Geothermal Energy Geothermal Heat Pumps

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Geothermal Energy Geothermal Heat Pumps. San Jose State University FX Rongre March 2009. 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

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<ul><li><p>Geothermal EnergyGeothermal Heat PumpsSan Jose State UniversityFX RongreMarch 2009</p></li><li><p>District HeatingDirect use of geothermal hot water</p></li><li><p>Heat Conduction in the GroundOne-dimensional Conduction equation is:</p><p>Along the year, the surface temperature is a sinusoidal function:</p><p>The analytical solution is:</p></li><li><p>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 J.kg-1.K-1 k = 1.5 W.m-1.K-1</p></li><li><p>It depends on annual average temperatureGround Temperature at 10m</p></li><li><p>Average Annual Temperature</p></li><li><p>Heat-Pump/ChillerA Heat-Pump as a Chiller transfers heat from the cold source to the hot source using compression to change the evaporation/condensation temperature</p></li><li><p>lnP-h DiagramHeat-Pump cycleValve</p></li><li><p>Geothermal Heat Pump Two types of exchangersVertical loop More expensive Reliable Smaller foot-printHorizontal loop Less expensive May be perforated Large foot-print</p></li><li><p>Geothermal Heat PumpOne can also use the aquifer or a pondOpen water loop Excellent transfer Water quality issues Regulatory issuesSurface water loop Very good transfer Size Temperature limitations</p></li><li><p>Renewable Energy for Heat In WinterHeating 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 source</p></li><li><p>Renewable Energy for Cooling In SummerCooling 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 source</p></li><li><p>Pros 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 =&gt; higher vendor markups</p></li><li><p>FreezingWhen the air is cooled at the evaporator of the heat pump, the air moisture condensates and freezesWhen cooling on the evaporator water condensates and freezes</p></li><li><p>ComponentsResidential traditional configuration (USA)Reversible heat pumpBlower enhanced freon-air exchanger</p></li><li><p>ComponentsHydronic SystemFloor heating or cooling</p></li><li><p>Hydronic system advantagesTraditional HP on airCOP = 3-15C55C</p></li><li><p>Hydronic system advantagesGeothermal HP on airCOP = 4.54C55C</p></li><li><p>Hydronic system advantagesGeothermal Hydronic HPCOP = 94C</p></li><li><p>Hydronic AdvantagesBetter Comfort</p></li><li><p>Heating and Cooling needsHeating and Cooling load of a house can be calculated using energy software</p></li><li><p>Sizing and ConstructionPond Closed loopTypically 15 tons/acre (depth15-20 ft) or as high as 85 tons/acre for well stratified deep lakes</p></li><li><p>Sizing and ConstructionHorizontal Ground loop4 6 ft burial depth</p></li><li><p>Sizing and Construction Horizontal Ground Loop</p></li><li><p>Sizing and ConstructionNot recommended, use a software package to include interaction and long term dynamic behavior</p></li><li><p>Ground CharacteristicsConductivity</p></li><li><p>Ground CharacteristicsSource: McQuay Geothermal Heat Pumps Design Manual</p><p>Unit Conversion:1 Btu/(h.ftoF) = 1.8 W/(m.K)1 Btu/(lb.oF) = 4,420 J/(kg.K)1 lb/ft3 = 16 kg/m3</p></li><li><p>Sizing and ConstructionVertical LoopTypically, a 300 ft bore hole provides 3 Tons</p></li><li><p>But interactions and long term behavior are complex; use of software recommendedSizing and ConstructionBetter case when balanced heating and cooling loads</p></li><li><p>Software PackagesAvailable software packages</p></li><li><p>Drilling is the main costDrilling cost: $5 to $10 per foot</p></li><li><p>Piping 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 </p></li><li><p>ExamplesSan Francisco City College</p></li><li><p>MarketsGeothermal Heat Pump market in the USANb of IGSHPA certified installers per state</p></li><li><p>Source: Geothermal Energy Association http://www.geo-energy.org/aboutGE/potentialUse.asp</p></li><li><p>MarketsMarkets will grow fast</p><p>Incentive programsSource: P. HUGHES Geothermal (Ground-Source) Heat Pumps: Market Status, Barriers to Adoption, and Actions to Overcome Barriers ORNL/TM-2008/232 Dec 2008Database for State Incentives for Renewables &amp; Efficiency http://www.dsireusa.org/</p></li><li><p>References and Companies to followWater Furnace www.waterfurnace.com Earth Energy Systems www.eartenergysystems.com McQuay www.mcquay.comGeoexchange www.geoexchange.comClimate Master www.climatemaster.com</p><p>Winery in Livermore equipped with geothermal heat pump and hydronic system. Source: Earth Energy Systems</p></li></ul>