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Forum Index : Solar : monocrystaline versus Polycrystaline ??
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I would be interested in hearing of peoples experience in directly comparing the two technologies. I originally did a bit of research into this, but there is not a lot of readily available knowledge out there to find. Apparently mono costs about 10% to 15% more, but is supposed to have about 10% to 15% higher efficiency and output for a given panel area. That sounds nice, and mono makes sense if you have a very limited panel area such as on a boat or camper van. But I have also read that mono works better with a clear blue sky, and direct sun, but any shading, even a single lump of bird crap, or a single leaf, can seriously degrades all that wonderful high mono crystaline goodness. Supposedly when the sky is a nasty dull grey, with 100% cloud cover, and conditions are truly awful, poly kills mono for output, even though neither can raise much above a few percent of full rated output on such a terrible day. For many of us, performance in the dim cold depths of winter is the really critical factor, where every single collected watt counts. And if the above is actually true, polycrystaline may be the better choice. I have also read that the two technologies are slowly converging in overall performance, and it really does not matter much which you choose. I have not had my system up for long enough to really be certain about all this, but I can say for sure, that on a dull cloudy Melbourne day, with no visible sun my almost flat polycrystaline panels easily beat low facing monocrystaline panels. My (up) panels are 8 x 250W polycrystaline, looking up at 70 degrees above the northern horizon. My (north) panels are 8 x 250W monocrystaline, looking 30 degrees above the northern horizon. I am located in Melbourne 38 degrees south latitude. I will be interested to see how it all works in winter. But as it is now (December) my (up) polycrystaline panels beat my (north) monocrystaline panels under any and all sky conditions and at any time of day. I also have a virtual tracker with east and west facing panels looking 30 degrees above each horizon, but that is another story. I would really be interested if anyone else has a combined mono/poly system for comparison between the two throughout the year. Cheers, Tony. |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1022 |
Hi Tony I have 9X250w mono crystalline panels (these were new) and 12X250w poly crystalline running on separate mppt controllers, the poly crystalline run there best at 60-70volts, could be the 30meter cable i use (they are secondhand some burnt spots on some panels) where as the mono set runs at 80-100volts. I get 2kw off each set on the average morning but around 48 degrees i loose about 400-600w from the mono crystalline. the poly crystalline are pulling there weight on the cloudy days, have not had them long enough to prove much yet. Once i hooked up 3 poly crystalline on with the 9 mono's, on a cool morning the best i could get from that was 61amp for a short time at 50volts so will have to wait and see how these 12X250w poly crystalline go in the winter. Cheers Aaron Cheers Aaron Off The Grid |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Thanks Aaron, it sounds like we have fairly similar systems. Pretty happy with how it works in summer, in winter we shall see. Cheers, Tony. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
My memory of the old days is that there were not a lot of options for solar controllers or grid inverters and they had some pretty tight criteria as to what combination of panels could be hooked to them. Most of them were designed around 80 watt 12v or 160 watt 24v mono's We needed to get close to the max amps but stay under the max OC volts for the coldest sunny day possible. That was easier to do with 72 cell mono panels at that time compared to the bigger 60 cell polys. There was also the issue of what would fit, some roofs are just the wrong shape for big panels. we also had a hangup about being able to reach quite high equalization charge voltages on a couple of brands of lead acid battery. it always seemed a bit stupid to me that the whole system had to be designed to reach a high voltage at any given moment when in reality it was just a few amps needed for a couple of hours once a month. With modern panels and larger installs there is not much in it efficiency or price wise, however like most things the devil is in the detail. Sloppy system design or poor workmanship and sub standard components downstream will sabotage the output of any panel. I'm confused, no wait... maybe I'm not... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes indeed, the whole system needs to be very carefully thought through if problems are not going to arise. Its really the entire combination of panels, controller, and battery. All three have some fairly complex specifications (and limitations). Cheers, Tony. |
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| HankR Senior Member  Joined: 02/01/2015 Location: United StatesPosts: 209 |
