Experimental and Numerical Analysis of a PCM-Supported ...

Desalination development focuses on ever larger systems, not the smaller
scale typical of RE-D, which causes a lack of standard (i.e. cheap)
components appropriate for small scale desalination plants.
Lake of supporting policies to promote the penetration of RE-D in the market,
which make it cheaper.
1.4 Solar desalination
Solar distillation can be classified into two main categories based on the plant setup.
The first is the basin-type (or direct type) solar stills in which the solar collector is
integrated in the still, such that solar irradiation is directly used to evaporate water.
In the second class, which is called indirect type solar still, the solar collecting device
is separated from the evaporator. As an indirect type solar distiller, humidificationdehumidification
(HDH) technique using fixed packed beds was introduced as a
promising technique as early as 1950's. As reported by Hudges [1], a solar operated
HDH process can yield 5 times as much fresh water as a solar still of the same solar
collecting area can produce.
1.4.1 Conventional solar stills
Solar stills are a simple method for desalinating water as they mimic the hydrological
cycle in the nature. Solar stills utilize the fact that water left exposed to air will tend to
evaporate. The function of the still is to capture this evaporating water and condense
it on a cold surface, thus providing potable water. The solar still consists of a black
colored pan (to maximize the absorbed energy) containing water, this pan is then
covered with a glass sheet or translucent plastic, which allows the admission of solar
energy. This cover also acts as a condensing surface for the evaporated water. The
cover is tilted towards the fresh water collector (Figure 1.5).
Conventional basin-type solar stills have low efficiency as there is no real
possibility to recover the latent heat of condensation, which is wasted to the
environment. This type obviously suffers from low productivity and requires large
land areas. The low daily productivity along with the high cost of water produced by
this method are the main obstacles to utilize the huge solar energy resource in water
distillation. The problem of low daily productivity of solar stills triggered scientists to
investigate various means of improving still productivity and thermal efficiency for
minimum water production cost. These means include various passive and active
methods for single effect stills.
Different techniques, configurations, and developments that have been introduced in
literature to improve the single effect stills are enormous and were highlighted in
Fath [77] and Tiwari, and Yadav [79]. Solar distillation is usually suitable for smallscale
applications in remote areas, where abundant solar radiation and low cost land
are available. Fath [77] concluded that the development of solar distillation has
demonstrated its suitability for saline water desalination when the weather conditions
9