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Although the solar panels are the heart of a PV system, many other components are
required for a working system, as we discussed very briefly above. Together, these
components are called the balance of system (BOS). Which components are required
depends on whether the system is connected to the electricity grid or whether it is
designed as a stand-alone system. The most important components belonging to the BOS
are:
A mounting structure in order to fix the modules and direct them towards the
Sun.
Energy storage as a vital part of stand-alone systems, because it assures that the
system can deliver electricity during the night and in periods of bad weather.
Usually, batteries are used as energy storage units.
DC-DC converters in order to convert the module output, which will have a
variable voltage depending on the time of the day and weather conditions, to a
compatible output voltage that can be used as input for an inverter in a gridconnected system.
Inverters that are used in grid-connected systems to convert the DC electricity
originating from the PV modules into AC electricity that can be fed into the
electricity grid. Many inverters have a DC-DC converter included to convert the
variable voltage of the PV array to a constant voltage that is the input for the
actual DC-AC converter. Also stand-alone systems may have an inverter that is
connected to the batteries. The design of such an inverter differs considerably
from that for a grid-connected system.
Charge controllers that are used in stand-alone systems to control charging and
often also discharging of the battery. They prevent the batteries from being
overcharged and also from being discharged via the PV array during night. High
end charge controllers also contain DC-DC converters together with a maximum
power point tracker in order to make the PV voltage and current independent
from the battery voltage and current.
Cables that are used to connect the different components of the PV system with
each other and to the electrical load. It is important to choose cables of sufficient
thickness in order to minimize resistive losses.
Though not part of the PV system itself, the electric load, i.e. all the connected
electric appliances, has to be taken into account during the planning phase. Further, it has
to be considered whether the loads are AC or DC.
The different components of a PV system are schematically presented in Figure 17.6
•
•
•
•
•
Although the solar panels are the heart of a PV system, many other components are
required for a working system, as we discussed very briefly above. Together, these
components are called the balance of system (BOS). Which components are required
depends on whether the system is connected to the electricity grid or whether it is
designed as a stand-alone system. The most important components belonging to the BOS
are:
A mounting structure in order to fix the modules and direct them towards the
Sun.
Energy storage as a vital part of stand-alone systems, because it assures that the
system can deliver electricity during the night and in periods of bad weather.
Usually, batteries are used as energy storage units.
DC-DC converters in order to convert the module output, which will have a
variable voltage depending on the time of the day and weather conditions, to a
compatible output voltage that can be used as input for an inverter in a gridconnected system.
Inverters that are used in grid-connected systems to convert the DC electricity
originating from the PV modules into AC electricity that can be fed into the
electricity grid. Many inverters have a DC-DC converter included to convert the
variable voltage of the PV array to a constant voltage that is the input for the
actual DC-AC converter. Also stand-alone systems may have an inverter that is
connected to the batteries. The design of such an inverter differs considerably
from that for a grid-connected system.
Charge controllers that are used in stand-alone systems to control charging and
often also discharging of the battery. They prevent the batteries from being
overcharged and also from being discharged via the PV array during night. High
end charge controllers also contain DC-DC converters together with a maximum
power point tracker in order to make the PV voltage and current independent
from the battery voltage and current.
Cables that are used to connect the different components of the PV system with
each other and to the electrical load. It is important to choose cables of sufficient
thickness in order to minimize resistive losses.
Though not part of the PV system itself, the electric load, i.e. all the connected
electric appliances, has to be taken into account during the planning phase. Further, it has
to be considered whether the loads are AC or DC.
The different components of a PV system are schematically presented in Figure 17.6