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Schroeder's paradox discovered by Schroeder in 1905 refers to the phenomenon that polymers have different maximum water uptake in the liquid and saturated vapor phases. For more than a hundred years, people have often debated whether this phenomenon conforms to thermodynamics. As proton exchange membrane fuel cell (PEMFC) gradually becomes a promising renewable energy utilization device, its impact on the physical properties of the proton exchange membrane has been studied widely. This paper reviews the theory and experiments on Schroeder's paradox over more than 100 years, especially the exploration of perfluorosulfonic acid membranes and PEMFCs in recent decades. Since membrane water content determines the operational performance of the PEMFC, this paper discusses and analyzes the effect of Schroeder's paradox on the PEMFC performance, including mechanical properties, electrical conductivity, and water transport mechanism. The effect of this phenomenon on the non-equilibrium operation of PEMFC has been highlighted, such as cold start-up, because of the different properties of membranes in contact with liquid water and air. This review gives an introduction to critical aspects of Schroeder's paradox to serve governments and organizations to promote the application of PEMFC in different regions. [Display omitted] • Schroeder's paradox in proton exchange membrane fuel cells is reviewed. • Mechanisms and experimental methods of Schroeder's paradox are critically analyzed. • Evaluated the effect of Schroeder's paradox on membrane performance. • The existence of Schroeder's paradox lower freezing point is discussed. • Future research directions of Schroeder's paradox are presented. [ABSTRACT FROM AUTHOR]

Curtailment of distributed photovoltaic (PV) and battery energy storage systems will have significant implications for power system transition around the world. Australia offers a unique case study as it has highest installation rate of distributed-PV and growing fleet of battery energy storage systems. Distributed-PV and battery inverters in Australia are required to exhibit voltage-responsive power-quality response modes to prevent excessive voltage rise caused by increasing day-time energy exports, but these modes can curtail power output and limit the value that can be gained from the renewable energy assets. For the first time in Australia, this paper studies all three inverter power-quality response modes and develops novel algorithms to assess curtailment. The algorithms are applied to a real-world dataset of 1-sec distributed-PV and battery power measurements from 1300 residential households; therefore, data resolution is higher and sample size is larger than previous related studies. Using these datasets, the study compares the experienced curtailment between distributed-PV only sites and distributed-PV coupled with battery sites for the first time. The study investigates and quantifies the energy loss due to curtailment within the South Australia region with over 40% distributed-PV penetration which has the highest uptake in the world. The results show that average curtailment loss was 1.5% for distributed-PV only sites and 0.2% for distributed-PV coupled with battery sites, however, some sites were heavily impacted losing up to 25% of generation. The reasons for the larger curtailment loss were identified as wiring and network connection faults and high voltage set-points at households' respective local substations. Other potential reason for the heavily impacted sites is being located towards the end of the low voltage feeder, however this couldn't be verified due to lack of spatial data. The large variation in curtailed generation across sites raises concerns for system owners and suggests further inquiry into the power-quality response mode design and regulations. The study also examines inverter conformance using real-world operational data for all three power quality response modes for the first time, and the results showed a low rate of conformance according to the Australian Standards and there were various discrepancies in the execution of these modes which raises concerns considering the increasing importance of distributed-PV and battery inverter fleet in supporting network operations and security. The results therefore warrant further investigation into the reasons behind these discrepancies and devising appropriate mechanisms to tighten inverter conformance checks. • Energy curtailment is calculated for D-PV only and D-PV coupled with BESS sites • Average loss due to curtailment is less than 2% of total D-PV generation • Curtailment is greater for D-PV only sites than D-PV coupled with BESS sites • Some sites lose up to 25% of generation due to curtailment • The large variation of curtailment losses across sites raises concerns • Inverters showed low conformance in power quality response mode standards [ABSTRACT FROM AUTHOR]

Regional integrated energy systems (RIES) have garnered increased attention because they highly utilize renewable energy, comprehensive efficiency, and flexible operation. However, the current research on RIESs is mainly based on burning natural gas and supplemented by renewable energy, which will consumes much primary energy and generates corresponding carbon emissions. Therefore, a RIES contained various renewable energy sources and station energy sharing was constructed in this paper. Both the collaborative optimization model, which considered the operating parameters and system configuration, and the hierarchical optimization model, which optimizes the equipment configuration at the upper layer and the operational parameters at the underlayer, were constructed, respectively. Taking a multi-function low-carbon park as an example, the isolated integrated energy system (IIES) and RIES performances were explored. Finally, the operation cost, carbon emission, and interactive power in the separated production system, IIES and RIES were analyzed and discussed from a long-short time scale perspective. The results showed that the carbon emission, interactive power, and energy supply cost of the RIES's unit area are 7.62 kg/m2, 10.07 kWh/m2, and 40.55 CNY/m2, respectively. Long time scale perspective (Years or months), RIESs could significantly reduce carbon emissions and interactive power. However, on a short time scale viewpoint (Hours), the system's instantaneous energy conservation and carbon reduction effect was general; meanwhile, the maximum grid-connected power in IIES and RIES was 2617.7 and 2712.0 kW, respectively. • A RIES is constructed integrating various renewable energy sources and energy sharing between stations. • Collaborative and hierarchical optimization is used to solve the complex RIES optimization problem. • Carbon emission and interactive power of the unit area for the RIES are 7.62 kg/m2 and 10.07 kWh/m2. • The maximum grid-connected power of IIES and RIES is 2617.7 and 2712.0 kW, respectively. [ABSTRACT FROM AUTHOR]

Implementing Nature-Based Solutions (NBS) is a promising way to reduce building energy demand and facilitates the achievement of United Nations Sustainable Development Goal 7, as they provide shading, evapotranspiration cooling and other influences on buildings. Although this field has attracted much attention, uncertainty persists regarding the potential of different NBS types to impact building energy demand in different climate conditions. To clarify this uncertainty, 101 papers were studied based on the Web of Science and Scopus databases. The current status analysis explored the development state of this field. Building energy performance analysis evaluated the potential reduction in cooling and heating energy in different climates by applying different NBS types at building scale. The review revealed that the cooling energy saving potential of NBS varies from 3% to 90%, while the potential reduction in heating energy demand ranges from 0.58% to 60%. The extent of the reduction in both cases is dependent on the NBS type and climate. Notably, some NBS types may lead to an increase in heating energy demand by between 5.9% and 25% in climates with short and mild winters. This review found that maximizing the energy-saving potential of NBS requires a comprehensive consideration of multiple factors rather than maximizing an individual factor. Further, most studies in this field have only concentrated on a few NBS types and climate zones, resulting in significant differences in research depth among different NBS categories. Future work should focus on neglected NBS types and climates to fully understand their energy-saving potential. • Different types of nature-based solutions regarding building energy demand reduction were reviewed. • Climate zone dependency of NBS impact on building energy demand was analyzed and quantified. • Influential factors to optimize the impact of nature-based solutions on building energy performance were identified. • Research gaps regarding nature-based solutions impact on building energy demand were identified. [ABSTRACT FROM AUTHOR]

Lead halide perovskite-based solar cells have developed significantly over the past few years and have proven to be suitable for photovoltaic applications thanks to several intriguing characteristics, including low cost, high absorption coefficient, long carrier diffusion length, low exciton binding energies, etc. However, the toxicity and stability of lead seemed to be the main challenges; therefore, a replacement was required. As an alternative, lead-free mixed organic-inorganic halide perovskite has revolutionized science and technology. The power conversion efficiency of these lead-free perovskite-based solar cells has dramatically increased to ∼20%, given the well-known uses of solar cells. As a result, due to their efficiency and low-cost processing, these are more promising and comparable with silicon-based PV applications. Excluding lead, due to its highly toxic and low stability nature, other replacements such as Sn, Ge, Bi, In, Sb, etc., are already considered suitable clients for different applications. Formamidinium, methylammonium, and other larger-sized organic cations demonstrated their compatibility with flexible other dimensional structures such as 2D, 1D, and 0D for enhancing stability. The diverse synthesis procedure make the preparation of these lead-free mixed organic metal inorganic halide much easier. Apart from various optoelectronic applications, the variation of the A and B cation sites led to different other catalytic, sensing, and energy applications making these materials suitable for bi/multi-functional applications. This review article has focused on the various properties and related preparation processes of these hybrid mixed halide perovskites. Different applications of these hybrid materials were also reviewed and summarized, including bi/multi-functional applications. This paper provides an overall performance of mixed hybrid halide perovskites from synthesis through multifunctional applications. In the course of finding an alternative to lead to get rid of its toxicity and stability issues, nowadays, researchers are motivated toward the hybrid mixed organic-inorganic metal halide perovskites. This tends to achieve more stabilized, environmentally friendly, and resonance characteristics perovskites for device applications. Utilizing different organic cations at place A lead to easy tuning in dimensionality, more stability, and bifunctional applications. [Display omitted] • Current status and advances on the lead free mixed halide perovskites materials. • Study on different lead free mixed organic-inorganic halide perovskite (LMHP) and respective optoelectronic properties. • Discussion on various synthesis procedure based on dimensionality of these LMHPs. • Recent progress in different sectors of solo as well as bifunctional applications and corresponding future aspects. [ABSTRACT FROM AUTHOR]

