Coupling potential-forced network flow analysis based on potential energy conservation rules and network flow method

Abstract

An integrated energy system that uses various networks to transfer electrical power, natural gas, heating, and cooling energy has been applied widely in recent decades. Heating energy flow is a typical coupling network flow consisting of pressure flow and thermal energy flow. It will be attractive to develop a similar network flow method for analyzing the general energy networks, including coupling network flows. In this work, two thermodynamic state properties in the energy networking transmission process, pressure, and temperature are proved as fundamental physical potentials in the network transmission process. It is found that the potential energy is conserved at the mixing node, and the generic network flow can be classified as fundamental potential-forced network flows or decoupled as the combination of potential-forced network flows. By comparing the transmission speed differences between different potentials, the unilateral continuity problem is found in the coupling network flows. The directional nodal potential method (DNPM) for modeling potential-forced network flows that capture the physical characteristics of pipeline transmission and nodal mixing for networking transmission is developed. The results show that the DNPM can unify modeling and analyzing all 3 types of typical potential-forced network flows, then directly obtain the state properties at the mixing nodal. These are instantiated in analyzing districted thermal energy networks. The case study on district heating networks shows that the unilateral continuity problem at the mixing node for coupling network flows can be well solved. The number of equations of the presented DNPM is 7 less than the traditional BFM, and 3 iterations less than BFM, which show the ability of effective formulation and solution. The present work gives researchers an efficient method of formulating, analyzing, and optimizing energy networks.