Comment by sir_bearington | Hacker News Reader

Comment by sir_bearington | Hacker News Reader

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> Apparently you haven't done the math on this, but I did: https://dercuano.github.io/notes/lithium-supplies.html

Only 5 minutes of storage exist in known energy reserves. Only 18 minutes exist in lithium reserves accessible with current extraction techniques.

How is this supposed to be in favor of renewables? The lesson we take aware here is that demand for lithium needs to drive prices up high enough to incentivize pioneering new mining techniques such that an order-of-magnitude increase in accessible lithium reserves can be tapped.

> However, independent of the above, your assertion, "Generating another 500 MW of solar energy doesn't actually represent any decarbonization if that energy is produced when demand is already saturated," is also incorrect. Generating another 500 MW of solar energy to satisfy demand currently being satisfied by coal, oil, or gas allows us to turn off coal, oil, and especially gas plants more often, which does actually represent decarbonization.

No, no it doesn't. If you generate 10 GWh of solar during the day and 10 GWh from methane during the night, and you install an additional 10 GWh of daytime solar how much did your carbon emissions go down? Zero. How is this hard to comprehend?

> It's only during hours when 100% of demand is being satisfied by solar energy that generating another 500 MW of solar energy doesn't represent decarbonization

Which is already the case in some markets. Prophecy that once markets are saturated we'll start using storage to capture the excess is not panning out.

> How is this supposed to be in favor of renewables?

I'm a lot more "in favor of the truth" than "in favor of renewables". And the truth is that there's plenty of lithium, but not with current extraction techniques.

> No, no it doesn't. If you generate 10 GWh of solar during the day and 10 GWh from methane during the night, and you install an additional 10 GWh of daytime solar how much did your carbon emissions go down? Zero. How is this hard to comprehend?

You seem to be violently agreeing with me, while congratulating yourself on your intellectual superiority, which is terribly amusing.

Last I checked, Li-ion was about US$111/kWh https://dercuano.github.io/notes/energy-storage-efficiency.h... which is probably around US$300/kW on th current grid, depending on how many hours a day you need battery, and buyers were undervaluing storage. Given that coal and (1970s) nuclear plants cost on the order of US$1000/kW to build, this is already economically feasible. (Current nuclear plants cost close to US$7000/kW, but plausibly that's largely regulatory costs.)

So, existing lithium batteries are already cheap enough to be economic to deploy; about US$100 billion of batteries into the future, new mining techniques are needed; there's plenty of lithium in the sea to get to an all-solar grid; and existing utility incentive structures haven't yet accommodated the necessity of storage.

> I'm a lot more "in favor of the truth" than "in favor of renewables". And the truth is that there's plenty of lithium, but not with current extraction techniques..

And the truth is that I only ever said that there isn't enough grid storage available to make renewables feasible for decarbonization. The notion that I ever said there wasn't enough lithium in the earth's crust isn't the truth. Sure, there's more lithium that's inaccessible. But inaccessible lithium isn't available for use in energy storage.

> Last I checked, Li-ion was about US$111/kWh https://dercuano.github.io/notes/energy-storage-efficiency.h... which is probably around US$300/kW on th current grid, depending on how many hours a day you need battery, and buyers were undervaluing storage. Given that coal and (1970s) nuclear plants cost on the order of US$1000/kW to build, this is already economically feasible. (Current nuclear plants cost close to US$7000/kW, but plausibly that's largely regulatory costs.)

You're comparing figures on generation to storage. Yes, a big nuclear plant that generates 2.5 GW of electricity often costs $15 billion, sometimes more sometimes less (The Taishan plant only costed $7 billion for 2GW). But they generate that power for 50 to 80 years. And crucially they generate power 24/7 and don't need a supplemental form of storage.

By comparison, buying 2 gigawatt hours grants you the ability to store enough energy to output 2 GW for a duration of 1 hour. This means something totally different. You still need to add onto this the cost of building and maintaining solar panels or wind turbines or what have you to actually fill this storage.

