A new hydraulic regulation method on district heating system with distributed variable-speed pumps

Abstract Compared with the hydraulic configuration based on the conventional central circulating pump, a district heating system with distributed variable-speed-pumps configuration can often save 30–50% power consumption on circulating pumps with frequency inverters. However, the hydraulic regulations on distributed variable-speed-pumps configuration could be more complicated than ever while all distributed pumps need to be adjusted to their designated flow rates. Especially in a multi-source looped structure heating network where the distributed pumps have strongly coupled and severe non-linear hydraulic connections with each other, it would be rather difficult to maintain the hydraulic balance during the regulations. In this paper, with the help of the advanced automation and information technologies, a new hydraulic regulation method was proposed to achieve on-site hydraulic balance for the district heating systems with distributed variable-speed-pumps configuration. The proposed method was comprised of a new hydraulic model, which was developed to adapt the distributed variable-speed-pumps configuration, and a calibration model with genetic algorithm. By carrying out the proposed method step by step, the flow rates of all distributed pumps can be progressively adjusted to their designated values. A hypothetic district heating system with 2 heat sources and 10 substations was taken as a case study to illustrate the feasibility of the proposed method. Two scenarios were investigated respectively. In Scenario I, the flow rate of one substation varied according to its heat demand and the flow rates of other substations maintained their original values. And in Scenario II, the flow rates of all substations varied synchronously with the same relative rate. The results of the both scenarios indicated that all pumps could be properly adjusted to their designated flow rates by the proposed method with a high frequency adjustment resolution as 0.001 Hz. In scenario I, compared with the district heating system with distributed variable-speed-pumps configuration, the power consumption would be 26.6–66.8% less than that of the conventional central circulating pump configuration during the 4 rounds of regulations. In scenario II, the energy saving ratio of the district system with distributed variable-speed-pumps configuration would be 36.1–90.3% less than that of the conventional central circulating pump configuration during the 5 rounds of regulations.

[1]  Jianjun Xia,et al.  Case study on industrial surplus heat of steel plants for district heating in Northern China , 2016 .

[2]  Thorsten Urbaneck,et al.  Dynamic thermo-hydraulic model of district cooling networks , 2016 .

[3]  F. Haghighat,et al.  Integration of storage and renewable energy into district heating systems: A review of modelling and optimization , 2016 .

[4]  Asim Imdad Wagan,et al.  A new explicit approximation to Colebrook’s friction factor in rough pipes under highly turbulent cases , 2015 .

[5]  Andrea Toffolo,et al.  Simulation and analysis of a meshed district heating network , 2016 .

[6]  U. Persson,et al.  Heat distribution and the future competitiveness of district heating , 2011 .

[7]  Zoran Kapelan,et al.  Quo vadis water distribution model calibration? , 2009 .

[8]  B. Möller,et al.  GIS based analysis of future district heating potential in Denmark , 2012 .

[9]  Zheng Xuejing,et al.  A survey of district heating systems in the heating regions of northern China , 2014 .

[10]  Bernd Möller,et al.  Conversion of individual natural gas to district heating: Geographical studies of supply costs and consequences for the Danish energy system , 2010 .

[11]  Risto Lahdelma,et al.  State estimation of district heating network based on customer measurements , 2014 .

[12]  Lin Duanmu,et al.  Electricity consumption and economic analyses of district heating system with distributed variable speed pumps , 2016 .

[13]  Jianing Zhao,et al.  A method for the steady-state thermal simulation of district heating systems and model parameters calibration , 2016 .

[14]  Pramod R. Bhave.  Calibrating Water Distribution Network Models , 1988 .

[15]  Jan Dahl,et al.  A method for the simulation and optimization of district heating systems with meshed networks , 2015 .

[16]  Brian Vad Mathiesen,et al.  The role of district heating in future renewable energy systems , 2010 .

[17]  Ralf-Roman Schmidt,et al.  Low temperature district heating in Austria: Energetic, ecologic and economic comparison of four case studies , 2016 .

[18]  Xia Chen,et al.  Energy saving and emission reduction of China's urban district heating , 2013 .

[19]  Duanmu Lin,et al.  Energy saving analyses on the reconstruction project in district heating system with distributed variable speed pumps , 2016 .

[20]  H. Ravn,et al.  The role of district heating in the future Danish energy system , 2012 .

[21]  W. Cai,et al.  China building energy consumption: Situation, challenges and corresponding measures , 2009 .

[22]  M. Lampinen,et al.  Energy efficiency improvements utilising mass flow control and a ring topology in a district heating network , 2014 .

[23]  Svend Svendsen,et al.  Renewable-based low-temperature district heating for existing buildings in various stages of refurbishment , 2013 .

[24]  Guoqiang Zhang,et al.  Diameter optimization of district heating and cooling piping network based on hourly load , 2016 .

[25]  Srinivasa Lingireddy,et al.  Hydraulic Network Calibration Using Genetic Optimization , 2002 .

[26]  Li Yang,et al.  Building energy efficiency in China rural areas: Situation, drawbacks, challenges, corresponding measures and policies , 2014 .

[27]  Lisa Branchini,et al.  District Heating Network Design and Analysis , 2014 .

[28]  Jun Zhao,et al.  Hydraulic performance of a new district heating systems with distributed variable speed pumps , 2013 .

[29]  Enrique Rosales-Asensio,et al.  District heating and cogeneration in the EU-28: Current situation, potential and proposed energy strategy for its generalisation , 2016 .

[30]  Patrick Lauenburg,et al.  Prosumers in district heating networks – A Swedish case study , 2016 .

[31]  Brian Vad Mathiesen,et al.  4th Generation District Heating (4GDH) Integrating smart thermal grids into future sustainable energy systems , 2014 .

[32]  Ioan Sarbu,et al.  Energy Savings Potential for Pumping Water in District Heating Stations , 2015 .

[33]  Peng Wang,et al.  Energy-consumption and economic analysis of group and building substation systems : a case study of the reformation of the district heating system in China , 2016 .

[34]  Zhenqing Sun,et al.  China's energy development strategy under the low-carbon economy , 2010 .