Search Results (66)

With the requirement of energy decarbonization, natural gas (NG) and hydrogen (H₂) become increasingly important in the world’s energy landscape. The liquefaction of NG and H₂ significantly increases energy density, facilitating large-scale storage and long-distance transport. However, conventional liquefaction processes mainly adopt electricity-driven compression refrigeration technology, which generally results in high energy consumption and carbon dioxide emissions. Absorption refrigeration technology (ART) presents a promising avenue for enhancing energy efficiency and reducing emissions in both NG and H₂ liquefaction processes. Its ability to utilize industrial waste heat and renewable thermal energy sources over a large temperature range makes it particularly attractive for sustainable energy practices. This review comprehensively analyzes the progress of ART in terms of working pairs, cycle configurations, and heat and mass transfer in main components. To operate under different driven heat sources and refrigeration temperatures, working pairs exhibit a diversified development trend. The environment-friendly and high-efficiency working pairs, in which ionic liquids and deep eutectic solvents are new absorbents, exhibit promising development potential. Through the coupling of heat and mass transfer within the cycle or the addition of sub-components, cycle configurations with higher energy efficiency and a wider range of operational conditions are greatly focused. Additives, ultrasonic oscillations, and mechanical treatment of heat exchanger surfaces efficiently enhance heat and mass transfer in the absorbers and generators of ART. Notably, nanoparticle additives and ultrasonic oscillations demonstrate a synergistic enhancement effect, which could significantly improve the energy efficiency of ART. For the conventional NG and H₂ liquefaction processes, the energy-saving and carbon emission reduction potential of ART is analyzed from the perspectives of specific power consumption (SPC) and carbon dioxide emissions (CEs). The results show that ART integrated into the liquefaction processes could reduce the SPC and CE by 10~38% and 10~36% for NG liquefaction processes, and 2~24% and 5~24% for H₂ liquefaction processes. ART, which can achieve lower precooling temperatures and higher energy efficiency, shows more attractive perspectives in low carbon emissions of NG and H₂ liquefaction. Full article

To improve traffic efficiency, adaptive traffic signal control (ATSC) systems have been widely developed. However, few studies have proactively optimized the air environmental issues in the development of ATSC. To fill this research gap, this study proposes an optimized ATSC algorithm to take into consideration both traffic efficiency and decarbonization. The proposed algorithm is developed based on the deep reinforcement learning (DRL) framework with dual goals (DRL-DG) for traffic control system optimization. A novel network structure combining Convolutional Neural Networks and Long Short-Term Memory Networks is designed to map the intersection traffic state to a Q-value, accelerating the learning process. The reward mechanism involves a multi-objective optimization function, employing the entropy weight method to balance the weights among dual goals. Based on a representative intersection in Changsha, Hunan Province, China, a simulated intersection scenario is constructed to train and test the proposed algorithm. The result shows that the ATSC system optimized by the proposed DRL-DG results in a reduction of more than 71% in vehicle waiting time and 46% in carbon emissions compared to traditional traffic signal control systems. It converges faster and achieves a balanced dual-objective optimization compared to the prevailing DRL-based ATSC. Full article

Increased demand for decarbonization and renewable energy has led to increasing interest in engineered subsurface storage systems for large-scale carbon reduction and energy storage. In these applications, a working fluid (CO₂, H₂, air, etc.) is injected into a deep formation for permanent sequestration or seasonal energy storage. The heterogeneous nature of the porous formation and the fluid–rock interactions introduce complexity and uncertainty in the fate of the injected component and host formations in these applications. Interactions between the working gas, native brine, and formation mineralogy must be adequately assessed to evaluate the efficiency, risk, and viability of a particular storage site and operational regime. This study reviews the current state of knowledge about coupled geochemical–geomechanical impacts in geologic carbon sequestration (GCS), underground hydrogen storage (UHS), and compressed air energy storage (CAES) systems involving the injection of CO₂, H₂, and air. Specific review topics include (1) existing injection induced geochemical reactions in these systems; (2) the impact of these reactions on the porosity and permeability of host formation; (3) the impact of these reactions on the mechanical properties of host formation; and (4) the investigation of geochemical-geomechanical process in pilot scale GCS. This study helps to facilitate an understanding of the potential geochemical–geomechanical risks involved in different subsurface energy storage systems and highlights future research needs. Full article

To reach climate neutrality by 2050, a goal that the European Union set itself, it is necessary to change and modify the whole EU’s energy system through deep decarbonization and reduction of greenhouse-gas emissions. The study presents a current insight into the global energy-transition pathway based on the hydrogen energy industry chain. The paper provides a critical analysis of the role of clean hydrogen based on renewable energy sources (green hydrogen) and fossil-fuels-based hydrogen (blue hydrogen) in the development of a new hydrogen-based economy and the reduction of greenhouse-gas emissions. The actual status, costs, future directions, and recommendations for low-carbon hydrogen development and commercial deployment are addressed. Additionally, the integration of hydrogen production with CCUS technologies is presented. Full article

