Solar panels are the best way to generate renewable energy, but they can be affected by shading. When a solar panel is shaded, it produces less electricity. This is because shaded cells cannot generate power. This results in an overall production output reduction of the panel and the solar array. Considering the importance of this subject, it is crucial to understand the effect of shading on our solar array and how you can mitigate its impact.
What is the Shading Impact on a Solar Panel?
Shading can impact solar panel production in several ways. First, by reducing the amount of sunlight that reaches the solar cells, shading can reduce solar energy production by up to 75% or more in severe cases. This is why it is highly important to assess the amount of shading losses at your property, especially if high trees or any other large nearby object will surround the roof or area where you will install the panels.
Second, another effect of shading is solar cell heating due to an increase in the internal cell resistance. This phenomenon is commonly known as the hot-spot effect. This can reduce the efficiency of the cells, and it can also damage them over time. This issue has been mitigated in the industry by installing 3 bypass diodes (typically found in the junction box behind the solar panel). These bypass diodes interrupt the flow of electricity coming from the shaded string of cells and hence avoid overheating. This however has an undesirable effect, which is that for every by-pass diode that is activated due to shading, 33% of potential energy production will be lost.
Impact of Shading on a String of Solar Panels
As we have discussed before, when a solar panel is shaded, it produces less electricity. This can have a cascading effect on the other panels of the same string. This is because solar panels are connected in series, which means that they need to share the same current. When one panel is shaded, it reduces the current flowing through the entire string. This will cause the other panels in the string to generate less electricity as well.
The amount of shading loss that a solar array can experience depends on several factors, including the size and shape of the shadow, the amount of sunlight that is available, and the type of system configuration that is used.
Maximum Recommended Shading Losses
Shading losses should ideally be zero. However, in real-world case scenarios, this is not always possible. Shading on a solar array is not unusual and typically most residential solar PV projects have some sort of shading on the roof that can equal 5-10% of annual energy losses. There is no technical maximum level of shading that a system can have, however, from a cost-efficient point of view, most systems across the US should not have more than 20% annual energy losses from shading to make financial sense.
Potential Solutions to Mitigate Shading Losses
There are a number of solutions that can be used to mitigate shading losses on photovoltaic arrays.
Some of the most common solutions include:
- Removing the source of nearby shading: Trees, antennas, satellite dishes, chimneys, and roof vents, typically cause shading on solar power projects. Removing the cause of shading is the best way to eliminate the issue. This can be done by cutting down the tree or moving the objects to another place.
- Use Module-Level Power Electronics: Not always is feasible or desirable to remove the source of shading. For those cases, the best approach is to consider installing microinverters or DC power optimizers that mitigate this phenomenon by reducing the impact of shading to the shaded solar panel only.
- Evaluate Different Solar Panel Positions: The way in which solar panels are wired internally presents some opportunities to mitigate shading on some occasions. Solar panels can be installed in portrait or landscape modes, which allows you to set up different layouts that minimize the amount of shading losses according to the operation process of the bypass diodes.
- Consider Half-Cell Solar Panels: Half-cell solar panel technology divides the PV module into two independent sections. This means that if the shade is covering the bottom west section of the panel, it will only affect 1/6 of the solar panel production
We have learned about the impact that shading can have on your solar array. By taking the steps mentioned above to mitigate the impact of shading, you can ensure that your solar panel production is maximized despite shading. This will optimize your PV system production and hence improve your overall off-grid experience.