West Chester University, PA Geothermal Energy
Status: Initiated in 2004
Source File: http://vortex.wcupa.edu/ec/geothermal.shtml
Q. What is an efficient way to keep cool in the summer and warm in the winter?
A. Dig a hole in the ground!
Yes, you read that correctly. It is not that simple, but the hole is the pathway to energy efficient cooling and heating year round. A system that starts with the hole in the ground is called a ground source heat pump (GSHP) or a geoexchange system.
Ground source heat pumps can be used to extract heat from the ground and pump it into a building to provide space heating and to pre-heat domestic hot water. In the summer months this process can be reversed to meet the cooling requirements of a building.
The concept of heating and cooling through the use of heat pump technology is nothing new. Heat pumps are commonplace in most households and offices in the form of refrigerators and air conditioning. They are designed to transfer heat from one place to another, by use of a compressor. How does it work?
Geoexchange systems work on a different principle than an ordinary furnace/air conditioning system, and they require little maintenance or attention. Furnaces must create heat by burning a fuel, typically natural gas, propane, or fuel oil. With geoexchange systems, there's no need to create heat, hence no need for chemical combustion at the building (though, of course, the electricity used is usually made via combustion). Instead, the Earth's natural heat is collected in winter through a series of pipes, called a loop, installed below the surface of the ground or submersed in a pond or lake. Fluid circulating in the loop carries this heat to the home. An indoor geoexchange system then uses electrically-driven compressors and heat exchangers in a vapor compression cycle - the same principle employed in a refrigerator - to concentrate the Earth's energy and release it inside the home at a higher temperature. In typical systems, duct fans distribute the heat to various rooms; other applications include water-to-water transfer, as seen in a radiant floor system.
In summer, the process is reversed in order to cool the home. Excess heat is drawn from the home, expelled to the loop, and absorbed by the Earth. Geoexchange systems provide cooling in the same way that a refrigerator keeps its contents cool, by drawing heat from the interior, not by injecting cold air.
Geoexchange systems do the work that ordinarily requires two appliances, a furnace and an air conditioner. They can be located indoors because there's no need to exchange heat with the outdoor air. They're so quiet homeowners don't even realize they're on. They are also compact. Typically, they are installed in a basement or attic, and some are small enough to fit atop a closet shelf. The indoor location also means the equipment is protected from mechanical breakdowns that could result from exposure to harsh weather.
Air Source Versus Ground Source Heat Pumps
Geoexchange works differently than conventional heat pumps that use the outdoor air as their heat source or heat sink. Geoexchange systems don't have to work as hard (which means they use less energy) because they draw heat from a source whose temperature is moderate. The temperature of the ground or groundwater a few feet beneath the Earth's surface remains relatively constant throughout the year, even though the outdoor air temperature may fluctuate greatly with the change of seasons. At a depth of approximately six feet, for example, the temperature of soil in most of the world's regions remains stable between 45°F and 70°F. This is why well water drawn from below ground tastes so cool even on the hottest summer days.
In winter, it's much easier to capture heat from the soil at a moderate 50°F than from the atmosphere when the air temperature is below zero. This is also why with geoexchange systems there is no difficulty blowing comfortably warm air through a home's ventilation system, even when the outdoor air temperature is extremely cold. Conversely, in summer, the relatively cool ground absorbs a home's waste heat more readily than the warm outdoor air.
Renewable and Efficient
Studies show that approximately 70 percent of the energy used in a geoexchange heating and cooling system is renewable energy from the ground. The remainder is clean, electrical energy which is employed to concentrate heat and transport it from one location to another. In winter, the ground soaks up solar energy and provides a barrier to cold air. In summer, the ground heats up more slowly than the outside air.
Geothermal at WCU
As a part of the Green Initiative, geothermal exchange is being implemented wherever possible. At present, the South Campus Apartments, built in 2004, are operating with a geothermal system. A geothermal system is planned for the renovation of Swope Hall. At Swope Hall, the wells will be located in the lawn area west of the building.
Besides the obvious cost savings, the advantages of a GSHP system are:
- Heating without combustion of fossil fuels
- No carbon monoxide or carbon dioxide
- Increased safety
- Simpler design, maintenance, and operation
- Free hot water in the summer
- No unsightly/noisy air conditioning or air source heat pumps in the yard
- Smaller mechanical rooms or closets, saving space for other uses
- Lower annual maintenance costs