Multi-objective optimization of district heating and cooling systems for a one-year time horizon

Besides lowering supply temperatures, the concept of fourth generation of district heating (4DH) also includes integration of heating, cooling and power sector. Due to their high interconnectivity, number of involved technologies and relatively long, but at the same time detailed temporal scale, optimization of such systems presents a challenging task. So far, only hourly district heating multi-objective optimization for a whole year period has been carried out, where detailed district heating and cooling multi-objective optimization has been reserved for small scale utilization and short temporal scale, usually covering specific days or weeks. The main objective of this paper was to develop an hourly based multi-objective optimization district heating and cooling model which is capable of defining supply capacities, including thermal storage size, and their operation for a whole year period. The objective functions are minimization of a total system cost, which includes discounted investment and operational costs, and minimization of environmental impact in terms of carbon dioxide emissions. By using multi-objective optimization, this research shows that for equal level of carbon dioxide emissions, combined district heating and cooling systems have lower total discounted cost when compared to district heating and cooling systems which operate separately. (C) 2018 Elsevier Ltd. All rights reserved.