Too bad you don't have the panels comparably oriented for a direct comparison. Are the poly ones intentionally pointed high up to perform better by gathering more whole dull-sky diffuse radiation, or just to generally do better in the summer? Dull or bright, it would seem as if your polys are much better oriented for summer sun angles. What is the comparison between the two with a perfectly clear sky at midday or thereabouts? |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
My original goal was to collect the most possible power in mid winter, which in Melbourne means a lot of very dull grey cloudy days, with the sun mostly in the north east, north, and north west at low elevation. The optimum panel elevation for direct mid winter sun here is 61 degrees (panel facing thirty degrees above the north horizon). So that is how I installed my monos. Its pretty obvious that with a clear blue sky, you cannot beat facing straight towards the sun. But with 100% very thick cloud cover, with only very weak diffused light, the sky is equal grey in every direction including due south. There may be only 10 watts from a 250 watt panel. And you will find that power peaks when pointing straight up, where the panel can "see" the maximum sky in all directions horizon to horizon. My polys work better than the monos in total cloud, the worse the conditions the bigger the difference. In very light cloud or no cloud the monos are better. But in those conditions I have more power than I can possibly use anyway. [quote]What is the comparison between the two with a perfectly clear sky at midday or thereabouts?[/quote] That is difficult to answer because my monos are 200 watt and my polys are 250 watt. And they have never had direct back to back testing at the same time under identical conditions. But after eighteen months practical experience, In mid winter the low towards the north horizon facing monos win in a clear blue sky. The pointing straight up polys win in that awful grey Melbourne mid day twilight. In summer the facing straight up polys win because the sun is almost directly overhead, and straight up is very good, and the poly panels are larger and more powerful anyway. But there is so much power at the mid day peak, its pretty useless. Cheers, Tony. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I had 2x 250w polys with the 'wrinkly' surface on my old 4x4 for camping- obviously mounted flat (altho I could quite quickly take them off the roof and prop them on the ground) I found that the small gain I got from tilting them didnt really justify taking them off the roof- only gained less than a couple of amps (into 12v- 3x120ah deep cycles) I was surprised not only by the power they developed on bright days, but even on the most heavily overcast days they would still put 5amps plus into the batterys, light overcast was barely noticable Most surprising was that while filling up at the servo at night, I looked at the reg to see a couple of amps being developed- from the servos high intensity lights!- even the yellow streetlights put a couple of amps out, which I found strange, I didnt think they would have been in the right spectrum to develop much power Overall I was quite impressed for a couple of chinese ebay panels, they certainly had no issues keeping the camping batts topped up and the 8kw (yes!!) chinese inverter has no issues running even quite large things (I used it to feed the house fridge and a plasma tv and microwave etc when we lost power after a cyclone up north- even ran a welder when camping to fix a trailer drawbar that broke off 4x4ing |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I have 3 separate arrays ATM, one 1500W and one 3000W both facing north at 26 degrees (our latitude) above flat and 5 KW laying flat. All are poly and there is little difference in output between the 4.5 KW of angled panels and the 5 KW of flat except when it is cloudy the 5 KW flat ones do slightly better. Only disadvantage of flat panels is they get dirtier. For anyone designing a off grid system, I would say aim for the best results on the worst days and the rest will be fine. There is absolutely no point in worry about what happens on clear days, there will always be enough power then. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
That sounds like a pretty sound philosophy Mad. I mounted my (almost) flat panels just below, and just in front of my sloping panels, so that when it rains the runoff from the sloping panels give the flat panels a good rinse. Cheers, Tony. |
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Clockmanfr Guru Joined: 23/10/2015 Location: FrancePosts: 429 |
I will watch this topic with interest to see what the TODAY consensus is! I have some amorphous silicone that have been operating for nearly 30 years, and yes they are still producing power. I went totally over to Monos with 14kW's worth in 2010. Why,? because the ambient light output was better than Polys in 2010. Normal dull day and I get 10% to 20% of my 13kW, so that's at worse, 1300 watts going in to my batteries. However, with the latest Polys, I am told they are slightly better in ambient light conditions, but I do not have any empirical evidence for Polys. Any one have any Polys? and test/observation data for Polys in ambient light ? Everything is possible, just give me time. 3 HughP's 3.7m Wind T's (14 years). 5kW PV on 3 Trackers, (10 yrs). 21kW PV AC coupled SH GTI's. OzInverter created Grid. 1300ah 48v. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
