The humble water heater could be the savior of our energy infrastructure woes
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It's the maximally outsourced air-conditioning solution I ever saw :)
The name puts me in mind of a chain called District Taco, but unfortunately that doesn't mean a supply of tacos piped directly into your house.
Not even slightly authentically Mexican, but nonetheless quite tasty.
It's used by some datacenters IIRC.
https://en.wikipedia.org/wiki/Enwave#Deep_Lake_Water_Cooling...
75% less energy than traditional air conditioning.
Instead it's used as an input to the filtration plants, cleaned, and used as municipal water. I'm not sure what the overall effect of getting slightly warmer water in the municipal system is, but I bet it's a win overall since we spend so much energy heating up water (as per the article!).
Edit: also the lake is 1600 cubic km of water, so I dunno if we could ever noticeably change the lake temperature this way.
By comparison, the lake's surface area is 19000 km², so when the sun is shining on it (at a slanting angle, as it always does that far north), it's receiving about 10 TW of solar energy, half the amount used by the entire human economy. It reflects about 10% of that into space and converts the rest into heat, then re-emits it as longwave infrared light, half at night.
It starts off talking about wanting to move energy production to renewable sources. Great, I'm with you so far. A major issue with renewable energy (solar and wind) is that they're variable, not constant. This results in uneven power. The wind doesn't blow, it's cloudy or it's night time. So we need a way to convert this variable renewable energy into constant energy that's accessible around the clock. An obvious solution to the problem is to convert the renewable energy into stored potential energy. This is what pumped hydroelectric dams are all about. Use the variable energy to pump a bunch of water up behind a dam, then release it when you need a more constant supply of energy.
Great, so we've got that much figured out. The world needs a way to convert renewable energy into constant energy.
And the solution to this problem is... the distribution of more efficient water heaters.
Wat
How do more efficient water heaters in any way, shape or form help solve the renewable variable rate energy to constant energy problem? I feel like I must be missing something obvious. Are we able to somehow store energy in heat-pump based water heaters and then extract that energy to run other items in our homes? When you store energy in a heat-pump based water heater does it not need to run at night when renewable energy sources are lowest?
Can anyone explain to me what the heck this article is talking about?
I feel like I'm missing the larger picture, but I don't see how these two concepts (energy storage and appliance efficiency) are related.
A large portion of our world energy use is to make heat. Thus if you can make the heat you need when there is plenty of renewable energy available, and then store it for use latter that is a large win. Sure we can't turn that heat back into electricity (false, but they are not worth talking about), but since heat is the goal that doesn't matter.
This is well understood. My parents have been on a off-peak water heating program since 1988 (in all those years they only ran out of hot water 5 times, and nobody was trying to save water). Based on that experience, just the hot water a family uses in a day is in the 300-800 liters range (go high - running out of hot water for the day sucks). Heating your house is a lot more though - 40000 liters is a low end estimate I've seen.
You won't be cooking food, powering your car, or lighting your house this way, but it is still a cheap and useful way to store energy. It is also something we can do for the world using yesterday's cheap technology.
I just thought the framework of his argument was rather odd. Better water heaters are framed as being a way to avoid constructing power storage systems that convert variable renewable energy into steady baseline power, which feels like an argument that doesn't hold up. We'll still need some way to supply steady power to run AC units, heaters, and other big power draws all night, no matter what type of water heaters we use!
He also, confusingly, makes a second point about how efficiency can to avoid building powerplants/storage.
Replacing old inefficient heaters with new smart and efficient heaters is a double win.
If you power them from renewables it's a triple win.
Also night time energy is often low carbon because of nuclear and wind combined with low demand, but modern smart heaters can respond at a much smaller scale to use "excess" energy.
Not really or at least that represents a gross simplification of the situation.
Electricity demand is anything but constant - peak to trough intraday consumption can vary by up to a factor of 5. Grid engineering is all about matching lots of different sources with different generation characteristics with a varying (but quite predictable) demand curve.
All generation sources are intermittent - they are just intermittent in different ways. Solar and wind have well known limitations in this regard but at least the variation in output is predictable - particular solar, wind is typically accurately predictable up to a few weeks horizon.
The intermittency associated with thermal plants may be less in some ways but it has the disadvantage is that it is largely not predictable. For example, the average US coal plant will be unavailable for generation 15% of the time - so roughly 1 hour down for every 6 hours generating. Most of this 1 hour downtime is unscheduled/forced which is unpredictable. It's a myth that having a 1GW of fossil fuel generation capacity means you can reliability meet a peak demand of 1GW.
