Solar Water Heaters design

1 Solar Water Heaters designgXavier Vallv , TTAS painpSolar Thermal EnergySolar energy is the most plentiful energy source in LebanonSolar Thermal EnergySolar radiation incident at 40 (kWh/m2 mean average monthly day)TripoliNabatiye et TahtaZahl Beirut34 20'37" North, 36 0'25" East, Elevation: 1382 22'59" North, 35 26'59" East, Elevation: 403 50'34" North, 35 55'8" East, Elevation: 935 52'57" North, 35 30'46" East, Elevation: (gyy)- Very regular all year-round-Average energy (4 meteo stations).

2 5,15 Solar hour peak/day-12 % more than Barcelona (Spain) (4,5 Hp) and 31% (3,51 Hp) Hp) and 31% (3,51 Hp) more than Munich (Germany) A Hp year5,13 5,18 5,29 5,01 Solar Thermal Energy Applications Hot Water SpaceheatingSpaceheating Solar cooling Swimming poolsSolar Water heating Primary circuit : CollectorsarrayCollectors array Closed circuit Pump and expansion tank Regulation Heat exchangerSolar Water heating Solar Tank.

3 ExternalorinternalheatexchangerExternal or internal heat exchanger Vertical cylinder Corrosion resistant material Thermal insulation Thermal sensor and termometerSolar Water heating Auxiliary heater : Boiler SlkhibfHW consumption Solar tank as a pre heating before the boiler Solar tank as a pre heating of the pgSW tank heated by the boiler / or the modulant boilerCold waterSolar Water heating Solar control Al2hl(hf At least 2 thermal sensors (at the top of Solar collector and the bottom of the Solar tank) The circulation pump turns on/off depending on temperature differential between both sensorsSolar collectorsSolar collectorsFlatplateFlat plateEvacuated tubeFl t l tFlat platecollectorFlat plate collector heat balance: solarradiation Solar radiation absorption, thermal losses useful heatSolar Flat Plate collectorSolar Flat Plate collectorFlat plate collector efficiency characterization Optical losses Thermal losses (depending temperature difference between absorber and ambient) Solar Flat Plate collectorSolar Flat Plate collectorDifferent collectors efficiency characterization unglazed glazed flat plate selective coat evacuated tube Solar Flat Plate collectorAbsorber design : grill shape, Solar Flat Plate collectorserial grill, and meander shapeThe flow per square meter is different in these three designsSolar Flat Plate collectorMost Solar flat plate collectors are around 2 m2.)

4 But also larger Solar collectors of 7, 10 or more m2 adequate for big installations: fewer connections, less Solar Flat Plate collectorqgthermal of large flat plate collectors Distance from obstaclesDistance from obstaclesd = h / tan d = (L sin ) / tan D = h x k Lebanon: 33 NSolar Flat Plate collectorSolar Flat Plate collectorCEDRO minimalperformance requirements optical efficiency: 0,7 thermallosses:5,5W/m2 Kthermal losses: 5,5 W/m2 KIf available space is not enough, a higher performance collector can be used optical efficiency: 0,79py, thermal losses: 3,21 W/m2 KSolar collectors mountingSolar collectors mountingStrong wind can destroy Solar installations if the structure or blocks that titsupport per gravity are undersizedStructure and pipingStructure and pipingPi ilthhllbPiping lengths shall be minimized to reduce heat losses and pressure drop (lowerthan40mm wc /m)(lower than 40 )

5 The flow speed shall be calculated in the range of 25 3m/s2,5 3 ttll d hllThe total load shall guarantee no risk of wind uplift of the Solar collectors / support co ecto s / suppo tframes for wind speeds up to 120 piping insulation protectionOutdoor piping insulation protectionAluminum sheetFlexible plastic sheetPaint coatCll t tiserialCollectors connectionparallelse aBlblNoBalance by valvesBalance by reverse returnCll tCollectorsBalance by valvesBalance by reverse returnCoupling and connection terminalsThreaded coupling for connecting t bes or accessories conicalCoupling and connection terminalstubes or accessories conical pressure, expansion absorberPrimary circuit Piping: cooper or stainless steelPrimary circuit Slope at least 1% for drainage preferable without airlocks Pipe diameter sizing: pressure drop < 40 mm w c per lineal meterPifld2/(i d )3/(d) Pipe flow speed: 2 m/s (indoor), 3 m/s (outdoor) Flow rate: usually 50 l/h per m2 of collector (refer to collector manufacturer) Thermalinsulation:20to30mm(indoor)and30t o40mm(outdoor)Thermal insulation: 20 to 30 mm (indoor) and 30 to 40 mm (outdoor) Insulation protection against UV radiation and mechanical erosion (outdoor pipes) The thermal transfer fluid non freezing under the colder local event.

