Ocean Thermal

Besides the power generation, fresh water, seawater in the deep sea, air conditioning can be obtained from the ocean temperature differential energy device that can be combined with the mine system in the deep sea. Therefore, the ocean temperature differential energy device can be utilized to set up marine independent living space, and support system for the marine power plant, seawater freshening plant or marine mining plant, marine city or marine livestock farm. In a word, priority should be taken to the comprehensive utilization in the development of temperature differential energy.

The ocean temperature difference conversion has opening circulation and closed circulation type.

a)        Open Circulation Power Generating System

The open circulation system comprises of vacuum pump, warm water pump, cool water pump, flash vessel, and condenser and turbine generator sets. The vacuum pump will take out the vacuum to a certain degree within the system. And then the warm pump will be initiated to take out the warm water in the surface into the flash vessel. Since there is a certain vacuum within the system, the warm seawater will be boiled and vaporized in the flash vessel until turning into the steam. The steam will be blown off from the orifice through the pipeline to propel the operation of turbine to power the generator for electricity. The low-pressure steam discharged from the turbine will flow into the condenser, which will be cooled by the cool seawater pump from the deep sea to be re-condensed to water for sea outfall.

In this system, as the working medium, the seawater will be pumped to the flash vessel for vaporization, and to propel the operation of turbine, and finally will be discharged into sea after being condensed by the condenser. Therefore, such working system method is called open circulation system. In this system, the pressure loss between flash vessel and condenser is very lower because of the water being taken as the working fluid body and medium. So, it is to be particularly noted the pressure loss in the pipelines and the large size of the turbine. The byproducts from the open circulation system are fresh water discharged from the condenser, which is the advantage of the system.

b)        Closed Circulation Power Generation System

Instead of seawater, the closed circulation power generation system adopts matters with low boiling point, i.e. propone, Freon and ammonia as the working medium, which will be reversible for vaporizing, expansion and condensing in the closed circuit. As a consequence of utilization of the working medium with low boiling point, the working pressure of the steam will be increase.

The closed circulation differs at the system modules and working method with the open circulation. Evaporator replaces the flash vessel in the open circulation. When the warm water pump takes out seawater in the surface to the evaporator, seawater will pass part of the thermal to the working fluid with low boiling point, for example, the ammonia water through the coil pipe in the condenser, other than to be vaporized by seawater itself

When the temperature of the warm water is decreasing, the ammonia water is increasing with its temperature and starts boiling until being turned to the ammonia gas. The ammonia gas will be expanded to do work through the vane channel of the turbine, to propel the rotating of the turbine. The ammonia gas discharged from the turbine flows into the condenser, where the ammonia gas will be cooled by seawater pumped from the deep sea by the cool water pump, and turns into liquid state ammonia again. The liquid state ammonia in the condenser will be compressed into the evaporator again by the ammonia pump (working medium pump) for the purpose of circulation utilization.

Since the closed circulation system adopts the working medium with the low boiling point, the plants can be diminished in a large degree especially the dimension of turbine sets. But it will be polluted to the environment by utilization of the working medium with low boiling point

The most difficulty for the utilization of temperature differential energy exists on the small difference in temperature and lower power density. The backbone of its conversion lies on reinforcing the thermal and mass transmission technology. Furthermore, the comprehensive utilization of the temperature differential energy has been system engineering interrelated to other academic sciences.