Advances in high-temperature heat pump technologies for industrial process applications with large temperature glides: Assessing the potential for carbon dioxide as a refrigerant

Industrial process heat users face great uncertainty due to the cost and complexity of transitioning to renewable energy sources. High-temperature heat pumps offer a promising solution due to the high Coefficients of Performance that can be achieved compared to electric heating. However, it can be difficult to identify which heat pump systems are most suitable for which applications. This is particularly true for transcritical heat pumps where the temperature glide in the gas cooler (equivalent to a condenser) is very high. This paper aims to quantify the potential decarbonisation impact that could be realised from the development of new high-temperature heat pump cycles with large temperature glides (>100 °C), using carbon dioxide as the refrigerant. To this end, this study identifies potential process applications, including suitable sink and source streams to supply the heat pump system, and discusses the opportunities and barriers for high-temperature heat pump implementation. Thermodynamic models of three heat pump cycles were used to estimate the Coefficients of Performance and the carbon abatement potential for the identified applications. Drying applications such as for producing milk powder, starch and instant coffee, were identified as suitable applications and the Coefficients of Performance estimated based on the required process temperatures and available waste heat.