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8lightminutesaway's avatar

Solar panel efficiency?

Asked by 8lightminutesaway (1413points) April 24th, 2008

If you have solar panels at different angles on your roof, would that lower the overall production of power? I’ve heard that if some cells are producing significantly less than the others due to partial shading or whatever reason, it acts like a sort of circuit, and a lot of energy is lost. Is this true? We’re building a solar house, and we’re just designing it now, and we want to know if we can have some panels at different angles on the roof, which would make some produce more than others at different times, but might be more aesthetically pleasing.

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9 Answers

Jdavis's avatar

ask the guys at SolarPowerRocks.com they have a lot of knowledge on this subject.

TrenchMouth's avatar

I second that link provided. The idea behind having multiple angles is that you want to have the best access to direct sunlight, which changes throughout the year, and more drastically in some areas than in others.

As far as overall efficiency is concerned, solar panels are not very efficient when it comes to how much is usable energy compared to how much hits the panel. There are new panels out there however that are much more efficient then ones made 10–15 years ago. Every little bit counts though, right?

gooch's avatar

No they are suppose to be at a specific angle facing a southern direction. I forgot the exact angle.

bodyhead's avatar

If you’ve ever seen a movie or tv show where they talk about the solar panels in the desert, you might notice that the solar panel farms all have servos on them in order to move the direction of the panel in order to harvest the most energy. I’m willing to bet that the energy they loose from turning on those motors to move the panels, they gain back through keeping the power intake optimized.

You do loose quite a bit of power because the roof is static and does not move. But, because it doesn’t move, if was any other shape it would probably get about as much power. As long as you have a full open view to the sun from the roof, you’ll probably be ok.

I wouldn’t take my word for it. I’d check with the pros like these guys have suggested.

Diavolicchio's avatar

The optimal angle at which to have solar panels mounted is in direct proportion to ones latitude. I’m at approximately 45’ N latitude in Maine, so the optimal angle for my panels would be 45 degrees.

As to direction, you should be as close as possible to facing True South (as opposed to Magnetic South which is 180 degrees on a compass.) True South for me here in Maine is about 196 degrees. It’s based on ones magnetic declination, which is determined by your location on the planet. You can calculate it by going here and then adding or subtracting the number you get from 180 (depending upon whether it’s a positive or negative number.) In general, in the US you’ll likely find yourself adding somewhere between 14 and 17 degrees to 180 to give you a True South of between 194 and 197 degrees on your compass, which will be slightly southeast.

Alternatively, you can go to a great website called PV Watts and simply choose your location, the wattage of the solar panel system you’ve got, the angle at which your panels tilt, and a few other variables, and it will determine for you just how much electricity your panels have the capacity to generate, and how much money you’ll shave off of your electricity bill each year by having your solar panels.

Hope this helps.

John

Rock2's avatar

Less than 10% typically. That is when they are new. They get worse as they age.

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icelopez's avatar

Efficiency of solar panel depends on how good your installer is or your where you purchased your solar system . Company takes care of design and installation depends of the roof of the client to maximize the energy coming from the sun to produce more renewable energy

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