Simultaneous heating and cooling production devices composed by reverse cycle systems under variable loads

• Flexible solutions can be better than standard heat pumps for varying heat demand.
• Adding flexibility is feasible by using a combination of standard heat pumps.
• Overproduction of heat at a high exergy level can be avoided by adding flexibility.

Energy and exergy analysis leads to integrated solutions for process design. However, if the overall process design is optimized its robustness and its operability could be major weaknesses. This paper focuses on an integrated process where a reverse cycle system answers both heating and cooling demands. For variable heat demands, the aforementioned reverse cycle system may be inadequate. Therefore, one option is to add flexibility to the device by splitting it into two systems. In this paper, in addition to the initial reverse cycle system, five more solutions are proposed and studied: three uncoupled and two partially coupled solutions. First, simplified models are used to compare the different proposed solutions for several nominal operating points. Then, more detailed models are used to consider heating or cooling demand variation. Results show that the flexible solutions designed can be relevant options when heating or cooling demands vary.