Physics-based electrochemical battery models derived from porous electrode theory are a very powerful tool for understanding lithium-ion batteries, as well as for improving their design and management. Different model fidelity, and thus model complexity, is needed for different applications. For example, in battery design we can afford longer computational times and the use of powerful computers, while for real-time battery control (e.g. in electric vehicles) we need to perform very fast calculations using simple devices. For this reason, simplified models that retain most of the features at a lower computational cost are widely used. Even though in the literature we often find these simplified models posed independently, leading to inconsistencies between models, they can actually be derived from more complicated models using a unified and systematic framework. In this review, we showcase this reductive framework, starting from a high-fidelity microscale model and reducing it all the way down to the single particle model, deriving in the process other common models, such as the Doyle–Fuller–Newman model. We also provide a critical discussion on the advantages and shortcomings of each of the models, which can aid model selection for a particular application. Finally, we provide an overview of possible extensions to the models, with a special focus on thermal models. Any of these extensions could be incorporated into the microscale model and the reductive framework re-applied to lead to a new generation of simplified, multi-physics models.

Direct air capture (DAC) can provide an impactful, engineered approach to combat climate change by removing carbon dioxide (CO₂) from the air. However, to meet climate goals, DAC needs to be scaled at a rapid rate. Current DAC approaches use engineered contactors filled with chemicals to repeatedly capture CO₂ from the air and release high purity CO₂ that can be stored or otherwise used. This review article focuses on two distinctive, commercial DAC processes to bind with CO₂: solid sorbents and liquid solvents. We discuss the properties of solvents and sorbents, including mass transfer, heat transfer and chemical kinetics, as well as how these properties influence the design and cost of the DAC process. Further, we provide a novel overview of the considerations for deploying these DAC technologies, including concepts for learning-by-doing that may drive down costs and material requirements for scaling up DAC technologies.

The need for storage in electricity systems is increasing because large amounts of variable solar and wind generation capacity are being deployed. About two thirds of net global annual power capacity additions are solar and wind. Pumped hydro energy storage (PHES) comprises about 96% of global storage power capacity and 99% of global storage energy volume. Batteries occupy most of the balance of the electricity storage market including utility, home and electric vehicle batteries. Batteries are rapidly falling in price and can compete with pumped hydro for short-term storage (minutes to hours). However, pumped hydro continues to be much cheaper for large-scale energy storage (several hours to weeks). Most existing pumped hydro storage is river-based in conjunction with hydroelectric generation. Water can be pumped from a lower to an upper reservoir during times of low demand and the stored energy can be recovered at a later time. In the future, the vast storage opportunities available in closed loop off-river pumped hydro systems will be utilized. In such systems water is cycled repeatedly between two closely spaced small reservoirs located away from a river. This review covers the technology, cost, environmental impacts and opportunities for PHES. The key motivations for this review are firstly that large amounts of variable wind and solar generators are being deployed; and secondly that there are vast opportunities for low-cost pumped hydro storage that do not require interference with rivers (with the associated environmental cost).

Sodium-ion batteries (SIBs) are one of the most promising alternatives to lithium-ion batteries (LIBs), due to the much more abundant resources of Na compared with Li in the world. Developing SIB technology to satisfy the increased demand for energy storage is therefore a significant task . However, one of the biggest bottlenecks is the design of high-performance and low-cost anode materials, since the graphite anode in commercial LIBs is not suitable for SIBs due to thermal dynamic issues. Hard carbon materials have been regarded as having the greatest potential as anodes in commercial SIBs owing to their excellent cost-effectiveness, but their relatively limited performance compared to the graphite in LIBs as well as the dimness of the sodium storage mechanisms still need further investigation. In this review, we summarize the progress of recent research into hard carbons for SIB applications, including the fundamentals of SIBs, sodium storage mechanisms, structures and the electrochemical performances of different types of hard carbons in SIBs and other types of sodium-based energy storage as well as the main challenges in this field. We aim to provide a general insight into hard carbons and their applications in SIBs, opening up future perspectives and possible research directions.

In an era of U.S. energy abundance, the persistently high energy bills paid by low-income households is troubling. After decades of weatherization and bill-payment programs, low-income households still spend a higher percent of their income on electricity and gas bills than any other income group. Their energy burden is not declining, and it remains persistently high in particular geographies such as the South, rural America, and minority communities. As public agencies and utilities attempt to transition to a sustainable energy future, many of the programs that promote energy efficiency, rooftop solar, electric vehicles, and home batteries are largely inaccessible to low-income households due to affordability barriers. This review describes the ecosystem of stakeholders and programs, and identifies promising opportunities to address low-income energy affordability, such as behavioral economics, data analytics, and leveraging health care benefits. Scalable approaches require linking programs and policies to tackle the complex web of causes and impacts faced by financially constrained households.

The Doyle–Fuller–Newman (DFN) framework is the most popular physics-based continuum-level description of the chemical and dynamical internal processes within operating lithium-ion-battery cells. With sufficient flexibility to model a wide range of battery designs and chemistries, the framework provides an effective balance between detail, needed to capture key microscopic mechanisms, and simplicity, needed to solve the governing equations at a relatively modest computational expense. Nevertheless, implementation requires values of numerous model parameters, whose ranges of applicability, estimation, and validation pose challenges. This article provides a critical review of the methods to measure or infer parameters for use within the isothermal DFN framework, discusses their advantages or disadvantages, and clarifies limitations attached to their practical application. Accompanying this discussion we provide a searchable database, available at www.liiondb.com, which aggregates many parameters and state functions for the standard DFN model that have been reported in the literature.

