Providing a renewable energy source that is efficient and economical, solar panels continue to be increasingly popular with homeowners. In considering the solar option, one of the questions often raised is how it might be affected by shade.
When shade covers all or part of a panel, that cell’s energy is reduced. It then draws energy from the other panels, weakening the output of the entire system. In some cases, it could result in damage to the cell. However, the choice of product, installation and positioning can mitigate any such effects.
The Effect of Shade on Solar Panels
To understand how solar works, it helps to think of the string of panels on your roof in the same way you think of a pipe of water. Just as water flows through the pipe, so solar power flows through the system of panels.
Shade over a panel creates a block to that flow, preventing the unshaded cells from operating at their maximum capacity. It can also result in the creation of a hot spot on the panel.
There will always be days of soft shading from cloud cover and that is not a concern. It is the regular, harder shade that can sometimes cause serious problems.
This kind of shading could be from a large tree that is alongside or overhanging your home, it could be caused by a chimney, fallen leaves, or a nearby building that casts a hard shadow across your roof at certain times of the day.
The Cause and Impact of Hotspots on a Solar Cell
When the flow of power to a solar cell is blocked, that cell goes into ‘reverse bias voltage’. Put simply, this is the conversion of the current from the other cells into heat, creating a hotspot. This can lead to damage from burnout, the rapid degradation of the panel, and cracks in the panel’s glass.
How to Avoid Solar Panel Damage
1. Position panels to minimise any shading
Installation of panels should take into consideration any potential hard shading. The extent of any shade will differ at varying times of the day and may happen from one season to the next. A professional installer can determine the best possible positioning.
2. The benefit of bypass diodes
Most solar panels are fitted with bypass diodes, which enable the current to flow around a blockage. As a result, the creation of a hotspot is prevented. Regular maintenance will ensure that the diodes are working correctly and replaced when needed.
3. String inverters
A string inverter is connected to the string, or series, of solar panels. It converts Direct Current to Alternate Current electricity for the whole system. Most of these come with Maximum Power Point Tracking, a technology that minimises the loss of power from partial shading.
As alternatives to string inverters, other options are microinverters and power optimisers. If your roof shading is only slight, these may work best as they enable each solar panel in a system to function independently, so that the entire system is not compromised by just one or a few shaded panels.