Performance evaluation of CHCP hybrid seawater desalination plants

There are many ways to improve efficiency and reduce fresh water cost in desalination plants, like theintegration of two or more desalination systems into a hybrid mechanical/thermal lay-out. Most common resultsthat could be achieved by hybrid systems are savings in pretreatments, overall cost reduction and significantprimary energy savings, especially when cogeneration unit are concerned. In this paper a small size(2000 m3/day) thermal desalination system (MEE) is coupled with a single-stage seawater reverse osmosis(SWRO) system; the system is fed by a natural gas (NG) reciprocate engine, where heat is recovered bothfrom exhaust gases and from the cooling jacket water circuit. Technical and energetic aspects of the examinedhybrid lay-out are described in detail, and complemented with a brief cost analysis in order to assess theeconomic viability of the proposed solution. In the examined case, cogeneration coupled with hybriddesalination systems reveals economically convenient with respect to the production of the same freshwater flow rate by very efficient RO systems. The minimization of the unit cost of desalted water was thegoal of the performed optimization; the sensitivity of fresh water unit cost to variations in the flow rate ofpermeate exiting the RO section is also investigated to determine the optimal design