Sizing of solar cooling systems

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Sizing of solar cooling systems

  1. 1. funded byChapter C : Predesign – system sizingSpeaker: XXXX YYYYYTraining course on solar coolingChapter C : Predesign – system sizing 2System sizingConvectionHygienic airInternal loadIrradianceSource : TECSOLA) Building load characterisation needed
  2. 2. Chapter C : Predesign – system sizing 3System sizingInternal loadsChapter C : Predesign – system sizing 4System sizing
  3. 3. Chapter C : Predesign – system sizing 5Solar collectors and thermally driven coolingdesiccantadsorption 1-effectabsorption2-effectabsorptionSAC = solar aircoll.CPC = stationaryCPCFPC = selectivelycoated flat plateEHP = evacuatedheat-pipeEDF = evacuated,direct flowSYC = stationaryconcentrated,Sydney-typeSAC = solar aircoll.CPC = stationaryCPCFPC = selectivelycoated flat plateEHP = evacuatedheat-pipeEDF = evacuated,direct flowSYC = stationaryconcentrated,Sydney-type0.00.10.20.30.40.50.60.70.80.91.00.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35∆T/G [Km2/W]ηcollSYCEDFFPCSACEHPCPCSource : Fraunhofer ISEA) Choice of technologiesChapter C : Predesign – system sizing 6Solar production0 25 50 75 100 125 150 1750,00,10,20,30,40,50,60,70,80,9flat-plateevac. tubeevac. flat-plateCPC-collectorparabolic troughIrradiation:800 W/m² direct normal200 W/m² diffuseefficiencyT - TAMB[K] 60 80 100 120 140 160 180 20001002003004005006007008009001000Barcelonaenergyyield[kWh/m²]temperature [°C]FPCEFPCETCCPCPTC60 80 100 120 140 160 180 20001002003004005006007008009001000Huelvaenergyyield[kWh/m²]temperature [°C]FPCEFPCETCCPCPTCFPC: flate plate collectorEFPC: flate plate collector with concentrating parabolic compound (CPC)ETC: vaccum tube collectorsCPC: vaccum tube collectors with concentrating parabolic compound (CPC)PTC: parabolic trough collectorSource : Aiguasol
  4. 4. Chapter C : Predesign – system sizing 7ProducedColdrFactoConversionConsumedEnergyalConvencionPEspec =conveleccoldeleceleccoldeleceleccoldelecelecconv,specCOP1QQ1Q1QQQPEεεεε====Specific Primary Energy (PE) (KWh PE/KWh cold):Conversion factor: Electricity – 0.36; Fossil Fuel – 0.9Conventional Compression Chiller:Source : INETIPrimary energy analysisDefinitionsChapter C : Predesign – system sizing 8towercooling,specthermalfossilsoltowercooling,speccoldheatdrivingfossilsoltowercooling,speccoldfossilsolheatdrivingtowercooling,speccoldfossilbackuptowercooling,speccoldfossilbackupsolar,specPECOP.)F-(1PEQQ)F-(1PEQ1)F-(1QPEQ1QPEQQPE+=+=+=+=+=εεεεεheatdrivingcoldthermalQQCOP =+=+===thermalelectercoolingtowspec,coldcoldtdrivingheaelectercoolingtowspec,coldelectedheatrejectercoolingtowspec,coldelectercoolingtowercoolingtow,specCOP11EQ)QQ(EQ1QEQEPEεεεεSolar Thermal Driven Chiller:With:Cooling tower:Source : INETIPrimary energy analysisDefinitions
  5. 5. Chapter C : Predesign – system sizing 90.00.51.01.52.02.50 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Solar Fraction for coolingPEspec,sol,kWhPE/kWhcoldCOP = 0.6COP = 0.8COP = 1.0COP = 1.2Conv 2Conv, 1Primary energy analysisCOPconv =2.5COPconv =4.5heat source:solar collector+ fossil fueledbackupprimaryenergyconversionfactor forelectricity:0.36primaryenergyconversionfactor forfossil fuels: 0.9heat source:solar collector+ fossil fueledbackupprimaryenergyconversionfactor forelectricity:0.36primaryenergyconversionfactor forfossil fuels: 0.9Source : Fraunhofer ISEChapter C : Predesign – system sizing 10Comparison between absortion and compressionEfficiency based on primary energy0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1solar fraction cooling00.511.52specific primary energy per unit of coldconventional systemthermal system,low COPthermal system,high COPno primaryenergysavingsaves primaryenergySource : Aiguasol
