A photovoltaic system uses sunlight and solar energy to generate electricity for our homes and offices. While they are a great source of green and renewable energy, shading and obstruction can hinder their energy production. A study on shading analysis for solar modules found that shading in solar panels reduces power output by more than 75%, even if only one cell is shaded. To better understand and address this issue, read on.
Why Shading Causes Energy Loss
In a solar power system, each module is connected in series, forming a link chain. Because each module is connected to another, whatever happens to one cell affects other cells as well. Partial shading of solar panels reduces their ability to generate electricity as they receive less solar energy. Because the other non-shaded cells are connected in series, they can only produce the same power as the shaded cells, even though they receive more sunlight.
Shading effects on solar panels output
What does this mean for solar energy efficiency? It has been suggested that the panel’s power output is reduced proportionately to the shaded area. However, this is not the case. Shading just one of the 36 cells in a small solar panel can reduce power output by more than 75%. Shading as little as 1/36 of the cells can reduce power output by 75%.
Approaches to reduce shading losses
Fortunately, there are a number of different mechanisms that can be used in a PV system to reduce shading losses. These include string arrays, bypass diodes, and module-level power electronics (MLPE).
Modules reduce the electrical current in the entire string and thus the output power. To counteract this, modules can be connected in series or in parallel. Modules in the same chain are said to be in series, while modules in different chains are said to be in parallel. All components along the same chain must have the same current flowing through them, while they may be different on parallel chains. Because modules in parallel strings can have different currents, shaded modules do not reduce the power output of modules in parallel strings, thereby mitigating the effects that a shaded module has on a PV system.
A bypass diode, as the name suggests, is a device that allows current to flow through shaded modules. With the help of a bypass diode, the current generated in the non-shaded cell can bypass the shaded cells. This means that the current generated in the unshaded cells does not depend on the shaded cells, it also means you lose any output generated by the unshaded cells.
Typical solar panels have three bypass diodes, which divide the entire panel evenly into three different strings so that even if one section fails or is shaded, the other two will continue to produce power.
Module Level Power Electronics (MLPE)
MLPEs are devices that provide advantages such as Mismatch mitigation, module-level monitoring, and increased performance in the shade. They are connected to individual modules and offer maximum power point tracking. There are two types of MLPEs: DC optimizers and microinverters.
- DC Optimizer
A DC optimizer increases the current output of a shaded module by reducing its output voltage. This allows the shaded module to adjust the current flowing through an unshaded module to maintain overall power delivery. A DC optimization system needs an inverter to convert DC power to AC power.
By connecting a small inverter to each module, the maximum output power can be increased. The microinverter allows each panel to convert DC to AC, and since their outputs are connected in parallel, one panel does not affect the other panels.
Shading is one of the most important factors to consider when planning solar panel mounting. Incorrect module placement or improper care can result in energy loss and cost overruns. If partial shading is unavoidable, there are ways to optimize the PV design for maximum performance. The position of the panels can be adjusted based on the shading angle, or connected in parallel instead of in series to compensate for the shading loss in case one of the modules is shaded. There is also an option to use additional tools such as bypass diodes or MLPE to ensure that the shaded modules do not interfere with the work of the rest of the cells. For the best solar panels in Nigeria, contact us now on 09067522620