Efficient storage of hydrogen is one of the biggest challenges towards a potential hydrogen economy. Hydrogen storage in liquid carriers is an attractive alternative to compression or liquefaction at low temperatures. Liquid carriers can be stored cost-effectively and transportation and distribution can be integrated into existing infrastructures. The development of efficient liquid carriers is part of the work of the International Energy Agency Task 40: Hydrogen-Based Energy Storage. Here, we report the state-of-the-art for ammonia and closed CO2-cycle methanol-based storage options as well for liquid organic hydrogen carriers.

Characterization and identification of recombination active defects in photovoltaic (PV) materials are essential for improving the performance of solar cells, hence, reducing their levelized cost of electricity. Injection dependent lifetime spectroscopy (IDLS) is a sensitive and widely used technique for investigating defects in silicon. With the development of carrier lifetime measurement techniques and analysis methods, IDLS has gained increasing popularity within the PV research community. In this paper, we review IDLS, from measurement techniques and systems, to existing and emerging defect parameterization methods. We also discuss the limitations and potential pitfalls of lifetime spectroscopy analysis and outline the possible approaches for improvement.

The urgent demand for energy structural reform and the limitations of single energy development have promoted the combination of wind energy and wave energy. A hybrid energy system means that two or more energy devices share the same foundation. It reduces the levelized cost of energy and improves competitiveness through infrastructure sharing and increased power output. This paper starts with the development of the joint resources of wind and wave energies, then introduces the foundation forms of the hybrid system. It reviews the latest concepts and devices proposed with the integration of wind energy and wave energy, according to the foundation forms, and makes a preliminary assessment of the synergies of the hybrid system. The existing study methods of the hybrid systems are summarized. In view of the challenges faced by the development of hybrid energy systems, several suggestions are put forward accordingly. This paper provides a comprehensive guideline for the future development of the hybrid wind-wave energy converter system.

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.

Redox flow batteries (RFBs) with decoupling energy and power, high safety, long durability and easy scalability have been considered as giant promising candidates for large-scale energy storage systems. As a key component of RFBs, the electrodes provide active sites for the conversion between electrical and chemical energies. Thus, the electrochemical properties of both the positive and negative electrodes are significantly important to the performance of batteries, especially the energy efficiency and the power. Therefore, improving the electrochemical performance of electrodes by effective modifications is essential for the advancements of RFBs. With high conductivity, high activity and stability, metal-based electrocatalysts have been widely used to modify and increase the electrochemical activities of electrodes in RFBs. This review summarizes and discusses the applications of metal-based electrocatalysts modified carbon-based electrodes of RFBs in a wide pH range (the acidic, alkaline and neutral electrolytes), including the characterizations of physicochemical and electrochemical properties of electrodes, the cell performance, the merits, and limitations.

In the last decade and longer, photovoltaic module manufacturers have experienced a rapidly growing market along with a dramatic decrease in module prices. Such cost pressures have resulted in a drive to develop and implement new module designs, which either increase performance and/or lifetime of the modules or decrease the cost to produce them. In this paper, the main motivations and benefits but also challenges for material innovations will be discussed. Many of these innovations include the use of new and novel materials in place of more conventional materials or designs. As a result, modules are being produced and sold without a long-term understanding about the performance and reliability of these new materials. This has led to unexpected new failure mechanisms occurring few years after deployment, such as potential induced degradation or backsheet cracking. None of these failure modes have been detected after the back then common single stress tests. New accelerated test approaches are based on a combination or sequence of multiple stressors that better reflect outdoor conditions. That allows for identification of new degradation modes linked to new module materials or module designs.

The development of efficient storage systems is one of the keys to the success of the energy transition. There are many ways to store energy, but among them, electrochemical storage is particularly valuable because it can store electrons produced by renewable energies with a very good efficiency. However, the solutions currently available on the market remain unsuitable in terms of storage capacity, recharging kinetics, durability, and cost. Technological breakthroughs are therefore expected to meet the growing need for energy storage. Within the framework of the Hydrogen Technology Collaboration Program—H2TCP Task-40, IEA’s expert researchers have developed innovative materials based on hydrides (metallic or complex) offering new solutions in the field of solid electrolytes and anodes for alkaline and ionic batteries. This review presents the state of the art of research in this field, from the most fundamental aspects to the applications in battery prototypes.

Photovoltaics (PV), or solar electricity generation, has become the cheapest form of energy in many locations worldwide and, combined with energy storage, has the potential to satisfy most of our electricity needs. PV has grown at an annual compounded growth rate of approximately 30% in the last three decades. Solar energy systems will continue their impressive growth in distributed energy, microgrids, and utility scale, as efforts are made for dependable electricity in an age with increasing extreme weather. However, within this remarkable success lies a new challenge. The growth curve, combined with rapid product innovation and scale up, means that the majority of PV systems are new, without the three years of performance data that have been required in the past to estimate product lifetime. PV reliability has to address this challenge. In this review we present a brief summary of PV reliability starting with brief historical synopsis, detailing some of the technological challenges and present a framework required for long lifetime.

