So now I have a solar PV system how do I make the most of it???

Cardew

orrery wrote: »

The standard panel rating is likely to be at 25C and I'd guess that it is at this panel ambient that the Normal Operating Cell Temperature is 45C. So you lose 0.431% per degree C rise above this.

It is anyone's guess as to what the cell temperature will be on a stinking hot day, but the maximum specified is usually 85C and I can't think it will be much below that. Normal garden objects get to at least 60C (the temperature at which you just can't hold your hand on for any time) in summer sun so we can assume that the cell temperature will be at least 80C, possibly 85C, so a 40C rise. This would give a 17% reduction in output.

So, as suggested before, you use all your surplus electricity to have fans blowing on the panels to cool them;)

celerity

Cardew wrote: »

So, as suggested before, you use all your surplus electricity to have fans blowing on the panels to cool them;)

Or, more effectively, rig up a closed sprinkler system powered by say, a 100W pump. This was discussed on here last year, not sure where now - but it's reasonably common in Australia and other scorching places.
The difference in generation curves with and without water cooling were pretty dramatic.
The downside is that all the DIY photos I've seen of such a setup looked a bit rough .

/\dam

Martyn1981

celerity wrote: »

Or, more effectively, rig up a closed sprinkler system powered by say, a 100W pump. This was discussed on here last year, not sure where now - but it's reasonably common in Australia and other scorching places.
The difference in generation curves with and without water cooling were pretty dramatic.
The downside is that all the DIY photos I've seen of such a setup looked a bit rough .

/\dam

Funnily enough, that idea had crossed my mind, using a small pump powered via a solar panel. Run that from a water butt connected to the roof guttering.

I assumed that the gains would be minimal (if you can class legionnaires disease as minimal!), and the water losses from evaporation would be too quick.

I hate to think what those with PV, but not on a water meter will do with this idea. :eek:

Mart.

celerity

Martyn1981 wrote: »

I assumed that the gains would be minimal

Apparently not, according to the first hand accounts I read anyway.
You can test it out yourself by waiting for a hot day with little wind and spraying your panels with a hose (I'm sure your water company won't mind). You should see a clear rise on your generation graph, assuming you have a monitor. I did it last summer just out of curiosity, but didn't quantify how effective it was, just saw the graph change.

I seem to remember that the main article I read only used a timer to spray a mist over the panels. The person had decided this was good enough without resorting to temperature sensors etc.

The main difficulty as far as I know is to get the guttering working well, so you don't run out of water.

/\dam

larkim

Martyn1981 wrote: »

I hate to think what those with PV, but not on a water meter will do with this idea. :eek:

Mart.

<Puts hand up as a non-metered PV person>

Tempted just to set a hose running on the roof 24 hours a day - costs me nothing, and we're not in a hosepipe ban area.

But that would damage my green credentials!!

Matt

grahamc2003

larkim wrote: »

<Puts hand up as a non-metered PV person>

Tempted just to set a hose running on the roof 24 hours a day - costs me nothing, and we're not in a hosepipe ban area.

But that would damage my green credentials!!

Matt

Is your cold water tank is situated higher than your panels?

As to cooling the panels efficiently, I expect in 10 years hybrid PV/Thermal panels will be the norm - killing two birds with one stone, cooling the panels while scavenging the heat.

EricMears

Providing you collect rainwater (and that from SPs doesn't overshoot gutters !) it would be perfectly feasible to pump water from a suitable container using a pump triggered by high light levels.

A few practical details like filtering out impurities and setting threshold light levels make it a little harder but it would still be eminently do-able.

An experiment with an unmetered hose would still be needed to let us all know if the investment is justified.


hybrid PV/Thermal panels would indeed represent a huge step forward - but improvement is unlikely to justify cost of existing SP owners upgrading their systems.

spaine

Big Thankyou to the E.on Web Team (especially Amanda) who have helped nudge the FIT Team ..

PDF contract received via email today :j and will be in the post this afternoon.

Very Happy.
:T

celerity

re: water cooling solar panels, I've dug up some old references:
http://forums.whirlpool.net.au/archive/1609024
http://tlug.webs.bailey.homelinux.net/solar/
Contains loads of detail, graphs, photos and discussion.
I'd overestimated the pump required, seems he started with an 18W one and then upgraded to 42W.
As far as I can tell, he's seeing an approx 10% improvement in generation from using about 1000L of (recycled) water per day. The key point is that he's in Australia though - in the UK the improvements would surely be significantly less (it would be interesting to know how many subjectively "hot and sunny" days we get per year in this country).

The first link discussion thread is worth a read too - some people have pretty ambitious plans to try and boost a 3.6kWp system to 5kWp for example .

/\dam

EricMears

seagull09 wrote: »

I would venture to suggest in the UK it would not be worthwhile doing given the expenditure to buy parts needed, the power to operate the pump, and then the relatively small saving for a handful of days per year.

"the power to operate the pump" should of course be free. No point wetting panels other than at periods of high generation. Same argument would apply to any power used to blow air across them.

The saving needs to be compared with capital cost of equipment needed then an investment decision can be made on normal criteria.