Enough Northwest US wind energy to power about 85,000 homes each month could be stored in porous rocks deep underground for later use, according to a new study. Researchers at the Department of Energy’s Pacific Northwest National Laboratory and Bonneville Power Administration have identified two unique methods for this energy storage approach, and two eastern Washington locations to put them into practice.
The world’s two existing compressed air energy storage plants (one in Alabama, the other in Germany) use man-made salt caverns to store excess electricity. The study examined a different approach: using natural, porous rock reservoirs that are deep underground to store renewable energy. Analysis identified two particularly promising locations in eastern Washington.
One could access a nearby natural gas pipeline, making it a good fit for a conventional compressed air energy facility. The other, however, doesn’t have easy access to natural gas. So the research team devised a hybrid facility would extract geothermal heat from deep underground to power a chiller that would cool the facility’s air compressors, making them more efficient. Geothermal energy would re-heat the air as it returns to the surface.
We’ve all heard of CAES (compressed air energy storage). Normally, the expression brings grid-scale operations involving vast underground caverns to mind or, at the very least, a substantial plant such as LightSail’s headline-making design. But French automaker PSA, owner of both Peugeot and Citroen, thinks CAES can be used as a replacement for battery power in hybrid vehicles.
The proposed vehicle would have a conventional petrol engine, paired with a hydraulic motor, driven by air from a high-pressure tank and which would come into play during low speed urban driving. The first prototype is slated for 2016, with a combined economy of 117 mpg.
But this is not the first time that compressed air has been suggested for running vehicles. As an example, Tata’s MiniCAT (Compressed Air Technology) is a very lightweight car that was scheduled to flood the streets of India in the summer of 2011, then at the end of last year – and now this. It remains to be seen if France’s air-powered car will share the same fate.
Working with the energy company Hydrostor, a team at the University of Windsor, Ontario, has been testing a unique CAES system that stores compressed 50 – 500 meters below the water’s surface in high-strength polyester bags when power supply outstrips demand.
When the grid demand increases, the weight of the water itself pushes the air back to the surface where it is then run through Hydrostor’s expander/generator system to generate the required electricity.
The team has already tested scale models of their system in the university’s swimming pool, plus a full-sized system in Lake Ontario. It is hoped that a commercial system could be online by the latter part of 2013.