Renewable energy from the sea - organic Rankine Cycle using ocean thermal energy conversion

Abstract

Rankine cycles using refrigerant- and benzene-series fluids as working fluids in converting low-grade energy from renewable energy resources such as solar energy and ocean thermal energy were investigated in this study. The main purpose is to verify the feasibility of utilizing ocean energy (i.e., ocean thermal energy conversion, OTEC) which can also be combined with solar energy in an organic Rankine Cycle (ORC) to generate electricity. Parameters under investigation were turbine inlet temperature, turbine inlet pressure, condenser exit temperature, turbine exit quality, overall irrversibility, and system efficiency. Results indicate that wet fluids with very steep saturated vapor curves in T-s diagram have a better overall performance in energy conversion efficiencies than that of dry fluids. It can also be shown that all the working fluids have a similar behavior of the efficiency-condenser exit temperature relationship. Furthermore, an appropriate combination of solar energy and an ORC system with a higher turbine inlet temperature and a lower condenser temperature (as operated deeply under sea level) would provide an economically feasible and environment-friendly renewable energy conversion system.