littleharbor2
Solar Addict
If you had snow on the ground AND winter sun the Bifacials might be a beneficial option but without the needed sun they would be a waste.
Is price always the first consideration in solar panels?
- Thread starter Chester Gal
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Chester Gal
New Member
Very true advice. This is always in my thoughts when trying to decide which panel. This is why I am asking if the higher cost, higher watt bifacials will in real world output be a better deal? On paper they are not that far apart.
330 watt - 12 panels - 46.55Voc = 558.6V
385 watt - 12 panels - 48.0Voc = 576V
Chester Gal
New Member
Once again thank you!
I have the same problem with shading and did extensive research and like everybody says, the best approach is the chainsaw approach. But besides that, some other tips:
- you want the half cut modules, so you reduce the impact of shade on the panel. A normal 60/72 cell panel is divided in three sections so shade in any of the 3 sections reduces power by 1/3. Half cut modules are divided into 6 strings, so you have more granularity on the shading loss (1/6 of the power). If there there is just a little shade, it will lose less power.
- consider HIT/ multijunction panels. They have a better response to the light spectrum, specially indirect light, so that gives you an extra juice. However they are expensive, so it depends if you can find them used. There are several brands that produces it, but they are hard to find.
- instead of string inverters, you definitely should go the micro inverter direction. On micro inverters, each panel is independent, so shade on one panel doesn't impact the others.
One last thing to consider are thin film panels. The layout of the panel is different with the cell being a string that covers the panel from end to end, so they are more tolerant to shading. Here is an video of it:
The manufacture of the panel is out of business, but it happens that a solar farm close to you is selling all their thin film panels:
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The problem with these is that they are very high voltage ( ~80volts) and I couldn't find a microinverter that will work with them, other than the Enphase IQ7XS that is a custom made version for Sunpower https://www.facebook.com/marketplace/105527782815125. The max voltage is very close if not over the limit, but the panels are already 6 to 8 years old, so it may work.
Anyway, like I said I have lots of ideas about your situation. I also have some other leads of very cheap materials if you want to play with solar.
Attached is my house. The green trees are pines that I already took down, including some other trees. The shade still impacts my production early and late in the afternoon and on the fall months when the sun is down.
- you want the half cut modules, so you reduce the impact of shade on the panel. A normal 60/72 cell panel is divided in three sections so shade in any of the 3 sections reduces power by 1/3. Half cut modules are divided into 6 strings, so you have more granularity on the shading loss (1/6 of the power). If there there is just a little shade, it will lose less power.
- consider HIT/ multijunction panels. They have a better response to the light spectrum, specially indirect light, so that gives you an extra juice. However they are expensive, so it depends if you can find them used. There are several brands that produces it, but they are hard to find.
- instead of string inverters, you definitely should go the micro inverter direction. On micro inverters, each panel is independent, so shade on one panel doesn't impact the others.
One last thing to consider are thin film panels. The layout of the panel is different with the cell being a string that covers the panel from end to end, so they are more tolerant to shading. Here is an video of it:
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Anyway, like I said I have lots of ideas about your situation. I also have some other leads of very cheap materials if you want to play with solar.
Attached is my house. The green trees are pines that I already took down, including some other trees. The shade still impacts my production early and late in the afternoon and on the fall months when the sun is down.
Here is a thread on it #30865 https://diysolarforum.com/threads/why-not-cigs.30865/ but they are discussing the flexible models of CIGS, not this glass on glass module.
zanydroid
Solar Wizard
This isn’t exactly right. They are indeed divided into 1/6 sections. However they are connected in 2p3s not 6s. 6s implies 6 bypass diodes but there are in fact only 3 with half cut. If you have only 1/6 blocked you actually will bottleneck current on the other 4/6 that are series connected. If that is 100% blocked you get 0.5 Pmpp. So it is beneficial to switch to 2/3 voltage and get 0.66 Pmpp, no different than full cut. But there is a range of blockage where the half cut has higher power. 50% blockage on 1/6 will get you 0.75 Pmpp on half cut while full cut is still at 0.66 Pmp
Half cut also has a better shot of avoiding turning on bypass diodes which will reduce the thermal aging on them
Also half cut can be used to increase the voltage instead of providing a second current path. Much less common for residential but I think is a thing in utility panels.
I think there’s a durability impact from half cell (not sure it matters that much, i know it’s called out for third cut in some articles), and some people have theorized that the more complex I-V curve might confuse some MPPT strings. It is plausible but nobody has shown data.
Another thing to look for in panels (not sure if mentioned yet in the list) is approval for local use. This entails UL in all USA places and CEC in California.
Balrog006
Solar Enthusiast
Will the system be grid tied and selling back the excess in the summer? If yes then you’ll build up money or kWH credits to offset use in the winter when the production isn’t ideal-so properly sized a system will net you zero or close to it for the span of the year.
Chester Gal
New Member
Wow!