The building sector accounts for over one-third of global energy consumption and a significant share of carbon emissions. Improving building energy efficiency, particularly in the tropics, where most of the future development is foreseen, is thus crucial. One of the main factors that determine building energy performance is the building envelope. This paper presents a comprehensive review of the impact of several envelope design variables, such as thermal, optical, physical, and geometrical, on the energy performance of buildings in the tropics. A correlational analysis that elaborates on the effectiveness of each of these measures is discussed in detail. The findings indicate that insulation, glazing properties, and Window-to-wall ratio (WWR) are promising solutions for improving energy efficiency in tropical buildings. Among these, insulating the building envelope has the most significant impact on energy savings. The variables of building orientation and the thermal mass of building materials have the least influence on total energy consumption. The latter exhibits complex effects in regions characterized by hot-humid climates. An optimized design in cooling-dominated climates should have a large aspect ratio, a higher WWR in the north and south facades, and an ideal shading system. With all variables combined and appropriate ventilation, a building can save 35% of annual energy and up to 60% in some cases. This study further reveals that available research on the effect of building shape and the context of surrounding built environment on energy consumption remains limited. • Combining all envelope variables can provide annual average savings of 35%. • Average savings can drop by over 20% without insulation. • Insulation, WWR, and glazing type are the most promising solutions in Tropics. • Use insulation based on WWR, shading, thermal mass, and glazing type. • Shading, glazing, SHGC, and WWR have been mainly studied together. [ABSTRACT FROM AUTHOR]

The construction sector is a key actor in fighting climate change. A clear and comprehensive accounting of its carbon emission responsibility is the basis for effective emission mitigation actions. The intersectoral and interregional trade of the construction sector complicates emission responsibility allocation. Neglecting such trade flows or measuring them from a single perspective may cause the sector's emission status to be misinterpreted. Hence, based on the environmentally extended multiregional input-output model, this paper establishes the construction sector's multiprinciple emission responsibility accounting framework and conducts multiple accounting for China's construction sector. The emission distribution and transfer across regions and sectors are systematically revealed, and various accounting principles, regional clusters, and corresponding policy implications are compared and discussed. The results show significant differences in the emission responsibilities of the construction sector under different principles, indicating that the choice of principles will greatly affect the determination of responsibility and corresponding policy priorities, which requires careful consideration. The emission responsibilities in different regions also have notable heterogeneity under each principle and are further clustered into three main emission patterns, suggesting that classified and targeted emission mitigation strategies should be adopted. The emission transfer analysis demonstrates that the construction sector is a typical end-of-chain sector with high emission-pulling effects on upstream industries and tiny emission-pushing effects on downstream industries, resulting in varied incentive impacts under each principle. Overall, this study contributes extensive insights into the emission responsibility of the construction sector, supporting common but differentiated emission reduction targets and policy settings. • A multiprinciple carbon accounting model for the construction sector is developed. • The emission distribution and transfer across regions and sectors are explored. • Accounting principles, emission patterns, and policy implications are compared. • Great disparities under various principles alert multiperspective strategy setting. • Regional heterogeneity in emissions emphasizes differentiated mitigation actions. [ABSTRACT FROM AUTHOR]

Sugarcane mills currently use sugarcane bagasse to cogenerate heat and electricity, supplying the process with mechanical, thermal and electrical energy. Some of these plants are able to produce surplus electricity to export to the national grid. With the improvement in collection techniques, sugarcane straw has also become available and has been used in some mills as fuel for steam boilers, mixed with sugarcane bagasse. However, due to different traits compared to bagasse, the use of sugarcane straw may pose additional problems of incrustation and corrosion on heat exchange surfaces. Several alternatives and technologies have been studied and tried out in order to increase the production of surplus electricity. Among others, biomass integrated gasifier–gas turbine combined cycle (BIGCC) is a promising technology. However, several attempts have resulted in failure, whether on a pilot or industrial scale. Biomass gasification integrated with internal combustion engines can become an opportunity for generation of small power capacity (<15 MW) and integrated to sugarcane mills. This paper analyzes the difficulties and barriers to increasing electricity generation in the sugarcane industry through studies, projects and experimental and industrial-scale installations that have already been carried out. • Bagasse and cane straw show great potential for electricity generation. • Sugarcane industry in Brazil accounts for 6.4% of the electricity generated. • Biomass integrated gasification and combined cycle can increase electricity generation. • Technological and economic challenges are major barriers to the development of BIGCC. • No BIGCC project already implemented is currently in commercial operation. [ABSTRACT FROM AUTHOR]

Potential carbon neutrality of the global trucking, shipping and aviation sectors by 2050 could be achieved by substituting fossil fuels with renewable hydrogen and synthetic fuels. To investigate the economic impact of fuel substitution over time, a holistic cost model is developed and applied to three case studies in Norway, an early adopter of carbon-neutral freight transport. The model covers the value chains from local electricity and fuel production (hydrogen, ammonia, Fischer–Tropsch e-fuel) to fuel consumption for long-haul trucking, short-sea shipping and mid-haul aviation. The estimates are internally consistent and allow cross-mode and cross-fuel comparisons that set this work apart from previous studies more narrowly focused on a given transport mode or fuel. The model contains 150 techno-economic parameters to identify which components along the value chains drive levelized costs. This paper finds a cost reduction potential for renewable fuels of 41% to 68% until 2050, but carbon-neutral transport will suffer asymmetric cost disadvantages. Fuel substitution is most expensive in short-sea shipping, followed by mid-haul aviation and long-haul trucking. Cost developments of electricity, direct air capture of carbon, vehicle expenses, and fuel-related payload losses are significant drivers. [Display omitted] • Levelized costs of renewable fuels in road, sea and air freight are estimated. • A new holistic cost model allows cross-mode and cross-fuel comparison. • Renewable fuels have a cost reduction potential of 41% to 68% until 2050. • Fuel substitution is most expensive in shipping, followed by aviation and trucking. • Reducing fuel-related payload losses is a significant cost lever. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive taxonomy and assessment of existing and emerging space cooling technologies in Europe. The study aims to categorize 32 alternative space cooling technologies based on eight scouting parameters (physical energy form, basic working/operating principle, refrigerant or heat transfer medium, phase of the working fluid, specific physical process/device, type of space cooling technology, fuel type and technology readiness level) and evaluate their key characteristics and development trends. The increasing demand for space cooling in Europe necessitates a thorough understanding of these technologies and their potential for energy efficiency. The majority of space cooling demand in Europe is currently met by conventional vapour compression systems, while a small portion is covered by thermally-driven heat pumps. The study reveals that several alternative space cooling technologies show promise for energy-efficient cooling but are not yet competitive with vapour compression systems in terms of efficiency and cost in the short-term and medium-term. However, technologies such as membrane heat pumps, thermionic systems, thermotunnel systems, and evaporative liquid desiccant systems demonstrate cost-competitiveness and energy efficiency in specific applications. The findings highlight the need for further research and development to improve the efficiency, costs, and market competitiveness of alternative space cooling technologies. The study also emphasizes the importance of policy support and the urgency to reduce greenhouse gas emissions, which can drive the adoption and advancement of sustainable cooling solutions. • The study provides a taxonomy of 32 space cooling technologies in the EU • Eight scouting parameters are discussed to categorize the space cooling technologies • Most of the alternative technologies have potential but can't compete in efficiency and cost • Only ten of the alternative cooling technologies have a TRL between 5 and 9 • Membrane heat pumps, thermionic systems, thermotunnel systems, and evaporative liquid desiccant systems are cost-competitive and energy-efficient in certain applications. [ABSTRACT FROM AUTHOR]

Power converters and motor drives are playing a significant role in the transition towards sustainable energy systems and transportation electrification. In this context, rich diversity of new power converters and motor drive products are developed and commissioned by the industry every year. However, to achieve efficient, reliable and stable operation of power converter and drive systems, there are challenges in condition monitoring, fault diagnosis, lifecycle estimation, stability evaluation and control. Online learning is an emerging technology that can serve as a powerful remedy to these challenges. This paper aims to provide a systematic study of algorithms, implementations, and applications of online learning for control and diagnostics in the area of power converters and drives. First, online learning problems are formulated for condition monitoring, fault detection, online stability assessment, model predictive control for power converter and drive applications. Next, guidelines are provided about how to develop online learning models and algorithms for these applications. Practical case studies are presented with experimental demonstrations. Finally, challenges and future opportunities are discussed about online learning for power converter and drive applications. • A comprehensive overview of online learning for power converter and drive applications. • Applications in condition monitoring, fault detection, stability assessment and control. • Formulation of online learning problems for power converter and drive applications. • Guideline about how to develop online learning models and algorithms for the applications. • Practical case studies with experimental demonstrations. • Challenges and future works about online learning for power converter and drive applications. [ABSTRACT FROM AUTHOR]

Solar radiation, being an ample source of renewable energy can be captured and stored in the form of latent heat using phase change materials (PCM) to make the environment sustainable. Furthermore, form stable phase change materials (FSPCM) are preferred due to their light weight and desirable thermal characteristics such as higher thermal conductivity, molten PCM holding capacity etc. In this regard, a porous matrix is utilized as a support to hold PCM. A thorough investigation on mechanism and methods of hydrophilic and hydrophobic modification of the porous medium has been carried out in this review paper. Water contact angle (WCA) is an influential parameter that governs hydrophilicity/hydrophobicity. Modified hydrophilic surfaces accept a wide range of aqueous solutions with increased chemical resistance while hydrophobically modified surfaces are self-cleaning and anti-corrosive. Moreover, reversible transition of wetting state can be attained in carbon-based materials like graphene, polycarbonate etc., which helps to prevent leakage and accomplish superior impregnation of PCM. The influence of hydrophilic and hydrophobic modification of the porous matrix on the thermal performance of the FSPCM and their applications have been deliberated in this review as per the available scientific literatures. • Significance of hydrophilic/hydrophobic modification of porous matrix with regard to form-stable phase change materials have been thoroughly investigated. • Water contact angle is a significant parameter in transforming surface characteristics of the porous medium, suitable to the application. • Methods of hydrophilic and hydrophobic modification of porous medium and supporting mechanisms have been demonstrated. • Novel form-stable phase change materials fabricated with aerogels and adaptable wetting surfaces as porous medium have gained attention on account of their thermal properties. • Applications of hydrophilic/hydrophobic altered porous medium along with phase change materials is predominant in low-medium temperature systems. • In accordance with the scientific literatures, thermal properties of form-stable phase change materials improved with surface altered porous medium. [ABSTRACT FROM AUTHOR]