Electric vehicles (EVs) are experiencing a rise in popularity over the past few years as the technology has matured and costs have declined, and support for clean transportation has promoted awareness, increased charging opportunities, and facilitated EV adoption. Suitably, a vast body of literature has been produced exploring various facets of EVs and their role in transportation and energy systems. This paper provides a timely and comprehensive review of scientific studies looking at various aspects of EVs, including: (a) an overview of the status of the light-duty-EV market and current projections for future adoption; (b) insights on market opportunities beyond light-duty EVs; (c) a review of cost and performance evolution for batteries, power electronics, and electric machines that are key components of EV success; (d) charging-infrastructure status with a focus on modeling and studies that are used to project charging-infrastructure requirements and the economics of public charging; (e) an overview of the impact of EV charging on power systems at multiple scales, ranging from bulk power systems to distribution networks; (f) insights into life-cycle cost and emissions studies focusing on EVs; and (g) future expectations and synergies between EVs and other emerging trends and technologies. The goal of this paper is to provide readers with a snapshot of the current state of the art and help navigate this vast literature by comparing studies critically and comprehensively and synthesizing general insights. This detailed review paints a positive picture for the future of EVs for on-road transportation, and the authors remain hopeful that remaining technology, regulatory, societal, behavioral, and business-model barriers can be addressed over time to support a transition toward cleaner, more efficient, and affordable transportation solutions for all.

The rapidly growing scale of solar photovoltaics and wind energy coupled with electrification of transport, heating and industry offers an affordable pathway for achieving deep decarbonization. Massive integration of variable solar photovoltaics and wind energy requires large-scale adoption of short (seconds-hours) and long (hours-days) duration energy storage. Currently, long-duration pumped hydro energy storage (PHES) accounts for about 95% of global energy storage for the electricity sector. This paper discusses the Global PHES Atlases developed by the Australian National University which identify 0.8 million off-river (closed-loop) PHES sites with a combined 86 million Gigawatt-hours of storage potential, which is about 3 years of current global electricity production. These Atlases show that most global jurisdictions have vast potential for low-cost PHES with small water and land requirements, and that do not require new dams on rivers. The low capital cost of premium PHES systems ($ per kilowatt-hour) is pointed out. Methods for creating shortlists of promising PHES sites from the Atlases for detailed investigation are developed.

Heat pumps play a crucial role in the transition toward sustainable energy. This review draws on an extensive range of resources to analyse advancements in heat pump technologies and their contribution to achieving the European Union’s (EU) goals on clean and secure heating/cooling. First, it provides a comprehensive overview of the status and trajectories of heat pump penetration, recent regulations, market growth projections, and supply chain challenges within the EU. Then, the report highlights state-of-the-art technological advancements and innovation trends in areas such as refrigerant and component development, optimal operation, and smart integration with other technologies, including alternative heating and cooling systems, thermal and electrical storage, and solar energy. These insights are based on recent reports, literature, and market updates. Following this analysis, this review leverages data from a large number of projects related to emerging heat pump innovations supported by the European Innovation Council, to summarise the direction of research and innovation, showcasing real-world examples of projects and startups shaping the future of heat pump technology. Finally, the review identifies non-technical barriers and policy actions needed to accelerate innovation in the field. Heat pumps are essential to achieve to net-zero targets in Europe and enhance European energy autonomy, and this review aims to provide policymakers with evidence-based insights to foster the widespread implementation of heat pumps in energy systems.

Global solar photovoltaic (PV) capacity is growing exponentially, and it is projected to become the dominant renewable energy source by 2050. A significant proportion of PV capacity is deployed as ground-mounted solar parks (SPs), incurring significant land use change, with implications for hosting ecosystems. Despite the rapid deployment of SPs, understanding of their environmental impacts and consequences for ecosystem services (ESs) remains poor. Here, we use a systematic literature review to identify environmental impacts of SPs and derive implications for ES, beyond the benefits that SPs confer over other means of electricity generation. We found 622 pieces of evidence from 167 articles demonstrating a wide range of both positive and negative impacts of SPs on ES, with responses varying with climate, ecosystem type and SP life cycle phase. Dominant positive outcomes included enhanced soil quality regulation in dry climates, and enhanced water cycle support, soil erosion regulation and pollination regulation during the operational phase. Conversely, savanna and grassland ecosystems and the construction phase were more commonly associated with negative outcomes. Further, negative climate regulation outcomes tended to occur in desert ecosystems. Crucially, we highlight significant knowledge gaps, with ⩽20 pieces of evidence for half of all ES, including vital services such as pollination regulation, likely to be impacted by SP land use change. The outcomes of this review could inform site location and management decisions which maximise ecosystem co-benefits and avoid detrimental impacts, providing valuable insight for emerging environmental policies. Ultimately, understanding of the impact of SPs on ES could aid an energy system transition that mitigates the climate and ecological crises.

Nigeria, one of Africa’s largest economies, faces a pressing dual challenge: meeting its rapidly growing electricity demand while transitioning to a net-zero emissions electricity system. Using a stylized capacity expansion model, we explore pathways to a net-zero emissions electricity system by 2050, 2060, and 2070, examining the impacts of restricting firm low-carbon technologies such as nuclear power, gas with carbon capture and storage (gas-CCS), and concentrated solar power. Our results indicate that solar power, both utility-scale and off-grid, will be a pivotal component of Nigeria’s future net-zero electricity mix. Across all net-zero scenarios, solar contributes between 37% and 55% of total electricity generation by 2050, and remains a major source of power in the 2060 and 2070 timeframes as well. Nuclear power plays a pivotal role in scenarios where it is allowed, accounting for 33%–41% of electricity generation by mid-century. In contrast, when nuclear is restricted, the system relies more heavily on gas-CCS and large-scale solar PV deployment. The cost analysis indicates that the transition to net-zero emissions electricity system requires average annual investments ranging from US$7 billion to $10 billion. The total system cost is consistently lower in net-zero emissions scenarios compared to business-as-usual, suggesting that transitioning to net-zero emissions, despite requiring higher initial investments, is more cost-effective in the long term for Nigeria. Earlier transitions do not necessarily lead to drastic higher system costs compared to delayed pathways. Sensitivity analyses reveal that ±25% variations in technology costs for solar, wind, and nuclear significantly influence the technology mix but do not alter the broader conclusion that firm low carbon technologies are vital to cost-effective transitions. We also assess the implications of high electricity demand growth consistent with Nigeria’s Agenda 2050. The study provides actionable insights into the technology, investment, and policy trade-offs facing Nigeria and similar African economies in designing net-zero electricity systems.

