Waste-to-energy (W2E) for renewable-battery-FCEV-building multi-energy systems with combined thermal/power, absorption chiller and demand-side flexibility in subtropical climates

Abstract

Fuel Cell Electric Vehicle (FCEV) cogeneration powered by hydrogen can provide demand-side flexibility, and mitigate grid reliance of district buildings. Nevertheless, optimal configuration and high-efficient operation of the cogenerated FCEV-building system considering load characteristics have not been studied. In this study, a general approach with optimal system configurations and control strategies on an integrated FCEV-based cogeneration system is proposed for techno-economic performance improvement. A transient system model is developed with a state-of-the-art fuel cell degradation model on the latest automotive fuel cell techniques to characterize both power and thermal efficiency change with fuel cell decaying. Considering the dominant impact of large load changes on fuel cell degradation in FCEV's dual functions (Vehicle-to-Building (V2B) interaction and transportation), an innovative synergistic control strategy with fixed operating power is specially designed to mitigate fuel cell degradation and prolong its service lifetime. Results showed that energy flexibility can be improved by the optimal system configurations and the proposed control strategies (e.g., compared to the traditional system, the FCEV-based combined cooling, heating, and power (CCHP) systems can improve the on-site electrical energy fraction from 33.26% to 61.90%, and the off-peak grid shifted ratio from 33.71% to 53.60%, respectively), together with the decrease in operating costs between 4.49 and 6.87 CNY/m2·a. Sensitivity analysis results indicate that, the CCHP systems will be economically feasible for office buildings when the hydrogen price and the absorption chiller initial costs fall below 26.1 CNY/kg and 7900 CNY/kW. Moreover, regarding the dynamic degradation of fuel cells under large-range load change cycling, start-stop cycling, idling condition, and maximum power condition, the proposed mitigation strategy can effectively reduce the average FCEV degradation rates per unit power by 17.80%, compared to the strategy with dynamic operating power. This research provides a comprehensive methodology to evaluate the impact of system configurations and control strategies to improve energy efficiency, energy flexibility, and economic performance, and reduce FCEV degradation, together with carbon footprint analysis of hydrogen economy, accelerating carbon neutrality with advanced H2 techniques and sustainable buildings.