pump can convert that battery energy to heat at 300-500% efficiency.

For the purpose of "burn your house down", the energy is usually extracted fairly efficiently from both coal and a battery.

And from the large amount of wood and other combustibles that make up the house and its contents.

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