A mountain designed to store electricity<\/h2>\n\n\n\n
Think of the whole project as a big rechargeable battery<\/a> that is powered by gravity instead of lithium. When there\u2019s plenty of electricity the motor generators pump water from the Seminoe Reservoir up to a 1,000 feet higher reservoir and about 10,000 feet east of the dam, using tunnels that carry the water through granite.<\/p>\n\n\n\n When the grid needs power the same water runs downhill through 3 underground pump turbines that together have the combined capacity of 972 megawatts. FERC data says the plant could generate power output for about 10 hours, while a full recharge would take an estimated 14.6 hours.<\/p>\n\n\n\n Wyoming has abundant wind generation but that does not correlate to electricity supply-and-demand always being lined up: such strong production during quieter overnight hours can leave the grid operators exposed to excessive power that has nowhere to go since there\u2019s no demand. This forces them to reduce output or sell electricity cheaply since it would be a waste to not use it in any way.<\/p>\n\n\n\n Seminoe\u2019s job is to absorb that surplus and only release it later. That would change the picture by giving the transmission infrastructure the option to carry energy only when the energy is really needed. There\u2019s no free power though: the pumping uses more electricity than the turbines return, showing a round-trip efficiency of about 78 to 80 percent<\/a> in the estimates.<\/p>\n\n\n\n Once they start operating those 10,800 acre-feet of water would be able to be cycled between the 2 reservoirs, which means the same volume would be reused over and over. The federal project description lists an initial fill of about 13,400 acre-feet and roughly 672 acre-feet a year to replace evaporation and seepage.<\/p>\n\n\n\n The Seminoe Reservoir is listed at over 1 million acre-feet of capacity, so the initial fill equals to roughly 1.3 percent of that total on paper. The reservoir levels, drought<\/a>, downstream obligations and the timing of withdrawals will still impact the daily operations. The developers also argue that net evaporation caused by the project could be lower because water moved uphill would no longer evaporate from the lower reservoir.<\/p>\n\n\n\nRead More: A Wyoming mountain could become a 972-megawatt water battery, but the project may disturb the trout waters below Seminoe Reservoir<\/a><\/h4>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\n
![\"Close-up](\"https:\/\/www.ecoticias.com\/en\/wp-content\/uploads\/2026\/09\/seminoe-dam-closeup-wyoming.jpg\")
Why Wyoming\u2019s wind makes storage viable<\/h2>\n\n\n\n
Read More: A whale as long as a city bus can race through the ocean, but NOAA\u2019s 212 strandings reveal a hidden coastal danger<\/a><\/h4>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\n
Why the water accounting is important<\/h2>\n\n\n\n