Design and dynamic investigation of low-grade power generation systems with CO₂ transcritical power cycles and R245fa organic Rankine cycles

This paper deals with the dynamic experimental investigation on low-grade power generation systems with CO₂ transcritical power cycles (T-CO₂) and R245fa organic Rankine cycles (ORC). These two systems were heated indirectly by exhaust gases of an 80 kWe micro-turbine CHP unit through a hot thermal oil system. The main components of each test system included a plate-type gas generator/evaporator, a turboexpander with high speed generator, a finned-tube air cooled condenser and a liquid pump. Both test rigs were fully commissioned and instrumented from which comprehensive dynamic experimental investigations were conducted to examine the effects of some important dynamic operational processes on system performance. These included the system start-up, variation of working fluid pump speed, change of thermal oil pump speed and system shutdown. These can lead to fully understand the dynamic and inertia behaviours of the system operations and thus to obtain robust controls. The experimental results reveal that working fluid mass flow rates are affected significantly by the start-up and shutdown processes, followed by the temperatures and pressures at turbine inlets and outlets. The research outcomes can contribute significantly to understand the system dynamic operating processes and thus instruct the system controls and safety operations.