Environmental Engineering Reference
In-Depth Information
Figure 7.2.1
Solubility of NaCl and MgCl
2
in water at different temperatures.
One of the most important criteria in determining the viability of a solar pond is
the availability of fresh or low-salinity water (less than 50,000 ppm salt concentration
or a density of less than 1050 kg/m
3
). The amount of low-salinity water required to
establish a pond is about the volume of the water in the pond measured from the
surface to the middle of the gradient layer. The amount of water needed to maintain
the gradient depends on evaporative losses, and the flow rate of the overflow system
removing surface washing water containing the salt that has diffused upwards. As a
rule of thumb, a surface washing water flow rate of two to three times the yearly
average rate of evaporation is required. The rate of adding water to the surface zone
must exceed the rate of removal through the overflow by the rate of evaporation
(Akbarzadeh et al., 2005).
For large ponds (greater than about 1000 m
2
), it is best to construct the pond by
establishing the walls using the soil excavated from the inner periphery of the pond. The
bottom of the pond will thus be below the surrounding ground level. This arrangement
provides the head required for gravity feeding of the surface water from the solar pond
to adjacent evaporation ponds, as well as siphoning off brine samples from different
depths in the pond for the required analysis.
7.2.5 Transient performance prediction
To predict the thermal performance of large solar ponds, the thermal process in these
solar ponds can be treated as one-dimensional unsteady conduction loss with heat
generation from incoming solar radiation and heat addition from any other source of
thermal energy; here the finite difference method is used. As shown in Figure 7.2.2 the
NCZ of the solar pond is divided into a number of small divisions (divisions can be
non-equal) and the location of the node for determination of temperature is assumed
Search WWH ::
Custom Search