Increasing district heating networks efficiency by means of temperature-flexible operation

Abstract

Abstract Reducing heat losses from district heating networks is one of the main ways of ensuring the economic and sustainable operation an overall heating system that consists of heat generation, distribution and consumption. In newly-built heating networks, heat losses can be reduced by increasing linear heat density, reducing pipe diameters, or improving pipe insulation. This work investigates a novel scientific approach for a system extension, which significantly reduces network losses by installing heat storages at end-consumer locations. Simulations were run to determine whether heat losses in existing local district heating networks could be further reduced by switching off the district heating network in low-load times. While the heating network is turned off, customers’ heat demand may be served by previously loaded, decentralised storage units, situated in close proximity to consumers. In order to remain as realistic as possible, all technical parameters and heat consumption data of two district heating networks in real operation were used as input data for the simulations. As a result of this novel strategy, network losses of a given year could be reduced by up to 34%. This means that the total amount of heat fed into the network was reduced by up to 6%. The storage sizes were optimised for the low load time in the summer and have not been changed for the other seasons. Pending further recommendations, it should be stated that the investigated intermittent operation leads to additional low cycle fatigue and therefore, the steel pipe used might have a reduced lifetime.