Also nuclear and coal are NOT good at load following - they operate most efficiently when producing the constant design output. Ramping up/down coal or nuclear output quickly is often not at all possible or is possible - depending on plant design - but with a large loss in efficiency and increased plant stresses and wear and tear.
Grid engineers have been maintaining this balancing act between unreliable generation and fluctuating demand for ever. In the past the focus was on coping with the intermittency caused by the failure modes of thermal plants. Increasingly now they are coping with the variable output of solar and wind generation but seem to be managing this - a bunch of European countries source more than 40% of their electricity from solar or wind and none required utility scale li-ion or have experienced increased grid instability.
The same tools are used to handle wind and solar intermittency as are used to handle thermal plant failure or inability to ramp up/down quickly - some hydro storage, backup idling natural gas plants, grid interconnections, etc.
Fundamentally the renewables revolution is happening quietly in the background is driven by simple economics. Coal and nuclear are just too expensive by a factor of 2 or 3 and natural gas, on-shore wind and utility scale solar are just so cheap in comparison. It's cheaper now to build a load of wind (or solar) and some backup natural gas generation - typically with a capacity factor of only 10% or so - than it is to meet demand with thermal fossil fuels. This is because wind and solar are capital intensive while NG plants are cheap to build but expensive to operate due to fuel costs. This combo (idling natural gas and wind and/or solar) is in the process of displacing everything else. 90% of the new generation capacity added in the US last year was of this nature. And a similar proportion is observed globally.
Meanwhile you have endless arguments about why wind and solar "cannot work" in fora, while all around the world it clearly IS working and analysis suggests it requires no technology breakthrough to get to 60%-70% carbon-free generation - many grids are well along this journey (40% to 50%) and none of the doomsday scenarios of massive load shedding, black-outs, etc. have occurred.
Texas suffered a doomsday scenario last winter, power demand far exceeding renewables ability under prolonged bad weather. California has frequent rolling blackouts; bizarrely, solar roofs are disallowed to supply the homes they cover.
The Texas story actually reinforces one of my points - thermal fossil fuel plants are unreliable also as the failure of thermal plants caused a far greater loss in capacity than that lost by renewables.
California's electricity has been a mess for decades before the recent growth in solar and wind so I'm not sure how you can claim a causal relationship between what's happening now in California and the expansion of wind and solar.
Regarding domestic roof-top solar PV - I currently don't see it having any role to play in the march towards carbon-free energy - the cost per KWh is just too high and in many countries is only made viable by large government grants and feed-in tariff guarantees which effectively allow a domestic installation to exploit the grid like a giant infinite and free battery. Utility scale solar is completely different - it costs about 1/5 of the price per KWh compared to roof-top domestic PV and in many markets is now competing and beating conventional thermal generation on price without government support.
One big advantage is that they can also be run in reverse so you could cool the house in summer (although you might need a special heat pump to do this, especially to separate from the hot water). In areas where it gets very cool, one can also use connect the heat pump to the ground as heat sink which improves efficiency even more.
Insulation is _dirt cheap_ compared to lifetime heating costs AND it also keeps the house cool during the summer. Such a no-brainer.
It's only one data point, but I'm in New England and from my home office I've watched builders replace 3 1960's-era homes with large colonials. Each is insulated with fiberglass, no visible foam, and nothing outside the sheathing (exterior plywood) except vapor paper / tyvek.
Sure, it meets code requirements for inches of insulation, but it's far from air tight or efficient.
This is how your thermos knows wether to keep your drink hot or cold.
So except for the sun shining through windows, insulation keeps heat out of your house.
Of course, once the heat is in, you need a way to get it out (at night, through windows).
Unlike a greenhouse, insulation is not directional.
The biggest problem though is the dryness during the winter, cold air comes in and expands, lowering the relative humidity, warm moisturous air is pushed out by mechanical fans. You get extreme dryness, lower then in the desert, which is not good for mucus membranes. I believe that if we could revolutionise air conditioning systems we could prevent the next pandemic (and maybe help the global climate).
Most people these days want more than natural cooling. As soon as you decide to have an AC system installed more insulation is better for the reasons you state.
I'd think barns would have very low mass in comparison to their size, but would stay close to surrounding temp by way of having very little insulation and being very "drafty"
It doesn't completely shift the issue to later in the season. Yes, it will shift some of it, but you still have the night/day average effect. This can still be beneficial, especially if in a shady location.
Barns can be drafty if you are talking about wooden barns. Stone barns, or stone foundation barns built into a hillside, can actually be cooler inside than outside during the heat of the day. That's part of why horse owner sometimes leave their animals in the barn during the day and turn them out at night (typical summer schedule).
