Dear A Moment of Science,

I know that renewable energy sources such as wind and solar power are cleaner and more environmentally friendly than fossil fuels. But as I understand it, one problem is that you can't store wind or sun like you can oil or coal. Or can you?

Storing Energy

No. There's no way to literally capture and store wind or sunlight in the same way that we stockpile coal, oil, and natural gas. When it's not windy outside, wind turbines don't generate electricity. And on cloudy days and at night, solar power plants are basically powerless.

But that doesn't mean that there's no way to capture and store energy made using wind and sun. In fact, a few power plants use cheap, off peak electricity generated at night to pump compressed air into giant underground caverns.

Then during the day, when electricity is more expensive, the air is released, heated to make it expand, and used to run turbines to generate electricity.

Renewable Energy

The process isn't necessarily tied to renewable energy. But it may turn out to be especially useful for intermittent power sources like wind. When the wind blows at night but there's little demand for the electricity generated by a wind farm, the power can be used to run pumps that force air underground.

During the day, when there's little wind, the stored air can be released to generate power. Geologists say that large, underground caverns are common enough around the world so that compressed air can be stored at many power plants.

So with the right incentives, compressed air could help solve renewable energy's energy storage problem.