To assess the current and likely future role of power electronics in high-voltage transmission, detailed structured technical interviews were conducted with 13 leading experts. Thyristors were seen as a mature technology for which major performance improvements are unlikely because of limited market pull for line commutated converter (LCC-based) systems. In contrast, the performance of Si insulated gate bipolar transistors (IGBTs) used in voltage source converter (VSC-based) systems was predicted to improve due to continued and growing demand. Packaging and reliability of IGBTs were seen as particularly promising areas for improvement. While silicon carbide (SiC) MOSFETs were seen by many as a likely successor to Si IGBTs, the experts’ opinions of the timing for this transition varied. The major hurdles to be overcome include achieving high current/power operation, as well as systematically establishing high reliability that can compete with very mature Si technology. A diversity of views was expressed about present and likely future relative costs of LCC and VSC systems. Several experts argued that the cost of VSC-based converter stations is now at or below the cost of LCC stations. The cost of devices was assessed to be a larger fraction of total cost for VSC than for LCC stations, suggesting that device improvements could further reduce the overall cost of VSC-based high voltage direct current (HVDC) technology. Most experts suggested that high future demand for power electronic devices from transportation and other sectors is unlikely to be a serious impediment to the future growth of HVDC.

The deposition of functional coatings on open-cell foam substrates using magnetron sputtering is gaining popularity, particularly for applications like oxygen evolution reaction/hydrogen evolution reaction catalysis, batteries, and supercapacitors. While most research focuses on performance, little attention has been paid to the coating growth mechanisms or properties within the foam, which could significantly impact device performance. This work investigates the properties and growth mechanisms of TiO₂ coatings inside porous foams, using experimental and modeling techniques. The structure, composition and thickness of the coating on the outermost surface of the foam are studied using focused ion beam (FIB), scanning transmission electron microscopy (STEM), energy-dispersive x-ray spectroscopy (EDS), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The experimental results reveal the formation of a dense, (quasi-)stoichiometric and crystalline coating. Numerical simulations and experiments highlight the transport of plasma particles in the foam. Interestingly, direct simulation Monte Carlo (DSMC)/particle-in-cell Monte Carlo (PICMC) models, coupled with mass-energy analyzer (MEA) experiments, demonstrate that the particle flux is reduced, but the particle energy distribution is not affected while traveling inside the foam. Using kinetic Monte Carlo thin film growth models provided by Virtual Coater^TM, the physical properties of the coating inside the foam have been modeled, and the drop in coating thickness as well as the impact of bias voltage on densification, resistivity, and optical absorption are confirmed. synchrotron x-ray diffraction (SXRD) analyses of the foam demonstrate that the same crystalline phase is obtained along the foam thickness, but it can be tailored with bias voltages. The decrease in the recorded SXRD signal with increasing depth inside the foam also suggests a drop in coating thickness. The new insights on the properties of coatings inside open-cell foams presented in this study can be used to improve future foam-based devices.

The use of biogas as a renewable energy source is expanding rapidly, propelled by increasingly stringent climate policies that reduce fossil-fuel reliance and greenhouse gas emissions. However, trace impurities, particularly siloxanes and sulfur compounds, pose significant challenges to biogas utilization in energy systems. While regulatory standards like EN 16723 set strict limits on these impurities, the absence of standardized, validated methods traceable to reference standards complicates compliance, especially for small- and medium-scale biogas plants without advanced analytical capabilities. This study introduces an accessible method for the simultaneous quantification of siloxanes and condensable sulfur compounds in biogas, utilizing gas chromatography coupled with inductively coupled plasma mass spectrometry (GC-ICP-MS). A liquid quench sampling system (LQ) is employed to preconcentrate and store analytes, enabling biogas plants without specialized analytical tools to collect samples for centralized analysis. By consolidating sulfur and siloxane measurements into a single procedure, the method streamlines the process, reducing both time and complexity compared to conventional approaches. Validated across multiple biogas sources, including digesters and wood gasifiers, this methodolgy improves the understanding of impurity variations due to feedstock, seasonality, and operational factors. By streamlining compliance and plant optimization, the method supports policy goals for renewable gas, while helping valorize biowaste through reliable biomethane production, thereby advancing a circular, low-carbon economy.

This perspective examines trade-offs in designing residential electricity rates that improve economic efficiency while ensuring feasible and distributionally favorable outcomes. We analyze rate structures across three key dimensions: improving economic efficiency by reflecting social marginal costs; ensuring affordability, technology access, and residual cost recovery; and simplicity in customer understanding and implementation. While real-time pricing based on social marginal costs is the most economically efficient choice, intermediate approaches like time-of-use rates or critical peak rates may better balance competing objectives. We recommend that decision-makers (1) move towards pricing environmental externalities in time-varying electricity rates, (2) introduce time-varying rates with predictable price periods gradually, (3) expand access to flexibility enabling technologies for low-income customers, and (4) carefully design fixed charges for residual cost recovery to avoid distributionally regressive impacts. These findings are particularly relevant as utilities nationwide consider rate reforms to support electrification while maintaining ratepayer affordability.

Brazil is a global leader in ethanol production from sugarcane, with corn-based ethanol emerging as a significant alternative. Understanding the technical potential of ethanol production is essential for supporting decarbonization in the energy transition. Therefore, the current study aims to comprehensively review sustainable ethanol production in Brazil, focusing on sugarcane processing and the emerging role of corn-based ethanol. The review includes a brief overview of ethanol production, details on first-generation and second-generation ethanol production, mapping of sugarcane production and biorefineries, an analysis of ethanol carbon intensity (CI), conversion factors for second-generation ethanol production, co-products, bioenergy with carbon capture and storage (BECCS), and finally, an estimate of the ethanol production perspective along with the potential reduction of greenhouse gas emissions. The review indicates that co-products are important, and sustainable ethanol production can be increased by converting degraded pasturelands into agricultural crops or by utilizing second-crop corn in tropical climates. Results show that up to 351.6 M m³ of sugarcane-based ethanol, equivalent to 7.51 EJ or 3.36 M barrels per day of crude oil, can be produced using 28 M ha when both 1G and 2G ethanol production are considered, while 98 M m³ of corn-based ethanol can be produced using corn as a rotational crop, with full allocation for ethanol production. Additionally, implementing BECCS during the fermentation process could lead to cumulative net-negative emissions of 136.6 M tonnes of CO₂, considered as carbon dioxide removal, when assuming an ethanol CI of 15.0 g CO_2-eq/MJ. Finally, an additional reduction of 526 M tonnes of CO₂ per year can be achieved due to the displacement of fossil fuels by ethanol.