That has similar issues with peak load to AC in the summer but most people do not live in places which are consistently so cold that you don't have a significant amount of time where the heat pump efficiency savings are substantial. As a matter of public policy, encouraging systems which work for 90% of the population is an easy call — especially because that can pair with code changes and subsidies which work anywhere (insulation, install of ground cooling loops, efficiency improvements, etc.).
Heat pumps work in Alaska:
* https://www.nrel.gov/news/features/2021/even-in-frigid-tempe...
https://www.nordicghp.com/2017/01/heat-pump-effective-temper...
What if homes had some kind of centralized modular heat exchanging infrastructure? That way we could move heat from hot things that need to be cold to cold things that need to be hot. Move heat from my computers to a water heater or something. Gotta use all that excess heat for something, right?
I don't get why this is an advantage. That's just plain old air conditioning, which is genreally considered to be a wasteful, energy guzzling luxury in colder climates.
The heat pump hype is a bit puzzling to me. Here's a TreeHugger article which puts it better than I can: https://www.treehugger.com/why-are-there-so-many-fist-pumps-...
Heat exchange in the house happens through floor heating. So during a hit summer, the reverse capability just pumps the cold water through our floors (controlled for the dew point) and the warm floor water into the ground. That, combined with controlled ventilation over a physical heat exchanger, keeps the warmth out. Or, during cool seasons, the warmth in.
Our heat pump uses about 1 Kwh electricity (from ecological resources like water or wind only) to generatev3 to 4 Kwh of heating. Without producing carbon dioxide. Airflow based heat pumps are less efficient, and more noisy outside, of course.
Good point. The source and destination of heat can be air, water, or "ground source". But it's still all just the same concept as A/C units. Pump heat to one place, using less energy than what it would take to heat it using resistance heating. There is nothing special about ground source heat pumps, except that they're a pain to install in densely populated areas.
All types of heat pumps, unfortunately, often leak. Depending on the type of refrigerant they use, this can be a serious climate concern as well.
A/C or heat pump efficiency is directly related to the temperature difference over which you're trying to pump. If the temperature difference is twice as large, you need to spend twice as much energy to pump the same amount of heat.
Furthermore, the days where you need a heat pump (or A/C) the most are the peak cold/heat days where the temperature difference between your house and the air is much larger than usual. Because of this, a ground source heat pump can do the same thing by spending much less power than an air source heat pump, so it is "greener" - though the installation is more cumbersome and expensive.
As for the "pump heat from here to there" ... while we are cooling we are warming the ground below. And as at our place, the ground's consistency keeps the warmth rather local, we reuse it later when we warm our water during the night.
We do live in a densely populated area and about every fifth hoiuse built here during the last 10 years uses a ground-based heat pump. As for electricity use: each house has two hours of "blockage" where the pump is not allowed to run, so that the power lines aren't stressed. That's no problem at all, because all houses are highly insulated and thus buffer rather good.
Also, you have your units wrong. Electrical demand is measured in just kilowatts (kw). Actual usage is in kilowatts-hours (kwh) which is just an unusual way of saying joules.
It's fine to talk about it in terms of energy as it would be to talk about it in terms of power.
And I'd argue that kWh is exactly the usual way of saying 3600000 joules.
Also name "geothermal heat" for ground heat pumps might be a local US marketing term. In international English geothermal means rather what Iceland is mostly doing. Pumping water into very hot rocks deep below to extract heat. And it doesn't work in reverse because it would be additional work to pump heat into very hot rocks instead of dumping it into the air or into the cool ground 2 meters below the surface.
https://www.energy.gov/energysaver/heat-and-cool/heat-pump-s...
Geothermal works with either vertical holes in the ground or a big loop spread out horizontally. Neither one is very deep nor does it involve hot rocks.
Geothermal heat on the other hand is a wider term https://en.m.wikipedia.org/wiki/Geothermal_heating of which geothermal heat pumps (ground source heat pumps) https://en.m.wikipedia.org/wiki/Ground_source_heat_pump are just a subset.
Anyway, for one unit input we got about 3.6 units of output, which has been produced with an almost zero carbon footprint, as we buy only ecologically produced electricity.
And yes, English is a second language.
This is only true when the ambient temperature dips below the geothermal temperature which depending on your location should make you prefer one over the other.
And last but not least: ground / water carries much more energy per volume unit than air does. So air based heat pumps would make more sense in Europe's south and less sense farther north.
