Deep Water Cooled ORC for Offshore Floating Oil Platform Applications

Abstract

Normal 0 21 false false false ES X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Normal Tablo; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif; mso-ansi-language:EN-US; mso-fareast-language:EN-US;} Due to global warming, environmental pollution and cost reduction, increasing efficiency of electricity conversion has become a key issue for the offshore market. This paper proposes an Organic Rankine Cycle (ORC), which uses heat waste from exhaust gases of an FPSO (Floating, Production, Storage and Offloading unit) as heating source, and deep ocean water as cooling source. A genetic algorithm optimization was conducted targeting maximization of net power output, by taking in to consideration of 23 working fluids. Expander inlet temperature and pressure were set as independent variables. The analysis encompasses subcritical or supercritical conditions and recuperation was included in a second version of the system as an option. The first configuration presented ethanol as optimal fluid, followed by toluene and the second configuration indicated cyclohexane followed by ethanol. Use of recuperation, when feasible, increased power output specially for cycles operating with dry and isentropic fluids, presenting an average contribution of 22.7%. Net power and efficiency results from ORC using deep sea water in condenser were presented and compared with ORC using shallow ocean water as cooling source and with Carnot efficiency operating under the same temperatures. Use of deep water raised net power output by 23.3% (cyclohexane recuperative ORC) and 12.5% (ethanol non-recuperative ORC) for the optimal configurations.