Flexibility categorization, sources, capabilities and technologies for energy-flexible and grid-responsive buildings: State-of-the-art and future perspective

The rapid development of remote telemetry, control and communication technologies in smart grids enables the demand side to provide energy flexibility for power grid economy and reliability. The building sector, as a consumer of large amounts of electricity, has various flexible loads that can be effectively utilized for such purposes if buildings and their energy systems are under proper design and control. In this paper, a systematic methodology is proposed for categorizing the building energy flexibility according to different power grid requirements. Considering the requirements of response duration, response direction and response speed (within seconds, minutes, or even longer timescale), the flexibility can be categorized as fast regulation, moderate regulation, load shedding, load shifting and load covering. A comprehensive review is presented to summarize and compare various flexibility sources, their characteristics and capabilities in buildings for providing those five different types of energy flexibility. The analysis of available information technologies and business development indicate great capability and potential of buildings to participate in energy flexibility markets as a practical demand side management instrument. Three major limitations in existing research and energy markets are identified as the major challenges for the future development of energy flexible buildings.