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Solar Power?

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And today closes out as the most productive day to date. Clear day with low humidity (less haze) yielded 127kWh. :wee: There won't be many like this over the course of the year. The low humidity days are in the winter when the days are short and the sun is low in the sky.
 
Jack Knife said:
my system will be installed Monday ( started) when everything is up and running I will add to the discussion.
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Why wait, let's get started now. How many panels? What power are they? What type of roof are they going on and what direction do they face? I gots to know.
 
280 watts is a strong panel, mine are 270's and they were pretty powerful at the time. My installer had just started carrying them when mine was done, before that he was pushing 220's. One question that I have that I wasn't astute enough to ask from the beginning is how much power will a 270 kWh panel produce vs a 220? I have had very few moments so far where my panels pushed over 220 kWh and I wonder it it was worth the extra expense of going with the 270's. Would the 220's produce the same amount of electricity, or would they make even less than the 270's are? However, the Primar 270's were even cheaper than the other manufacturer's 220's were. There are even stronger panels out there but the cost vs return on them diminishes rapidly.
 
A 220W panel that is 100% efficient will produce 220W/hr., a 250W will produce 250W/hr., etc.

Jack Knife's 23 x 280W panels will produce 6.44KwH if all panels were operating at 100% efficiency at the same time (since they aren't all pointing the same direction, that won't happen) If they were all facing due South, they'd be more efficient but he likely could not get as many panels on the roof.

If they are paired with a 5kWh inverter instead of a 7kWh inverter (cheaper for the installer if a lease) and, as a group the panels are operating over 77.6% efficiency the inverter is working beyond capacity. Inverters can handle operating at a bit over capacity for short durations. It varies by manufacturer and the ability for the inverter to handle the current and heat. Since the panels are facing S and SE I am guessing the installer is taking advantage of the roof facings as best as possible.

A 28 panel 220W system and a 22 panel 280W system can produce the same amount of power, one just takes a bit more roof space.

They now have 325W panels for under $300/each.
 
To get 100% out of a panel would one not need direct sun (sun 90 degrees from panel) on a 0% humidity day?
 
ABFer said:
To get 100% out of a panel would one not need direct sun (sun 90 degrees from panel) on a 0% humidity day?
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Yes. It's the reason you can find 6000W worth of panels and 5000W inverters paired all the time.

My roof is about a 30 degree pitch and the South facing has an unobstructed view of the sun (almost optimum for my area). My panels are 113% of my inverters' capacity.
 
EX396 said:
Yes. It's the reason you can find 6000W worth of panels and 5000W inverters paired all the time.
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OK, so at my peak thus far my panels produced about 225kWh but only for a short time. That is about 82% of the capacity of my panels. Let's say my average is 200kWh (strictly hypothetical, I could derive an accurate number if I spent the time doing it) but we know that my peak is 225 or so. Would 220kWh panels produce the same amount of energy as my 270's, or would they produce a max of 82% of that 220 (181kWh)?
 
ABFer said:
OK, so at my peak thus far my panels produced about 225kWh but only for a short time. That is about 82% of the capacity of my panels. Let's say my average is 200kWh (strictly hypothetical, I could derive an accurate number if I spent the time doing it) but we know that my peak is 225 or so. Would 220kWh panels produce the same amount of energy as my 270's, or would they produce a max of 82% of that 220 (181kWh)?
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I believe you are confusing Watts and kWh.

If you replaced each of your 270W panels with 220W panels, and they were of the same quality, same position, etc. you would get 81% of the power generation. (220/270)

If you replaced all of your 270W panels with 325W panels you would generate 20% more power. ((325-270)/270)
 
EX396 said:
I believe you are confusing Watts and kWh.
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You are right, I was. :duh:
What you are saying sounds logical since there is no way that I could have achieved ideal production conditions so there is no way that a 220W panel could have produced 220W at the times mine produced 225 or so.
 
ABFer said:
What you are saying sounds logical since there is no way that I could have achieved ideal production conditions so there is no way that a 220W panel could have produced 220W at the times mine produced 225 or so.
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Correct.

Basically, the solar panel manufacturers rate their panels by how much power they produce in a given lab test condition. All panels are rated at the same temp, certain air clarity, and certain solar insolation exposure. If that panel produces 280W in those conditions, the manufacturer can advertise that panel as a 280W panel. The conditions in your installation may cause that panel to produce some number other than 280 at the best of times, but that number allows you to compare 2 panels and their relative power production.

The better panels last longer and will produce closer to that advertised output over a wider range of conditions. They will also require less surface area per watt. A panel that produced 200W, 10 years ago might be larger than one that can produce 300W today.
 
June is over and rings in with 2.8mWh for a value of $337 worth of electricity. This is slightly higher than predicted for the month.
 
ABFer said:
June is over and rings in with 2.8mWh for a value of $337 worth of electricity. This is slightly higher than predicted for the month.
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so you get a check from the power company, or they credit your current bill.???
 
can't say for ABFer but on mine they credit it to your account and settle up in march.I am still not on line yet should be by the end of next week per Duke Power.
 
pro1driver said:
so you get a check from the power company, or they credit your current bill.???
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Mine settled up in May and I took a credit for the payout instead of a check...long story there I'll explain later. They bank the extra production and apply it later. I have electric heat and don't anticipate any extra at the end of the year.
 
July is over and the stats for the month are in. We generated 2680 kWh this month, which is about 90 kWh less than the forecast. That equates to $323+- of electricity. Total for the year is 14.43 MWh or about $1740 worth of electricity. July is anticipated to be the best month of the year so it's less each month from here on out.
 
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