  6. 6. Chapter C : Predesign – system sizing 11! High solar fraction for cooling necessary for solar thermally driven coolingequipment with low COP which use a fossil fueled backup! A lower solar fraction is acceptable if thermally driven cooling equipment with ahigher COP is employed! An alternative is to use a conventional chiller as a backup (e.g. in case of a largeoverall cooling power)! Primary energy savings are always achieved using a solar thermally autonomoussystems but no guarantee for strictly keeping desired indoor comfort limits canbe given! In any case the use of the solar collector should be maximised by supplying heatalso to other loads such as the heating system or hot water productionConsequences of primary energy performanceChapter C : Predesign – system sizing 12DesignDesign with regard to solar-assisted air-conditioning mainly means! Selection of the proper thermally driven cooling equipment for theselected air-conditioning system! Selection of the proper type of solar collectors for the selected air-conditioning system and thermally driven cooling equipment! Sizing of the solar collector field and other components of the solarsystem with regard to energy and cost performance
  7. 7. Chapter C : Predesign – system sizing 13Design approaches‚Rules of thumb‘Collector cost per heatingcapacityCost of solar heat forgiven climateLoad - gain - analysis forgiven climate and loadAnual cost based on load-gain-analysisComputer design tool withpredefined systemsOpen simulation platformAccuracy,reliabilityofresults,detailsofdesigninformationRequiredsysteminformation,effortforparametrizationSource : Fraunhofer ISEChapter C : Predesign – system sizing 14Design pointdesigndesign,colddesign,collcollcollCOPPGA =η⋅⋅==>designdesign,collcollspecCOPG1A⋅η⋅=Example Gcoll = 800 W/m2hcoll,design = 0.5COPdesign = 0.7==> Aspec = 3.57 m2per kW cooling powerSource : Fraunhofer ISE
  8. 8. Chapter C : Predesign – system sizing 15+ Method allows a very quick assessment (guess) about therequired collector area, if the efficiency of the collector andthe COP of the thermally driven cooling equipment isknown– Method neglects completely the influence of the variationof radiation on the collector during day and year– Any information on the specific site and load is neglected– Method neglects completely part load conditions of coolingload in thermally driven cooling equipmentAdvantages and disadvantagesChapter C : Predesign – system sizing 16SizingSource : EAWAverage values of thespecific collector area" for Absorption- andAdsorption chillers3,0 to 3,5 m²/kWchilling capacity" for open technologies(DEC, liquid DEC):8 to 10 m² per 1.000 m³/hrated air flowrate
  9. 9. Chapter C : Predesign – system sizing 17Collector first cost⊥⊥−⋅−−⋅−⋅Θ=ηG)TT(cG)TT(cc)(k2ambav2ambav10⊥⊥⊥⋅η=⇒⋅η=⇒⋅η⋅=GkW1AGQAGAQ specuseuse&&specspecpower,heat CostACost ⋅=incidentanglemodifieropticalefficiencylinearheat losscoeff.quadr.heat losscoeff.average fluidtemperatureambient airtemperatureradiation oncollectorspecificcollector costSource : Fraunhofer ISEaverage fluid temperature = operating hot temperature of cooling systemChapter C : Predesign – system sizing 18Collector cost versus specific required area04008001200160020001 2 3 4 5 6required absorber area [m2/kW]collectorfirstcost[€/kW]evacuated tube flat plate flat plate - integrated roof stationary CPCTav = 75°CGcoll = 800 W/m2Source : Fraunhofer ISE
