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Over the past few months we’ve noticed quite a bit of interest in geothermal heating and cooling amongst our site visitors, and in particular in geothermal heat pumps. We’ve also had many questions from people about exactly what they are and how/if they should consider them as an eco-friendly heating/cooling option. If this describes you, then read on - these systems ARE incredibly promising technologies to heat and cool your home, but they’re also more complicated than your typical AC or furnace unit. We’ll try to help clear the air!
We get into quite a bit of detail below, but before you get into that here’s a very quick summary of geothermal heat pumps:
- Geothermal (or ground source) heat pumps can be incredibly efficient, delivering 3-6x as much energy for heating and cooling as you use to power the equipment;
- They are in some ways a renewable energy system, since they use the heat contained in the earth to provide heating / cooling;
- They do require extensive installation work, including excavation or drilling to install subsurface pipes; and
- They are more expensive than traditional heating/cooling equipment, but the payback period is less than five years almost everywhere in the country due to their greater efficiency.
Editor’s note: While we’ve discussed home geothermal systems a number of times around the Green Options Media network (see the list at the bottom), we’re glad to bring you today’s post from GreenBuildingTalk on the subject. They not only provide an overview of the technology, but point you to some cutting-edge models of geothermal heat pumps. This post was originally published on Thursday, May 15, 2008.
With energy costs on the rise, homeowners are looking for ways to offset higher bills. Geothermal heat pumps are one of the best options, as they currently offer the highest efficiencies of any heating and cooling system available today. A study by MIT emphasizes the potential for geothermal, and manufacturers are offering more options for consumers. While at the Midwest Builders show, I stopped by ClimateMaster and WaterFurnace booths to learn more about their newest offerings. Before diving into the respective systems, let’s review the three main components of a geothermal system; the heat-pump unit, the liquid heat-exchange medium (open or closed loop), and the air-delivery system (ductwork).
The heat pump simply moves heat energy from one place to another, just like your refrigerator or air conditioner. But a major difference is that air conditioners and refrigerators transfer heat in only one direction, while a heat pump can transfer heat in two directions, thereby heating or cooling the space. In the cooling mode, the geothermal heat pump takes heat from indoors and transfers it to the colder earth through either groundwater or an underground earth loop system. In the heating mode, the process is reversed.
The buried pipe, or earth loop, is the most important technical advancement in heat pump technology to date. The idea to bury pipe in the ground to gather heat energy began in the 1940s. But it’s only been in the last twenty-five years that new heat pump designs and more durable pipe materials have been combined to make geothermal heat pumps the ultimate in efficiency. The two main types of loops available are open and closed. An open loop system is less expensive to install, but over time could require more maintenance. A closed loop system is more expensive up front, but requires almost no maintenance. As manufacturers phase out R-22 (HCFC) refrigerant, there have been more environmentally friendly liquid mediums brought into the marketplace to use in your system. The most common antifreeze solutions in the U.S. and Canada are propylene glycol, methyl alcohol, and ethyl alcohol.
