5-Ton Direct Exchange Geothermal System in Ithaca, NY
Challenge
These homeowners wanted their home to produce as much energy as it uses. So we talked about the right geothermal system for them.
Solution
An Advanced Geothermal Technology single-stage GC-60-6DS0 geothermal heat pump (5 ton/60,000 BTU/hr max) with refrigerant to air heating and refrigerant to air cooling capacity for the existing house was installed in the Customer's mechanical space. The system was designed around the 38,000 BTU/hr max design load for the house, and interconnects to the existing forced air distribution system for heating and cooling. The system also provides primary DHW for the house (around 80% annually), and the system includes one indirect fired tank as a buffer tank for the DHW. The geothermal ground loops are a refrigerant closed loop system, consisting of ten (10) vertical bores or earthtaps spaced around the circumference of a circle. If soil and site conditions allow, bores can be done diagonally around a 5 ft circle (spacing initially between the bores is 2.6 ft apart but rapidly increases). If site conditions are not suitable for diagonal drilling, then straight vertical bores will be done around a 15ft diameter circle (spacing between the bores around 7.5 ft). Each earthtap is typically 70 ft deep and contains 120ft of 1/2" diameter copper pipe in the bore, with the exact design depending on the geology and hydrology of the site. Please note that DX geothermal systems provide a 25% greater Coefficient of Performance (COP) than traditional water-based geothermal systems. In addition, vertical geothermal ground loop systems also provide good thermal stability across the heating season, typically a 8-12% increase in the system's COP as compared to horizontal systems. Complete system monitoring - including the energy production (BTU) of the heat pump, electricity consumption (kWh) of the heat pump - is being provided using a custom datalogger and online Halco Monitoring Portal. As designed, this system should function at an annual average COP of 4.0, thus increasing the heating system efficiency from around 90% to 400%, and completely eliminating the use of natural gas for building heating. With this COP and based on the expected heat load for the building, the geothermal system would require approximately 7,300 kWH/year to operate. The majority of this electricity is generated by an on-site solar electric array, avoiding the emission of at least 11,200 Lbs CO2/year.
