In order to effectively combat the effects of global warming, all sectors must actively reduce greenhouse gas emissions in a sustainable and substantial manner. Sector coupling has emerged as a critical technology that can integrate energy systems and address the temporal imbalances created by intermittent renewable energy sources. Despite its potential, current sector coupling capabilities remain underutilized, and energy modeling approaches face challenges in understanding the intricacies of sector coupling and in selecting appropriate modeling tools. This paper presents a comprehensive review of sector coupling technologies and their role in the energy transition, with a specific focus on the integration of electricity, heat/cooling, and transportation, as well as the importance of hydrogen in sector coupling. Additionally, we conducted an analysis of 27 sector coupling models based on renewable energy sources, with the goal of aiding deciders in identifying the most appropriate model for their specific modeling needs. Finally, the paper highlights the importance of sector coupling in achieving climate protection goals, while emphasizing the need for technological openness and market-driven conditions to ensure economically efficient implementation.

In a global context where sustainable growth is imperative, understanding carbon emissions in significant regions is essential. Henan Province, being a vital region in China for population, agriculture, industry, and energy consumption, plays a crucial role in this understanding. This study, rooted in the need to identify strategies that not only meet China’s broader carbon neutrality objectives but also offer insights regarding global sustainability models, utilizes the STIRPAT model combined with scenario analysis. The aim was to forecast carbon emission trajectories from 2020 to 2060 across the key industries—electricity, steel, cement, transportation, coal, and chemical—that are responsible for over 80% of the total emissions in Henan. The findings suggest a varied carbon peak timeline: the steel and cement industries might achieve their peak before 2025, and the transportation, coal, and chemical sectors might achieve theirs around 2030, whereas that of the power industry could be delayed until 2033. Significantly, by 2060—a landmark year for Chinese carbon neutrality ambitions—only the electricity sector in Henan shows potential for zero emissions under an extreme scenario. This study’s results underscore the importance of region-specific strategies for achieving global carbon neutrality and offer a blueprint for other populous, industrialized regions worldwide.

The Germans energy transition (Energiewende) is a long-term strategy aimed at transforming the country's energy system to achieve carbon neutrality by 2045. This transition is centered on three key pillars: improving energy efficiency, accelerating the deployment of renewable energy, and ensuring a stable energy supply during the shift away from fossil fuels. Over the past decades, Germany has made significant progress in expanding renewable energy sources, particularly wind and solar power, which now account for a substantial share of its electricity generation. The Russia-Ukraine war has posed significant challenges to the German energy transition, disrupting natural gas imports and leading to short-term measures such as the temporary reactivation of coal-fired power plants. This geopolitical shift has highlighted the need for Germany to accelerate the adoption of renewable energy and develop robust energy storage solutions to ensure long-term energy security. By 2030, Germany aims to install at least 20 GW of renewable capacity annually and develop 12 GW of energy storage to manage the intermittency of wind and solar power. Despite these challenges, the energy crisis has also created opportunities. The sharp rise in energy prices has incentivized investment in renewable energy and energy efficiency measures. Germany is now actively seeking alternative energy partnerships, strengthening cooperation with China in solar technology and exploring hydrogen collaborations with African nations. These strategic shifts are expected to play a crucial role in shaping the next phase of the Energiewende. This paper examines the evolving challenges and opportunities in the German energy transition, focusing on key aspects such as the expansion of renewable energy, energy storage solutions, and policy adjustments needed to navigate the changing energy landscape.

This study explored underground biomethanation as a means to achieve carbon neutrality and promote carbon circular utilization by methanating CO₂ and hydrogen-rich industrial waste gas in depleted natural gas reservoirs (MECHIG). This approach not only aids the development of carbon capture, utilization, and storage (CCUS) technologies, but also effectively processes industrial waste gas, thereby reducing pollutant emissions. In order to verify the feasibility of the MECHIG concept, this study builds upon the analysis of the MECHIG process overview and employs the net present value (NPV) analysis method to investigate its economic viability. Additionally, the study conducts a sensitivity analysis on six factors, namely methanation efficiency, facility site investment, hydrogen content in waste gas, natural gas prices, operation and maintenance (O&M) investment, and CO₂ capture and injection prices. The results indicate the following: (1) Under the baseline scenario, the NPV of the MECHIG concept is approximately CNY 5,035,100, which suggests that the concept may be economically viable. (2) The fluctuation in natural gas prices has the most significant impact on NPV, followed by facility site investment and methanation efficiency. In contrast, the variations in hydrogen content in waste gas, O&M investment, and CO₂ capture and injection prices have relatively smaller effects on NPV. (3) To ensure the economic feasibility of the concept, the acceptable fluctuation ranges for the factors of methanation efficiency, facility site investment, hydrogen content in waste gas, natural gas prices, O&M investment, and CO₂ capture and injection prices are −16.78%, 5.44%, −32.14%, −4.70%, 14.86%, and 18.56%, respectively.

The rapid retirement of electric vehicle (EV) batteries presents both a challenge of resource management and an opportunity for carbon mitigation. An Artificial Intelligence (AI)-driven framework is introduced that couples high-accuracy capacity forecasting with a dynamic life cycle carbon model (LCCO ₂ ), enabling intelligent end-of-life decision-making and large-scale repurposing. Analysis of real-world field data from commercial EVs shows that data-driven retirement strategies extend battery service life beyond conventional fixed thresholds, increase usable energy output, and improve classification accuracy of safety margins. Integration into the LCCO ₂ model indicates reductions of 14.3% in average life cycle carbon intensity, alongside substantial per-battery CO ₂ savings, without compromising operational safety. At scale, projections suggest that second-life deployment of retired EV batteries could deliver tens of tens of millions of metric tons of CO ₂ mitigated annually in China and the European Union by mid-century, thereby contributing directly to both regions’ carbon neutrality pathways. These findings highlight a scalable strategy that unites predictive modelling with carbon accounting, advancing the circular economy of EV batteries. Graphical Abstract