OTEC Pilot Plant Heat Engine (1979)

ABSTRACT The Johns Hopkins University Applied Physics Laboratory has completed the preliminary engineering design for a pilot plant intended to demonstrate the construction feasibility, performance, operation, and economics of power generation on ocean thermal energy conversion (OTEC) plant-ships utilizing the temperature difference between the surface and deep waters of the tropical oceans. This work has been funded by the U.S. Department of Energy and the Maritime Administration, and was presented in a design report in late 1978. This paper summarizes the heat-engine system design and integration in the platform and describes system components and their performance and construction requirements, together with the computed overall cycle performance and operation. Ancillary equipment and platform arrangement and support requirements are discussed as to their effect on the platform design. The heat engine and platform design is based upon the APL folded-tube; shell-less heat exchanger module concept as developed from analytical and experimental work previously reported. The heat engine design discussed is among the candidates for the construction of large commercial OTEC plant-ships. In the APL concept, the plant-ships will cruise (graze) the tropical oceans to utilize the maximum available ocean temperature difference. They will produce energy-intensive products such as ammonia, which can be synthesized from sea water and air and shipped to U.S. or foreign ports for use as fertilizer or as a hydrogen fuel carrier. The pilot plant design presented is for a 10 to 20 megawatt net output plant made up of 2.5-MWe net heat exchanger modules manifolded to 5 MWe net turbine-generator sets. In this approach, it is anticipated that all construction requirements, manifolding, cycle control, and installation and operational requirements can be determined and evaluated for the detailed design of large commercial vessels. The 5-MWe module sizing will permit continuous performance evaluation with one unit down for modification and/or equipment maintenance, and will also permit comparison of cycle or control changes on similar units under identical operating conditions. INTRODUCTION This preliminary engineering design of a 10-MWe (net) power system for a 10/20-MWe pilot plant or modular experiment has been focused on the primary objective of demonstrating OTEC power generation and includes an energy dissipation system for demonstration of power generation but does not address details of onboard chemical plants or transmission of generated power. The pilot-plantship is designed around the APL folded-tube, "shell-less" heat exchanger concept, but the overall design of central or common OTEC systems and services including lift systems and platform services, provides for incorporation of alternative heat-exchanger and power-system designs that may result from ongoing DOE programs. The platform and system design are based upon environmental conditions in the proposed cruising area in the South Atlantic1, 2 and the sea-keeping/survival requirement for the 100-yr storm in that area. The major impact of design modifications for operation at other sites will be on platform modifications required for the more severe design wave survival conditions with attendant possible modifications to the OTEC power systems layout.