my diy pv set-up

[jwxr7]

Solar power rules

[jwxr7]

I need to come up with some sort of water cooling system for my array. These hot sunny days aren't producing nearly as much power as I expected. The panels are getting very hot and this lowers thier efficiency.

[Daox]

Is there any commercially avaliable solution for this problem?

[groar]

"Albedo" may be a part of the solution : find something clear that reflect the sun and cover the ground around the panels. Not only the panels will receive more indirect light, but the surrounding will be more cool and the panels less hot.

Hope I'll be able to take picture of what we installed lately to shade the office bay and the kitchen window. Not only they permit the office and the kitchen to not be hot, but the ground is more cool so the air at the base of the panels. I have only the feeling that it helps a little in my case, but I'm working on trying to find the way to show it without having to remove the shades.

Ventilation is also important. This is noticeably important for roof integration as I have and as it's privileged in France by better buying rates. Finding a more ventilated place could be a solution.

Water is certainly bad as it will make things to depose on the panels and will not remove so much heat. A way to remove more heat with water would be to mist it (make very small drops that instantaneously evaporate and absorb "a lot of" heat).

At least don't put them under some trees as I have seen it in a US TV series lately

Denis.

[jwxr7]

Is there any commercially avaliable solution for this problem?

I'm not sure, I haven't researched it too much yet. I will be looking though.

Thanks for the ideas Denis.
I don't think the area around the panels is getting too hot being vegitation mostly. Putting down white stone would probably help though, it would also keep the weeds down. I'm not sure I'm ready to commit to this location that much yet, with all the work putting stone down.

There are lots of minerals in our water, and I can imagine they would build up wherever it evaporates. That makes things difficult for misting or trickling. I suppose a network of tubes touching the back side of the panels with water flowing thru them could help, but isn't very practical or efficient. Maybe misting the back surface is an option, I just don't like the idea of putting moisture on all the wiring and inverter stuff back there.
I think a good first step would be to cut back the weeds around the area of the array for better ventilation. This needs done again soon anyway to eliminate shadows, but I'll clear even farther away than needed for that.

These long hot sunny days have only been giving me 1200 watt hours or so, and I know that isn't nearly as good as it should be doing .

[jwxr7]

Here's the #s for June 2009;
total monthly production was around 27.42kwhrs.
averaging 914whrs per day.
Not as good as it should be considering the amount of sun we recieved.
I cut down the weeds around the array for 20 feet or so to help with ventilation on the 28th of june. Hopefully this will help cool the set-up some and get the #s up a bit.

[groar]

About your low numbers for June, which is the max instantaneous you could notice between 11 and 15 ?

Your output from the panels may be greater than the maximal input of your inverter. The inverter can then limit the input to the allowable max, or simply put itself in security and produce no output until the input is acceptable.

The efficiency of the inverter isn't a constant and isn't maximal at maximum input.

Denis.

[jwxr7]

I'm not sure what you mean by

which is the max instantaneous you could notice between 11 and 15 ?

? Is 11 and 15 the time, like between 11 am and 3 pm?

In the winter i have observed the panels maxing out the inverter. It would hit 204 watts and not climb anymore. On several occasions during hot sunny days I checked the inverter output, but it was only about 120 watts. I would have expected it to be maxed out under those peak solar conditions. I remember one day feeling the panels with my hand. They were extremely hot. Aren't the polycrystalline type like mine effected more by temperatue? I also felt the inverter and it wasn't too bad.

The suns path thru the sky is actually quite far north in the morning and evening too. Making me want to angle my array that way slightly, or at least go totally flat. They seem to recommend this for lower lattitudes, but not mine.

[jwxr7]

I just checked my inverter output at 5pm. It said zero watts. It's nice and sunny, but later in the day, not so late as to cut off output. It shows that the array logged around 640 watt hours for the day (not too impressive). I went out and the inverter was cool to the touch, panels were quite warm. I opened up the DC junction box and the array voltage was around 46 volts. I checked each panel and they were between 11.5 and 11.75 volts. The middle ones were lower than the outer ones (heat related?). I thought about experimenting with some water cooling but it's late enough that the sun may not be at a good angle for the test. Maybe tomorrow I'll try something during peak solar conditions. I hope the glass can take the rapid temp change (I'm sure they are tempered). I also suspect the array angle some, but if cooling brings the voltage up dramatically, I'll drop that suspect.

[jwxr7]

I checked output again at 7pm and it was making 45 watts or so . Array angle isn't the problem. Went out and felt the panels, they were fairly cool now, the inverter felt the same as earlier. Got under the array and checked the array voltage, I think it was around 38 volts . Now that made me go back and check the input parameters to my inverter. It looks like the info I printed off gives the minimum DC input voltage as 44 volts. So what the heck is going on? I might be having some kind of inverter issue. It should have been producing earlier when it was in the 46 volt range, especially if it was working below 40 volts just a while ago. I'll have to do some connection checking.