The tubes are about 100 mm in U-form, drilling mostly is offered in combination with the heat pump. And costs where payed of after about 7 years.
Costs and problems depend on the ground's structure. When I talked with the guys of the drilling team, they told me that problems occur if they work in hill regions with cavernous spots in the ground. That's because the tubes need firm contact to the ground to transfer heat.
Edit: here's an image of the drilling machine in operation: http://www.cynix.net/2008/img_1757.jpg and the tubes are those black ones on the rolls in the front.
In cold climates you eventually hit an efficiency wall with the air-exchange units and need to use a ground-source heat pump, with glycol pipes being run deep in the ground to exchange heat. And/or also have a supplemental source of heat that only comes on during the very coldest periods (oil-fired furnace, natural gas, cast-iron stove, or even resistance heat).
In hot climates you can increase the efficiency of a heat pump by adding water mist, making it a hybrid swamp cooler. Evaporating water will take out a bunch of heat energy.
As was mentioned, insulation is key otherwise you're just spending money on heating or cooling the outdoors. Walls, door, and windows that don't have thermal bridges, controlled air exchange with the outdoors (ERV energy recovery ventilator units), and so on.
They have been remote-controlling water heaters in New Zealand and Australia since the 50s. Just a simple relay installed in each house that responses to extra frequencies on the power lines in the 160-1600hz range. It's called ripple control, for obvious reasons. Each home gets assigned to one of several channels in each area so they can have more fine grained control of the load.
While this is true for basic resistive electric water heaters it's not for modern heat pump water heater which have energy factors of 3.5x which more then makes up for the 34% efficiency of a simple gas power plant (more modern combined cycle plants are 50-60% efficient) and the 95% efficiency of the grid.
Still works out much cheaper to use gas than electricity for heating in California with gas at $0.06/kWh vs $0.26/kWh for electricity.
Not to mention that piping all that natural gas out to each home has to result in a certain amount of leakage and energy cost in just the pumping itself.
[1] https://www.eia.gov/tools/faqs/faq.php?id=105&t=3#:~:text=Th....
Figure on the order of 60% efficient for the best natural gas power plants vs. 95% efficient for a condensing gas water heater. Not to mention the drastic reduction in expensive electrical infrastructure, the power plant, etc.
I wonder how from a pure greenhouse gasses perspective, the numbers stack up. I know that leaked methane is much worse than CO2. 28x according to [1]
This source [2] says that the grid looses: 2% - 5% of gas between provider and consumer.
Even assuming that your grid is 90% just gas plants stil.
30% loss at the power plant, 5% loss from electrical grid. So for every unit of water heated you are wasting 35% of the energy.
Vs say 2% loss in the natural gas grid. but that 2% is 28x worse than burned CO2.
Am I completely wrong in saying that from a pure this hurts the planet more electric based water heaters often probably still win?
[1] https://www.epa.gov/ghgemissions/understanding-global-warmin... [2] https://pubs.naruc.org/pub/FA86BB52-AE3F-D8AC-B295-801BD6DC6...
Assuming your electricity comes from gas plants.
The grid is getting greener which means you win by even more if you electrify everything.
If you have a gas line to your home the most efficient way of heating would be to have co-generation gas turbine than makes heat and electricity and then use the electricity produced to power heat pump.
First, a gas-fired power plant converts about 40% of thermal energy to electricity, discarding 60% to further heat the planet. Then a few more percent are lost in transmission lines and voltage-lowering transformers. Only then that electricity is used to heat water or air in one's house.
If you just directly burn that same gas in the house to produce heat, it's nearly 3x as efficient.
The best coal plants can archive 47% efficiency, https://www.brighthubengineering.com/power-plants/72369-comp...
I only mentioned the gas-fired power station to make it an apples-to-apples comparison. It would be hard to compare e.g. to solar panels, even though direct hearing by concentrated sunlight might be feasible.
It's worth it for a larger volume though. Not so much for a small flat.
A typical solution is recirculating the water so that it stays hot.
(I have a gas tank heater and the faucets far away take a bit to warm up, because of the water in the pipes)
I bought a used Wemo plug for $10 and set it to only be on for 3 hours in the morning and 3 hours at night. Now we have hot water at any of the times when we actually would want it, and we aren't wasting money/energy to keep hot water on tap 24/7.
The problem is using devices that are either timed or (even worse) just runs 24/7.
Ideally you'd want one that runs on demand when triggered by a switch: hit the button, it runs for 30-60s while you undress, and then we you turn on (e.g.) the shower the water is already hot.
