Comment by pfdietz
21 hours ago
Diurnal storage is solved by batteries. Longer term storage will very likely be solved. For several days, cheaper batteries (perhaps with lower specific power). For longer periods, either thermal storage or e-fuels.
21 hours ago
Diurnal storage is solved by batteries. Longer term storage will very likely be solved. For several days, cheaper batteries (perhaps with lower specific power). For longer periods, either thermal storage or e-fuels.
My guess is seasonal will be handled with flow batteries. A big tank and cheap-ish electrolyte, with the expense being in the electrodes sized for whatever max power is required. Tanks good for multiple cubic meters worth of liquid storage aren't exactly difficult to find, nor to place in a garden.
Then again, I'm basing this opinion on a recent-ish video from NightHawkInLight: https://www.youtube.com/watch?v=eq7fR9ISuCw
Flow batteries might be ok for a week or so, but their market window has been shrinking as Li-ion has gotten cheaper.
The technology I'm most excited about is ultra low capex thermal, as being done by Standard Thermal. Capital cost per unit of energy storage capacity as low as $0.10/kWh(th), so it can work with seasonal storage and just a few tens of charge/discharge cycles over its lifespan.
Standard Thermal has raised $11M and is building in Germany, where they say they can deliver 365/7/24 solar resistive heat (400 C or perhaps 600 C) for half the cost of heat from burning natural gas there.
Flow batteries keep coming up again and again, but they just don't work well in practice. The power density of electrodes is too low to be practical, and this is a fundamental problem.
A regular 18650 cell has about 0.1 square meters of electrode surface. And you have thousands of these cells in a car battery, resulting in literal football fields of electrode area.
Wood burning heat is perfect compliment to solar in remote areas.
Agreed, e-fuels seem to be far and ahead the front-runner.
We can get to 95% using just short term storage. I suspect that most jurisdictions will just say "95% is good enough" rather than paying for ridiculously expensive long term storage.
We've got the nat gas capability already; keeping it around for the 5% is quite inexpensive, making the massive investment in long term storage for marginal benefit hard to justify.
OTOH, while the premium for e-fuels seems excessive, if you're only running that nat gas plant 2 days a year that premium is not so scary.
> Agreed, e-fuels seem to be far and ahead the front-runner.
For covering Dunkelflauten? Yes.
For seasonal storage with a prolonged discharge (so, low power/storage capacity ratio)? I think thermal storage wins there.
Sure, thermal is great where it's possible. But there aren't that many places where district heating is viable.
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I just don't see it with thermal. You have to pay the Carnot tax, and you also need humongous amounts of material.
E.g. 100 GWh (4 days of 1GW thermal power) with a 100C temperature swing (you can't go down all the way to room temperature) will need around 3.6*10^4 tons of sand. That's a lot.
Honestly, power-to-gas sounds like the only reasonable way for now. In theory, with SOFC (Solid Oxide Fuel Cells) for power generation, it can beat the steam cycle.
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