Ocean Thermal Energy Conversion Systems

In this presentation I'm explaining about Closed and Open cycle OTEC systems with detailed explanation and advantages and disadvantages of OTEC systems.

1. OCEAN THERMAL ENERGY CONVERSION BY S.VEDANARAYANA MECHANICAL ENGINEERING

2. INTRODUCTION Ocean Thermal Energy Conversion (OTEC) is an energy technology that converts solar radiation into electric power. OTEC systems use the ocean’s natural thermal gradient , consequently the temperature difference between the warm surface water and the cold deep water below 600 meters by about 20 C, an OTEC system can produce a significant amount of power . Warm water is collected on the surface of the tropical ocean and pumped by a warm water pump . The water is pumped through the boiler, where some of the water is used to heat the working fluid, usually propane or some similar material . If it is cooler you can use a material with a lower boiling point like ammonia ( - 33  ° C) . The vapour expands through a turbine which is coupled to a generator that generates electric power . Cold water from the bottom is pumped through the condensers , where the vapour returns to the liquid state. The fluid is pumped back into the boiler.

3. Types of Energy C onversion Systems There are three types of OTEC designs: Closed Cycle OTEC System Open Cycle OTEC System Hybrid Cycle OTEC System . Among these three systems, closed and open cycle systems are different . Hybrid cycle is a combination of both closed and open cycle systems . In this presentation I’m explaining about Closed and Open cycle OTEC Systems.

4. CLOSED CYCLE OTEC SYSTEM

5. Closed cycle is also called as Anderson cycle. The components of a closed cycle system are heat exchangers, turbo generator, feed pump. Closed cycle system uses fluid with a low boiling point, such as  ammonia (N H 3 ) , to power a turbine to generate electricity.  Warm surface  sea water  is pumped through a heat exchanger to vaporize the fluid.  The expanding vapour turns the turbo-generator and generates electricity. Cold water is pumped through a second heat exchanger i.e. condenser, it condenses the vapour into a liquid. The condensed liquid is pressurised with the help of feed pump and is send into the evaporator. Due to the repeatability of the same working fluid, whose flow path and thermodynamic process represents closed loop, hence it is named as closed cycle.

6. OPEN CYCLE OTEC SYSTEM

7. Open cycle system is also called as Claude cycle. Open-cycle OTEC uses warm surface water directly to make electricity .  The warm sea water from surface is sent into the Deaerator. The function of deaerator to remove the dissolved gases from the fluid and the non-condensable gases is send into the atmosphere, The condensable fluid is sent into the flash evaporator to convert it into steam. The warm water discharges away from the evaporator. The low pressure steam from the evaporator flows through the turbine and hits the blades to rotate. The turbine shaft is connected to a generator which produces electricity. The exhaust steam from the turbine is transferred directly to the condenser. The cold water from the deeper layers of ocean is taken to the condenser and is sprinkled to convert the exhaust steam into a liquid. The liquid is sent to the deeper layers of ocean an it is recycled.

8. ADVANTAGES AND DISADVANTAGES OF OTEC ADVANTAGES DISADVANTAGES Cleaner, No air pollution. More expensive than power from fossil fuels. It can produce massive amount of electrical energy. Electricity must also be produced to land. Helps in producing fuels such as hydrogen, ammonia and methanol. OTEC plants must be located where a difference of about 20 C occurs year around. Has the potential to meet all the world’s energy needs Less efficient than coal