Session: 4.1.1 - Renewable Energy Systems

Paper Number: 118655

118655 - Design and Performance Analysis of 1-kW Microturbine of Organic Rankine Cycle applied for Solar Heat Collector 

Organic Rankine Cycle (ORC) is a thermodynamic cycle similar to the conventional Rankine cycle, but it uses an organic refrigerant instead of water as a working fluid. One of the main advantages of ORC is that it can use a wide range of heat sources, such as waste heat from industrial processes, geothermal sources and solar heat energy, etc. In this study, a 1-kW_e ORC microturbine is designed, considering the thermal characteristics generated by the concentrating solar collector. , and we do not deal with this device in this study. The designed microturbine is adaptable to a 1-kW_e ORC power generation system. This system is capable of obtaining additional economic benefits by adding electrical power generation to the existing structure of solar collectors used for space heating and hot water purposes. The working fluid for the ORC system developed in this study is selected as R1233zd(E), which possesses favorable thermodynamic properties. This non-flammable refrigerant has zero ozone depletion potential (ODP) and a very low global warming potential (GWP), making it known as a highly environmentally friendly refrigerant. A cycle analysis of the ORC system that utilizes low-temperature solar heat as its heat source is performed by using SoftlnWay's AxCYCLE to obtain the thermodynamic efficiency of the system. The cycle analysis is conducted based on the electrical generation with 1-kW_e by considering both the average heat power of the solar collector and operating conditions of the turbine. We obtain a cycle thermal efficiency of about 14%. In this regard, effective turbine development is required to achieve the highest performance in small-scale ORC systems. An axial flow turbine with single stator and single rotor is designed for this study. The operating conditions for the turbine mean-line design are applied, with an inlet temperature of 145 °C, an inlet pressure of 10 bar, and a flow rate of 0.031 kg/s, respectively. As a result of the design, the microturbine is characterized by a very small size with a tip diameter of about 26 mm, and the total-to-total efficiency of the turbine based on a rotational speed of 120,000 rpm is 73.2% at a pressure ratio of 7.2. To validate the effectiveness of the design methodology, a three-dimensional computational fluid analysis is conducted to investigate the fluid flow passing through the blades. This is performed by using STAR-CCM+ software to obtain the pressure field, temperature field, and Mach field. In addition, a parametric study is conducted to investigate the effect of key input parameters on turbine performance. For the turbine parametric studies mentioned above, various refrigerants are adopted as working fluids and compared with each other. As a result, it is shown that the turbine inlet temperature, mass flow rate, and pressure ratio should be increased to achieve high power output. In order to verify the efficiency and power characteristics of the turbine, a 1-kW_e capacity ORC test rig will be constructed. Experimental investigations will be conducted to analyze the performance of the turbine under various operating conditions.

Presenting Author: Woong Jun Ko Korea Institute of Industrial Technology

Presenting Author Biography: [2021-2023] Green Energy and Nano Technology R&D group, Korea Institute of Industrial Technology / Researcher