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If you put your solar powered math calculator in your backpack it will turn off from the lack of sunlight needed to power the device. As you slowly open your backpack and begin to let sunlight in, the calculator will eventually turn on when the amount of sunlight is enough to power the calculator. Similarly, peak sun hours refer to the hours of they day where the sunlight is strong enough to power a solar panel. This is different from total sunlight hours, which is simply the amount of hours in a day when there is any sunlight.

The latitude at the equator of the earth is zero degrees. This is where sunlight strikes the earth most directly. Due to the earth's curved shape, sunlight hits at a various angles depending on location. As latitude increases, the further you are located from the equator and more variance you see in sunlight hours. The latitude of Coffeen is 39.1.

You will notice that the average peak sun hours for Coffeen change based on the type of panel being used. The reason for this is quite simple. A fixed panel does exactly what it sounds like, remains fixed in one position at all times. A 1-axis and 2-axis panels have axis that allow them to rotate. The 1-axis rotates with the sun's daily east to west movement while a 2-axis also adjusts for seasonal changes.

Looking at latitude, average peak sun hours and various data can obviously help when planning for your solar power needs. The one thing you can never fully account for is changing weather. Storms, rain, cloud coverage all have an impact on solar panel capabilities.

Using the latitude of Coffeen along with historical data of sunlight and weather patterns we can estimate that a fixed mounted solar panel will receive an average of 4.3 hours per day in this area. That number can be increased with better technology including add a 1-axis or 2-axis tracking mount, which would increase the average peak sun hours per day to 5.6 hours and 6.5 hours, respectively.