pastor-raised t1_irwps92 wrote
Reply to comment by FinndBors in Geothermal May Beat Batteries for Energy Storage: Enhanced geothermal systems are well suited to store excess renewable power as heat. by filosoful
What about using excess energy to pump water up a mountain and releasing the water through turbines down the mountain as power in needed. Too inefficient?
sunsparkda t1_irwzd7i wrote
That's pumped hydro storage, and it's already implemented in most of the places that have the geography for it. It's the most widely deployed power storage system at the moment.
Squirmin t1_irwr5is wrote
It looks like the biggest disadvantage to molten salt is the drop in generation efficiency. While the long term storage is fairly efficient, it loses a lot when they try to convert back to electricity. Hydro storage can lose efficiency due to evaporation, but they can still maintain 70-80% efficiency.
There's also geography that has to be taken into account for hydro, as you can't put it just anywhere.
>In a complete PHES cycle, water is pumped from a lower to an upper reservoir and at a later time returns to the lower reservoir, with a round-trip efficiency of about 80%. In other words, about 20% of the electricity is lost in a complete pumping/generation cycle.
>The topic is crucial because, at the present stage of power industry development, molten salt power plants are pioneering solutions promoted mainly in Spain and the US. Molten salt reservoirs have high storage efficiency (above 90%), but the efficiency of the energy transformation from heat to electricity is much lower at about 50%, which is a significant disadvantage.
VladVV t1_iry6tby wrote
It’s been proposed to simply use groundwater reservoirs as the lower reservoir and enable pumped hydro (almost) independently of geography. It’s only been implemented as small-scale tests, however, and the long-term consequences (if any) of repeatedly pumping water out of and back into deep underground wells are not known.
oppositetoup t1_is07k30 wrote
It's very dependent on the geography of the area. You can't just use a mountain as there's no space at the top to actually store enough water to make it worthwhile.
It also takes up A lot of space
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