materials for making solar panels and cooling advantages - Page 1
Forum section: electronics / general

author: Simon
author_rank: Unknown
timestamp: April 10, 2011, 12:35:21 pm
content: Right so after debating the pro's and cons of solar tracking I have decided to use fixed panels. As I said in my other thread I have a flat roof area approximately 3 metres long and intend to build my own panels making them single rows of cells and as long as practical.I've often heard tell that solar panels are more efficient when cooler. Well while I'm making these up then I could build a small fan into the back of each panel with enough room in the panel for air to flow through to help keep the panels cool. any suggestions there ?

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 10, 2011, 01:10:55 pm
content: each fan for each panel doesnt sound economical, how about natural airflow? raise the panel a bit for a space underneath. and about the tracking mechanism on the other thread, how about limited and specialized tracking system that best suits your project? you are very well into deep research on this, since you know best your condition and need. my 2cnts.

author: Simon
author_rank: Unknown
timestamp: April 10, 2011, 01:13:20 pm
content: tracking is a waste of money in my case, it is a small setup and the cells are cheap. Well the cooling fans depend on gain efficiency. The cells will be in long rows so only a couple of watts from a 60W panel will be used, it that makes it more than 2W efficient then it's worth it

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2011, 02:20:12 pm
content: Why not water cool the panels? You could then use the waste heat for hot water, even if it's not hot enough, you'll still save energy it it's preheated before the boiler.

author: onemilimeter
author_rank: Frequent Contributor
timestamp: April 10, 2011, 02:23:44 pm
content: How many watts will be gained if the panel is made 1 deg C cooler?

author: PetrosA
author_rank: Frequent Contributor
timestamp: April 10, 2011, 02:39:29 pm
content: What temperature do the cells need to be at for the efficiency to really start dropping? IOW, how cool is cool and how hot is hot?

author: Simon
author_rank: Unknown
timestamp: April 10, 2011, 04:01:00 pm
content: well those are the questions i need answering. Hero, how can I water cool, that sounds complicated. I'd have to build a pressurized panel where the water does not come into contact with the electrics.Does anyone know the temp specs for solar cells ?

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2011, 05:15:15 pm
content: Quote from: Simon on April 10, 2011, 04:01:00 pmMaybe use radiators or water heating solar panels behind the cells?You'll need a pump to circulate the water but that shouldn't use too much power. If it's an issue you could only turn the pump on when the water reaches a certain temperature.

author: Russel
author_rank: Regular Contributor
timestamp: April 10, 2011, 05:16:55 pm
content: Here is some reading material that you may find interesting.Solar Photovoltaic Panels From a Heat Transfer Perspective

author: Simon
author_rank: Unknown
timestamp: April 10, 2011, 08:42:30 pm
content: Quote from: Hero999 on April 10, 2011, 05:15:15 pmI'd need to remove the heat from the cells, to do that a coolant must flow over them, water cannot as it will cause issues hence my idea of air, essentially by pumping air through the panel I'd be running a coolant over the cells themselves and get maximum heat transfer. How will water heating panel help cool a photovoltaic panel ?

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2011, 08:47:05 pm
content: No I'm talking about using water to cool the panels not heat them.Why does water actually have to flow over the cells to cool them?As long as the radiator is in direct contact with the cells it will cool them by conduction and radiation. It's just a heat exchanger.

author: Simon
author_rank: Unknown
timestamp: April 10, 2011, 08:55:05 pm
content: yes you need to cool the cells, but you need the cells to come into contact with a coolant in order to remove the heat, in my case the cells will be glued to a plastic or wood base, trying to exchange heat through that would be a waste of time, you can't allow water to come into contact with the cells. Remember I'm building these they are not commercially made so the cells won't be well bonded to the structure from a heat transfer point of view.To use water i need two heat exchangers, one to take heat from the panel/cell and one to dump it into the air (the radiator). The exchanger for the panel must integrate into the panel in order to take heat away from it - not really a likely scenario without expense that outweighs the gain

author: Zero999
author_rank: Super Contributor
timestamp: April 10, 2011, 09:48:49 pm
content: Quote from: Simon on April 10, 2011, 08:55:05 pmThen don't glue them to wood, fix them directly to the metal radiator.QuoteOr you could use the waste heat to heat the water for your house.Just to clarify, stick the solar panels to radiators which you pump cold water through which is warmed to go to your house's hot water system. You boost the efficiency of the solar panels and save money on your heating bills.

