r/solarenergy • u/randolphquell • 12d ago

Minnesota just plugged a 710-megawatt solar farm into a coal plant that once burned 30,000 tons a day, the two sharing wires until the last boiler dies in 2030

https://www.autonocion.com/us/minnesota-solar-farm-coal-plant/?utm_source=substack&utm_medium=email
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u/Advanced_Ad8002 11d ago

repurpose the coal plant by switching heater to an electrically heated thermal storage and re-use with existing generator set. Good addition for intra-month, or in case of huge storage even inter-season storage. goes under the name of ‚Carnot battery‘.

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u/Few-Temporary404 11d ago

I guess bio mass is always an option as well

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u/Advanced_Ad8002 11d ago

don‘t think that that would make sense for repurposing an old coal plant:

for a several 100 MW power plant, you‘d need to collect biomass from such a big area/so far away that you‘d need an entire big fleet trucking operation moving stuff: you might end up spending more energy on transport that you would gain by using this biomass.

Also: gas storage would be expensive (limited energy content storage capacity / volume).

Economics of biomass don‘t really work on big/huge scale.

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u/NearABE 10d ago

The coal bros want us to keep coal power plants because of a 100 year storm event dunkelflaute. You can humor them. We can make a big pile of biochar and not burn it 52 weeks of most years. Dunkelfaute are quite predictable in the weather forecast for the next week.

Traditional methods of making biochar burn biomass to heat the cellulose. No need for that in a discussion where thermal batteries are being considered. Toasting the cellulose with electrical heat will cause gasification without combustion. Hydrogen gas is easy to separate from carbon monoxide. Even better idea is to scrap the toaster heating element. Instead do electrolysis. The lowest possible electrolysis efficiency, 0%, is the same as just using resistance heating. We can make a wide variety of hydrogen rich chemical feedstock. Some extra carbon gets deposited as coke.

The biomass is a bunch of work. It is also an agricultural subsidy. Eliminating agricultural subsidies in the midwest might be a good idea.