Low-grade waste heat integration in distributed energy generation systems - An economic optimization approach

This paper proposes a Mixed-Integer Linear Programming (MILP) formulation for the economic optimization of the synthesis, design, and operation of an energy supply system of a manufacturing company. The multi-period approach incorporates both Heat Upgrading Technologies (HUTs) and conventional Distributed Energy Ressources (DER). Temperature requirements of heating and cooling demands are addressed explicitly and fluctuating ambient temperatures are considered, this gives rise to the possibility of temperature dependent modeling of technology efficiencies. The model enables the planner to consider waste heat recovery from hot process streams or from refrigeration cycles via direct heat integration or HUTs, such as mechanical heat pumps. Furthermore, it enables the planner to evaluate the complex interactions of HUTs with Combined Heat and Power (CHP) plants. To illustrate the practicability of the presented modeling approach, it is applied to a real-world case study. Furthermore, we exemplify how the optimal design is adjusted if HUTs and DER are investigated integrally in contrast to an isolated optimization.