Environmental Engineering Reference
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(stand-alone, roof integrated, wall integration etc). The figure shows the cross-section
of roof integrated MaReCo designed for Stockholm conditions (Adsten et al., 2005).
The highest optical efficiency which was reported for a bi-facial based MaReCo was
56%. Other examples of optical efficiencies of similar systems are: 91% for dielectric-
filled BIPV covers (Zacharopoulos et al., 2000) and 85% for an air-filled asymmetric
CPC BIPV system (Mallick et al., 2002a).
Some other examples of static concentrators which use dielectrics are presented
by Edmonds et al. (1987). The cells are positioned in a V-trough concentrator filled
with oil or water (the dielectric) which also serves as a cooling function. The design
presented by Shaw and Wenham (2000) uses an anidolic lens to reach a concentration
factor of 2X and optical efficiency of 94%. The flat static concentrator described
in (Uematsu et al., 2001a; 2001b; 2001c; 2003) has been used to analyse various
possible configurations, including use of monofacial cells (1.5X) or bifacial cells (2X)
and different types of illumination of the rear face. However, Uematsu et al. did not
take into account thermal effects in the PV cells.
Two linear dielectric non-imaging concentrating designs (symmetric and asym-
metric) for PV integrated building façades were analysed using 3D ray-tracing analysis
(Zacharopoulos et al., 2000). A “slim line'' design was reported to achieve a concentra-
tion ratio of 4X (Wenham et al., 1995). Thermal analysis indicated that performance
loss through additional heating of the PV cells was more than offset by the gains
achieved through concentration. The efficiency of the module was reported to be
15% greater than that of the flat-plate module. Static concentrators offer a compro-
mise between high concentration systems that require tracking and one-sun flat-plate
modules (Wenham et al., 1995).
Some additional studies in the field of dielectric non-imaging concentrating covers
for PV integrated building facades are those of Zacharopoulos (2001) and Korech
et al. (2007), where the total internal reflection (within the dielectric material) is used
to provide optimal optical efficiency.
An image of the second generation of the Photovoltaic Facades of Reduced Costs
Incorporating Devices with Optically Concentrating Elements (PRIDE) dielectric-filled
system, based on the first studies conducted by (Zacharopoulos et al., 2000) is shown
in Figure 17.2.13. This system was studied and did show excellent power output
compared to a similar non-concentrating system (they were characterized indoors
by using both a flash and continuous solar simulator). Nevertheless, durability and
instability (of the dielectric material) occurred under long-term outdoor characteriza-
tion when the concentrator was made by means of casting technology. With regard to
large-scale manufacturing, durability and reduction of the weight and cost of the con-
centrator, second generation PRIDE designs use 6 mm wide solar cells at the absorber
of dielectric concentrators. PV concentrator modules achieved a power ratio of 2.01
when compared to a similar non-concentrating system. The solar to electrical conver-
sion efficiency for the PV panel was 10.2% when characterized outdoors. It should
be mentioned that in large-scale manufacturing, a module cost reduction of over
40% is potentially achievable by using this concentrator technology (Mallick and
Eames, 2007).
Systems which concentrate radiation using elements opaque to visible light (CPC,
V-trough) cannot be installed on areas of a building through which light is supposed to
enter without reducing natural lighting in the interior. To reach a certain concentration
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