Current and future operation scenarios for a 50,000 MWh district heating system.

The performance of Pimlico District Heating Undertaking (PDHU), in London, with an annual heating load of 50,000 MWh was analysed throughout 2012. Half-hourly data for the system were investigated to determine the natural gas consumed, operation of the 2500 m3 accumulator, the two 1.6 MWe combined heat and power (CHP) engines, the three 8 MW boilers, the electricity import and export and the consumers' heat consumption. These data were used to characterise the current performance in detail, and an energy flow diagram for the system energy flows was generated. The modulating efficiencies of the boilers varied from 84% to 91%, whereas the CHP engines performed with a modulating near constant electrical efficiency of 40%, but with a thermal efficiency that decreases with higher load. The current operation of the plant is compared across 10 scenarios. These scenarios were compared while (i) using the accumulator more effectively to let the boilers operate at full load only and (ii) using the provided maintenance agreement contract of the CHP engines to guarantee their good operation. Optimising the operation of the current plant reduces the annual heating cost of £165,000 or 12% and investing in additional CHP capacity can reduce the CO2 emissions by 28%.