sustainability Review The Role of Renewable Energy in the Promotion of Circular Urban Metabolism Antonio Barragán-Escandón 1,* ID , Julio Terrados-Cepeda 2 and Esteban Zalamea-León 3 ID 1 Department of Electrical Engineering, Universidad Politécnica Salesiana, Calle Vieja 12-30 y Elia Liut, Cuenca 010102, Ecuador 2 Department of Graphic Engineering, Design and Projects, Universidad de Jaén, 23071 Jaén, Spain;
[email protected] 3 Facultad de Arquitectura y Urbanismo, Universidad de Cuenca, Cuenca 010103, Ecuador;
[email protected] * Correspondence:
[email protected]; Tel.: +593-9-90017601 Received: 28 October 2017; Accepted: 12 December 2017; Published: 15 December 2017 Abstract: Cities are human creations requiring large amounts of materials and energy. Constant consumption of resources exerts pressure on the environment not only due to its exploitation, but also because once processed, the resources produce waste, emissions or effluents. Cities are responsible for more than three quarters of the emissions of greenhouse gases. It is anticipated that the urban population will increase by up to 80% by the mid-21st century, which will make the current energy model unsustainable, as it is based on the intensive use of fossil resources. A change in urban planning is required to meet the energy requirements of cities. Several studies mention that renewable energy must be used in cities, but they do not identify the resources and technologies that can be used to promote circular urban metabolism. A review of the literature establishes that there are eleven renewable technologies with different degrees of maturity that could reduce the import of energy resources, which would contribute to changing the metabolic linear model into a circular model.