Techno-economic comparison of a high-temperature heat pump and an organic Rankine cycle machine for low-grade waste heat recovery in UK industry

This paper presents a comparison of a high-temperature heat pump and an organic Rankine cycle (ORC) plant for the recovery of low-grade waste heat for a UK inorganic chemicals case study. Superficially, the two technologies appear equally suitable for use here; therefore, both technologies are modelled in order to provide data for a comparison in terms of expected technical and economic performance. Both technologies are proven to be feasible in this case study, with the heat pump helping to significantly reduce the natural gas requirement of the plant and the ORC producing a significant net output of electricity. This leads to each technology being attractive from the economic and environmental viewpoints. However, the proposed ORC achieves greater potential greenhouse gas reductions (499 tCO 2 eq/year as opposed to 401 tCO 2 eq/year) and greater potential cost savings (£69 000/year as opposed to £37 800/year). Therefore, the ORC machine is shown to be the preferred technology in this case. A sensitivity analysis based on continuation of the utility cost trends is performed and shows that the ORC plant would gain in profitability in future years whereas the potential profit of the heat pump system would diminish to almost zero by 2020. Such results suggest that ORCs may be further utilised in future years whilst the use of heat pumps may decline. Copyright , Oxford University Press.