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SummaryThe German government has adopted a law that requires sewage plants to go beyond the recovery of phosphorus from wastewater and to promote recycling. We argue that there is no physical global short‐ or mid‐term phosphorus scarcity. However, we also argue that there are legitimate reasons for policies such as those of Germany, including: precaution as a way to ensure future generations’ long‐term supply security, promotion of technologies for closed‐loop economics in a promising stage of technology development, and decrease in the current supply risk with a new resource pool.

Abstract Waste disposal is a core issue worldwide. Different researches are being carried out in order to handle waste materials, generated in industrial production and application processes, e.g. paint residue from metal coating in the automobile industry. Often waste is disposed in landfills at substantial economic and environmental cost. Combustion is another way to get rid of possibly hazardous waste. Pulverized fuel combustion is one of the latest combustion technologies. However, pulverized fuel combustion faces severe problems if the waste (fuel) contains components with low melting point. Having a low melting point, it gets difficult to manage and convey the pulverized material to the hot combustion chamber. The melting of fuel causes clogging in the fuel transport nozzle used to convey the material into the combustion chamber. In this work, a new technology for combustion of materials with low melting points is proposed, focusing on apparatus and nozzle design to prevent clogging. For this purpose, different nozzle designs were evaluated by multi-phase CFD simulations. Two sets of nozzle air flow rates were used in four nozzles. Effect of different flow rates and fuel particle size on combustion temperatures are also discussed. It was noted that nozzle air flow rate has a strong influence on the temperature distributions. Small fuel particle sizes result in wider combustion zones while larger particles give longer combustion zones. The results come up with optimized nozzle design and nozzle air flow for transportation of pulverized material with low melting point.

Abstract The increasing global energy demand, the foreseen reduction of available fossil fuels and the increasing evidence off global warming during the last decades have generated a high interest in renewable energy sources. However, renewable energy sources, such as wind and solar power, have an intrinsic variability that can seriously affect the stability of the energy system if they account for a high percentage of the total generation. The Energy Flexibility of buildings is commonly suggested as part of the solution to alleviate some of the upcoming challenges in the future demand-respond energy systems (electrical, district heating and gas grids). Buildings can supply flexibility services in different ways, e.g. utilization of thermal mass, adjustability of HVAC system use (e.g. heating/cooling/ventilation), charging of electric vehicles, and shifting of plug-loads. However, there is currently no overview or insight into how much Energy Flexibility different building may be able to offer to the future energy systems in the sense of avoiding excess energy production, increase the stability of the energy networks, minimize congestion problems, enhance the efficiency and cost effectiveness of the future energy networks. Therefore, there is a need for increasing knowledge on and demonstration of the Energy Flexibility buildings can provide to energy networks. At the same time, there is a need for identifying critical aspects and possible solutions to manage this Energy Flexibility, while maintaining the comfort of the occupants and minimizing the use of non-renewable energy. In this context, the IEA (International Energy Agency) EBC (Energy in Buildings and Communities program) Annex 67: “Energy Flexible Buildings” was started in 2015. The article presents the background and the work plan of IEA EBC Annex 67 as well as already obtained results. Annex 67 is a corporation between participants from 16 countries: Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Ireland, Italy, The Netherlands, Norway, Portugal, Spain, Switzerland and UK.

Abstract Despite the comparatively limited stock of vehicles, heavy-duty road transport is responsible for a major share of CO2 emissions from the European transport sector. Electric trucks powered by overhead lines, so-called trolley trucks or catenary hybrid trucks, have been proposed as a potential GHG mitigation option. However, from the perspective of the energy system, trolley trucks constitute an additional and inflexible electricity demand. Here, we analyse scenarios with an ambitious European market diffusion of trolley trucks and their impact on the electricity system and CO2 emissions. Our results show that trolley trucks can noteworthily reduce the CO2 emissions from heavy road transport even when the additional CO2 emissions from electricity generation are taken into account. Furthermore, the actual impact of the additional load from trolley trucks on the total energy system is limited. Compared to the anticipated electricity demand from passenger cars in 2030, trolley trucks require less energy and the load is more equally distributed over daytime. Our findings thus show that electric trucks are an interesting option for CO2 mitigation in heavy road transport.

