Organic Rankine cycle thermal architecture - From concept to demonstration

This paper describes some of the important features of a new experimental ORC test-rig that may contribute towards increased overall conversion efficiencies. These features include, firstly, a variable heat source setup, allowing the potential to replicate a wide range of realistic gaseous sources. Secondly, the direct utilisation of the High-Temperature (HT) exhaust gases, which is expected to lower the specific evaporator exergy cost by 22%. Thirdly, deployment of HT water blends, this is estimated to increase the potential of overall conversion efficiency by 2.4 times. Fourthly, a flexible thermal platform, offering multiple and efficient heat utilisation, with a holistic approach to NOx reduction, downsizing and exhaust heat recovery. Finally, advanced process conditions (e.g. 29.3 bar, 270.9 °C), which corresponds to the near-optimal region, and offers the possibility of a 12.5% conversion rate of heat recovered to expansion power. The potential benefits are quantified using a combination of published literature, procurement findings, simulation results (Aspen HYSYS) and preliminary experimental measurements (NI LabVIEW). The paper concludes with the rational for the next intended research effort, i.e. high-pressure ratio and two-phase expansion machines.