solar Panels (PV) and High Temperature  - Page 1
Forum section: electronics / general

author: jihad
author_rank: Newbie
timestamp: June 19, 2016, 06:24:35 pm
content: Hi allI live in Africa near the Sahara Desert. We get temperature up too and more then 45 Deg C, what effect this has on solar panels (PV) efficiency wise!Thanks

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 19, 2016, 10:10:57 pm
content: i think the issue is more of the electronic components, most of them will not work well operating at 50C. Solar panels themselves will do fine with the heat as they are supposed to have the sun directly at them. The main question is is the temperature from the sun shining directly or ambient temperature like when you're in the shade? make sure the plastic cover you use doesnt degrade under the sun.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 20, 2016, 12:06:39 am
content: Solar panel output power degrades with temperature. Current remains constant while voltage drops. The effects are pretty strong, with losses relative to 23C in the neighborhood of 25% at the temperatures you are likely to observe. I would also expect shorter cell life due to the high temperatures and also to the wider diurnal temperature swings you are likely to see. I don't have any numbers, but I wouldn't expect to see the normal 20-25 year lifetimes in your environment.

author: Marco
author_rank: Super Contributor
timestamp: June 20, 2016, 03:05:22 am
content: Don't the Panasonic HIT panels have really small loss of efficiency at high temperatures?

author: mtdoc
author_rank: Super Contributor
timestamp: June 20, 2016, 04:49:27 am
content: As others say, panel output drops with increasing temp.Panels nominal output ratings are based on standard test conditions (STC): irradiance of 1,000 W/m², solar spectrum of AM 1.5 and module temperature at 25 °C..A panels datasheet will list its temperature coefficient and usually show coresponing curves.Marco - I have 8 HIT panels - they have no special advantage re temperature that I am aware of.

author: coppice
author_rank: Super Contributor
timestamp: June 20, 2016, 04:54:49 am
content: Some people attach a pumped water circuit to the back of PV panels in hot places. This cools the panels, to improve PV output, and provides warm water.

author: Zeranin
author_rank: Regular Contributor
timestamp: June 20, 2016, 05:43:47 am
content: Quote from: jihad on June 19, 2016, 06:24:35 pmNot so different to the desert parts of Australia. Sure, efficiency drops off a bit at the higher temperatures, but the average annual irradiance is excellent, and more than compensates. Make sure to mount with a decent air gap under the panel to allow for air circulation, and you will turn photons into moving electrons like they were going out of fashion.

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 22, 2016, 06:25:45 am
content: So you're saying those voltaic cells voltage drop with increased temperature?Depending on the desert is the air hot or is it only the sun? Heatsinks can help if the air isnt hot during the way. As for water cooling if the pipes arent exposed to the sun than it might also work.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 22, 2016, 05:36:03 pm
content: I haven't gone back and checked the physics behind what is going on, but it does happen. Heat sinks and/or water cooling works, but they add cost and drop reliability. The real fundamental question is: Do you care about efficiency? As mentioned before, most places which have very high temperatures also have very high solar potential. You can get all the power you want. It is just a matter of cost. I strongly suspect that the right way to solve the problem is to add panels, potentially as many as 25% more. It will be cheaper and more reliable than trying to cool them.I am actually sure that if you run through the numbers (integrating solar availability over the day as modified by actual hourly air temperatures and expected solar cell temperature rise) you will find that the penalty is far smaller than 25%. It isn't that hard to do, but does take some time and research on your locations diurnal and annual weather patterns. Simpson integration in Excel is more than good enough.Don't forget to think about things like dust on the panel, and even worse salt water corrosion if you are in a coastal location.

author: mtdoc
author_rank: Super Contributor
timestamp: June 22, 2016, 05:57:09 pm
content: Quote from: CatalinaWOW on June 22, 2016, 05:36:03 pmThis is exactly right. Cooling panels with water has been tried and found not to be worthwhile due to cost and loss of reliability. Plumbing corrodes, leaks, etc. Pumps require maintenance.One of the great advantages of solar PV is that once properly installed, it requires very little maintenance. Depending on location, occasionally cleaning of panels is all that is required. Inverters (and perhaps charge controllers and batteries if present) - eventually fail (15 + years generally) - but PV panels themselves can be expected to give 25+ years of service with little maintenance. There are people using panels made 40+ years ago and still getting meaningful power from them.Panels are cheap now. Just add more.