Osmotic energy, also known as ‘blue energy’, harnesses the salinity gradient between seawater and freshwater, providing a vast, renewable, and environmentally friendly energy source. The efficiency of osmotic power generation is fundamentally dependent on the performance of ion-exchange membranes, where a critical trade-off exists between ion selectivity and ion permeability, which determine the voltage and current respectively. Recent advances in nanofluidic reverse electrodialysis (NRED) have leveraged nanoconfined spaces and innovative membrane design to significantly minimize resistance and promote energy conversion. In this review, we systematically explore the ion transport mechanisms in nanoconfined spaces, analyze state-of-the-art membrane optimization parameters to balance the selectivity-permeability trade-off. Finally, we discuss current challenges and prospective future directions for membrane innovation in NRED-based osmotic power generation systems, with the ultimate target of facilitating the practical realization of high-performance, commercially viable osmotic power generation.

Heat pumps play a crucial role in the transition toward sustainable energy. This review draws on an extensive range of resources to analyse advancements in heat pump technologies and their contribution to achieving the European Union’s (EU) goals on clean and secure heating/cooling. First, it provides a comprehensive overview of the status and trajectories of heat pump penetration, recent regulations, market growth projections, and supply chain challenges within the EU. Then, the report highlights state-of-the-art technological advancements and innovation trends in areas such as refrigerant and component development, optimal operation, and smart integration with other technologies, including alternative heating and cooling systems, thermal and electrical storage, and solar energy. These insights are based on recent reports, literature, and market updates. Following this analysis, this review leverages data from a large number of projects related to emerging heat pump innovations supported by the European Innovation Council, to summarise the direction of research and innovation, showcasing real-world examples of projects and startups shaping the future of heat pump technology. Finally, the review identifies non-technical barriers and policy actions needed to accelerate innovation in the field. Heat pumps are essential to achieve to net-zero targets in Europe and enhance European energy autonomy, and this review aims to provide policymakers with evidence-based insights to foster the widespread implementation of heat pumps in energy systems.

Its ability to upconvert myriad wet carbonaceous wastes into biofuels and platform chemicals makes hydrothermal liquefaction (HTL) an attractive process to incorporate into a future bioeconomy. However, while HTL is well suited to process feedstocks with high moisture content, it generates a carbon-laden process water (PW). There is considerable research on the state-of-the-field of HTL; the impact of feedstocks and process conditions on products is well established, as are methods to upgrade recovered biocrudes (BCs). However, methods to efficiently separate, recover, and utilize the fugitive carbon in PW are less well understood. We believe this is because of the intrinsic thermodynamic limitations imposed by the PW; PW is a solutropic solution for which liquid–liquid extraction is, depending on the solvent, of minimal utility. Aqueous phase processing and electrocatalytic oxidation could produce high-value products like H₂ for BC upgrading, though issues of catalyst stability and electrode fouling, along with selectivity and efficiency, plague these nascent technologies. The literature is replete with conflicting opinions on the potential to recycle PW in the reactor (some authors find enhancement of hydrochar or BC yield, others no change or a negative impact). The current Edisonian approach to biological treatment (e.g. grow one bacteria on one PW) leaves the field without a clear understanding of the HTL PW compounds that inhibit or promote growth beyond broad classifications. Through this review, we hope to encourage the HTL field to move beyond the current norm of processing singular feedstocks to assess the BC produced and consider the carbon balance of the entire system to develop recovery and valorization pathways for the carbon present in HTL PW.

Global solar photovoltaic (PV) capacity is growing exponentially, and it is projected to become the dominant renewable energy source by 2050. A significant proportion of PV capacity is deployed as ground-mounted solar parks (SPs), incurring significant land use change, with implications for hosting ecosystems. Despite the rapid deployment of SPs, understanding of their environmental impacts and consequences for ecosystem services (ESs) remains poor. Here, we use a systematic literature review to identify environmental impacts of SPs and derive implications for ES, beyond the benefits that SPs confer over other means of electricity generation. We found 622 pieces of evidence from 167 articles demonstrating a wide range of both positive and negative impacts of SPs on ES, with responses varying with climate, ecosystem type and SP life cycle phase. Dominant positive outcomes included enhanced soil quality regulation in dry climates, and enhanced water cycle support, soil erosion regulation and pollination regulation during the operational phase. Conversely, savanna and grassland ecosystems and the construction phase were more commonly associated with negative outcomes. Further, negative climate regulation outcomes tended to occur in desert ecosystems. Crucially, we highlight significant knowledge gaps, with ⩽20 pieces of evidence for half of all ES, including vital services such as pollination regulation, likely to be impacted by SP land use change. The outcomes of this review could inform site location and management decisions which maximise ecosystem co-benefits and avoid detrimental impacts, providing valuable insight for emerging environmental policies. Ultimately, understanding of the impact of SPs on ES could aid an energy system transition that mitigates the climate and ecological crises.

The rapid expansion of low-cost renewable electricity combined with end-use electrification in transport, industry, and buildings offers a promising path to deep decarbonisation. However, aligning variable supply with demand requires strategies for daily and seasonal balancing. Existing models either lack the wide scope required for long-term transition pathways or the spatio-temporal detail to capture power system variability and flexibility. Here, we combine the complementary strengths of REMIND, a long-term integrated assessment model, and PyPSA-Eur, an hourly energy system model, through a bi-directional, price-based and iterative soft coupling. REMIND provides pathway variables such as sectoral electricity demand, installed capacities, and costs to PyPSA-Eur, which returns optimised operational variables such as capacity factors, storage requirements, and relative prices. After sufficient convergence, this integrated approach jointly optimises long-term investment and short-term operation. We demonstrate the coupling for two Germany-focused scenarios, with and without demand-side flexibility, reaching climate neutrality by 2045. Our results confirm that a sector-coupled energy system with nearly 100% renewable electricity is technically possible and economically viable. Power system flexibility influences long-term pathways through price differentiation: supply-side market values vary by generation technology, while demand-side prices vary by end-use sector. Flexible electrolysers and smart-charging electric vehicles benefit from below-average prices, whereas less flexible heat pumps face almost twice the average price due to winter peak loads. Without demand-side flexibility, electricity prices increase across all end-users, though battery deployment partially compensates. By integrating hourly power system dynamics into multi-decadal energy transition pathways, our approach addresses the fundamental trade-off between the wide scope needed for climate policy analysis and the spatio-temporal detail needed for power system planning.

