Spain. The first functional prototype of a high-temperature heat pump in Spain for the recovery of industrial waste heat was presented by scientists from the research group in Thermal and Energy Systems Engineering (Istener) of the Universitat Jaume I de Castelló, in collaboration with the company Rank.
The first experimental results of this prototype, which will move towards more efficient energy systems to cope with climate change, have been published in the journal Applied Energy. In addition, they were presented at the 25th edition of the IIR International Refrigeration Congress held in Montreal (Canada).
This new prototype designed at the UJI uses HFC-245fa as a refrigerant, well known in organic Rankine cycles, but not so common in refrigeration or conventional heat pumps. "Its main advantage is the high critical temperature of this fluid (153.86 °C), which allows to produce steam or pressurized water up to 140 °C", explains the researcher of the Istener group, Carlos Mateu. However, this refrigerant has a high global warming power (GWP), of 858, "so it is necessary to search for more sustainable refrigerants that provide similar energy performance as said refrigerant; consequently, this prototype also sets a benchmark for researching new refrigerants with low GWP that are environmentally sustainable," adds Mateu. In fact, in the coming months, potential low-GWP refrigerants that will replace HFC-245fa in high-temperature heat pumps will be experimentally investigated.
The conclusions of this research demonstrate that this technology, according to Mateu, "has a promising future in the decarbonization of the planet, since useful heat has been generated at 140 °C from a low-temperature waste heat source at 80 °C, obtaining a COP of 2.23", as it will reduce greenhouse gas emissions responsible for global warming. In turn, it has been shown that the integration of this technology in cogeneration systems to recover heat from engine cooling oil reduces CO2 equivalent emissions by up to 57% compared to conventional heat generation systems, such as natural gas boilers.
Energy Revaluation
UJI professor Joaquín Navarro Esbrí, coordinator of the Istener research group and expert in machines and heat engines, argues that the concern to mitigate climate change calls for new energy systems that are increasingly efficient and sustainable that are capable of producing energy efficiently, thus reducing greenhouse gas emissions. "From this need – in the words of the professor – high-temperature heat pumps for the recovery of industrial waste heat are born. These systems work exactly like air conditioners, chillers and other vapor compression systems, with the difference that operating temperatures have been increased using new compressor technology and new refrigerants, among other components."
Currently, much of the energy in the industrial sector is discharged into the environment without the possibility of recovering it due to the lack of technology capable of it. Engine cooling oil, exhaust fumes or cooling from industrial processes are some examples of sources of industrial waste heat that due to their low temperature are not useful for industry and due to lack of technology can not be reused. "This is where the high-temperature heat pump has a promising future as a system capable of recovering this industrial heat at low temperature and revaluing it so that it is useful again in industrial processes," concludes the Istener coordinator.
The high-temperature heat pump, unlike other steam compression systems, is capable of operating with evaporation temperatures between 60-90 °C and with condensation temperatures between 110-150 °C. With a small contribution of electrical energy to feed the compressor, this type of systems are able to absorb waste heat and produce a heat useful for industry, between 120-150 °C, in the form of steam or pressurized water with high efficiency. This generated heat is used in processes of petrochemical, food or ceramic industries, among others, reducing the fossil fuel consumption of heat generation systems and, with it, greenhouse gas emissions.
The Istener research group belongs to the Area of Machines and Thermal Engines of the Department of Mechanics and Construction of the Universitat Jaume I de Castelló. His main lines of research focus on the development of microgeneration and revaluation systems from low-temperature heat sources, specifically, Organic Rankine Cycles (ORC) and high-temperature heat pumps. In addition, his research also focuses on the search for sustainable refrigerants with low GWP in both refrigeration systems and in organic Rankine cycles and high-temperature heat pumps.
Source: Universitat Jaume I de Castelló.
