Abstract
Abstract Temperature difference between supply and return distribution medium (water) is a vital factor when assessing the efficiency of a district heating (DH) substation. An accounting for fluctuations and differences of the heat consumption/generation is the key problem in planning DH system operation. The influence of the fluctuating energy consumption on a DH system was studied with actual data, using the DH systems of the Russian cities Krasnoyarsk and Omsk as a case study. Information is visualized in the form of graphs and charts, orderly and clearly comparing certain points. The data includes supply and return temperatures, and heat demand. Clearly visible state of high return temperatures induces more bottleneck problems as the flow increases. At the same time, in 2019, the total heat demand was 21 008 MW. This is more than 5 % than in 2020, assuming 100 % of consumers connected. The reasons for this trend are: decreasing total housing area, no incentive for the buildings in newly built-up areas to be connected to the DH system, poor service motivating business facilities to disconnect from the system. When the primary energy consumption related to the warmer climate and behaviour of business sector decreases, the DH system requires renovation. It is possible to reduce network return temperature during some months of the year. The reason is that, a high temperature difference is essential to maintain high efficiency and minimize fuel and pumping cost, it also enables more customers to be connected to a DH system without increasing pipe dimensions of a network.
Highlights
Brange et al [1] mention return and supply temperatures as indicators of a district heating (DH) system performance
The suggested in [4] three-pipe option utilises one supply pipe and two return pipes, whereby one return pipe is in use when energy demand occurs, referred to as the delivery flow, while the other return pipe is in use when there is no energy demand, referred to as the recirculation flow
The supply and return temperatures in a DH system change according to the outdoor temperature, and because of wind, solar radiation, and behaviour of inhabitants using TRV valves
Summary
Brange et al [1] mention return and supply temperatures as indicators of a DH system performance. The suggested in [4] three-pipe option utilises one supply pipe and two return pipes, whereby one return pipe is in use when energy demand occurs, referred to as the delivery flow, while the other return pipe is in use when there is no energy demand, referred to as the recirculation flow The latter of these is mostly related to domestic hot water (DHW) usage profile, for example, inhabitants usually have a shower in the morning, before they go out. Noussan et al [10] detail the operation analysis of existing DH systems considering actual data and detailed time steps. To predict a value of thermal load, Geysen et al [24] establish feature set that considers timing data, temperature prediction, statistics on heat demands and control signals. Zarin Pass et al [3] input fixed heating and cooling supply temperatures and constant network temperatures, a more accurate analysis could be done
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