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Comment by gwbas1c | Hacker News Reader

Regarding these kinds of plants that operate by burning: We don't know what "stockpiled" solar energy will be. Some people think it'll be hydrogen. Other people think we'll figure out how to generate flammable gasses like methane, propane, natural gas, ect, from sunlight.

Historically, steam turbine plants get retrofitted to run on different fuels. I think there's a good chance we'll figure out how to stockpile a flammable gas from solar energy, and then retrofit these kinds of plants to use it.

In this particular case, capturing CO2 is interesting, because stockpiling solar energy to a flammable gas may require a source of pure CO2. Thus, this plant could stockpile CO2 in the winter when sunlight is less abundant, and then stockpile fuel in the summer when sunlight is more abundant.

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Carnot efficiency limitations means the winning solution can't use burning CO2.

Batteries and hydro can both break 90% round trip efficiency while having very low costs. To win something needs to be better than that or very cheap, and burring stuff is not cheap.

Maybe, but keep in mind that batteries are expensive and energy intense to manufacture. When a battery goes through many cycles in a year, the cost and energy investment are marginal.

The problem is stockpiling. If we have a lot of solar, we will need to stockpile energy in the summer for the winter.

Buying a giant battery that charges in the summer so I can run an electric heater in the winter is probably more expensive than figuring out how to manufacture a flammable gas. If I use it for 20 years, and take into account the energy used to manufacture, I wonder what the "true" efficiency is?

It's still very affordable to heat with wood, (which captures CO2 from the air,) so I'm rather confident we can figure out how to do this at scale.

For home heating solar hot water heaters still beat buying wood pellets + stove over 10 years while lasting longer than that at least in the continental US. Wood is a larger pain to use and less efficient causing scaling issues.

Also with solar + wind their is no need for seasonal storage just have extra capacity and move it from other areas. 30-50% daily grid storage is about the useful limit above that and you're better off with more capacity.

PS: It's a different story if you say live on an island above the attic circle, but that's not a huge market.

There are many entities claiming they found some chemical process that outputs a flammable gas (or heat) and the whole process is carbon negative, somehow. But all of these claims are all vapourware, still.

I thought air-to-fuel was old school chemical engineering that nobody has figured out how to make economical. The "somehow," though, I believe is known.

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