Adam Plesniak: Sun-tracking, concentrating systems boost PV efficiency

my name is Adam plays niak I'm the director of R&D at Amex and we are here in Irvine actually at the campus of University of California at Irvine and we have two of our what we call systems and actually these are the 7700 systems installed behind me so these are providing power to the university through a partnership we have with them each a manic system is comprised of what we call 7 mega modules each mega module is about the length of the flatbed truck it's about 50 feet and is about 10 feet wide and each mega module is comprised of 36 single-lens Park Ches and each lens parque is about a square meter so each mega module here generates on the order of nine kilowatts of power when you put them all together in a form of seven you get roughly 60 to 70 kilowatts of power coming off of each one of these systems but right here is basically the hydraulic control system and this keeps hydraulic fluid in these cylinders and the hydraulic fluid is used to move the cylinders at the top of the system both in azmuth so in this direction and also in elevation in the in the elevation asmath of the Sun here the elevation angle of the Sun and then if you follow me around here we basically have some electronic control boxes here this is just managing power off of systems and one feature of our 7700 systems is the inverters this one is provided by select RIA are installed on the actual system so they twist with the system they move with it as it tracks throughout the day that's pretty much it for the base and then basically we have a very long pedestal here that runs the wiring and hydraulic lines up to the very cop at the top we have the hydraulic actuators and we have this big long what we call torque tube which is supporting structurally all the mega modules we saw from the front if the Sun is shaded with clouds the system has an algorithm in it that tells the tracker kind of where the Sun is it's an approximation when the Sun comes back out when we want to generate electricity there's a little sensor that's all the way up there it's between two of the mega modules that it's basically a collimated tube and sunlight comes down in it and it basically just lights up a couple diodes or photo sensors and it's the balancing of the current in those photo sensors which tells you that you're pointed directly at the Sun we are standing in front of one of the set a man X 7700 systems and I just want to talk a little bit about how we get from the solar cell to the module to the system so each solar cell in this system is is pretty small it's less than a square centimeter and it's just a little high-efficiency triple Junction cell above the cell is a lens that's about this big it's about 7 inches squared and there are 30 of those optics per lens park' here each lens park' is about a square meter and that's basically represented by the you know the square the square thing here there are 36 lens part k's per mega module and then there are seven mega modules per system and that's the full system so you could do the math there's a lot of solar cells in this system and a whole lot of lens bar k's it like I said the the solar cells are a triple Junction material it's a high-efficiency photovoltaic material and the lens bar-kays are made of a type of plastic so the efficiency of this panel is about thirty percent and that's one of the highest efficiencies your you're ever going to see in photovoltaics and it's because of the use of the triple Junction cell in an RD environment we've been able to get the efficiency of ammon X modules up to as high as as high as 36% using a 40% solar cell so you can think that if the cells improve an efficiency over the next couple years the modules will also improve an efficiency and yeah that's kind of the exciting part about CPV is the efficiencies continue to grow and we continue to find new ways to push module efficiency power production and hopefully push it to higher and higher limits we don't quite know where the top where the highest it could go is but one thing that's really critical about the M and X systems is we're using a type of photovoltaics called concentrated photovoltaics what that means is that we're concentrating the light before it gets to the solar cell and that comes with a couple key elements the first one is we only use direct sunlight the direct sunlight is the sunlight that's directly coming from the Sun to you and comprises anywhere from 85 to 90 percent of the full solar radiation you're getting here on earth 85 to 90 percent is direct sunlight so we're taking that light which is basically uni-directional and we're concentrating it with an optic which is the front of the panel on two cells onto the back of the panel so what's important about this is that you can only put these panels in certain parts of the world you can only put them in the parts of the world where they get a lot of direct sunlight that's where it makes the most sense so you can think the u.s.

Southwest is a great great area for for CPV and in fact is the area where a mean X has the most installed CPV there are other parts of the world be it in the Middle East North Africa region there are some parts of China there are some parts of Australia South America that are also really great for CPV another great feature of CPV the cell that we use is less temperature sensitive than silicon cells so not only can we go in really sunny direct radiation locations we can also go in really hot places and what you'd find out if you if you looked into it silicon cells don't perform all that well at really high temperatures they start losing a lot of efficiency so our cells lose less efficiency at higher temperatures makes them a great choice for really really Sun sunny arid dry climates

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