Geothermal Energy

Geothermal energy is heat energy from inside the earth. This energy results from radioactive decay of material deep underground, which has continued since the original formation of the earth. The movement of heat energy from underground to the surface leads to a geothermal gradient that can be exploited to meet energy needs.

Some Background...

In reviewing the history of geothermal power one learns that ancient man used hot springs for bathing and it was used for space heating as early as the Roman times. Today the more popular uses for this energy include: heating of spaces, heating of spas, certain industrial processes, and some agricultural applications.

Despite some obvious benefits of using geothermal power (i.e., no more dependence on fossil fuels), access areas are usually near tectonic plate boundaries. However recent advances in technology have led to more widespread use, especially for home heating.

The earth's supply of this heat is enough to supply man's energy needs, however only a tiny amount can be taken and still result in a profit. Drilling and exploration for this type of energy is expensive. Predictions for future use of geothermal power depends on technological advances, energy prices, and tax incentives/subsidies.

The countries with the largest geothermal capacity are the U.S., followed by the Philippines, Indonesia, and Mexico. The largest group of geothermal plants in the world is The Geysers, in California. However, the countries with the highest percentage of their total energy are: Iceland (30%), Philippines (27%), El Salvador (25%), and Costa Rica (14%). (source: Wikipedia) As eluded to earlier, geothermal plants were typically built near the edges of tectonic plates, where a natural conduit exists to transport energy from deep inside the earth to the surface. Technological advances have led to the spread of this energy source to other parts of the country and world.

Main Considerations

Typically thermal efficiency for geothermal electric plants is low - around 10-20%. This is due to the fact that fluids within the earth don't reach the necessarily high temperatures needed for steam production. However capacity can be large as compared to solar and wind, since geothermal energy is more "continuous" or uninterrupted.

Direct heating is more efficient than electricity generation for this energy. Geothermal heat pumps draw on shallow areas of ground heat using earth tubes or downhole heat exchangers. The earth's geothermal gradient averages around 80 F/mi or 30 C/km in most places, so you don't need to go too deep to draw energy.

Some Main Points to Consider:

Starting with the positives...

• cost effective

• requires no fuel (except for heat pumps)

• reliable

• sustainable for most

• environmentally friendly (as compared to using fossil fuels)

Some negatives...

• can have limited access regions

• wells release greenhouse gases trapped within earth (still less than that released from using fossil fuels)

• can be expensive for drilling and exploration

Geothermal is another source of alternative energy that deserves a closer look if you are looking at reducing your dependence on fossil fuels and doing your part to combat climate change.

See my article on geothermal energy facts More specific geothermal considerations for the homeowner are covered.