The worsening of climate adversity and the depletion of fossil fuels have led to an alarming situation, requiring urgent intervention to develop greener energy generation and conversion methods. The accelerated development of renewable energy conversion, storage, and conservation technologies is anticipated to play a pivotal role in addressing the looming global energy crisis. Quantum materials are proving to be powerful new tools for advancing research and applications. Over the past two decades, QMs have been found to exhibit size-dependent tunable optical, electronic, and electrochemical. To date, quantum materials (QMs) have demonstrated applications across electronics, energy-related domains, and communication technologies. However, despite the rapid growth of the field, several aspects concerning the synthesis and energy-related applications of QMs have not yet been systematically reviewed in prior studies. In this work, a systematic study has been consolidated on the design of QMs (including quantum dots (QDs), quantum wires (QWs), and quantum sheets/wells (QSs)), through various synthesis techniques, with particular emphasis on their size-dependent characteristics. Recent developments in QMs and their applications in energy conversion (solar cells, photodetectors, LEDs, nanogenerators, and electrocatalysis), energy storage (batteries and supercapacitors), and energy saving (electrochromism) have been highlighted. In addition, the current challenges and future prospects of emerging quantum materials (QMs) for potential multifunctional applications have been systematically summarized.

The rapid expansion of low-cost renewable electricity combined with end-use electrification in transport, industry, and buildings offers a promising path to deep decarbonisation. However, aligning variable supply with demand requires strategies for daily and seasonal balancing. Existing models either lack the wide scope required for long-term transition pathways or the spatio-temporal detail to capture power system variability and flexibility. Here, we combine the complementary strengths of REMIND, a long-term integrated assessment model, and PyPSA-Eur, an hourly energy system model, through a bi-directional, price-based and iterative soft coupling. REMIND provides pathway variables such as sectoral electricity demand, installed capacities, and costs to PyPSA-Eur, which returns optimised operational variables such as capacity factors, storage requirements, and relative prices. After sufficient convergence, this integrated approach jointly optimises long-term investment and short-term operation. We demonstrate the coupling for two Germany-focused scenarios, with and without demand-side flexibility, reaching climate neutrality by 2045. Our results confirm that a sector-coupled energy system with nearly 100% renewable electricity is technically possible and economically viable. Power system flexibility influences long-term pathways through price differentiation: supply-side market values vary by generation technology, while demand-side prices vary by end-use sector. Flexible electrolysers and smart-charging electric vehicles benefit from below-average prices, whereas less flexible heat pumps face almost twice the average price due to winter peak loads. Without demand-side flexibility, electricity prices increase across all end-users, though battery deployment partially compensates. By integrating hourly power system dynamics into multi-decadal energy transition pathways, our approach addresses the fundamental trade-off between the wide scope needed for climate policy analysis and the spatio-temporal detail needed for power system planning.

To assess the current and likely future role of power electronics in high-voltage transmission, detailed structured technical interviews were conducted with 13 leading experts. Thyristors were seen as a mature technology for which major performance improvements are unlikely because of limited market pull for line commutated converter (LCC-based) systems. In contrast, the performance of Si insulated gate bipolar transistors (IGBTs) used in voltage source converter (VSC-based) systems was predicted to improve due to continued and growing demand. Packaging and reliability of IGBTs were seen as particularly promising areas for improvement. While silicon carbide (SiC) MOSFETs were seen by many as a likely successor to Si IGBTs, the experts’ opinions of the timing for this transition varied. The major hurdles to be overcome include achieving high current/power operation, as well as systematically establishing high reliability that can compete with very mature Si technology. A diversity of views was expressed about present and likely future relative costs of LCC and VSC systems. Several experts argued that the cost of VSC-based converter stations is now at or below the cost of LCC stations. The cost of devices was assessed to be a larger fraction of total cost for VSC than for LCC stations, suggesting that device improvements could further reduce the overall cost of VSC-based high voltage direct current (HVDC) technology. Most experts suggested that high future demand for power electronic devices from transportation and other sectors is unlikely to be a serious impediment to the future growth of HVDC.

The use of biogas as a renewable energy source is expanding rapidly, propelled by increasingly stringent climate policies that reduce fossil-fuel reliance and greenhouse gas emissions. However, trace impurities, particularly siloxanes and sulfur compounds, pose significant challenges to biogas utilization in energy systems. While regulatory standards like EN 16723 set strict limits on these impurities, the absence of standardized, validated methods traceable to reference standards complicates compliance, especially for small- and medium-scale biogas plants without advanced analytical capabilities. This study introduces an accessible method for the simultaneous quantification of siloxanes and condensable sulfur compounds in biogas, utilizing gas chromatography coupled with inductively coupled plasma mass spectrometry (GC-ICP-MS). A liquid quench sampling system (LQ) is employed to preconcentrate and store analytes, enabling biogas plants without specialized analytical tools to collect samples for centralized analysis. By consolidating sulfur and siloxane measurements into a single procedure, the method streamlines the process, reducing both time and complexity compared to conventional approaches. Validated across multiple biogas sources, including digesters and wood gasifiers, this methodolgy improves the understanding of impurity variations due to feedstock, seasonality, and operational factors. By streamlining compliance and plant optimization, the method supports policy goals for renewable gas, while helping valorize biowaste through reliable biomethane production, thereby advancing a circular, low-carbon economy.

This perspective examines trade-offs in designing residential electricity rates that improve economic efficiency while ensuring feasible and distributionally favorable outcomes. We analyze rate structures across three key dimensions: improving economic efficiency by reflecting social marginal costs; ensuring affordability, technology access, and residual cost recovery; and simplicity in customer understanding and implementation. While real-time pricing based on social marginal costs is the most economically efficient choice, intermediate approaches like time-of-use rates or critical peak rates may better balance competing objectives. We recommend that decision-makers (1) move towards pricing environmental externalities in time-varying electricity rates, (2) introduce time-varying rates with predictable price periods gradually, (3) expand access to flexibility enabling technologies for low-income customers, and (4) carefully design fixed charges for residual cost recovery to avoid distributionally regressive impacts. These findings are particularly relevant as utilities nationwide consider rate reforms to support electrification while maintaining ratepayer affordability.

