Quantification of energy flexibility of residential net-zero-energy buildings involved with dynamic operations of hybrid energy storages and diversified energy conversion strategies

For immediate response and sufficient reaction to building energy demands by avoiding excessive production, increasing stability of energy networks, and minimising energy congestion, building energy flexibility has potentials to enhance the resilience of hybrid grids to fluctuations in energy demands of multi-energy systems. However, few studies focused on dealing with the complexity of energy flexibility quantification regarding diversified energy conversions and hybrid energy storages. Moreover, few studies focused on the exploitation of energy potential provided by building energy systems itself through flexible energy control strategy. In this study, a generic methodology was proposed to characterise energy flexibility of diversified energy systems. A series of new flexibility indicators are proposed such as flexible power, flexible electricity, on-site flexible electric load fraction, on-site flexible surplus renewable fraction ratio, and flexibility factors. Technical solutions are proposed to improve the energy flexibility using integrated solutions of energy conversion, energy storage, and rule-based control strategies. Case studies with different control strategies (i.e. "battery-to-demand control strategy" and "renewable-to-demand control strategy") are studied for the technical viability assessment. This study provides a generic methodology to characterise the energy flexibility regarding sophisticated building energy systems, and a rule-based control strategy for the flexibility enhancement, which will be effective in the promotion of energy flexible buildings.