Environmental Engineering Reference
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PV module's efficiency due to the rise of temperature of PV cells. Natural or forced
circulation of air or other fluids can be used to cool PV cells which heats up the photo-
voltaic thermal systems (PV/T) and can be used as a substitute for the conventional PV
modules. A photovoltaic thermal system (PV/T) integrates heat extraction devices to
the PV cell to reduce the temperature of the PV module and to increase electricity pro-
duction as well as useful heat simultaneously, thereby increasing the overall efficiency
of PV/T system.
For more than thirty years, many researchers have used and discussed the idea of
PV/T both experimentally and numerically. The initial focus was on glazed collectors
utilizing air and liquid as the heat transport media. Later, unglazed heat pump-based
collectors were also introduced. PV/T systems are mainly classified based on the type
of fluid being utilized for heat removal. Compared to PV/T air systems, PV/T water
systems relatively have a higher efficiency, because water has a higher thermal capacity
and conductivity (Prakash, 1994). But considering the leakage and corrosion that can
be caused by water, more robust construction must be included in a PV/T water system
to make it water-tight and corrosion-free. Therefore, the easiest way of heat extraction
from PV modules is by circulating natural or forcing air through an air channel either
on the top or rear-side of the PV surface.
Other than giving rise to diverse ways of heat extraction, the types of PV modules
also influence the operational state of the PV/T system. Crystalline-silicon (c-Si), poly-
crystalline silicon (pc-Si), and recently exploited thin films of amorphous-silicon (a-Si)
cells can be used in PV module construction. The c-Si cells are exorbitantly expensive
due to the comprehensive and energy-intensive procedures needed to produce them,
even though they are highly efficient. In the past two decades, attempts have been
made to lower the price of c-Si cells through various manufacturing methods to further
improve module efficiency.
The PV/T systems have a wide range of applications. One of the feasible ways to
utilize photovoltaic system is to incorporate the PV modules into the building envelope,
as they can be incorporated into the façade and roof of buildings easily. Such building
integrated PV (BIPV) technology is one of the most widespread applications of photo-
voltaic systems in urban buildings. Hence these systems have received a great interest
from engineers and architects. The PV/T systems have a grander prospect by producing
green, safe and tactically significant alternatives to power generation. The superiori-
ties of grid-connected PV electricity to customers are reflected in both economic and
environmental concerns. Customers can partially fulfill their electricity needs while
using utility-generated power at night and on gloomy days by using a grid-connected
PV system where utility power is attainable. The domestic or commercial buildings
can also use the extracted heat for heating purpose.
Most photovoltaic thermal (PV/T) systems are set up in districts or areas where
grid and telephone networks are rarely available, or may be difficult to reach. The PV/T
systems have a relatively long service lifetime with nearly no maintenance. Therefore,
autonomous or stand-alone PV/T systems are more welcome among remote rural areas.
Furthermore, researchers are trying to improve solar output and power production by
using solar trackers and concentrator photovoltaic thermal systems, which are most
feasible when space is scarce. One of the main advantages of a concentrator integrated
PV/T system is to reduce the number of solar cells, as well as increasing power output.
A concentrator collects solar radiation that is received on a relatively large surface
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