Holistic analysis and optimization of distributed energy system considering different transport characteristics of multi-energy and component efficiency variation

Abstract

Different natures and nonlinear transport characteristics of electric, thermal and gas energies make it so complex for analyzing distributed energy system (DES). Many researches usually ignored nonlinear heat transfer equations of heat exchange devices and assumed constant efficiencies of energy conversion devices to construct a simplified electric-analogy model of DES. This contribution develops a heat current model of thermal system to consider heat transfer constraints and their influences on energy conversion efficiencies, applies a linearized DistFlow model to describe electric power flow in radial distribution power grid, and then offers a holistic multi-energy transport model of whole DES. On this basis, a hierarchical iteration method is developed for system operation optimization under different working conditions. Results show that the proposed method fully reflects the influences of energy transport constraints on efficiencies of energy conversion devices and further the optimal operation strategy of DES. Specifically, under the consideration of time-of-use electric tariff, the heat generation rate of heat pump has a considerable decrease at 4:00 compared with the results without considering efficiencies variations and power transmission constraints. Besides, the total released heat of heat storage device from 10:00 to 18:00 has a 36.53% reduction if ignoring solar collector efficiency variations.