The balance of system (BOS) encompasses all components of a
photovoltaic system
A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and ...
other than the
photovoltaic panels
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
.
This includes
wiring
Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure.
Wiring is subject to safety standards for design and installation. Allowable ...
, switches, a
mounting system, one or many
solar inverter
A solar inverter or photovoltaic (PV) inverter is a type of power inverter which converts the variable direct current (DC) output of a photovoltaic solar panel into a utility frequency alternating current (AC) that can be fed into a commercial ...
s, a
battery bank and
battery charger
A battery charger, recharger, or simply charger is a device that stores energy in a battery by running an electric current through it. The charging protocol (how much voltage or current for how long, and what to do when charging is complete) depe ...
.
Other optional components include
renewable energy credit revenue-grade meter,
maximum power point tracker (MPPT),
GPS solar tracker
A solar tracker is a device that orients a payload toward the Sun. Payloads are usually solar panels, parabolic troughs, fresnel reflectors, lenses or the mirrors of a heliostat.
For flat-panel photovoltaic systems, trackers are used to ...
,
Energy management software
Energy Management Software (EMS) is a general term and category referring to a variety of energy-related software applications which may provide utility bill tracking, real-time metering, building HVAC and lighting control systems, building simulat ...
,
solar concentrator
Concentrated solar power (CSP, also known as concentrating solar power, concentrated solar thermal) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight into a receiver. Electricity is generated when ...
s,
solar irradiance
Solar irradiance is the power per unit area ( surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre ...
sensors,
anemometer
In meteorology, an anemometer () is a device that measures wind speed and direction. It is a common instrument used in weather stations. The earliest known description of an anemometer was by Italian architect and author Leon Battista Alberti ...
, or task-specific accessories designed to meet specialized requirements for a system owner. In addition,
concentrated photovoltaics
Concentrator photovoltaics (CPV) (also known as concentration photovoltaics) is a photovoltaic technology that generates electricity from sunlight. Unlike conventional photovoltaic systems, it uses lenses or curved mirrors to focus sunlight ont ...
systems require
optical lens
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...
es or mirrors and sometimes a cooling system.
In addition, ground-mounted, large
photovoltaic power station
A photovoltaic power station, also known as a solar park, solar farm, or solar power plant, is a large-scale grid-connected photovoltaic power system (PV system) designed for the supply of merchant power. They are different from most building ...
require equipment and facilities, such as grid connections, office facilities, and concrete. Land is sometimes included as part of the BOS as well.
Balance of Plant
A similar term to Balance of System is “Balance of plant (BOP)” which is generally used in the context of power engineering and applies to all the supporting components and systems of the power plant which are needed to produce the energy. These may include suitable transformers, inverters, cabling, switching and control equipment, protection equipment, power conditioners, support structures, etc., depending on the type of plant.
Cost of BOS
Cost of Balance of System will include the cost of the hardware (and software, if applicable), labor, permitting Interconnection and Inspection (PII) fees, and any other fees that may apply. For large commercial solar systems, the cost of BOS may include the cost of land and building, etc. The cost of BOS can be about two thirds of the total cost.
Downward Trend
While the cost of solar panels is coming down appreciably, the cost of BOS is not showing the same rate of decline. It is understandable because extra effort has gone into the solar cell technology. The solar cell technology is still evolving and improving, and costs are being reduced fast. The balance of systems consists mostly of items which are not specific to solar technology. As an example, the mounting structures are quite usual and the technology may already be mature, benefitting little from further innovation and research.
See also
*
Balance of plant Balance of plant (BOP) is a term generally used in the context of power engineering to refer to all the supporting components and auxiliary systems of a power plant needed to deliver the energy, other than the generating unit itself. These may inclu ...
References
Solar energy
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