The hot water supply for the shower should be the same as the sink, and so when you go to shave or brush your teeth, that's then already primed as well.
Do a search for "Gary Klein", who has written a lot of designing good hot water systems over the years.
And they cool the air around them, so if you live in a hot area they save more.
In this same remodel I also convinced them to get heat pump / AC combo unit to replace the old gas furnace. Again amazingly cheap (even compared to gas), but also higher upfront cost.
This is in a coastal California region, so I'm not sure how well these heat pump solutions will work in colder places (ice would likely form on the heat pump near freezing, limiting its capability), but if anyone is looking to upgrade either a hot water heater or an AC unit, I cannot recommend the heat pump option enough (if you can get through the higher up front cost).
The worst case is efficiency approaches resistance heating at 1.0, maybe with backup resistance heat strips. But a well designed system to match worst case load should rarely see this.
For some reason they've really only been widely available in the US in the past few years.
Well actually it'll see it quite often. Every time a heat pump goes into defrost mode it'll use resistive heating inside to hold over while it's working like a traditional air conditioner to thaw out the outdoor coils.
I think it's cheap energy. In places like Japan they've been using heat pumps a long time
To make the installs cheap, these systems use flare fittings that almost all seem to leak. Couple that with the fact the 412a systems run at high pressure and you get a lot of leaking refrigerant.
No HVAC techs I’ve met like the 412a systems and most seem to be hoping for more sanity from r32, though that will have its own set of problems (flammability)
Also, if you are worried about the refrigerant leaking, you can sacrifice a little bit of efficiency and buy a unit using CO2 as a refrigerant with a GWP of you know: 1.
I think the biggest problem here for leakage are random construction dudes cutting the pipes when they demolish or remodel homes. If only they could gather the gas in the outdoor unit before, all of it would be saved.
There is no excess indoor heat in winter in 99.9%+ non-passivhaus homes.
(They would however de-humudify the space they are in, but that's another thing...)
I'd argue that every house that has any sort of ventilation, even naturally aspirated ones, have excess heat in that any amount of air leaving the house "unreclaimed" while there is any heating need contains wasted energy.
Heatpumps using that energy are very prevalent in the Nordics and Scandinavia, even with a majority of the time being heating season here.
Refrigerant leaks are still an issue though, but moving to hydrocarbons and CO2 will mitigate that. Even R32 is a step up in that regard.
Incorrect. Or rather not necessarily correct. Pumped hydro does not necessarily require damning a river.
> Making matters worse, about a quarter of the energy is cannibalized to do all that pumping.
Pumped hydro is largely considered one of the most efficient forms of energy storage, beating most other methods by a fair amount.
> This approach can be deployed far faster than dam construction, and free of protest (except perhaps from dam builders).
We can't do both?
I don't like the idea of the grid or cloud controlling appliances in my home. If I could program the run options myself based on the power company's recommendation (like a programmable therostat), that would be better in my opinion.
We use it to warm a 240m2 house with four inhabitants. It works well down to -10 to -15C.
During the night we pay only have the price per kWh to the utility company (as they have excess capacity during that period).
It works great and it pays itself back quite fast.
It's not controlled by any cloud. You can regulate on the control panel how and when you want it to run and it adapts with the weather too if you want.
If your refrigerant can reach -20 in your system, and it's 30C outside, then your refrigerant is exchanging 50C of energy per cycle. But if it's -15C outside, the best you can achieve is 5C of energy exchanged per cycle. And at -20C outside, you can't exchange heat at all.
That's a bit hand-wavey and not exact units, but I think it accurately describes the problem.
What the above poster is saying is that as temperatures drop, the system gets less and less efficient. For some environments, it may become cheaper to use resistive electric instead.
The 'Technology Connections' channel did a series of videos about heat pumps that are fascinating and I highly recommend: https://www.youtube.com/channel/UCy0tKL1T7wFoYcxCe0xjN6Q.
They do run about 2x the price of a non-hybrid (My local hardware store has an 80 gallon hybrid for $2250 vs $1080 for the non-hybrid) but my power company is offering a $500 instant rebate as well as the county offering a $300 rebate, so in my case, it's a few hundred extra bucks for a few hundred dollar annual reduction in my power bill.
I find the benefits to be marginal when using an average 40 gallon or less and only using it for 1-2 people. The use of water conserving fixtures further reduces the benefits for smaller tanks with fewer people (not sure they even make them smaller than 40 with the heat pump). With the exception being for people in hot climates with the tank in the garage or similar space.
