Alternative Technology Assn Forums

1. 

   Russell Moore
   Member

   Today was my first completely cloud free day, but I still only equaled my best output day(28kwh).

   The first day I got 28kwh, I had late cloud cover, watching the inverter output, it seems that early in the morning and late in the afternoon, cloud cover may actually be an advantage to power output. Is this because of the diffusing effect that the clouds have on sunlight, and 'bend' it from a shallow angle to a higher angle?

   At first I thought that a completely cloud free day would be best, now I'm not so sure.

   Posted Wednesday 17 Mar 2010 @ 9:00:14 am from IP #
2. 

   Russell Moore
   Member

   It is no coincidence that when people talk of solar farms, it is almost always mentioned that the farms will be set up inland, in areas that have the maximum number of cloud free days. The biggest derating effect on my panels so far has been cloud cover.

   And as pointed out by many others who have had far more PV experience than me, it is thick, low cloud that is the killer, high cloud has a lesser effect on power output. On days when I have had 50% or less cloud cover throuhout the day, I can get over 20kwh, the max' being 28kwh so far, (which by the way is one kwh per 180w panel..) yesterday (31/3), under 100% heavy cloud and rain, I got my lowest output yet of 4.5kw.

   I have decided to put in an order for nothing but overnight rain, and cloud free days LOL...

   Posted Wednesday 31 Mar 2010 @ 11:34:10 am from IP #
3. 

   Inspector
   Member

   Inland would also have hotter ambient temperatures than coastal areas with sea-breezes... Who's going to work out what's worse - more cloud or higher ambient temperature?

   Posted Thursday 1 Apr 2010 @ 2:19:28 am from IP #
4. 

   petacat
   Member

   First and foremost thing to do to reduce panel temperature is to provide ventilation at the underside. Heat fins could even be economic. Well constructed framing and leaving an air gap make a difference from what I have tried. The difference can be 20-25 degrees in mid summer just by having a 10 cm gap to the roof. I cant say if it is beneficial to have more than that.

   As munter suggested, placing the panels as surrogate eaves works well because of the cooling effect. From my own perspective it makes sense to use the panels as eaves because you need to use some material anyway for the eaves and there is a clear benefit in using one lot of materials for two purposes. There are, of course consequential issues such as what angle to use for the panels for efficiency and how that affects their use as an eave - especially with a passive solar house.

   Posted Sunday 4 Apr 2010 @ 4:27:54 am from IP #
5. 

   Russell Moore
   Member

   Here are some photos of my system, image three has the sprinkler in shot, especially if you zoom in.
   It may take a while for each image to download http://profile.imageshack.us/user/russellmoore/

   Posted Sunday 16 May 2010 @ 10:41:50 pm from IP #
6. 

   munter
   Member

   Nice photos Russell. I like the slightly diffuse reflectors in place up behind the panels. I saw the earlier discussion about them and figure they look like a better way to boost the output at lower risk of a manufacturer taking issue with them. Have you noticed increased output using it?

   Posted Monday 17 May 2010 @ 2:33:35 am from IP #
7. 

   Anonymous
   Unregistered

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   Posted Monday 6 Sep 2010 @ 7:46:00 am from IP #
8. 

   Ed Seymour
   Member

   Russell, not sure if you're still an active member of this forum, but would like to know about the water cooling system you devised for your solar panels.

   We have recently had a 3.5kW system installed where we live in Melbourne. On cloudy days when the sun occasionally breaks through, peak output is as high as 3,950 watts (or at least that's what the read-out displays on the Aurora 3600 Outdoor Inverter), whereas on perfectly sunny days (even those when the ambient temperature is only mid-twenties celsius - the peak output only get's to around 2,800 watts.

   This weekend I experimented with running a hose pipe over the panels (which are mono) for 3 or 4 minutes to cool them down (they're on a tilt frame on a flat roof) and their output immediately increased quite markedly (additional 350 watts or so). That got me to thinking about running a cooling system from our unheated pool - with the benefit of warming our pool up which is often too cold for my young kids, and cooling the panels down.

   I then Googled for similar ideas and your thread came up (great minds and all that). I'm particularly interested in your estimate of the net increase in electricity production and whether it is worth the time/effort/cost. I guess there is also some environmental cost (and a small monetary cost) from the loss of water through evaporation. I'm proposing to affix guttering to the bottom of the two rows of panels (rather than using the the roof down downpipe as the return pipe) to minimise evaporation.

   Ed

   Posted Monday 7 Mar 2011 @ 3:23:53 am from IP #
9. 

   Sunshine
   Member

   Ed,
   I think running water from the roof guttering into the pool isn't a good idea, as it will increase the amount of phosphate into the pool, causing algae problems later.
   My pool expert has even advised me it's not even worth using tank water to top up the pool, as the $2/kilolitre saving for the cost of water, is nothing against the cost of Starver to remove the phosphate from the water.

   Getting back to the original post, does sound reasonable idea if you have a rainwater tank and just recirculate the water from the tank to the roof.

   Posted Monday 7 Mar 2011 @ 4:24:03 am from IP #
10. 

    Russell Moore
    Member

    Ed, still here, I post a little less often now days, but still lurking.

    You should check out the Whirlpool forums, there is a great thread there, (water cooling of solar (PV) panels), that I have contributed to as well.

    I have been water cooling my panels for a year now, using recirculated tank water, with no ill effects on the panels, yet! The cooling works best on hot, low humidity days, but any time there is full sun it is effective, even in winter..

    Have to agree with Sunshine about not using water from normal guttering to fill your pool, my tank water at the moment stinks, as we have had very little rain of late, and it is constantly being recycled over the panels. Maybe your idea of small gutters only on the panels might be OK though.

    Good luck. Russell

    Posted Monday 7 Mar 2011 @ 7:32:07 am from IP #
11. 

    Ed Seymour
    Member

    Thanks Russell, I will read the thread on Whirlpool.

    Posted Monday 7 Mar 2011 @ 10:10:45 am from IP #

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