author: System Error Message
author_rank: Frequent Contributor
timestamp: June 23, 2016, 02:29:07 am
content: Since this is a desert one thing you can do is make a water well and get a whole tank full of water. The water underground would be cooler and have a heatsink connecting to the water. Sure the water would heat up but at least you have warm water to drink/use. I guess water cooling only helps if it is tied in to the same water supply for homes,etc.If you mention the scale of this and whether this would be out in the middle of nowhere could be a factor. Dont forget sandstorms could cover the panels with sand but if the panels are smooth and angled that shouldnt be a problem.

author: coppice
author_rank: Super Contributor
timestamp: June 23, 2016, 09:51:54 am
content: Quote from: mtdoc on June 22, 2016, 05:57:09 pmAdding panels is a great idea if you have the space. Using crude electronics, and adding more panels to overcome its inefficiency, can make sense if you have the space. However, many people have a well defined space that is usable for panels, such as a roof. Getting the maximum energy out of that area can also be a great idea. One solution doesn't fit all.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 23, 2016, 05:01:00 pm
content: Quote from: coppice on June 23, 2016, 09:51:54 amTotally agree. Not so strangely, this is yet another problem where understanding all of the constraints and options and then thinking is a really good idea. It is possible to overthink, but thinking is almost always the fastest, cheapest and safest path to the best answer.

author: mtdoc
author_rank: Super Contributor
timestamp: June 23, 2016, 05:20:28 pm
content: Yes, it's true of course. One can only add another panel if there is a place to put it. But practically speaking that is rarely if ever an issue - at least IME. Any theoretical output gains from actively cooling panels with pumped water would be very modest (on the order of less than 10%). I've yet to see a case where adding 10% more PV is an issue.I have yet to see any successful implementation of active cooling of panels. It's an engineering idea that seems logical but has yet to be demonstrated as worthwhile. IOW, it sounds good in theory but .... IIRC there was a company that had developed a commercial product to do this but it went nowhere. Maybe someone will come find a way to make it worthwhile - but it hasn't happened yet that I'm aware of.And there are much better ways to heat water with the sun.And BTW - for an extra panel to give meaningful additional power it need not be in optimal orientation. In fact with panels so cheap now, what many are doing is setting up multiple arrays - one facing south (or north in the southern hemisphere), one west, one east, etc.

author: Marco
author_rank: Super Contributor
timestamp: June 23, 2016, 09:52:19 pm
content: Quote from: mtdoc on June 23, 2016, 05:20:28 pmAFAICS simply putting them all at a very shallow angle south would generate more power overall (google tells me horizontal only loses you 10% on average, but you need the shallow angle so rain runs off fast enough to clean it effectively).PS. forgive the Northern hemisphere centrism.

author: Lightages
author_rank: Unknown
timestamp: June 24, 2016, 03:08:22 am
content: LOL, "I live in the desert, what should I do to fix efficiency problems with temperature?" "Use water to cool them".

author: tszaboo
author_rank: Super Contributor
timestamp: June 24, 2016, 11:58:06 am
content: FYI you got reported to moderators for using offensive name.

author: Simon
author_rank: Unknown
timestamp: July 24, 2016, 12:01:51 pm
content: . I've been looking at the output of my own solar system lately. What I have noticed is that I will get 8 to 900 W in full sun but then if it clouds over when the clouds uncover the sun again the power output will jump to 1100 or 1200 W due to the fact they have had a chance to cool down. So it looks like I'm gaining up to 300 W when they are cooler. I'm not entirely sure how I would go about cooling them from behind as that surface hangs upside down so I either need to encase some water ducting or spray the backs of the panels. My thoughts were instead along the lines of putting a spray bar across the top of the panels and letting water run down them collected at the bottom pump it through a radiator and back to the top of the panels. If I do this with less than 100 W I would say that that is a substantial increase in power. As 200 W on top of my 800 W is an increase of 25%. In my case I am space limited as I have a great big tree in the garden which provides a lot of shade.I'm also wondering if there is a way of automatically switching panels in and out based on whether or not they are producing because they are shaded. I am going to assume that a panel in full sunlight is producing more voltage than one in the shade particularly if the same current is going through both because they are in series. So if I had panel redundancy say that in the morning one end is shadowed but in the evening the other end is shadowed I could detect when the panels have become shadowed and switch them out but switch in the ones that are in the sun. I suppose a lot of Opto coupling is going to go on to do this or perhaps just good old mechanical relays. The other option I suppose is to know the shadow profile of my garden and time the switching in and out of panels but that will be more difficult as you can never take into account the time of year very easily.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 24, 2016, 02:34:01 pm
content: There are many commercially available controllers which operate on a panel basis. They do everything needed to switch panels out when they are shaded.

