Lister Engine Forum

How to / DIY => Everything else => Topic started by: guest22972 on December 29, 2018, 02:43:30 AM

Title: Panel Cooling.
Post by: guest22972 on December 29, 2018, 02:43:30 AM

Way too hot here to go work in the shed on any engines but I have  been playing with the solar stuff again and thought I'd start another topic on that to bore you all.

I have set up 5 x 250w panels on a garden bed I just stripped, ploughed and leveled. They are in series so I could test an inverter I ( successfuly ) repaired.
Being 40+ here today, I noticed my inverter was only outputting about 840W.  seemed a bit low for 1.25 Kw of panels in the middle of summer at close to midday.

With the garden hose nearby I decided to put something to the test and gave them a good spray.  Going straight back to the meter I noticed I was now getting about 1030W although it was falling pretty fast.  Go back out 20 Min later and I'm back down to 840w again.  There sure is a fall off when these panels get warm.

I have read people saying that this is due to the magnifying effect of the water droplets but I don't think there is much to that.  I spose I could set up a test and spray the back of a panel and see the difference in output but I think I'd still see a significant jump.  I did not think I'd see a near 200W jump though.

This solar generation has so many inefficiency it's a wonder it works at all. If they can in years to come  overcome a lot of these things there will be great gains to be made.
Title: Re: Panel Cooling.
Post by: old seagull man on December 29, 2018, 08:50:28 AM
My best output days in Brisbane are cool clear sunny days when the panels are cold or only warn, the hotter the panels the less the output.
Remember the specifications output is at 20C on a perfect day, when the panel is new and you have just won the lotto for the third time this week.
Plus most inverters don't like to be over about 35 C or they cut output.
Today the highest output from the 3060 watt array on the back of the house was 2876 watts,  18 x 170 watt panels,  making 19.7 kwh so it not bad.
Title: Re: Panel Cooling.
Post by: mike90045 on December 30, 2018, 01:58:13 AM
The amperage of solar panels is dependent on the "brightness" of the sun
The Voltage is dependent on the temperature, cooler is higher voltage, warmer is lower voltage.

That's why all the panel "string calculators" want to know the record low temps in your area, as the temps drop, the voltage of a string can go way up - enough to fry a controller.
Title: Re: Panel Cooling.
Post by: mike90045 on December 31, 2018, 03:44:14 AM
AC line voltage variation is mostly about local generation, local consumption , and the resistance in the run from the inverter to the pole transformer.
 Low local consumption on a cool sunny day, will produce higher line voltage.  Add some local usage, and the line voltage will go down.
  This is becoming a problem with neighborhoods with lots of solar, nobody really cares/notices with low line voltage, your fridge does not fault out, but the safeguards in GT inverters, when the line voltage goes up, they start shutting down as individual voltage sense goes over the threshold.
Title: Re: Panel Cooling.
Post by: AdeV on December 31, 2018, 10:27:16 AM
The birds, mainly those Indian minor pests seem attracted to them. ...  I can see them jumping about and squawking in distress but takes some of them a long time to fly off.

Doesn't that lead to a bit of a bird shit problem (I presume the crap when in distress, like most animals  :o); given the high temperatures, I imagine it gets baked on in seconds....