Demand-side management (DSM) can transfer the dynamic fluctuations of load to match the renewable energy sources and realize the interaction of source-load. In most existing combined cooling heating and power (CCHP) system scheduling, user-side and system-side resources are independently optimized to achieve optimum economic performances without efficiently combining resources. In this paper, the devices with adjusted loads on the system-side and the user-side are integrated to construct generalized energy storage (GES) model, including traditional flexible resources, batteries, electric vehicles, cooling and heating load response, and electro-to-thermal conversion devices. Then, the GES model is integrated into the system for optimization including economy, load fluctuation, energy efficiency, and exergy efficiency. A case study demonstrates the application of the proposed method. The scheduling results of four DSM cases under different objectives are comprehensively obtained and compared. The optimized schemes are assessed in multi-dimension decision-making method and the effects of objective weights on decision results are analyzed. The simulation results illustrate that the load variation is decreased by 54% to obtain a smooth electrical load, resulting in the stable operation of equipment and improving the security and stability of the CCHP system. The exergy efficiency, energy efficiency, and economy performances through the DSM optimization are improved by up to 8.7%, 2.5%, and 2.4%, respectively. The system optimized with the objective of load fluctuation achieves the highest score in the TOPSIS decision-making scenarios and has the best comprehensive performance. [Display omitted] • A multi-dimension day-ahead scheduling optimization model is proposed. • The transformation model between rigid and flexible electric load is built. • The multi-dimensional performance indicators are applied to demand response. • The load variance index has the most prominent performance improvement, 54%. • The exergy efficiency, energy efficiency and cost boosted by 8.7%, 2.5% and 2.4%, respectively. [ABSTRACT FROM AUTHOR]

The wastewater sector accounts for up to 7 and 10% of anthropogenic CH 4 and N 2 O emissions, respectively. Nowadays wastewater treatment plants are going through a paradigm shift to approach a net-zero carbon condition. Numerous ongoing measures have taken place to identify the sources of greenhouse gases and minimize the carbon footprint. This paper systematically reviews all known practices leading towards net-zero carbon wastewater treatment. The greenhouse gas emissions from the wastewater sector are identified and carbon footprint quantification tools, such as reliable models and emission factors are compared. The direct process emissions can contribute to over 60% of the carbon footprint in wastewater treatment plants, while around 30% of the carbon footprint is due to energy-related indirect emissions. Therefore, greenhouse gas mitigation via process optimization and energy usage in wastewater treatment plants are comprehensively described. The implantation of novel nitrogen removal processes can reduce both greenhouse gas emissions and energy consumption. Other techniques such as source separation systems can potentially allow mitigation of N 2 O emissions by 60% while avoiding energy-intensive nitrogen fertilizer production. Nutrient recovery methods are another approach which offer negative value for the net carbon footprint. Recovering N 2 O for energy production is a promising method which can lead to both direct and indirect carbon footprint reductions. Ultimately, to achieve full decarbonization any remaining emissions need to be offset, including carbon footprint of chemicals usage and transportation. [Display omitted] • Wastewater sector is going through a paradigm shift towards decarbonization • GHG emission hotspots are identified and emission factors are reviewed • WWTPs may be responsible for approximately 5% of total GHG emissions • Direct emissions can contribute to >60% of the carbon footprint in WWTPs • Process modifications and energy optimization play key roles towards net-zero WWTPs [ABSTRACT FROM AUTHOR]

The shipping sector is facing increasing pressure to implement clean fuels and drivetrains. Especially hydrogen-fuel cell drivetrains seem attractive. Although several studies have been conducted to assess the carbon footprint of hydrogen and its application in ships, their results remain hard to interpret and compare. Namely, it is necessary to include a variety of drivetrain solutions, and different studies are based on various assumptions and are expressed in other units. This paper addresses this problem by offering a three-step meta-review of life cycle assessment studies. First, a literature review was conducted. Second, results from the literature were harmonized to make the different analyses comparable, serving cross-examination. The entire life cycle of both the fuels and drivetrains were included. The results showed that the dominant impact was fuel use and related fuel production. And finally, life-cycle hot spots have been identified by looking at the effect of specific configurations in more detail. Hydrogen production by electrolysis powered by wind has the most negligible impact. For this ultra-low carbon pathway, the modes of hydrogen transport and the use of specific materials and components become relevant. [Display omitted] • For shipping, hydrogen-fuel cell drivetrains seem attractive as low carbon options. • Existing LCA studies on this topic are hard to interpret and compare. • In this study, a 3 step meta-review of LCAs has been conducted. • Hydrogen production by electrolysis powered by wind using PEMFC has the least impact. • For this low-carbon option, fuel transport and material use become relevant. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines have arisen as a promising option to access massive wind energy resources in deep water, where the existing fixed-type offshore wind turbine is no longer practical. However, due to the nature of the oceanic environmental conditions, large uncertainties are involved in the aerodynamic/hydrodynamic calculations, which are coupled with those within the structures and materials. This not only threatens its reliability but also drastically increases the manufacturing cost of floating offshore wind turbines. To understand the uncertainty within the system and properly predict its reliability, first, the uncertainties involved in the environments and subsystems need to be defined. Therefore, this paper aims to provide an extensive review of the uncertainty models involved in the structural design of floating offshore wind turbines. The presented uncertainties within the structures include those inherent in the material and geometrical/mechanical properties of the wind turbine, floating structures, and mooring lines. The uncertainties within hydrodynamics include empirical parameters and nonlinearities involved with the hydrodynamics modeling of the floaters. Within the environmental loads, the parameter uncertainties as well as the randomness of wind and wave loads are presented. The uncertainties growing over time caused by fatigue, corrosion, and climate hazards are also discussed. In addition, the correlation between the random variables, such as the correlation of the wind and wave, is presented. Finally, the method of treating those uncertainties is discussed, including the probabilistic model which incorporates the uncertainties and the correlations between the random variables, as well as modeling errors. • Various sources and types of uncertainties that affect the structural reliability of floating offshore wind turbines are presented. • An extensive review of the uncertainty models for the parameters involved in the estimation of the reliability of the floating offshore wind turbines is provided. • The correlations between the parameter uncertainties are discussed when applicable. • Growing uncertainties over the lifecycle, including those caused by fatigue and corrosion, are discussed along with their impact on structural reliability. • Various existing reliability analysis methods, that can be used for the floating offshore wind turbine structures are reviewed and discussed. [ABSTRACT FROM AUTHOR]

This paper provides a review of negative carbon capture technologies. Based on these technologies, here it is proposed an innovative negative emissions power plant combining the generation and storage of energy from biomass, photovoltaic, and concentrated solar power, capturing and recovering CO 2 by producing H 2 or CH 4 as green energy carriers. The main features of the system are i) large-scale energy production system with negative CO 2 emissions; ii) 100% renewable system based on biomass and solar energy with the possibility of integrating other renewables; iii) synergistic integration of processes and systems; iv) recovery of O 2 generated by photovoltaic-driven electrolysis within the process of partial biomass oxycombustion and v) solar-driven limestone calcination. A detailed model of the entire plant is developed to evaluate the integration of the process. The model performance is assessed on an hourly basis throughout the whole year. The base case results show an energy consumption from 1 to 2.1 MJ/kg CO 2 to capture 60–77% of CO 2 emitted from the biomass plant and green methane production of more than 7500 tons/year. The negative emissions associated with the process are -612 kg CO 2 /MWh. It justifies the interest in the proposed negative emissions power plant. [Display omitted] • A synergetic integration of CO2 capture, energy storage and methane production is proposed. • A biomass power plant is considered, resulting in -612 kg CO2/MWh negative emissions. • Solar PV and CSP are integrated into the process to reduce the SPECCA to 1–2.1 kg CO2/MWh. • A large amount of solids storage is required to achieve 70–90% CO2 capture capacity. [ABSTRACT FROM AUTHOR]

Rapidly increasing catastrophic environmental incidents and changes in global climate have compelled researchers to take proactive measures for climate change mitigation. Consequently, reducing greenhouse gas emissions has become one of the most significant global targets. The transportation sector has a massive carbon footprint accounting for 22% of the total carbon dioxide emissions. In this regard, road transport contributes the largest fraction of the total emissions within the transportation sector. Conversely, the railway which is the cleanest form of transportation contributes slightly more than 1% of the total emissions. Moreover, since most of the rail systems are operated by government or private companies, it is relatively convenient to implement policies and replace conventional technology with environmentally friendly ones. This could be achieved by taking certain measures from technical and operational viewpoints for conserving energy to lower the carbon intensity of all transport modalities. Hence, this review paper focuses on investigating the railway sector to encourage a modal shift to the least carbon-intensive option. This study provides a critical review of the past and present rail technologies in terms of the environmental, economic, social, and technical perspectives. Moreover, a comparative assessment of the various locomotive types has been performed. The results reveal that battery-hydrogen hybrid locomotives are the best choice to be considered as a future locomotive technology. Hydrogen locomotives have the potential to be a promising alternative to diesel railway locomotives. However, certain technical barriers need to be overcome to enhance the overall system's performance and reliability to further improve the viability of its deployment in the railway sector. [Display omitted] • A critical review of the various rail technologies is provided through different viewpoints. • The assessment constitutes environmental, economic, social, and technical perspectives. • A decision-support tool for comparison of four rail technologies is also developed. • Battery-hydrogen hybrid locomotive results in the highest score of 1.47. • Standalone hydrogen locomotive results in the second highest score of 1.38. [ABSTRACT FROM AUTHOR]

