ABSTRACT:

A performance analysis of an OTEC plant using an integrated hybrid cycle (I -H OTEC Cycle) is conducted. The I-H OTEC cycle has a combination of a closed cycle OTEC plant and a spray flash desalination plant in which a flash evaporator is installed after the OTEC evaporator. The I-H OTEC cycle is an improved version of a joint hybrid cycle(J-H OTEC Cycle) in which the flash evaporator is installed before the OTEC evaporator. The results of a numerical analysis are reported for a 10 MW DTEC plant using the I -H DTEC cycle with plate-type heat exchangers and ammonia as working fluid.

INTRODUCTION

Ocean thermal energy conversion (OTEC) is the system converting heat energy into electricity by using the temperature difference between the warm sea water of the surface and cold sea water of the depth (Uehara et al., 1987). Since the temperature difference in the OTEC plant is 15 " " 23°C available, the thermal efficiency is only 3 " " 5 %. Many countries and small islands in the tropical and subtropical zone where are in need of the electric power as well as drinking water expect to construct the OTEC and desalination" plant. Therefore, a hybrid cycle system of the OTEC and desalination plants will be considered. Multi-stage flash, (MSF) desalination plants are typically used for producing fresh water. However, there are disadvantages in using MSF desalination plants. These are a suppression of the evaporation at a lower part due to the liquid level and a temperature drop caused by the mixture of the cold sea water after evaporation and hot sea water before evaporation. In the plant using the J-H OTEC cycle, as the electric power increases, the desalination rate decreases, conversely, as the desalination rate increases, the electric power decreases.

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