Progress in Energy

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.

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).

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.

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.

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.

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 global shift towards low-carbon economies and societies is expected to result in a substantial surge in the demand for critical minerals. Endowed with at least a fifth of the world's reserves in a dozen minerals, Africa can play a pivotal role in facilitating the global transition away from fossil fuels. In this paper, we argue that, for this to happen, Africa needs to act now to convert its natural assets into sustainable comparative advantages for a resource-based industrialisation. This will require proactive measures to ensure strict compliance with the highest standards of governance and transparency, as well as to uphold social values such as safeguarding basic rights of affected individuals and communities and sound environmental management to avoid falling into a new resource curse. This also requires a renewed global raw material diplomacy in which Africa manages the geopolitics of critical minerals, identifying strategic global alliances to unleash economic potential, create local content in the mining sector, develop domestic productive capacity, and foster sustainable development.

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.

Thermal conductivity is a crucial material property for a diverse range of energy technologies, ranging from thermal management of high power electronics to thermal insulation for building envelopes. This review discusses recent advances in achieving high and low thermal conductivity (k) as relevant for energy applications, from high-k heat spreaders to low-k insulation. We begin with a brief introduction to the physics of heat conduction from both theoretical and computational perspectives. The heart of the review is a survey of recent advances in high- and low-k materials. The discussion of good heat conductors for thermal management includes inorganics and polymers in both bulk and low dimensional forms. For insulators, the discussion covers the effects of chemical composition, crystal structure, and defects and porosity. Promising areas for future research in both fundamental materials science and engineering technologies are noted.

The production of freshwater from desalinating abundant saline water on the planet is increasingly considered a climate change adaptation measure. Yet, there are challenges associated with the high cost, intensive energy demand, and environmental implications of desalination. Effective integration of solar energy generation and freshwater production can address both issues. This review article highlights recent key advances in such integration achieved in a joint-research university-national laboratory partnership under the auspices of the United States Department of Energy and parallel efforts worldwide. First, an overview of current and emerging desalination technologies and associated pretreatment, brine treatment, and valorization technologies that together can result in zero-liquid-discharge systems is presented, and their technological readiness levels are evaluated. Then, advanced modeling techniques and new software platforms that enable optimization of solar-desalination applications with the dual objective of cost and environmental impact minimization are discussed.

Low-income countries (LICs) have long benefitted from household biogas plants for the extraction of clean energy and fertilizers. Despite their popularity, such ordinary plants do not have heating systems and suffer from low biogas production in cold regions or during winter. This paper presents a comprehensive review of the research and development of household biogas technology in cold climates. This review specifically highlights the influence of temperature on biogas production and technologies, as well as recent advances in psychrophilic biogas production. These measures include the introduction of adapted inocula, maneuvering operational parameters (such as hydraulic retention time and organic loading rate), co-digestion approach and additives, and digester designs. In addition, this review shows that the adoption of low-cost heating arrangements, including the construction of a greenhouse over biodigesters, digester insulation, and integration of solar heating, is crucial for enhancing biogas production. Furthermore, this review identified gaps in the operation of biodigesters under psychrophilic temperature in LICs and recommends operational consistencies in full-scale psychrophilic biogas plants through the development of standards, operational guidelines, and user training.

The global shift towards low-carbon economies and societies is expected to result in a substantial surge in the demand for critical minerals. Endowed with at least a fifth of the world's reserves in a dozen minerals, Africa can play a pivotal role in facilitating the global transition away from fossil fuels. In this paper, we argue that, for this to happen, Africa needs to act now to convert its natural assets into sustainable comparative advantages for a resource-based industrialisation. This will require proactive measures to ensure strict compliance with the highest standards of governance and transparency, as well as to uphold social values such as safeguarding basic rights of affected individuals and communities and sound environmental management to avoid falling into a new resource curse. This also requires a renewed global raw material diplomacy in which Africa manages the geopolitics of critical minerals, identifying strategic global alliances to unleash economic potential, create local content in the mining sector, develop domestic productive capacity, and foster sustainable development.

Protonic ceramic cells (PCCs) offer variety of potential applications for electrochemical energy conversion, however a lot of challenges remain in the development of PCCs for industrial scale manufacturing processes. As it was successfully demonstrated for the solid oxide cells, metal supported architecture is a good alternative for PCCs with many attractive advantages in terms of stabilities in operation and reduction of raw critical materials. In this review, proposed architectures, component materials and processing options are summarized. The challenges and prospects are discussed.

