Thermodynamic analysis of electric to thermal heating pathways coupled with thermal energy storage

Abstract

The intricate energy conversion involving thermal energy introduces complexities in assessing, analyzing, and optimizing such systems. Recognizing the paramount role of thermal energy in overall energy consumption, there arises an imminent necessity to identify and implement thermodynamically efficient electric to thermal heating pathways. This study delves into the attributes and applicability of different thermodynamic evaluation methods. Through a combination of theoretical elucidation and case-based comparisons, comprehensive thermodynamic assessments on three distinct electric heating options are performed, including electric heaters integrated with user-end thermal energy storage, heat pumps integrated with user-end thermal energy storage, and two-stage compression heat pumps paired with intermediate thermal energy storage. Our findings reveal that two-stage compression heat pumps paired with intermediate thermal energy storage exhibit heightened energy conversion efficiency, exergy efficiency, and diminished entransy dissipation. Notably, greater temperature differences between ambient and heat supply temperatures contribute substantively to the realization of both thermodynamic and economic advantages along this pathway. Considering the time-sharing tariff, optimal economic outcomes are observed for Shanghai electric bills when the intermediate thermal energy storage output temperature is maintained at 15 °C. Leveraging intermediate storage temperatures for thermal energy storage enables both heat storage during winter and cold storage during summer.