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. And 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.
In 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 of cell strings in modules, bypass diodes, and module-to-module and string-to-string mismatch, a small amount of shade typically causes a disproportionate reduction in PV energy production microinverters and power optimizers can limit the impact of shade to the individual shaded module(s). However, the times higher than the % of shaded area.
A PV or solar hot water system’s yield is always the biggest factor in whether the financial investment in the solar asset makes money or loses money. Accurate shade measurements and system planning are essential to maximizing and forecasting the yield of a system.
One way is to shop or top trees. Sometimes the tree needs to be removed altogether. Other times we lose an entire section of roof.
Keeping your solar monitored, clean and unshaded is a great way to ensure a highly productive and reliable renewable energy system for years to come. At HelioPower, we employ shading analysis tools to help us find an unshaded or less shading spot on the roof.
Contact us today if you think your system needs service!