Water demand in the United States is projected to increase by up to 140% by 2050 and 220% by 2070 while climate change will reduce the availability of freshwater in large parts of the country. Here we quantify the magnitude of this challenge and define pathways of sustainable water desalination that can satisfy projected deficits between supply and demand on a US county-level. Simulations were conducted using the SEDAT and WaterTAP-REFLO platforms, validated using performance data from pilot or commercial plants (e.g. desalination plants in Plataforma Solar de Almería, Spain and crystallization plants by Veolia Water) and based on publicly available datasets from the US Geological Survey, Sandia National Laboratories, and National Renewable Energy Laboratories. The results showed the potential of desalination technologies with zero liquid discharge, mainly powered by solar and wind energies, sustainably meeting the needs of the municipal, thermoelectric and industrial sectors. This analysis offers a new reference point for supplemental social studies addressing issues and perceptions regarding the sustainability of producing freshwater via desalination.

Hydrogen is not a greenhouse gas, but its interactions with other species in the atmosphere indirectly induce radiative forcing. This study evaluates the relative impacts of hydrogen emissions across 23 different net-zero scenarios from five prominent US economy-wide analyses. Hydrogen emissions associated with venting and leakages across energy supply chains are considered. The magnitude of these energy-related hydrogen emissions is estimated and compared to the remaining positive energy-related carbon dioxide and methane emissions in the 23 US net-zero scenarios. This methodology facilitates consideration of the potential magnitude of hydrogen emissions relative to the other emissions reductions and/or carbon dioxide removal strategies that would be required to balance those hydrogen emissions across a wide range of possible net-zero scenarios. Magnitudes of energy-related hydrogen and methane emissions are estimated for each scenario across a range of possible emissions rates (Low, Central, and High) and global warming potentials based on literature. The results indicate that when evaluated over a 100 year horizon, hydrogen emissions span a range of 0.02–0.15 Gt_CO2e yr⁻¹ and are lower than remaining positive carbon dioxide emissions in the Central emissions case of all 23 scenarios. In the 19 scenarios that do not constrain fossil fuels, hydrogen emissions (0.02–0.11 Gt_CO2e yr⁻¹) account for less than 14% of combined hydrogen, methane, and carbon dioxide emissions. The four scenarios that constrain fossil fuels have higher levels of hydrogen consumption and correspondingly higher levels of hydrogen emissions (0.10–0.15 Gt_CO2e yr⁻¹). These results suggest that hydrogen emissions are non-negligible in net-zero energy systems; however, the potential climate impacts associated with hydrogen emissions can be balanced through relatively small reductions in remaining positive emissions and/or increases in carbon dioxide removal. Further effort is needed to advance hydrogen emissions measurement, quantification, and mitigation strategies to maximize the potential climate benefits of hydrogen for decarbonization.

Green hydrogen is projected to play a key role in achieving net-zero emissions, with applications across various sectors. While hydrogen applications have been assessed on costs, competitiveness and feasibility, it is unclear which applications are most favourable for the climate. Here, we use prospective life cycle assessment to compare the greenhouse gas emissions of green hydrogen use in various applications with: (i) their fossil counterparts, and (ii) low-emission alternatives for these applications, which are other mitigation technologies that provide the same service. Specifically, we look at methanol, ammonia, steel, aviation fuel, passenger cars, long-term grid balancing, and domestic and industrial heat production for the year 2030. We demonstrate that green hydrogen production, transport and application leads to emissions savings compared to their fossil counterparts, but emissions are similar or higher than those of the low-emission alternatives. Only with very low hydrogen production emissions and without transport do the green hydrogen-based applications result in net emissions savings compared to the low-emission alternatives for: ammonia, steel, long-term grid balancing, and industrial and domestic heat. We conclude that for green hydrogen to fulfil its anticipated role in the net-zero transition, emission reductions are needed across the supply chain, as well as a prioritisation of hydrogen use in different applications that accounts for and optimises climate benefits.

Heat pumps play a crucial role in the transition toward sustainable energy. This review draws on an extensive range of resources to analyse advancements in heat pump technologies and their contribution to achieving the European Union’s (EU) goals on clean and secure heating/cooling. First, it provides a comprehensive overview of the status and trajectories of heat pump penetration, recent regulations, market growth projections, and supply chain challenges within the EU. Then, the report highlights state-of-the-art technological advancements and innovation trends in areas such as refrigerant and component development, optimal operation, and smart integration with other technologies, including alternative heating and cooling systems, thermal and electrical storage, and solar energy. These insights are based on recent reports, literature, and market updates. Following this analysis, this review leverages data from a large number of projects related to emerging heat pump innovations supported by the European Innovation Council, to summarise the direction of research and innovation, showcasing real-world examples of projects and startups shaping the future of heat pump technology. Finally, the review identifies non-technical barriers and policy actions needed to accelerate innovation in the field. Heat pumps are essential to achieve to net-zero targets in Europe and enhance European energy autonomy, and this review aims to provide policymakers with evidence-based insights to foster the widespread implementation of heat pumps in energy systems.

Its ability to upconvert myriad wet carbonaceous wastes into biofuels and platform chemicals makes hydrothermal liquefaction (HTL) an attractive process to incorporate into a future bioeconomy. However, while HTL is well suited to process feedstocks with high moisture content, it generates a carbon-laden process water (PW). There is considerable research on the state-of-the-field of HTL; the impact of feedstocks and process conditions on products is well established, as are methods to upgrade recovered biocrudes (BCs). However, methods to efficiently separate, recover, and utilize the fugitive carbon in PW are less well understood. We believe this is because of the intrinsic thermodynamic limitations imposed by the PW; PW is a solutropic solution for which liquid–liquid extraction is, depending on the solvent, of minimal utility. Aqueous phase processing and electrocatalytic oxidation could produce high-value products like H₂ for BC upgrading, though issues of catalyst stability and electrode fouling, along with selectivity and efficiency, plague these nascent technologies. The literature is replete with conflicting opinions on the potential to recycle PW in the reactor (some authors find enhancement of hydrochar or BC yield, others no change or a negative impact). The current Edisonian approach to biological treatment (e.g. grow one bacteria on one PW) leaves the field without a clear understanding of the HTL PW compounds that inhibit or promote growth beyond broad classifications. Through this review, we hope to encourage the HTL field to move beyond the current norm of processing singular feedstocks to assess the BC produced and consider the carbon balance of the entire system to develop recovery and valorization pathways for the carbon present in HTL PW.

