Preliminary design and cost analysis of a solar distillation system

In this paper different solar systems of seawater distillation are proposed and economically analyzed. The solar collectors are parabolic trough ones in which brine circulates as thermal fluid. Steam is directly obtained from circulating brine. The solar collector field could be connected to condenser/preheater heat exchangers; nevertheless, the system would have a low performance ratio. In addition, the solar collectors could be coupled to multi-stage flash or multi-effect distillation systems to continue the evaporation of the remaining brine. The steam generated by the solar field would drive the distillation plant. The above systems are analyzed in comparison with other solar distillation ones as follows: a multi-effect distillation plant connected to a solar field in which steam is directly generated from fresh water, and a multi-stage flash plant that uses parabolic trough collectors as the brine heater. The specific cost of the product is evaluated for different climatic conditions, plant capacities, cost of the solar collectors, and costs of a conventional energy supply. Results obtained are useful in preliminary cost evaluation of the proposed solar distillation systems.

Since direct steam generation parabolic troughs are not currently commercial, estimating the fresh water cost by using such technology is difficult. Nevertheless, the case studied here offers useful results in preliminary cost evaluation as well as in sensitivity analysis of the solar-assisted distillation systems considered. Moreover, the economic benefits of solar direct steam generation from brine instead of from fresh water in desalination processes are pointed out.