Geothermal Heat Pumps John Sima, PE Connecticut Geothermal Association www.ctgeo.org Today’s Topics The Concept Why Geothermal is “Renewable” What’s Inside the Box? The Geothermal ‘Loop’ Heat Metering See For Yourself Every Geothermal Heat Pump System is Unique Geothermal Heat Pumps Use Proven Technology to Extract Renewable Energy Geothermal Heat Pumps don’t make heat, they simply Move Heat. Geothermal Heat Pumps (GHPs) use the same technology as conventional heat pumps, with one very important difference – they are coupled to the earth, rather than the outside air. GHPs move renewable thermal energy from the ground during the winter to heat buildings, and move heat back into the ground during the summer. Why is it Renewable? The earth’s temperature reflects the average heat absorbed from the sun over the course of the seasons. Heat from the sun renews heat in the earth. Some heat in the earth is also renewed by the GHPs in the summer, when operating in the air conditioning mode. So How Do They Work? The technology is similar to that inside your refrigerator, or auto’s air conditioner. These all move heat. The big advantage with geothermal systems is that they move heat out of the earth, where the temperature is constant. Refrigerators extract heat from the air inside the refrigerator, and reject it to the air inside the house. (Everybody knows that.) Auto air conditioners extract heat from the air inside the car, and reject it outside. Conventional air conditioning systems are the same, extracting heat from indoor air, and rejecting it to air outside. Refrigeration Loop - 4 Main Components Refrigeration Loop - Absorb Heat on the Cold Side (Evaporate the Refrigerant) - Reject Heat on the Warm Side (Condense the Refrigerant) Tuning for Efficiency: - Use more efficient motors - Use larger heat exchangers - Adjust expansion valve for minimum superheat 70 90 70 90 Geothermal Systems Reject Heat to the Earth, or Absorb heat from the Earth Using Water For air conditioning, geothermal systems work almost the same as air-source air conditioners, with one important difference - the outdoor radiator and fan are replaced by a water-cooled heat exchanger and pump. It is so much easier to reject heat to the 50-degree earth than 90-degree (or warmer) outside air. Similarly for heating, geothermal systems absorb heat from water through the same heat exchanger. The big advantage over air-source heat pumps is that the earth’s temperature about 50 degrees. So the heat source is much warmer than the 30-degree or colder outside air. 70 50 70 50 The Geothermal Loop Small pumps circulate a water / antifreeze solution between the heat pump’s heat exchanger and a geoexchange loop installed in the earth. In Connecticut, the most effective geoexchange loop field consists of deep drilled wells. Deep wells offer two advantages – saving space (land), and more importantly, connecting to a constant heat source (deep earth). Heat Metering – Renewable Energy In New Hampshire, geothermal heat pump owners can be paid for the energy their systems extract from the earth. The concept is simple – measure the flow rate and temperature change of the water / antifreeze mixture, to calculate the amount of renewable energy extracted from the earth. This concept also works for solar thermal (hot water) energy extracted from sunlight. Heat Metering Now You can go online now, to see the actual performance of geothermal heat pump systems. Geothermal Heat Pump Systems are being metered right now. Heat metering information may be viewed in real time, from Live Sites, at www.groundenergysupport.com Key Points Geothermal energy is a renewable resource. These systems simply move heat into and out of the earth. Geothermal systems provide efficient, comfortable heating and air conditioning. Geothermal systems save Money, save Energy, and Reduce CO2 Emissions This is GREEN Technology Most Important Point Geothermal Heat Pump systems are unique. Every installation is unique, and every system needs to be designed from scratch. Many heating & cooling contractors have the know-how to select the right size heat pump, but special skills are needed to design the right geoexchange loop field. If the geothermal system is not designed properly, it will not save energy or money. Hire a professional. Go to www.ctgeo.org to find an experienced geothermal professional.
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