WHAT IS GEOTHERMAL POWER?
The earth was formed a long time ago (about 4.5 billion years ago). In its infancy it wasn't a very nice place to live. Mostly it consisted of a giant ball of molten rock, some noxious gas and when the sun wasn't out the bitter cold of space (no atmosphere yet).
But a long time later we have this nice crust with all the little plants and animals on it. But deep below the ground there still lives that old ball of fire. The center of the earth is HOT, 5000-7000 degrees C. Fortunately for us, the center of the earth makes our planet volcanically active. This in turn helped to form our atmosphere and allowed us all the develop.
When water seeps down into cracks in the earths crust it interacts with this hot core. This causes the lovely show at Old Faithful in Yellowstone national park, and all the nice hot springs all over the world. In other places there is just a lot of dry hot rocks below us. But either way (water heated by the earth, or hot rocks) this heat can be captured for energy. If you have lots of steam and hot water coming up out of the earth (like in Iceland) you can capture this steam and use it to create electricity. If however you live where there isn't lots of steam shooting out of the ground you can still get energy from the earth.
CAN GEOTHERMAL POWER BE USED IN THE HOME?
If you live above an aquifer (a layer of water between rock below the earth) and sink a pimp into it you can create a geothermal system for your home. The of water deep enough is just about always the same tempurature. Lets say its 50 degrees. If you pump out 50 degree water you can use it to heat your home in the winter, by using a heat exchanger to remove heat from the water.
WHAT SHOULD I KNOW ABOUT USING GEOTHERMAL?
Water taken from the source must be returned or the ground will start to collapse, but if you are careful and pump all the water back in, you can safely use geothermal systems. You also must give the water time to heat up from the earth, as you pump the water out you are removing the heat stored in the water, and pumping the cold water back in. Care must be taken to allow the water you pump back in to heat up again or else your system will not produce heat. The amount of time it takes for the water to warm again depends on the site.
CAN GEOTHERMAL POWER SYSTEMS BE USED FOR BIGGER PROJECTS?
Places like the Philippines get as much as 27% of there power from geothermal. Large scale geothermal plants have been built in many countries and on all continents except Antarctica. Iceland has been using geothermal plants for many years now, as have several sites in California. With proper sighting and usage control geothermal is an energy source that is nearly infinite.