Australia's 'giant water battery'
This is the Kidston Solar Project under construction in Queensland, Australia. It will be the world's first pumped-water energy storage project built from a former gold mine. You may prefer to think of it as a "giant water battery." The project uses excess solar power to pump water from one reservoir to another at higher elevation, then harvests the energy as hydroelectricity by letting water fall back to the lower reservoir in times of need. In the image above, the two reservoirs are visible in the upper left-hand corner, while the heart-shaped structure at right will consist of over 3 million solar panels when the project reaches completion. The project is set to generate 783,000 MWh each year, enough to power more than 100,000 homes. Old-fashioned though it is, pumping water uphill is still the most cost-efficient technology available for large-scale electrical energy storage. Storage is an essential component of a renewable energy grid, so that electricity can be provided when the wind doesn't blow and the sun doesn't shine.