  10. 10. Chapter C : Predesign – system sizing 19Advantages and disadvantages+ Method allows a rough comparison of different solarcollectors, if the collector parameters and the operationtemperature of the thermally driven cooling equipment areknown– Method neglects completely the influence of the variationof radiation on the collector during day and year– Any information on the specific site and load is neglected– Method neglects completely part load of cooling load andthermally driven cooling equipmentChapter C : Predesign – system sizing 20Solar heat costannuityspecannual fCostCost ⋅=grossannualheatQCostCost =annualcollector costspedificcollector cost(€/m2)annuityfactorsolar heatcost (€/kWhof heat)collector grossheatproduction.dataicallogmeteoroatingmindotheofvalueshourlygsinucalculatedTypically.etemperaturoperationgivenaandsitegivenaatproductionheatcollectorannualQgross =Source : Fraunhofer ISE
  11. 11. Chapter C : Predesign – system sizing 21Solar heat cost0481216200 200 400 600 800 1000 1200 1400annual gross heat production [kWh/m2]heatcost[€-cent/kWh]etc fpc irc cpc Palermo, Tav = 75°CSource : Fraunhofer ISEChapter C : Predesign – system sizing 22Solar heat cost0481216200 200 400 600 800 1000 1200 1400annual gross heat production [kWh/m2]heatcost[€-cent/kWh]etc fpc irc cpc Palermo, Tav = 95°CSource : Fraunhofer ISE
  12. 12. Chapter C : Predesign – system sizing 23Simple software tool SHC (NEGST project)Only needs monthly cooling (heating) loadFree download in:http://www.swt-technologie.de/html/publicdeliverables3.htmlCompares monthly loads(heating and coling) withmonthly solar energygains.It is based onPHIBARFCHART Method- The results are primaryenergy savings forcolector area installed.Chapter C : Predesign – system sizing 24Advantages and disadvantages+ Method allows a good comparison of different solarcollectors using their parameters and the radiation data ofa specific site+ The maximum possible heat production of a specific solarcollector for a given site (annual meteorological data file)and a given constant operation temperature is determined– Any information about the load profile is neglected– Method neglects completely part load of cooling load andthermally driven cooling equipment
  13. 13. Chapter C : Predesign – system sizing 25meteo databuildingmodelcollectormodelsolar fractions forheating and coolingCOP, εheatloadsolar gains0501001502002500 100 200 300 400 500 600 700 800heating cooling 1 0.5 0.25 0.1! For each hour of the yearthe required heat forcooling (heating) iscomputed, e.g. usingbuilding simulation! Global efficiency factors fortransformation of heat incooling (heating) are usedto describe the technicalequipment! Calculation of hourlycollector gains usingdifferent operationtemperatures for coolingand heatingCorrelation of loads and gainsSource : Fraunhofer ISEChapter C : Predesign – system sizing 26Software tools needed to determine hourlycooling (heating) loads of a buildingTRNSYS – Commercially available(www.sel.me.wisc.edu/trnsys/)Energy plus – Download free(www.eere.energy.gov/buildings/energyplus/ )ESP-r – Download free(http://www.esru.strath.ac.uk/Programs/ESP-r.htm )A list of other software tools can be found :(http://www.eere.energy.gov/buildings/tools_directory/)
  14. 14. Chapter C : Predesign – system sizing 27Simple software tools using hourlycooling (heating) loadSACE Cooling evaluation light tool– available in http://www.solair-project.eu/218.0.htmlResults using this software tool while be shown latterChapter C : Predesign – system sizing 28Simple software tools using hourlycooling (heating) loadSolAC – available in:http://www.iea-shc-task25.org/english/hps6/index.htmlFour different units are considered in this software:• Solar system• Cooling device• Air handling unit• Cooling and heating components in the roomThe input data for theprogramme is:• weather data including solarradiation (hourly data)• load files including heatingand cooling loads (hourlydata)
