POTENTIAL USES OF SOLAR-ENERGY FOR SEAWATER DESALINATION

A method to assess the cost effectiveness of large solar desalination systems is presented. This method was used to investigate the effect o f site, technological and economical parameters. The comparative cost of full and partial solar desalting systems was also evaluated by a mo re detailed case study of 20,000 m(3)/d and 200,000 m(3)/d systems. Tw o solar technologies were considered: salt gradient solar ponds and du al-purpose solar electric power stations supplying low pressure steam to thermal desalting systems. The solar field could use any concentrat ing collector technology such as parabolic troughs, dishes or helelios tats. At the present state of heat storage technology, back-up of exte rnal fuel will have to be used for continuous operation. Two desalting technologies were considered: multi-effect distillation(MED) and hybr id MED/SWRO systems. The first uses thermal process heat from the sola r field and a relatively small supply of commercial electricity for pu mping purposes. The second uses solar energy only for the MED portion of the hybrid system while the SWRO portion uses commercial electricit y. The hybrid concept represents therefore a partial rather than a ful l solar system. Solar pond powered desalting systems were found to hav e a considerable potential to be cost effective if favorable site cond itions exist. Only for very low specific solar field cost and/or high commercial electricity prices would the fully solar options be more co st competitive than the partial solar options.