Rapid decarbonization of the transportation system is needed to address global climate change, and electrification of the transportation sector will likely be an important strategy to achieve decarbonization goals. While electrification is an effective approach to reducing carbon emissions, it may result in environmental justice consequences that need to be tackled. We discuss four categories of related issues: air quality and health-related equity; technology access; equitable infrastructure development; and a just global supply chain. In regions where grid decarbonization is well under way, transport-related disparities in air quality and health are expected to decrease with electrification. In contrast, in regions that still rely heavily on coal generation, disparities may increase, putting further strain on low-income communities and people of color. The high upfront cost of electric vehicles and limited access to charging present additional challenges for achieving equity in transportation electrification. Meeting the electricity demand of a fully electric vehicle fleet will require rapid expansion of power generation, transmission, and distribution capacity, and the location and design of this infrastructure will have further impacts on communities where it is sited. Here, we offer a perspective on these emerging environmental justice issues at the intersection of transportation and electricity systems and provide policy recommendations and future research directions for electrified transportation. We suggest there is a need for policies targeting electrification and power sector decarbonization in tandem, assessment of barriers to electric vehicle adoption in different groups, development of strategies for community inclusion in infrastructure development decisions, and creation of frameworks to assess equity tradeoffs along the global supply chain supporting electric vehicles and renewable energy technologies.

The production of freshwater from desalinating abundant saline water on the planet is increasingly considered a climate change adaptation measure. Yet, there are challenges associated with the high cost, intensive energy demand, and environmental implications of desalination. Effective integration of solar energy generation and freshwater production can address both issues. This review article highlights recent key advances in such integration achieved in a joint-research university-national laboratory partnership under the auspices of the United States Department of Energy and parallel efforts worldwide. First, an overview of current and emerging desalination technologies and associated pretreatment, brine treatment, and valorization technologies that together can result in zero-liquid-discharge systems is presented, and their technological readiness levels are evaluated. Then, advanced modeling techniques and new software platforms that enable optimization of solar-desalination applications with the dual objective of cost and environmental impact minimization are discussed.

Low-income countries (LICs) have long benefitted from household biogas plants for the extraction of clean energy and fertilizers. Despite their popularity, such ordinary plants do not have heating systems and suffer from low biogas production in cold regions or during winter. This paper presents a comprehensive review of the research and development of household biogas technology in cold climates. This review specifically highlights the influence of temperature on biogas production and technologies, as well as recent advances in psychrophilic biogas production. These measures include the introduction of adapted inocula, maneuvering operational parameters (such as hydraulic retention time and organic loading rate), co-digestion approach and additives, and digester designs. In addition, this review shows that the adoption of low-cost heating arrangements, including the construction of a greenhouse over biodigesters, digester insulation, and integration of solar heating, is crucial for enhancing biogas production. Furthermore, this review identified gaps in the operation of biodigesters under psychrophilic temperature in LICs and recommends operational consistencies in full-scale psychrophilic biogas plants through the development of standards, operational guidelines, and user training.

Protonic ceramic cells (PCCs) offer variety of potential applications for electrochemical energy conversion, however a lot of challenges remain in the development of PCCs for industrial scale manufacturing processes. As it was successfully demonstrated for the solid oxide cells, metal supported architecture is a good alternative for PCCs with many attractive advantages in terms of stabilities in operation and reduction of raw critical materials. In this review, proposed architectures, component materials and processing options are summarized. The challenges and prospects are discussed.

Contactless detection with a camera of radiation emitted from silicon solar cells resulting from band-to-band recombination after charge carrier excitation with an illumination source, i.e. photoluminescence (PL) imaging, has shown a great potential in the laboratory setting. In the recent years, the first approaches to PL imaging in the outdoor setting have been conducted on silicon modules with the Sun, a LED module and laser as excitation sources. The reason for these attempts has been that fault detection in photovoltaic (PV) modules using imaging can be more efficient and accurate than fault detection using electrical parameters. Developments in fault detection and localization are necessary because accurate monitoring of solar plants is expected to be one of the critical tasks facing the energy industry, when one considers that PV energy conversion will be the largest installed power capacity by 2027 and that the utility-scale solar PV electricity generation will be the least costly option for new electricity generation in many of the world's countries. The present study sums up the different methods for outdoor PL imaging and emphasizes their differences regarding filtering of the reflected excitation light from the PL signal. The different types of PL images obtained from each method and the image processing algorithms are described. Finally, the interpretation of the different types of PL images is addressed.

