Design and Build of a 1 Kilowatt Organic Rankine Cycle Power Generator

Abstract

Organic Rankine Cycle (ORC) systems are capable ofutilising low-enthalpy geothermal sources. The aim of theAbove Ground Geothermal and Allied Technologies(AGGAT) research programme is the development of ORCsystems within New Zealand. An experimental scale ORCsystem, known as ORC-B, was built at the University ofCanterbury to assist with the research and development ofthe system design and component selection process.The unit is a 1 kW ORC consisting of four key components:evaporator, expander, condenser and pump. Selection of theworking fluid was found to be a constraining factor in thedesign. A refrigerant mix known as HFC-M1 was selecteddue to its desirable performance, high safety and ease ofavailability in New Zealand. The heat source for the systemis the exhaust of a Capstone gas turbine. Heat is transferredto the unit’s plate-type evaporator by a thermal oilextraction loop. Cooling is supplied to the plate-typecondenser from the available water supply. A scrollexpander is used to extract work from the system and theevaporator is fed by a high-pressure plunger pump. Theinstrumentation selected allows measurement of theperformance of the system as well as PID control. Thesystem has been designed and constructed and is now readyfor commissioning and testing.