An Introduction to Geothermal Energy

As scientists begin digging deeper into the possibilities for renewable energy, they look to the sun, the wind, and other renewable options for cleaner, greener sources. Another possibility may be right beneath our feet — geothermal energy.

In our discussions on renewable energy sources, we’ve already covered a few of the most common types of alternative energy, such as wind, solar, and bioenergy. For the next part in our series, we’ve compiled a brief introduction to and explanation of yet another form of renewable energy: geothermal.

What is Geothermal Energy?

As the name suggests (geo = earth and therme = heat), geothermal energy comes from heat produced by the Earth.

First, a brief lesson in geology: Beneath the surface (or crust) of the Earth, there are a number of heat-producing layers of rock, minerals, and magma, including the mantle, the outer core, and the inner core. The deeper you dig towards the center of the Earth, the hotter it gets. In fact, the core (about 4,000 miles beneath the surface), can reach temperatures of 7,600 degrees Fahrenheit.

This heat – which can be harnessed for energy — is caused by residual heat from the formation of the Earth, as well as decay of radioactive isotopes.

How is Geothermal Energy Harnessed?

There are several different ways of harnessing the heat of the Earth for energy. We’ve outlined a few, below.

Direct geothermal energy can be accessed in areas where hot springs/geothermal reservoirs are near the surface of the Earth. In these areas, hot water (pumped through a heat exchanger) can be directly piped in to heat homes or buildings. The “used” water is then returned to the reservoir for re-heating.

Geothermal heat pumps are another method for harnessing geothermal energy. These systems utilize a series of underground pipes, an electric compressor and a heat exchanger to absorb and transfer heat.

In the summer, the system removes heat from the house/building and returns it to the Earth. In the winter, the geothermal pump absorbs heat from the ground and transfers it into the house/building.

Geothermal power plants also harness the heat of the Earth through hot water and steam. In these plants, heat is used to generate electricity. There are three main types of geothermal power plants, including dry steam plants, flash steam plants, and binary cycle plants.

How is Geothermal Energy a Renewable Energy Source?

As discussed in our other articles, renewable energy sources – unlike fossil fuels – are virtually unlimited resources. Since the core of the Earth is so hot, and this heat permeates throughout the other layers of the planet, geothermal heat as a source of energy will not deplete. Additionally, geothermal power plants produce just a fraction of the carbon emissions of fossil fuel plants.

So, What’s the Hold-Up?

As with many types of renewable energy, the initial costs of geothermal energy installment are high. However, studies show that a residential geothermal heat pump can reduce energy bills by as much as 40%, and will likely pay for itself within 5-10 years.

Be sure to stay tuned here at Eco-Centric, as we continue our series on renewable energy in the coming weeks!

Resources:

http://www1.eere.energy.gov/geothermal/powerplants.html

http://www.consumerenergycenter.org/home/heating_cooling/geothermal.html

http://science.howstuffworks.com/environmental/energy/geothermal-energy2.htm