The Green Deal, a cornerstone of the European Union’s climate goals, sets out to achieve a substantial 55% reduction in greenhouse gas emissions by 2030 compared to 1990 levels. The EU’s decarbonization strategies revolve around three pivotal avenues. First, there is a focus on enhancing energy efficiency and decreasing the energy intensity of economies. Second, concerted efforts are made to diminish the reliance on fossil fuels, particularly within industrial sectors. Lastly, there is a deliberate push to augment the share of renewable energy sources in the final energy consumption mix. These measures collectively aim to propel the decarbonization of EU economies, establishing EU member countries as global leaders in implementing these transformative processes. This manuscript seeks to evaluate the efficacy of three primary decarbonization strategies adopted by EU economies, namely the enhancement in energy efficiency, the promotion of renewable energy consumption and the reduction in fossil fuel consumption. The objective is to discern which strategies wield a decisive influence in achieving decarbonization goals across EU countries. The analysis encompasses all 27 member states of the European Union, spanning from 1990 to 2022, with data sourced from reputable outlets, including Eurostat, Our World in Data and the Energy Institute. Research findings underscore that, in the realm of decarbonization policies, statistically significant impacts on carbon dioxide emission reduction are attributable to the strategies of improving energy efficiency and augmenting the share of renewables in energy consumption across almost all EU countries. Conversely, the strategy with the least impact, embraced by a minority of EU member states, revolves around diminishing the share of fossil fuels in primary energy consumption. This approach, while statistically less impactful, is intricately linked with transitioning the economies toward renewable energy sources, thus playing a contributory role in the broader decarbonization landscape. The uniqueness of this research lies not only in its discernment of overarching trends but also in its fervent advocacy for a comprehensive and adaptive approach to EU decarbonization policy. It underscores the enduring significance of prioritizing energy efficiency, endorsing the integration of renewable energy and acknowledging the distinctive dynamics inherent in diverse regions. The study accentuates the necessity for nuanced, region-specific strategies, challenging the conventional wisdom of a uniform approach to decarbonization. In doing so, it accentuates the critical importance of tailoring policies to the varied energy landscapes and transition strategies evident in different EU member states. Full article

This research explores the role landscape architects can play in shaping renewable energy infrastructure in the Southwest United States. Conventional energy development often neglects the impacts on landscapes and communities, resulting in community frustration and project terminations. To address this issue and tackle the need for decarbonization, the Southwest Regional Virtual Workshop was convened to foster co-creation and generate innovative ideas for new energy solutions. The Southwest Regional Virtual Workshop (SRVW) aimed to unite landscape architects, architects, engineers, and energy professionals to craft place-based, at-scale, and environmentally sensitive solutions. Key insights from this study demonstrate landscape architects have the capacity to help transform renewable energy projects into attractive, engaging, and productive infrastructure. Their expertise in community engagement, site-specific design, and interdisciplinary collaboration positions them as ideal designers for energy landscapes that go beyond mere functionality. By adopting a landscape-centric approach, landscape architects can help seamlessly integrate energy infrastructure with the environment and aesthetics to gain steadfast community support. Harmonizing functionality with visual appeal can instill a deep sense of pride and ownership among community members, ultimately fostering increased acceptance of renewable energy development. In conclusion, landscape architects can expand upon their expertise to include energy and help create projects that align with the values of local communities and contribute to a resilient energy future. Full article

Following the trend of transport decarbonization, biodiesel has become a promising alternative fuel option. Its production includes multiple steps, all of which can be time-consuming and energy intensive. Improving any of these steps could bring considerable environmental and economic benefits. The utilization of deep eutectic solvents (DESs) for glycerol extraction from crude biodiesel has predominantly been explored as a batch process. This work provides insight into continuous column extraction. Different waste cooking oils were used to produce biodiesel via transesterification with methanol, and the selective solvent for purification was DES choline chloride–ethylene glycol (1:2.5, mol.). A laboratory Karr column at different pulsation frequencies and DES to biodiesel mass ratio was used for extraction. Plate material (steel and 3D printed PETG) and geometry influence on the efficiency of extraction were investigated. Contact angle measurement was used to measure the surface free energy of steel and PETG and the spreading ability of biodiesel and DESs on both materials. Extraction efficiency was analyzed by several analytical techniques. Higher efficiency was observed with steel plates of a triangular pitch hole arrangement. Increasing the mixing intensity and DES to biodiesel mass ratio further increased the efficiency of extraction. Full article