  15. 15. Chapter C : Predesign – system sizing 29Dynamic simulation software tools usinghourly cooling (heating) load- System orientatedTNSYS - www.sel.me.wisc.edu/trnsys/ColSim - www.colsim.deInsel - http://www.inseldi.com/index.php?id=21&L=1- Building OrientatedEnergy plus - www.eere.energy.gov/buildings/energyplus/Software SolarComponentsACComponentsNewComponentsFreedownlaodOpensourcecodeTRNSYS Yes Yes Yes No YesColSim Yes Yes, but noclear list waspossible toobtain.Yes Not clear YesEnergyPlusYes Yes Yes Yes Not clearINSEL Yes Yes Yes NO NOChapter C : Predesign – system sizing 30Identification of HVAC components available which are most interesting forCTSSTRNSYS 16.Type 107 – Absorption Chiller (hot water fired, single effect)Type 51 – Cooling Towers.TESS LibrariesType 680 – Single-effect hot water-fired absorption chiller (Equivalent to type107 of TRNSYS 16)Type 679 – Single-effect steam-fired absorption chillerType 677 – Double-effect hot water-fired absorption chillerType 676 – Double-effect steam-fired absorption chillerType 683 – Rotary desiccant dehumidifier – models a rotary dessicantdehumidifier containing nominal silica gel.
  16. 16. Chapter C : Predesign – system sizing 31solargaselectcalderabombacalorabsorciócalefacciórefrigeraciósolargaselectcalderabombacalorabsorciócalefacciórefrigeracióSource : AiguasolCalculation methods :Estimated calculation with energy balancesSolar thermal energy availability• Simulation tool for the solar systems• “Infinite” consumption with high return temperature (chilled water)• 100% use of produced solar energyEnergy load determination, per year and per month: cold, heat, and DHW• Calculation tool for the building energy load• DHW energy load determinationUse factor determination• Depends on the relation availability / load• Depends on the heat storageDefinition of energy flows between subsystems• -> Definition of a control strategyChapter C : Predesign – system sizing 32Source : Fraunhofer ISE
  17. 17. Chapter C : Predesign – system sizing 33Guidelines for design, control & operationof solar assisted adsorption chillers00.10.20.30.40.50.60.760 65 70 75 80 85 90 95temperature, °CCOP,COPsol,etacoll2030405060708090coolingpower,kWetacoll COPCOPsol cooling powerCOPsol =COP * ηcollRadiation oncollector: 800 W/m2COPsol =COP * ηcollRadiation oncollector: 800 W/m2COP-maximumat about 70°CSource : Fraunhofer ISEChapter C : Predesign – system sizing 34Efficiency of solar thermal cooling systems0.000.100.200.300.400.500.6060 80 100 120 140 160 180 200Working temperature [°C]COPsolar5006007008009001000Irradiation W/m2==> optimalworkingtemperaturedepends on theirradiation levelSource : Fraunhofer ISE
  18. 18. Chapter C : Predesign – system sizing 35Evaluation parameter: Costs of savedprimary energy! Combined Energy-costs-Performance! enables comparison of different system designsCosts of primaryenergy saved=∆ Total annual costs∆ Primary energy∆primary energy = annual primary energy saving ofthe solar driven system compared to aconventional reference system∆primary energy = annual primary energy saving ofthe solar driven system compared to aconventional reference system∆total annual costs = annual supplementary costs of the solardriven system compared to aconventional reference system∆total annual costs = annual supplementary costs of the solardriven system compared to aconventional reference systemSource : Fraunhofer ISEChapter C : Predesign – system sizing 3610%20%30%40%50%60%55 65 75 85 95 105 115 125 135Storage volume, l/m2Primaryenergysaved160 180 200 220 240 260 280! Madrid! Officebuildings! Flat platecollector! Backup:Gas boiler! AbsorptionchillerCollector surface,m2Example: primary energy savings(in%ofthereferencesystem)Growing collectorsurfaceSource : Fraunhofer ISE
