Energy flexibility investigation of advanced grid-responsive energy control strategies with the static battery and electric vehicles: A case study of a high-rise office building in Hong Kong

The energy flexibility of the sophisticated building energy systems with the integration of renewable systems, diversified energy storages, advanced energy conversions and electric vehicles, has attracted increasing attention. However, there are limited studies on the energy flexibility quantification and enhancement of the sophisticated building energy systems. In this study, a nonlinear component-based model, integrating building integrated photovoltaics and vehicle integrated photovoltaics, was developed for the energy flexibility assessment. A generic methodology with a series of quantifiable energy flexibility indicators (the off-peak renewable-discharging ratio and the off-peak grid-discharging ratio) has been presented to quantify the energy flexibility of the hybrid grid-connected building vehicle system. Two dynamic advanced grid-responsive energy control strategies have been proposed for the energy flexibility enhancement. Techno-economic feasibility has been discussed regarding different off-peak electricity tariffs and different rated renewable capacities. Moreover, a technical solution is presented to solve the energy congestion contradiction regarding the exploitation of the off-peak grid electricity and the on-site renewable energy through electrical storage systems. The research results showed that the proposed renewable-to-demand and the off-peak grid-supported storage control (Control Strategy 3) shows the robustness and competitiveness, in terms of activating both the on-site renewable system and the grid to participate in the building energy system. By implementing the Control Strategy 3, 96.8% of the grid electricity can be shifted from the off-peak period to the peak period for the usage of the office building. Depending on the critical static battery capacity at 10 kWh for each floor, the energy congestion contradiction can be solved by managing the off-peak grid-battery charging power to minimise the energy-based operational cost. This study formulates a flexible energy management system and a flexible energy control strategy, which are important for the promotion of energy flexible buildings, with participation of both the policymakers and the householders.