The transition to a carbon-neutral energy system requires widespread deployment of renewable energy sources and economically feasible energy storage solutions. This study presents a comprehensive optimization framework that jointly addresses the design and control of a nonlinear energy system supplying both heat and electricity to the Dietenbach district in Freiburg, Germany. The proposed system integrates solar and wind power with battery storage and seasonal thermal energy storage coupled via a heat pump, enhancing self-sufficiency and mitigating seasonal supply-demand mismatches. A multi-node lumped-parameter model captures heat transfer within the pit thermal energy storage, forming the basis of a periodic optimal control problem solved numerically. An averaging method reduces computation time by 80.5% while preserving fidelity for year-long optimization. A case study shows a projected total yearly energy cost of 5.93 e e/m e/m2 for combined heat and electricity, which is 73% lower than the German average. This study underscores the feasibility of designing economically viable, autonomous energy communities in real-world scenarios and provides an efficient, robust optimization framework for designing system components and operational control strategies.

Deploying onshore wind energy as a cornerstone of future global energy systems challenges societies and decision-makers worldwide. Expanding wind energy should contribute to a more sustainable electricity generation without harnessing humans and their environment. Opponents often highlight the negative environmental impacts of wind energy to impede its expansion. This study reviews 152 studies to synthesize, summarize, and discuss critically the current knowledge, research gaps, and mitigation strategies on the environmental impacts of onshore wind energy. The investigated effects comprise impacts on the abiotic and biotic environment, with birds and bats in particular, noise and visual impacts. Effects are discussed in the context of social acceptance, other energy technologies, and wind energy expansion in forests. The review illustrates that many effects are highly case-specific and must be more generalizable. Studies are biased regarding the research focus and areas, needing more standardized research methods and long-term measurements. Most studies focus on the direct mortality of birds and bats at wind farms and are concentrated in Europe and North America. Knowledge gaps persist for many impact categories, and the efficacy of mitigation strategies has yet to be proven. More targeted, unbiased research is required that allows for an objective evaluation of the environmental impacts of wind energy and strategies to mitigate them. Impacts, such as those on biodiversity, need to be addressed in the context of other anthropogenic influences and the benefits of wind energy. This forms the basis for a socially acceptable, efficient, and sustainable expansion of wind energy.

Offshore wind energy provides a promising option for substituting conventional energies due to its low greenhouse gas emissions, cost-effectiveness, and abundant wind resources at seas. The installed capacity, available area, technological advancements, and wind resource development under climate change drive the offshore wind potential. Thus, the goal is to develop 28 techno-climatic wind energy expansion scenarios, considering installed capacity expansion paths and potential wind farm sites to estimate the national and global wind energy yield in 2025-2054. The study tests the hypothesis that technological advancements are more influential for future offshore wind energy yield compared to climate-related wind resource changes. Globally, at more than 80 % of studied sites, the capacity factors significantly decrease under all evaluated climate change scenarios in 2025-2054. However, it should not hinder future offshore wind expansion since the climate change-induced wind resource change is far less than the capacity factor variability of the potential wind farm sites within the exclusive economic zones. This study also found that if the wind energy expansion continues at the same pace as in 2019-2023 until 2030, China could gain the highest average energy yield at 280.9 TWh annually. Besides, the results indicate that the wind turbine type is more critical to the capacity factor than the climate change impact. At 87.9 % of all evaluated sites, the 10 MW reference wind turbine yields the highest capacity factors out of seven reference wind turbines tested.

Deploying onshore wind energy as a cornerstone of future global energy systems challenges societies and decision-makers worldwide. Expanding wind energy should contribute to a more sustainable electricity generation without harnessing humans and their environment. Opponents often highlight the negative environmental impacts of wind energy to impede its expansion. This study reviews 152 studies to synthesize, summarize, and discuss critically the current knowledge, research gaps, and mitigation strategies on the environmental impacts of onshore wind energy. The investigated effects comprise impacts on the abiotic and biotic environment, with birds and bats in particular, noise and visual impacts. Effects are discussed in the context of social acceptance, other energy technologies, and wind energy expansion in forests. This review illustrates that many effects are highly case-specific and must be more generalizable. Studies are biased regarding the research focus and areas, needing more standardized research methods and long-term measurements. Most studies focus on the direct mortality of birds and bats at wind farms and are concentrated in Europe and North America. Knowledge gaps persist for many impact categories, and the efficacy of mitigation strategies has yet to be proven. More targeted, unbiased research is required that allows for an objective evaluation of the environmental impacts of wind energy and strategies to mitigate them. Impacts, such as those on biodiversity, need to be addressed in the context of other anthropogenic influences and the benefits of wind energy. This forms the basis for a socially acceptable, efficient, and sustainable expansion of wind energy.

