Ocean Thermal Energy Conversion (OTEC): Temperature Increase System (TIS) Assisted

Efficiency is improved in ocean thermal energy conversion (OTEC) by increasing the temperature of heat supplied to a closed Rankine cycle system substantially above the warm sea water temperature. This temperature increase is accomplished in a separate system by reacting gaseous ammonia with water to produce sensible heat at a high temperature; the ammonia is later fractionated from the water using lower temperature heat from the existing heat source. The method is illustrated with design of a 100 MWe pilot plant suitable for OTEC application, using ammonia as the working fluid, with a thermal efficiency > 2.4 times the efficiency of conventional designs. With the same sea water flows and the same platform space on an OTEC ship, a 100 MWe plant with a temperature increase component would produce 2.5 times the power of a 40 MWe plant of standard design, with a plantship construction cost only 25% higher.