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Heavy-duty vehicles (HDVs) are responsible for a significant amount of CO2 emissions in the transport sector. The share of these vehicles is still increasing in the European Union (EU); nevertheless, rigorous CO2 emission reduction schemes will apply in the near future. Different measures to decrease CO2 emissions are being already discussed, e.g., the electrification of the powertrain. Additionally, the impact of autonomous driving on energy consumption is being investigated. The most common types are fuel cell vehicles (FCEVs) and battery-only vehicles (BEVs). It is still unclear which type of powertrain will prevail in the future. Therefore, we developed a method to compare different powertrain options based on different scenarios in terms of primary energy consumption, CO2 emissions, and fuel costs. We compared the results with the internal combustion engine vehicle (ICEV). The model includes a model for the climatization of the driver’s cabin, which we used to investigate the impact of autonomous driving on energy consumption. It became clear that certain powertrains offer advantages for certain applications and that sensitivities exist with regard to primary energy and CO2 emissions. Overall, it became clear that electrified powertrains could reduce the CO2 emissions and the primary energy consumption of HDVs. Moreover, autonomous vehicles can save energy in most cases.

Renewable Energy Communities (RECs) have been defined as modes of collective prosumership under the Renewable Energy Directive (RED II). We evaluate the benefits offered by RECs and the barriers and enablers impacting their uptake. Germany is taken as a case study for a novel multi-disciplinary assessment of a potential REC intended as a climate-neutral, mixed-use district. We found that energy cooperatives may not be suited to form RECs, but the future may see an uptake of innovative organizational structures such as the Consumer Stock Ownership Plan. It has been shown that a high degree of prosumership can provide technical and economic benefits with maximum greenhouse gas savings of 35% and a maximum self-consumption share of 61% compared to no prosumership. The REC has a negative Net Present Value (NPV) after 25 years of operation and lacks financial attractiveness. A positive NPV is only possible by using the cost savings from prosumership to recoup the investments faster. RECs are a promising mode of citizen participation in the energy transition; however, for their application in Germany, together with the currently missing regulatory allowance of sharing energy between small-scale parties over a public grid, dedicated subsidies, one-time grants or price support for operators are needed.

Air pollution caused by traffic and other sources remains a challenge in big cities and urbanized areas in Germany and abroad. Nitrogen dioxide emissions, particulate matter, noise emissions, and ozone are still problematic issues with negative impacts on both the environment and human health. In 2018, the German Federal Government launched the “Lead City Program,” a €130-million fund to support five selected so-called Lead Cities in developing and implementing air quality policies. This article comparatively analyzes the policy-making process and policy content for better air quality in the three (out of five) Lead Cities—Essen, Herrenberg, and Reutlingen. Conceptually, we rely on two theoretical frameworks—the policy package approach (PPA) and the multiple streams framework (MSF). The objective, thus, is an ex-post analysis of policy development by means of two policy science-based concepts. Based on document-based desk research and qualitative interviews with policymakers and stakeholders in each of the three cities, we identified a number of key variables that created a window of opportunity and paved the way for the selection of the policy packages. The resulting five key variables are direct interaction between the different governance levels, long-standing non-compliance with the European Union (EU) NO2 limit values in many German cities, the resulting European and national infringement proceedings, the diesel scandal, and the Lead City Program as overall multiple stream-coupling facilitators. The results are then discussed regarding the explanatory power of MSF and PPA and the mutual potential linkages these concepts offer for future research.

Increasing the share of Renewable energy sources in District Heating (DH) systems is of great importance to mitigate their CO2 emissions. The combined integration of Solar Thermal Collectors (STC) and Thermal Energy Storage (TES) into existing Combined Heat and Power (CHP) systems can be a very cost-effective way to do so. This paper aims at finding the optimal design of STC and TES systems integrated in existing CHP’s considering two distinct objectives: economic profitability and environmental impact. To do so, we developed a three-stage framework based on Pareto-optimal solutions generated by multi-objective optimization, a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)-entropy method to select the optimal solution, followed by the definition of final Operation strategy. We proposed relevant improvement of the state-of-the-art models used in similar analysis. We also applied the proposed methodology to the case of a representative, 12 MWth CHP plant. Our results show that, while the addition of TES or STC alone results in limited performances and/or higher costs, both the cost and the CO2 emissions can be reduced by integrating the optimal combination of STC and TES. For the selected, optimal solution, carbon emissions are reduced by 10%, while the Annual Total Cost (ATC) is reduced by 3%. It also improves the operational flexibility and the efficiency by peak load shaving, load valley filling and thus by decreasing the peak load boiler operation. Compared to the addition of STC alone, the use of TES results in an increased efficiency, from 88% to 92%. The optimal share of STC is then increased from 7% to 10%.

Nowadays decarbonisation of the energy system is one of the main concerns for most governments. Renewable energy technologies, such as rooftop photovoltaic systems and home battery storage systems, are changing the energy system to be more decentralised. As a consequence, new ways of energy business models are emerging, e.g., peer-to-peer energy trading. This new concept provides an online marketplace where direct energy exchange can occur between its participants. The purpose of this study is to conduct a content analysis of the existing literature, ongoing research projects, and companies related to peer-to-peer energy trading. From this review, a summary of the most important aspects and journal papers is assessed, discussed, and classified. It was found that the different energy market types were named in various ways and a proposal for standard language for the several peer-to-peer market types and the different actors involved is suggested. Additionally, by grouping the most important attributes from peer-to-peer energy trading projects, an assessment of the entry barrier and scalability potential is performed by using a characterisation matrix.

This perspective article aims to identify key research priorities to make the waste-to-energy sector compatible with the societal goals of circularity and carbon neutrality. These priorities range from fundamental research to process engineering innovations and socio-economic challenges. Three focus areas are highlighted: (i) the optimization of flue gas cleaning processes to minimize gaseous emissions and cross-media, (ii) the expansion of process control intelligence to meet targets for both material recovery and energy recovery, and (iii) climate neutrality, with the potential for negative emissions via the removal of atmospheric carbon dioxide across the full cycle of the waste resource. For each area, recent research trends and key aspects that are yet to be addressed are discussed.

Power system security is increasingly endangered due to novel power flow situations caused by the growing integration of distributed generation. Consequently, grid operators are forced to request the curtailment of distributed generators to ensure the compliance with operational limits more often. This research proposes a framework to simulate the incidental amount of renewable energy curtailment based on load flow analysis of the network. Real data from a 110 kV distribution network located in Germany are used to validate the proposed framework by implementing best practice curtailment approaches. Furthermore, novel operational concepts are investigated to improve the practical implementation of distributed generation curtailment. Specifically, smaller curtailment level increments, coordinated selection methods, and an extension of the n-1 security criterion are analyzed. Moreover, combinations of these concepts are considered to depict interdependencies between several operational aspects. The results quantify the potential of the proposed concepts to improve established grid operation practices by minimizing distributed generation curtailment and, thus, maximizing power system integration of renewable energies. In particular, the extension of the n-1 criterion offers significant potential to reduce curtailment by up to 94.8% through a more efficient utilization of grid capacities.