20 kW ORC Turbine Off-Design Performance Analysis

The temperature difference between the surface water and deep sea water is about 20~. This temperature difference can be converted into mechanical power. The mechanical power can be converted to electricity through a generator. However, temperature difference is relatively small compared with that of traditional steam turbines. It is difficult to apply steam turbine technology for this small temperature difference. To use small temperature difference for making energy, proper working fluid with high saturation pressure at low temperature and optimized turbine design for the working fluid are needed. Since the deep ocean is not only heat source available authors evaluated the performance of the designed turbine system for other heat source which is slightly higher than the design temperature difference of the turbine. The present study focuses on the turbine for 20 kW OTEC system with the real gas property. It includes the determination of working fluids, meridional design, turbine layout and 3D CFD results. With off-design point analysis, the full performance of 20kW OTEC turbine is mapped. Through the research, one stage radial type turbine with R32 as working fluid is successfully developed and can be applied to other high temperature heat source.