Global solar photovoltaic (PV) capacity is growing exponentially, and it is projected to become the dominant renewable energy source by 2050. A significant proportion of PV capacity is deployed as ground-mounted solar parks (SPs), incurring significant land use change, with implications for hosting ecosystems. Despite the rapid deployment of SPs, understanding of their environmental impacts and consequences for ecosystem services (ESs) remains poor. Here, we use a systematic literature review to identify environmental impacts of SPs and derive implications for ES, beyond the benefits that SPs confer over other means of electricity generation. We found 622 pieces of evidence from 167 articles demonstrating a wide range of both positive and negative impacts of SPs on ES, with responses varying with climate, ecosystem type and SP life cycle phase. Dominant positive outcomes included enhanced soil quality regulation in dry climates, and enhanced water cycle support, soil erosion regulation and pollination regulation during the operational phase. Conversely, savanna and grassland ecosystems and the construction phase were more commonly associated with negative outcomes. Further, negative climate regulation outcomes tended to occur in desert ecosystems. Crucially, we highlight significant knowledge gaps, with ⩽20 pieces of evidence for half of all ES, including vital services such as pollination regulation, likely to be impacted by SP land use change. The outcomes of this review could inform site location and management decisions which maximise ecosystem co-benefits and avoid detrimental impacts, providing valuable insight for emerging environmental policies. Ultimately, understanding of the impact of SPs on ES could aid an energy system transition that mitigates the climate and ecological crises.

Direct air capture (DAC) can provide an impactful, engineered approach to combat climate change by removing carbon dioxide (CO₂) from the air. However, to meet climate goals, DAC needs to be scaled at a rapid rate. Current DAC approaches use engineered contactors filled with chemicals to repeatedly capture CO₂ from the air and release high purity CO₂ that can be stored or otherwise used. This review article focuses on two distinctive, commercial DAC processes to bind with CO₂: solid sorbents and liquid solvents. We discuss the properties of solvents and sorbents, including mass transfer, heat transfer and chemical kinetics, as well as how these properties influence the design and cost of the DAC process. Further, we provide a novel overview of the considerations for deploying these DAC technologies, including concepts for learning-by-doing that may drive down costs and material requirements for scaling up DAC technologies.

The need for storage in electricity systems is increasing because large amounts of variable solar and wind generation capacity are being deployed. About two thirds of net global annual power capacity additions are solar and wind. Pumped hydro energy storage (PHES) comprises about 96% of global storage power capacity and 99% of global storage energy volume. Batteries occupy most of the balance of the electricity storage market including utility, home and electric vehicle batteries. Batteries are rapidly falling in price and can compete with pumped hydro for short-term storage (minutes to hours). However, pumped hydro continues to be much cheaper for large-scale energy storage (several hours to weeks). Most existing pumped hydro storage is river-based in conjunction with hydroelectric generation. Water can be pumped from a lower to an upper reservoir during times of low demand and the stored energy can be recovered at a later time. In the future, the vast storage opportunities available in closed loop off-river pumped hydro systems will be utilized. In such systems water is cycled repeatedly between two closely spaced small reservoirs located away from a river. This review covers the technology, cost, environmental impacts and opportunities for PHES. The key motivations for this review are firstly that large amounts of variable wind and solar generators are being deployed; and secondly that there are vast opportunities for low-cost pumped hydro storage that do not require interference with rivers (with the associated environmental cost).

Electric vehicles (EVs) are experiencing a rise in popularity over the past few years as the technology has matured and costs have declined, and support for clean transportation has promoted awareness, increased charging opportunities, and facilitated EV adoption. Suitably, a vast body of literature has been produced exploring various facets of EVs and their role in transportation and energy systems. This paper provides a timely and comprehensive review of scientific studies looking at various aspects of EVs, including: (a) an overview of the status of the light-duty-EV market and current projections for future adoption; (b) insights on market opportunities beyond light-duty EVs; (c) a review of cost and performance evolution for batteries, power electronics, and electric machines that are key components of EV success; (d) charging-infrastructure status with a focus on modeling and studies that are used to project charging-infrastructure requirements and the economics of public charging; (e) an overview of the impact of EV charging on power systems at multiple scales, ranging from bulk power systems to distribution networks; (f) insights into life-cycle cost and emissions studies focusing on EVs; and (g) future expectations and synergies between EVs and other emerging trends and technologies. The goal of this paper is to provide readers with a snapshot of the current state of the art and help navigate this vast literature by comparing studies critically and comprehensively and synthesizing general insights. This detailed review paints a positive picture for the future of EVs for on-road transportation, and the authors remain hopeful that remaining technology, regulatory, societal, behavioral, and business-model barriers can be addressed over time to support a transition toward cleaner, more efficient, and affordable transportation solutions for all.

Sodium-ion batteries (SIBs) are one of the most promising alternatives to lithium-ion batteries (LIBs), due to the much more abundant resources of Na compared with Li in the world. Developing SIB technology to satisfy the increased demand for energy storage is therefore a significant task . However, one of the biggest bottlenecks is the design of high-performance and low-cost anode materials, since the graphite anode in commercial LIBs is not suitable for SIBs due to thermal dynamic issues. Hard carbon materials have been regarded as having the greatest potential as anodes in commercial SIBs owing to their excellent cost-effectiveness, but their relatively limited performance compared to the graphite in LIBs as well as the dimness of the sodium storage mechanisms still need further investigation. In this review, we summarize the progress of recent research into hard carbons for SIB applications, including the fundamentals of SIBs, sodium storage mechanisms, structures and the electrochemical performances of different types of hard carbons in SIBs and other types of sodium-based energy storage as well as the main challenges in this field. We aim to provide a general insight into hard carbons and their applications in SIBs, opening up future perspectives and possible research directions.

