Environmental Engineering Reference
In-Depth Information
area and converts it to a concentrated radiation onto a small area with solar cells.
The concentrators can be made from simple plastic lenses or conventional mirrors, or
polished light water surfaces. Fins are added to the back of the PV panel to further
improve the performance of air PV/T systems.
Numerous research has been attempted to advance the performance of pho-
tovoltaic thermal systems. Generally speaking, the conversion rate of PV modules
available in the commercial market is very low. They can only convert about 6-18%
of solar radiation incident on the PV panel to electricity. The rest of the solar energy is
turned into waste heat affecting the cell competence and some is reflected back to the
atmosphere.
A PV/T system has the following advantages:
(i)
Dual function: the integrated system can generate both electricity and heat;
(ii)
Flexible and efficient: with limited roof surface area, the integrated system has
a higher efficiency than two independent systems, especially using the BIPV
technology;
(iii)
Wide application: the heat generated can not only be used for heating but also
for cooling, for instance it can be used for desiccant evaporative cooling;
(iv)
Economical and practical: the PV/T system is simple to be retrofitted or inte-
grated into different types of buildings with insignificant remolding. A PV/T
system can be used as roofing material and has a shorter payback period.
Compared to parallel connecting of photovoltaic panels to solar thermal collectors,
the integrated PV/T modules are not only able to produce more energy per unit surface
area, but also have less initial and production cost. The collector area can be reduced
up to 40% by using PV/T system producing the same amount of energy according to
an ECN report (Energy research Centre of the Netherlands) (IEA, 2007). Furthermore,
PV/T modules cater to the same aesthetic need as PV.
This chapter will focus on different technologies and module aspects of heat trans-
formation of the PV/T systems. Modifications are suggested with the main objective
being to improve heat transfer in the PV/T systems. A detailed description on hybrid
PV/T solar systems is included in a recently published Roadmap (Zondag et al., 2005;
Affolter et al., 2006), where several aspects regarding technology, present status and
future perspectives of these solar energy conversion systems are presented (Arif Hasan
and Sumathy, 2010).
5.2 PV/T DEVICES
PV/T devices can vary in design to suit various applications, ranging from PV/T domes-
tic hot water systems to ventilated PV facades and actively cooled PV concentrators.
The markets for both solar thermal and PV are growing rapidly and have reached a
very substantial size. For PV/T, a similar growth can be expected, since the technical
feasibility is proven and as such it can be integrated with other domestic applications.
PV/T has broad range of applications, that is, it is not only suitable for domestic hot
water heating (glazed PV/T collectors), but also for commercial buildings (ventilated
PV to preheat ventilation air during winter and to provide the driving force for natural
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