Cogeneration for power and desalination – state of the art review

This paper reviews the state of the art of cogeneration for power and distillation. The performance of several cogeneration options are considered in association with the MSF process for seawater desalination. Both full load and part load characteristics of each major commercial cogeneration process is reviewed both from a technical and economic viewpoint. A methodology for selecting the optimum cogeneration option to satisfy a given demand of power and water is described and an example is given for a cogeneration plant having a power rating of 300 MW and 50 MIGD of potable water. The life cycle cost analysis is used to select the optimum cogeneration system and the exergy analysis method is used for allocating the costs between electricity and water.

• The wide variety of options available for combining cogeneration plants with desalination plants and the influence of the technical and economic performance parameters of each combination makes the use of system modeling using computer programming inevitable. • The optimum cogeneration option depends strongly on the load variation throughout the year. Both monthly electrical and water production loads should be input parameters to the computer model. • The power to water ratio of the different combinations of cogeneration plants scans the range from 4 to 18 MW per MIGD with the lowest ratio for the BP-ST option and the highest ratio for the CC-EC option. • The power to water ratio has a strong influence on the optimum selection of a cogeneration plant. • The selection of the most economical cogeneration plant should be based on a life cycle cost analysis which should take into consideration the escalation rates of fuel and O&M expenses in order to arrive at an estimate of the total expenses for each option for the whole lifetime of its operation.