Increasing Solar Panel efficiency with Water film

[syiafuku]

Hi everyone. As per title, I'm currently doing my final year project on increasing the efficiency of solar panel through the use of water film. We all know that solar panel loses efficiency when subject to long exposure to sunlight/heat i.e over heating. I'm living in Malaysia, a tropical hot climate country. This is my initial design( just a simple sketch):

http://www.flickr.com/photos/30842097@N08/4383808339/?addedcomment=1#comment72157623499076548

What do you guys think and what are the necessary datas that i should know and collect?(water flowrate?) So far, i need to get the average insolation readings for a day ( without the water film and with water film). Opinions and insights are very appreciated.

Regards,

Syiafuku

[Mike90250]

In past trials, the power needed to pump and recycle the water, exceeds the gain from the cooler panels. Free water from a creek would not have this issue.

[syiafuku]

i see..thanks for the info. I didn't thought about it before . does the water flowrate affects the cooling? how? faster flowrate = faster cooling/lower temperature drop?

[Mike90250]

i see..thanks for the info. I didn't thought about it before . does the water flowrate affects the cooling? how? faster flowrate = faster cooling/lower temperature drop?

right, if the water is slow enough, it picks up so much heat from the dark panels, the panels loose power, so more flow is better, to keep panels cooler.

[syiafuku]

right, if the water is slow enough, it picks up so much heat from the dark panels, the panels loose power, so more flow is better, to keep panels cooler.

Ooo i see... so water can affect it the other way around is it? instead of cooling it to increase output efficiency, it can also decrease efficiency if the flowrate is slow enough to absorb much heat. This is so new to me, thanks!

[BilljustBill]

Here in Texas, water down to 300 ft. is consider "hard water" due to all the minerals. In Stephenville, Tx, at the University there, I parked my new car in a legal parking zone in front of the President's house. Two hours later, unknown to me, the automatic sprinkler system came on. At the end of its cycle, the light breeze carried a fine mist loaded with minerals. All the glass surfaces on the lawn side of the car, and half the windshield and rear glass were covered with a white mineral film you couldn't scratch off with your fingernail.

The University paid for the car to be cleaned and power buffed as it was the only way to clean the entire glass and paint areas. It took almost a day.

Using water to cool would have to use treated water so the panels wouldn't build up and bake on mineral build-up, no matter which side of the panel you plan for the water to cool.

As a side note, why wouldn't thin L-shaped aluminum strips attached with a thermally conductive tape or adhesive, and placed on the rear of the panels, carry away heat? Being on the underside, they would be naturally shaded on top of an average roof and with North America's angle to the sun, the tilt of the panel would allow passive air to carry away the heat.

search: 3M™ Thermally Conductive Acrylic Soft Tape 9889FR

Also, I ran across some 2" wide rolls of copper tape at the local flea market, several years ago. Except for the retail cost, why wouldn't running this tape in vertical strips on the rear of a panel help carry away heat?

Because of the undersided location of either of these materials/methods, it wouldn't readily allow their surfaces to build-up contaminates nor require regular cleaning of their surfaces once they are in place...

Bill

[Mike90250]

heatsinks on the backside are not a bad idea, but the plastic sealing layer (tedlar etc...) inhibit the thermal path.
And a little vinagar in the wash water, will clean off a light layer of hard water deposits. Weeks worth - no way. And it's bad for anodised aluminum

[syiafuku]

Here in Texas, water down to 300 ft. is consider "hard water" due to all the minerals. In Stephenville, Tx, at the University there, I parked my new car in a legal parking zone in front of the President's house. Two hours later, unknown to me, the automatic sprinkler system came on. At the end of its cycle, the light breeze carried a fine mist loaded with minerals. All the glass surfaces on the lawn side of the car, and half the windshield and rear glass were covered with a white mineral film you couldn't scratch off with your fingernail.

The University paid for the car to be cleaned and power buffed as it was the only way to clean the entire glass and paint areas. It took almost a day.

