Development and application of a multicriteria decision support framework for planning or retrofitting district heating systems

CHP-based, combined district heating (DH) systems with gas-fired boilers for peak heating load compensation have several advantages compared to traditional DH systems. They have a relatively high level of energy and environmental efficiency. However, there is a lack of a decision support system aiding in the planning or retrofitting of them. Therefore, the aim of this dissertation is to demonstrate how these kinds of DH systems are designed and operated as well as to develop a decision support framework not only from an economic viewpoint, but also in relation to energy, technology, and environment issues. First, the excessive heat supply rate (EHSR), which indicates the thermal maladjustment extent of heat substations, is presented to determine the installation strategy of peak shaving gas-fired boilers. On this basis, the combined heating alternatives to be addressed are constructed with a different basic heat load ratio; moreover, the design and operation of the system is discussed extensively. Then, the dissertation presents an application-oriented, multi- criteria decision support framework for evaluating different combined heating alternatives in a real-life DH system in Daqing, China. Before doing the multicriteria decision analysis (MCDA), a corresponding criteria aggregation system is developed, based on which criteria weights can be elicited using fuzzy AHP in combination with the concept of a 'complementary judgment matrix' (CJM) and hypothesis test. A feasible weight space instead of a deterministic weight vector is then proposed and utilized in the MCDA. Subsequently, the techno-economic performance, atmospheric environmental impact, reliability, and energy efficiency of the systems are modeled respectively in order to obtain the criteria measurements needed for decision support. Stochastic multicriteria acceptability analysis (SMAA) is implemented to synthetically handle the problem. The results indicate that combined district heating systems consisting of CHP and gas-fired boilers can be economically more feasible and sustainable, and it is environmentally efficient to use gas-fired boilers for peak heating load compensation. The most preferred basic heat load ratio in the demonstration case should be between 0.66 and 0.77, with relatively high confidence factors. In all, the present decision support system can be useful for planning or retrofitting and operating the combined district heating system. Nevertheless, it can be extended and applied to other energy supply systems as well.