There's nothing new about drilling for energy. But there is a fresh approach to what we're drilling for - and how deep.

According to Jefferson Tester, there's enough recoverable heat energy in the hard rocks below the U.S. for 2,000-year's worth of electricity use at current rates. Tester's research focuses on Enhanced Geothermal Systems, or EGS. Here's how it works. They drill two holes about nine miles into the earth's crust. High-pressure cold water is injected down the first hole to the hot rock, which heats the water so it returns as steam through the second hole. This steam turns turbines that create electricity.

The US already generates more electric power through geothermal energy than any other country. There are 64 geothermal power plants in seven states, producing enough energy to power over one million homes.

And there are plenty of reasons to look into it. Since EGS requires no carbon-based fuel, it has nearly zero emissions. And the heat from the earth won't die out anytime soon.