Ocean Thermal Energy Conversion (OTEC) is a renewable energy technology that harnesses the temperature difference between warm surface waters and cold deep waters to generate electricity. Note that this is different to Tidal Stream Energy, one of two forms of tidal energy generation that is equivalent to wind turbines under the sea, OTEC utilizes the thermal energy stored in the ocean. So how does it work?
- The process begins by deploying a floating platform or structure in the ocean. The warm surface waters, typically above 20°C (68°F), are used as the heat source, while the cold deep waters, usually below 5°C (41°F), act as the heat sink. OTEC systems employ a working fluid, such as ammonia or a hydrocarbon, with a low boiling point.
- Warm surface water is pumped into a heat exchanger and used to vaporise the working fluid. The heat causes the working fluid to boil, creating high-pressure vapour.
- The high-pressure vapour flows through a turbine, similar to those used in conventional power plants. As the vapour expands, it drives the turbine, producing rotational motion.
- After passing through the turbine, the vapour is cooled by exposure to cold deep water. This rapid cooling causes the vapour to condense back into a liquid state.
- The condensed liquid is then pumped to a higher pressure using a compressor. This pressurised liquid is reintroduced into the evaporation stage, restarting the cycle.
- As the turbine rotates, it drives a generator to produce electricity. The generated electricity can be utilized to power various applications, including homes, industries, or even desalination plants.
OTEC systems offer unique advantages as a renewable energy source. They provide a constant and predictable energy supply, as the temperature difference between the ocean’s surface and deep waters remains relatively stable. Additionally, OTEC systems have the potential to produce large amounts of electricity, given the vast thermal energy reservoirs in the ocean.
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