Rooftop solar photovoltaics can significantly contribute to global energy transitions by providing clean, decentralized energy without the need for new land, thereby avoiding land-use conflicts. It serves as a valuable complement to other renewable-energy sources and is expected to play a crucial role in future electricity systems. Due to the spatiotemporal variability in the solar radiation on roof surfaces, it is essential to determine the potentials of the rooftop photovoltaics and its variations in specific regions. In Germany, this potential was assessed in 5 km × 5 km zones, as well as at the federal-state and national levels. High-quality satellite and reanalysis data were used to determine the power output of the solar photovoltaics. Additionally, high-resolution (2 m × 2 m) European Settlement Map data, calibrated with solar cadastre data, were utilized to evaluate different scenarios. The results show that the potential is concentrated in larger urban areas and the southwestern part of Germany due to the availability of rooftop space and solar radiation. Overall, the national rooftop areas are substantial across all scenarios, ranging from 2100 to 4500 km2. The applied methods and scenarios provide a straightforward way to reveal the spatiotemporal variability and define realistic ranges of the solar photovoltaic potential without requiring detailed information about each building. However, assessing the rooftop photovoltaic potential remains challenging and uncertain due to the lack of large-scale, high-resolution data on building characteristics and the complexity of the solar radiation distribution in urban environments.

The intensification of climate change impacts requires a fast and efficient transition of energy systems and deployment of renewable energies worldwide. An adequate site assessment strategy forms the basis for expanding installed capacities and energy yield. This study applies a set of meaningful criteria to determine site suitability for Germany's onshore wind and utility-scale solar photovoltaics facilities. An aggregated priority index involving meteorological-technical, economic, and environmental criteria is developed and used in a new concept for identifying renewable energy priority zones, where installations of wind and solar energy facilities should be prioritized. As a novelty, this resource-centered approach does not only analyze the mean energy potential as a meteorological criterion but also accounts for other characteristics such as variability, complementarity, and predictability. The results indicate that reducing legal restrictions substantially facilitates wind and solar energy capacity expansion in prioritized zones. With weak restrictions, up to 22% and 12% of Germany represent priority zones for an efficient and sustainable use of solar and wind energy. However, due to the intermittent nature of wind and solar resources, mismatches between generation potential and electricity demand would persist even with substantial capacity expansion. Future energy systems must advance the expansion of renewable energy capacities just as the flexibilization of demand or an increase of storage capacities to guarantee future energy security and mitigate climate change. The newly developed renewable energy priority zones are a starting point and can be transferred to other study areas by specifically adapting criteria and their weighting.

The success of the German electricity mix transformation depends on the variable renewable energies solar photovoltaics and wind. Their extensive exploitation until 2030 and beyond is a cornerstone on the road to climate neutrality, which Germany aims for in 2045. We use actual electricity generation and consumption data from 2015 to 2021 to analyze the development and potential of renewable energy shares in the German electricity mix and discuss future challenges for implementing the transformation until 2030. Current electricity consumption mostly exceeded renewable electricity generation, leading to consumption-supply mismatch and large residual loads. Renewable electricity generation met the net electricity consumption in 0.16% of all hours analyzed. No day renewables met net electricity consumption; substantial residual loads always occurred. The natural variability of the territorial availability of solar and wind was identified as the main reason for the high residual load shares. Results of a high-resolution wavelet analysis illustrate in detail the extend of the temporal, territorial variability of wind and solar along the studied timeline. Together with the annual gross electricity consumption values discussed for 2030 of 650-800 TWh these findings were used for projecting the future consumption-supply mismatch. The most optimistic scenarios show that only strict compliance with the targeted expansion and moderate increase in electricity consumption enables the achievement of set energy goals. Missing expansion targets and increasing electricity consumption challenge the 2030 renewable generation targets in 47% of the most optimistic scenarios. It is concluded that the natural variability of solar and wind will continue to be a major challenge for meeting Germany's electricity consumption in the near future.

Wind energy is crucial in German energy and climate strategies as it substitutes carbon-intensive fossil fuels and achieves substantial greenhouse gas (GHG) reductions. However, wind energy deployment currently faces several problems: low expansion rates, wind turbines at the end of their service life, or the end of remuneration. Repowering is a vital strategy to overcome these problems. This study investigates future annual GHG payback times and emission savings of repowered wind turbines. In total, 96 repowering scenarios covering a broad range of climatological, technical, economic, and political factors affecting wind energy output in 2025–2049 were studied. The results indicate that due to more giant wind turbines and geographical restrictions, the amount of repowerable sites is reduced significantly. Consequently, in most scenarios, emission savings will dramatically diminish compared to current savings. Even in the best-case scenario, the highest emission savings’ growth is at 11%. The most meaningful drivers of GHG payback time and emission savings are wind turbine type, geographical restrictions, and GHG emissions. In contrast, climate change impact on the wind resource is only marginal. Although repowering alone is insufficient for achieving climate targets, it is a substantial part of the wind energy strategy. It could be improved by the synergies of different measures presented in this study. The results emphasize that a massive expansion of wind energy is required to establish it as a cornerstone of the future energy mix.