The easiest way to keep PV panels cool would be to put some shade cloth over them.

I've never seen a better match between avatar and statement.

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Mr Milk said..

Test pilot 1 said..

I wonder how many rooftop sized units are made. Would be better for storing energy for night time use.
Having felt the heat reflected radiated from solar panels, you'd think that you could combine the 2 principles using pv plated reflectors for dual production of energies(electricity/heat storage). Even if only for power and hot water you could run the heat collection pipes ont the back of PV panels, cooler panels would surely lower electrical resistance if only slightly and surely be a more efficient use of space on a roof.

I think that you would find the problem with a small solar thermal system is that you can't heat up enough of your heat storage medium (ie salt solution or oil) to make it worthwhile. A big tank has less surface area per unit of volume, so it leaks less heat to the environment. And there is a problem in that solar PV works best when the collector is perpendicular to the sun's rays, while solar thermal uses rough parabolas to focus the rays onto a pipe.

As for cooling solar PV, I have read of it being done by Wollongong Uni Architecture students on a house that they refitted as a project to show that an old fibro house could be made energy efficient. They did it with fans under the panels drawing a little of the power that the panels generate. If you try to do it with water I think that there are a few problems to overcome. Weight of the system immediately increases. Then you have to get flow going through the pipes. Pumping water is harder than blowing a fan. Sharp temperature gradients in the materials near the cooling pipes could accelerate ageing. And, the big one.....water and electricity is a dangerous mix

Pure water and electricity is a good mix, as thats what we use to clean live HV insulators up to 132kv. When the water aint pure that is when problems arise. Pumps are not used for normal solar hot water so they would not be needed for a combined unit. Using smaller capilliary pipes per panel would lower the combined weight per panel. Each panel could use oil as the heat transfer medium going to seperate header tanks with pipes running through the header tanks to heat the water feeding to hot water storage.

Not that I want to argue about it, but I think that using your water heating to cool solar PV is really not much of a goer. Solar water heating is to heat up ~2-400 litres by contact with a hot surface over several hours. Thus thermosyphoning is fine. Slow flow rate and the surface stays hot to heat up the next few cc of water as it enters the manifold. Cooling the PV panel to improve its efficiency means dumping the heat as fast as possible, so the surface never gets hot enough to heat the heat transfer medium to anything above lukewarm
Cooling the solar PV is a good idea, just by the way. My own system seems to produce about 10% or so more power on a breezy day, maybe 15% if it is a cool southerly in sunny conditions.
I didn't know that you use H2O to clean HV insulators. There you go. I'm ignorant. But I do remember that a small quantity of dissolved salts improves conductivity of water and I can tell you that tap water is not at all pure. The chemical factory that I once worked in did a lot of business every time we had a few rainy days producing Al2(SO4)3 solution that gets dumped into Prospect reservoir to help settle out the mud in the inflow.

Something different re Base Load Power: pulverise dirty coal to a super fine particle in water, then run a massive ship diesel engine directly on it. They'
re talking halving co2 emissions with CCS on top of that.

CSIRO and its industry partners plan to trial a direct-injection carbon engine with the aim of reducing emissions from brown coal-generated electricity by 50%.The $A1 million trial is to be conducted in Victoria?s Latrobe Valley, home to the second-largest and lowest-cost brown coal reserve in the world.
Brown Coal Innovation Australia has put up the $1 million for the trial.

The technology involves converting coal or biomass into a water-based slurry that is directly injected into a large, specially adapted diesel engine.
The fuel burns to produce intense temperature and pressure in the engine, which provides power to turn electrical generators.
An existing laboratory-scale prototype engine will trial fuel based on Victorian brown coal and this work will be followed by trials using the same fuel in a large scale test engine in Japan.

This research will determine whether DICE can enable brown coal to produce Australia?s lowest cost, reduce carbon dioxide electricity for the staged replacement of existing coal power plants.
CSIRO Energy Group executive Dr Alex Wonhas said DICE technology could allow Australia to economically develop coal reserves while reducing the sector?s environmental impacts.

?Australia has the second largest brown coal resource in the world but current utilisation technologies are carbon intensive so we need to implement cleaner and more efficient ways to generate energy from coal,? he said.

Info about DICE:
http://www.globalccsinstitute.com/insights/authors/martinoettinger/2012/08/01/mrc-%E2%80%93-dice-%E2%80%93-ccs-%E2%80%93-game-changer-electricity