Much like solar energy, geothermal energy is sustainable, non-polluting, and available all over the world. Geothermal energy has advantages over other green solutions like solar and wind power, though, because the energy is 'direct-use'. Since the energy doesn't have to be converted to some other form, like electricity, the usage is more efficient, sustainable and eco-friendly. Geothermal energy comes from the heat stored within the Earth's mantle - a layer of superheated rock nearly 2,000 miles thick. The heat from this mantle radiates outward through the planet's thin crust, and can be easily detected in volcanic regions or where thermal springs are found.
Humans have taken advantage of geothermal energy since time immemorial, through structures as simple as root cellars. Root cellars were used to store food and vegetables, since the temperatures there never fell below freezing and were always cooler than the hottest days of summer. In fact, thanks to the heat rising from below the surface, soil about 8' underground in most parts of the world remain a steady 55 degrees Fahrenheit - perfect root cellar weather. Accessing this well of warmth can be as simple as laying lengths of 6" pipes underground and pumping air through them. The air is cold at the start of the pipeway and has warmed up by the time it exits.
