water cooling of photovoltaic panels

8/13/2019 Water Cooling of Photovoltaic Panels

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Water cooling of Photovoltaic Panels

Photovoltaic cells loose efficiency as they heat up. [Citation Needed] To gain some extraperformance I have set up a water cooling system for our 1.!"# solar system. $o far% I&vedetermined this cooling can give an extra 1' ( 1)* electricity.

Total cost of the system to date is around +)''. #ith hindsight% I could pro,a,ly do it a little cheaper.

Initial testing

-y initial testing was done with a garden hose supplying water to cool our solar panels. The veryfirst tests were done with a garden sprin"ler to see what type of improvement could ,e achieved.rom this wor" it seemed that /1'* improvement was possi,le

The plot a,ove is one of the trials I conducted using a sprin"ler as the water source. Note howrapidly the cooling effect drops off. N0. The slight tail on the first trial is not usual% the near verticaldrop of the second is more typical.


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This wor" also showed that the output increased almost immediately as the water was applied fulleffect in a couple of minutes2 and the effect reverted almost as 3uic"ly ,ac" to ,aseline in 4 minutes2. 0oth lines on the plot were virtually vertical.

rom this I set up the garden sprays 5 guttering system to determine the physical setup and flowrates re3uired. This wor" indicated that I need ,etween ) and 6 75min for my setup 1' sprays 8 1'

dri,,ling2.

I then sourced a pump and set up the system as a whole.

Setup

The setup is 3uite simple. I have some standard garden sprays located at the top of my panels.These sprays are fed ,y a small 19 watt pump. -y panels are setup in two rows% with on top and 6,elow% with a small gap ,etween the rows say mm2.

I have put a layer of duct tape ,etween the rows so I can feed most of the water to the top row which

then runs down and across the lower row. I have a second delivery setup across the top of the lowerrow% ,ut it is now only delivering a very small amount of water ,asically dripping water onto thepanels% rather than spraying2.

There are :gutters: ,elow each row of panels% which run the water ,ac" to a sump tan". The gutterfor the top row really only catches water from the :odd: panel that doesn&t have a matching one inthe lower row.

I originally used a spare wheelie ,in as the sump% ,ut it crac"ed on the ,ottom. I don&t "now if therewas a fault with that particular ,in% or if they aren&t up to the ;o,.


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=n overview of our solar setup including water cooling.


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= shot of the spray system I&m using across the top set of panels. These are standard half circlegarden sprays. I&ve found a flow rate of ) to 6 75min is optimum for my setup.

= closer view of the sprays in action.


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The ;oin ,etween the two rows of panels. Note the duct tape to allow the water to run over thesecond row. There is also a second delivery system. This is typically only set to :dri,,le: water


6/18

This is the :guttering: system on the ,ottom row of panels. The top row has something similar. Theguttering is ;ust some metal A shaped material that I found at 0unnings. $ince then% a new 0unningshas opened in my area and they stoc" some cheap /+)5 length2 plastic proper gutter material thatwould ,e much ,etter than this.


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Profile:

This is ,rand new water pump P(!9F% high 3uality and relia,le. $uita,le for? =3uarium% solar(panelcirculate system% fountain% electronic refrigerator% water heater etc.

Features:

Bated voltage? 1)G HC

Bated current? 1.6=

Capacity? 75-in 111JP


9/18

The pump cost /+!' delivered.


10/18

This is a plot of the theoretical characteristics of this pump. It agrees fairly well with my o,servedflow rate.

N0. If this pump were insufficient for my needs% I would pro,a,ly loo" into purchasing a small 1)Gdiaphragm pump. There seem to ,e a num,er of them availa,le on e0ay. Their power consumptionis typically higher than this pump% ,ut their output is typically higher. Lou may ,e a,le to derate itand run it at a lower wattage and achieve the desired result.

New Pump

Anfortunately I managed to wrec" my original pump I cleaned a lot of ash from near,y grass firesfrom my gutters and allowed the water to run ,ac" to the sump. =pprently the fine gunge in the waterwas enough to sandpaper the motor spindle to death ?

I have since purchased a small diaphragm pump.

12 Volt, 4! "#min Pump c#w !$ PSI Pressure Switch Suits %aravans, &V,'griculture, Solar ( Water )ransfer


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)he 12 V*% permanent magnet motor is thermall+ protecte an splash proof

The Pump is a )(cham,er positive displacement% self priming unit

capa,le of ,eing run dry

7i3uid Temperature? 16'M @'MC2 -ax.

Priming Capa,ilities? 6 feet 1.) m2 suction lift

-ax Pressure? ! P$I

Inlet5Eutlet Ports? !59 hose ,ar,

#eight?'.@"g 1.)l,s2

Certifications? C =pprovals

Current Hraw? !. =mps

This new pump draws up to 6) #atts. This is ;ust over dou,le my previous pump% ,ut it is still lowenough to ma"e it ecconomical to run.

0elow are the characteristics of the new pump. It&s measured output of !75min is pretty close to thetheoretical value especially as that graph doesn&t ta"e viscosity into account2.

The small increase in output from the new pump is notica,le in the coverage from the sprays.


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The only


13/18

Performance

0elow are a couple comparisons of two consecutive days production with and without the watercooling. #e&ve had a considera,le amount of cloudy 5 rainy weather since I&ve set up this system% soit&s difficult to get good &sunny day& graphs for comarison.

The plot a,ove is for the first day that I had the actual pump the comparison day is actually from theprevious wee"% not the previous day% that may explain the slightly different underlying curve2. I didn&tturn the pump on till around 1'?!' =-. prior to that I did some wor" on the system to reduce somephysical losses. Huring this time I was physically ,loc"ing a portion of some of the panels. The ;umpin production can ,e clearly seen when the cooling was started. The total improvement in output forthe day is ;ust over >*.