Using water to cool would have to use treated water so the panels wouldn't build up and bake on mineral build-up, no matter which side of the panel you plan for the water to cool.

As a side note, why wouldn't thin L-shaped aluminum strips attached with a thermally conductive tape or adhesive, and placed on the rear of the panels, carry away heat? Being on the underside, they would be naturally shaded on top of an average roof and with North America's angle to the sun, the tilt of the panel would allow passive air to carry away the heat.

search: 3M™ Thermally Conductive Acrylic Soft Tape 9889FR

Also, I ran across some 2" wide rolls of copper tape at the local flea market, several years ago. Except for the retail cost, why wouldn't running this tape in vertical strips on the rear of a panel help carry away heat?

Because of the undersided location of either of these materials/methods, it wouldn't readily allow their surfaces to build-up contaminates nor require regular cleaning of their surfaces once they are in place...

Bill

oh wow.what is this "hard water"? i've never heard of this kind of phenomena before. and I don't think here in Malaysia that kind of thing could happen, assuming minerals are the major factor that contribute to that occurrence. Never saw or heard it before but then again I don't know jack about minerals anyway :P. I'll take a look on the product you mention, but my project focuses on using water as a coolant, so I can't say much about other methods of cooling( unless my SV decided to widen the project scope) .good info nonetheless!any other info you can share is appreciated. thanks

[lile001]

oh wow.what is this "hard water"? i've never heard of this kind of phenomena before. and I don't think here in Malaysia that kind of thing could happen, assuming minerals are the major factor that contribute to that occurrence. Never saw or heard it before but then again I don't know jack about minerals anyway :P. I'll take a look on the product you mention, but my project focuses on using water as a coolant, so I can't say much about other methods of cooling( unless my SV decided to widen the project scope) .good info nonetheless!any other info you can share is appreciated. thanks

"hard water" is water that contains high levels of minerals in solution, typically calcium. Hard water is common wherever water is drawn from deep wells. Especially if the underlying rock is limestone. There is an old joke about water-cooled-air-cooled air conditioners - often people spray water on their air conditioning equipment with a sprinkler in order to increase the capacity. Works great until the machine gets caked with calcium deposits and then goes in the junkpile.

Salt water does the same thing, only it leaves salt when it evaporates instead of calcium.

That's the main risk with your setup - that the water will leave deposits. If you are using pure rainwater, the risk is much less, because rainwater is essentially distilled water, with a little airborne dust mixed in.

[syiafuku]

"hard water" is water that contains high levels of minerals in solution, typically calcium. Hard water is common wherever water is drawn from deep wells. Especially if the underlying rock is limestone. There is an old joke about water-cooled-air-cooled air conditioners - often people spray water on their air conditioning equipment with a sprinkler in order to increase the capacity. Works great until the machine gets caked with calcium deposits and then goes in the junkpile.

Salt water does the same thing, only it leaves salt when it evaporates instead of calcium.

That's the main risk with your setup - that the water will leave deposits. If you are using pure rainwater, the risk is much less, because rainwater is essentially distilled water, with a little airborne dust mixed in.

i see.thanks for explaining that in detail for me. My project will use treated water i.e water from pipe.not from an underground well etc. That should be okay, right? One thing my SV requested was the water film (the water that's going to run down the panel) is preferred to be very thin. I never had a chance yet to ask him about this since he is away since last week. What's the effect of using thinner water film in terms of cooling?

[BilljustBill]

In metal machining with vertical mills or boring machines for instance, they use a mist of a coolant since mist will absorb the heat faster. Flooding a part with coolant as the metal cutters machine surfaces is another way. It's up to the amount of heat generated and the material's traits as to which does the better job of lowering the heat.

Several years ago, a company came out with an aftermarket gizmo for making the outside air conditioning compressor work more efficiently. Catching the condensed water from the interior air conditioning coil that is normally routed to a small drain pipe and letting it fill a small container, this condensed water is as pure as distilled water. When the container reached a point, a float switch turned on a small pump and the water was finely sprayed on the condenser coils which cooled the Freon much better. The main problem with this gizmo was when the air temps were lower and the extra cooling spray caused the head pressure of the compressor to spike which would cause extra wear and tear if not damage.

