Do you REALLY get enough out of your solar panel?

[Music] foreign [Music] [Music] hi we've done a number of videos on solar power and I am continually doing experiments trying to improve the performance of commercial solar panels and solar cells this is one of those experiments and the results are pretty exciting solar power is a multi-billion dollar billion watt industry and slowly the manufacturers are improving the performance of solar panels and solar cells with better engineering and better chemistry but there is a fundamental limit on the performance of solar cells and it's unavoidable Heat the way a solar cell is manufactured is they take a substrate aluminum or plastic and they will deposit on it a thin layer of silicon that is doped with a different atom like aluminum or boron then they'll deposit a second layer of silicon that is doped with a different atom like phosphorus because of the different atoms present in the layers at the junction of the semiconductor a small electromagnetic field or potential is created so when a photon comes in from the Sun and Strikes the Silicon it can kick loose an electron and that field will urge that electron away from the depletion Zone at the junction and send it to the conductors that bleed it out as electricity now the solar silicon will respond to wavelengths between about 400 nanometers in the blue out to about a thousand to Eleven Hundred nanometers in the near IR but the solar spectrum is much broader than that and any of the heat or light that is absorbed by the panel but not converted into electricity is converted into heat in addition that process I told you about is not a hundred percent efficient some of those electrons don't make their way out and fall back into the depletion Zone creating more heat and that process is thermally dependent as the temperature of the junction Rises the heat causes the vibrations in the atoms to increase and it makes it harder for the electron to make its way out of the junction and into the conductors so solar cells become less efficient as they become hot and it's not just when they get really hot they start to become inefficient it's a progressive process all the way from the highest temperature that the solar panel can tolerate all the way down far below zero that's why solar cells are more efficient in the winter than they are in the summer the reason they don't seem to be is because the sun is hitting at a more oblique angle and you're getting fewer photons but the photons that do strike the panel are more efficiently converted into electricity therefore when you are engineering or building a solar cell array you want to do everything you can to passively keep it cool for example if you mount it on your roof and you paint or coat the roof with a highly reflective paint or coating that sends most of the solar heat away you don't create large clouds of hot air that waft around the array that's sitting on top of the roof if you take the panels themselves and mount them you want to mount them in such a way that you have a lot of free air space around the panel so that you get convective cooling because the panel when it's operating is always going to be at a higher temperature than the surrounding air what we're doing in this experiment is testing whether or not active cooling can lower the temperature of the junction sufficiently to boost the efficiency of the whole apparatus enough that we can more than drive the cooling system and get some net benefit out to do that I took one of these solar panels we obtained last year on Amazon from a company called wise w-e-i-z-e they're pretty nice panels they're sold in pairs at 170 dollars a pair and each panel is rated at 100 Watts that's at noon on the equator here in New England 60 to 70 watts is more typical what's nice about the panels is they have a stamped aluminum frame around the outside that gives it rigidity and mounting points but it also creates a space between the panel and the edge of the frame that we can use to build an air duct and that's what I did now on the back of the panel we're going to be testing I took a one millimeter thick sheet of aluminum and attached it to the sides and left a small Gap at the top and a large gap at the bottom they're farther from the fans and the combined area of those two gaps is equal to the combined area of the three ventilating fans the fans are pretty impressive they're from a company called Orion and they are 12 volt DC wash down fans so you can spray them with a hose it can rain on them they're perfectly fine and they're very efficient when run at 12 volts each fan will consume 5 watts and produce 120 cubic feet per minute of airflow that's each however as you lower the voltage the power consumption drops more quickly than the flow when you bring the voltage down to six volts which is The Sweet Spot each of the fans will draw approximately one watt but still move 60 cubic feet per minute so when we set this thing up and tested it we found that the results were a little equivocal not that impressive the problem was that the surface area on the back of the panel wasn't sufficient to interact with that airflow we needed more surface area to do that I put these fins on the back surface to increase that surface area now if I was to use a commercial heat sink or heat spreader like this we would triple the cost and the weight of each of the of the panels so I decided to make it myself I took the same one millimeter thick sheet aluminum and I have a friend that has access to a sheet metal shear and a press brake and so I trimmed out a whole bunch of strips and then put them in the brake and bent them into these right angle shapes like this two centimeters by three centimeters two by three and the first couple took me about 10 minutes to kind of figure everything out but once I got rolling I could make two or three very long strips per minute made over a hundred in one hour now if you don't have access to that kind of