The water heaters I saw were not running ducts to the outside, they use the room air. The point is that heat pump efficiency is tied to the ambient temperature. The hotter the air, the easier it is to collect the heat from it. So when it gets cold enough the "emergency" or "auxiliary" heating coil starts to be used (resistance based). This is very common in cold climates. My house heat pump auxiliary tends to kick in when the tempature gets below 40. This would also apply to water heaters if using outside air than the warmer basement air. Of course you are heating that basement air with another source, so that efficiency should be evaluated too (likely a heat pump because if you have a gas furnace, one would be likely to have a gas water heater too).
"It's not controlled by any cloud. You can regulate on the control panel how and when you want it to run and it adapts with the weather too if you want."
The proposal in the article is that smart water heaters could be controlled by the utility companies.
"It is then used for heating the house via radiators as well as for warm tap/shower water."
That is one type of system. The article is talking the US, in which the type of system you describe is relatively rare. The 10 million annual water heaters they reference are overwhelmingly used just for tap/shower water.
The article just wanders aimlessly between lies.
Pumped Hydro dams are tiny compared to hydro-power or water dams and are beautiful, the same size as solar or wheat farms. A cool seawater based one in Japan - https://www.google.com/search?q=okinawa+pumped+storage+&tbm=...
A good example of a government doing something that worked is the Australian government which wanted to spend money fighting the global financial crisis so insulated homes. Unfortunately deaths from the scheme, which were at the same rate as normal but became larger in number stop people talking about it much.
This tale of heat pump water heaters stopping a dam is rubbish. Where is the mathematics?
Heat pumps are awesome however, go to Technology Connections, not this to learn about them - https://www.youtube.com/watch?v=7J52mDjZzto
1. heat pumps rather than resistance heating: move the heat where you want it instead of creating it from scratch.
2. timeshifting electrical load. Figure out how to add and shed it on demand.
The second one has a remarkable property. Load can be shed much more quickly than spinning up peak-load generators. That means grid operators can, in periods of overload, keep the grid's AC frequency (50 or 60Hz) from dropping. Without load shedding it's done with expensive and dirty peak-load generators. That's called "frequency control ancillary services" (FC/AS) in the grid biz, and it's economically important: regional grids don't work properly unless their local grids all run at the same frequency. Local grids don't want to be disconnected from regional grids in peak-load times because their generators slowed from 60Hz to 59.8Hz. Remotely switching off a mess of hot water heaters is a GREAT way to change the grid load quickly if that starts to happen.
FC/AS is a major driver of the big Australian battery projects (built with parts from Tesla). https://www.greentechmedia.com/articles/read/australia-picks...
Who is the Van Jacobson (TCP designer who dreamed up slow-start / exponential backoff) of smart grids? Is it somebody reading HN?
The Aluminum smelting is done on hydro not geothermal.
Iceland is small compared to the USA or Indonesia for geothermal power. Large per capita, but Mexico has more geothermal power.
https://www.thinkgeoenergy.com/the-top-10-geothermal-countri...
(Iceland also has geothermal heating for housing which works well)
https://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_proc...
[0] https://en.wikipedia.org/wiki/Phase-change_material#Common_P...
EDIT: it was the enertia house
Refrigerate water at night, use it during day heat. I see that many groceries use this technique; homes could, too.
From a bit of quick searching, EV battery packs are roughly the same volume as a fridge, and weigh in around 300kg (that was a Nissan Leaf specifically, but I assume others are similar). I don't have enough room for a fridge sized battery in my house. It'd be nice if they could shrink a bit. With enough capacity to run a tankless water heater for the duration of a nice, hot shower. The battery can charge slowly whenever power is abundant.
The grid doesn't care about running a bunch of laptops. But a bunch of tankless water heaters quickly add up. Having a local buffer really makes sense there.
The US National Electric Code (NEC) has been updated (§625) so that electric vehicle charging can be used as a source of power (PDF):
* http://mydocs.epri.com/docs/publicmeetingmaterials/1112/PDNN...
Agreed. That’s why you‘ll get adequately paid for the energy sucked out of the battery in the evening when everybody starts cooking and energy prices on the market spike.
The big problem we have right now is that we want to get rid of coal and gas, but they are currently absolutely necessary for serving peaks occurring when wind power and solar lie flat. Vehicle2grid could be the solution - a giant distributed battery. I think if you charge 40kWh in the day with cheap solar, and sell it for 5x the price in the evening or morning, that would more than offset the battery degradation (which is way less of a problem than initially suspected, especially when charging and discharging slowly). A big battery could make you a couple of bucks every day.
