Energy consumption and economic analyses of a district heating network

An approach for minimisation of the capital costs and energy consumption in a district heating network is presented using a case study based on a district heating network in South Wales, UK. A number of different design cases were simulated using the PSS SINCAL, taking into account different supply and return temperatures and target pressure losses. The operation of the district heating network was synthesised under different design cases using four district heating operating strategies. Optimisation was conducted to obtain the optimal flow rate and supply temperature for the variable flow and variable supply temperature operating strategy. The optimisation model was formulated using the FICO™ Xpress optimisation suite. The objective of optimisation was to minimise the annual total energy consumption and costs. Using each operating strategy, the annual pump energy consumption, heat losses and the equivalent annual cost were found and compared. A variable flow and variable supply temperature operating strategy was found to be beneficial in all cases. Design cases with minimum annual total energy consumption and cost used small pipe diameters and large pressure drops. Further, by increasing temperature difference between supply and return pipes, the annual total energy consumption and the equivalent annual cost were reduced.