Thermodynamic analyses and experimental investigations on the net efficiency of a small-scale organic Rankine cycle prototype

Organic Rankine cycle (ORC) is an effective technical route to achieve power generation from low-grade heat energy. In an ORC system, the working medium pump and cooling system consume much more expander power than the steam Rankine cycle. But the power self-consumptions of ORC system did not receive enough attention in public literatures. In this paper, an ORC prototype with R123 as working medium was constructed. The expander power and the power consumptions by all power-consumer equipment were measured. The net efficiency and net power of the ORC prototype achieved 5.02% and 4.4 kW, respectively. A method was proposed to find out the key point that affects the net efficiency. It was found that the irreversible losses in expander led to the largest net efficiency drop of the ORC prototype, then the next was the work consumed by the cooling fan and working medium pump. A thermodynamic analysis model was also developed to predict the net efficiency of the prototype and the theoretical values were basically consistent with the experimental results.