Abstract
The urban territory is responsible for a high percentage depletion of natural resources and producing waste. As the global population grows and cities expand, the demand for energy also climbs higher. Consequently, efficient energy usage is becoming more and more crucial in order to support both local and global sustainability. To achieve such a goal, the reduction of energy demand, the optimization of energy supply sources, and the increase of renewable energy share can facilitate the transition of urban areas into highly efficient and sustainable districts. Building energy efficiency is an essential element in every national policy to achieve long-term energy and sustainability goals. Although nearly-Zero Energy Buildings are now a standard for new constructions in several European Union Member States, the real challenge for a decarbonized society relies in the renovation of the existing building stock. Specifically, the choice of energy efficiency measures to apply in retrofitting interventions represents a significant step, which can have implications also on building life cycle environmental impacts and economic sustainability. Even if the literature has plenty of examples of coupling building energy simulation with multi objective optimization techniques for the identification of the best energy efficiency measures, the adoption of such approaches for district and urban scale simulation is still limited, often because of lack of complete data inputs and high computational requirements.
The approach suggested in this study is based on the coupling of Urban Scale Energy Modelling simulations and multi-objective optimization techniques performed considering an archetype-based simplified physical modelling of the overall urban heterogeneity, to evaluate the annual district energy uses and define possible efficiency measures considering three objectives – i.e., energy efficiency, economic performance, and environmental sustainability. The application to a real case study indicates that the proposed approach can be successfully implemented to renovate an existing built environment and it can be adopted to support the decision makers in the development of efficient strategies to apply at city or district scale. Achievable energy savings are analyzed and the most significant factors affecting the overall performance identified. As regards the investigated case study, the results show that climate change can have a significant impact on the energy performance of buildings and although each energy efficiency measure can improve the district energy performance with savings ranging from 29 % to 46 % of the 2015 baseline value (98 kWh m2 a-1 ), the proposed solutions are not sufficient to achieve 2050 carbon neutrality goals without intervention on the system. Furthermore, public subsidies have been found to be necessary, as none of the proposed solutions are capable of recouping the initial investments for this case study.