Will a heat sink on a solar panel help?

[DualFuel]

Hi,

 Am experimenting with discarded solar cells from Solargizer desulfators. These panels are not of significant wattage. I think six in series make 18volts open circuit and enough amperage to charge at half a watt. Its not significant until one places a desulfator in parallel with the cells. Then some of these dead or weak batteries start raising their voltages.

 Okay, the big fat question is about heat. I think in terms of thermodynamics. These panels sit out in the direct desert sunlight. The panels get well over 150F. I wonder if the panels would benifit from a big heat sink on their shaded side. So way of providing a cold resivoir.

 Also, it shouldn't hurt them to be wired together series, parallel right?

 BPJ

[John II]

Yes you will notice an improvement if the outside ambient air temperature is quite high. This is the reason they tell you to mount commercial panels with an air gap between them and a roof. Many of the new P.V. manufactures are installing a sheet of glass on the back side rather than using plastic. The Glass sheet dissipates heat from the panel lowering it's temperature improving it's output performance in hot weather.

And yes, you can series and parallel to your hearts content as long as the P.V. panels are reasonably the same size in output.

This is a quick answer to your questions, hopefully someone "in the know" can give you more detailed information.

John II

[hayfarmer]

Looking at my roof  solar rack mounting rails today ,pondering how to make it a tracker,  I noticed there was



 2 positions on the mounting legs ,lower  profile and upper. I  decided to move the rails to the upper mounts about  a inch difference and .....................poof 10 % more amps , less heat to the panels , more ventilation.


 panels are facing south on good angle and planning to build actuator and tracker to pivot racks  toward west ,still researching.



hayfarmer

[MagicValleyHPV]

I'm dubious about the use of a heat sink unless it's made of copper or aluminum and finned. While heat sinks do indeed absorb and stabilize the 'heat' source, they also need to transfer the heat to the surrounding air - which requires surface area (think 'fins').

I'm pondering the same thermal situation, and I'm strongly leaning towards mounting my single PV vertical (for improved cooling) and using a reflector.  The advantage with my PV is that it's bifacial - in other words, it is designed to absorb from both sides of the panel. That said, I may even try two reflects - one aimed at the front, and a second (perhaps defused or just painted white) at the rear. This is most assuredly against Sanyo's recommendations AND no doubt a breach of the warranty. And yes, I plan to monitor the PV's temperature in several locations so I don't fry it.  

  

[naturalpessimist]

As I'm reading this thread I cannot help but think of the rocket stove(s) I've built.
In doing so you learn real fast the impact/effect of heat/combustion/draft - and that the longer the exhaust (flue) the faster the air flow.
This is also true with a solar draft roof. Yes, heat rises, but by adding a "chimney", when the chimney really heated up, it draws air so fast you could blow dry your hair ---ok, ok, that's a stretch but you get the idea.

Would it not be possible to attach a "chimney" to the panel (maybe parallel - along the long side) that would act in the same manner, and draw through the air?
Rhetorical question really, I know that it would, just don't know how much

[Madscientist267]

I've been toying with the idea of keeping panels cool for a bit, and have taken the first step here, but by itself it didn't do a whole lot. The panels run somewhat cooler, but it's difficult to detect the difference in output.

Since covering the entire back side of a panel with aluminum (nevermind copper) would get VERY expensive quickly, I am pondering a new approach. Thinking of using cut up drink cans and layering them somewhat to get the fin thing going...

Granted, with my application, it might be a little more practical than trying to do it on a grand scale such as an entire roof full of panels, but I'm still not sure of the gains vs PITA factor.  

Either way it represents a lot of work. There would be about 1 can's worth of aluminum per cell in the panel, and for me, thats just shy of 72 heatsinks... LOL Is it worth all the hassle for a few mA?

Shrug.

Another approach, also rather (ok more like prohibitively?) expensive, is to turn the PV panels into hybrids, and in the process gain the added effect of the cooling. Tossed this one around for myself as well.

Use circulating water to pull the surplus heat out of the panels and preheat your DHW supply.

The pros as I see them:

Cooler panels, more output
Preheated water for your water heater, saving some heating costs there

The cons:

A closed loop system with all the copper (maybe aluminum if you wanted to deal with the issues involved in that) required to contain the coolant going through the panels behind the cells. Expensive. Would require antifreeze. A lot of work, even if you bought the panels pre-made for the purpose. If such a thing exists. ?

A heat exchanger would be necessary; you can't shower with antifreeze.

A pump to circulate the antifreeze. Most designs would mean that the water doesn't move on it's own (to any useful degree) in an application like this. Cost of the pump, energy to run it.

EDIT - Not remotely practical for portable 'class' panels...

---

I throw that out there to get someone's marbles rolling...

So in a nut shell... Is it worth it to try and squeeze out a few extra watts? Probably not. I tried it just to try it.

My excuse for leaving the fans on mine is "heat isn't good for anything electronic"... I'm probably more in denial that it was a failure rather than using sound logic here...  

In your case, the panels are so small that experimenting wouldn't hurt, but don't expect much.

FWIW

Steve

[MagicValleyHPV]

The panels run somewhat cooler, but it's difficult to detect the difference in output.

This is for the Sanyo 186w HIT PV. Lots of variables, and of course other PV's will be affected differently, but at least you can 'ballpark' the losses/gains.  

[Madscientist267]

Yeah, thats the typical plot, just have to substitute the appropriate values.

Upon further experimentation today, I was able to squeeze out another 15% from mine (in 80F ambient, full sun) by a patient spray-down with a water bottle. It of course doesn't last, but illustrates the concepts.

It's a tricky thing, but once you get 'the disease', you'll find yourself doing all kinds of weird things to scrape every milliwatt out of what you have.

It helps if you're OCD... 

Steve