  19. 19. Chapter C : Predesign – system sizing 37140%145%150%155%160%165%170%175%180%55 65 75 85 95 105 115 125 135Speichervolumen, l/m2Jahreskosten,%Referenz160 180 200 220 240 260 280Kollektorfläche,m2ansteigendeKollektorflächeExample: annual costs! Madrid! Bürogebäude! Flachkollektor! Backup:Gaskessel! Absorptions-kältemaschine! Madrid! Officebuildings! Flat platecollector! Backup:Gas boiler! AbsorptionchillerGrowing collectorsurfaceCollector surface,m2Storage volume l/m2Annualcosts,%referenceSource : Fraunhofer ISEChapter C : Predesign – system sizing 380.120.140.160.180.20.220.240.260.2855 65 75 85 95 105 115 125 135Speichervolumen, l/m2KosteneingespartePE,€/kWh160 180 200 220 240 260 280Kollektorfläche,m2MinimumExample: Costs of primary energy savings! Madrid! Bürogebäude! Flachkollektor! Backup:Gaskessel! Absorptions-kältemaschine! Madrid! Officebuildings! Flat platecollector! Backup:Gas boiler! AbsorptionchillerStorage volume l/m2Collector surface,m2Costsofprimaryenergysaved,€/kWhSource : Fraunhofer ISE
  20. 20. Chapter C : Predesign – system sizing 39Dynamic modelling with TRNSYS… necessarySystem sizingChapter C : Predesign – system sizing 40Transient simulation – TRNSYSTRNSYS features– Numerical calculation methods– Continuous yearly simulation of the thermal behaviour of theinstallation, analysing the transitory phenomenon of the heatflows– Variability of climatology (temperature, irradiation) is taken intoaccount– Enables analysis of the different factors which determine theenergetic behaviour of the system # parametric study#optimisation
  21. 21. Chapter C : Predesign – system sizing 41TRNSYS WorkspaceTransient simulation – TRNSYSChapter C : Predesign – system sizing 42Results obtained with TRNSYSTransient simulation – TRNSYS
  22. 22. Chapter C : Predesign – system sizing 43Analysis of the results051015202530351 14 27 40 53 66 79 92 105 118 131 144 157TambTair01000200030004000500060007000Gener Febrer Març Abril Maig Juny Juliol Agost Setembre Octubre NovembreDesembrekWhMonthly heating demand in kWhTotal demand in kWhSolar contribution in kWhTransient simulation – TRNSYSChapter C : Predesign – system sizing 44Calculation options with dynamic simulation toolsSeparated calculation of building and cooling system– Step 1: Simulation of the building demand (heating, cooling)– Cooling system model= ideal system with infinite power.– Intermediate result: hourly data of heating and cooling demand.– Step 2: Simulation of the cooling system– Result: energy contribution of the real cooling systemCoupled calculation of the building and the cooling system– Simulation of the building (demand) and of the cooling system in thesame software– Cooling system model = real system– Results:• Energy contribution of the real cooling system• Degree of fulfilment of the comfort criteriaTransient simulation – TRNSYS
  23. 23. Chapter C : Predesign – system sizing 45Which questions have to be answered?1. Which is the basic sizing of the main equipments?• Collector field : type and size in m2• Absorption machine: kWf2. What is the solar contribution to the cooling, heating and global demand?3. Which is the basic sizing of the back-up system?• type (boiler, heat pump, air conditioner...);• size kW4. Which are the energy savings?5. What are the additional costs compared to a conventional installation?6. What is the pay-back time?Chapter C : Predesign – system sizing 46
  24. 24. Chapter C : Predesign – system sizing 47Sizing of the absorption machineffsolargensolargenfkWmmkWkWkWmkWkWkW 222332.015.065.0 ==××Demand peak < maximal total power (absorption + auxiliaries) + coldstorageOperating with solar energy: minimal power required to absorb thesolar heat produced and convert it into cold. # 3 m2/kWf– Criteria 1: the absorption machine is able to use the maximalsolar production. Solar peak production approx. 