Optimization in dual purpose plants

The world trend is to save energy and its best use. One of the ways is the dual purpose plant in sea water desalination area, with simultaneous production of desalinated water and electrical power. The combinated production improves the effcieicny of the rhmic cycle and the utilization of fuel is better than separately production.The characteristics of plant such as water/power ratio and the economy ratio will be determined for the dual plants so that the design values must be the optimum point out of all possible values.The optimum relationship water/power and economy will be determinated as a function of the yearly bank rate, the amortization period in years, the fuel cost, the utilization factor, etc. Definitively, the optimum point is a function of the investment cost and the operating cost.The influence on the optimum point of above factors with two possibilities is analyzed : condensation turbine and back pressure turbine.The influence of the fuel cost and labour cost excalation on an installated dual plant and designed at the optimum point is too analyzed.