The environmental footprint of photovoltaic electricity is usually assessed using nominated power or life cycle energy output. If performance degradation is considered, a linear reduction in lifetime energy output is assumed. However, research has shown that the decrease in energy output over time does not necessarily follow a linear degradation pattern but can vary at different points in the module’s lifetime. Further, photovoltaic modules follow different degradation patterns in different climate zones. In this study, we address the influence of different degradation aspects on the greenhouse gas (GHG) emissions of PV electricity. Firstly, we apply different non-linear degradation scenarios to evaluate the GHG emissions and show that the differences in GHG emissions in comparison to a linear degradation can be up to 6.0%. Secondly, we use the ERA5 dataset generated by the ECMWF to calculate location-dependent degradation rates and apply them to estimate the location-specific GHG emissions. Due to the reduction in lifetime energy output, there is a direct correlation between the calculated degradation rate and GHG emissions. Thirdly, we assess the impact of climate change on degradation rates and on the respective GHG emissions of photovoltaic electricity using different climate change scenarios. In a best-case scenario, the GHG emissions are estimated to increase by around 5% until the year 2100 and by around 105% by 2100 for a worst-case scenario.

The change from a centralized to a decentralized energy supply creates new challenges in the planning of such energy supply concepts. Specialized planning tools that can cope with the complex requirements and multi-layered boundary conditions of local energy use are therefore needed. Existing methods need to be further developed and optimized to suit the complex stakeholder structures encountered in innovative district projects, as well as for research purposes. This paper presents selected aspects and challenges in the development of an application-oriented planning tool. Using a North German district as a case study, the usability of a Building Information Model as an aggregated data platform is tested in the context of a residential energy district planning process. In addition, the modeling of heating grids using a combination of Geographic Information System and open source thermodynamic tools is presented. Economic valuation methods are examined to determine the extent to which the value of flexibility and access to local flexibility markets can be taken into account. Finally, an approach for evaluating the ecological aspects of the district energy supply is presented, based on the dynamic assessment of imported and exported energy quantities.

AbstractIf transdisciplinary sustainability research is to contribute to sustainability transitions, issues of power dynamics need to be understood and accounted for. However, examples of concrete methods that put this into practice are sparse. This paper presents a conceptual and methodological framework that develops a better understanding of the power phenomenon, while providing actionable knowledge. By focussing on the context of social innovation in energy transitions, we demonstrate how different theoretical conceptualisations of power can be translated into a collaborative, transdisciplinary research design. In a facilitated process, researchers, policy workers and practitioners from diverse social innovation fields developed and tested the Transformative Power Lab approach and co-wrote a ‘Power Guide’ as a strategic exploration of power dynamics in sustainability transitions, specifically regarding social innovation in energy transitions. Based on the insights that emerged during this process, we discuss how transdisciplinary and action-oriented approaches in sustainability transition studies might benefit from this approach and, potentially, develop it further.

This is the first attempt to combine disposed bottle caps and natural fibres into sandwich panels. A full factorial design is performed to identify the effects of the skin type (aluminium or coir fibre reinforced laminates) and bottle cap core packing (cubic and orthotropic) on the mechanical properties of the proposed panels. The coir fibre composite skin provides maximum core shear strength, 29 % higher than the aluminium-based panels, in cubic packing, while the flexural modulus is reduced by 45 %. An interlocking effect between the skin and the core is evidenced when coir fibre composites are used. In addition, the cubic cell packing increases the specific mechanical properties, even though with a higher density. The results highlight a promising association of green components and plastic bottle caps for secondary structural applications.