Journal article

City Energy Analyst (CEA): Integrated framework for analysis and optimization of building energy systems in neighborhoods and city districts

This paper describes the City Energy Analyst (CEA), a computational framework for the analysis and optimization of energy systems in neighborhoods and city districts. The framework allows analyzing the energy, carbon and financial benefits of multiple urban design scenarios in conjunction to optimal schemes of distributed generation. For this, the framework integrates time-dependent methods for building energy performance simulation, conversion and storage technologies simulation, assessment of local energy potentials, bi-level energy systems optimization and multi-criteria analysis. Based on past research, the framework introduces a novel interface to facilitate the spatiotemporal analysis of patterns of demand and potential infrastructure solutions. The model was programmed in Python v2.7 and built as an extension of the Geographic Information System ArcGIS v10.3, which serves as a platform for the allocation and future dissemination of spatiotemporal data. We present an application of the model for a downtown area in Switzerland where we evaluated four trajectories of development and found optimum infrastructure solutions for their operation. For a more holistic approach we used the 2000-W/1-t CO2 society vision concept to compare the environmental performance of these solutions with that of embodied energy in buildings and transportation systems. From the optimization process, most infrastructure solutions showed an average integration of 50% to 80% of buildings in thermal micro-grids, 50 to 100% of the available solar potential, and a resource mix consisting of photovoltaic electricity and sources of waste and ambient heat. For a balanced distribution of social, environmental and economic criteria, the results showed potential relative savings in the area from 45% to 60% in emissions and from 25% to 50% in primary energy at an annualized cost between 14% and 44% higher than today. For an-economic-driven distribution, the results showed savings of up to 23% in emissions, 36% in primary energy and 11% in costs. We identified close to 15% in emissions and 20% in primary energy savings with variable costs between -2% and 23% in the area are strongly related to the urban design option rather than to its optimal energy system. In comparison to local benchmarks, the environmental impact of buildings during operation lies between that of embodied energy in buildings and mobility in the service sector (business flights). We estimated that an increase in close to 4% of today's average efficiency of photovoltaic technology would allow the area to comply with those local benchmarks. On the other hand, we concluded the suitability of the City Energy Analyst (CEA) to assist urban planning authorities looking for both design and engineering options to increase the performance of their neighborhoods and city districts. (C) 2015 Elsevier B.V. All rights reserved.


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