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Due to the limited area available on site, placing the geothermal wells was a challenge. These wells need to be at least 20 feet apart to be effective. For these reasons, 14 vertical wells are placed 20 feet apart from each other on the driveway approaching the building. Originally, the team members explored the possibility of distributed heat pump systems throughout the building, but later concluded that using one centrally located heat pump would serve the building's needs better.
A general representation of ground temperature changes over the year
Ground AS AN ENERGY Source
Ground AS AN ENERGY Source
Like a water tank, the ground absorbs or rejects heat through annual seasonal changes to maintain a stable temperature. As a result, the underground temperature is lower than above-ground air temperature in the summer, and higher in the winter. The ground is hence a valuable source, acting as a thermal battery for a building's heating and cooling. Heat captured from the indoor air during the summer is rejected to geothermal wells, and stored in the ground to use for heating in the following winter. This is cost-effective, sustainable and environment-friendly.
Single Borehole
Single Borehole
Each borehole on the site is 510 ft (155 meters) deep, and has a radius of 6-inches (15 centimeters). Within each borehole, there are two 1.25-inch polyethylene (PEX) tubes filled with a water-glycol solution, one of which is geothermal supply (GTS), and the other is geothermal return (GTR). They exchange heat with the ground, tying back into the building's heating ventilation and air-conditioning (HVAC) system.
The geo-exchange process requires a good seasonal balance between the hot and cold months, so that an approximately equal amount of heat that is added and withdrawn over the course of a year. Otherwise, the ground temperature would become increasingly hotter or colder over a period of time, harming the local ecological environment.[1]
System Connection
System Connection
The geothermal wells are connected to the mechanical room, from where the water is pumped to the rooftop, where the water source heat pump is located.
Text Reference:[1] Building In Bloom by Mary Adam ThomasPhoto Reference:https://igws.indiana.edu/Geothermal/HeatPumpsAnimation and Video Credits:All animations and videos on this page were produced by Group C, 48721 - Building Controls and Diagnostics 2019, Carnegie Mellon University
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