Biomethane production by anaerobic digestion can significantly contribute to the decarbonation and defossilization of the European energy mix. Although previous estimates have been provided about biomethane potential production in several European countries, they suffer from a coarse evaluation of substrate availability and a lack of spatial resolution. This paper provides a spatially-explicit assessment of the potential for biomethane production in France at a fine spatial resolution (NUTS 4 region) from agricultural biomass (livestock manure, crop residues and cover crops) and sewage sludge. This assessment is based on (i) a fine estimation of substrate availability, particularly for cover crop production, by combining a crop model with spatially-explicit soil and climate databases; (ii) the use of an anaerobic digestion model that predicts biomethane production from agricultural biomass; and (iii) a procedure for optimizing biomethane production while respecting the stoichiometric constraints of the substrate mixture. We found a significant potential for annual biomethane production of 64.1 TWh, mainly from cattle manure, a value that could reach 108.7 TWh through the generalization of cover crops within arable cropping systems. Our results also highlighted the importance of detailed substrate availability data to account for their large spatial variations. Accordingly, we showed that biomethane production was highly variable across the French regions and that crop residues could only partly be used for anaerobic digestion – especially in arable regions – because they lead to excessively dry substrate mixtures. This study helped to identify the most suitable regions for biomethane production and to provide accurate estimates for biomethane development in France. • High-resolution estimate of agricultural biomethane production in France • Biogas production could reach 64.1 TWh/year under current substrate availability • Cover crop generalization could increase biogas production to 108.7 TWh/year • 24–40% of crop residues could not be used due to their stoichiometric composition • Biogas production was highly clustered in both crop- and livestock-oriented regions [ABSTRACT FROM AUTHOR]

Smart charging strategies for electric vehicles (EVs) require as input information such as energy requirement and dwell time. In practice, that information is often not available. However, estimations may be obtained from historical charging behavior. This paper investigates the added value of historical information for EV charging strategies based on real-world EV charging data collected in an office building parking lot with 125 chargers. Furthermore, it provides valuable insights into EV charging behavior at office building parking lots, based on a statistical analysis of the data. The added value of data availability in EV charging strategies for day-ahead planning and real-time operation of office building parking lots is assessed via a set of quality metrics that measure user satisfaction and impact on the local grid. Offline charging strategies under various degrees of available information are validated by comparing their performance with the real-time operation of the parking lot. Results show a power peak reduction of more than 50% using historical data and simple estimations of arrival times, dwell times, and energy requirement. A trade-off between power peaks and service quality (on average 4.4 kWh energy not served) is observed. It was found that knowledge of individual average energy provides higher added value compared to knowing individual average dwell time in both offline planning and real-time operation of the parking lot. • Statistical insights into real-world EV data collected at an office building parking lot. • Quality metrics from user perspective and grid perspective. • Validation of EV charging strategies under different degrees of available information. • Offline planning based on historical information reduces power peak by 51.4%. • Offline planning shows trade-offs with energy not served metrics. [ABSTRACT FROM AUTHOR]

Solar energy is considered the most promising form of renewable energy due to its abundant reserves, widespread availability, and minimal environmental impact. However, the traditional PV (Photovoltaic) systems cannot achieve high electrical efficiency because of the technical restrictions of solar cells and high maintenance costs also hinder the large-scale popularization of PV system. The appearance of CPV (Concentrated Photovoltaic) systems solve the above problems, increasing the electrical efficiency to a great extent, but appropriate cooling technologies are of great need to decrease the cell surface temperature under high heat flux density caused by concentrators. This paper provides a comprehensive review of the different photovoltaic systems and corresponding cooling technologies, detailed investigating the distinctions, applicability, development trend and future technologies of both passive and active cooling methods. The analysis will shed light on the advancements made in increasing efficiency of crucial solar systems, as well as the importance of effective cooling techniques to maintain optimal performance in crucial solar systems. • The development of crucial solar systems and the corresponding cooling technologies are reviewed and discussed. • The focus is on the comparison and analysis of cooling technologies for CPV/T systems. • Spray cooling is one of the optimal cooling techniques for HPCV/T systems. • The application of nanotechnology improves the uniformity of temperature field of solar cells and heat transfer performance. • The challenges and opportunities associated with CPV system cooling technology are considered. [ABSTRACT FROM AUTHOR]

The optimal design of the flow field is of great significance for the performance enhancement and commercial application of proton exchange membrane fuel cells (PEMFCs). The optimization of water-gas transport characteristics in the flow field is the key research content and the key to enhancing the performance and durability of PEMFC. Flow field design evaluation criteria are the mainstream methods for judging the water-gas transport characteristics of flow fields. This paper reviews the current status of PEMFC flow field optimization design research, emphasizes multiple flow field design evaluation criteria, and is dedicated to achieving a standardized, integrated and commercialized design of commercial flow field plates (FFP). Further, a flow field design criterion with a cost-effectiveness index as an important criterion is proposed to optimize the high cost of commercial FFP and poor water-gas transport performance at high current densities. In order to obtain a commercial FFP with better comprehensive performance and better cost-effectiveness, and ultimately promote the commercialization of PEMFC. • An overview of PEMFC flow field optimization research is presented. • Multiple flow field design evaluation criteria are introduced and analyzed. • The concept of optimized design of commercial FFP for SIC is proposed. • CEI is used as an important design criterion for commercial FFP. • Achieving the goal of commercial FFP design with high performance and low cost. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of active fault-tolerant coordination control (AFTCC) for proton exchange membrane fuel cells (PEMFCs), which are complex nonlinear systems with multiple inputs and outputs. Conventional fault-tolerant control methods cannot properly coordinate multiple operating variables and prevent constraint violations in PEMFCs. Our proposed AFTCC method seeks to stabilize the output performance of four operating variables and avoid PEMFC operating constraint violations during failure scenarios. Our method is supported by a curriculum-based multiagent deep meta-deterministic policy gradient (CMA-DMDPG) algorithm, which integrates meta-reinforcement learning, multiagent reinforcement learning and curriculum learning to achieve multitask collaboration of multiple agents, thereby enhancing PEMFC robustness. The algorithm consists of a meta-learner and a base learner. The base learner regards the hydrogen controller, oxygen controller, pump controller and radiator controller as four independent agents and thus achieves a cooperative control policy. The meta-learner detects PEMFC faults and selects an appropriate cooperative control policy. The performance of AFTCC under various stochastic and fault conditions is evaluated using a 75 kW PEMFC model. The results showed that the performance of AFTCC surpassed 11 other fault-tolerant control methods in terms of output voltage, oxygen excess ratio, and stack temperature, and avoided constraint violations. • An AFTCC method is proposed to realize active fault-tolerant control of the PEMFC. • A CMA-DMDPG algorithm is proposed to realize multi-task collaboration of controllers. • The AFTCC improved PEMFC control performance and prevent constraint violation. [ABSTRACT FROM AUTHOR]

A comprehensive review of flapping foils for Wave Devouring Propulsion (WDP) is presented. The flapping foil can effectively utilize wave energy and generate thrust. The development of WDP is discussed, followed by an introduction to the geometry, modes of motion, and operating principles. These research studies are classified as theoretical, experimental, and numerical and are provided in detail. They demonstrate that marine equipment with a flapping foil system can achieve high energy conversion efficiency and low resistance. Several prototypes of the combination of WDP with human-crewed and uncrewed vessels have been shown, including the latest initial concept models and company products. There is a huge prospect for self-driven, pollution-free propulsion of marine devices, and this paper suggests several future studies. • A comprehensive overview of research on wave-induced flapping foils was provided. • Detailed descriptions of the foil geometry and associated parameters was summarized. • A comprehensive summary is presented, from theoretical, experimental, and numerical perspectives. • Potential applications of WDP and future research were suggested. [ABSTRACT FROM AUTHOR]

Freshwater scarcity is a problem that is becoming more and more of a concern over the world, and as a result, the search for solutions has become a race against time. One of the most crucial solutions for this issue is seawater desalination. The simplest and easiest type of desalination technology is seawater desalination using a solar still system. This present study reviews the past/current status of vacuum solar still systems to pave the way for researchers to improve this technology. This paper aims to describe the design specifications and highlight the merits and demerits of various vacuum techniques used in solar stills systems upon which research has been done in the recent past. Also, a discussion on future ideas is given with some recommendations in the field of vacuum solar stills improvement to economically produce sustainable potable water. The current study concludes that lowering the operating pressure of solar still systems improves system productivity and efficiency by roughly 100% and 70%, respectively. According to the research, forced vacuums account for 52% of all vacuums, while natural vacuums account for 48%. Forced vacuum is an ideal method since it combines creating vacuum conditions and evacuating the non-condensable gases, which is not possible in a natural vacuum. The system productivity and efficiency of the forced vacuum conditions are higher by 80% and 25% than that of the natural vacuum conditions. The cost of freshwater produced per liter in natural vacuum conditions is less than that of forced vacuum conditions. • Solar still systems are reviewed with an emphasis on vacuum circumstances. • Two methods for applying vacuum conditions; natural and forced vacuum. • Forced vacuums account for 52% of all vacuums, while natural vacuums account for 48%. • Natural vacuum accompanies problems related to maintenance and space requirements. • Forced vacuum is the best technique as it achieves vacuum conditions and expells the NCG. [ABSTRACT FROM AUTHOR]

