Refrigerant lubricant interaction in high-temperature heat pump and organic Rankine cycle systems.

High-Temperature Heat Pumps (HTHPs) and Organic Rankine Cycles (ORCs) are well defined technologies used in energy conversion. Ongoing research and development of equipment and processes is enabling the operating envelope of these technologies to be extended to achieve higher temperatures and pressures. Lubricant plays a key functional role within primary plant, namely compressors and expanders preventing damage and wear, while also sealing, preventing corrosion and reducing energy requirements. These lubricant oils need to interact with low global warming potential refrigerant combinations without negating operational performance or damaging plant and equipment. An evaluation of these refrigerant lubricant compositions through testing is essential to ensure optimum performance is maintained within operational limits. This study is linked to an EU project CHESTER (Compressed Heat Energy STorage for Energy from Renewable sources) and reviews research based on HTHPs and ORCs that serves to provide a bases to understand integration of lubricant basestocks and working fluids to meet the demands of high temperature applications.