Geothermal Energy Geothermal Heat Pumps

  • Published on

  • View

  • Download


Geothermal Energy Geothermal Heat Pumps. San Jose State University FX Rongre April 2008. District Heating. Direct use of geothermal hot water. Heat Conduction in the Ground. One-dimensional Conduction equation is: Along the year, the surface temperature is a sinusoidal function: - PowerPoint PPT Presentation


Geothermal EnergyGeothermal Heat PumpsSan Jose State UniversityFX RongreApril 2008District HeatingDirect use of geothermal hot waterHeat Conduction in the GroundOne-dimensional Conduction equation is:Along the year, the surface temperature is a sinusoidal function:The analytical solution is:Ground Temperature Ground temperature remains constant around the year for a depth greater than 10m.Ground characteristics:T0= 20oC = 2.10-7 s-1 = 2,300 kg.m-3 C = 900 k = 1.5 W.m-1.K-1It depends on annual average temperatureGround Temperature at 10mAverage Annual TemperatureHeat-Pump/ChillerA Heat-Pump as a Chiller transfers heat from the cold source to the hot source using compression to change the evaporation/condensation temperaturelnP-h DiagramHeat-Pump cycleValveGeothermal Heat Pump Two types of exchangersVertical loop More expensive Reliable Smaller foot-printHorizontal loop Less expensive May be perforated Large foot-printGeothermal Heat PumpOne can also use the aquifer or a pondOpen water loop Excellent transfer Water quality Regulatory issuesSurface water loop Very good transfer Size Temperature limitationsRenewable Energy for Heat In Winter Heating energy provided to the building. For each increment of 4 kWh required for heating (COP 4.5):Renewable Energy used for the total comfort need of the building: 77% 3.5 kWh renewable+ 1.0 kWh utility 4.5 kWh required 3.5 / 4.5 = 77%From renewable sourceRenewable Energy for Cooling In Summer Cooling energy provided to the building. For each increment of 4 kWh required for cooling (COP=4):Renewable Energy used for the total comfort need of the building: 75% 5.0 kWh renewed1.0 kWh utility 4.0 kWh required4.0 / 5.0 = 75%From renewable sourcePros and consAdvantagesEnergy efficiencyLow life-cycle costSimplicityLow maintenanceWater heatingNo outdoor equipmentPackaged equipmentLower peak demandNo freezing in heating modeDisadvantagesFirst (capital) costLimited qualified designersMessy constructionGeographically limited contractorsSupply/demand => higher vendor markupsFreezingWhen the air is cooled at the evaporator of the heat pump, the air moisture condensates and freezesWhen cooling on the evaporator water condensates and freezesComponentsResidential traditional configuration (USA)Reversible heat pumpBlower enhanced freon-air exchangerComponentsHydronic SystemFloor heating or coolingHydronic system advantagesTraditional HP on airCOP = 3-15C55CHydronic system advantagesGeothermal HP on airCOP = 4.54C55CHydronic system advantagesGeothermal Hydronic HPCOP = 94CHydronic AdvantagesBetter ComfortHeating and Cooling needsHeating and Cooling load of a house can be calculated using energy softwareSizing and ConstructionPond Closed loopTypically 15 tons/acre (depth15-20 ft) or as high as 85 tons/acre for well stratified deep lakesSizing and ConstructionHorizontal Ground loop4 6 ft burial depthSizing and Construction Horizontal Ground LoopSizing and ConstructionNot recommended, use a software package to include interaction and long term dynamic behaviorGround CharacteristicsConductivityGround CharacteristicsSource: McQuay Geothermal Heat Pumps Design ManualUnit Conversion:1 Btu/(h.ftF) = 1.8 W/(m.K)1 Btu/(lb.F) = 4,420 J/(kg.K)1 lb/ft3 = 16 kg/m3Sizing and ConstructionVertical LoopTypically, a 300 ft bore hole provides 3 TonsSizing and ConstructionBut interactions and long term behavior are complex; use of software recommendedBetter case when balanced heating and cooling loadsSoftware PackagesAvailable software packagesDrilling is the main costDrilling cost: $5 to $10 per footPiping and GroutingThe grout aims to keep optimal conduction from the pipe to the groundGrout conductivity is very important. It varies from 0.8 W.m-1.K-1 to 2 W.m-1.K-1 MarketsGeothermal Heat Pump market in the USANb of IGSHPA certified installers per stateReferences and Companies to followWater Furnace Earth Energy Systems McQuay www.mcquay.comGeoexchange www.geoexchange.comClimate Master www.climatemaster.comWinery in Livermore equipped with geothermal heat pump and hydronic system. Source: Earth Energy Systems


View more >