author: Lightages
author_rank: Unknown
timestamp: April 11, 2011, 01:26:55 am
content: As is usual, there are other forums with a wealth of information on these things. The general consensus is that the energy required to move the water to cool things or the cost of the system to do so far outweighs any advantage in the efficiency gined by doing such cooling.In other words, you use more energy trying to cool the panels than you gain.Don't bother. Just make sure you have no other sources of heat causing temperature rise and provide enough air space for natural cooling.

author: Simon
author_rank: Unknown
timestamp: April 11, 2011, 05:49:10 am
content: Quote from: Hero999 on April 10, 2011, 09:48:49 pmThe cells have metal contacts on the back and any glue would have to have good heat transfer specs. what type of radiator are you thinking of ? Still it's a lot of work and cost that has little justification.My main question was suggestions on materials to make the panel construction from and info on the efficiency versus temp. From what the PDF linked to said its something worth worrying about but i only want to go as far as passing air.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 11, 2011, 08:00:53 am
content: ask admin. i think he still has the solar with water cooled on his roof.

author: david77
author_rank: Frequent Contributor
timestamp: April 11, 2011, 09:40:09 am
content: I haven't done any research on the topic, however looking at the thousands and thousands existing installations all over the place I have never seen or heard of a domestic solar (PV only) installation where the cells were cooled in any way. They usually just slap 'em on the roof.If it was viable and would cause any significant rise in efficiency to cool the cells, it would have been done already, don't you think?

author: Simon
author_rank: Unknown
timestamp: April 11, 2011, 11:47:12 am
content: well it may be that companies do not like to complicate their installations. remember many are just paid by the government, they won't get much for making the panels more efficient

author: david77
author_rank: Frequent Contributor
timestamp: April 11, 2011, 12:17:18 pm
content: That may be the case, true.But how much do you think you could gain by cooling the cells? Something like 2%? And what's the investment to cool them? You need fans and the construction of each "strip" will be more complicated surely. Then of course a standard axial fan usually has a rated temperature of max. +70°C (Sunon) and then there's winter and damp...I don't want to be negative, just pointing out things that pop into my mind thinking about your project.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 11, 2011, 03:21:00 pm
content: coil/circuit burnt... maintenance etc.

author: david77
author_rank: Frequent Contributor
timestamp: April 11, 2011, 04:01:29 pm
content: Another thing... what dimensions are your solar panels going to have?If they're long and slim as I imagine them, you'd probably need quite powerfull fans to suck enough air through to get any meaningful cooling effect anyway. The standard axial fan can suck a fair bit of volume, it's useless at pushing air through a tubular shaped enclosure, though.And what about noise? These fans would produce quite a bit of noise I imagine.

author: Time
author_rank: Frequent Contributor
timestamp: April 11, 2011, 07:09:46 pm
content: Thermoelectrics:http://kammen.berkeley.edu/C226/5p.pdf

author: tecman
author_rank: Frequent Contributor
timestamp: April 11, 2011, 07:10:57 pm
content: There is some advantage of cooling the cells. Like any diode, it has a tempco of -2.2 mV/degC. Therefore they will output a decreasing voltage as they heat up. By cooling them, you will get a slightly higher voltage per cell if the temperature is reduced. Problem is the logistics of cooling. the ideal solution is to mount the cells to an aluminum plate and cool the plate with water. Issues are mounting, insulating the cells, etc. Also consider the energy gained compared to the energy lost to the cooling pump and any other devices needed to get rid of the heat.paul

author: Zero999
author_rank: Super Contributor
timestamp: April 11, 2011, 07:39:20 pm
content: Quote from: tecman on April 11, 2011, 07:10:57 pmYes, as far as I'm aware, that's why solar cells are less efficient at higher temperatures.QuoteYes, that's similar to what I'm suggesting, except maybe the expensive aluminium could be replaced with household radiators? The problem then is the reduced efficiency does to the air spacing. Perhaps if the radiators and the backs of the panels are panted black there will be adequate cooling via radiation?

author: Unknown
author_rank: Unknown
timestamp: April 11, 2011, 09:37:11 pm
content: Build your panel inside aDavid & Nicole Jones patented solar spongethe dark surface of the solar cells will improve performance of the hot air collector. The airflow will aid in cooling the cells.Don't count on it entirely heating or powering that much however.