[AndrewDucker]

Stores it for return as heat. Which is useful, but not nearly as useful as returning it as electricity would be.

Still, if it could be stored stably in the summer and converted to heat in the winter then possibly helpful.

I wonder how the efficiencies compare to producing hydrogen or other burnable gases.

[3eb7988a1663]

Something like 25% of global energy is dedicated to industrial heating. While not as immediately applicable as electricity, there are many uses for load shifting solar as heat.

That being said, there are some "hot rocks" companies who have been working with thermoptovoltaic cells. Which could still work, but the low hanging fruit is in the millions of direct uses for heat.

[hn_throwaway_99]

> Still, if it could be stored stably in the summer and converted to heat in the winter then possibly helpful.

There are already sand batteries that store heat well and are used in northern climates: https://polarnightenergy.com/news/worlds-largest-sand-batter...

[pfdietz]

These are too expensive for seasonal storage.

[hn_throwaway_99]

"Seasonal storage" is a problem so far out that it feels like it's not even worth worrying about until renewables are a much higher percentage of the overall energy mix. What I mean by this is that even places that (for example) have a huge abundance of solar power during the day still have to burn fossil fuels when it's nighttime or when it's cloudy - solving the "24 hour problem" will still take a lot more renewable capacity than we currently have.

And even then, we already have the ability to create synthetic fuels from electricity, so any new development would need to be competitive with what we can already do.

[pfdietz]

I disagree! It's a vital problem to solve, especially if solar becomes significantly cheaper than wind (as appears to be happening; solar has the better experience rate). And solving it punctures one of the last arguments bad-faith nuclear advocates use to argue against renewables.

I will once again point to Austin Vernon and Standard Thermal, which has an approach that could truly solve the problem. The first principles analysis of the issue shows the problem with "sand batteries" and the like.

https://www.orcasciences.com/articles/standard-thermal

"Given that heat capacities of solids are all generally similar at ~3kb per atom, we’d need to store heat in a solid that costs ~$10-30/ton or less and tolerates very high temps. But nothing built on a foundation or made in a factory is sold for less than $100/ton. There’s almost nothing that even gets shipped in the dollar per ton range."

https://www.austinvernon.site/blog/standardthermal.html

https://www.standardthermal.com/

[pfdietz]

> Still, if it could be stored stably in the summer and converted to heat in the winter then possibly helpful.

The capex per unit of stored energy in undoubtedly far too high for that to be worthwhile. Seasonal energy storage requires extremely low cost storage media.