We’ve had several questions asked regarding the geothermal energy system, so here are a few answers to those questions. We’ll post a few more on our blog as we receive more questions.
How many wells are there?
What is the average, maximum, and minimum well depth?
What is the temperature of the water in the pipes?
Has this ever been done before at a university?
Were there any experts outside of Physical Facilities consulted before the project started?
Will the mall between V.H. McNutt Hall and the Curtis Laws Wilson Library be a new parking lot?
How does a screw type heat recovery chiller work?
Will the geothermal system provide heat or only cooling?
645 wells have been installed for the three geothermal plants under construction.
The wells range in depth from 420 to 440 feet.
The groundwater temperature in this area is approximately 60°F. As the year progresses from predominantly cooling season to heating season, the temperature of the water circulating in the closed geothermal loop and well piping will vary from 90°F to 100°F in the early fall to 40°F to 45°F in the spring.
Ground source heat pump technology has been around for many years, but only one other university has completed a project of this scale.
McClure Engineering offered consulting while Physical Facilities was evaluating feasibility.
No. This area will be restored to a landscaped pedestrian area.
A heat recovery chiller operates on the basis of a refrigeration cycle: the same basic cycle that is used for refrigerators, air conditioners, and heat pumps you find in your homes. It is designed to provide both useful cooling and useful heating energy from the machine. The work or energy put into the machine through the compressor is used to simply transfer heat from evaporator to the condenser, which makes it a more efficient use of energy than combusing fuel for heat.
As seen in the diagram below, the refrigerate, R-134a in our chiller, is first compressed using a screw-type compressor. This hot gas is then condensed to a liquid as it travels in a circuit through the condenser, and heat is transferred to the water flowing through the condenser tube bundle.
The pressure and temperature of the refrigerant is reduced as it flows through the throttling valve. The refrigerant next passes through the evaporator where heat is transferred from the water flowing through the evaporator tube bundle back to the refrigerant. Then the cycle repeats as the refrigerant goes back to the compressor. The refrigerant is confined inside of the heat pump chiller for the entire process.
The heat recovery chiller coupled with the geothermal well fields can be operated to provide heating water only, cooling water only, or can simultaneously provide heating and cooling water, if required.
Heating Water Production
Water from the campus heating water return lines flows through the condenser of the heat recovery chiller, where it is heated to a nominal 120 degrees Fahrenheit for distribution back to campus. The heat transferred from water flowing in the evaporator of the chiller, which has been circulated through the geothermal loop, warms as it circulates through the well fields.
Chilled Water Production
Water from the campus chilled water return lines flows through the evaporator of the heat recovery chiller, where it is cooled to a nominal 44 degrees Fahrenheit for distribution back to campus. The heat is transferred to water flowing in the condenser of the chiller, which has been circulated through the geothermal loop, cools as it circulates through the well fields.
Simultaneous Heating and Chilled Water Production
Water from the campus heating water return lines flows through the condenser of the heat recovery chiller, where it is heated to a nominal 120 degrees Fahrenheit for distribution back to campus. The heat is transferred from water flowing in the evaporator of the chiller, which in this case is water from the campus chilled water return lines through the evaporator of the heat recovery chiller, where it is cooled to a nominal 44 degrees Fahrenheit for distribution back to campus. Geothermal loop water is mixed as necessary through one of the tube bundles to balance the loads on the chiller.
The geothermal system will provide heating in the winter and cooling in the summer.