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

• Published in: Energy and buildings 2023-09, Vol.294, p.113213, Article 113213
• Main Authors: Álvarez Flórez, Laura, Péan, Thibault, Salom, Jaume
• Format: Article
• Language: English
• Subjects: Carbon emissions; Demand response mechanisms; Energy flexibility in buildings; Hourly conversion factors; Household energy consumption; Primary energy use
• ISSN: 0378-7788
• DOI: 10.1016/j.enbuild.2023.113213

•Hourly-based methods help assess the carbon footprint and primary energy use of buildings.•Time-varying signals are compared with constant factors from national standards.•National standards overestimate grid emissions by 50% and primary energy by 20%•Hourly assessment methods more relevant in COVID19 pandemic or extreme weather.•Energy flexibility is activated based on accurate hourly emissions, price or primary energy. 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 de