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Post by David B. Benson on Mar 9, 2023 8:15:30 GMT 9.5
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Post by cyrilr on Mar 10, 2023 23:41:03 GMT 9.5
Pumped hydro in the desert? Where will they get the water? Huge problems already with Colorado water suppy & water rights.
Perhaps they can bring in seawater or contaminated waste waters.
In any case these are not long duration projects... high turnover is needed for economics and there are limits (geotechnical and economical) to the size of the upper reservoir.
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Post by David B. Benson on Mar 11, 2023 3:25:11 GMT 9.5
Pumped hydro in the desert? Where will they get the water? Huge problems already with Colorado water suppy & water rights. Perhaps they can bring in seawater or contaminated waste waters. In any case these are not long duration projects... high turnover is needed for economics and there are limits (geotechnical and economical) to the size of the upper reservoir. From the picture given in the first link we see that the lower reservoir of the proposed pumped hydro system in Wyoming is an existing reservoir behind a dam. As for the Nevada project, en.wikipedia.org/wiki/White_Pine_County,_Nevada even has lakes in its limber pine forests and water is no problem. I agree that these projects are not ‘long term’ storage, likely intended for daily load balancing. Edited to add cleantechnica.com/2023/03/09/massive-energy-storage-projects-planned-for-nevada-wyoming/points out that the Nevada project will use water (previously) reserved for a coal-fired power plant.
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Post by cyrilr on Mar 20, 2023 0:12:27 GMT 9.5
www.ecovat.eu/These guys over here want to store hot water in big underground tanks on seasonal scale. Simple and low visual and environmental impact. They claim it is cheap but their own estimates suggest prices in the ballpark of 20000 euros per household. That is very expensive by any comparison. A gas boiler is 2000 euros installed. They probably have to scale the tank up. A lot. To get cost down.
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Post by David B. Benson on Jul 19, 2023 7:41:25 GMT 9.5
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Post by David B. Benson on Aug 4, 2023 8:04:27 GMT 9.5
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Post by cyrilr on Aug 10, 2023 19:52:54 GMT 9.5
Could be useful for small remote energy storage apps. This material is too expensive for large scale energy storage. Gotta think rock, gravel, sand level of cheapness to compete. Or really cheap salts like common chlorides and nitrides. I’m analyzing a thermocline system of solar salt (nano3-kno3 eutectic) in a cheap excavated pit with cheap quarzite rock and sand as filler. It is coming in at about 2 cents per kwh levelized cost. Very promising.
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Post by cyrilr on Aug 14, 2023 18:45:31 GMT 9.5
Pumping water up a hill is a fairly cheap and simple method of bulk energy storage. Unfortunately the needed geology and topology for this makes it rather limited on the global energyscape. Pumping air instead of water is clearly much less limiting. Everyone has air. Of course, storing air in large pressure vessels on the surface is an economic non-starter, but it is easy to excavate or solution-mine large underground caverns. Problem with air is that it's compressible. Pumping it results in wasteful heat generation, and the machinery has to operate across a wide pressure range, meaning off-design points. Existing plants such as at Huntorf and Mcintosh simply dump the compression heat, and provide expander heating by burning natural gas, which is inefficient and generates CO2 emissions. Canadian company hydrostor has fixed the problem by regenerating the produced heat in a thermal store, and using a water pond and compensating column to operate isobarically. www.hydrostor.ca/They claim it is very cheap. Though they use excavated caverns which are more expensive, and their thermal store seems expensive too. (spherical storage tanks are not economical). So I'm not really buying their claims. A solution-mined salt cavern would be a lot cheaper. Large salt formations are common enough. The brine created from solution mining could be used for the water compensating pond. Brine is denser than water, so the operating pressure is increased accordingly. For the thermal store, would it be possible to increase the number of stages so as to allow cheap hot water storage (<100C)? Pit thermal energy storage (PTES) such as being used in Denmark is currently the lowest cost thermal storage option.
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Post by cyrilr on Aug 14, 2023 18:45:57 GMT 9.5
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Post by cyrilr on Aug 30, 2023 2:01:10 GMT 9.5
I looked at using GE7FB gas turbine to see how many stages would be needed.
We'll need 5 stages of compressors and expanders.
Ballpark figures. After each stage of compressor there would be a plate HX to cool the air temperature from 100C to 20C. Cooling is regenerative to the water pond, which is heated from 15C to 95C.
Likewise the 5 stages of expanders would first take the hot water to heat the air back up to 90C, before it is expanded to 10C.
actual temperatures would be a few degrees off as air heat capacity increases slightly towards the 18 bar operating pressure and there'd be slight pressure loss in the HXs. Plus there'd be more loss on the inlet/outlet. On the other hand the efficiency of the turbines and expanders is better with smaller pressure ratios.
Higher pressure would just mean more stages and HXs. A single thermal store can be used.
Someone needs to run a gatecycle model or some such to check this further. It seems quite promising.
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Post by cyrilr on Nov 4, 2023 2:42:31 GMT 9.5
Some funky company claiming to have a great idea in high temperature thermal storage. silbat.com/The big idea being to melt silicon metal for energy storage and recover it via thermophotovoltaics. This doesn't make much sense to me. According to this: www.nature.com/articles/s41586-022-04473-yTPV at the relevant temperature has an efficiency of around 1/3. So 3 kWh in and only 1 kWh comes out. That's terrible. Perhaps for a small application, the use of TPV would make sense, but for a large application it is obvious that a combined cycle gas turbine of sorts would produce much better efficiency. Heck you can get 50% efficiency with a state of the art steam turbine single cycle. Further, silicon metal is quite expensive. It would be better to use something cheaper like steel or cast iron. Steel melts at around 1500C. Ledeburite (cast iron eutectic) has a melting point of 1147C for something a bit less spicy; HX tubes will be required for the metal bath. SiC-SiC is probably a good option. With a combined cycle it could probably run around the 60% efficiency mark. Which isn't super great but it may pass as cheap energy storage.
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Post by David B. Benson on Dec 5, 2023 9:28:47 GMT 9.5
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Post by David B. Benson on Dec 5, 2023 9:41:47 GMT 9.5
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Post by David B. Benson on Dec 7, 2023 7:40:47 GMT 9.5
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Post by David B. Benson on Dec 8, 2023 11:37:46 GMT 9.5
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Post by David B. Benson on Dec 20, 2023 9:38:52 GMT 9.5
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Post by David B. Benson on Jan 4, 2024 4:19:25 GMT 9.5
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Post by David B. Benson on Jan 9, 2024 3:28:06 GMT 9.5
Gravity Energy Storage Systems: Transforming Defunct Mines Into Efficient Energy Producers John Nieman 2024 Jan 07 EEPower eepower.com/news/gravity-energy-storage-systems-transforming-defunct-mines-into-efficient-energy-producers/Not ‘producers’ but rather stores, please. It looks like ABB is going to do the engineering involved in these mine shaft lifts. Nothing is said about the site remediation which is at least desirable if not required for disused underground mines. As for efficiency, I opine around 70% of the energy used to hoist the weights is recoverable in the descent.
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Post by David B. Benson on Jan 13, 2024 4:17:27 GMT 9.5
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Post by David B. Benson on Mar 19, 2024 11:23:00 GMT 9.5
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