Uncertainties in smart grids behavior and modeling: What are the risks and vulnerabilities? How to analyze them? Enrico Zio a,b,n , Terje Aven c a Ecole Centrale Paris – Supelec, Paris, France b Politecnico di Milano, Milano, Italy c University of Stavanger, Stavanger, Norway article info Article history: Received 11 December 2010 Accepted 14 July 2011 Available online 6 August 2011 Keywords: Smart grids Uncertainty Risk abstract This paper looks into the future world of smart grids from a rather different perspective than usual: that of uncertainties and the related risks and vulnerabilities. An analysis of the foreseen constituents of smart grids and of the technological, operational, economical and policy-driven challenges is carried out to identify and characterize the related uncertainties and associated risks and vulnerabilities. The focus is on the challenges posed to the representation and treatment of uncertainties in the performance assessment of such systems, given their complexity and high-level of integration of novel technologies. A general framework of analysis is proposed. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction In today’s World, a number of critical infrastructures have become fundamental to national and international social devel- opment, economy, quality of life and security. The energy trans- mission and distribution network, the telecommunication network, the transportation system are common representative examples. Their high degree of inter- and intra-connectedness makes them quite vulnerable to global disruption, when exposed to hazards of various nature, from random mechanical/physical/ material failures to natural events, intentional malevolent attacks, human errors. This broader spectrum of hazards and threats, calls for an all-hazards approach for the understanding of the failure behavior of such systems, in view of their consequent protection. One associated underlying motif is the complexity of these systems and the related emergent behaviors, which may arise in collective ways difficult to predict from the superposition of the behavior of the individual elements of the system. This complex, emergent behavior has been demonstrated by system breakdowns often triggered by small perturbations followed by accelerating cascades and large-scale, border-crossing consequences, stressing the importance of (inter)dependencies. This leads to the fact that the analysis of these systems cannot be carried out with classical analytical methods of system decomposition and logic analysis; a framework is needed to integrate a number of methods capable of viewing the problem from different perspectives (topological and functional, static and dynamic, etc.). The focus of this paper is on the networks for energy supply (the so-called electric power grids), and its foreseen future ‘‘smart’’ development in response to the challenges ahead. These systems are pervasive in our everyday’s life as they reach virtually every home, school, hospital, office, factory and institution in developed countries and are quickly penetrating in developing ones. They are made of a large number of interconnected elements (wires and machines), which link the electricity gen- erators to the customers, for satisfaction of their diverse needs. Originally developed as loosely interconnected networks of local systems, electric power grids have extended on large scales, across regional and national boundaries. Recently, distributed resources, mostly small power generators, are being increasingly connected to the existing backbone. The extent of the intercon- nectedness, the number and variety of power sources and gen- erators, of controls and loads make electric power grids among the most complex engineered systems. Another relevant complexity attribute relates to the increased integration of the electrical power grid with other critical infra- structures, e.g. driven by the pervasive use of computer-based communication and control systems, which is beneficial in many respects but on the other hand it introduces additional vulner- abilities due to the increased interdependence, which can lead to surprising behaviors in response to perturbations. The re-concep- tualization of the electric power grid to allow for the integration of large shares of electricity produced by harvesting solar and wind energies at the most suitable sites (e.g. desert solar and offshore wind farms) calls for a ‘‘smarter’’ system with decentralized Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/enpol Energy Policy 0301-4215/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.enpol.2011.07.030 n Corresponding author at: Ecole Centrale Paris – Supelec, Paris, France, and Politecnico di Milano, Italy. E-mail addresses: enrico.zio@ecp.fr, enrico.zio@supelec.fr, enrico.zio@polimi.it (E. Zio), terje.aven@uis.no (T. Aven). Energy Policy 39 (2011) 6308–6320