Pollution-free Heating and Cooling: Geothermal Heat Pumps

Mark Snyder
Minnesota Office of Environmental Assistance
November 1, 2001
What is Geothermal?

Many people, when they hear the word "geothermal", think of those old plants that were built out in Western states to generate electricity using underground reservoirs of hot water or steam. Known as "direct-use" systems, they trade off dependence on fossil fuels for impacts on the hot springs from which they draw their energy.

In recent years, newer technological advances have allowed for the development of ground source heat pumps that can provide buildings with heating in the winter and cooling in the summer, all in one unit. This means that instead of having both a furnace and an air conditioning unit for a home, only a single heat pump system is needed.

How Does it Work?

Ground source heat pumps use the earth as a heat source in the winter and a heat "sink" in the summer. Much of the upper 10 feet of the Earth's surface maintains a nearly constant temperature between 50 °F and 60 °F. A ground source heat pump consists of a closed-loop piping network buried near the building and connected to a heat exchanger and ductwork going into the building. In the winter, heat from the relatively warmer ground is pulled into the building by the heat exchanger, and in the summer, hot air from the building is pulled into the relatively cooler ground by the heat exchanger. Some heat pump systems also include a secondary heat exchanger that allows heat from summer air to be used for heating water in the hot water tank.

What Are the Benefits?

First, geothermal heat pumps tap into a clean, efficient, renewable energy source for heating and cooling the home. It replaces the furnace that burns oil or natural gas as well as the air conditioner that uses huge amounts of electricity generated from burning coal. According to the U.S. Environmental Protection Agency (EPA), geothermal heat pumps are 48% more efficient than the best gas furnaces and 75% more efficient than the best oil-burning furnaces. Geothermal energy is also "homegrown," reducing our dependence on imported oil or natural gas.

Geothermal energy is reliable and lowers utility bills. You don't have to worry about outages caused by peak power demand or price spikes caused by distribution shortages as have been seen lately with natural gas. Estimates show many households can save 25% or more on utility bills.

For folks in rural areas, geothermal energy can replace a cumbersome propane heating system or avoid the cost of extending natural gas service.

Lastly, folks who have installed geothermal heat pumps in their homes have appreciated how much quieter, reliable and low-maintenance these systems are compared to the traditional furnace and air conditioner. Since heat pumps are much smaller than traditional systems, they can be installed completely indoors, protecting them from harsh weather and preventing outside units from becoming an eyesore in the yard.

With benefits such as these, it's no wonder that geothermal heat pumps are growing in popularity each year. The Geothermal Energy Association estimates that more than 300,000 heat pumps have been installed in the last few years, with the largest markets in Midwestern states such as Indiana, Kentucky, Michigan, Minnesota, Missouri and Ohio.

Something to keep in mind is that geothermal heat pumps are not just for homes. Commercial-sized systems are available which can service schools, apartment complexes or other larger buildings. One such system was installed at the elementary school in Onamia, Minnesota. The 79,700 square foot building uses an ECONAR GeoSource Commercial Line system with 230 tons of heating/cooling capacity. Onamia's system heats, cools, dehumidifies and illuminates the school at half the cost of just heating the adjacent high school, which uses a traditional furnace system!

How Much Does it Cost?

Geothermal heat pumps generally do cost more to install than traditional heating and cooling systems. Much of this is due to the need to dig trenches to install the piping network. For a typical-size home, a heat pump may cost between $9,000 and $14,000 depending on the layout of the piping network. To offset the increased costs, some utilities offer rebates for homeowners that install geothermal heat pumps.

For public buildings, the Minnesota Department of Commerce Energy Investment Loan Program helps finance energy-saving capital improvements. State funds are used for up to a 50% match to a loan or tax-exempt lease from a private lender. No interest is charged on state funds. An applicant may use a local lending institution or other energy conservation financing options such as utilities or vendors. Eligible organizations include cities, counties, towns and public and private schools and hospitals.

Read Up: 

Geothermal Heat Pumps: Introductory Guide, James Bose, 1997.

Closed-Loop Geothermal Systems: Slinky Installation Guide, Fred Jones, 1995.

Act Locally: 

Minnesota Department of Commerce - Energy Investment Loan Program
85 7th Place East
Suite 500
St. Paul, MN 651-297-1221

Econar Energy Systems Corp
19230 Evans St NW
Elk River, MN 763-241-3110
http://www.econar.com

What You Can Do

* Investigate installing a geothermal heat pump in your home. For folks with smaller yards, vertical or "slinky" piping networks that require less yard area can be installed.

* Speak up about installing geothermal heat pumps at your neighborhood's schools or other public buildings. Stress that these systems will allow more taxpayer dollars to be spent on education needs and less on building maintenance and contribute to more sustainable communities. Since geothermal systems operate more quietly than traditional heating/cooling systems, they also provide a better environment for our children to learn.

* Write your congressional and legislative leaders to encourage their support for geothermal energy. Stress the importance of reducing our dependence on foreign energy supplies, creating jobs here and more favorably balancing our trade deficit without the need for drilling or exploring for domestic oil and gas supplies

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