[danans]

4 hours is solidly in the middle of what is needed for the daily peak load management tier of the energy storage problem [1], which is how we experience electricity "reliability" on a day to day basis, and it is the upper end of what is economical for lithium ion batteries.

Beyond that, other technologies (pumped hydro, perhaps hydrogen electrolysis) are more economical.

1. https://storagewiki.epri.com/index.php/Energy_Storage_101/Te...

[ncmncm]

Tankage is much cheaper than batteries.

[danans]

Tankage for what? Tanks for things like compressed air might be cheaper, but round trip energy efficiency is much lower (50%ish) than batteries.

It will be interesting to see how sodium ion batteries will compete since their alkali metal is far more abundant than lithium, especially in stationary applications that don't need high energy/mass or energy/volume.

[ncmncm]

Tankage is for anything: Liquified ammonia (stored at environment temperature under light compression. Liquified hydrogen. Liquified nitrogen. Gaseous hydrogen, underground, where geology favors it. Maybe liquified methane or kerosene, if you can synthesize that.

Perhaps surprisingly, round-trip efficiency matters a lot less than other things, for storage not drawn down often. And, it matters a lot less everywhere than only a short time ago, because top-line generating capacity has got so cheap, you can just build out enough more of that to make up the difference. If your liquified hydrogen is slowly boiling away, you just top up your tanks now and again.

The important difference from batteries I call attention to is that in batteries, you can only store exactly as much energy as you buy expensive batteries to keep it in. But for synthetic chemicals (and liquified nitrogen), the only expensive parts are what you use to synthesize them in, and maybe the way you get the energy back. Those capacities are measured in watts. Saying tankage is cheap is to note that there is no upper limit on the amount of tankage you can have, and the watt-hours you can bank; your bottleneck is only the conversion rate.

This is all aside from the fact that tankage can be shipped, both out, generating revenue from excess generating capacity, and in, if local storage gets drawn down too far.

So, batteries will be used for short-term storage. Iron-air battery factories are under construction, and those will be much cheaper than lithium, and will be used, but however much cheaper they are than other batteries, they cannot match empty tankage.

[danans]

> Saying tankage is cheap is to note that there is no upper limit on the amount of tankage you can have, and the watt-hours you can bank; your bottleneck is only the conversion rate.

I think there are a lot of use cases for those fuels that don't even require a lot of long term storage, my current favorite being hydrogen fuel cell powered semi trucks that already burn a lot of diesel crossing places that have a lot of renewable electricity potential but not enough transmission (i.e. wind in the Great Plains and sun in the desert Southwest). This would get around the issues with batteries eating into truck weight limits.

Also, the idea of freight trucks "sailing" across the country on wind power is just an appealing narrative.

[ncmncm]

Once people get used to electrical synthesis of ammonia, those wide-open spaces will be making their own fertilizer and tractor fuel.

They might sell the excess to nearby truck stops. Ammonia is not quite as dense as diesel, but trucks typically have enough room for it. Advantage is trucks (like farm tractors) can be cheaply retrofitted to burn ammonia.

I see reports about a problem of UK farmers who make more from dedicated solar, per hectare, than they were making growing. The problem may be self-limiting: they may end up unable to compete with farmers doing double- or triple-use, with solar, wind, and cultivation in the same field. Then, farmers not doing it will end up needing to, as prices decline.

[danans]

> I see reports about a problem of UK farmers who make more from dedicated solar, per hectare, than they were making growing.

> The problem may be self-limiting: they may end up unable to compete with farmers doing double- or triple-use, with solar, wind, and cultivation in the same field.

Can you share that report?

I'd like to see a triple use farm. Great idea in concept, but I doubt that there a lot places that have a climate that makes wind, solar, and shade vegetable growth economical on the same land. Otherwise we would see this pervasively across California's Central valley.