Geothermal heat pumps can be extremely efficient

The word geothermal stems from the Greek words “geo” for earth, and “therme” for heat, which literally means heat from the earth.

Our ancestors used primitive geothermal energy in the form of hot springs for bathing and cooking. In 1852, Lord Kelvin invented the heat pump and brought geothermal to a new level. But it took Robert C. Webber in the 1940s to harness geothermal for home use.

Webber ran freon gas through copper tubing underground. The gas condensed in the piping through his cellar, released its heat and expanded. The expansion moved it through the ground coil to pick up another load. He set up a fan to distribute the “conditioned air” through his home. He was so pleased with the results that the next year, Webber sold his old coal furnace.

Webber’s system worked because air temperatures change constantly, yet soil temperature in the earth’s upper 10 feet stay consistently between 50 and 60 degrees Fahrenheit. That means that in the winter, the soil is much warmer than the air, so heat can be taken from the soil to warm a home to 50 or 60 degrees. A supplementary heater can warm the air the rest of the way as it circulates through the house.

In the summer when the soil is cooler than the air temperature, the process is reversed and warm air from the house is cooled by underground temperatures brought into the house.

Geothermal heat pumps are vastly more efficient than regular heat pumps because the heat is moved around through water circulating between the building and the earth in “ground-loop” piping buried in the ground.

In the summer the water is warmed by the heat of the building and transfers that warmth into the ground. In the winter, the water is warmed by heat from the ground and transfers that heat to the building. Heat pumps move the water through the tubing so that the transfer is continuous.

According to the U.S. Environmental Protection Agency, geothermal heat pumps are the most energy-efficient, environmentally clean, and cost-effective systems for heating and cooling. The EPA found that geothermal heat pumps are on average 48 percent more efficient than gas furnaces and 75 percent more efficient than fuel oil furnaces. This translates into a savings to consumers of 30 percent to 70 percent of their heating costs, and 20 percent to 50 percent of their cooling costs. These reductions help offset the costs of installing the expensive equipment.

John Lynch wrote in “Home Power Magazine” that the average payback for a geothermal system for residential use is about seven years. He notes “if the cost of maintenance and replacing equipment over the long term are taken into account, the payback period becomes shorter.”

“Inside-the-home costs of installing a 10 kilowatt heat pump system is $7,656, and the cost of the ground loop is $3,364 for a total of $11,020,” says Lynch.

Other estimates for geothermal systems can go as high as $30,000 for a similarly sized home. Compare that to the cost of a new oil-fired boiler which is around $8,000, and you see why the cost difference can scare many homeowners away.

The payback period on larger buildings can be as small as five years, making geothermal especially appealing to schools and community centers. The Howland Cultural Center in Beacon, N.Y., raised $90,000 from city, county and state grants, and from the community by hosting concerts by local musicians, poetry readings, coffee houses, and membership donations, according to Michael Jurkovic, Howland board member.

Geothermal installer Charles Lazin of Altren Consulting, drilled five geothermal wells 400 feet deep between the Howland and a neighboring brownstone building. Two heat pumps distribute air to two main zones at the Howland – a large performance and exhibition space and a smaller office area. Lazin estimates the Howland’s system will cut heating costs by 50 percent or more, helping to offset the installation costs with energy savings.

Jurkovic points out that the Howland system delivers “hot water, that comes as a result of the exchange process, has made our patrons and visitors who use the restrooms real happy.”

- Surveys by utilities indicate higher levels of customer satisfaction from geothermal systems. Of all geothermal customers, 95 percent would recommend the system to a friend.

- The 900,000 current geothermal installations have eliminated more than 5.2 million (metric) tons of carbon dioxide annually.

- Current geothermal systems have saved more than 7 billion kilowatts in electricity, and 36 trillion BTUs of fossil fuels.

- The energy savings of these geothermal installations are equal to taking more than 1,165,000 cars off the road, planting more than 346 million trees, and reducing U.S. reliance on imported fossil fuels by 19.3 million barrels of crude oil per year.By Shawn Dell Joyce