Embrace geothermal heating and cooling

By Tom Phelan - ReminderNews
- posted Tue., Sep. 13, 2011
- Contributed Photo

There’s no quick way to escape the cost of the fuel the oil truck will deliver this winter, or the cost of natural gas or electricity coming from the power company – short of moving to a more moderate climate before winter comes. Among the solutions for alternative energy sources that could work in homes in this area, geothermal heating and cooling deserves some consideration. This is particularly true if you are building a new house.

We normally think of technology as being complex, but the idea here is actually quite simple. The concept is really much like that of a refrigerator, except that it is used both to cool and to heat. It accomplishes this by reversing the process it uses to exchange thermal energy with the earth. It uses a fluid that is an environmentally safe product like the ethylene glycol (antifreeze) in your automobile. The fluid flows through loops of pipe buried 5 to 8 feet beneath the earth around the house.

The material used in the loops buried beneath the ground is quite durable, yet it readily allows the transfer of heat to and from the ground around it. Some manufacturers create their loops of polyethylene (plastic), while others use copper.

Whether you have a vertical or horizontal loop system and how long it is depends on the size of your lot, the type of soil it will be buried in, and the load your home requires. Moderate climates are best for geothermal exchange.

The temperature beneath the ground where the loops take the system’s ethylene-glycol fluid will remain a fairly constant 50 to 57 degrees, year-round. The fluid is pumped into the ground and returns at about 50 degrees. The compressor turns the fluid to a liquid state, and in so doing, creates heat that is directed to an air handling system that distributes it through the warm air ducts throughout the house. When cooling is called for, the system reverses itself, taking the heat out of the house, transferring it via the heat exchanger to the fluid circulating in the underground loops. There, it is cooled and returned to the house.

Most conventional heating and cooling systems use a heat pump – a unit with a compressor that operates outside the house. It’s a noisy apparatus that dissipates its heat out into the air. A system that performs geothermal exchange combines the functions of a conventional furnace and separate air-conditioning system in a single unit. It is markedly different in that it doesn’t require outside air for combustion, nor does it exchange hot air with the air outside of the house.

Certainly, the system’s compressor uses electricity, but the cost of that electricity is significantly less than that of the oil or gas required to run a furnace or, through electricity, run an air-conditioning system.

Configuring and installing a geothermal exchange system is not a project for the weekend DIYer. An industry professional is required to conduct the analysis of your home and its requirements, as well as of the climate and soil in your area. They will be able to analyze the potential for heat loss and gain of a geothermal system, as well as the correct size (capacity) of the loops and the compressor.

The optimal time to install a geothermal exchange system is during the construction of a house, when the ground has not yet been graded or landscaped. The loops and placement of the system can be integrated into the design of the house and its surroundings. Design of the house can also be fitted with energy conservation measures that will lessen the need for heating and cooling capacity of the system to be installed.

While the planning, selection and installation of a system is costly, the maintenance and operation is very inexpensive. And given the level of current environmental consciousness, state and national governments are offering financial incentives to outfit or retrofit a home with systems that make use of the passive energy sources. Tax credits and rebates in the thousands of dollars are available to those who are bold enough to implement environmentally-friendly systems while the oil truck is delivering hundreds of gallons of fuel at a fluctuating price.

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