How Does Shading Affect Solar Panels?
12th Oct 17
Cameron Quin

Solar power systems are not productive when they are not getting sunlight, which means they should be kept free from shadows. However, this is not always possible, especially when there are trees, buildings or hills around the project site. Fortunately, there are ways to deploy solar power successfully even when a rooftop is partially shaded.

Keep in mind that solar modules are normally connected in series, where each circuit of modules is called a string. Conventional solar inverters do not convert the output of individual modules to AC power, but rather the output of each entire string. This connection reduces wiring costs but has one weakness: if one of the panels is shaded, it restricts current and reduces the output of the entire string. You can imagine each solar panel as having a “valve” thats starts to close when it is shaded, affecting all panels in the same circuit.

Reducing the Effect of Shadows with Smart Design

Shading issues can be prevented in great part by surveying the site before installing the solar panels. If you are working with professionals, they will analyse the positions of shadows and how they change during the day before proceeding with the project. Unless your rooftop area is very limited, there is generally space to maneuver around shadows when installing a PV system.

Providers of solar PV systems use simulation software to ensure that shading will not be an issue at any point of the year. Consider that the sun goes lower in the sky during the winter, which can make some shadows longer than in the summer. However, solar PV system design software accounts for this.

Compensating Shading with Module-Level Electronics

Some shadows can be very difficult to avoid. However, there are projects where the business case for commercial solar power is so good, that it makes sense to use as much rooftop area as possible. For example, large energy users can eliminate capacity charges from their power bills by reducing their net yearly energy consumption. With a technology called module-level electronics, you can make solar panels independent from each other even if they are part of the same array.

Microinverters completely modify the electrical connection used in solar power systems. While a conventional installation has modules connected in series direct-current circuits, microinverters convert power to alternating current individually at each module, and are connected in a parallel circuit. Basically this converts each solar module into a separate generation system, and shading only reduces output for the affected panel, not the whole system.

Power optimisers use a hybrid system configuration that takes elements from conventional inverters and microinverters. The solar array is connected in DC circuits, but each module is equipped with a power regulator that optimises voltage and current so that other modules in the circuit are not affected when one of them is shaded.

The main limitation of module-level electronics is that installation cost increases, but there is also also a corresponding increase in energy output by minimising the effect of shading. In countries like Australia, where electricity prices are very high, solar power is an excellent investment even with additional system features.

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Cameron Quin

12th Oct 17
Cameron Quin

Cameron Quin has been heavily involved in business development from an early age. After founding and selling two online companies, Cameron found a strong passion for renewables and the opportunities it brings for the commercial and industrial sector. Sharing the possibilities of solar and the knowledge from the Solar Bay team is his favourite pastime.