In the context of carbon neutrality, renewable energy, especially wind power, solar PV and hydropower, will become the most important power sources in the future low-carbon power system. Since wind power and solar PV are specifically intermittent and space-heterogeneity, an assessment of renewable energy potential considering the variability of wind power and solar PV with high temporal resolution in different regions will facilitate more accurate identification of the decarbonization pathway of power system. In this paper, the complementary output potential of wind-solar-hydro power every 15 min in 31 Chinese provinces is evaluated by developing a multi-objective optimization model based on Nondominated Sorting Genetic Algorithm II. The results show that the total annual complementary power generation potential in China is 17.57 PWh, of which the three components account for 47.8%, 25.3% and 26.9%, respectively. Inner Mongolia and Tibet are the major renewable energy source provinces with annual complementary power generation potential of 5330 TWh and 3907 TWh, accounting for 30.3% and 13.7% of the total power generation potential, respectively. The temporal potential of wind-solar-hydro power varies greatly, with daily potential is more volatile than monthly. Seasonal and spatial heterogeneity of the complemental renewable potential makes some provinces suffer power shortage during long-hours period especially in winter. Our findings will encourage a higher penetration of renewable energy, the promotion of multi-energy complementarity, and the development of inter-provincial power transmission and energy storage infrastructure in China's future power sector. • A multi-objective wind-solar-hydro complementary optimization model is developed. • Electricity supply and demand have gaps at different temporal and spatial scales. • Wind-solar-hydro complementary potential shows great temporal and spatial variation. • Renewable complementarity can improve China's future power system stability. [ABSTRACT FROM AUTHOR]

This paper models two strategic decisions made by industrial entities: the intention to adopt a renewable energy system (RES) and the timeframe for this adoption. The methodology presented considers multiple layers of "unobserved heterogeneity." The results of random parameters imply that the parameters exhibit unobserved heterogeneity across industrial entities. For example, high non-electric energy costs increase the probability of selecting a shorter timeframe in 81.8% of entities and reduce that probability in 18.2% of entities. The results of this study also show that the majority (60%) of responding entities intend to adopt an RES within a short timeframe, generally one to two years, while 40% intend to adopt an RES three or more years after 2022. According to our findings, green bank loans, electricity tariffs, the type of industry, government bureaucracy, and entities' export capabilities predominantly influence their intention to adopt an RES. The results also show that energy-intensiveness (e.g., industrial entities in the plastic and rubber, food and drinks, and chemicals and paints sectors), high electricity tariffs, and elevated non-electric energy costs often expedite the adoption process (resulting in shorter adoption timeframes). Government impediments tend to cause entities to delay their adoption decisions. Capital costs are by far the largest impediment to adoption, as indicated by 29.3% of the surveyed entities, followed by government legislation at 18.6%. The findings presented offer crucial knowledge for creating opportunities to implement new policies and produce an environment in which industries can expedite their transitions to renewable energy. • Solar PV demand by the industrial sector is addressed through heterogeneity models. • Two key decisions are addressed: the intention to adopt and the adoption timeframe. • Heterogeneity in means and variances of the random parameters are accounted for. • Several explanatory variables turned out to influence the two demand decisions. • Heterogeneity models are statistically superior to fixed parameters models. [ABSTRACT FROM AUTHOR]

Although there is large consensus regarding the significance of flexibility in power systems, there exists significant disparity in the definitions and models employed to describe flexibility. To structure existing flexibility descriptions, this work classifies the mathematical principles underlying the flexibility models and finds quality metrics, machine learning models, and flexibility envelopes to be the main higher-order classes, with envelopes being the most popular one. It finds that there is a significant degree of mathematical incompatibility among different flexibility models, even within the same class. This is primarily due to the utilization of distinct flexibility metrics. To address the ambiguities in flexibility definitions and terminology, this paper introduces FLEXBLOX, a formal flexibility taxonomy. FLEXBLOX encompasses three core building blocks: a power system's flexibility requirements, the flexibility potentials provided by flexibility resources, and flexibility mediators that facilitate between the requirements and the potentials. An analysis of 49 flexibility models shows that three of them cover both flexibility requirements and potentials. However, only one of the three approaches also considers a flexibility mediator between them. Two models are generic enough to describe the flexibility potential of diverse flexibility resources, but certain resource characteristics are often excluded. To date, there is no flexibility model that addresses all three flexibility building blocks of the FLEXBLOX taxonomy coherently. This leaves room for future research directions that are suggested in this work. • Flexibility taxonomy based on the concepts of flexibility requirements and potentials. • Categorization of existing flexibility concepts to structure the research area. • Classification scheme for flexibility models based on mathematical principles. • Analysis of 49 flexibility models with regard to the flexibility taxonomy. • Discussion of future research directions in formal flexibility modeling. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) promises to be an alternative solution for secure and versatile charging of electric vehicles. However, some challenges still exist in this contactless technology, such as electromagnetic safety, low transmission efficiency and power capacity. A vast research literature focuses on improving the design and optimization of WPT systems. This paper provides an in-depth literature review on the current status and potential trends of wireless charging for electric vehicles and brushless excitation technology for drive motors, including the power electronic structure, coupling mechanism, and compensation topology of WPT systems. In addition, several emerging research topics are proposed and highlighted. • Fundamental theory, types, and performance of wireless power transmission is reviewed. • The application of WPT systems in electric vehicle charging and non-contact excitation is summarized. • The performance of inductive and capacitive power transfer is compared. • Challenges on coupling mechanism, electromagnetic compatibility, and optimization persist. [ABSTRACT FROM AUTHOR]

This paper is concerned with the fixed-time fractional-order sliding mode control (FTFOSMC) approach using fixed-time disturbance observer (FTDO) for the load following problem of a pressurized water reactor (PWR), in the presence of load-dependent parameters and perturbations. First, by integrating the merits of the fixed-time stability theory and the disturbance observer technique, an FTDO which can ensure fixed-time convergence is constructed to estimate perturbations induced by model uncertainties, external disturbances, and unmeasured states. Then, an FTFOSMC strategy with the help of the disturbance observer is proposed to achieve strong robustness against perturbations and high-precision load following performance. The fixed-time stability of the closed-loop system is theoretically demonstrated by Lyapunov's theorem. Finally, comparative simulation results are presented to illustrate the superiority of the overall proposed control strategy. • A more accurate PWR model with load-dependent parameters and perturbations is built. • A nonlinear FTDO is developed to estimate perturbations. • A FTFOSMC scheme coupled with FTDO is proposed. • Fixed-time stability of closed-loop system is theoretically demonstrated. • Simulation and comparison results reveal superiority of proposed scheme. [ABSTRACT FROM AUTHOR]

Net-zero emission and self-sustaining carbon-neutral have been widely encouraged and intensively explored in wastewater treatment, as the wastewater industry accounts for approximately 1.6% of global greenhouse gas (GHG) emissions. However, how to achieve net-zero GHG emission in wastewater treatment from a biological standpoint is still lacking. In this paper, the status of GHG (i.e. nitrous oxide (N 2 O), methane (CH 4) and carbon dioxide (CO 2)) production and emission in wastewater treatment was comprehensively reviewed. Generally, N 2 O emission contributes the majority of the total GHG emissions from wastewater treatment, and the dissolved N 2 O and CH 4 in the effluent should be paid more attention for the further GHG mitigation. Based on the newly identified microbial communities capable of nitrogen removal with less GHG emissions, several alternative integration systems for GHG mitigation were discussed. Coupling denitrifying anaerobic methane oxidation with anammox process shows high nitrogen removal performance and low GHG emissions, which is regarded as a more promising integration system for GHG mitigation. Moreover, the novel strategies to manage N 2 O and CH 4 as energy sources were also demonstrated, aiming to offset certain carbon footprint in wastewater treatment and thus attain net-zero GHG emission. In addition, future challenges and perspectives of above integration systems and strategies were discussed to facilitate the development of environmentally sustainable wastewater treatment. Finally, a prospective hybrid system integrating emission reduction and energy recovery was proposed as an example for achieving net-zero GHG emission from wastewater treatment. [Display omitted] • Status on GHG production and emission in each treatment unit is quantified. • Autotrophic microorganisms play important roles in mitigating GHG emission. • CH 4 is more feasible than N 2 O for energy recovery from mainstream wastewater. • Net-zero GHG emission integrates both emission reduction and energy recovery. [ABSTRACT FROM AUTHOR]

The determination of maintenance strategies is subject to complexity and uncertainty arising from variable offshore wind farm states and inaccuracies in model parameters. The most common method in the existing studies is to adopt an open-loop approach to optimize a maintenance strategy. However, this approach lacks the ability to capture periodic operational state of the wind farm and the awareness of eliminating uncertainty. Consequently, the determined strategy is inadequate to instruct maintenance activities, inducing excessive revenue losses. In this paper, a closed-loop maintenance strategy optimization method is proposed for decision-makers to identify a more profitable manner of wind farm maintenance management. The life-cycle maintenance optimization problem is decomposed into a sequence of sub-optimization problems covering multiple time periods by using a rolling-horizon approach. Each sub-optimization problem is intentionally designed based on the monitored state of the wind farm and the available reliability, availability, and maintainability (RAM) database. Meanwhile, the decision maker consciously mitigates the parameter uncertainty in the maintenance model gradually by updating the current database. Compared to conventional strategies covering the entire lifetime of wind farms, the proposed maintenance strategy is periodically adjusted to provide a series of sub-strategies. The proposed approach was applied in a simulation experiment, a generic small-scale offshore wind farm, to assess its performance. Computational results show that adapting maintenance strategies based on the current state of the wind farm can reduce revenue losses in comparison to conventional open-loop strategies. In addition, the benefits of updating the RAM database in decreasing revenue losses is revealed. • Proposing a maintenance strategy with a closed-loop decision-making process. • Dividing the entire maintenance optimization problem into sub-problems covering multiple time periods. • Gradually mitigating model parameter uncertainty over time with new operational data. • Adjusting the entire maintenance strategy into a series of sub-strategies based on wind farm states and updated parameters. [ABSTRACT FROM AUTHOR]

