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Background Problems such as climate change, environmental pollution, nuclear disposal and unsustainable production and consumption share a common feature: they pose long-term challenges because of their complex nature, potentially severe consequences, and the demanding problem-solving paths. These challenges may have long-lasting impacts on both present and future generations and, therefore, require to be addressed through a long-term governance perspective, i.e., coherent and consistent policy-making across sectors, institutions, and temporal scales. Dealing with these challenges is a core task of policy-making in modern societies, which requires problem-solving skills and capabilities. In this context, we identify long-term governance traces in the literature, illustrate the case of energy transition towards renewable energy systems as a long-term governance case, and elaborate on the scope and definition of long-term governance and its research. Main text We elaborate an analytical framework for long-term governance (LTG), based on five building blocks: the ‘environment’, which details the policy-making arena; the ‘policy issues’, which elaborates on the problems to be dealt with by LTG; the ‘key challenges and driving force’, revealing LTG mechanisms; the ‘key strategies’, in which promising approaches for LTG are identified; and the ‘policy cycle’, where governance impacts on different policy phases are discussed. In essence, we understand long-term governance at its core as a reflexive policy-making process to address significant enduring and persistent problems within a strategy-based decision-making arena to best prepare for, navigate through, and experiment with a changing environment. Conclusions The framework does not describe specific processes or individual cases in detail. Instead, it should be understood as an illustration of long-term governance characteristics at a more general level. Such a framework may help to structure the field of long-term policy-making, guide future research on conceptual, comparative, and empirical in-depth studies, and may provide orientation and action knowledge for making our governance system sustainable. Stimulating and broadening research on long-term issues seems indispensable, given the existence of several ‘grand challenges’ that require successful long-term governance.

Background To limit climate change and reduce further harmful environmental impacts, the reduction and substitution of fossil energy carriers will be the main challenges of the next few decades. During the United Nations Climate Change Conference (COP28), the participants agreed on the beginning of the end of the fossil fuel era. Hydrogen, when produced from renewable energy, can be a substitute for fossil fuel carriers and enable the storage of renewable energy, which could lead to a post-fossil energy age. This paper outlines the environmental impacts and levelized costs of hydrogen production during the life cycle of water electrolysis technologies. Results The environmental impacts and life cycle costs associated with hydrogen production will significantly decrease in the long term (until 2045). For the case of Germany, the worst-case climate change results for 2022 were 27.5 kg CO 2eq. /kg H 2 . Considering technological improvements, electrolysis operation with wind power and a clean heat source, a reduction to 1.33 kg CO 2eq. /kg H 2 can be achieved by 2045 in the best case. The electricity demand of electrolysis technologies is the main contributor to environmental impacts and levelized costs in most of the considered cases. Conclusions A unique combination of possible technological, environmental, and economic developments in the production of green hydrogen up to the year 2045 was presented. Based on a comprehensive literature review, several research gaps, such as a combined comparison of all three technologies by LCA and LCC, were identified, and research questions were posed and answered. Consequently, prospective research should not be limited to one type of water electrolysis but should be carried out with an openness to all three technologies. Furthermore, it has been shown that data from the literature for the LCA and LCC of water electrolysis technologies differ considerably in some cases. Therefore, extensive research into material inventories for plant construction and into the energy and mass balances of plant operation are needed for a corresponding analysis to be conducted. Even for today’s plants, the availability and transparency of the literature data remain low and must be expanded.

