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active cooling of PV-panels - Page 4

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Posted by Morris Dovey on December 6, 2008, 12:50 pm
mundt wrote:

Ok - good to know.

Ah - I was envisioning a roof-mounted circulator, with a head only a bit
greater than the hight difference between the collection gutter and the
distribution pipe.

I understand that any lift pump is limited to a head in the neighborhood
of 25' or so. An incorporated 'loop' to a ground level heat exchanger
would introduce additional friction, but would not subtract from that
maximum head.

If there's a need to move water from an unpressurized source (like a
rain barrel) then a ground level pump could probably push (as opposed to
lift) replacement water the requisite 30' - and my guess is that the
capacity would only need to match the rate of topside evaporation.

The PVC irrigation pump shown on the bottom of the web page at
http://www.iedu.com/DeSoto/Projects/Stirling/Dyne.html  probably wouldn't
be the best choice for this application, nor would the improved version
at the top of http://www.iedu.com/DeSoto/Projects/Stirling/Fluidyne.html  
because designs are optimized for low cost. However the high-temperature
engine at the bottom of the second page is an attempt to optimize for
efficiency. At the 725F design temperature it should have an energy
conversion efficiency limit close to 55%. That, in combination with the
all-metal construction should allow doing either function with capacity
to spare. I'll know for sure when it's been tested.

Ok. This is an area where I don't have any expertise at all. I'm happy
to take your word on this kind of stuff.

Seems reasonable to me.

I'll take your word for it. I've very carefully avoided getting involved
with DHW systems. Still - in my part of the country "tepid" is a
significant improvement over "well temperature". I'm so cheap that I'd
want to recycle the heat if I could. :)

I'm not worrying about cooling the panels - rather about not having the
plumbing self-destruct in sub-freezing weather.

Always possible, although I'm familiar with what it costs to produce a
trough and solar engine and I'm becoming more so all the time. :(
Actually, I think my numbers include a bit of "bloat".

Heh - I read alt.solar.photovoltaic to learn. I don't have any direct
experience with the stuff (other than a tiny cell in a calculator) and
don't have any place where I can make use of the technology.

But - I'm already working with solar powered fluidynes for irrigation
and village water supply, so from an a.s.p perspective I'm probably
coming at this problem bass-ackwards.

I don't know the future of photovoltaics, but there's already enough of
a worldwide installed base that development of a reasonable-cost
retrofit capable of boosting PV energy conversion efficiency by 10%
seems worthwhile. I think it's a wizard idea.

However, it's not a development I plan to pursue because I'm already at
the limit of my resources with just the projects I already have
underway. There's enough info on my website for someone else to make a
start at this one, and if it hasn't happened by the time I'm done with
current projects, then I may put it on my to-do list...

Morris Dovey
DeSoto Solar
DeSoto, Iowa USA

Posted by rwprjr on January 9, 2009, 12:37 am

I did a google search for panels I had seen on a Planet Green program.
Renovation Nation, episode Boston/ 2008.
I missed the company if it was stated.
they showed PV panels that had a water path on/in the back side to
cool the panels increasing efficiency, and heating water to the
domestic water tank, and I think to the radiant flooring.
I live in NC and we get some pretty strong sun, Not to mention heat
gain through the roof.
I thought that would be a dandy Idea if we had a large under the house
tank to build up that heat to use in the winter, we get mainly cold
nights in snaps down to 12 degrees some nights.
it can get to 104 in jul/aug.
Our motto is its all an experiment. We won't just try anything, but
are interested enough to investigate.
Did anyone catch that program or know of what company makes those
Thanks in advance,

Posted by Christian Kaiser on January 11, 2009, 5:54 pm
Good idea, though not new. Problem is, the aims contradict: you want
cold panels (PV), but hot water (DHW). What would be best? ;-)


Posted by Beac on January 2, 2009, 5:46 am
Have you looked at this site.  It might help you with your question.


Hope this helps.
Dave Beacco

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