With the intensification of global climate problems, the worldwide call for reducing CO 2 emissions is getting louder and louder. Low-carbon development has become the consensus of all countries. The electric heating film systems (EHFS) have recently attracted much attention as a clean and low-carbon building heating way due to the global target of carbon neutrality. This paper aims to provide a comprehensive review of the materials, performances and applications of the electric heating film (EHF). The conductive materials for the EHF mainly include graphene and carbon nanotubes (CNTs). Moreover, the main preparation methods are redox method, chemical vapor deposition (CVD), vacuum filtration method and screen printing. It was found that the EHF doped with the graphene or the carbon nanotubes (CNTs) has better performance on flexibility and thermal stability. The EHF prepared by chemical vapor deposition (CVD) has the best performance on uniformity and structure. However, this method is costly and difficult to implement for large-scale industrial production. Therefore, the screen printing technology remains the most widely used method. The composite EHF with two or more conductive materials (graphene and multi-walled carbon nanotubes (MWCNT)) has excellent mechanical properties, superb damage resistance and flexibility. In addition, the numerical simulation based on computational fluid dynamics (CFD) will be an important research method to investigate the indoor thermal environment of building heating by EHFS, which needs to be conducted in the future. The high performance EHF will be widely used in international applications such as artificial intelligence, wearable devices, aerospace, solar energy and medical protection. • The influence factors of electric heating film (EHF) conductive materials and composites are reviewed. • The methods of EHF and conductive materials are studied and synthesized. • The performance of the EHF is analyzed by means of experimental and numerical simulation. • The application of EHF is reviewed and prospected. [ABSTRACT FROM AUTHOR]

Due to increasing amounts of energy being supplied by intermittent renewable energy sources, future energy systems need to be able to react flexibly to sudden changes. To address this challenge, a large body of research is devoted to improving the utilization of energy flexibility of various types of energy resources on the supply and demand side. This is commonly done by applying mathematical models. The objective of this paper is to review such models and identify common modeling approaches used to quantify and optimize the use of flexible energy resources. The literature review is conducted systematically, encompassing 215 publications that feature 694 models of different energy resources. The main distinction of this work, in comparison to other reviews on the topic of energy flexibility lies in its focus on the mathematical formulation of models of energy resources and the quantification of the models' level of detail. The aim is to identify common modeling approaches and the corresponding research problems they address. The review shows that the majority of research efforts are directed towards the management and optimization of distributed energy resources. The most commonly employed modeling approach involves abstract black-box models with limited levels of detail. Linear programming and meta-heuristics are frequently used to optimize energy flexibility. A critical reflection of the current common practice is conducted and recommendations for future research are formulated. [Display omitted] • Literature review of 215 reports presenting model approaches for energy flexibility. • Categories of research problems identified and deduction of two main research focuses. • Presenting models of common energy resources classified into different model types. • Mostly low level of detail seen in modeling energy flexibility. • Optimization models are used to represent and quantify flexibility. [ABSTRACT FROM AUTHOR]

The gamut of geothermal energy research encompasses the studies aimed at harnessing the abundant and inexhaustible thermal energy within the Earth, and it ranges from heat transfer to the activity of thermophilic microorganisms, 3D printing, and additive manufacturing and impacts the NET ZERO endeavour of humanity. In this paper, computational social network analysis has been employed to discover the subfield clusters of geothermal energy research and further trace the key evolutionary routes from the research corpus. The development, limitations, and opportunities of each cluster are examined, and it becomes evident that the focus of research ranges from geothermal evaluation, long-term effects of borehole heat exchangers, shallow systems that employ urbanisation's ground heating, enhanced geothermal systems (EGS) for district heating, combined and hybridised geothermal power generating models, including multi-generation and poly-generation, geothermal fluids, reinjection and their dual nature, environmental effects in geothermal water and mineral scaling, enhanced geothermal systems aiming to increase permeability without causing seismicity, and finally to social acceptability. We address significant questions, such as whether the waste heat is compatible with the idea of green geothermal heat and the elimination of pollutants and find that further R&D and technological advancements are required for this ubiquitous clean energy to get wider acceptance and employment. The future of this energy depends on the rational and scientifically sound exploration and use of the resources, just as in the case of fossil fuels, and thus precludes geothermal energy as a win-all solution to the energy needs of the whole world. • Computational analysis of geothermal energy research themes and linkages. • Algorithmic theme identification rather than expert-based analysis. • Tracing the key-routes of domain evolution. • Subdomain-specific status, limits, emerging fronts and future research agenda. • Impact analysis of contemporary technologies such as AI and 3D printing. [ABSTRACT FROM AUTHOR]

Occupant behavior in buildings might result into gap between predicted and actual energy use and cause indoor thermal comfort fluctuations, due to its uncertainty and unpredictability. Previous studies mainly focus on the investigations of occupant behavior impact and modeling methods, whereas few concludes strategic solutions. It is hard to narrow the negative impact of occupant behavior without a clear Impact-Modeling-Solution clue. Thus, the major objective of this research is to review and analyze the impact of occupant behavior and then to summarize modeling methods and strategic solutions by connecting specific techniques and approaches. This paper first investigates the characteristics of occupant behavior and then discusses the impact. It indicates that thermal comfort (environmental condition) triggers occupant actions with corresponding building systems, resulting in energy load changes. The occupant behavior in turn causes thermal comfort fluctuations. The strategic approaches of traditional methods such as surveys, experiments/tests and simulations, and artificial intelligence (AI)-based techniques are analyzed respectively. It is found that the intelligent approach shows high robustness in addressing the uncertain and unpredictable characteristics of occupant behavior in buildings, compared with traditional methods. The AI-based methods and data-driven approaches can enhance the prediction of building energy consumption and the recognition of occupant's thermal comfort. Typical modeling methods and flowchart for occupant behavior are presented with comparisons. The novel physics-based and data-driven model which performs strong adaptability, high decision-making efficiency and fast response of the controller is especially introduced. The corresponding improvements and future directions are also proposed to reach optimal effects. • The research clue of Impact-Modeling-Solution for occupant behavior in buildings is proposed. • Traditional methods and AI-based techniques and data-driven approach are compared. • Typical modeling methods for occupant behavior are presented with comparisons. • Typical strategic solutions are presented upon connections with modeling scopes and methods. • AI-based approaches to address building energy prediction and thermal comfort are summarized. [ABSTRACT FROM AUTHOR]

The Sun is the star in our solar system that beams solar energy towards the Earth, shining it during the day. The researcher discovered different ways to enhance the use of solar radiation to meet daily need because they are aware of how abundant it is. The thermal performance of double pass solar collector (DPSC) is higher compared to flat plate solar collector (FPSC) when comparing their thermal efficiencies. There have been several studies done on the experimental and theoretical analysis of DPSC, where different kind of tests have been carried out on different aspects. This paper aims to reviews recent development (5 years) on double pass solar collector (DPSC) where it highlights the improvement methods, functioning parameters, materials used, and design configurations. By reviewing experimental and theoretical analysis on the double-pass collector with various thermal transfer enhancement, it can help the researchers to keep updated on new development of the double-pass collector. Several methods to improve the convective heat transfer for the system were adding fins, phase change material (PCM), improved absorbers and porous media to the DPSC. Other important things that require improvement are increasing the outlet temperature, efficiency enhancement for DPSC and pressure drop reduction. The effect of using various mass flow rates, solar radiation, temperatures and working fluid on DPSC are also discussed. We wrap this review by identifying numerous applications that are possible for the solar air heating such as space heating and conditioning, water desalination process and drying agricultural food product. • Adding phase change material (PCM), can enhance thermal efficiency for double pass solar collector. • Fins can increase convective heat transfer. • Porous media can accelerate the performance of double pass solar collector. • Adding tubular on absorber can helps to increase the heat efficiency. • New novelty double pass solar collector has been found for the last 5 years. [ABSTRACT FROM AUTHOR]

Over the past few years, numerous countries have rapidly expanded the number and size of their high-tech clean fabrications, to keep pace with electronic devices and Internet needs. Moreover, extremely strict dry-bulb temperature, relative humidity, and particle concentration requirements cause high-tech cleanrooms to consume enormous energy, which is nearly three times the average energy consumed by data centers. Reducing energy use while ensuring the required built environment for normal production has become key challenges in high-tech clean manufacturing, and gradually attracted public and academic attention. However, different from extensive research and review studies conducted on data centers, no study has systematically reviewed state-of-the-art research on the energy aspects of high-tech cleanrooms. Therefore, this paper comprehensively reviews the research work on energy performance and energy conservation methods for high-tech cleanrooms. The main features and energy use status of high-tech cleanrooms are presented and analyzed. The energy models and evaluation metrics of high-tech cleanrooms, as well as the performance assessments and analysis of their environmental control systems (i.e., air-conditioning systems) are summarized and elaborated. Efforts on the performance improvement and energy conservation of high-tech cleanrooms, particularly air-conditioning systems, are also reviewed from multiple aspects, i.e., cold-heat offset reduction, air exchange rate, and airflow resistance optimization, and cooling plant efficiency improvement. A future framework for establishing smart, sustainable, and efficient high-tech cleanrooms is also proposed and discussed. [Display omitted] • A comprehensive review on energy research of high-tech cleanrooms is presented. • Main features and energy use of high-tech cleanrooms are categorized and analyzed. • Energy performance & its assessment methods for high-tech cleanrooms are summarized. • Exiting energy conservation methods and latest technology development are reviewed. • Future perspectives for smart and sustainable high-tech cleanrooms are elaborated. [ABSTRACT FROM AUTHOR]