This review presents a state-of-the-art literature review of automatic generation control (AGC) control strategies for power systems containing renewable energy sources. The incorporation of renewable energy into the power system has a large impact on the stability, reliability, economy and security of the power system. To mitigate these effects, it is important to choose a suitable control strategy for AGC. However, there is a limited amount of literature available on the review of AGC in renewable energy power systems, so a review of AGC control strategies for renewable energy-containing power systems is necessary. The investigation of this paper focuses on all kinds of different AGC control strategies for renewable energy-containing power systems, such as proportional integral derivative control, fuzzy control, artificial neural network control, etc, and compares and considers these different control methods, while this paper summarises the power system models with/without renewable energy. In addition, this paper summarises and discusses the application of intelligent optimization algorithms and energy storage systems to control strategies. The problems and future research directions of the current research on power systems with renewable energy sources are also discussed.

The production of freshwater from desalinating abundant saline water on the planet is increasingly considered a climate change adaptation measure. Yet, there are challenges associated with the high cost, intensive energy demand, and environmental implications of desalination. Effective integration of solar energy generation and freshwater production can address both issues. This review article highlights recent key advances in such integration achieved in a joint-research university-national laboratory partnership under the auspices of the United States Department of Energy and parallel efforts worldwide. First, an overview of current and emerging desalination technologies and associated pretreatment, brine treatment, and valorization technologies that together can result in zero-liquid-discharge systems is presented, and their technological readiness levels are evaluated. Then, advanced modeling techniques and new software platforms that enable optimization of solar-desalination applications with the dual objective of cost and environmental impact minimization are discussed.

The global shift towards low-carbon economies and societies is expected to result in a substantial surge in the demand for critical minerals. Endowed with at least a fifth of the world's reserves in a dozen minerals, Africa can play a pivotal role in facilitating the global transition away from fossil fuels. In this paper, we argue that, for this to happen, Africa needs to act now to convert its natural assets into sustainable comparative advantages for a resource-based industrialisation. This will require proactive measures to ensure strict compliance with the highest standards of governance and transparency, as well as to uphold social values such as safeguarding basic rights of affected individuals and communities and sound environmental management to avoid falling into a new resource curse. This also requires a renewed global raw material diplomacy in which Africa manages the geopolitics of critical minerals, identifying strategic global alliances to unleash economic potential, create local content in the mining sector, develop domestic productive capacity, and foster sustainable development.

The shift toward electric vehicles (EVs) as a decarbonization strategy in transportation raises important energy justice concerns, particularly regarding fair access to charging infrastructure. This perspective synthesizes evidence on how access to, and experience of, charging infrastructure may differ across socio-economic groups across North America. We present a framework for assessing charging infrastructure equity that includes: (i) accessibility—proximity, reliability, visibility, affordability; and (ii) user experiences related to safety, payment ease, and co-located other services. The framework helps characterize the varied impacts across socio-demographic groups, including on low-income and marginalized communities. We explore how the direct and indirect effects of accessibility and user experience might influence the distribution and design of EV charging stations. Considerations of socio-economic diversity in the deployment of charging infrastructure are critical to ensure equitable benefits from electric mobility. We conclude that targeted actions from manufacturers, charging operators, and governments are needed to alleviate the disparities in access and experiences with public EV charging.

Protonic ceramic cells (PCCs) offer variety of potential applications for electrochemical energy conversion, however a lot of challenges remain in the development of PCCs for industrial scale manufacturing processes. As it was successfully demonstrated for the solid oxide cells, metal supported architecture is a good alternative for PCCs with many attractive advantages in terms of stabilities in operation and reduction of raw critical materials. In this review, proposed architectures, component materials and processing options are summarized. The challenges and prospects are discussed.

Contactless detection with a camera of radiation emitted from silicon solar cells resulting from band-to-band recombination after charge carrier excitation with an illumination source, i.e. photoluminescence (PL) imaging, has shown a great potential in the laboratory setting. In the recent years, the first approaches to PL imaging in the outdoor setting have been conducted on silicon modules with the Sun, a LED module and laser as excitation sources. The reason for these attempts has been that fault detection in photovoltaic (PV) modules using imaging can be more efficient and accurate than fault detection using electrical parameters. Developments in fault detection and localization are necessary because accurate monitoring of solar plants is expected to be one of the critical tasks facing the energy industry, when one considers that PV energy conversion will be the largest installed power capacity by 2027 and that the utility-scale solar PV electricity generation will be the least costly option for new electricity generation in many of the world's countries. The present study sums up the different methods for outdoor PL imaging and emphasizes their differences regarding filtering of the reflected excitation light from the PL signal. The different types of PL images obtained from each method and the image processing algorithms are described. Finally, the interpretation of the different types of PL images is addressed.

