A thermal-electrical analogy transient model of district heating pipelines for integrated analysis of thermal and power systems

Abstract

District heating networks have an ability to store heat to improve the flexibility of power systems, but it lacks a compatible method to analyze thermal and power system together. Based on the thermal-electric analogy method and inspired by the electromagnetic transient analysis approaches, this paper develops a thermal-electrical analogy transient model for district heating pipelines (DHPs), which offers the matrix formulas to describe the variations of fluid temperature and stored heat with time in the pipelines, instead of the traditional partial differential equations. For a heating pipe with the length 20 km, applying the thermal-electrical analogy transient model gives the variations of the outlet temperatures and the stored heat of the pipe under step, periodic and sinusoidal inlet temperatures, where the outlet temperatures keep unchanged before 300 min due to time delay. From 300 to 380 min, the outlet temperature rises to approach the inlet temperatures, i.e. the thermal non-regular regime, but 1 °C lower due to heat loss. After 380 min, they vary in the same trend as the inlet temperatures, i.e. the thermal regular regime, but have 380 min delay. Besides, the heat stored in the pipe and its variation frequency depend on the amplitude and phase differences of inlet and outlet temperatures.