Is Balance of System (BOS) Equally Important for Solar Plant?

The quality, safety and profitability of a solar plant depend not only on the workmanship, efficiency of PV modules and the reliability of the inverter, but also on the Balance of System (BOS) components. However, for many it seems not to have direct or not much impact.

All the components of a Solar Photo Voltaic (SPV) Power Plant, other than SPV modules and inverters, are encompassed into the BOS. It can also be defined as the components and equipment that move DC Energy produced by SPV Panels through the conversion system which in turn produces AC or usable electricity.

This includes wiring, switches, connectors, mounting system, one or many solar inverters (usually considered under main system with Panels), a battery bank and battery charger, earthing/lightning protection. Other optional components include net meter, maximum power point tracker (MPPT), GPS solar tracker, Energy management software, solar concentrators, solar irradiance sensors, anemometer, or task-specific accessories designed to meet specialized requirements for a system owner.

However, based on the size of the plant, its type and purpose, some of the components may not be required or used.

So, it can be understood that the BOS components consist of majority of the items as needed for a Solar PV Plant and the account for 10-40% of the system cost with Installation & Commissioning. The higher BOS cost is needed for standalone systems due to the batteries and charge controllers.  It also decides the future maintenance requirements and thereby expenses would be needed. It is like the army of the SPV system which will protect the plant in the long run, say 20-25 years of the system life. So, a proper selection of the BOS is crucial and any compromise on the quality may lead to more maintenance requirements and cost along with revenue loss.

We need to remember that  a number of users opt for Solar PV system considering that it has a life of  trouble free 20-25 years but do not know this important aspect of BOS and workmanship.

Quality of wiring is not considered to be a critical factor sometime, however neglecting correct wiring and using material that is not suitable for solar applications can compromise the overall life time of a system.

The other key aspects are-

Safety features that protect stand-alone and grid-connected small renewable energy systems from being damaged or harming people during events like lightening events, power surges, or malfunctioning equipment.

Meters & Instrumentation – Meters and other instruments allow to monitor battery voltage, the amount of power is being consumed, and the level at which the batteries are charged. Also, if the system is connected to the electricity grid, the meters keep track of the electricity the system produces and the electricity is used from the grid.

DC Connectors- Improper size and quality may lead to mismatch loss, fire hazard, chances of electrocution, financial loss and system reliability.

So, BOS seems less but can impact more negatively on the SPV system projects considering its predicted long life.

References:

• Best Practices on Performance Evaluation, Operations & Maintenance of Solar PV Power Plants in India Handbook by World Institute of Sustainable Energy
• https://www.cedgreentech.com/article/balance-solar-pv-systems-bos