Hourly based methods to assess carbon footprint flexibility and primary energy use in decarbonized buildings

Constant emission factors to assess the carbon footprint of buildings energy use, as usually included in national Building Technical Codes, show their limitations since the electrical grid mix changes constantly. For this reason, hourly-based methods using time-varying penalty signals to calculate carbon emissions and primary energy use in buildings constitute more effective assessment methods, especially with the aim to activate energy flexibility in buildings based on those inputs. Such signals have been developed and tested in the present work. The robustness and effectiveness of the methods is tested throughout two study cases. The first case compares the impact of using hourly signals over constant factors from the standards. For that purpose, a measured aggregated consumption profile corresponding to 226 real households is analyzed. In the second study case, demand response is implemented through control strategies reacting to the hourly penalty signals, aiming to decrease the emissions, primary energy use and cost. Results for the first case reveal that hourly rates better capture the variability of the electric grid compared to constant yearly factors from national standards, with a 50% difference in carbon emissions and a 20% overestimation with primary energy. Results from the second study case show how the implemented modulation strategies offer benefits in the flexible scenarios compared to the base scenarios, in terms of accumulated emissions or primary energy. Improvements are especially perceived when splitting data seasonally and considering periods with higher demand. Furthermore, this study provides insights for developing energy flexibility inputs when assessing the building performance during critical events such as the COVID19 pandemic or extreme weather conditions, where hourly and seasonal variation might have greater impact. Demand response mechanisms as energy flexibility strategies studied through this work might help in the reduction of total emissions and primary energy. Depending if the goal is to shift the demand due to environmental or economical reasons, different modulation strategies can be implemented to reach greater benefits.