Use the temperature difference between the surface and deep water of tropical and subtropical oceans to produce electricity.
Thermal cycle
Ocean temperature difference electricity generation uses the Rankine cycle and its actual thermal efficiency is about 2.5%. Depending on the working fluid used and the arrangement of the process, it is divided into closed, open and mixed cycles. Rankine cycle ocean temperature difference power generation can also use other thermal cycles, such as the fog droplet (or foam) lifting cycle or the full flow cycle. The thermoelectric effect can also be used to produce electricity.
Closed cycle (intermediate method)
Use low boiling point substances, such as ammonia, freon, etc. as working fluids to complete the closed-loop Rankine cycle. Its characteristicsThe risks are that the system is under positive pressure, the vapor density of the working fluid is high, the volume flow rate is low, and the size of the flow part is not too large. However, the evaporator and condenser must use surface heat exchangers, which are huge in size, consume a lot of metal, and are difficult to maintain.
Open cycle (flash method or expansion method)
By using water as the working fluid, condensed water does not return to the cycle. Its flash evaporator and condenser can use hybrid heat exchangers, which have simple structure and easy maintenance. If a surface condenser is used, fresh water can be produced as a byproduct. However, the saturation pressure of low temperature water vapor is extremely low, the specific volume is huge, and the size of the flow part is too large.
Mixed cycle
Essentially the same as the closed cycle, but uses low-pressure steam extracted from warm seawater to heat the low-boiling working fluid.