“Pump storage power stations.” Pumping water into a mountain lake when electricity is cheap, and allowing it to drain out through power-generating turbines when electricity is more expensive, is rather efficient contemporary energy storage (“80% efficiency” for short-term storage of a few hours). Excess electricity is hard to store in quantity and tends to be sold off to neighboring countries instead, so storage issues might be one reason why Germany has quadrupled electricity exports since-and-despite closing eight nuclear power plants in 2011. A more obvious reason would seem to be the success of the Energiewende, large-scale infrastructure investments Germany is making to switch to renewable power sources such as solar and wind.
Of course villagers, fish and tourists near mountain lakes don’t appreciate constant changes in water levels. But the switch to renewable energy sources has undermined the financial benefits of draining lakes every day at lunchtime. Power prices used to peak around noon, so Germany’s >30 pump storage power stations drain their lakes through turbines during daylight hours, pumping the water back up the mountain at night. That demand-driven price spike is now being offset by the daylight collected by solar panels, which private citizens have been encouraged to install on their roofs. Utility companies are starting to not expand, not build, not renovate and shut down their lake storage power stations, as they wait for new technologies.
Next-generation electricity storage options will have to store power not only for hours but also for months, to buffer seasonal fluctuations. Small storage options that, like photovoltaics, can be installed in quantity in e.g. private houses will aid the decentralization trend. Large storage options under discussion include gas chemistry and big hollow concrete spheres lowered to high-pressure depths on the ocean floor: to store energy they would be filled with air and then allowed to refill with seawater, driving turbines.
(POOMP shpy chh ah CROFT verk ah.)