What is the Balance of System in Solar Power Installations?
10th Jul 18
Cameron Quin

Solar panels provide a cost-effective way to convert sunlight, an extremely abundant and free resource, into electricity. However, there is a limitation: the power output of stand-alone solar panels is incompatible with the voltage supplied by the utility network and used by most appliances.

To be used along with conventional electricity sources, photovoltaic panels must be connected to a power-conditioning unit called an inverter, which delivers an alternating current output just like the electric grid. Like any generation system, solar panels also require mechanical supports and electrical protection devices, along with specialised wiring to connect individual solar modules into arrays. All these additional components needed for a functional solar power installation are called the Balance of System (BOS).

Importance of the Balance of System

The photovoltaic array is the largest component of a solar power system, but it cannot deliver useful power by itself, as described above. Using high-quality solar panels from an reliable manufacturer is strongly recommended, but a well-designed balance of system is equally important. You can use the best solar panels in the market, but may end up with poor performance if the BOS is not designed properly, or if it uses low-quality components.

Just like there are opportunities to improve performance by optimising the solar array layout and orientation, the BOS can be adjusted to increase the value of your installation. The following are some examples:

  • You can improve the financial performance of your solar power system with careful selection of the inverter load ratio, also known as the DC/AC ratio.
  • Small solar systems normally have their PV modules connected into a single string circuit, but in larger installations it may be possible to enhance performance by grouping solar panels with similar generation profiles. For example, in a rooftop split into areas with different orientations, solar panels tend to perform better when grouped with other panels having the same orientation.

Mechanical support is accomplished with racking, and the type of racking to use is a very important design decision. Rooftop arrays and ground-mounted arrays use different supports, and the best system for each project varies by client. Ground-mounted arrays tend to have slightly lower installation costs due to ease of working at ground level, and they are easier to service; the main drawback is that they require plenty of land, but may be an attractive option for clients with plenty of space available.

Electrical protections also play a fundamental role, making PV panels a safe source of electricity. Solar power systems are mechanically safe, since they don’t have any moving parts, but they can only be electrically safe with the right protections. When you have many solar modules connected together in a string circuit, their output can add up to several hundred volts.

Innovation Opportunities in the Balance of System

Solar panels themselves have become extremely affordable thanks to innovation and large-scale manufacturing, but there are still many opportunities to reduce the cost of the BOS. For example, an 11-MW solar installation in Queensland uses a modular racking technology that simplifies the installation procedure drastically, while reducing the space requirements. This reduces both the labor and the area required to deploy a specified solar power capacity.

Battery systems are another important area of opportunity for innovation. They are not mandatory in solar power systems, but they are very promising: a solar system equipped with batteries can store electricity and deliver it on demand, even when there is no sunshine.

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Cameron Quin

10th Jul 18
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.