2008 Issue

www.utahengineerscouncil.org 26 Quietly and without much fanfare, ground coupled, geothermal heat pump systems have become very popular over the past decade in Utah and around the country. It is an exciting concept that uses the earth as an energy source to heat and cool our homes, schools and offices. The “geo” system links together highly efficient heat pumps with underground pipes that descend hundreds of feet into the earth. T HE UNDERGROUND PIPING, CALLED A GROUND LOOP HEAT EXCHANGER (GLHE), IS AN ENVIRONMENTALLY-SAFE SYSTEM WHERE WATER CIRCULATES deep in the ground through polyethylene pipes and exchanges thermal energy before returning to the building. GLHE’s have Ground Coupled Heat Pump Systems By Richard Reeder, P.E., LEED been placed in out-of-the-way, underground locations beneath playgrounds, back yards, soccer fields and parking lots. Deep underground, they are safe from damage and go completely unnoticed. In the cooling season, heat is extracted from the building and transferred into the ground through the ground loop heat exchanger. In the heating season, heat is absorbed from the deep earth and is trans- ferred into the building. Good GLHE designs carefully balance the energy exchange with the earth to ensure negligible influence on the subterranean soil temperatures. Heat pumps consist of a fan, a couple of coils, and a compressor that are all housed in a cabinet about the size of a residential furnace. They have a reversing valve that allows them to either heat or cool regardless of the sea- son or water temperature. The heat pumps can be located in mechanical rooms, closets, or above ceil- ings. They are best located near the areas they are serving. This reduces the length of duct runs, reduces ceiling space requirements and improves energy efficiency by reducing the fan horsepower requirements. The amount of building square footage that was once dedicated strictly to mechanical equipment can now be dramatically reduced