Shading is not good for Solar Systems!!!
It is most likely that – Shading is not good for Solar panels. Even if a small shadow is cast on a portion of the solar panel in your solar array, it can affect the output of the whole solar system. In most occasions, solar PV installed in our households, business and other organizations are made of solar panels (a group of solar panels is called ‘solar array’) and inverter. For technical reasons related to the voltage requirements of the system’s inverter, solar arrays are usually divided into ‘strings’ of solar panels. Small systems may only have 1 string, while large systems could have many more.
One string could consist of a single panel, but usually they have more. The string of panels can be related to a pipe and the solar power as crude oil flowing through the pipe. In traditional solar panel strings, shade impedes the flow. For instance, if shade from a tree is cast on even one of the solar panels in the string, the output of the whole string decrease to almost zero for as long as the shadow remains on the panel. If there is another unshaded string, although, this string will continue to produce power as per normal.
In extreme scenarios, a shadow does not necessarily need to fall on a whole panel– based on the technology used in the solar panel in question, shading of even just one cell could flatten the output of the panel and in turn the entire string. Many modern panels, however, come equipped with devices called bypass diodes which minimise the effects of partial shading by essentially enabling electricity to ‘flow around’ the shaded cell or cells.
Solutions to Solar Shading
- This is obviously the initial and most important method to prevent partial shading on your solar power system. It is of utmost important to regard all times of day as all season period of the year when during solar installation, whether some structures of things close by could throw a shadow onto your rooftop.
Solar system owners should also be watchful in expecting that there are no trees close by which could grow tall enough to eventually create shading. The lifespans of
solar systems are normally anticipated around 25+ years; this is the period most trees grow plenty.
Clouds can also cause shading. Clouds via the sky during the day can also bring about variations in system output, but these are basically inevitable. Amorphous silicon solar cells are said to be better at handling shading than crystalline silicon solar panels, but generally speaking the relatively low overall efficiency of amorphous panels means that crystalline modules are a better choice.
There are some other technologies under development that may offer high efficiencies even in inclement weather, such as ‘super black’ solar cells, but most of these are still either expensive or not yet commercially available.
- Use an Inverter that has MPP Tracking capability
Maximum Power Point Tracking (MPP Tracking or MPPT) is a technology that comes standard in most quality inverters. An inverter equipped with an MPP Tracker is able to ‘average out’ the difference between the current and voltage of two or more strings of panels, so that even if the output from one is sub-optimal, the system is still able to take advantage of whatever juice it is creating and add it to the more powerful string, producing a consistent, usable volume of power. Inverters without MPPT capability simply lose the output from the weaker string once it passes below the required output threshold.
An example of partial shading in a conventional multi-string inverter system.
Presentation on Solar Shading and Solutions
If you would like to understand more about the effect of shading on solar panels you can download a presentation prepared by Gem Energy Australian you can download or view the below file.