14/18

This is a plot from another pair of consecutive days. 0oth days were pretty good till lunch time% thenthe clouds came in. It&s a little hard to see from this graph% ,ut my perception is that even when thereare clouds comming past% the :re,ound: is much greater with the water cooling. or example%without cooling I would rarely see a spi"e O 1%6'' watts% with cooling spi"es of 1%'' ( 1%@'' areregular% and O 1%'' is not unheard of. 0asically% I ,elieve I&m still getting a significant ,enefit evenon relatively cloudy days.

I record the PG output to a data,ase at 1 minute intervals. I have run some data,ase 3ueries to3uantify the improvement. I compared the averaged output for the same minute periods each daywhere ,oth were producing over '' watts ie not in heavy shadow2.

'verage increase -watts. Percentage increase

1' 1!*


15/18

I have also run some :spot: tests to determine the output change caused ,y the water ,eing turnedon or off.

)ime of a+ /n # /ff Intial watts Final Watts Percent change Notes

1@?6 En @'> @>9 1).9* Pump 5 sprays

1@?'' Eff >!' 9) 1).* Pump 5 sprays'9?'' En !' 6)' 11.>* Pump 5 sprays

1!?1' En 1)1' 1!' 1'.6* $prin"ler

1!?) Eff 1!'' 1)'' 9.!* $prin"ler

1!?' En 11@' 1)' 9.* $prin"ler

16?1 Eff 1)@' 11' >.@* $prin"ler

These results tend to indicate that around 1'* or more production can ,e achieved at virtually anyproduction level% not ;ust pea" production times. To me that indicates I can hope to get a 1'*improvement on my annual production not ;ust pea" production2.

I intend to run some further tests when we get some sunny days having the water alternating on offfor 1 or !' minute intervals.

/n0/ff cooling trial

I was finally a,le to do an on5off cooling trial to try and see how the effect went throughout the day.$ee ,elow?


16/18

Huring this trial I ran the cooling !' minutes on 5 !' minutes off from 9?!'=-on. ven at 4 '' #atts output% the system made ,ac" ) #atts% which ismore than the pump cost 19#atts2.

)ime /n # /ff 'ctual &eaing &eaing # st &eaing *ifference *ifference

'9?!' Eff En 69 1' ) .1*

'>?'' En Eff @!' @9' ' .>6*

'>?!' Eff En @' 1' 6' .>*

1'?'' En Eff >1' >9' ' .@>*

1'?!' Eff En >!' 1''' ' .!*

11?'' En Eff 116' 1'@' 9' .*

11?!' Eff En 1'@' 116' 9' .*


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1)?'' En Eff 11)' 1)!' 11' >.9)*

N0. =t this time we had a significant afternoon shading issue which has since,een rectified.

Future improvements

3ottom gutter

The original small ,ottom gutter has now ,een replaced with larger normal plastic guttering. This iswor"ing much ,etter and there is no longer any physical losses of water missing the guttering andrunning onto the ground.

The gutter I have there at the moment is not really the ,est. It is a little too small it&s fine for the,ottom of the first row2. $ome of the water either tea(pots ,ac" around the solar panel or :;umps:over the guttering. I have some duct tape in place a the moment to minimise this.

= ,etter solution would ,e some cheap plastic guttering that I&ve seen at the hardware shop. Thisguttering is significantly wider so missing the gutter would no longer ,e an issue.

*uct tape

The duct tape I&ve ,een using was a pretty old 5 cheap roll. This tape isn&t very AG sta,le and it tendsto unstic" after a while. I should get some ,etter tape for this system% especially the ;oint ,etweenthe two rows of panels.

Water eliver+ s+stem for top row

There are ) sprays per panel set up. The water tends to run in a )'() cm wide stream from each.This means that the water covers only a ,it over '* of the panel surface. = little more coveragemay ,e advantageous% although only slightly.

I could pro,a,ly loo" at different setups so that I get ,etter coverage. Possi,ly ,y having a :dripper:tu,e running across the top of the row with a num,er of drips per panel instead of the sprays.

N0. #hen I originally experimented with this system using a garden hose as the water source2. Ididn&t get much% if any% improvement when I increased the water flow. I suspect that even thoughthere isn&t total coverage% the water is still removing a significant proportion of the heat from thesystem. The top covering is still warm to the touch ,ut not hot2 where there is no water% ,ut that isn&tthe top of the actual PG cell. I suspect that the water is removing a significant amount of the heatfrom the actual PG cells ,elow% even though it isn&t directly a,ove them.

%omputer control of pump

Qaycar has a remote switch "it availa,le http?55www.;aycar.com.au5productGiew.aspRIHKFC6!SC=TIHK)SformKC=TS$A0C=TIHK99. #ith one of these it would ,e possi,le tohave a 1)G relay control the pump. I also ta"e readings from the inverter each minute. I could stopthe pump if the monitoring PC determined that there wasn&t enough output to ma"e it worth while.
http://www.jaycar.com.au/productView.asp?ID=KC5473&CATID=25&form=CAT&SUBCATID=588http://www.jaycar.com.au/productView.asp?ID=KC5473&CATID=25&form=CAT&SUBCATID=588http://www.jaycar.com.au/productView.asp?ID=KC5473&CATID=25&form=CAT&SUBCATID=588http://www.jaycar.com.au/productView.asp?ID=KC5473&CATID=25&form=CAT&SUBCATID=588


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This is a low priority ;o, as the cooling does seem to give ,enefits unless there is very heavy cloudor it is actually raining.

water cooling of photovoltaic panels

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