raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 18, 2019 13:23:54 GMT
****A disclaimer, this thread contains material and discussions that is "...dangerous and not productive...". I guess that warning should satisfy everybody. ****
I thought maybe a discussion about the solar panels would be in order. In my system, all my panels are monocrystalline. I have noticed that their seems to be polycrystalline panels, also. Has anybody used any of the poly panels, and what would be the consideration for a poly panel, besides the price difference.
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Post by tattoo on Aug 18, 2019 13:56:24 GMT
I thought maybe a discussion about the solar panels would be in order. In my system, all my panels are monocrystalline. I have noticed that their seems to be polycrystalline panels, also. Has anybody used any of the poly panels, and what would be the consideration for a poly panel, besides the price difference. You never cease to amaze me how little you know about your own system............
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 18, 2019 15:07:02 GMT
I thought maybe a discussion about the solar panels would be in order. In my system, all my panels are monocrystalline. I have noticed that their seems to be polycrystalline panels, also. Has anybody used any of the poly panels, and what would be the consideration for a poly panel, besides the price difference. Monocrystalline solar panels are more efficient than polycrystalline panels. But don't be concerned if yours are polycrystalline. a 100 watt solar panel is a 100 watt solar panel. The biggest advantage to more efficient monocrystalline solar panels is the size. The advantage of the polycrystalline solar panels is the cost.
So, if the cost is important and you have plenty of room, polycrystalline solar panels are fine. If you have limited space, such as the roof of your motor home, then monocrystalline panels may a better choice because they are smaller for a given wattage.
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 19, 2019 13:45:04 GMT
After reading some more of the solarpaneltilt.com blog article, it makes mention of insulation. Specifically, for my latitude, 42.48, the numbers derived are using ~5.7 inches of insulation. Has anybody even considered or even uses insulation for the panels. The use of insulation in an exposed to weather conditions, is a whole new topic in itself, I think.
I know the effects of extreme cold weather on a battery, how similar or dissimilar are the effects on solar panels. Not sure at what temperatures the panels start to lose efficiency. Is this even a point of consideration for my setup.
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Post by tattoo on Aug 19, 2019 14:10:08 GMT
Is this even a point of consideration for my setup. Nope none at all...........
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 19, 2019 18:54:09 GMT
Maybe somebody else has some pertinent information besides, "Nope none at all...........". Maybe Renogy has a comment that would help.
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Post by tattoo on Aug 19, 2019 19:10:33 GMT
Maybe somebody else has some pertinent information besides, "Nope none at all...........". Maybe Renogy has a comment that would help. We shall see.... But they are used to people trying to set there system up correctly.........
As far as my response?? When you don't read what people say what suggestions can people give you?? Other than none at all...... Now if you ever listen to what people are saying that would be different.......
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 19, 2019 19:48:27 GMT
After reading some more of the solarpaneltilt.com blog article, it makes mention of insulation. Specifically, for my latitude, 42.48, the numbers derived are using ~5.7 inches of insulation. Has anybody even considered or even uses insulation for the panels. The use of insulation in an exposed to weather conditions, is a whole new topic in itself, I think. I know the effects of extreme cold weather on a battery, how similar or dissimilar are the effects on solar panels. Not sure at what temperatures the panels start to lose efficiency. Is this even a point of consideration for my setup. At colder temperatures solar panels work more efficiently. They loose efficiency when they get hot.
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 19, 2019 20:05:07 GMT
I have my panels so they have some ventilation on the back side. I did notice that, when there is some direct sun on the front side, the backside of the panel itself gets hot. I might have to hang a dht22 on the backside, and see what kind of temperatures are really there. Now, at what temperatures should we see an efficiency loss, and how much. Hopefully it is negligible.
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 19, 2019 21:12:04 GMT
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raydas
Solar Devotee
Posts: 166
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Post by raydas on Aug 19, 2019 22:12:47 GMT
Thanks. A very interesting article. A couple of key points 77* F, and the Pmax rating. I went to the Renogy site and checked the specs for the 100W panel, no mention of a Pmax rating, and I rediscovered that the leads out of the panel are 12AWG. So I guess anything that connects to the leads should also be 12AWG, for max efficiency. I will have to do some research on efficiency of the panel as temps creep up past that 77* F mark.
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 20, 2019 0:13:16 GMT
When determining the wire size of an electrical conductor, one of the most important factors is the amount of current passing through the wire. You also need to know the length of the wire.
The longer the wire the thicker it needs to be for the same amount of current.
As you run more and more current through a conductor of a given length, the conductor needs to be thicker.
So, If you have a 100 watt panel and the specifications are:
Vmp 17.9 volt (optimum operating voltage)
Imp 5.72 amps (optimum operating current)
And the length of wire from the panel to the charge controller is 10 feet.
You can try different sized wires with the voltage drop calculator. You want to keep the voltage drop below about 4 percent.
So:
With number 14 wire:
Enter 17.9 volts, 5.72 amps, 10 feet (each way, so a 10 foot pair of wires), and 14 AWG wire into the online voltage drop calculator and it gives you:
Voltage drop: .29 volts voltage drop percentage: 1.61% (which is fine.) Voltage at the end of the wire: 17.9 volts
The wires on the solar panel itself may be 10 AWG and they are very short so we can assume that they will not cause enough resistance to matter. You don't need to match your wiring from the panels to the charge controller with the wires coming out of the solar panel.
Let's say you want to see what would happen with 14 AWG for 100 feet:
Enter 17.9 volts, 5.72 amps, 100 feet (each way, so a [edit] 100 [/edit] foot pair of wires), and 14 AWG wire into the online voltage drop calculator and it gives you:
Voltage drop: 2.98 volts voltage drop percentage: 16.14% (which is bad. In fact, I would expect the wire to get warm.) Voltage at the end of the wire: 15.01 volts
Clearly, 14 AWG is too thin for 100 feet with a 100 watt solar panel. Again, the short leads on the panel itself really don't make much difference, especially if they are nice and thick.
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Post by mediadogg on Aug 20, 2019 16:30:58 GMT
Enter 17.9 volts, 5.72 amps, 100 feet (each way, so a 10 foot pair of wires), and 14 AWG wire into the online voltage drop calculator and it gives you:
I think you meant to say, "100 feet (each way, so a 100 foot pair of wires)".
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russ
Solar Advocate
Posts: 63
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Post by russ on Aug 20, 2019 16:53:56 GMT
Enter 17.9 volts, 5.72 amps, 100 feet (each way, so a 10 foot pair of wires), and 14 AWG wire into the online voltage drop calculator and it gives you:
I think you meant to say, "100 feet (each way, so a 100 foot pair of wires)". Oops!
You are right, thanks for the correction!
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Post by Admin on Aug 20, 2019 23:10:38 GMT
After reading some more of the solarpaneltilt.com blog article, it makes mention of insulation. Specifically, for my latitude, 42.48, the numbers derived are using ~5.7 inches of insulation. Has anybody even considered or even uses insulation for the panels. The use of insulation in an exposed to weather conditions, is a whole new topic in itself, I think. I know the effects of extreme cold weather on a battery, how similar or dissimilar are the effects on solar panels. Not sure at what temperatures the panels start to lose efficiency. Is this even a point of consideration for my setup. inSOLation is different from insulation. The insolation is a measurement in kWh/m2 per day of solar energy. It's what allows the solar panels to absorb the solar energy and reflect back to the sun, as well as absorb and transform into electricity. This means that depending on factors such as: your geographic location/latitutde, temperature, air mass, and many real life factors, you will be receiving a modified version of your rated panel.
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