Silicon-based solar cells Characteristics and production processes ...

Silicon-based solar cells – characteristics and production processes
5. Photovoltaic systems
Photovoltaic systems are electric systems which make it possible to practically
utilize the energy of solar radiation. The power of these systems can be within the
range from a few W p to a few hundred MW p , which determines their structure and
configuration. The simplest autonomous photovoltaic system consists of
a photovoltaic module, a voltage controller and an energy receiver. Due to their little
usefulness, resulting, among others, from their effective work only when illuminated,
the practically applied autonomous PV systems consist of PV modules, a charging
controller, an accumulator and an energy receiver. The charging controller is used in
small autonomous systems with the power up to a few kW p and its purpose is to
supervise the charging process of the accumulator, in order to switch off the charge
above 13,7 V and to switch off the accumulator’s loading below 11,1 V. The current
obtained from the PV module is a direct current (DC) and thus, in the case of the use
of an electric energy receiver, which requires an alternating current (AC) supply, it is
necessary to apply an inverter in the PV system.
Fig. 40. Scheme of an autonomous PV system type DC (a) and type AC (b).
The most important categorization of photovoltaic systems classifies them as the
autonomous systems and the integrated systems with an energy network. In the case
of the autonomous systems, their power can vary from a few W p to a few kW p , and as
for the integration with the energy network, this case is appropriate for the systems
with the power above 3 kW p . Within the frames of this division, we can distinguish
the systems constantly oriented and the follow-up systems, in which the module
plane is set mechanically, parallelly to the direct radiation. In the case of the systems
integrated with the network, they can be scattered or central, that is, they are big PV
electric power stations, the largest of which, with the power of 97 MW, is currently
located in the town of Sarnia, Canada. [74]. Typical PV power plants possess the
power within the range of 1 ÷ 80 MW p . Another categorization distinguishes the PV
systems as the free-standing ones and those integrated with buildings (BIPV),
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