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How does shade affect solar performance?

Shade and Solar Performance

Insolation is the amount of solar radiation reaching a given area. Shade reduces the insolation (solar radiation) that reaches a solar PV (photovoltaic) or thermal array.  Your PV array only needs to be partially shaded to suffer significant production losses. Shading can literally determine whether the financial investment in a solar installation succeeds or fails.

solar performance is bad when your system is shadedIn typical installations, shade is caused by obstructions between the sun and the solar system like chimneys, trees, or buildings.

Shade patterns on an array change in complex ways throughout the day and year. The shape and location of a shadow is based on the shape of the obstruction, the location on the array, and the location of the sun.

Azimuth and elevation angles are useful for defining the orientation or direction of the sun, roof, array, or obstructions. The location of the sun in the sky varies in azimuth and elevation angle relative to the array. Shadows change location and shape as the relative position of the Sun changes.

The Sun’s trajectories through the sky, or sunpaths, are determined by the latitude/longitude and season.

Shade Impacts Solar Performance

There are many factors that reduce the production of a solar system and shade is often the biggest factor. A shaded system will always have a worse return on investment (ROI) than an unshaded system.

A small amount of shade may, at first, seem like a small problem, but because modules are typically connected in series, a small amount of shade can cause a disproportionate reduction in PV energy harvest. Microinverters and DC power optimizers can limit the impact of shade to the individual shaded module(s) and are a good tool to maximize production from partially obstructed skylines.

A PV or solar hot water system’s yield is always the biggest factor in whether the financial investment in the solar asset makes or loses money. Accurate shade measurements and system planning are essential to maximizing and forecasting the yield of a system.

One obvious way to reduce shade is to eliminate it altogether. Occasionally, a tree needs to be chopped or topped to make way for a solar array. Worst case, we can lose an entire section of the roof due to shading.

Keeping your solar monitored, clean and unshaded is a great way to ensure a highly productive and reliable renewable energy system for years maximizing ROI. At HelioPower, we employ shading analysis tools to help us find an unshaded or less shaded spot on the roof.

Contact us today if you think your system needs service!