Techno-economic relevance of absorption chillers to enhance existing 3GDH

This article studies the economical, technical and environmental aspects of a third generation district heating (DH) network with absorption chillers installed at substation level in order to satisfy the cooling demands. This network solution hence takes advantage of the distribution facilities of existing DH systems. The study aims at evaluating the technical and environmental performances of this new district heating architecture, when sized and operated according to an economic objective using the Mixed Integer Linear Programming (MILP) optimization formalism. It is compared to the case where cooling demands are met using individual chillers. The paper first presents the production, distribution, demand and storage models. Regarding the demand side, different heating and cooling scenarios are studied by varying the proportions of residential and tertiary buildings. The model is fed in a second part with data from the French context. In particular, we rely on typical French weather conditions, thermal loads and energy costs. The analysis of the results focuses on the cooling part. It appears that the thermal network solution achieves on average a 3.6% reduction in the levelized cost of space cooling energy. In the worst case space cooling exergy efficiency goes through a 82% decrease. GHG emissions decrease on average by 7.7% thanks to the absence of leakage of refrigerant with high global warming potential. Overall, these emissions are low due to the low carbon content of French electricity.