The power grid defines one of the most important technological networks of our times and sustains our complex society. It has evolved for more than a century into an extremely huge and seemingly robust and well understood system. But it becomes extremely fragile as well, when unexpected, usually minimal, failures turn into unknown dynamical behaviours leading, for example, to sudden and massive blackouts. Here we explore the fragility of the European power grid under the effect of selective node removal. A mean field analysis of fragility against attacks is presented together with the observed patterns. Deviations from the theoretical conditions for network percolation ͑and fragmentation͒ under attacks are analysed and correlated with non topological reliability measures.

We present an analysis of the topological structure and static tolerance to errors and attacks of the September 2003 actualization of the Union for the Coordination of Transport of Electricity (UCTE) power grid, involving thirty-three different networks. Though every power grid studied has exponential degree distribution and most of them lack typical small-world topology, they display patterns of reaction to node loss similar to those observed in scale-free networks. We have found that the node removal behaviour can be logarithmically related to the power grid size. This logarithmic behaviour would suggest that, though size favours fragility, growth can reduce it. We conclude that, with the ever-growing demand for power and reliability, actual planning strategies to increase transmission systems would have to take into account this relative increase in vulnerability with size, in order facilitate and improve the power grid design and functioning.2

Sustainability issues, as unwanted results of not fully respecting natural cycles, are widely recognized as wicked problems, which should not be thought of as problems to be solved, but rather as "conditions" to be managed, as if they were a chronic disease (Seager et al., 2011). There exists a general agreement on the need to reform scientific expertise by developing new ways of knowledge production and decision-making able to cope with the challenges sustainability poses. In this sense, transdisciplinary aspects of sustainability are acknowledged as a transformational stream of sustainability science.Transdisciplinarity is considered a competence for sustainability in technological curriculums. Nevertheless, engineering education professionals tread on unfamiliar ground when entering transdisciplinarity approach, as it includes social sciences and humanities perspectives. Advancing sustainable engineering science requires creating new long-term, participatory, solution-oriented programs as platforms to recognize and engage with the macro-ethical, adaptive and cross-disciplinary challenges embedded in professional issues.Meanwhile, individual university professors and researchers take a step forward to try out innovative experiences in their classrooms to deal with complexity and reach holism in fostering knowledge in different ways. This paper analyses first what is being done and how is it being focused, and second, What are the strategies for and purposes of implementing transdisciplinary experiences in engineering higher education.Assuming that distinct patterns of definition of transdisciplinary exists, the authors collated transdisciplinary initiatives in engineering education for sustainability from Thompson Klein (2014) discourses on transdisciplinarity: transcendence, problem solving and transgression. They also explored how practical constraints imposed by a classroom context, highlighted the limits of transdisciplinarity, and offered suggestions on improvements, which could be implemented. Balsiger (2014) proposes four varieties of transdisciplinarity (soft, hard, inclusive and reflexive) to identify ways for moving from one type to another as circumstances change, in terms of stakeholder's collaboration and knowledge integration possibilities.The methodology consisted in literature review of articles published in relevant journals in the field of sustainability, which focussed on transdisciplinarity approaches in engineering education. We have analysed how the different initiatives fit in Klein's discourses on ACCEPTED MANUSCRIPT transdisciplinarity. Moreover, an affinity analysis has been performed to cluster transdisciplinarity initiatives in engineering education for sustainability in homogeneous groups. Finally, in the varieties of transdisciplinarity framework, the experiences identified when reviewing the literature have been spread over the range among Balsiger's taxonomy.The investigation indicates that most transdisciplinary initiatives in technological education for sustainability ...

Reliability assessment is crucial when dealing with complex systems, especially complex networks. Be they natural or man made, networks are able to sustain their functioning by means of a reliable set of components. The many functions a network can sustain are direct consequence of the topological structure that constraints and, at the same time, defines, the dynamical relation between its components. Therefore, some kind of relation between structure and dynamics should be expected to appear. In this paper, some of these relations that have been found for the European power grid are presented. Evidences for a critical relation between topology and dynamics are summarized, using some basic topological measures widely used in the developing complex networks paradigm. Finally, strategies for optimal management and operation of such networks are suggested.

