Modelling and analysis of a district heating network

District heating systems have the potential to contribute to the UK renewable energy targets. However, there are a number of economic barriers which would have to be addressed in order to make district heating competitive in comparison with alternative heating technologies. The objective of this research was to model and analyse a district heating network and develop an optimisation method to calculate the minimum capital investment, heat losses and pump energy consumption. Firstly, modelling and analysis of a district heating network was conducted to obtain district heating design cases with minimum annual total energy consumption, annual total exergy consumption and annualised cost. Then through the analysis, a two-stage programming model was developed which synthesised design and optimal operation of a district heating network. The optimisation was used to minimise annual total energy consumption, annual total exergy consumption or annualised cost of the heat network by selecting suitable pump and pipe sizes, taking into account different parameters such as target pressure loss, temperature regime and operating strategy. The optimisation technique was used to investigate two different case studies, with high and low heat density. In all cases, a variable flow and variable supply temperature operating method was found to be beneficial. Design cases with minimum annual total energy consumption and annualised cost used rather small pipe diameters and large pressure drops. To achieve the minimum annual total exergy consumption a design case with larger pipe diameters and smaller pressure loss was found to be desirable. It was observed that by reducing the water temperature and increasing temperature difference between supply and return pipes, the annual total energy consumption, annual total exergy consumption and the annualised cost were reduced. It was also shown that district heating in an area with high heat density is more energy efficient and cost effective.