0.5 kW/m2(1000 W/m² x 50 % efficiency)– Criteria 2: the solar energy produced during the day of maximalirradiation can be totally used by the absorption machine,assuming that the required heat storage is available– Maximal power to guarantee a minimal solar contribution(typically > 60...70 %) and/or an reasonable number of operatinghours (> 1000 h/year).Rules of Thumb – pre-design rules ofsolar cooling systemsChapter C : Predesign – system sizing 48Sizing of the heat/cold storageCold storage– Cover demand peaks (smaller machines, larger number ofoperating hours)– Avoid part-load or intermittent operationHeat storage– Gap between cooling demand and solar heat availability– Guarantee continuous operation of the machine during days ofintermittent irradiation– Typical size: 25 .. 50 litres / m2 of collectorRules of Thumb – pre-design rules ofsolar cooling systems
  25. 25. Chapter C : Predesign – system sizing 49Control strategyStarting priority (cold production) according to the energy efficiency– Cold production with heat-pump in case of simultaneous heatdemand. Solar contribution for space heating.– Cold production with absorption through solar heat– Cold production with heat-pump (without heat recovery)– Cold production with absorption through gas boilerRules of Thumb – pre-design rules ofsolar cooling systemsChapter C : Predesign – system sizing 50System sizing75 – 95°C75 – 95°C25 - 35°C7 – 12 °C700W/m² 85 kW77 kW50kWf127 kW200 m²Source : TECSOL
  26. 26. Chapter C : Predesign – system sizing 51System sizing! 1 Cooling load : 50 kWc! 2 Inlet generator : 50 / 0.65 = 77 kW! 3 Cooling tower : 77 + 50 = 127 kW! 4 Primary loop efficiency : 0.9! 5 Heat load on collector side : 85 kW! 6 Average irradiance : 700 W/m²! 7 Collector efficiency : 0.6! 8 Collector area : 85/0.7/0.6 = 200 m²! 9 Optimal tilt : 30° (France South)! 10 Groung space necessary > 300 m²Chapter C : Predesign – system sizing 52Check list concept : example233Possible undersizement of solar system thanks toback up333Passives actions decrease potential223Yearly heating and DHW needs223Yearly adequation production <-> load133Daily adequation production <-> loadLoadTECHNICALFEASIBILITY333Adapted existing material (or planned) for back up233Adapted distribution network123Space for technical premices223Important area for solar collection333ClimateBuildingHotelPublic buildingIndustrySource : TECSOL
  27. 27. Chapter C : Predesign – system sizing 53455558TOTAL SCORE(on 63) :232Presence of a long term financed monitoringMonitoring223Regulat operation action possibilitiesFEASIBILITY223Skilled internal technical staffO&MORGANISAT.133Financial stability of building owner231National & international supports eligibility333Environmental action politics323Importance in term of marketing impactFEASIBILITY333Building owner motivationECONOMICAL133High investment capacityBuilding owner223Low water cost331High cost of saved energyCost of energyHotelPublic buildingIndustryCheck list concept : exampleSource : TECSOLChapter C : Predesign – system sizing 54DisclaimerThis training has been developed in the context of SOLAIR. SOLAIR is a European co-operation project for increasing the market implementation of solar-air-conditioningsystems for small and medium applications in residential and commercial buildings. Forfurther information on the project or on products of the project see: www.solair-project.euThe project SOLAIR is supported by the Intelligent Energy – Europe (IEE) programme ofthe European Union promoting energy efficiency and renewables. More details on theIEE programme can be found on: http://ec.europa.eu/energy/intelligent/index_en.htmlThe sole responsibility for the content of this training lies with the authors. It does notrepresent the opinion of the European Communities. The European Commission is notresponsible for any use that may be made of the information contained therein.
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