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Underwater Pumped-Storage Hydroelectric Project Completes Its First Practical Test (forschung-energiespeicher.info)
What if you built massive concrete spheres -- 98 feet in diameter, with 10-foot walls -- under the ocean to help generate electricity during peak periods? Slashdot reader nachtkap reports that German researchers just finished testing their 1:10-scale prototype StEnSEA:
It was retrieved from Lake Constance, where it was submerged at a depth of 100 meters [328-feet] since November. The system was developed by the Fraunhofer-Institut IWES in Kassel, Germany in collaboration with its inventors... The German Trade Department and Department of Education and Research as well as the German construction company Hochtief are also involved with the project.
The system's hollow concrete spheres are intended to be used in conjunction with off-shore wind-farms to serve as energy storage for peak hours. The spheres are ultimately supposed to be submerged near off-shore wind-farms and pumped free of water with excess energy. When additional energy is needed during peak hours the system goes into reverse and water rushes in, driving a turbine... At 700 meters the system has a capacity of 20MWh, with a linear capacity increase as depth increases.
The system's hollow concrete spheres are intended to be used in conjunction with off-shore wind-farms to serve as energy storage for peak hours. The spheres are ultimately supposed to be submerged near off-shore wind-farms and pumped free of water with excess energy. When additional energy is needed during peak hours the system goes into reverse and water rushes in, driving a turbine... At 700 meters the system has a capacity of 20MWh, with a linear capacity increase as depth increases.
Sounds like that would create more moving parts in an environment that's not kind to them.
First, that pressure is extremely important. As per Mythbusters episode, it can take a human and crush it inside an underwater pressurized suit when the suit breaks.
More important, water pumped up hill has multiple issues you are not considering. Evaporation, rain, land use areas, pollution, danger of dams breaking, are all major issues.
But the most important issue is simple power transmission is expensive. We lose more power moving it around than you would believe.
If you are inland, with natural hills, then pumping water up hill makes sense.
But if you are near a shore line, where beach front property is prime real estate, then finding a way to store energy OFFSHORE makes a lot more sense, as all the land near the ocean is to valuable.
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