Interspecies electron transfer (IET) between fatty acid-oxidizing bacteria and hydrogenotrophic methanogens is key to stable and efficient methanogenesis in the anaerobic digestion (AD) process. Recently discovered direct IET (DIET) enables energetically and kinetically advantageous methanogenesis and facilitating cell-to-cell electrical connections using conductive additives (mostly metal- or carbon-based) has been recognized a promising approach to enhancing methanogenesis. Over the last decade, extensive efforts have been made to understand the mechanism and role of DIET in AD and to use it to improve AD performance and stability. However, challenges and limitations remain and must be addressed for the practical application of DIET-AD technology, for example, (i) how to prevent the washout loss of particulate conductive materials in continuous operation, (ii) how to further promote DIET so as to achieve better and more stable methanogenic performance, and (iii) how to evaluate the effects of DIET promotion separately from enhanced biomass retention by adding conductive materials with high specific surface areas. This paper discusses these challenges in both research and practical application of engineering DIET in AD using conductive additives, as well as the efforts to address them. Reviewing current technologies and recent advances to tackle the challenges and improve the practicability of the DIET-AD process, it has been suggested that significant further research is needed, especially on the retention of conductive additives and their biocompatibility and interactions with microorganisms. DIET-AD technology is still in its early stages, and ongoing efforts are required to improve its scalability and economic feasibility at the industrial scale. [Display omitted] • Challenges in engineering DIET with conductive additives are critically reviewed. • Strategies to prevent washout of particulate conductive DIET promoters are needed. • External voltage application with conductive additives can further promote DIET. • Tools to separate the effects of DIET promotion and biomass retention are needed. • More studies are needed to evaluate and improve the scalability of DIET-AD systems. [ABSTRACT FROM AUTHOR]

Increased renewable electricity reduced electricity prices but the costs of consumer-funded support schemes were added to utility bills. Previous studies compared these two components to understand the impacts on consumers. This paper constructs a framework for the electricity sector and provides a new angle to examine the impacts of renewable support schemes on consumers and the sector, respectively. Any negative gain to consumers was offset by the positive gain received by renewable generators (and suppliers), leaving the sector unaffected. In contrast, the increase in renewable electricity brought positive gain to the sector as a whole through reduced fossil fuels imports and greenhouse gas (GHG) emissions. We examine the structural change in the generation mix from 2006 to 2020 in the UK and suggest that wind generation replaced coal-fired generation rather than gas-fired generation on the longer horizon. Therefore, using coal-related coefficients and a contribution share of 38.6% for renewable subsidies, we suggest that wind generation supported by the RO scheme brought positive net gain to the sector, exceeding £800 million per annum in 2018–19 and 2019–20. Therefore, the discrepancy in payoffs from the perspective of consumers and the sector imposed a difficult challenge for policymakers, as criticism would be raised if the analysis was done on consumers only. • Renewable support schemes brought net gain to the electricity sector. • The first type of net gain was avoided costs from fewer imports of fossil fuels. • The second type of net gain was avoided costs from reduced GHG emissions. • Wind replaced coal rather than gas in the generation mix in the long term. • The net gain to the electricity sector exceeded £800 million per annum between 2018 and 2020. [ABSTRACT FROM AUTHOR]

The market of batteries for electric mobility is expected to greatly expand in Europe during the next decades. The most sustainable batteries to be produced in the future depend on the primary and secondary resources available and on the capacity to produce and recycle battery cells. This paper proposes an optimization model based on Material Flow Analysis and prospective Life Cycle Assessment which allows us to suggest the types of batteries which should be produced and recycled, the primary and secondary resources to be used, and in which quantities. Several scenarios are proposed to address the uncertainty of the future batteries market. In the Reference Scenario, designed to reflect the European policies, the results show that Europe would achieve high self-sufficiency from external producers (72%), but this percentage could decrease drastically in the case of alternative scenarios (up to 35%). Furthermore, in the Reference Scenario, lithium-iron-phosphates (40%) and lithium-air (23%) batteries result to be the best options. To cut the consumption of lithium and cobalt, sodium-ion cells (3%) could also be considered for manufacturing or even nickel-cobalt-manganese (6%) type to exploit secondary cobalt. In alternative scenarios instead, the proposed algorithm would suggest different choices as a function of the boundary conditions. For instance, in case the demand and the re-use rate of the cells are higher than in the Reference Scenario, the environmental impact of batteries for mobility turns out to increase because of the lower self-sufficiency of the European industry. • Material flow analysis and prospective LCA are integrated into an optimization model. • Several scenarios are set to address the uncertainty of the future batteries industry. • The European batteries' production and recycling to cut GHG emissions are assessed. • The optimal management of primary and secondary resources is evaluated in time. • The model evaluates the batteries industry's relevant GHG mitigation (up to −45%). [ABSTRACT FROM AUTHOR]

The development of off-grid hybrid renewable energy systems (HRESs) is essential to rural electrification and global decarbonization. Based on 299 journal papers in the recent five years, this work conducts a state-of-the-art qualitative review and quantitative bibliometric analysis on the sizing optimization of off-grid HRESs. An overview of system configurations, energy management strategies, performance evaluation indicators, and sizing methodologies are presented, and bibliometric analysis is conducted to reveal the overall scope and mainstream of this research field. Finally, promising future works are summarized on the basis of current research gaps. The results of bibliometric analysis indicate that: (1) solar photovoltaic and batteries are the most common energy source and energy storage respectively, and wind-photovoltaic-battery-diesel is the most popular system configuration; (2) most researchers apply rule-based energy management strategies rather than optimized strategies, owing to their advantages of simple implementation and fast computation; (3) 97.99% of articles considers economic indicators in the sizing optimization model, and techno-economic feasibility is the essential research foundation at the planning stage; (4) meta-heuristic algorithms and the HOMER software tool are the two most popular sizing methodologies for off-grid HRESs. In future works, hybrid energy storage systems, deep reinforcement learning-based energy management strategy, sustainability and resilience indicators, as well as distributionally robust optimization-based sizing methodologies are promising research directions. Overall, the presented overviews and outlooks can provide holistic theoretical knowledge about sizing optimization research for practitioners, thus promoting the academic progress and practical implementation of off-grid HRESs. • Qualitative review and quantitative bibliometric analysis on energy system planning. • Overview of conventional and emerging renewable energy and storage technologies. • Classification of energy management strategies integrated with sizing optimization. • Multi-perspective projection of future works based on current knowledge gaps. [ABSTRACT FROM AUTHOR]

Dust accumulation on the surface of solar harvesting devices can significantly reduce energy yield. Electrodynamic Shield (EDS) technology can remove dust via an electric field generated on the top layer of the solar harvesting devices. This technology does not require the use of water and can operate with a fraction of the power generated by the solar harvesting devices. The electric field is generated by applying a voltage across electrodes deposited on the surface of the solar harvesting devices. Extensive research is being carried out to: (1) Identify and characterize important parameters and their effect on the cleaning efficiency of the EDS, (2) improve the optical transmission and conductive properties of the electrodes, and (3) develop scalable electrode coatings. This review paper discusses the current state of research on EDS technology, mechanisms of dust removal, parameters that determine cleaning efficiency, and recent advances in the application of EDS for both space and terrestrial applications. The literature on the impact of electrode geometry is less than adequately needed to understand its effects on cleaning efficiency. The independent role of frequency and waveshape applied to an EDS remains an open research question. The main challenges that need to be addressed before this technology can be successfully implemented on a large scale include: (1) increasing the efficiency of fine dust particle removal while optimizing for power consumption, (2) further experimental validation of theoretical models built to calculate cleaning efficiency for simulated EDS, and (3) exploring new materials to manufacture electrodes at scale. • Comprehensive review of Electrodynamic Shield (EDS) for terrestrial applications. • Extremely promising technology to address solar panel soiling issues. • The fundamentals of operations and dust removal mechanisms are discussed in detail. • The most important parameters affecting cleaning efficiency are identified. • Scaling up and field testing remain important open issues. [ABSTRACT FROM AUTHOR]

The growing need to alleviate the environmental impact of fossil fuels demands further technical growth in fuel cell hybrid electric vehicles (FCHEVs). Due to the dynamic nature of electrochemical power resources such as fuel cells (FCs) with auxiliary energy storage systems (ESSs), a variety of power management strategies (PMSs) have been widely developed and analysed for optimal power allocation. In this paper, a comprehensive review of various PMSs is systematically investigated for data acquisition and management regarding the search strategy. Within the data collected, the classification and the performance of PMSs are analysed to determine their characteristics and objectives for optimisation process. Additionally, a thorough examination of various PMSs employed in marine industry provides insights into the research trends and challenges associated with FC and battery hybrid systems and particularly ship propulsion systems. Furthermore, a system-level approach to PMS is explored, highlighting the importance of considering the correlation between component sizing and control as well as a health-conscious management that can enhance cost-effectiveness and life cycle of a FC and battery electric ferry applications. • A comprehensive review of power management system (PMS) in fuel cell electric vehicles. • Detailed analysis of PMS classifications and features. • A review and analysis of PMS in fuel cell ferry. • Discussion of current issues and potential research of PMS in ship propulsion system. [ABSTRACT FROM AUTHOR]

