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Sustainable development embraces a broad spectrum of social, economic and ecological aspects. Thus, a sustainable transformation process of energy systems is inevitably multidimensional and needs to go beyond climate impact and cost considerations. An approach for an integrated and interdisciplinary sustainability assessment of energy system transformation pathways is presented here. It first integrates energy system modeling with a multidimensional impact assessment that focuses on life cycle-based environmental and macroeconomic impacts. Then, stakeholders’ preferences with respect to defined sustainability indicators are inquired, which are finally integrated into a comparative scenario evaluation through a multi-criteria decision analysis (MCDA), all in one consistent assessment framework. As an illustrative example, this holistic approach is applied to the sustainability assessment of ten different transformation strategies for Germany. Applying multi-criteria decision analysis reveals that both ambitious (80%) and highly ambitious (95%) carbon reduction scenarios can achieve top sustainability ranks, depending on the underlying energy transformation pathways and respective scores in other sustainability dimensions. Furthermore, this research highlights an increasingly dominant contribution of energy systems’ upstream chains on total environmental impacts, reveals rather small differences in macroeconomic effects between different scenarios and identifies the transition among societal segments and climate impact minimization as the most important stakeholder preferences.

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Purpose The life cycle assessment of silicon wafer processing for microelectronic chips and solar cells aims to provide current and comprehensive data. In view of the very fast market developments, for solar cell fabrication the influence of technology and capacity variations on the overall environmental impact was also investigated and the data were compared with the widely used ecoinvent data. Methods Existing material flow models for silicon wafer processing for microelectronic chips and solar cells used for engineering and planning formed a starting point for this analysis. The models represent an average of widely used processes and associated process equipment. The resulting input/output tables formed the data basis for the life cycle assessment. This is a cradle-to-gate investigation, consisting of primary gate-to-gate data for wafer processing. The upstream processes of the necessary inputs were supplemented with data from ecoinvent v2.0. Subsequent manufacturing steps, utilization, and waste disposal of the final products were not included. The software used for creating the inventory and impact assessment was Umberto version 5.5. The Impact 2002+ method was applied for impact assessment. Results For both semiconductor and solar cell fabrication, energy consumption and upstream chemicals production are most relevant for the overall potential environmental impact when only the gate-to-gate processes are considered. The upstream process for wafer production is dominant in solar cell fabrication, but exerts little influence on semiconductor fabrication. In the case of semiconductor fabrication, a comparison with the present ecoinvent dataset "wafer, fabricated, for integrated circuit, at plant" shows large differences. Conclusions In the case of silicon solar cells, the results of this study and the ecoinvent data are very similar and the impact of different fabrication processes appears to be minor.

Energy storage is currently a key focus of the energy debate. In Germany, in particular, the increasing share of power generation from intermittent renewables within the grid requires solutions for dealing with surpluses and shortfalls at various temporal scales. Covering these requirements with the traditional centralised power plants and imports and exports will become increasingly difficult as the share of intermittent generators rises across Europe. Pumped hydropower storage plants have traditionally played a role in providing balancing and ancillary services, and continue to do so. However, the construction of new plants often requires substantial interventions into virgin landscape and bio-habitats; this is often fiercely opposed by local citizens. Utility-scale lithium ion batteries have recently entered the energy scene. Albeit much smaller than most pumped hydropower plants, they can also provide the required balancing and ancillary services. They can be constructed on brownfield sites as and where needed, to support the move towards increasingly decentralised energy systems. Although they are seen by some as a more environmentally friendly option, they do cause impacts relating to the consumption of limited natural resources during the production stage. Addressing initially technological capacity of pumped hydropower storage and utility-scale battery to meet the required services, a simplified LCA will be performed to examine the environmental impacts throughout their life cycles. This includes two sensitivity analyses. Issues addressed in this paper include also methodological issues relating to comparability and those parameters that are pivotal to the LCA result.