‘Base power’ is the power, which is available 24 hours a day and 7 days a week. Geothermal power is the only constant green source of base power, unlike solar and wind power, which are unreliable. Oak Ridge National Laboratory (ORNL) may just have developed a new alternative of base power. ORNL is looking forward to produce electricity using seawater by Ocean Thermal Energy Conversion (OTEC). As per James Klett, an official of ORNL Materials Science and Technology Division, there is a huge difference between the temperature of surface water and the water thousands feet below at the bottom. This temperature difference can be used for generating electricity.
The temperature difference makes OTEC power generation system work and it drives closed loop Rankine cycle power plant.The plant pumps surface water at 25° Celsius, through heat exchanger to boil ammonia. Ammonia in gaseous state spins turbine generator to generate power. The last stage is to cool ammonia to convert it into liquid state using condenser and the entire process is started over again. In the tropics where the temperature difference is about 20°Celsius and above, 3 to 5 terawatts can be produced using the plant without affecting the environment or the ocean temperature.
Considering the current state of OTEC technology at least 20 very large heat exchangers would be needed to commercialize OTEC power plant. This is where Graphite Foam based heat exchangers comes to play. These heat exchangers are developed by Klett and his research team and combines large surface area with high heat conducting capacity. This reduces the size and cost of heat exchangers as well as improves the performance of standard thermal conduction unit. The heat exchanger will be two times effective and the size of the heat exchangers of OTEC plant would be cut down to half.
At present, a laboratory scale heat exchanger is being built by Klett and his colleagues for testing at NELHA (National Energy Laboratory of Hawaii Authority). If it turns out to be a success, OTEC plant will revolutionize power generation. Apart from OTEC the technology used to build these heat exchangers can also be helpful in improving the efficiency of other types of plants.
Via: Dvice
