solar compressor system – 0.5hp 120vac – test report · pdf file ·...

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Date:1-26-2016

SolarCompressorsystem–0.5HP120Vac–TestReport

ThisreportquantitativelydocumentsthetestedperformanceofasolarairpumpingsystemconsistingofaspecificACaircompressorpoweredbysolarPVpanelsinconjunctionwithaPicoCellcontroller. SolarPVpanelsaretheDC input for thePicoCellcontrollerandthesinglephaseACaircompressor is connected to thePicoCell’soutput, as shown inFigure1below.SolarPVpanels areconnectedinseriesinordertoprovidetherequiredDCsolarpowertothePicoCellcontrollerthatisgeneratingtheappropriateACoutputforaspecificACaircompressor.

The PicoCell controller can be used for running any AC air compressor from solarindependent of phase, voltage and frequency. For a given air compressor specification, PicoCell iscapableof generating a true sinewavewith a variable frequency rangeof30-60Hz.Byvarying thefrequency, PicoCell controls the compressor’s speed in the range between 50 and 100% of ratedspeed,dependingon thepoweravailability fromthesolarpanels (PV input). Italsoprovidessoftstartfunctionality,whichcandramaticallyextendthelifeofthemotorandcompressoritself.

Figure1:SolarACpumpingsystemdiagram

In this particular setup, a 0.5HP, 120Vac, 60Hz, single-phase (2-wire) air compressor wastestedwiththePicoCellcontrollerpoweredby3-5standard(60cells,230-270W)PVpanelswiredinseries.ThetechnicalspecificationoftheACaircompressorisprovidedinthetable1.

Table1:TechnicalspecificationoftestedACpump:

GASTaircompressor:Jun-Air87R640-101-N470X

Power:0.5HP Voltage:120V Current:6A Frequency:60Hz

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/ Maxflow:4.253scfm Speed:1725rpm MFG#N470NXInterpretingtheloadcurve:

TheACaircompressorwastestedfor6differentpressures(heads)versusflowversussolarPVpowerasshowninFigure2.Ittakesaround200Wtostartacompressor,anditsperformanceinairflowbasedontheinputpower,foragivenpressure,isshowninthefigure2.

Forexample,for300Wofinputsolarpower,ifthecompressor’sbackpressureis30psi,thenitprovidesanairflowofjustabove2scfm,whileifbackpressureis20psi,thenitprovides3scfmofairflow;butifthebackpressureisonly5psi,thentheairflowis4.5scfm.ThissolarpowerismeasuredasaninputtothePicoCell,drivingthecompressor.

Figure2:0.5HP,120VacSolaraircompressorspecification–airflowvs.solarpowerfordifferentpressures

SameperformancecurveofsolarpoweredACaircompressorcanbepresentedasonfigure3, which shows standard air flow versus pressure graph, but for different power inputs to thePicoCellcontroller. If inputpowerisonly300W,theair flowat20psi is2.75scfm,but fortheinput

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powerof400W,theairflowbecomes3.25scfm,whilefor500Wofinputpower,theairflowimprovesmarginally.Thus,theinputpowerforthesolaraircompressorsystemshouldbeat least500W,foraircompressortoprovideoptimalperformanceatalltimes.

Figure3:Performanceofsolarpoweredaircompressorfordifferentpowerlevels

Dependingonthelocationwherethissolaraircompressorsystemisinstalled,itwillrequiremoreor less totalPVcapacity toachieve these results. Thereare6 solar zones thatare shown inFigure3.Zone6hasthemostsolarinsolation(6-7kWh/m2/day),whilezone1hastheleastamountofsun(1-2kWh/m2/day).

Figures 5-7 show the cumulative daily hours of operation for different solar PV installedpower,fordifferentworldinsolationzones.Therearethreeexamples,wheresystemcanbeinstalledwith 3, 4 and 5 solar PV panels, and hence the total hours of operation will differ, for differentworldwidezones.

Forexample,fromfigure5with750Wofinstalledpower(3solarPVpanels),lookingatzone

6, for backpressures of 25psi, the system operates almost 8 hours per day. However, at zone 3(whichisMontanaare),samesystemwouldoperateonly5hourswithbackpressureof25psi,whileatzone2,atthesamebackpressure,systemwouldoperateonly3hoursduringtheday.

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Figure4:SolarinsolationzonesintheWorld

Figure5:Dailyhoursofoperationfor750W(3PVpanels)solarinstalledcapacity

If the site is in Montana (zone 3), and 5 hours of daily operation is not enough, then by

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adding1PVpanel(1000Wsystemcapacity),thenewoperatingtimeis7.5hours(Figure5),whileadding 2 additional panels (1250W system capacity), the operating hours can go to8.5 hours ofoperationperday(figure6).

Figure6:Dailyhoursofoperationfor1000W(4PVpanels)solarinstalledcapacity

Figure7:Dailyhoursofoperationfor1250W(5PVpanels)solarinstalledcapacity

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