6 Safe for the use in such applications and environmentally suitable . All circuit components shall resist the maximum design temperature (valves, air vents, etc.)Heat exchangerHeat exchangerSolar tankSizing: its rated power shall be no less of 500 x collectors heat exchangers shall be suitable selected and installed to optimize the heat transfer efficiency and easy to remove for periodic cleaning. Solar hot Water tankSolar hot Water tankSolar tank characteristics Good thermal insulation Height > than diameter and vertically installed External protection Heat exchanger: internal or externalInternalsurfaceprotection Internal surface protection Anticorrosive deviceSolar hot Water tankSolar tank locationAsclosetothesolararraythanpossib leSolar hot Water tank As close to the Solar array than possible Better inside a technical room than outdoorThe tank insulation polyurethane with minimum thickness of 50 mm Solar hot Water tank WhenmorethanonesolarSolar hot Water tankWhen more than one Solar tank is necessary, they are connected in seriesRegulationRegulationSolar collectorsB1B1turnsonwhen TT1T2>e47 CB1 turns on when T = T1 T2 > ex.

7 4 7 CB1 turns off when T = T1 T2 < ex:1 2 C)RegulationSolarRegulationSolar collectorsB1B1B2B1 turns on whenSolar radiation is > ex. 300 W/m2B2 turns on when T = T1 T2 = ex: 4 C)B2 turns off when T = T1 T2 = ex: 2 C)MonitoringCalorimeterMonitoringFlow meterCalorimetersMeasure Solar energy producedCalorimetersMeasure Hot Water energy consumedtcVQe = Data logging and performance indicatorsData logging and performance indicatorsAnti legionella circuitAnti legionella circuitThermal treatment against the legionella bacteria The legionella bacteria is harmful when inhaled via micro droplets or aerosol (example atashower)at a shower) The optimal development temperature for the legionella bacteria is 35 37 C, but can reproduce between 25 and 45 C.

8 At 70 C or more is destroyedhli lliklhlfhillii To prevent the legionella sickness a regular thermal treatment of the HW installation is recommended (is compulsory for public buildings in many countries) A specific recirculation circuit is needed to transfer hot Water from the boiler tank to the lkllhlsolar tanks untill 70 C degrees are attained. Sometimes these temperatures are also reached with Solar energyCEDRO SHW reference hydraulic schematicsSolar collector arrayTe mperature CEDRO SHW reference hydraulic schematicsReversed returnMixing valvepsensorPrimary circuit HW consumption and recirculation looppumpBooster pumpSolar tanksExisting HW tankBoilerSports arena: hydraulic HW litres/day [235 users]f=35%.Sports arena: hydraulic schematicsSports arena: Solar collectors and heat dissipationSports arena: Solar collectors and heat dissipationSports arena: Solar tanks and pumpsSports arena.

9 Solar tanks and pumpsHeat dissipationPassive dissipationWhen the maximum Solar tanks temperature is reached, the circulation pump turns off and Heat dissipationActive dissipation p,ppa heat dissipation may be necessaryReference values for a SWH modelGENERAL SPECIFICATIOND emandDaily hot Water demand ( Rated output temperature 60 C)2200 L/daySolar arraType Flat-plate Tilt/orientation45 5 /0 20 SSolar arrayTilt/orientation45 5 /0 20 STotal collector area(1) 45 m2 Piping systemPrimary circuitPressure drop 40 mmwcFlow velocity2,5-3 m/sSdiiPd40 Secondary circuitPressure drop 40 mmwcFlow velocity2,5-3 m/sPumpFlow2025 L/hPressure drop6 mwcHot Water TankNumber/Capacity 1/2000 L; 1/100 LConnectionSeries invertedInstalled capacity3000 LExpansion tankVolume ~ 160L Heater exchangerExternal~ 32 kW Minimum Data logger and processorPerformance evaluation: temperatures, Water consumption, Solar energy produced, energy balance, reference radiation and ambient temperature.