Research and Development of MEMS Turbine Generator for Miniature Organic Rankine Cycle System

This paper proposes miniature turbine structures that are aimed for a miniature Rankine cycle generator. For the IoT (Internet of Things) society, maintenance free, and miniaturized power source is demanded. Among several candidate, we have researched miniature power generators that transform an environmental wasting energy into electrical power. In order to get a high power, Rankine cycle generator that using an electromagnetic induction type is employed conventionally. However, the size is much larger than the IoT device. For this purpose, we developed IoT size miniature Rankine cycle generator. To realize the miniature Rankine cycle structure, MEMS (Micro Electro Mechanical Systems) processes and organic Rankine cycle systems using a low boiling point material have been applied. In this paper, combinations of the miniature turbine and a 3-dimensional flow path that is the part of the organic Rankine cycle system are designed and fabricated by the MEMS process. Dimensions of the MEMS structure were 11.26 mm, 10.33 mm, 7.96 mm. It showed a rotational motion by the low boiling point material, and the maximum speed was 76,923 rpm at 355 K and 0.3 MPa. Moreover, the output fluid changed from the gas phase to gas-liquid two-phase.