We don’t use electricity for heating (heating and warm water are powered by community heat), and need 11kWh per day on average, excluding the EV. The EV adds another 5.5kWh per day.
Tankless water heaters are pretty efficient, but when you need hot water, you briefly use huge amounts of energy. It's for this reason that they almost always use natural gas. Electric tankless heaters are a great way to cause brownouts. They're roughly the size of a microwave oven, so they can fit in pretty much any kind of dwelling.
Water heaters with tanks, on the other hand, take up huge amounts of space and require frequent (but lower) energy input. This can use heat from a variety of sources, including low quality/unrealiable heat sources like solar heat pipes.
Then there's space heating. Unless you live in a Passivhaus, keeping a comfortable indoor temperature is challenging. Central heating using hot water and radiators is the most common approach where I live. But this again relies on burning hydrocarbons. Or, increasingly, on heat pumps, which require a lot of space, are noisy, and drop in efficiency as the temperature drops.
As far as I can tell, there are no silver bullets in either space heating or water heating. If you have a really big house, a big tank is probably a good solution for hot water. But living in a really big house is horribly inefficient in its own way. So I'm guessing that's not the greener approach. Living in a smaller dwelling is more efficient. But it seems there are basically zero good ways to heat small living spaces and hot water for a family of 1-2 living in small houses.
Propane water tanks are pretty bulletproof. Even with bad water they just truck, and require no electricity to operate, unlike some other gas appliances.
Usually you operate them until they break (maybe around 10 years), then get a replacement heater for like 400 €.
[1] https://www.stiebel-eltron.co.uk/en/products-solutions/dhw/i...
You can do the same thing with the HVAC system. For example, when the sun is high and electricity is cheap, have the A/C cooling a large mass of stone or concrete. Then, blow air over it at night to keep the house cool.
It's used to create zero-net-energy homes in Fairbanks, Alaska.
https://www.greenbuildingadvisor.com/article/a-passivhaus-de...
http://www.esterlibrary.org/programs/lectures/chluppp4-20-20...
(The videos are the best resource. They're very long, up to 2+ hours, but also incredibly detailed.)
You'd be surprised at the resistance to the idea it always engendered.
However, even if hot-water heaters aren't where it's at, I think circadian thermal energy storage is a pretty big deal for demand response, and demand response is pretty important for the renewables transition—though not as essential as many claim. There's thermal-mass energy storage like the hot-water heater approach (and Trombe walls, and earth-berm walls, and several other possibilities), but phase-change storage like the ice-battery approach mentioned in https://news.ycombinator.com/item?id=27757018 allow an order of magnitude higher energy storage density and easier temperature control, and "thermochemical energy storage" (generally through reversible hydration of desiccants such as CaCl₂) potentially allows another order of magnitude density improvement over phase-change materials, as well as offering the possibility of thermally-driven air conditioning, humidification, and dehumidification, as well as greater controllability.
I wrote extensive notes on this in https://dercuano.github.io/topics/thermodynamics.html (especially https://dercuano.github.io/notes/big-if-true.html#addtoc_8 and https://dercuano.github.io/notes/household-thermal-stores.ht...) and also Derctuo and Dernocua.
The water will get up to 80c on a sunny day, so it can store enough heat to last a couple days without sun. There is a mixing valve so the water coming out of the tank is mixed with cold to stay below 50C for safety.
But I'm curious about your case: why not use the old-fashioned solar water panels to create hot water directly?
My non-grid connected solar cost about $1200, and was easy to DIY. No $1000 permit needed since it is not connected to the grid. No moving parts and almost no electronics. House now uses only 8-12 kWh a day.
A less-sophisticated approach is to put your tank heater on a timer. Think carefully before you do this. Does your tank heater have the capacity to keep the water hot for a full shower, until you’re back under the non-peak schedule? If it doesn’t, you’ll be the first to hear about it.
Do not do this without understanding the lifecycle of legionella pneumophila, or you will face a dramatic decrease in your quality of life.
Greek public health announcement regarding outbreaks ~2018: https://www.acg.edu/about-acg/institute-of-public-health/fac...
An anecdotal account of a man contracting Legionnaire's while on holiday in Greek apartment: https://www.irwinmitchell.com/news-and-insights/newsandmedia...
An older account of a similar ocurrance in a hotel, just as you describe: https://www.sciencedirect.com/science/article/abs/pii/004313...
Granted, no mention of this particular cultural artifact. Global temperature warming was cited in some reports as part of the cause of these outbreaks. It seems that the bacteria really likes to live in showerheads, so especially older shower heads can accumulate legionella especially given commonly lukewarm temperatures. This creates a perfect storm of ideal reservoirs, protected, moist, temperature conditions and aerosolized distribution.
