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Geothermal Heat Pumps

Geothermal Heat Pumps. Marisca Oana Teodora Fizica 11B. What is a heat pump?. a machine that moves heat from a location to another location, using mechanical work. What are the major parts of a heat pump?.

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Geothermal Heat Pumps

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  1. Geothermal Heat Pumps MariscaOanaTeodora Fizica 11B

  2. What is a heat pump? • a machine that moves heat from a location to another location, using mechanical work

  3. What are the major parts of a heat pump? • Compressor: This increases the pressure of the refrigerant so that it will accept the maximum amount of heat from the air. • Condenser: Coils that move heat to or from the outside air. • Evaporator: Coils that move heat to or from the air inside the home. • Air handler: Fan that blows the air into the ducts of the home. Components 1, 2, 3 and 4 are found in all standard air conditioners. • Reversing valve:Changes the heat pump from air conditioning to heating, and vice versa. This is not part of the thermostat.

  4. What is a geothermal heat pump? • a heat pump which extracts heat from ground or water.

  5. The engineering and scientific communities prefer the terms "geoexchange" or "ground source heat pumps" because geothermal power traditionally refers to heat originating from deep in the earth's mantle. Ground source heat pumps harvest a combination of geothermal power and heat from the sun when heating, but work against these heat sources when used for air conditioning.

  6. How does it work? • An antifreeze solution is circulated through plastic pipes buried beneath the ground for closed loop systems. The fluid gathers heat from the earth and circulates it through the system and into the building. During the summer, the system reverses itself and pulls heat from the structure and places it in the ground. This process creates free hot water in the summer and produces a considerable savings on hot water in the winter.

  7. The COP for a heatpump in a heating or coolingapplication, withsteady-stateoperation, is: • where • ΔQcoolistheamount of heatextractedfrom a coldreservoir at temperatureTcool, • ΔQhotistheamount of heatdeliveredto a hot reservoir at temperatureThot, • ΔAisthecompressor'sdissipatedwork. • Alltemperatures are in absolute units

  8. Heatpumps are always more efficient at heatingthan pure electric heaters, evenwhenextractingheatfromcoldwinterair. But unlike an air-sourceheatpump, whichtransfersheatto or fromtheoutsideair, a groundsourceheatpumpexchangesheatwiththeground. Thisismuch more energy-efficientbecause underground temperatures are more stablethanairtemperaturesthroughtheyear. Seasonalvariationsdrop off withdepthanddisappearbelowsevenmetersduetothermalinertia.

  9. Groundsourceheatpumps, which are alsoconfusinglyreferredto as Geothermalheatpumps, typicallyhavehigherefficienciesthanair-sourceheatpumps. Thisisbecausetheydrawheatfromtheground or groundwaterwhichis at a relatively constant temperatureallyearroundbelow a depth of abouteightfeet (2.5 m). Thismeansthatthetemperaturedifferentialislower, leadingtohigherefficiency. Ground-sourceheatpumpstypicallyhaveCOPs of 3.5-4.0 at thebeginning of theheatingseason, withlowerCOPs as heatisdrawnfromtheground. The tradeoff for thisimproved performance isthat a ground-sourceheatpumpis more expensivetoinstallduetotheneed for thedigging of wells or trenches in whichto place thepipesthat carry theheatexchange fluid. Whencompared versus eachother, groundwaterheatpumps are generally more efficientthanheatpumpsusingheatfromthesoil.

  10. How many types of geothermal heat pumps exist? • geothermalheatpump (extractsheatfromtheground or similar sources) • geothermal–airheatpump (transfersheattoinsideair) • geothermal–waterheatpump (transfersheatto a tank of water); • Closed-loop system-horizontal, vertical and lake/pond; • Open-loop system

  11. Is it effective? • The setupcosts are higherthan for conventionalsystems, but thedifferenceisusuallyreturned in energysavingsin 3 to 10 years. Systemlifeisestimated at 25 years for insidecomponentsand 50+ years for thegroundloop. As of 2004, there are over a millionunitsinstalledworldwideproviding 12 GW of thermalcapacity, with an annualgrowth rate of 10%.If deployed on a large scale, thistechnologymayhelpalleviateenergycostsand global warming.

  12. Two geothermal heat pumps used at the College of Southern Idaho.

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