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Evaluation of District Heating with Regard to Individual Systems – Analysis of Carbon and Cost Allocation in Cogeneration Units

District heating has been proven as effective way of increasing energy efficiency and reducing environmental impact. Besides mentioned, these systems have additional benefits such as integration of low-temperature renewable energy sources, including excess heat from different industrial processes, and highly efficient transformation of electrical energy to thermal by means of power-to-heat technologies in combination with thermal storage. Although, district heating has large share in heating sector in Northern Europe, Central-Eastern European countries often do not utilize potential for further thermal network expansion neither support new district heating project implementation. One of the main reasons for this are relatively low energy market prices, which diminish economic feasibility of the proposed projects. Even though there are numerous optimization methods which optimize district heating supply capacities in order to minimize total cost, they rarely provide comparison with individual heating solutions. This paper presents a novel method of evaluation of district heating and regarding individual systems by using multi- objective optimization approach and different allocation in cogeneration units. Objective functions have been defined as minimization of total discounted cost, environmental impact and exergy efficiency. Optimization variables are supply capacities and hourly operation of the system on hourly level for a whole year. In order to deal with multi-objective optimization epsilon-constraint method has been used. District heating system has been modelled by means of mixed-integer linear programming. Free and open- source programming language called Julia, in combination with Gurobi solver has been used. The main outcome of this research are energy market prices for which district heating systems have lower environmental impact and exergy destruction than individual heating solution, while at the same time being economically feasible. It has been shown how CHP allocation methods based on power loss have crucial impact on the acquired results.

district heating ; energy planning ; power-to-heat ; multi-objective optimization ; CHP allocation

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