Investigation of industrial high-temperature heat pumps for simultaneous heating and cooling: A brewery case study

Process industries are responsible for a large share of the global energy demand. While refrigeration systems are used in the industry for the supply of cooling, the introduction of high-temperature heat pumps (HTHPs) and electric boilers to supply heat is necessary for the electrification of this industry. Combining the refrigeration system and the HTHP may offer an opportunity to improve the overall efficiency and facilitate the integration of HTHP. However, fluctuating, and non-continuous demands make the integration of a combined heat pump for simultaneous heating and cooling (HPS) more challenging as the heating and cooling capacity for such a system is coupled.

This study compared a cascade HPS with an R-717 bottom cycle and R-718 top cycle to a reference system consisting of a R-717 refrigeration system releasing excess heat to the ambient and a HTHP with R-717 and R-718 using the ambient as a heat source. The HPS configuration included heat exchangers with ambient air, and ambient heat sources to meet all combinations of heating and cooling demands. The comparison was carried out for an industrial brewery case and was based on numerical modelling.

For each combination of heating and cooling load the usage of ambient air as heat source and sink was adapted and simultaneously the pressure levels in the HPS were optimized for minimum electricity consumption. The influence of the ambient temperature was also analysed.

At design conditions the electricity consumption of the HPS was 9.8 % lower than the electricity consumption of reference system, but only 2.1 % lower on a yearly basis, due to the fluctuating demand profiles. This indicates that the HPS did not offer a substantial improvement in in terms of thermal efficiency compared to the reference system.