In the early 1990's, riding mower tractors with horsepower rating of 15 to 20hp, had a hay-day touting "liquid cooling". Some were made by John Deere. But here in the South, liquid cooling really didn't make much sense and if the small radiator became covered with dust and clippings, the engine would over heat.... It seems that if small bore engines cool themselves with air blowing over the cast fins around the head and cylinder with years and years of success, only when pushing the thermal limits for extra horsepower would liquid cooling be needed.

Like one solar panel designer, he ran a liquid through the back of his panels which absorbed the heat and getting higher wattages, and then the liquid was pumped around a water tank to preheat it for household hot water. I think the main issue there was that each panel required a connection, and the more connections you have in a loop the more issues you'll have with leaks...

Moving air over cooling fins on the back side of a solar panel seem more cost effective as well as having the least maintenance issues compared to the complications of liquid mixtures, leaks, and pump failures.

[syiafuku]

In metal machining with vertical mills or boring machines for instance, they use a mist of a coolant since mist will absorb the heat faster. Flooding a part with coolant as the metal cutters machine surfaces is another way. It's up to the amount of heat generated and the material's traits as to which does the better job of lowering the heat.

Several years ago, a company came out with an aftermarket gizmo for making the outside air conditioning compressor work more efficiently. Catching the condensed water from the interior air conditioning coil that is normally routed to a small drain pipe and letting it fill a small container, this condensed water is as pure as distilled water. When the container reached a point, a float switch turned on a small pump and the water was finely sprayed on the condenser coils which cooled the Freon much better. The main problem with this gizmo was when the air temps were lower and the extra cooling spray caused the head pressure of the compressor to spike which would cause extra wear and tear if not damage.

In the early 1990's, riding mower tractors with horsepower rating of 15 to 20hp, had a hay-day touting "liquid cooling". Some were made by John Deere. But here in the South, liquid cooling really didn't make much sense and if the small radiator became covered with dust and clippings, the engine would over heat.... It seems that if small bore engines cool themselves with air blowing over the cast fins around the head and cylinder with years and years of success, only when pushing the thermal limits for extra horsepower would liquid cooling be needed.

Like one solar panel designer, he ran a liquid through the back of his panels which absorbed the heat and getting higher wattages, and then the liquid was pumped around a water tank to preheat it for household hot water. I think the main issue there was that each panel required a connection, and the more connections you have in a loop the more issues you'll have with leaks...

Moving air over cooling fins on the back side of a solar panel seem more cost effective as well as having the least maintenance issues compared to the complications of liquid mixtures, leaks, and pump failures.

thanks for the info billjustbill.i've already mentioned to my SV like you said; cooling fins and all, but he insist that our project focuses on using water, as water here in Malaysia is treated and easily available,so as not to have to use other coolant. I've already got the insolation data reading from 10am to 5pm but I think I need to get a more accurate data from a weather station. I want to have both direct and diffused reading of solar radiation. So for now, my Supervisor asked me to think of a design to use and run water on the Solar panel's surface. My initial design is like the one in the first post. Do you guys have any comments or other ideas for a better design? Oh and a tank is probably needed to put and circulate the water i.e. by using a pump.

[Mike90250]

In past trials, the power needed to pump and recycle the water, exceeds the gain from the cooler panels. Free water from a creek would not have this issue.

Please document fully, and see if you can actually create a gain, after running the pump.

[syiafuku]

sure of course i'll document it soon.but now the problem is I'm trying to think of a better design for the solar panel.the original design should make do but in case there's a better idea, please share

[russ]

A film of water on the panel will reflect light - the question is how much.

The only you can make any progress is to set up one panel and see what happens.

To me, the fins on the backside make good sense. They are totally passive with no moving parts and do not interfere with light reaching the cells.