My camping panels are polys (admittedly a small array only, but they were for camping after all!) with the 'wrinkly'/non smooth finish- bitch to keep clean on flat panels- with 12v 500w (2x250w) chinese ebays with regulator (20a) into 3x120ahr deep cycle (yellowtop tubular ebay agms) I found little difference between flat roof mounting and tilting them (either by undoing the roofracks and leaning panels against the car, or parking near an embankment and driving over the edge when unpacked to get the tilt)- directly aimed at the sun got about 37/38A into dead flat batts/ heavy inverter load (ie hotplate plus fridge) sitting flat- about 35- hence me in the end not bothering with taking the roofracks off light overcast ie 100% cloud cover, no rain, diffuse shadows still visible- about 25A, varying according to coverage heavy overcast 100% cloud, occasional showers, no shadows visible- around 10A ultraheavy overcast- very dark day, continual light rain- unsteady 5a yellow streetlights or white servo lights- about 2A values from various notes made while camping various places/times and shoved in glovebox of the old car panels currently sitting on top of my boat waiting to go on new 4x4 (well new to me) |
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| HankR Senior Member Joined: 02/01/2015 Location: United StatesPosts: 209 |
Warp, I think you missed one of my questions (the first one): "Are the poly ones intentionally pointed high up to perform better by gathering more whole dull-sky diffuse radiation, or just to generally do better in the summer?" From what you said I guess you were going for getting something in grey winter sky conditions, but please elaborate if necessary. H |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Sorry I was not more clear. My original aim was (and still is) to get best possible mid winter performance throughout the short day for as many hours as possible. First came the low north horizon pointing monos. Next came an east west virtual tracker with monos. That gained me about an extra hour at each end of the day when the sun rises and sets south of due east/west and is actually BEHIND the north facing panels. I had read various reports and opinions on the internet that polys worked better in low light conditions, but monos work better with direct sun. So decided to add some polys pointing almost straight up. Personal experience supports all that others had said, that in twilight or very heavy cloud polys should beat monos, although the power you will get from either is extremely low. Solar panels are rated at 1Kw/sq metre insolation, which is about 20% more than typical direct sun in most parts of the world. So under those standard test conditions mono are supposed to have about 10% higher output than poly which is probably about right. What that does not tell you is how the relative outputs compare under very poor. light. That might be rather important in mid winter. Summer performance comes pretty much for free. If it works sufficiently well in mid winter, in summer you cannot fail to get enough power no matter what you have. If I ever add more panels in the future, they will all be up facing polys. Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
You also need to consider your climate, normal winters day here is blue skies 25 degrees and low humidity. Summer can in the mid 30's with high humidity to low to high 20's and a little to a lot of cloud. I have seen 3 KW of panels putting out under 10W at midday. So for us the shorter winter days are more than made up for with clear skies and cooler temperatures. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yes climate can be important. Even being on the opposite side of a mountain range can make a very big difference. My current system does not use a battery, so its important to get as many hours as possible from solar and as few as possible sucking from the grid. Any huge excess mid day power peak goes completely wasted. So its important to get as much as I can during gloomy days. Solar panels are now not that expensive, particularly second hand. Batteries are still a major expense. So optimizing the system for minimal grid use should also be much kinder to the eventual battery, and hopefully extend its working life. Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
University of Queensland Solar has lots of data on their solar panels. There is details of the brand and model of the panels as well if you dig through it. It may be possible to get some idea of the comparisons between different types. They have a huge number of panels across many different locations and have generated nearly 30,000,000 KWH's. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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