The Indian OTEC Program

Abstract It is planned to construct a pilot floating OTEC plant with a rating of 1MW gross off the coast of India. Preliminarydesign calculations that impact on the sea water systems have been completed. The factors that affect the choice of configuration for the cold water pipe and mooring are discussed. At smaller ratings the cost of the sea water systems is likely to be a larger fraction of the overall plant cost and thus merits detailed investigations. Introduction Commercial energy consumption (coal, oil & gas, electricity)in India has increased from 19.76 million tonnes of coal equivalent (MTCE) in 1953–54 to 101.5 MTCE in 1990-91. The contribution by coal, oil & gas and electricity for the latter period is 39, 43.4 and 17.6 percent respectively [1]. As of 1996–97 the lifespan of known reserves of oil & gas is around 20 years and coal reserves are estimated to last for about 200 years. The installed capacity of electrical generation is 96000 MW (1996–97) and is insufficient to meet the current demand. In such a scenario, the development of alternative sources of energy is an imperative. Further, it would be desirable to pursue an energy resource that can be utilised in a sustainable manner. This is possible through renewable sources. For tropical countries with a long coast line, ocean thermal energy conversion (OTEC) appears to be a promising source. Ocean Thermal Energy or OTEC harnesses energy through the natural thermal gradient of the ocean depths which acts as a heat engine for a thermodynamic cycle. In tropical countries like India, this temperature difference is above 20°C between the surface of the ocean and at a depth of800-100Om and the annual fluctuation in this value is only l°C. Based on this temperature difference, the area of OTEC resource within India's EEZ is estimated to be 1.5 × 106 km 2. An acceptable power density for OTEC plants has been estimated by researchers to be 0.2 MW/km2. With such a spacing, and allowing 40° for parasitic losses in the OTEC plants, the estimated OTEC potential in India is around 180, OOOMW, Previous calculations have shown that floating OTEC plants can be competitive at ratings of the order of 50MW. [2]. While the ultimate aim is to build plants of such ratings, a demonstration pilot plant of a smaller capacity to validate the design of subsystems such as heat exchangers, turbine, and sea water systems appears rational. This paper attempts to study the advantages and disadvantages of variousconfigurations of the sea water systems (cold water pipe and moorings) with respect to the complexity, feasibility and cost in the Indian context. Conceptual basis for pilot plant Based on the bathymetry of the ocean, three options for OTEC plants exist. They could be land based, shelf based or floating plants. Land based plants are feasible in the islands of India.