equipment you can find a local Job Shop or a machinist that will do this for you you'll pay more than just the stock aluminum but they're probably better at it than you so they could probably produce even more of these pieces of metal and it's certainly going to be a heck of a lot cheaper than doing something like this we then applied those strips to the back of the panel using some of our thermal epoxy and then retested it now you might notice this articulating frame that I have here this was built for tracking experiments for solar panels and other things we'll get into that later but in this case we're going to be operating it manually and the purpose of this is to keep the panel aiming directly at the sun you want a normal or a perpendicular from its surface to be directed directly at the disk of the Sun so we don't get any foreshortening during the few minutes the test during the test that the sun is moving across the sky I'll show you the little technique that I use to do that but every couple of minutes I'm going to be tweaking the panels a quarter of a degree or so to keep things bullseye on the Sun now the instrumentation we're using includes a thermometer over here see if it's on yeah and the number in the lower corner represents the temperature of the box that we really don't care about because it's baking in the Sun the larger number up here is being fed from the thermocouple that has been glued to the back surface of the panel so it's the panel temperature that's the number we care about this is the power meter the power is fed from the panels into this meter and it will read volts amps and in this lower corner down here the combined product Watts that's the other number that we're going to care about the power is then LED out of the meter into a resistor array that provides the load I did some experimenting and discovered that these panels are pretty forgiving they will produce near Peak output over a fairly broad load range but it Peaks around 7 ohms so I took seven one ohm ceramic resistors wired them up in series to produce a 7 ohm load and then put the whole thing down in a bucket of water to act as the heat sink it works well you might wonder why we're not using a charge controller sort of an Adaptive controller because one of those controllers by adapting the resistance perfectly for conditions could probably tweak another watt or two out of the panel problem is the algorithms what drives the function of the of the machine is not accessible to us it's sort of black box so if it's making changes in the the load it might interfere with the results and because we're being we're doing a comparative test this panel same conditions just a change in temperature this does a very good job of doing that comparison without adding an additional unknown of the charge controller this is the power supply that drives the fans in theory DC fans DC output from the panel we could drive the pan the fans directly from the panel but this allows us to adjust the voltage perfectly for what the fans need as well as dissects out the amount of power that the fans are consuming relative to the amount of power change we're getting in the panel due to temperature now let me come around here and show you the last thing I have this reflective insulator put in front of the panel so that while we set up and while I was talking to you we didn't heat soak the panel and started at an elevated temperature and then when I take this off we're going to note the temperature let me turn this back on because it it's got an auto shut off here which is 19.3 degrees and we'll notice the initial power when the panel is as cool as we can get it that's starting ambient temperature this is the alignment technique I have a machinist's Square I place it on the front of the panel or on the insulator which is lined up with the panel and as I move this back and forth in the sun you can see the shadow is moving past the vertical and if I move it up it does the same thing and down the same thing when I line everything perfectly this Shadow will disappear because it lines up with the vertical like that that is the starting position and that's where we're going to begin the test and that's what I'm going to be doing every couple of minutes just to make sure we stay perfectly aligned so when I pull this off on three let's notice the power output with the cool panel one two three get my head out of the way and what do we got 69.68.8 Watts and you'll notice the temperature is already fairly rapidly Rising there are panels out there that attempt to do something relatively similar they're called photovoltaic thermal panels and they use a whole series of tubes on the back of the panel to circulate water to carry away the Heat and there are some DIY channels that have done something similar where they put drip tubes across the top of the panel and actually flow water over the panel they're waterproof they can be rained on it's perfectly fine and it has the added advantage of keeping the panel perfectly Clean and Free of debris we decided not to do it for this reason water is an excellent heat conductor but itself it's not a heat sink and so if we don't have some way of dumping the heat the water will just continue to rise in temperature until eventually it gets to the same temperature of the panel and doesn't do any cooling we need to dump that heat and so if we dump that heat with it water to air heat exchanger like a car radiator we not only have the power requirements of driving the fans that do the exchange as well as the water pumps that move the water potentially lowering the overall efficiency if you were lucky and you had a lake or an Artesian well next to you and you could use that instead of the heat exchanger the problem you get to there is it's at a fixed temperature which obviously has got to be above freezing and so if you start circulating that water from that Source eventually when the air temperature drops below freezing and