Geothermal. . . Heat from the Earth
By Al Taylor
Imagine that all you had to do is plug into a receptacle in the ground for all your heating & cooling needs.
Essentially, you can do that with a geothermal system.
We all want to reduce our carbon footprint and one way is to tap into the ground right under our feet and enjoy year-round heating and cooling from the earth itself.
So, how does it work?
In the winter, a geothermal system extracts heat from the earth. This is done through a highly efficient, self-contained system that produces no carbon emissions on-site. (Of course, since the system requires electricity to run, the total carbon footprint depends upon the manner of generation of that electricity.) The system consists of a geothermal unit inside your home, about the size of a regular home furnace, and a series of pipes buried underground on your property, which circulate an anti-freeze solution which acquires heat from the ground during the winter heating season and loses heat into the ground during the summer cooling season.
Heat in the ground is actually stored energy from the sun. At six feet below the surface, the earth’s temperature is a constant 10 – 15 C (40-60 F) all year round. This latent energy is a steady heat source, even during the coldest winter.
In the summer the process is reversed, once again taking advantage of the differential between air temperature and ground temperature, to cool the liquid flowing through the buried pipes. Now the heat-exchanger in the geothermal unit produces cool air to circulate through your home, instead of winter’s heated air.
Geothermal systems promise substantial savings over the long term as compared to such traditional sources of energy as oil, electric resistance, natural gas, or propane. Annual heating bills could be as much as 50 to 80% lower, depending on the system that is replaced.
Geothermal energy is not subject to rising costs or unpredictable price swings, and is not transported over long distances. It is always available, right beneath your feet!
The typical system costs between $20 – $27,000. Provincial and Federal rebates reduce that by $7 – $8000. The payback period depends upon the savings generated by the elimination of your current energy source of gas, oil, or electricity.
Electricity is still required to run geothermal, both for the pumps that circulate fluid through the in-ground pipes and for the fan that distributes heated or cooled air through your home. However, a geothermal system delivers about 3 units of heat energy for every one unit of electrical energy consumed, accounting for their legendary efficiency… and they are surprisingly quiet if properly installed.
Geothermal units last about 20 years, the loop systems of in-ground pipes last indefinitely.
The trick is to correctly size your loop field. Typically, two trenches 150’ x 5’ are dug, so you need at least an acre of land for a lateral loop system. Smaller properties may be able to take advantage of a vertical loop system: with the buried piping going straight down into the ground, like a water well.
In some instances, a body of water, such as a pond or lake, can be used to provide the necessary temperature differential versus ambient air temperature, instead of the ground.
Typically, the contractor conducts a heat loss study, followed by a cost analysis, then matches the heating requirements to the field size. Consider the loop system like a battery that supplies your home: too small and it won’t do the job; too big, and you are paying for redundant capacity.
• Although relatively cool on the surface, the deeper one goes, the warmer the ground becomes on average by 3° Celsius per 100 metres (with temperatures at the centre of the earth reaching several thousand degrees – although we haven’t heard of any local contractors going quite that deep!)
• The first geothermal power plant was started in 1904 in Larderello, Italy. It is still in operation today.
• In 1960, the Geysers in California were developed to generate electricity and currently produce approximately 5% of California’s power supply.
• Geothermal energy can be used to provide both electricity and heat.
• Geothermal energy is reliable, clean, and renewable.
• When compared to other types of power plants, geothermal power plants have a very small footprint on the local area in which they are situated.
• Geothermal electricity plants provide a steady source of power, operating more than 95% of the year.
• Iceland generates 17% of its electricity, and 87% of its heating from geothermal energy.
• Geothermal energy is used in more than 20 countries to generate electricity, including Iceland, USA, Japan, Italy, Indonesia, New Zealand, Mexico, the Philippines, Kenya, Costa Rica, and Nicaragua.