Balance Of System
The balance of system (also known by the acronym BOS) includes all the components of a photovoltaic system with the exception of photovoltaic panels. The balance of system is constituted, typically, by the electrochemical accumulator in the case of some isolated systems of the network, the control unit and the inverter (electronic equipment), the mechanical support structure, the electrical wiring and the protection devices (fuses, ground connections and switches).
Other optional components in a solar BOS include, maximum power point monitoring (MPPT), GPS solar tracker, energy management software, solar concentrators, solar radiation sensors, wind equipment, or specific task attachments designed to meet the specialized needs of a system owner. In addition, CPV systems require optical lenses or mirrors and, sometimes, a cooling system.
In addition, a large photovoltaic solar power station above ground requires equipment and facilities, such as network connections, office and concrete installations. The land is sometimes included as part of the BOS as well.
Balance Of Plant
A term similar to Balance Of System is "Balance Of Plant (BOP)", which is generally used in the context of energy engineering and is applied to all components and support systems of the solar power plant that are needed to produce energy. These may include current transformers, inverters, wiring, appropriate switching and control equipment, protective equipment, power conditioners, support structures, etc., depending on the type of phtovoltaic plant.
Cost of Balance Of System (BOS)
The cost of the system balance will include the cost of hardware (and software, if applicable), labor, which allows for interconnection and inspection (PII) rates, and any other rate that may apply. For large commercial solar systems, the cost of BOS can include the cost of land and construction, etc.
To get an idea of the cost of the balance of the photovoltaic system (solar BOS), the photovoltaic modules represent approximately 25% of the total cost. The cost of batteries is usually higher than that of photovoltaic panels, especially if periodic replacement is included. So, even if the modules were free, we would only reduce the cost of isolated stations by 25%. Fortunately, many applications do not need accumulators (water pumping, irrigation, grid connection) and are free of this economic burden.
Last review: February 13, 2019