Assessing the energy flexibility of building clusters under different forcing factors

Given the increasing penetration of variable renewable resources in energy networks, future buildings should become flexible, i.e., able to modify their energy demands in response to external forcing factors to pursue specific goals. Furthermore, strong interaction among interconnected prosumer buildings and energy systems will require flexible energy management strategies at cluster level. Accordingly, this study implements the IEA EBC Annex 67 approach and proposes a quantification methodology to assess the energy flexibility performance of building clusters. The availability of renewable energy sources and carbon intensity in the energy mix are selected as forcing factors and a rule-based control scheme is applied to the space heating set-point to exploit thermal storage in the building structure. Specific indicators are defined to quantify flexibility as (i) a reduction in energy demand not covered by renewables or (ii) a percentage decrease in carbon emissions enabled by smart control of the cluster, compared to a reference scenario. The methodology is applied to four cluster configurations characterized by different building thermal mass levels, modeled in Dymola dynamic simulation environment. Results show that smart operation for simulated clusters enables an improvement of renewable energy usage (up to a 13% saving of the residual annual heating demand), and up to an 18% reduction of energy-related carbon emissions. The suggested quantitative assessment and indicators represent valuable support for building designers to easily compare multiple technological solutions and design strategies in terms of energy flexibility.