But what's crucially omitted here is service lifetime. Good lithium ion batteries will do ~1,500 discharge cycles, exceptional ones 2,000. That's 4-6 years of service life for these batteries, especially if they're being used for diurnal storage like solar. And that's really all they're good for, batteries also lose their charge if they sit unused for long durations. so $100 for 1 KWh that needs to be replaced every 4 years really costs $2,000 over the life of 80 years.

Also actually attempting to use batteries for grid storage will cause the price of batteries to skyrocket. Globally ~300GWh of lithium ion batteries are produced annually [1]. The world uses 60TWh of electricity daily. 1 day of storage would take 200 years to provision at current production rates. Sure, battery production is growing but won't be able to keep up with demand and price will rise. As you pointed out earlier, only 20 minutes of storage are available with existing mining techniques so extraction will rapidly become a bottleneck.

1. https://energycentral.com/c/ec/world-battery-production

Thanks, this is good stuff! Just to clarify one thing:

> You're comparing figures on generation to storage. Yes, a big nuclear plant that generates 2.5 GW of electricity often costs $15 billion … buying 2 gigawatt hours grants you the ability to store enough energy to output 2 GW for a duration of 1 hour

I'm clear on the distinction between power and storage capacity; that's why I said, "Li-ion was about US$111/kWh which is probably around US$300/kW on th[sic] current grid, depending on how many hours a day you need battery" and linked to my note from 02019 about precisely how the price of batteries interacts with the price of energy, depending on how many charge/discharge cycles you get per day and how long they are.

The thing I probably should have been more explicit about is that, on the current storage grid, batteries are needed about 2–3 hours a day; US$111/kWh times two or three hours gives "around US$300/kW": to bridge those 2–3 hours of shortfall, you need 2–3 kWh/kW of batteries. That's what makes Li-ion batteries profitable to install today.

It is of course true that as the amount of solar energy in the grid increases, this duration also increases, especially if demand response doesn't materialize as we might hope. Figures from the CAISO report I linked elsethread http://www.caiso.com/Documents/Final-Root-Cause-Analysis-Mid... show that California's solar generation in the summer is roughly 12 hours a day and fairly constant during about 10 of those hours, ending just after peak demand, and that peak demand is about twice "valley demand". On the fateful day, the demand ramped down from about 45000 MW to about 25000 MW nearly linearly over the other 12 hours, so if you wanted to feed the entire California demand from expanded solar generation, you'd need to store up 420 gigawatt hours (1.5 PJ). You'd need 12 kWh of batteries per (average) kilowatt, which would bring the price of storage to above US$13000 per kW at the battery prices I found two years ago, which is slightly higher than the price of thermal power generation. Hopefully those battery prices will go lower and/or people will shift to using more power when the sun is up, for example because it's free, but those prices are already low enough to invest the first US$50 billion into ramping up battery production and new extraction technologies.

Your point about service life is well taken, but I think you probably would benefit from doing real NPV calculations, with discount rates. I'll make an effort tomorrow if I have time.

> the other 12 hours, so if you wanted to feed the entire California demand from expanded solar generation, you'd need to store up 420 gigawatt hours (1.5 PJ). You'd need 12 kWh of batteries per (average) kilowatt, which would bring the price of storage to above US$13000 per kW at the battery prices I found two years ago, which is slightly higher than the price of thermal power generation.

And you'll have to pay this cost every 4-8 years, too.

And once you talk about load shifting, you're adding in a while bunch of other invisible costs to accommodate the shifting load. E.g. making it so that trains only run at night and on windy days, that increases cost of logistics across the board, which in turn makes a whole bunch of other goods and services more expensive.

Cf. https://news.ycombinator.com/item?id=26308189.

If freight trains are what we're talking about, solar-powered freight trains might only run during the day rather than the night.

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