Salinity gradient solar ponds - Solar Energy Sciences and Engineering Applications - page 197

Figure 7.1.3 Typical salinity and density profiles in a solar pond.
Figure 7.1.3 shows the typical solar pond profiles of salinity, density and tempera-
ture. The UCZ is typically 0.2 m-0.3 m thick and is maintained at temperature close to
local daily ambient. The UCZ requires continuous washing with fresh or low salinity
water to remove the diffused salt from the saline layers below and to compensate for
the evaporation water loss. In order to maintain the salinity gradient, salt crystals or
saturated brine must be added to the LCZ to compensate for the salt lost by diffusion
(Akbarzadeh et al., 2005).
7.2 SOLAR POND - DESIGN PHILOSOPHY
7.2.1 Sustainable use of resources
Solar ponds are very sensitive to different applications and hence knowing the appli-
cation before design starts is very crucial. Knowing the end application of the solar
pond would help estimate the energy requirements and hence an optimised solar pond
could be designed. For example, the characteristics of a solar pond to supply hot water
at say 35 ◦ C to an aquaculture facility will be very different from that of a solar pond
to be used to generate electricity where sustained performance at higher temperatures
of 80 ◦ C or above is essential. Obviously the solar pond must be located as close to its
application as possible (Akbarzadeh et al., 2005).
Solar ponds would be more economical if constructed using local labour, materials
and other resources. It is essential to have a local supply of salt or brine and low salinity
water. Flat land is better with high solar radiation for easy construction and optimum
operation of a solar pond. Since construction of the solar pond basically involves earth
moving and plumbing, it makes good sense to use local contractors.