In many countries, depending on climatic conditions and the energy performance of buildings, the built stock is highly energy-consuming and constitutes a main source of greenhouse gas emissions. This is particularly true for Europe, where most of the existing buildings were built before 2001. For this reason, EU policies have focused on the Deep Energy Renovation Process of the residential building stock as the mainstream way for its decarbonization strategy by 2050. Based on a broad investigation of seven EU local retrofitting markets carried out within the H2020 re-MODULEES project, this paper defines a holistic methodology for understanding and facing the complexity of the renovation market and its inner constraints. Thanks to systematic surveys and the activation of stakeholders’ core groups (re-LABs), the main market barriers (cultural, social, technical, processual, and financial) were explored. Through a bottom-up clustering approach and vote analysis, a relevance classification of constraints of each pilot market and a detailed scenario of the most relevant market constraints at the European level were provided. This scalable methodology offers the baseline necessary for shaping more effective, cooperative, and tailored-made policies aimed at overcoming the current limitations to the full deployment of the Deep Energy Renovation Process (DERP) across the European markets. Full article

The rapid fall in the cost of solar photovoltaics and wind energy offers a pathway to the deep decarbonization of energy at an affordable price. Off-river pumped hydro energy storage and batteries provide mature and large-scale storage to balance variable generation and demand while minimizing environmental and social impacts. High-voltage inter-regional interconnection and dispatchable capacity (existing hydro and geothermal) can help balance supply and demand. This work investigates an Indonesian energy decarbonization pathway using mostly solar photovoltaics. An hourly energy balance analysis using ten years of meteorological data was performed for a hypothetical solar-dominated Indonesian electricity system for the consumption of 3, 6 and 10 megawatt-hours (MWh) per capita per year (compared with current consumption of 1 MWh per capita per year). Pumped hydro provides overnight and longer storage. Strong interconnection between islands was found to be unnecessary for Indonesia, contrary to findings from similar modelling in countries at higher latitudes. Storage requirements for power and energy were found to be smaller than three kilowatts and 30–45 kilowatt-hours per person, respectively. Introducing gas turbines (burning hydrogen or synthetic methane) contributing around 1% of annual generation reduced the levelized cost of electricity (LCOE) by 14% and halved the storage requirements by allowing the system to ride through prolonged cloudy periods at lower cost. This work showed that Indonesia’s vast solar potential combined with its vast capacity for off-river pumped hydro energy storage could readily achieve 100% renewable electricity at low cost. The LCOE for a balanced solar-dominated system in Indonesia was found to be in the range of 77–102 USD/megawatt-hour. Full article

Liquefied natural gas (LNG) is widely regarded as the midterm solution toward zero-carbon transportation at sea. However, further applications of gas engines are challenging due to their weak dynamic load performance. Therefore, the comprehension of and improvements in the dynamic performance of gas-engine-based power systems are necessary and urgent. A detailed review of research on mechanisms, modeling, and optimization is indispensable to summarize current studies and solutions. Developments in engine air-path systems and power system load control have been summarized and compared. Mechanism studies and modeling methods for engine dynamic performance were investigated and concluded considering the trade-off between precision and simulation cost. Beyond existing studies, this review provides insights into the challenges and potential pathways for future applications in decarbonization and energy diversification. For further utilization of clean fuels, like ammonia and hydrogen, the need for advanced air–fuel ratio control becomes apparent. These measures should be grounded in a deep understanding of current gas engines and the combustion characteristics of new fuels. Additionally, the inherent low inertia feature of electric power systems, and consequently the weak dynamic performance when adopting renewable energies, must be considered and studied to ensure system reliability and safety during transient conditions. Full article

Since nuclear energy is crucial in the decarbonization of the energy supply, one hurdle to remove is the handling of high-level radioactive waste (HLW). Disposal of HLW in a deep geological repository has long been deemed a viable permanent option. In the design of a deep geological repository, compacted bentonite is the most commonly proposed buffer material. Predicting the long-term chemical evolution in bentonite, which is important for the safety assessment of a repository, has been challenging because of the complex coupled processes. Models for large-scale tests and predictions based on such models have been some of the best practices for such purposes. An 18-year-long in situ test with two dismantling events provided a unique set of chemical data that allowed for studying chemical changes in bentonite. In this paper, we first developed coupled thermal, hydrological, mechanical, and chemical (THMC) models to interpret the geochemical data collected in the in situ test and then extended the THMC model to 200 years to make long-term prediction of the geochemical evolution of bentonite. The interpretive coupled THMC model shows that the geochemical profiles were strongly affected by THM processes such as evaporation/condensation, porosity change caused by swelling, permeability change, and the shape of concentration profiles for major cations were largely controlled by transport processes, but concentration levels were regulated by chemical reactions, and the profiles of some species such as pH, bicarbonate, and sulfate were dominated by these reactions. The long-term THMC model showed that heating prolongs the time that bentonite becomes fully saturated in the area close to the heater/canister; however, once the bentonite becomes fully saturated, high concentrations of ions in bentonite near the heater, which was observed in the field test, will disappear; illitization continues for 50 years but will not proceed further. Full article

