At a global level, the need for energy efficiency and an increased share of renewable energy sources is evident, as is the crucial role of cities due to the rapid urbanization rate. As a consequence of this, the research work related to Positive Energy Districts (PED) has accelerated in recent years. A common shared definition, as well as technological approaches or methodological issues related to PEDs are still unclear in this development and a global scientific discussion is needed. The International Energy Agency’s Energy in Buildings and Communities Programme (IEA EBC) Annex 83 is the main platform for this international scientific debate and research. This paper describes the challenges of PEDs and the issues that are open for discussions and how the Annex 83 is planned and organized to facilitate this and to actively steer the development of PEDs major leaps forward. The main topics of discussion in the PED context are the role and importance of definitions of PEDs, virtual and geographical boundaries in PEDs, the role of different stakeholders, evaluation approaches, and the learnings of realized PED projects.

Transport accounts for 31% of Swiss green house gas emissions due to the high degree of oil dependence in transport energy supply. The emissions of transport could be reduced significantly if all the vehicles that ran on fossil fuels would be replaced by electric vehicles powered by photovoltaic solar energy. Compared with other sources of renewable transport energy, photovoltaic generation of electricity has two advantages: it requires little space and can also be applied to built-up areas or transport infrastructure. In this paper, we will examine the potential of parking lots for the photovoltaic generation of solar electricity. The paper is based on simulations that were carried out for 48 parking lots in Frauenfeld, a typical Swiss medium-sized city of 22 665 inhabitants. Covered with solar carports, these parking lots alone would cover 15-40% of the energy demand by the city's road passenger transport.

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Urban agglomerations show different development patterns and stages. Here, we describe, discuss and compare urban agglomerations in different continents. The introduction section gives a general overview of specific issues of urban agglomerations. Different characteristics in Europe, Asia and America are discussed as experienced by the article's co-authors, living in or working for urban agglomerations in these continents. First, the history of urbanization and agglomeration evolvement is described, then patterns, functional structures and relations, drivers as well as social and demographic characteristics are discussed (e.g. migration, aging, household structure, housing patterns, workplaces, etc.). Transportation infrastructure (roads, public transport systems) is also addressed as trigger for spatial dynamics causing certain effects (floor space, office and apartment rents releasing urban sprawl or hyper-densification), as well as gentrification. Further topics are urban governance and its impact on agglomeration development. Recent state and future trends will be debated, if important. A conclusion section summarizes the comparison of state, dynamics, drivers and trends.

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