Forum Discussion
pianotuna wrote:
red31,
What Vintage465 is saying is that he was ripped off. Panels are often priced below $1 per watt and that has been so for many years now.
Exactly, just making light of an ole adage/axiom/maxim!wa8yxm wrote:
3 tons wrote:
What he doesn’t attempt to make clear is, why do two different types of panels (differing in substrates and size) that are rated at the same wattage (i.e. Power) might produce results that are different than their manufacturer’s 100w ratings??
3 tons
The 100 watt rating of the panels is "Ideal conditions"
The roughly half that he observed is "Real Conditions".
This is well known.
FWIW, this assumed what is ‘well known’ may seem to be more than a minor revelation to the many folks who have read repeatedly that mono are more efficient than poly, and come typically at a premium over poly - but admittedly the world seems a bit Orwellian today - lol- I took his output for each panel and divided by the square inches of each panel. The Mono was more efficient per square inch than the Poly, but by less than 5%. The Poly provided more power because they were larger, e.g. had more square inches. My take on this is go with the cheapest (Poly) unless they are just too large to fit your area of application.
Bobbo wrote:
I took his output for each panel and divided by the square inches of each panel. The Mono was more efficient per square inch than the Poly, but by less than 5%. The Poly provided more power because they were larger, e.g. had more square inches. My take on this is go with the cheapest (Poly) unless they are just too large to fit your area of application.
Bingo, larger could translate into more capture area (??) - interesting, you may be on to something !!pianotuna wrote:
3 tons,
The 2 mono and 2 poly were all rated at 100 watts. The poly's out performed the mono's in all the tests. How does that make the results "ring hollow"?????
Well if you think about it in the sense of different kinds of light bulbs, yet rated at the same amount of lumens, it can get a little perplexing...- 3 tons,
I don't see it as perplexing.
The 100 watt poly is physically larger which we all knew.
The output when covered is higher from poly.
The output in haze is higher from poly.
The difference in size is not great. The difference in output is higher with poly.
The cost is lower with poly.
So, if I were to redo my system I would move to poly.
And if I were starting from scratch, I would use poly.
The only time mono might be better is if there were perfect solar conditions. But that option was not tested. - The 100w is under testing conditions of a solar lab, of xXxX amount of radiation per square meter
The testing specs are published and are the same for all panels
Just about the only way to obtain this in RV real world use is by camping on a mountain top at 10000 ft
The simple facts are the poly's have a larger surface area and out performed the monos in watts out put,
Now if you want to juggle the numbers, the mono panels put out slightly more power per square inch/foot/meter of panel area, so the mfg can legally claim higher efficiency (they never tell you , it is per square measured areas)
But for most RV owners that don't mean squat!
300w of poly will give the avg RV more power per day than 300w mono, and that is what we want, when we put solar panels on the roof jdc1 wrote:
When a regular panel failed, I just left it in place and glued a flex panel to it. I didn't want a flex panel sitting directly on my roof. They get very hot.
The lack of air circulation (flexible) at the bottom KILLS them.- Several problems with the testing.
First, there is no full sun test to see how close they measure up to their rated output. This would have been the most important test for me.
Second, the cloud conditions he shows are highly variable and there is no way to know how much time elapses as he changes between panels. I have real time output on my remote control panel and in those kinds of clouds the watt output is continually moving up and down as the clouds pass across the sun. Conclusion is that the variation in irradiance could easily be most of the difference in the output he showed.
Third, the half-shaded panel either horizontal or vertical is a non-issue. In all cases the output is less than or equal to one amp. Who cares? None of them in those conditions will make a difference to your battery bank at the end of the day.
Solar panel efficiency is calculated by dividing the rated output by the area of the panel. Since poly panels are larger than mono panels for the same output they are less efficient than mono panels.
I just got back from a weeklong trip to the edge of the Flat Tops Wilderness in Colorado. The elevation of the campsite was 9,500 feet, the trailer was pointed due South, the panels have a natural tilt of 5 degrees due to the slope of the roof and a 3 degree tilt to the sides due to the curvature of the roof. I have the capability to tilt further but chose not to for enhanced shoulder time. Noontime temperatures were in the mid-80s. Three of the days had on-off clouds, sunshine, rain, from late morning to evening.
As you all know, solar panels only produce what is used but here is my production for the eight days.
1.02 kwh, 71.7 ah
1.29 kwh, 92.1 ah
1.25 kwh, 90.2 ah
1.11 kwh, 81.8 ah
1.60 kwh, 115.4 ah
1.36 kwh, 97.3 ah
1.83 kwh, 132.1 ah
1.34 kwh, 95.2 ah
Four of the days I had peak outputs of 379, 383, 406 and 394 watts. This is pretty good for nine year old MONO panels rated at 370 watts. Don’t let anyone tell you that you can never reach rated output of your panels.
As far as mono/poly, buy what is on sale. There is not enough difference to matter. 12thgenusa wrote:
Third, the half-shaded panel either horizontal or vertical is a non-issue. In all cases the output is less than or equal to one amp. Who cares? None of them in those conditions will make a difference to your battery bank at the end of the day.
Yet the output from the poly panels was greater than from the mono panels by about 20% when vertically covered and 16% when horizontally covered. Going with 16%, here are some extrapolations.
You mention less than one amp--but now lets multiply by 5 hours. Assuming a 400 watt install, the return to the battery bank is now for mono about 15.6 amp-hours and for poly about 18.75 amp-hours. It is enough to keep the bank from self discharging in storage, and would meet 50% of the parasitic loads of camping for a day in my (rather hungry) RV. The poly wins by about 3 amp-hours.
The haze test showed increased output by about 1/5 more for the poly panels, so I have to disagree with your statement about there is not much of a difference.
I suspect that if it had been a totally clear day, that the poly would out perform the mono in real life, as opposed to laboratory measurements.
As to longevity, my panels are from 2005 and still, in a flat install, output 17 amps (if the battery bank is hungry). The full output is rated at 256 watts in laboratory conditions (approximately 20 amps @ 12.8 volts).
I agree the testing is "back of an envelope" quality--and that he should have included a clear day as well as clouds traveling moving over the panels to show lens effects.
Even with these quibbles, poly is usually cheaper, and often gives more of a solar harvest. So, providing there is room, I believe poly is the way to go.
