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RFClark
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Alm,
Flat mounted panels are about 71% efficient. Panels angled for where you live are about 75% efficient. The correct angle is 15 minus your latitude
which for Cerritos is about 8 degrees of elevation on your panels. If you run your panels parallel and loose 80% of your solar you get nothing. If you
run series you get at least 20% or more of your output. Flatter panels output more on cloudy days as the lighting coms from overhead.
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Alm
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RFClark, JDCanuck was talking about 20% of "normal output" in overcast. Normal, meaning full-sun output. Yes, panel is not 100% efficient but under
ideal conditions it does produce close to 100% of what it says on the label. Less when it's hot, less when cloudy. If you lose 80% on a cloudy day,
this is still 20% of "normal" - or 10%, or 5%, depends on how cloudy.
With array of that size, series-parallel is the only way to go. The reason is monstrous 200-something amp current and 5-inch thick cable to
controller, if it were all-parallel  .
Yes, optimal tilt in summer is latitude minus 15 degrees. In winter it's latitude + 15. Optimal year-round tilt is close to latitude, about 20-21
degrees for La Paz. Canadians mostly stay there in winter, for reasons not related to weather.
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RFClark
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Today in San Felipe it was partly cloudy. Solar radiation was down to 500W/Sq Meter from a 1100W/Sq Meter normal high. Our fixed array was outputting
2KW which is 2/3rds of it’s normal mid-day output.
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larryC
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Quote: Originally posted by Alm  | RFClark, JDCanuck was talking about 20% of "normal output" in overcast. Normal, meaning full-sun output. Yes, panel is not 100% efficient but under
ideal conditions it does produce close to 100% of what it says on the label. Less when it's hot, less when cloudy. If you lose 80% on a cloudy day,
this is still 20% of "normal" - or 10%, or 5%, depends on how cloudy.
With array of that size, series-parallel is the only way to go. The reason is monstrous 200-something amp current and 5-inch thick cable to
controller, if it were all-parallel .
Yes, optimal tilt in summer is latitude minus 15 degrees. In winter it's latitude + 15. Optimal year-round tilt is close to latitude, about 20-21
degrees for La Paz. Canadians mostly stay there in winter, for reasons not related to weather. |
In my experience a solar panel will put out about 77% of its rated capacity in the real world and bright sun light. So a 100 watt panel will generally
produce 77 watts of power. Using an mppt controller will help a little, maybe 10% if you are lucky. If we were up north in cold country and bright
sunlight then panels will do better but almost never anywhere near 100%.
If you look at the output rating of a solar panel they almost always list the rating as "STC". That stands for "standard test conditions" which is
where a batch of panels are mounted in a large room and connected to test equipment and a large strobe light is flashed on them and the current is
measured and recorded.
A lot different than the real world usage but the only way they can control the test.
[Edited on 7-29-2022 by larryC]
Off grid, 12-190 watt evergreen solar panels on solar trackers, 2-3648 stacked Outback inverters, 610ah LiFePo4 48v battery bank, FM 60 and MX60
Outback charge controllers, X-240 Outback transformer for 240v from inverters, 6500 watt Kubota diesel generator.
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Alm
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| Quote: Originally posted by larryC | If we were up north in cold country and bright sunlight then panels will do better but almost never anywhere near 100%.
If you look at the output rating of a solar panel they almost always list the rating as "STC". That stands for "standard test conditions" which is
where a batch of panels are mounted in a large room and connected to test equipment and a large strobe light is flashed on them
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Finally . Yes, temperature matters. So does the tilt. Ideal conditions in real
world would be early summer with panel tilted "just right" - not at the fixed summer or winter angle, with cold wind so that the panel doesn't get
hot, and then at 1 pm you get 90-92% of the rated power.
MPPT - of course. With large array using PWM is impractical. MPPT could boost the total system output - not the panel output, it's still 90-something
of the nominal power at best. Panel temperature and high input voltage affect MPPT conversion.
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RFClark
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After a few weeks of operating our solar electric system I’ve made the following observations.
Flat mounted solar panels have a higher output on overcast days. Todays output at about 1/3 normal solar is about 1/3 of normal. They also have a
higher output (100% in 87 degree weather) while the sun is overhead or north of our location in BCS as it is about 6 months of the year. As the sun
moves south I’ll keep track of the output and back report here.
[Edited on 8-16-2022 by RFClark]
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JDCanuck
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Quoted: In my experience a solar panel will put out about 77% of its rated capacity in the real world and bright sun light. So a 100 watt panel will
generally produce 77 watts of power. Using an mppt controller will help a little, maybe 10% if you are lucky. If we were up north in cold country and
bright sunlight then panels will do better but almost never anywhere near 100%. end quote
We've been testing ours for about 3 months now. While we are having voltage issues on the one array, we are getting between 95 to 100% of rated power
on the fully operable array at peak period during the day (in our case 1:45 pm as they are not oriented perfectly for the 1:15 solar peak). At our
location the best we have had on a slightly cloudy full day was 5.5 times of full rating total power yield. Recently washed and still not using all
the power available as we have programmed the controllers for maximum battery life and they drop down 1 full volt to 51 volts in float mode from peak
of just over 52 volts when they go into absorption mode.
My rough estimate is there will be between 60-65 KWH power per day for our use on days like today once both arrays are fully remediated. so far we
have been limited to 58 kwh
Panels are these : https://energy.dmm.com/en/product/%e5%8d%98%e7%b5%90%e6%99%b...
and both arrays total to 10,920 full rating. We are running very close to 100% peaks on slightly cloudy days with 24 panels installed.
[Edited on 8-16-2022 by JDCanuck]
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