Islands face unique challenges on their journey towards achieving carbon neutrality by the mid-century, due to the lack of energy interconnections, limited domestic energy resources, extensive fossil fuel dependence, and high load variance requiring new technologies to balance demand and supply. At the same time, these challenges can be turned into a great opportunity for economic growth and the creation of jobs with non-interconnected islands having the potential to become transition frontrunners by adopting sustainable technologies and implementing innovative solutions. This paper uses an advanced energy–economy system modeling tool (IntE3-ISL) accompanied by plausible decarbonization scenarios to assess the medium- and long-term impacts of energy transition on the energy system, emissions, economy, and society of the island of Mayotte. The model-based analysis adequately captures the specificities of Mayotte and examines the complexity, challenges, and opportunities to decarbonize the island’s non-interconnected energy system. The energy transition necessitates the adoption of ambitious climate policy measures and the extensive deployment of low- and zero-carbon technologies both in the demand and supply sides of the energy system, accounting for the unique characteristics of each individual sector, while sectoral integration is also important. To reduce emissions from hard-to-abate sectors, such as transportation and industry, the measures and technologies can include the installation and use of highly efficient equipment, the electrification of end uses (such as the widespread adoption of electric vehicles), the large roll-out of renewable energy sources, as well as the production and use of green hydrogen and synthetic fuels.

Background Addressing global climate challenges necessitates a shift toward sustainable energy systems, with public acceptance of energy technologies playing a vital role in their successful adoption. While extensive research has been conducted on this topic, the lack of a unified framework for integrating various data and approaches from existing studies remains a challenge. This inconsistency makes it difficult to compare findings across different contexts and impedes the development of a comprehensive understanding of the factors influencing acceptance. This review aims to address this challenge by systematically evaluating the statistical methods used in ten large-scale studies on public acceptance of energy technologies in Western Europe published between 2012 and 2023. This Work allows researchers to more effectively compare methodologies and results, offering a transparent and structured approach for analysis, thereby enhancing the overall methodological assessment. Main text The review of ten large-scale studies identified valuable insights and opportunities for improving the analysis of public acceptance of energy technologies. Traditional methods like regression analysis have provided a solid foundation, highlighting key factors such as perceived benefits, trust, and attitudes. However, the review also revealed potential for growth by integrating more advanced techniques like AI-supported analysis, sentiment analysis, and agent-based modelling. These newer approaches offer the ability to capture complex, non-linear relationships and provide predictive insights. The introduction of statistical pattern graphics significantly enhances the clarity and comparability of methodologies, helping researchers to better understand and improve their approaches, ultimately supporting more accurate and impactful studies. Conclusions The review emphasizes the need for a unified analytical framework that integrates diverse methods, including both traditional statistical techniques and emerging approaches such as machine learning and sentiment analysis, to enhance the comparability of studies on public acceptance of energy technologies. By consolidating these varied methodologies into a cohesive framework, researchers can generate more consistent, robust insights that account for the complexities of public attitudes across different contexts. This unified approach not only improves the generalizability of findings but also provides stronger empirical evidence to guide policymakers in crafting more informed, effective strategies for promoting sustainable energy transitions at both local and global levels.

This study focuses on investigating the impact and cost‐competitiveness of solar power in a highly hydropower‐driven northern energy system. The goal is to assess the role of rooftop photovoltaics (PV) in the Norwegian energy system toward 2050 under different energy transition pathways. Energy system analysis is conducted using the IFE‐TIMES‐Norway model, with an integrated detailed representation of rooftop PV based on the tilt and azimuth of existing rooftops in Norway. A thorough sensitivity analysis is conducted to illustrate how investment in rooftop PV varies under different system and parameter conditions and to disclose important barriers for PV in similar energy systems. The results show that when PV investments are facilitated, solar power can potentially stand for 56% of all new investments, resulting in a share of 10% of the total electricity generation. With less competition from onshore wind power and favorable investment parameters, especially lowering the demand for the rate of return, the investments in PV will be four times higher and reach their full potential in commercial and apartment buildings by 2050. Additionally, the results highlight that the cost parameter functions as a barrier to other solutions that facilitate increased PV investments, such as flexibility and energy storage. This study investigates the impact and cost‐competitiveness of rooftop solar power in a highly hydropower‐driven northern energy system toward 2050. The role of rooftop photovoltaics (PV) is assessed under different energy transition pathways and through a sensitivity analysis aiming to disclose important barriers to PV investments in the energy system. The analysis is conducted utilizing the energy system model, IFE‐TIMES‐Norway.

