Solar Energy Generation Systems – an overview by Specialized Solar Systems

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UNDERSTANDING VARIATIONS IN POWER OUTPUT

The power output from your system at any given moment will vary throughout the day, and the patterns and peak values will vary with the seasons. It is important to understand these normal variations in system performance.

Daily Output Power Profiles

The momentary output of your system depends on the angle of the sun and the clearness of the sky as well as the temperature and cleanliness of the PV module glass.  An ideal typical daily system output profile is shown below.

In the early morning, even though the day appears bright to the eye, the angle of the sun to the PV modules is very low resulting in a reduced output. As the sun rises, it moves more directly over the panels and the output rises to a peak value near noon. As the sun begins its decent, the angle of the sun to the panels gets lower and reduces the power output of the system.

Some actual daily profiles are shown here to illustrate the effects of sky conditions on output. Notice how the real profiles vary moment to moment compared to the smooth idealized profile. This is a truer representation of how your system output will vary during a day.

Seasonal Variation

During Winter months the sun shines for fewer hours of the day and has a lower angle in the sky. This results in a generally lower daily output profile than in Summer.

A simplified comparison of how output will differ from Summer to Winter.