Extreme weather events, such as high winds, storms, flooding and temperature extremes, are a major cause of disruption to the supply of electricity to consumers. System Operators (SOs) are responsible for ensuring stable real-time operation of large-scale power networks, and will act to prevent adverse impacts of such events on consumer supply, contain the extent of supply interruptions that do occur, and restore supply to affected consumers in an efficient and timely manner. SOs will also generally be involved in some way in the long-term planning of the transmission network and generation capacity required to ensure future resilience. In this paper we review some of the strategies adopted by SOs across the globe in ensuring high levels of reliability and resilience to extreme weather, with reference to learning generated from specific recent events. In the face of the potential for both the frequency of such events and for their consequent impacts to increase in the future, we recommend that regulatory control of investment in networks is informed by quantified understanding of the climate-energy interface, including assessment of the potential frequency and impacts of future weather events and shared learning from events experienced by different operators. The statutory role of utilities should include robust assessment of future weather-related risks and appropriate investment in their asset resilience, as well as assisting in the preparedness of supporting agencies to mitigate the impacts of weather-related disturbances on energy consumers.

Energy system models do not represent natural processes but are assumption-laden representations of complex engineered systems, making validation practically impossible. Post-normal science argues that in such cases, it is important to communicate embedded values and uncertainties, rather than establishing whether a model is 'true' or 'correct'. Here, we examine how open energy modelling can achieve this aim by thinking about what 'a model' is and how it can be broken up into manageable parts. Collaboration on such building blocks—whether they are primarily code or primarily data—could become a bigger focus area for the energy modelling community. This collaboration may also include harmonisation and intercomparison of building blocks, rather than full models themselves. The aim is understandability, which will make life easier for modellers themselves (by making it easier to develop and apply problem-specific models) as well as for users far away from the modelling process (by making it easier to understand what is qualitatively happening in a model—without putting undue burden on the modellers to document every detail).

This paper reviews the state-of-the-art of research on African energy transitions and pinpoints critical questions that require answering to allow science-based policymaking. It both highlights unique elements of energy transitions research in the African context, and explains why these need deeper investigation to enable decisions informed by clear and objective country-specific analysis. In doing so, it pinpoints clear areas of future study that are urgently needed at the country level to enable science-informed policy.

The uptake of solar photovoltaic (PV) panels for the generation of clean energy has almost exponentially increased over the past 10 years and can be expected to further exponentially increase until 2030. Organisations like the International Renewable Energy Agency have clearly outlined the need and benefits of robust end-of-life (EoL) management legislations, such as a product stewardship scheme or extended producer responsibility, to cope with the significant expected waste volume arising from solar PV panels during the next 30 years or so. However, effective EoL management legislation is still not existing in many countries despite having significant solar PV capacity installed. This article explores a possible strategy for a product stewardship legislation for solar PV panels including options for necessary levies to support an emerging recycling industry for solar panels. Given that currently almost 3 billion solar PV panels are installed worldwide, considerations are also given for a legislation which supports and encourages a second hand economy for solar PV panels.

New efficient redox flow batteries (RFBs) are currently of great interest for large-scale storage of renewable energy. Further development requires the improvement of the redox active materials. Quantum chemical calculations allow the screening of large numbers of redox active molecules for required static molecular properties. In particular, redox potentials are calculated in high-throughput studies. In addition, calculations of solubility and reactivity and in-depth electronic structure analysis are performed for smaller numbers of molecules. In this review, we provide an overview of the static theoretical investigations carried out on the known classes of molecules that are considered as redox active materials in RFBs. We will focus on electronic structure methods such as density functional theory and wave function-based methods. Furthermore, investigations using the increasingly important machine learning techniques are presented. For each class of redox active molecules considered, significant theoretical results are presented and discussed. In addition, the different quantum chemical approaches used are examined, in particular with regard to their advantages and limitations. Another focus of this review is the comparison of theoretically predicted results with available experimental studies. Finally, future challenges and trends in the theoretical studies of redox active materials are highlighted.