Theoretical cost and energy optimisation of a 4th generation net-zero district heating system with different thermal energy storage technologies.

A model was used to simulate and optimise a speculative district heating (DH) system for an existing urban area in Loughborough, UK. Heat was supplied using only renewable heat sources (RHS) with long and short duration thermal energy storage (TES) systems used to address mismatch between heat generation and demand. For an 18month simulation period, a) building heat loads, b) heat generated, c) heat flow to and from stores, and d), heat losses from the stores and network were calculated using hourly weather data, network and building characteristics. RHS included evacuated-tube solar thermal collectors (ETSTCs), and ground and air source heat pumps powered by electricity generated by solar-photovoltaic (PV) and Wind turbines (Wind). The effect of long-term TES system volume and charging temperature on the calculated DH system cost per dwelling, and the calculated DH system energy efficiency was assessed. The minimum cost of the DH system was obtained by modifying the capacity of installed Wind and PV, while ensuring that heat demands were met in every hour of the simulation. A minimum cost per dwelling of 12,278 pound was predicted with an energy efficiency of 84.84 % for a long term TES volume of 15,000 m3 and temperature of 60 degrees C.