Wow! I can't thank you enough for taking the time to share your thoughts and advice.I have the same problem with shading and did extensive research and like everybody says, the best approach is the chainsaw approach. But besides that, some other tips:
- you want the half cut modules, so you reduce the impact of shade on the panel. A normal 60/72 cell panel is divided in three sections so shade in any of the 3 sections reduces power by 1/3. Half cut modules are divided into 6 strings, so you have more granularity on the shading loss (1/6 of the power). If there there is just a little shade, it will lose less power.
- consider HIT/ multijunction panels. They have a better response to the light spectrum, specially indirect light, so that gives you an extra juice. However they are expensive, so it depends if you can find them used. There are several brands that produces it, but they are hard to find.
- instead of string inverters, you definitely should go the micro inverter direction. On micro inverters, each panel is independent, so shade on one panel doesn't impact the others.
One last thing to consider are thin film panels. The layout of the panel is different with the cell being a string that covers the panel from end to end, so they are more tolerant to shading. Here is an video of it:The manufacture of the panel is out of business, but it happens that a solar farm close to you is selling all their thin film panels:
The problem with these is that they are very high voltage ( ~80volts) and I couldn't find a microinverter that will work with them, other than the Enphase IQ7XS that is a custom made version for Sunpower https://www.facebook.com/marketplace/105527782815125. The max voltage is very close if not over the limit, but the panels are already 6 to 8 years old, so it may work.
Anyway, like I said I have lots of ideas about your situation. I also have some other leads of very cheap materials if you want to play with solar.
Attached is my house. The green trees are pines that I already took down, including some other trees. The shade still impacts my production early and late in the afternoon and on the fall months when the sun is down.
View attachment 172758
Tl2300 low light full color time-lapse camera
HIGHLIIGHTS ♦Color high-brightness time-lapse video files can be captured under starlight or moonlight ♦Starlight angle of view: 110° ♦Starlight level 2 million Sensor, 1/2.7" ♦6 months (take a picture at 5 minute intervals, 288 pictures/day) ♦Support up to 512GB external TF storage card...
acpotels.com
This is the camera. I think this is the site I bought it from.
WindWizard
Solar Enthusiast
To me I would go for the $85 panels. I bought some used panels and they produce great. $85 is a great deal and it is hard to pass up on it.
I had a similar issue with the shading. I have my panels as 3 in series. Keep in mind that all it takes is for one of the panels with a little bit of shade, in a set of 3 to kill the power for the whole group. Shading is a much more important point than which panels to buy. Buy the cheap ones and a good chainsaw and you will have great power.
Chester Gal
New Member
No, the system will not ever be grid tied. But you are right about the very big plus of kWH credits. I'm part of a coop and my electric is pretty cheap compared to others and only receiving wholesale amt for credits is not worth the hassle of being officially grid tied.
Chester Gal
New Member
You are beyond wonderful for taking the time to pass this along to me. Definitely going to check this out. Sounds like it would answer a lot of unknowns. Thanks again!Tl2300 low light full color time-lapse camera
HIGHLIIGHTS ♦Color high-brightness time-lapse video files can be captured under starlight or moonlight ♦Starlight angle of view: 110° ♦Starlight level 2 million Sensor, 1/2.7" ♦6 months (take a picture at 5 minute intervals, 288 pictures/day) ♦Support up to 512GB external TF storage card...
This is the camera. I think this is the site I bought it from.
Thanks for the correction. You went to a higher level of detail that I ever could.
littleharbor2
Solar Addict
60 and 72 cell panels are actually a single string. PV cells put out somewhere over .5 volts. 72 cells in series yield something over 36 Vmp. 60 yield something over 30 volts. 120 and 144 perc 1/2 cut cells are basically two panels in one They should be mounted in portrait orientation. this will have the upper 1/2 of the panel out of the shadows when they creep up from the bottom of the panel.
Balrog006
Solar Enthusiast
Regardless of the amount of the credit, you are loosing production, ROI and value in a system that can be grid tied and earn credit but isn’t. Depending on how much you overproduce in the summer you could, despite the rate, offset some or all of your winter use. You are in essence turning down free money from your system and the sun once the grid tie expenses and process is complete.
Consider carefully wasting what you could produce, even if it could just pay for a month a year, that’s a month you don’t have to and after a few years that certainly adds up.
Chester Gal
New Member
I think I'm going with the cheaper panels. I appreciate that you feel the same. I was thinking about 4 in series with 3 separate arrays for a total of 12 panels. Each array would face a slightly different direction. SSE-S-SSW
Chester Gal
New Member
You are absolutely right! I made an off the cuff decision to not be grid tied, but you are right. I am going to investigate the process. Can you use used solar panels in grid tied systems? If they were UL certified to begin with?
If the panels are listed to UL 1703 or UL 61730-1 and UL 61730-2 you are good for a code compliant/permitted/inspected system off or on grid.
Chester Gal
New Member
You really are PVGIRL!!!!! I'm writing this down right now to check against the panels I'm going to buy. Thanks for the speedy answer!
Chester Gal
New Member
I checked this out. Very interesting! Definitely going to look into these. Thanks!
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