Geothermal Heating and Cooling Add ‘Green’ to Commercial Buildings
For owners of commercial buildings, climate control costs are top of mind as energy prices continue to rise. It’s easy to understand, therefore, why geothermal heating and cooling is gaining attention among those who design and maintain non-residential facilities.
“Developers and managers of these properties are definitely beginning to understand that they can reduce energy costs significantly by installing geothermal systems,” says Mark Miller, President of Miller Environmental Group (MEG), a Calverton, NY, environmental response, remediation, and alternative energy solutions company. “We believe in both the environmental and financial benefits so strongly, that we have just invested in installing a complete geothermal heating and cooling system in our headquarters. “
What is geothermal energy?
The earth absorbs the sun’s heat, so that between five feet and several hundred feet underground, the temperature remains relatively constant at about 55 degrees Fahrenheit. A geothermal system allows us to “harvest” the earth’s heat energy by bringing it indoors in the winter and by using it to discharge the heat extracted from the building in the summer. There are several different types of ground temperature exchange systems that can be used to provide this transfer of heat depending on geological conditions. These exchange systems consist of vertical or horizontal closed loops, open loops, and pond/lake loops.
The main component of a typical closed-loop geothermal system is a ground-source or geothermal heat pump that cycles a water-based solution through a continuous loop of flexible piping buried underground, either horizontally or vertically, depending on soil conditions and available land.
In a closed-loop system, a geothermal heat pump cycles fluid continuously through pipes that act as heat exchangers, transferring the earth’s heat energy into the building’s heating/cooling system. (image courtesy of U.S. Department of Energy) Ground-source heat pumps move energy from one place to another; they do not create energy. The result is that, with the exception of the minimal amount of electricity needed to operate the heat pump and air circulators, no fossil fuels are burned in heating or cooling the building. A U.S. Environmental Protection Agency study reported that ground-source heat pumps are as much as 44% to 72% more efficient than conventional heating and air conditioning systems, which translates into substantial energy cost savings.
Costs and payback
The costs of installing ground-source heat pumps during construction are competitive with those of traditional climate control systems. Retrofitting an existing structure will be more expensive, but in either case, the savings over time make the investment worth considering.
The U.S. Department of Energy estimates that ground-source heat pumps use 25% to 50% less electricity than conventional heating or cooling systems, which in non-residential buildings can represent a significant dollar amount, especially during peak demand periods. The DOE also notes that these systems improve humidity control by maintaining about 50% relative indoor humidity, making them very effective in humid areas.
Another advantage of a geothermal system is that the required equipment takes up much less space than conventional systems, allowing for greater design flexibility or more productive use of existing space and elimination of outdoor or rooftop installations. Maintenance costs are also reduced. Ground-source pump systems have relatively few moving parts and these parts are kept indoors, and the DOE reports that the underground pipes often carry warranties of between 25 and 50 years and the pumps often last at least 20 years.
Environmental concerns
While there is no doubt that geothermal systems are friendly to both the earth and the budget, how and where they are installed make a difference. “From our extensive work in groundwater remediation,” Miller explains, “we know that the composition and properties of the soil in which you install the geothermal exchange system makes a difference in the range of efficiency. We also know that it’s important to consider the effects on environmentally sensitive factors such as the aquifer.”
MEG, which was founded in 1971, installed the first groundwater treatment system on Long Island more than 30 years ago and was one of the first companies to be awarded a groundwater remediation contract by the New York State Department of Environmental Conservation. It is now using its extensive soil studies experience to benefit its growing list of geothermal system clients.
The 30-ton geothermal heating and cooling system installed in the 35,000-square-foot MEG headquarters and training center consists of eight heat pumps and thirty 200-foot closed loops of piping installed by drilling holes vertically on both the north and south sides of the building for increased efficiency. The depth of the loop field was designed for and installed entirely in the upper glacial aquifer to prevent drilling in the deeper aquifers (Magothy) and avoid penetrating any confining clay layers. “We take special care to study the geology and hydrogeology around an installation so as to eliminate any negative environmental impact and maximize system efficiency,” Miller says.
Miller Environmental, who installed a 30-ton geothermal heating and cooling system at its Long Island headquarters, performed soil studies to determine the optimal drilling depth for protecting the aquifer and improving system efficiency.(photo: MEG)
Some municipalities around the country, including Shelter Island, NY, are studying the environmental impact of geothermal systems. Because of increasing salt water intrusion potential to aquifers in coastal zones, open-loop systems are of particular concern. In an open-loop system, groundwater that travels through the heat pump returns to the environment through an injection well or through surface discharge.
“As with all geothermal exchange systems, proper subsurface evaluation of such factors as the geology, groundwater transport flow directions, and groundwater quality, to name a few, are necessary to insure that there is no disruption to the subsurface environment. Open-loop systems generally may not be practical for some conditions,” says Miller, “and we strongly recommend a proper understanding of hydrogeologic conditions before the final design of the ground source exchange method is installed."
Green trends continue
Consumers are flocking to auto dealerships to place orders for hybrids, there is a "Green Channel" on cable television and there are pension funds investing in only environmentally progressive companies. There is no question that environmental friendliness has captured consumer attention.
The U.S. construction industry has taken note. In its 2008 U.S. Construction Overview, FMI, the construction industry consulting firm, projects that $21.2 billion of all new non-residential construction in 2008 will employ the use of green-building principles—a 58 percent increase over 2006. “This sizable growth in green construction,” the report states,” has created a shift in perception among owners and the architectural and engineering communities over the last few years—the industry is increasingly recognizing green building capabilities as a necessary part of a firm’s best practices.” And, without doubt, geothermal heating and cooling is taking its rightful place among those best practices.
“At Miller, we are convinced that, under the right conditions, geothermal heating and cooling is the alternative energy source of choice,” says Miller. “Everyone here works every day to make our planet a cleaner and healthier place. That’s our business. So, finding a way to help homeowners and commercial building owners meet their heating and cooling needs in an environmentally responsible way is very rewarding.” |