author: wblock
author_rank: Regular Contributor
timestamp: July 24, 2016, 05:09:04 pm
content: What about adding a black panel on the roof at the top of the PV panels? The heat would create airflow under the panels for cooling. Passive, and no calcium deposits.

author: Simon
author_rank: Unknown
timestamp: July 24, 2016, 05:20:48 pm
content: Quote from: wblock on July 24, 2016, 05:09:04 pmI don't think that will work. It would not create enough airflow and you are out in the great outdoors so natural wind caused by shading et cetera would make more of an effect. Calcium deposits will be less of a problem as the water would flow continually washing any deposits away or preventing them even starting. However I'm yet to determine if having a coat of water on the panel will reduce its efficiency. Obviously there would need to be a tank for sediment to fall to the bottom of that is emptied now and then.

author: kaz911
author_rank: Super Contributor
timestamp: July 24, 2016, 07:58:02 pm
content: 50c ambient means cells are close to 100-120 deg c - and you loose a lot of power at 120.I did a lot of experiments in the UAE with up to 52c - and the only viable thing to do is use thin film which is not as badly impacted or use heatsinks. But there are cells in development for hot climates. Masdar Institute of Technology has done some more efficient cells for high temperature.

author: rfbroadband
author_rank: Unknown
timestamp: July 25, 2016, 11:11:19 pm
content: The solar cells have a negative temperature coefficient, thus in the summer (at higher temperatures) you will get a lower peak power out of the system than in the spring or fall. Thus in the summer you will have more sun shine hours at lower peak power vs fewer sunshine hours at higher peak power in the spring and fall.Attached are two photo's showing the temp of one solar panel in August in Austin, TX at 9am and 3pm to give you an idea on the change of surface temp of a panel during a hot summer day.

author: kaz911
author_rank: Super Contributor
timestamp: July 26, 2016, 06:41:08 am
content: there you are measuring the glass and not the element. So glass is reflective and not the best for measuring cell temperature with an Infrared meterCheck the temperatures below - they are a lot higher.I did my measurements with a K probe on the back of the cell mounting. With a heatsink on it I could get the temperature down by about 20c in a mild breeze - but that would then add about 5-15 kg to each panel and overall efficiency of the heatsinks would probably go down with all the cells having heat sinks.

author: navrattan.himansh
author_rank: Newbie
timestamp: August 03, 2016, 07:32:07 am
content: If you look at the manufacturer's data sheet you will see a term called "temperature coefficient Pmax". For example the temperature coefficient of a 190 W (monocrystalline) solar panel is –0.48%. What this means is that for each degree over 25?C … the maximum power of the panel is reduced by 0.48%.So on a hot day in the summer – where solar panel temperature on the roof might reach 45?C or so – the amount of electricity would be 10% lower.Conversely, on a sunny day in the Spring, fall, or even winter – when temperatures are lower than 25?C – the amount of electricity produced would actually increase above the maximum rated level.Therefore, in most northern climates – the days above and below 25?C would tend to balance each other out. However, in locations closer to the equator the problems of heat loss could become substantial over the full year and warrant looking at alternatives.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 03, 2016, 07:59:54 am
content: How much the efficiency goes down depends on the type of cell. Thin film cells tend to be more sensitive to high temperature. Special Cells (AFAIK GaAs base) can even be slightly more efficient at higher temperature, but these are more suited for concentrated PV.So check the data for the moduls to have not to much degradation with high temperatures. It might also be worth allowing for good air cooling, e.g. by not keeping the wind away or avoiding high temperature from a dark area near by.As usual performance data are relatively optimistic - even in cold regions the cells can be well above 25 C in the sun.The high peak output for the moment when a cloud just gives free the sun is not so much because of the temperature, but there is extra radiation scattered from the clouds. So you get the full direct sun plus some extra scattered light.