The idea of coal mines being put to good use as a kind of “green battery” for wind power is being developed in Lower Saxony in Germany. This acceptance is surprising to someone who has lived for so long in America, where green energy has to do battle, for different reasons, with both sides. Perhaps this pragmatic approach (when coup- led with its uncomplicated embrace of green energy) is responsible for Germany’s economic growth. Variations on ideas for pumped storage are surfacing now that the world needs to integrate intermittent wind power with the grid, but Schmidt’s innovative idea would be the world’s first use of an abandoned coal mine for this purpose. Traditional pumped storage uses gravity to harness wind power. Water is pumped up a hill to a reservoir by wind power when it is available, typically at night, so that it can be released downhill when it is needed, using gravity to drive the turbines to make electricity. In this case, the pumped water would be stored inside the mountaintop, rather than on it, in a reservoir, but it would still be high enough so that gravity could be used at the bottom to drive turbines when it is released. This would be a contained loop system, so the water does not contaminate rivers at the bottom. Schmidt estimates that a pilot plant could be built in Bad Grund within the next three to five years for between 170 and 200 million euros, that would be large enough to provide up to 400 MW of storage capacity at a time, enough to power 40,000 households for a day. Each typical windy night could be “time shifted” to power the following day’s daytime needs in this way, one day at a time. Schmidt also believes that there are up to 100 other sites in Germany that could be similarly utilized, simply by adapting the no longer used infrastructure of the fossil age

Original sources: 11 09) (2013 11 09)

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