Errors in forecasting load and renewable-based generation in restructured power systems mean that independent system operators (ISOs) must procure sufficient operating reserves to keep the real-time operation of the system reliable and secure. But when procured reserves turn out to be insufficient in real-time due to the lack of resource capacity or ramp capability, operators often set higher prices for reserves and energy to encourage more supply, and to motivate consumers to decrease usage or shift it to other times. This procedure, which is called scarcity or shortage pricing, is a core feature of U.S. electricity markets. It is receiving increased attention from market designers and stakeholders because scarcity will become more important for spot price formation in the future with the increased penetration of zero-marginal cost renewables, and the shrinking role of fuel costs in setting prices. Scarcity pricing is implemented in various ways by different ISOs. These differences have practical implications for the level of prices and incentives for investment, operations, and demand modification. In this paper, general approaches and specific calculation procedures for reserve and energy scarcity pricing practices and calculations across the seven ISO-based U.S. power markets are reviewed and compared. A consistent terminology is used to facilitate the comparison. Current scarcity pricing practices are grouped into three approaches: (1) imposing an adder after the spot market is run; (2) including stepwise demand curves within market clearing procedures for non-contingency reserve products (e.g., the novel flexiramp product), which tends to yield longer right tails for energy scarcity premium curves; and (3) having stepwise demand curves for traditional contingency reserve products only, which results in shorter right tails in energy scarcity curves. A generic numerical example is presented to highlight the large practical differences among the reserve scarcity pricing approaches and specific implementations. To further investigate factors that contribute the most to demand curves differences among ISOs, a sensitivity analysis is performed. This analysis shows that the largest source of differences among the curves is the scarcity prices assumed in the case of severe scarcity, while the number of steps used and whether flexiramp is considered also yields important differences in scarcity prices. As renewable penetration increases, it will become increasingly crucial to employ administrative demand curves so that spot prices more effectively motivate supply and demand adjustments exactly when and where they are needed. This study shows that the different assumptions yield very different scarcity premiums for reserves and energy, and are likely to provide divergent incentives for resources to respond to shortages. It is concluded that to promote market efficiency, a reserve shortage demand curve should have at least three features: inclusion of the marginal value of reserve products at each shortage level, consideration of the magnitude and probability of supply contingencies, and avoidance of abrupt price discontinuities that can cause excessively volatile market outcomes. • Explains principles and specific calculation procedures for reserve scarcity pricing practices across U.S. power markets. • Proposes a novel classification of sources of penalty values applied in the markets, highlighting their relative advantages. • Presents a generic numerical example to illustrate practical differences among the reserve scarcity pricing approaches. • Performs a sensitivity analysis to further investigate the most significant factors in differences among ISO demand curves. • Makes recommendations for defining demand curves for reserve scarcity pricing that accurately reflect the value of reserves. [ABSTRACT FROM AUTHOR]

Researchers have begun to realize first-hand that the causes and effects of telework are much more complex than immediately apparent. While reduced commuting to work is widely beneficial (environment, economy, health, etc.), the impacts of telework are widespread (e.g., long-term urban planning considerations, home and office utilization, demand on communication networks, etc.). This paper aims to review and structure a large body of literature and emerging research from COVID-19-induced teleworking to address the complex relationships and energy impacts of telework on the four domains of homes, transportation, offices, and information and communication technologies (ICT). A systematic search was conducted on databases and the results were categorized. At the centre, we identified many relationships between homes and transportation, as teleworking gives teleworkers to have more flexibility in terms of location. Furthermore, the relationships between offices and homes are important since the operating costs of offices are on the teleworkers' side. Accordingly, cause and effect relationships were mapped out between and within domains. The outcome demonstrates that researchers and policymakers need to consider widespread implications of telework. As a result, it is essential to study items in each domain, intrarelationships in each domain, and most importantly the relationships between domains to capture and quantify the impacts of teleworking comprehensively. • Telework primarily impacts energy use in four domains of homes, offices, transportation, and ICT. • Comprehensive studies on telework should study four domains simultaneously. • Interrelationships between domains are important determinants of teleworking impacts. • There is a major literature gap on interrelationships between domains. • Teleworkers' behavior and decisions are a significant source of uncertainty for energy use. [ABSTRACT FROM AUTHOR]

This is the first study utilizing carbon tax revenue to the renewable energy generation with Learning-by-doing (LBD) in the CGE model. This investigation demonstrates how induced technologically change (ITC) in the power sector offsets negative impacts on economic growth caused by the carbon tax in China. Business-as-usual scenario (without carbon tax) shows a significant impact of LBD on GDP growth and CO 2 emission reduction. Under a policy scenario with carbon tax, the results show that the negative impact on economic growth can be alleviated to less than 0.12%. If total carbon tax revenue was used for the subsidy to wind and solar power, even a positive impact on GDP growth will occur in the long-term. Therefore, the results verified and demonstrated the synergic effect of carbon pricing and the LBD process that economic loss caused by carbon tax could be offset by ITC in the renewable energy power sector. GDP decomposition shows that unexpensive electricity affected by ITC is beneficial to drive development of low-carbon energy, which can mitigate shock of carbon tax on heavy dependence on fossil fuel. This paper also provides policy implications that the LBD process will positively play a key role in energy structural shift under climate policy, making a great effort to climate mitigation. [Display omitted] • Combining bottom-up CGE model with top-down module Learning-by-Doing. • Utilizing carbon tax revenue to subsidy to renewable energy generation. • Providing optimistic impacts of carbon tax and subsidy on economic growth and reduction of carbon emission. • Learning-by-doing describes pathway of improved renewable energy. • Giving implication that Learning-by-doing can be boosted by environmental policies. [ABSTRACT FROM AUTHOR]

Recently, with the development of industrial informatization and intellectualization, the development of smart bearings has attracted a lot of significant attention in an attempt to reduce maintenance costs and increase reliability by providing online health condition monitoring. As a result of advances in miniaturization and low power consumption of wireless sensor nodes (WSNs), self-powered technologies have been considered as a promising method to achieve autonomous WSNs in smart bearings. Although the self-powered technology has received considerable achievements, there are less reviews covering the development of self-powered structures towards smart bearing and providing potential guidelines for the future development. To bridge the gap, this paper presents a comprehensive state-of-the-art review and guidelines on self-powered methods to create smart bearings, including outlining the underlying theory, modeling methods, methodologies and technologies. The topology of a self-powered smart bearing is clarified, and the mechanisms and benefits of piezoelectricity, electromagnetism, triboelectricity, thermoelectricity and wireless power transfer for powering WSNs in smart bearing are discussed. To improve the applicability of self-powered smart bearing in a range of working conditions, the design methodologies and technologies of a variety of transducers are reviewed to provide guidelines for performance enhancement. Finally, the future challenges and perspectives are proposed for outlining potential research directions and opportunities in future self-powered smart bearing systems, including the impact on bearing performance, engineering implementation, reliability, power management and storage. • A detailed review of self-powered methods for smart bearing is presented. • Topology and working principle of a self-powered smart bearing are clarified. • Mechanisms, modeling, and methodologies are reviewed for performance enhancement. • Perspectives and challenges of developing self-powered smart bearing are proposed. [ABSTRACT FROM AUTHOR]

In view of the current geopolitical situation, the EU and its Member States are accelerating efforts to reduce their dependency on fossil fuel imports, while simultaneously tackling the climate crisis. With heating in buildings accounting for a large share of the energy consumption in the EU, policies to phase-out fossil fuels for heating and to switch to renewables are key elements. In the context of the proposed actions to phase-out fossil fuels at EU level, this article provides a systematic analysis of current and planned phase-out regulations for fossil fuel boilers in the EU Member States. The paper quantifies the share of energy consumption for heating that is addressed by such regulations and finds that the current regulations only address about 10% of the total fossil energy consumption for heating in the EU. The share increases to almost 30% when considering the planned regulations, reflecting the fact that large energy consumers such as Germany and the Netherlands have announced such regulations. The analysis shows that several Member States with high energy consumption for heating have neither implemented nor announced plans to introduce phase-out regulations for fossil fuel heating. The study concludes that immediate policy action is needed both at EU and at Member State levels. At EU level, the proposed introduction of an end-date for stand-alone fossil fuel boilers needs to be substantiated and implemented into the legislative framework. At the national level, phase-out regulations for fossil fuel boilers need to be expanded both in quantity and scope. [Display omitted] • Systematic analysis of phase-out regulations for fossil fuel boilers in the EU. • Only 10% of the EU fossil energy used for heating is covered by phase-out regulations. • Including planned regulations, the share of heating energy covered by phase-out regulations increases to almost 30%. • Comparison of different approaches for implementing regulations for phasing out fossil fuel boilers. [ABSTRACT FROM AUTHOR]

Renewable energy sources such as wind farms and solar power plants are replacing conventional coal-based synchronous generators (SGs) to achieve net-zero carbon emissions worldwide. SGs play an important role in enhancing system strength in a power system to make it more stable during voltage/frequency disruptions. However, traditional coal-fired SGs are being decommissioned in many parts of the world, owing to stringent environmental regulations and low levelized cost of energy of renewables. Consequently, maintaining system strength in a renewable energy-dominated power system has become a major challenge, and without adequate mitigation techniques, low system strength can potentially cause widespread power outages. This paper provides an overview of system strength and its measurement techniques in a power system with a large number of renewable energy sources (RESs), for example solar and wind farms. The review includes the system strength measurement techniques, mitigation approaches, and future challenges. • A comprehensive review on system strength for Australia. • Integration of power systems with large number of renewable energy sources. • Measurement and mitigation techniques for system strength shortfalls. • Analysis of future challenges and research directions on system strength. [ABSTRACT FROM AUTHOR]