Background The transition to renewable energy is crucial for decarbonising the energy system but creates land-use competition. Whilst there is consensus on the need for local responsibility in achieving climate neutrality, debates continue over where to implement renewable energy plants. The Public Participation Geographic Information System (PPGIS) scenario approach can facilitate these debates and improve equity and procedural and distributive justice. Results The findings highlight the effectiveness of the PPGIS method in assessing the spatial impact of technologies on agriculture and landscapes. The approach was tested in a rural German municipality to help stakeholders and citizens recognise the potential for land-based solar energy even under strict constraints. These insights were shared to support decision-makers on land-use changes to increase renewable energy production. Conclusions The findings indicate that the PPGIS scenario approach is valuable for improving equity and mutual understanding in local decision-making processes. Incorporating stakeholders’ and citizens’ perspectives into renewable energy planning enhances the transparency, legitimacy, and acceptability of land-use decisions. The ability to visualise and quantitatively assess different scenarios makes PPGIS particularly useful for addressing the complexities of public debates on land-use requirements for renewable energy systems.

Background Concerns about the sustainability of commercially available batteries have driven the development of post-lithium systems. While previous studies on Magnesium batteries have explored both the potential environmental footprint of battery production and their possible use in stationary applications, their environmental impact in electromobility remains unexplored. This study provides an initial prospective evaluation of the environmental performance of a theoretical Mg–S battery for potential use in electric vehicles (EVs). Utilizing life cycle assessment (LCA) methodology, various scenarios are analyzed and compared to conventional systems. The analysis focuses on potential environmental impacts, including climate change, resource criticality, acidification of the biosphere, and particulate matter emissions. Results In the battery pack level, the Magnesium anode and its respective supply chain have been identified as main drivers of environmental burdens. Additional concerns arise from the uneven geographical distribution of Mg production, which leads to dependency on few producers. In terms of resource criticality, the Mg–S battery could carry significant advantages over benchmark systems. A look into the use-phase via theoretical implementation in an electric vehicle (EV) also suggests that the Magnesium based EV could perform on a comparable level to an LIB EV, also outperforming conventional ICEVs in several impact categories. Conclusions This study is based on optimistic assumptions, acknowledging several remaining technical challenges for the Mg battery. Consequently, the results are indicative and carry a significant degree of uncertainty. Nonetheless, they suggest that the Mg–S system shows promising environmental sustainability performance, comparable to other reference systems.

Background Smart home technologies (SHT) make it easier than ever to track energy demands and are expected to contribute to the implementation of sustainability strategies. In particular, they are supposed to enable promising demand side management strategies by altering user behaviour towards sustainability while ensuring the balance of energy supply and demand. For determining environmental impacts of products and technologies, the methodology of life cycle assessment (LCA) is an established tool. While large parts of LCAs are standardised, the consideration of user behaviour related effects has not been specified. By adopting an interdisciplinary perspective, this literature study contributes to the future development of a standardized methodology for the operationalisation of behaviour in LCAs. Results Three main strategies for operationalising behaviour in LCA studies were identified: (1) behaviour theory-based approaches, (2) model-based behaviour predictions and (literature-based) deductions, and (3) averages and assumptions. The results of this literature study show that the selection of the strategy is crucial as the user behaviour and methods used for LCAs have a significant impact on the environmental and economic payback periods and calculated overall impact of SHTs. Findings from the social sciences on practices and household activities that can be influenced by SHTs, are not systematically applied. Conclusions Our literature analysis makes it clear that LCA results depend on various factors. Selected operationalisation and methodological approaches, respectively, can play a key role. Depending on the method chosen the results can vary by several orders of magnitude and are not always comparable. Simplified approaches for integrating user behaviour into LCAs like assumptions and average values can be a first step in accounting for the relevance of behaviour. However, it is important to bear in mind that these approaches may not reflect actual user behaviour, as this can be subjected to a limited changeability of certain household practices and habits. On the basis of the results, the authors recommend greater interdisciplinary co-operation in the conduction of LCAs on SHTs, ranging from a common definition of the scope, to the implementation of socio-scientific research and survey methods, to the derivation of policies.

