The Grant/Douglas/Lincoln Hall geothermal system is a large vertical closed-loop field that uses water to heat and cool the air in the building. This is accomplished by pumping water through pipes buried underground (below the open space near University Hall, to be exact).
The pipes use the earth’s natural ground temperature, along with heating or cooling assistance from equipment in the building, to maintain a constant temperature of 73 degrees F year round in the classroom buildings.
Heat pumps collect heat during winter through fluid circulating in pipes called loops, placed below ground. The circulating fluid carries ground or water-stored heat indoors. In summer, the loop draws away indoor heat and carries it underground or under water, where it is absorbed. In a closed loop system, the circulating water or other suitable fluid stays within the pipes. Best of all – no carbon emissions are associated with geothermal energy! UIC reduced the need to purchase electricity in the summer when Air Conditioning is needed and reduces the need for purchasing natural gas-powered heat in the winter.
The geothermal system has seen a 50% decrease of energy consumption since its implementation in the fall of 2007.
It all started with Grant Hall, a 15,000 square-foot office and classroom building which was renovated in 2007. Its loop field required 14 boreholes drilled 500 feet deep. Based on Grant Hall’s success, a 50-borehole loop field drilled 500 feet deep was added in the same area and hooked up to the 25,000 square-foot Lincoln Hall. This 1960s-era classroom building reopened in late 2009 after receiving LEED Gold certification. Then, nearby Douglas Hall, the 25,000 square-foot classroom was added and hooked up to the system.
Drilling the wells for the pipes of the geothermal energy source.
Geothermal pipes run warm air via water to the buildings in the winter and take away hot air in the summer.
Lincoln Hall’s biggest energy-saving feature is the building’s geothermal heating and cooling system. Almost everywhere on the planet, the upper crust of the surface maintains a nearly-constant temperature between 50 and 60°F (10 and 16°C). A geothermal system takes advantage of this natural feature, using pipes buried in the shallow ground near the building, a heat exchanger, and ductwork that runs into the building. In winter, heat from the relatively warmer ground goes through the heat exchanger into the building. In summer, hot air from the building is pulled through the heat exchanger into the relatively cooler ground. Heat removed during the summer can be used as no-cost energy to heat water.
In our system, we use water to heat the air. Water is pumped through the pipes buried up to 400 feet underground, which is connected to a heat pump in Grant Hall. A heat pump is a machine that moves heat from one location to another using mechanical work. One common type of heat pump works by exploiting the physical properties of an evaporating and condensing fluid- a refrigerant; which heats or cools the air depending on the time of year. The water starts the geothermal cycle again and the air is distributed to each individual room in Lincoln Hall by the heat pumps that are located in the ceiling of the corridors. Since there is no basement in Lincoln Hall, the pumps are located in the ceiling; flexible tubing has been used to make maintenance easier.
The refrigerant circulates through tubes (refrigerant lines) that run throughout the heat pump. A geothermal heat pump in cooling mode acts identically to an air conditioner. Refrigerant vapor exits the compressor at a high pressure and temperature (120o–140o F) that is warmer than the ground water temperature. As a result, it spontaneously loses heat when it enters the heat exchanger causing it to condense. The refrigerant leaves the condenser as a liquid, still under high pressure. The expansion valve vaporizes some refrigerant and lowers its pressure as well as its temperature to 40o-50o F. The refrigerant enters another heat exchanger where it absorbs indoor heat. As a result, the evaporator vaporizes the rest of the liquid refrigerant. The low-pressure refrigerant vapor leaves the evaporator and returns to the compressor, where the cycle begins again.
The reversing valve can be switched to heating mode such that the high pressure output of the compressor is directed toward the condenser where the refrigerant gives up its heat to the room. As a result, the refrigerant condenses to high pressure liquid. It is then expanded in the reverse direction and vaporized in the evaporator where it gains heat from the ground water. The refrigerant vapor then returns to the compressor where the cycle begins again.
In the mechanical room, located on the third floor, there is an energy recovery wheel; this takes about 90% of the energy (heat) from the exhaust air and puts this heat into the outside air going into the building.
Grant Hall is also running on a geothermal heating system and since opening, there has been approximately a 50% decrease in the energy consumption of the building when compared to a conventional year round heating/cooling system. The aim is to run all three buildings in the cluster (Lincoln, Grant and Douglas Halls) off the same geothermal system.