Civil Engineering Reference
In-Depth Information
technical status, difficulties and problems remaining, market potential and barriers
in practical application, still remain unclear. To clear up these matters, an intro-
duction into the current achievements on PV/T technology is most desired. The
work will have significant global impacts in terms of several important aspects,
namely (1) helping engineers/professionals to understand the basic knowledge of
PV/T, identify the technical feature of the PV/T systems and select, design, install
and evaluate PV/T system; (2) helping academia/researchers to identify research
directions/topics of PV/T technology; (3) helping policy makers and governmental
officers to deliver the strategic plans related to PV/T and establish the associated
standards and regulations; and (4) helping industry to identify the barriers of PV/T
in piratical application, develop the commercially variable PV/T products and
establish the associated market exploitation plan to promote wide application of
PV/T technology across the world.
2 Basic Concept and Theory, Classification
and Performance Evaluation Standards
of the PV/T Technology
2.1 Basic Concept and Theory Behind the PV/T Operation
PV cells/modules are well-known solar electricity-generating components, and the
solar efficiency of the PVs is a parameter associated with the cells' materials and
temperature. In general, the PVs' electrical efficiency is in the range 6-18 %,
which is a value measured at the nominal operating cell temperature (NOCT)
(0.8 kW/m
2
of solar radiation, 20 C of ambient temperature and 1 m/s of wind
speed) (Messenger and Ventre
2003
). It is well known that the solar electrical
efficiency of the PV cells falls with the rise in its operating temperature, as shown
in Fig.
1
. Increasing the temperature of PV cells by 1 K leads to about 0.4-0.5 %
reduction in the electrical efficiency for the crystalline silicon-based cells
(Brinkworth et al.
1997
; Kranter et al.
1999
) and around 0.25 % for the amor-
phous silicon (a-Si) cells (Kalogirou and Tripanagnostopoulos
2006
).
Fig. 1 Established
efficiency-to-temperature
relationship (Zhang
et al.
2012
)