continues to drop it will actually act to warm the panels and lower the efficiency so we decided to stick with a simpler leak-free system that potentially is more efficient now if we look over here just before we start letting this heat soak you can see that we've gained about seven degrees and we have dropped about two Watts we're going to give this a little while to equilibrate and we see where we get to once this thing heats up [Music] okay you can see that the temperature has risen to almost 53 degrees and the power has dropped to 58.7 Watts from 68.8 Watts so we've basically lost 10 watts of power and we have risen about what 34 degrees something like that now I'm going to turn on the fan and we're going to see what happens okay six volts fan coming on okay and you can see that the temperature is already starting to drop let's give this another few minutes to equilibrate and see where we get to foreign [Music] we've given this a few minutes to equilibrate and you can see that we've dropped the temperature down from about 53 degrees to about 39 degrees and we have increased the power from 58.8 watts to about 63.4.6 Watts so we've gained about five and a half Watts for an investment of about three watts in power pretty significant Improvement in the performance of the panels by simply using the fans it really does work you can actually get more power out than you put in I like that the problem is the engineer is going to say something else they're going to say well for this modest power gain is it worth it does it make sense is it worth doing and I think it is the first argument is panel longevity solar panels degrade over time some of that is due to humidity some of it's due to just the photons hitting the surface but the biggest killer is heat the number of hours spent at any given temperature and it isn't linear if you're running a panel temperature of 50 to 60 degrees the degradation rate is about half a percent per year if you go to about 80 degrees Celsius the rate increases to about one percent per year and if it gets to about 95 degrees Celsius it jumps to about two or three percent per year that's a fairly significant increase now as you can imagine if you were to install say a twenty thousand dollar system on your roof that was designed to last for say 25 years and you could get five or ten more years of life out of the system that may more than justify the purpose of putting in the in the fan system however you might argue that all right the twenty thousand dollars isn't just paying for the panels it is paying for the panels but also the installation costs and the replacement costs and the real cost of your system is probably not as low as 20 000. if your neighbor's taxes are being used to subsidize your panels you're paying more because your taxes are being used to subsidize their panels in addition these things contain heavy metals and so when you dispose of them it's not free the second argument is we are actually making more power and that Improvement in power means you can either run your toaster more often you could run your air conditioner more frequently or you could buy a slightly smaller system and get the same amount of power out and this test is an extremely conservative test here in New England we don't get a very high Photon flux you know 60 70 Watts out of a 100 watt panel but in areas of the world where solar power makes more sense Southwest U.S the Mediterranean Australia in those conditions the panel temperatures are running much higher than this 20 30 40 degrees celsius higher and even though the air temperatures there are higher they're not 20 30 40 degrees celsius higher if they were in some of those areas you'd be dead so with a higher temperature differential between the panel and the air the same fan system will carry away more heat and so there will be a larger differential between a passively cooled panel and an actively cooled panel and the final argument is that if I was going to install these things on my roof put 40 of these panels up there I wouldn't install 120 of these tiny fans and as fans increase in size they increase in efficiency so if I double the diameter of one of these fans I'll get four times the airflow but maybe only invest three times as much electrical current the point being that a smaller number of more efficient fans is easier and it's more efficient so it's kind of a good deal you could even potentially use a number of large blowers to ventilate multiple larger units making it even easier to do so with all those arguments you might say well if it's a good idea why isn't anybody doing it point is somebody is there is a company out of Australia called sunivate which is doing exactly this they use a slightly different design in the cooling system but they're doing direct air Cooling and they even tout in their literature that if you're doing a big industrial setup you could use some of that waste industrial heat for other purposes drying wood making paper but even if you just dumped it into the atmosphere it still makes sense so we wish them luck and any other companies that decide to add this as a feature to their existing panels but as I've shown you it works it's not difficult to do you could do it yourself so hopefully you found this interesting and potentially maybe even useful and if you like the kind of stuff that we're doing on this channel please take a second and look at some of our other videos we've done some pretty interesting things and if you're willing to please subscribe because if you do it helps the channel to grow and the bigger we get the more we can afford to do both the equipment that we buy and the labor that we use to produce the videos in any case I want to thank you for watching you have a wonderful afternoon and we'll see you soon thank you

Channel: Tech Ingredients

Views: 379,538

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Id: Mt9qLRN7JvA

Length: 21min 0sec (1260 seconds)

Published: Sun Jan 08 2023