By Don Magglioli
Nov. 3, 2011
When it comes to using alternative heating sources, commercial building owners often overlook geothermal heating and cooling as an option. Truth be told, geothermal is more cost-efficient to install and offers a substantial return on investment for commercial building owners than other conventional systems.
There is often confusion of exactly what is geothermal. Geothermal can mean using hot waters that are naturally occurring below the earth’s surface for either direct-use heating or electrical power generation. Geothermal can also mean simply using the constant temperature of the earth’s shallow temperatures (6 ft. to 1,500 ft. below ground surface) as a heat storage medium. This heat storage is also known as geoexchange. Heat pumps are used to heat or cool the building and the earth is used to store heat. The heat pumps are used to “exchange” the heat from or to the earth.
The three main geoexchange systems are:
-
Closed Loop;
-
Open Loop; and
-
Standing Column Well.
In a closed loop system, a pump circulates a heat transfer fluid through a series of buried pipes in a closed loop: the fluid never leaves the system, but rather travels back and forth in a loop between the earth connection and the heat pump. The length of the ground loop is determined by the size of the heating and cooling loads of the building and the ground thermal properties. The loads are defined by the size of the building, type of construction, use of the building, duration of the heating and cooling seasons, and climate.
Closed-loop systems are environmentally benign. They are sealed so that no fluid is exchanged with the environment. The fluid often includes an antifreeze solution to protect the heat pump equipment. The high-density polyethylene piping used in geoexchange systems is the same or higher grade of pipe used in cross country natural gas piping and often comes with a 50-year warranty.