Theoretically, there's easily enough wind and solar energy available to replace the 400 gigawatts of power that are currently provided by fossil fuels. But clouds roll in and winds die down — meaning we can't count on always having enough renewable energy.
That's why, according to a fascinating article in Scientific American, we need to build a giant battery that can store all the energy we need to get through all but the most extreme of lulls. They calculate that we need to be able to store about 80 gigawatts at all times to cover most shortfalls, which is four times greater than our current energy storage capabilities.
That's a difficult, though probably not impossible, task, though thankfully (or unfortunately, depending on your level of whimsy) it doesn't require building a five mile long AA battery in Nebraska just to store all the energy:
Fortunately, two types of large-scale energy storage exist that are already mature and economically feasible. These two technologies are less flashy than the ones the media usually likes to cover-they are decidedly "more Flintstones than Jetsons," as one online trade journal put it. One involves pumping water uphill, the other one involves compressing air.
A pumped-hydro facility consists of two reservoirs with a substantial drop in height between them. When there is excess electricity to go around, electric pumps move water from the lower reservoir into the upper one, thereby storing energy in the form of gravitational potential energy. When wind and solar wane or simply cannot keep up with demand, operators let water flow down and through turbines, generating electricity. In compressed-air facilities, excess electricity pumps air into underground caverns, and it is later released at high pressure to turn turbines.
The whole article, which provides a great overview of a lot of the more hidden challenges in switching over completely to renewable energy (plus 20% nuclear), is well worth checking out. The feature-length version of the post is also set to appear in the next issue of Scientific American.
Image by Luis Alves on Flickr.