How environmental and energy issues shape the cities: a case-study in Barcelona, Spain

In a time of transformation and discussion on energy issues, the one-to-one relationship between city and energy sources of supply prompts to go over city morphology according to new renewable energy sources and technologies. The urgency of this action is motivated by the current energy-intensive condition of our settlements, accused to be the “black holes” (F. Butera, 2008) in global energy consumption accounting for more than 75% of total amount and 85% of polluting emissions. A figure doomed to grow, according to United Nation evaluations, due to the continuous process of world metropolitanization which will lead more than 80% of world population to choose urban living. Thanks to the evidences in the history of the cities, it is possible to demonstrate as urban form is tightly reliant on energy source typology and its availability on territory and, mainly, as it changes as a consequence of their development and decline. The relationships between Coketown and coke, vertical-city and electricity or horizontal-city (sprawl) and oil, give us a clear example. The obliged transition toward new renewable sources makes us wonder on future settlement morphology, especially on possibility to use the urban design as ideal tool to reach new urban models. More specifically, in which direction goes the historic debate on contemporary cities evolving, in this age of climate change and sustainability? What about incorporation of renewable energies and, in particular, exploitation of solar energy in urban settlements? To date, researches mainly focus on urban density, while less attention has been paid to the form that means to the “physical qualities” of the spatial structure of the city; actually, the organization of the urban fabric in its 3 dimensions is strictly related to the potential gains of solar energy and therefore to the individual, technical and social use of the sun. By studying an existing urban sample, this work aims at investigating the extent to which the morphological features of the fabric can affect the collection of solar radiation on the buildings envelope and public spaces, in order to define general guidelines aiding architects already in the early phases of masterplan and urban design. In the specific study case of Eixample district by I. Cerdà in Barcelona (Spain) the attention is focused on the network orientation and on the height to width ratio, which are analysed in order to evaluate and compare the influence of obstructions and the distribution of solar flux. This study is developed by applying a simplified comparative methodology supported by HELIODON 2, a simulation software that has not a realistic and diagnostic aim, but allows fast interaction between solar radiation and design process. Through this work, we intend to propose a more “architectural” approach as well as to provide a new methodological and operational tool for solar analysis and at urban scale.