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Old 07-29-2016, 09:12 PM   #1
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Default Solar panel output

Does anyone know of a baseline formula that determines the average output of typical solar panels? EXAMPLE: Each square foot of 12vdc solar panel produces about .5 amps (or 6watts), sunny day naturally.
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Old 07-29-2016, 09:20 PM   #2
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Googled "solar panel watts per square meter" and got this:

Irradiance is a measure of the sun's power available at the surface of the earth and it averages about 1000 watts per square meter. With typical crystalline solar cell efficiencies around 14-16%, that means we can expect to generate about 140-160W per square meter of solar cells placed in full sun.
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Old 12-30-2016, 10:01 AM   #3
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Full on sunlight with a clear sky and the sun directly overhead gives about 1000W/m^2 at a flat surface. However, the power also varies with the incidence angle. The cosine of the angle between the sun and the panel's normal vector (a line exactly perpendicular to the panel) must be multiplied by the solar power. The angle varies over the course of the day as the sun rises and sets, and then on top of that you have to figure out how many hours of sunlight you get on average at a particular location. As you can see it gets kind of complicated.

There is a website provided by the DOE which gives average daily insolation numbers that you can use for a pretty good approximation if you plug in the location. I think tables are available in both hours of sunlight and average power levels. Here it is:

That's the DOE National Renewable Energy Lab in Colorado.

Also I think the latest types of solar panels they are putting on houses now, the efficiencies are a little better, around 17% I believe.

For my house I calculated ROI on solar panels to be 5-7 years, but that's with state and federal subsidies and with NJ electricity prices which are nearly double the national average. If you are in Texas, for example, you get more sunlight at a better angle, but the ROI is more like 20-30 years. (Electricity there is around 10 cents instead of 19 and you don't get checks from the state).
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Old 12-30-2016, 10:28 AM   #4
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Originally Posted by power View Post
Does anyone know of a baseline formula that determines the average output of typical solar panels? EXAMPLE: Each square foot of 12vdc solar panel produces about .5 amps (or 6watts), sunny day naturally.

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Most solar panels now are open circuit voltages in the high 30's and output depends on panel efficiency, sky clarity(haze) angle and temperature. So there is no typical panel. Panel output varies greatly with temperature change alone.
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