Physics-based electrochemical battery models derived from porous electrode theory are a very powerful tool for understanding lithium-ion batteries, as well as for improving their design and management. Different model fidelity, and thus model complexity, is needed for different applications. For example, in battery design we can afford longer computational times and the use of powerful computers, while for real-time battery control (e.g. in electric vehicles) we need to perform very fast calculations using simple devices. For this reason, simplified models that retain most of the features at a lower computational cost are widely used. Even though in the literature we often find these simplified models posed independently, leading to inconsistencies between models, they can actually be derived from more complicated models using a unified and systematic framework. In this review, we showcase this reductive framework, starting from a high-fidelity microscale model and reducing it all the way down to the single particle model, deriving in the process other common models, such as the Doyle–Fuller–Newman model. We also provide a critical discussion on the advantages and shortcomings of each of the models, which can aid model selection for a particular application. Finally, we provide an overview of possible extensions to the models, with a special focus on thermal models. Any of these extensions could be incorporated into the microscale model and the reductive framework re-applied to lead to a new generation of simplified, multi-physics models.

In an era of U.S. energy abundance, the persistently high energy bills paid by low-income households is troubling. After decades of weatherization and bill-payment programs, low-income households still spend a higher percent of their income on electricity and gas bills than any other income group. Their energy burden is not declining, and it remains persistently high in particular geographies such as the South, rural America, and minority communities. As public agencies and utilities attempt to transition to a sustainable energy future, many of the programs that promote energy efficiency, rooftop solar, electric vehicles, and home batteries are largely inaccessible to low-income households due to affordability barriers. This review describes the ecosystem of stakeholders and programs, and identifies promising opportunities to address low-income energy affordability, such as behavioral economics, data analytics, and leveraging health care benefits. Scalable approaches require linking programs and policies to tackle the complex web of causes and impacts faced by financially constrained households.

The share of electricity generated by intermittent renewable energy sources is increasing (now at 26% of global electricity generation) and the requirements of affordable, reliable and secure energy supply designate grid-scale storage as an imperative component of most energy transition pathways. The most widely deployed bulk energy storage solution is pumped-hydro energy storage (PHES), however, this technology is geographically constrained. Alternatively, flow batteries are location independent and have higher energy densities than PHES, but remain associated with high costs and short lifetimes, which highlights the importance of developing and utilizing additional larger-scale, longer-duration and long-lifetime energy storage alternatives. In this paper, we review a class of promising bulk energy storage technologies based on thermo-mechanical principles, which includes: compressed-air energy storage, liquid-air energy storage and pumped-thermal electricity storage. The thermodynamic principles upon which these thermo-mechanical energy storage (TMES) technologies are based are discussed and a synopsis of recent progress in their development is presented, assessing their ability to provide reliable and cost-effective solutions. The current performance and future prospects of TMES systems are examined within a unified framework and a thermo-economic analysis is conducted to explore their competitiveness relative to each other as well as when compared to PHES and battery systems. This includes carefully selected thermodynamic and economic methodologies for estimating the component costs of each configuration in order to provide a detailed and fair comparison at various system sizes. The analysis reveals that the technical and economic characteristics of TMES systems are such that, especially at higher discharge power ratings and longer discharge durations, they can offer promising performance (round-trip efficiencies higher than 60%) along with long lifetimes (>30 years), low specific costs (often below 100 $ kWh⁻¹), low ecological footprints and unique sector-coupling features compared to other storage options. TMES systems have significant potential for further progress and the thermo-economic comparisons in this paper can be used as a benchmark for their future evolution.

Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 ‘Energy Storage and Conversion based on Hydrogen’ of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group ‘Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage’. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage.

Intense literature and research efforts have focussed on the exploration of complex hydrides for energy storage applications over the past decades. A focus was dedicated to the determination of their thermodynamic and hydrogen storage properties, due to their high gravimetric and volumetric hydrogen storage capacities, but their application has been limited because of harsh working conditions for reversible hydrogen release and uptake. The present review aims at appraising the recent advances on different complex hydride systems, coming from the proficient collaborative activities in the past years from the research groups led by the experts of the Task 40 ‘Energy Storage and Conversion Based on Hydrogen’ of the Hydrogen Technology Collaboration Programme of the International Energy Agency. An overview of materials design, synthesis, tailoring and modelling approaches, hydrogen release and uptake mechanisms and thermodynamic aspects are reviewed to define new trends and suggest new possible applications for these highly tuneable materials.

Electrofuels, fuels produced from electricity, water, and carbon or nitrogen, are of interest as substitutes for fossil fuels in all energy and chemical sectors. This paper focuses on electrofuels for transportation, where some can be used in existing vehicle/vessel/aircraft fleets and fueling infrastructure. The aim of this study is to review publications on electrofuels and summarize costs and environmental performance. A special case, denoted as bio-electrofuels, involves hydrogen supplementing existing biomethane production (e.g. anaerobic digestion) to generate additional or different fuels. We use costs, identified in the literature, to calculate harmonized production costs for a range of electrofuels and bio-electrofuels. Results from the harmonized calculations show that bio-electrofuels generally have lower costs than electrofuels produced using captured carbon. Lowest costs are found for liquefied bio-electro-methane, bio-electro-methanol, and bio-electro-dimethyl ether. The highest cost is for electro-jet fuel. All analyzed fuels have the potential for long-term production costs in the range 90–160 € MWh⁻¹. Dominant factors impacting production costs are electrolyzer and electricity costs, the latter connected to capacity factors (CFs) and cost for hydrogen storage. Electrofuel production costs also depend on regional conditions for renewable electricity generation, which are analyzed in sensitivity analyses using corresponding CFs in four European regions. Results show a production cost range for electro-methanol of 76–118 € MWh⁻¹ depending on scenario and region assuming an electrolyzer CAPEX of 300–450 € kW_elec⁻¹ and CFs of 45%–65%. Lowest production costs are found in regions with good conditions for renewable electricity, such as Ireland and western Spain. The choice of system boundary has a large impact on the environmental assessments. The literature is not consistent regarding the environmental impact from different CO₂ sources. The literature, however, points to the fact that renewable energy sources are required to achieve low global warming impact over the electrofuel life cycle.