We hear a lot these days about clean energy. So I thought I'd address the subject of geothermal heating and cooling. This isn't a new energy source, but one that isn't mentioned as much as solar and wind power. With all its benefits, it really should be considered when trying to find cleaner ways to heat and cool homes, businesses and public buildings.
What is geothermal energy?
In its simplest definition, geothermal energy is a form of energy obtained from within the Earth, originating in its core and produced by extracting the Earth's internal heat. How far into the ground the energy is obtained varies from quite close to the surface to miles underground, depending on the application.
How does geothermal energy work?
According to the Environmental Protection Agency, the constant temperature of the Earth creates underground sources of heat, hot water and steam, which become the fuel to produce geothermal energy. The agency says, "People have used various forms of geothermal energy for hundreds of years; modern technology accesses these underground reservoirs, steam deposits and hot air by drilling, and then using the heat or hot water directly or using it to create power. Geothermal energy represents an enormous, under-used power source that provides clean, renewable energy in virtually unlimited supply."
How is geothermal energy used?
Some applications of geothermal energy use the Earth's temperatures near the surface, while others require drilling miles into the Earth. According to the U.S. Department of Energy, the three main uses of geothermal energy are:
1. Direct use and district heating systems, which use hot water from springs or reservoirs near the surface.
2. Electricity generation power plants require water or steam at a very high temperature (300 to 700 degrees). Geothermal power plants are generally built where geothermal reservoirs are located within a mile or two of the surface.
3. Geothermal heat pumps use stable ground or water temperatures near the Earth's surface to control building temperatures above ground.
Where is geothermal energy being used?
The world's largest district heating system is in Reykjavik, Iceland. Since it started using geothermal energy as its main source of heat, the once-polluted Reykjavik has become one of the cleanest cities in the world, reports the Geothermal Education Office. Applying the principles of piping hot water near the Earth's surface directly into buildings for heat, the Department of Energy says 95 percent of the buildings in Reykjavik are heated by the district heating system. As of the early 1990s, more than half the country's population was supplied geothermal water by geothermal heating, according to the Reykjavik Heating & Electricity Plan.
While the U.S. generates more geothermal electricity than any other country, the Department of Energy says it represents less than .5 percent of electricity produced in the country. Only four states have geothermal power plants: California has 35 plants producing almost 90 percent of the nation's geothermal electricity, Nevada has 17, and Hawaii and Utah each have one.
"Ground source heating and cooling can be done almost anywhere in the U.S. using a geothermal heat pump, a highly efficient renewable energy technology that takes advantage of the constant temperature of the Earth beneath the surface," says the Environmental Protection Agency. "The heat pump transfers heat stored in the Earth or in ground water into a building during the winter, and transfers it out of the building and back into the ground during the summer. In other words, the ground acts as a heat source in winter and a heat sink in summer. Applications of this technology are for space heating and cooling, and hot water."
Hydrothermal resources (reservoirs of steam or hot water) are available primarily in the western states, Alaska, and Hawaii. The Department of Energy says other universally available geothermal resources — hot dry rock and magma, for example — are awaiting further technology development.
What are some of the benefits of geothermal energy?
Because geothermal energy can be accessed at all times, the availability is constant, unlike wind or solar power, which is dependent on the weather on any given day. It's clean; because fuel is not burned to make steam to move turbines (as in wind power), emissions are low. It's homegrown; it can be accessed on U.S. soil, so it doesn't depend on relations with oil-producing countries and doesn't have to be shipped here.
According to the Geothermal Education Office, geothermal energy is "easy on the land. The land area required for geothermal power plants is smaller per megawatt than for almost every other type of power plant. Geothermal installations don't require damming of rivers or harvesting of forests — and there are no mine shafts, tunnels, open pits, waste heaps or oil spills." It's also flexible. The Department of Energy says plants can have modular designs, with additional units installed in increments when needed to fit growing demand for electricity.
Geothermal energy is clean, available and here. It can be used on a small scale in a single-family home and on larger scales to power entire cities. It's time to look into this virtually untapped resource and really step up our game to become a truly green country.
Anyone interested in installing a geothermal energy system should do some careful planning to ensure they install the best system for their property and for their dwelling. Look for a good company that will not only do the job right, but at the right price.
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Bill Goss is the owner of Quality Systems Consulting Group in Amesbury. His Web site is www.merrimackvalleygreen.com. If you have any questions regarding Going Green, send them to merrimackvalleygreen@comcast.net, and he will answer them in upcoming columns.
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