Civil Engineering Reference
In-Depth Information
an off-grid dwelling. The hybrid collector is equipped with fins to enhance the heat
transfer between the PV cells and air; the air was then drawn into the house using a
fan in winter and by natural convection in summer. Fudholi et al. (
2010
) indicated
that drying up agricultural and marine products is one of the most attractive and
cost-effective applications for solar PV/T technology. Takashima et al. (
1994
)
concluded that the surface temperature of the PV panels could be reduced when air
gap was remained above the PV to form a thermal collector. Moshtegh and
Sandbergy (
1996a
,
b
) numerically and experimentally studied the performance of
air flow induced by buoyancy and heat transfer within a vertical channel heated
from the PV side wall. The study reported that the induced velocity increases the
heat flux non-uniformly inside the duct and its impact depends on the sizes and
geometry of the air exit. Bhargvaa et al. (
1991
) and Parkash (
1994
) studied the
performance of single-pass PV/T air collector using a computer model and ana-
lysed the influence of air mass flow rate, depth of air channel and packing factor to
the system's overall efficiency. Sopian et al. (
1996
) analysed the performance of
both single- and double-pass PV/T air collectors using steady-state computer
models. The results showed that double-pass PV/T air collectors have higher
efficiencies than the single-pass ones, but its capital cost is a bit higher. Kelly and
Strachan (
2000
) and Tripanagnostopoulos et al. (
2002
) suggested several possible
approaches to enhance the cooling effect, such as modifying channel geometries to
create more turbulence for flows. Tiwari and Sodha (
2007
) indicated that the
glazed air PV/T collectors have higher thermal efficiency than the paralleled
unglazed ones, especially at low-temperature conditions where the double-glazing
cover was found to be superior to the single-glazing cover (Garg and Ahhikari
1997
). On the other hand, the glazing cover would slightly reduce the overall
performance of the collector owing to unavoidable solar reflection occurring on the
cover.
For water-based PV/T, Agarwal and Grag (
1994
,
1995
) designed the prototypes
of thermosyphonic and flat-plate PV/T water heaters. Bergene and Lovvik (
1995
)
then conducted an energy transfer study on PV/T water system composed of flat-
plate solar collector and PV cells, which indicated that an overall efficiency of
60-80 % can be achieved. It is found that the proposed system could be used to
preheat the domestic hot water. More recently, Zondag et al. (
2003
) classified the
water-based PV/T collectors into four major types, namely sheet-and-tube col-
lectors, channel collectors, free-flow collectors and two-absorber collectors. Chow
et al. (
2006
) suggested that implementing the water flow channels beneath the
transparent PV module may be a good choice to achieve enhanced solar efficiency.
However, the single-glazing sheet-and-tube hybrid PV/T collector is regarded as
the most promising design as it has high overall efficiency and is easy to construct.
Kalogirou and Tripanagnostopoulos (
2001
,
2006
) simulated a PV/T water supply
and storage system and found that the economic viability of PV/T water system
was much better than the air-based type. Elswijk et al. (
2004
) installed large PV/T
arrays on residential buildings and reported that the use of PV/T would save
around 38 % in roof area, relative to a side-by-side system of PV and solar
thermal. Ji et al. (
2003
) studied a facade-integrated PV/T collector for residential