Nasty.
Tankless heaters are great if you’re burning gas, but electric versions are wildly inefficient versus a heat pump and require very large circuits and service entrances on the load center/breaker panel.
This is literally the first time I'm hearing of this as a concern. Our local recommendations are to keep tank temperature above 70C and you should be fine.
Classic tanked electric is so cheap to make & operate, I have come to think they may always be with us. (Though certainly a heat pump water heater is an easy choice in the right climate)
None of this applies if the water heater is not in a conditioned space, but that's not feasible in (common) environments with cold winters.
The up-front cost of a heat pump is definitely an issue. IMO we should be doing instant rebates to even out the cost between the two so that it's an easy decision.
I urge great caution, although I'd wager you'd be fine, so long as you remain healthy.
If you do the "bare minimum 140f once a day" method, you have to flush all the hot lines with this for long enough to kill it.
All this also presumes correct thermostatic calibration and generally even temperature distribution in a system planned to age with minimal maintenance.
The process isn't instant, you also have to ensure the hot water hits all the lines down the way at the appropriate hold temp and, well, hold it there for long enough.
These outbreaks still occur today. Not a huge problem, but why design such a well controlled hazard back into your potable water?
Where I am, you’re not allowed to deliver water to fixtures higher than 49C (120F), to reduce scalding risk. and this is usually accomplished through a mixing valve at the hot water tank outlet.
11m people live here, haven’t heard of any evidence of increased legionnaires:
All that other stuff assumes a minmax hot cycle in a waterheater tank.
On demand heaters work fine too.
When I replaced my water heater, I went with the hybrid model and dropped the AC. The room stays cool, my water heater uses less power on average and I don't have to fire up the ac unit at all.
Alternatively a tankless water heater provides both redundancy and instantly hot water.
I’ve been intending to do solar water heating, and convert from gas to electric, but the old heater gave out at the wrong time. So the current plan is build the solar and make a new place to move the electric tank into, then use the other tank for extra storage of the solar heated water. The good news about climate change is that I never have to worry about the pipes freezing any more.
As they recently learned in Texas.
The only saving grace at the coasts is that you’re sitting beside a giant heatsink.
So maybe plan accordingly just in case....
Issues: Building inspectors do not like it because it is non-standard. Copper is attacked by wet chlorine so you have to use stainless heat exchangers and plastic pipe. Pool filter must be constantly maintained to ensure the AC does not get clogged. If the pool is small, it can become very warm in august, almost like a hot tub.
Energy efficiency/load redirection is not the same as energy storage.
Heat pumps water heaters, with good insulation is about 3-3.8 times more efficient than straight electric heating. However keeping hot water hanging around isn't all that efficient.
With (grid sourced) electricity as the only energy source for the heat - and in absence of a "smart grid" - storing hot water adds losses, compared to heating the water just in time. So I can understand why they might think about some sort of ban.
If they go for a ban, I'd expect them to add some conditions.
Sorry.
So much in the energy field is like a stopped clock.
Can we really manufacturer that many hot water tanks in less time than building a damn?
But with the water heater solution, every time a water heater is replaced, we get the partial benefits immediately.
Manufacturing hot water tanks is trivial and highly parallelized.
Thousands of manufacturers for parts, all of whom can contribute to the demand.
That 10% is 1 million out of 10 million.
I guess the lead time on water heaters is short enough to hand wave a yes.
In the summer they are removing heat from a hot house, great - free air conditioning.
In the winter they are removing heat from a warm house, which then needs to be replaced by some other heating source to keep the house warm, great - you get to pay twice.
I tried turning the heat pump element on my heater off during the winter. However, it is programmed to automatically turn on again after 5 days.
That heat in the hot water is coming from somewhere, and you're paying for it regardless of where it came from. The question is _how much_ you're paying.
The magic of heat pumps is that in many cases, they can move X joules of heat by expending less than X joules of electricity. As an extra bonus, in the winter, any "waste heat" from the heat pump doing its work is still inside your home and not wasted at all.
So you could view a heat pump water heater as a way of converting one type of heating cost (the fuel/electricity used in a conventional tanked hot water heater) into another type of heating cost (the fuel/electricity used to heat your home).
As long as the cost of the electricity used by the heat pump is not astronomically higher than the cost of whatever is heating your home, it should definitely be in the green.
edit to add: Many state and local governments along with utilities are offering incentives/rebates/discounts to install heat-pump hot water heaters.