Application of direct steam generation into a solar parabolic trough collector to multieffect distillation

In this paper, the application of the direct steam generation into a solar parabolic trough collector to multieffect distillation is proposed and economically evaluated. The thermal fluid of the solar field is pure water, which boils as circulating along the solar collectors. The steam generated drives a multieffect distillation unit. This solar distillation system is compared with multieffect plants connected to a conventional parabolic trough collector field, and with fossil fuel powered distillation plants. Different parameters are analysed, the plant capacity and performance ratio, the cost of conventional thermal energy, the cost of the solar collectors, and the annual average of the fresh water obtained per m2 of solar collector. Results obtained are useful in finding the most suitable conditions in which solar energy could compete with conventional energies in solar desalination.

Results obtained in Fig. 3 and Table 1 are useful in extrapolating values of fresh water levelised cost from given conditions to different ones. In addition, from Fig. 4 and Table 2 we can point out the competitiveness of solar MED technology vs. conventional MED in southern Spain, depending on conventional energy costs and costs of solar collectors. Obviously, the most suitable conditions for solar MED systems strongly depend on the costs of fossil fuels and solar collectors. Fig. 5 may help us to choose a suitable performance ratio for a given plant capacity.