Optimal design of energy-flexible distributed energy systems and the impacts of energy storage specifications under evolving time-of-use tariff in cooling-dominated regions

Abstract

To utilize the energy flexibility of demand side participants for achieving the global carbon-neutrality target, distributed energy systems (DESs) with active energy storages have attracted increasing attention. Existing studies mainly address the optimal configuration of DESs for enhanced energy flexibility. But the impacts of the energy storage specifications for DESs are rarely investigated, particularly under the evolving electricity markets towards carbon neutrality. This study, therefore, investigates the optimal design of energy-flexible DESs in cooling-dominated regions and the impacts of the economic and technical parameters of active energy storages under the evolving ToU tariff. A two-stage optimization method is developed for the optimal design of energy-flexible DESs. A district in Hong Kong is chosen as a reference site to perform the design case studies and impact analysis. It is found that the ToU tariff has significant impacts on the optimal design of energy-flexible DESs. The increase of the peak-to-valley ratio generally can increase the life-cycle economic benefits of DES energy-flexibility investment. The annualized life cycle cost of the optimized energy-flexible DES is decreased by up to $ 0.31 million when the peak-to-valley ratio increases from 2 to 10. A high unit price of energy storages (i.e., higher than 210 $/kWh for electric energy storages and 60 $/kWh for cold energy storages) will make them not economical to be adopted under all ToU tariffs. The maximum discharging rate of cold storages and the four specification parameters (i.e., the maximum charging rate, maximum discharging rate, charging/discharging efficiency, and lower limit of state of charge) of electric energy storages have considerable impacts on the energy-flexible DES design, and therefore are recommended to be optimized in design.