Deep-sea decarbonization remains an enigma as the world scrambles to reduce global emissions. This study looks at near-term decarbonization solutions for deep-sea shipping. Pathways are defined, which are appealing to ship owners and major world economies alike. The economic and environmental viability of several of the most advanced near-term technologies for deep-sea decarbonization are revealed. The environmental analysis suggests the necessity of new emission intensity metrics. The economic analysis indicates that the carbon tax could be a great motivator to invest in decarbonization technologies. Standalone decarbonization technologies can provide a maximum of 20% emissions reduction. Hence, to meet IMO 2050 targets of 50% emissions reduction, several solutions need to be utilized in tandem. This study reaches the conclusion that alternative fuels are the crucial step to achieve a net zero carbon economy, although bunkering, infrastructure, and economic hurdles need to be overcome for the widespread implementation of carbon-neutral fuels. Full article

The article presents an analysis of the statistical relationship between the determinants of and barriers to the development of renewable energy sources (RESs) in the macroeconomic system and the development of renewable energy source consumption in individual European Union countries. The article considers four key categories of RES development barriers in the European Union: political, administrative, grid infrastructural, and socioeconomic. The work is based on publicly available historical data from European Union reports, Eurostat, and the Eclareon RES Policy Monitoring Database. The empirical analysis includes all 27 countries belonging to the European Union. The research aimed to determine the impact of all four types of factors, including socioeconomic, on the development of RESs in European Union countries. The analysis uncovered that describing the European Union as a consistent region regarding the speed of renewable energy advancement and the obstacles to such progress is not accurate. Notably, a significant link exists between a strong degree of societal development and the integration of renewable energy sources. In less prosperous EU nations, economic growth plays a pivotal role in renewable energy development. Barriers of an administrative nature exert a notable influence on renewable energy development, especially in less affluent EU countries, while grid-related obstacles are prevalent in Southern–Central Europe. In nations where the proportion of renewable energy sources in electricity consumption is substantial, an excess of capacity in the renewable energy market significantly affects its growth. Full article

The energy sector is responsible for a large share of climate-damaging emissions. Regarding the decarbonization of the energy sector, deep geothermal energy is considered to have high potential, particularly in the area of heat supply. In order to gauge the extent to which heat use from deep geothermal energy can make a positive contribution to climate protection, deep geothermal systems should be appraised using an environmental sustainability assessment. Although electricity generation from deep geothermal power plants has been evaluated in many ways in the literature with respect to its sustainability, no such sustainability evaluations of pure geothermal heat plants have been conducted so far. In order to close this research gap, this study presents a systematic approach that makes it possible to apply suitable sustainability criteria across the individual life stages of deep geothermal heat plants based on life-cycle assessment (LCA) guidelines. To demonstrate the effectiveness of the systematic approach presented here, a planned geothermal heat plant in the Upper Rhine Valley, Germany, serves as an example. Based on the estimated plant parameters and the predicted total heat yield, it was possible to determine, for example, the “energy returned on energy invested” (EROI) of the plant, which was approximately 34, and the specific CO₂ emissions, which were approximately 5.6 g/kWh_th. Full article

Buildings are responsible for approximately 40% of the world’s energy consumption and 36% of the total carbon dioxide emissions. Building occupancy is essential, enabling occupant-centric control for zero emissions and decarbonization. Although existing machine learning and deep learning methods for building occupancy prediction have made notable progress, their analyses remain limited when applied to complex real-world scenarios. Moreover, there is a high expectation for Transformer algorithms to predict building occupancy accurately. Therefore, this paper presents an occupancy prediction Transformer network (OPTnet). We fused and fed multi-sensor data (building occupancy, indoor environmental conditions, HVAC operations) into a Transformer model to forecast the future occupancy presence in multiple zones. We performed experimental analyses and compared it to different occupancy prediction methods (e.g., decision tree, long short-term memory networks, multi-layer perceptron) and diverse time horizons (1, 2, 3, 5, 10, 20, 30 min). Performance metrics (e.g., accuracy and mean squared error) were employed to evaluate the effectiveness of the prediction algorithms. Our OPTnet method achieved superior performance on our experimental two-week data compared to existing methods. The improved performance indicates its potential to enhance HVAC control systems and energy optimization strategies. Full article