Background Photovoltaic (PV) systems are nowadays a central pillar in the expansion of renewable energy in Germany. Nevertheless, further significant growth in renewable energy will be needed in the future to meet the national emission reduction targets set by the German government. Homeowners play a crucial role in the expansion of PV capacity. In a discrete choice experiment, we empirically examine the impact of a large number of dimensions on homeowners’ PV adoption, including attributes that have received less attention in the literature so far, such as the included (smart energy) services, government subsidies, and forms of financing. Results Our results show that increasing levels of smart energy services for PV systems increase respondents’ valuation of smart energy services, while increasing the access rights of the contractual partner has a negative impact on the valuation. The latter negative effect is mitigated by an element of co-determination. Furthermore, our results point to the importance of government subsidies as a measure to increase PV adoption. Participants preferred one-time (or continuous) payments over continuous (or one-time) payments when government grants amounted to 40% (or 10%) of the investment cost; they were indifferent between both forms when subsidies amounted to 20% of the investment cost. Homeowners clearly preferred loan financing to self-financing only at an effective interest rate of 1.03%, as opposed to 3.53%. This result indicates a limited effectiveness of this subsidy measure, which is designed to overcome the problem of high investment costs from a conceptual point of view. Our results also show that homeowners are not so heterogeneous when it comes to the importance they attach to certain attributes related to PV adoption. Decisions were made independent of socio-demographic characteristics, but are related in some cases to the homeowners’ value orientations and risk inclination. Conclusions Homeowners are more likely to adopt smart energy services when they are involved in the typically automated processes through decision prompts. Financial factors are of pivotal role. There is a need to tailor financing strategies, as preferences for subsidy schemes vary with the level of financing. In addition, low-interest loans are ineffective in reducing the high upfront costs of PV deployment. Smart energy services have great potential, but there are also some caveats.

Background Sustainability assessment comprises many different forms of assessment—from Life Cycle Sustainability Assessment to freely chosen indicator assessments—often yielding contradictory results. Multi-criteria decision-analysis (MCDA) methods have been recognized as a powerful and frequently applied tool to support decision-making in the field of energy. This study analyzes the application of MCDA in the sustainability assessment of energy technologies and systems within the Helmholtz Association, a network of German research centers addressing important topics ranging from cancer research to polar science. Energy technologies are a key focus of research within several Helmholtz research centers. Based on 20 case studies performed by Helmholtz researchers, we identify trends, challenges, and opportunities in criteria selection, MCDA method application, and stakeholder engagement. Results The selection of criteria and indicators often reflects the triple bottom line framework, with a strong emphasis on environmental and economic dimensions, while social criteria receive little attention due to methodological gaps. For indicator aggregation, there were three preferred methods: the Weighted Sum Method (WSM), the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) for compensatory studies due to its ease of application and simplicity, and the Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE) due to its non-compensatory attributes, consistent with the principles of strong sustainability. However, inconsistencies in weight elicitation methods, with frequent misalignment between the chosen methods and underlying MCDA principles, were found in the analyzed studies. The integration of stakeholders remains underutilized, with most studies involving experts but lacking broader societal involvement. Participatory techniques such as workshops and surveys are mainly applied for criteria weighting, but their implementation across all MCDA stages remains limited. Analysis of group decision-making approaches indicates a predominance of input-level aggregation, with few studies exploring comparative or output-level techniques. Conclusions This paper highlights the need for methodological advancements in social sustainability assessments and more robust stakeholder engagement strategies. In addition, further education on MCDA methods is needed to bridge the knowledge gaps of practitioners. By comparing Helmholtz MCDA practices with best practices from other research, this work aims to strengthen the sustainability assessment of energy technologies and systems.