DESIGN AND CONSTRUCTION OF A REVERSIBLE ORC TEST RIG FOR GEOTHERMAL CHP APPLICATIONS

Abstract

for their ability to supply heat or electricity flexibly. While many publications focus on their application in Carnot batteries or domestic systems, geothermal applications got less attention. In geothermal combined heat and power plants, reversible ORCs offer the possibility to generate electricity in times of low heat demand and supply additional heat to a district heating network (DHN) in peak load times. In previous work, the authors showed that this increases plant utilisation and reduces the load of commonly used peak-load gas boilers. This work presents the design and construction of a fully reversible ORC test rig capable of flexible operation as ORC or high-temperature heat pump (HTHP). It extends the state of the art by design and construction of a test rig for experimental validation of a previously untested cycle layout for geothermal applications. The test rig is supplied by a 200 kW hot water heating circuit as a heat source and uses a fully reversible 20 kW twin-screw machine. A closed loop intermediate cooling circuit allows simulating a DHN with varying temperature levels and mass flows during HTHP operation. This paper provides insights into the design methodology and the test rig’s intended operating range and performance. Thus, the paper provides valuable insights for the research community regarding conceptual and experimental activities on reversible ORC systems. Moreover, an in-depth description of the constructed test rig, its components and instrumentation and finally the preliminary control concepts are given. Commissioning and first experimental results are expected in the year 2023.