18 May 2017
Industrial heating consumes a significant fraction of the energy consumed globally. Heating at temperatures higher than about 100°C is predominantly provided through combustion of fossil fuels with uncertain prices and well recognised environmental impacts, including climate change. A significant fraction of industrial input energy is wasted as low temperature heat (e.g. dryer vent gases or cooling water) that could be lifted by high temperature heat pumps (HTHPs) to temperatures meeting nearby heating duties.
A novel HTHP with 32 kWth heating capacity is evaluated in this paper. It is based on a reciprocating compressor adapted from a piston expander previously developed for a small-scale organic Rankine cycle system. The expander has been extensively tested at high temperatures and has demonstrated high efficiencies. The compressor was constructed by solely adjusting the expander valve system. HFO-1336mzz(Z) (cis-CF3CH=CHCF3; previously referred to as DR-2), with a global warming potential of 2, was selected as the working fluid. HFO-1336mzz(Z) has attractive safety, environmental and thermodynamic properties and high chemical stability at high temperatures. Heat pump tests demonstrated heating from a 90 °C heat source to 130 °C and 150 °C with a Coefficient of Performance for heating of 4.6 and 2.7, respectively. Work is ongoing to demonstrate higher heating temperatures and optimise performance in support of commercialisation in 2017. The new HTHP with HFO-1336mzz(Z) could enable the utilisation of abundantly available low temperature heat to meet heating duties at higher temperatures, with equal or higher energy efficiencies and lower environmental impacts than with incumbent working fluids.