Power grids are prone to failure. Time series of reliability measures such as total power loss or energy not supplied can give significant account of the underlying dynamical behavior of these systems, specially when the resulting probability distributions present remarkable features such as an algebraic tail, usually considered the footprint of self-organization and the existence of critical points. In this paper, 7 years (from 2002 to 2008) of Europe’s transport of electricity network failure events have been analyzed and the best fit for this empirical data probability distribution is presented. With the actual span of available data and although there exists a moderate support for the power-law model, the relatively small amount of events contained in the function’s tail suggests that causal factors other than self-organization or a critical state might be significantly ruling these systems’ dynamics.Peer ReviewedPostprint (author’s final draft

Abstract:Winter tourism is the main source of income and the driving force of local development in many mountain areas. However, in recent years the industry has been identified as being extremely vulnerable to future climate change. Although the Pyrenees has the largest ski area in Europe after the Alps, there are few detailed climate-change vulnerability assessments on the ski resorts based in this region. This paper analyzes the vulnerability of the Pyrenean ski resorts to projected changes in the snowpack under various future climate scenarios. In addition, the study analyzes the sustainability of the snowmaking systems to offset the climate variability of natural snow cover. On average, the study predicts a shorter ski-season length, especially in low-altitude ski resorts in a moderate climate-change scenario and for all ski resorts in a more intensive climatechange scenario. However, a significant regional variability has been identified for the projected impacts at very short geographical distances within the studied area.Moreover, this paper shows that snowmaking cannot completely solve the problem for all ski resorts in the Pyrenees, as the measure can only act as a robust adaptation strategy in the region provided climate change is limited to +2 °C snowmaking.

Mountain regions have been identi fied asespecially vulnerable areas to climate change. Changes in snowfall, glacier retreat and shifts in biodiversity amount and distribution are some examples of the sensitivity of mountain ecosystems. Moreover, in many mountain economies, reliable snow cover plays a key role as an important resource for the winter tourism industry, the main income source and driving force of local development in such regions. This study presents a georeferenced agent-based model to analyze the climate change impacts on the ski industry in Andorra and the effect of snowmaking as future adaptation strategy. The present study is the first attempt to analyze the ski industry in the Pyrenees region and will contribute to a better understanding of the vulnerability of Andorran ski resorts and the suitability of snowmaking as potential adaptation strategy to climate change. This study projects a reduction on the ski season length and the drop of the number of skiers especially in the lowest elevation ski resort of this region. Moreover, this work indicates that snowmaking cannot completely solve the problem of ensuring snow cover at low elevation ski resorts and should be considered as a suitable short-term strategy, but not as a sustainable long-term adaptation strategy. The resulting model can be used as a planning support tool to help local stakeholders understand the vulnerability and potential impacts of climate change and in the decision-making process of designing and developing appropriate sustainable adaptation strategies to future climate variability.

This paper analyses transport energy consumption of conventional and electric vehicles in mountainous roads. A standard round trip in Andorra has been modelled in order to characterise vehicle dynamics in hilly regions. Two conventional diesel vehicles and their electric-equivalent models have been simulated and their performances have been compared. Six scenarios have been simulated to study the effects of factors such as orography, traffic congestion and driving style. The European fuel consumption and emissions test and Artemis urban driving cycles, representative of European driving cycles, have also been included in the comparative analysis. The results show that road grade has a major impact on fuel economy, although it affects consumption in different levels depending on the technology analysed. Electric vehicles are less affected by this factor as opposed to conventional vehicles, increasing the potential energy savings in a hypothetical electrification of the car fleet. However, electric vehicle range in mountainous terrains is lower compared to that estimated by manufacturers, a fact that could adversely affect a massive adoption of electric cars in the short term.