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 € kWelec −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.

There is about to be an abrupt step-change in the use of coastal seas around the globe, specifically by the addition of large-scale offshore renewable energy (ORE) developments to combat climate change. Developing this sustainable energy supply will require trade-offs between both direct and indirect environmental effects, as well as spatial conflicts with marine uses like shipping, fishing, and recreation. However, the nexus between drivers, such as changes in the bio-physical environment from the introduction of structures and extraction of energy, and the consequent impacts on ecosystem services delivery and natural capital assets is poorly understood and rarely considered through a whole ecosystem perspective. Future marine planning needs to assess these changes as part of national policy level assessments but also to inform practitioners about the benefits and trade-offs between different uses of natural resources when making decisions to balance environmental and energy sustainability and socio-economic impacts. To address this shortfall, we propose an ecosystem-based natural capital evaluation framework that builds on a dynamic Bayesian modelling approach which accounts for the multiplicity of interactions between physical (e.g. bottom temperature), biological (e.g. net primary production) indicators and anthropogenic marine use (i.e. fishing) and their changes across space and over time. The proposed assessment framework measures ecosystem change, changes in ecosystem goods and services and changes in socio-economic value in response to ORE deployment scenarios as well as climate change, to provide objective information for decision processes seeking to integrate new uses into our marine ecosystems. Such a framework has the potential of exploring the likely outcomes in the same metrics (both ecological and socio-economic) from alternative management and climate scenarios, such that objective judgements and decisions can be made, as to how to balance the benefits and trade-offs between a range of marine uses to deliver long-term environmental sustainability, economic benefits, and social welfare.

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.

Liquid air energy storage (LAES) uses air as both the storage medium and working fluid, and it falls into the broad category of thermo-mechanical energy storage technologies. The LAES technology offers several advantages including high energy density and scalability, cost-competitiveness and non-geographical constraints, and hence has attracted a growing interest in recent years. As a result, several reviews have been published on the topic. However, these reviews covered little in the following aspects of LAES: dynamic simulation and optimisation, key components for LAES, LAES applications through integration, and unified economic and cost models for LAES. This article provides a comprehensive review on the LAES technology and fills the above gaps. Apart from applications in electrical grids such as peak-shaving, load shifting, and dealing with intermittency of renewable generation, the review also shows a diverse range of other LAES applications through integration, including waste heat and cold energy recovery and utilisation, multi-energy vector service provision, and sector coupling for chemical production and carbon capture. The review also leads to the recommendation of several areas for future research and development, including dynamic characteristics of whole LAES system integrated with renewables and end users; thermo-economic and dynamic optimization of stand-alone LAES and integrated systems; and experimental study on commercial systems.

Solar photovoltaic (PV) installations have increased exponentially over the last decade and are now at a stage where they provide humanity with the greatest opportunity to mitigate accelerating climate change. For the continued growth and success of PV energy the reliable inspection of solar power plants is an important requirement. This ensures the installations are of high quality, safe to operate, and produce the maximum possible power for the longest possible plant life. Outdoor luminescence imaging of field-deployed PV modules provides module image data with unparalleled fidelity and is therefore the gold standard for assessing the quality, defect types, and degradation state of field-deployed PV modules. Several luminescence imaging methods have been developed and some of them are already routinely used to inspect solar power plants. The preferred luminescence inspection method to be used depends on the required image resolution, the defect types that need to be identified, cost, inspection throughput, technological readiness, and other factors. Due to the rich and detailed information provided by luminescence imaging measurements and modern image analysis methods, luminescence imaging is becoming an increasingly important tool for PV module quality assurance in PV power plants. Outdoor luminescence imaging can make valuable contributions to the commissioning, operation, and assessment of solar power plants prior to a change of ownership or after severe weather events. Another increasingly important use of these technologies is the cost-effective end-of-life assessment of solar modules to enable a sustainable circular economy.

Progress in the development of fusion energy has gained momentum in recent years. However, questions remain across key subject areas that will affect the path to commercial fusion energy. The purpose of this review is to expose socio-economic areas that need further research, and from this assist in making recommendations to the fusion community, (and policy makers and regulators) in order to redirect and orient fusion for commercialisation: When commercialised, what form does it take? Where does it fit into a future energy system? Compared to other technologies, how much will fusion cost? Why do it? When is it likely that fusion reaches commercialisation? Investigations that have sought to answer these questions carry looming uncertainty, mainly stemming from the techno-economics of emerging fusion technology in the private sector, and due to the potential for applications outside of electricity generation coming into consideration. Such topics covered include hydrogen, desalination, and process-heat applications.

This review work presents an overview of the innovations shaping today’s photovoltaic (PV) operations and maintenance sector by summarising literature and current research. After a brief introduction to the market dynamics and state-of-the-art best practices, relevant insights are provided into emerging fields and key research directions are identified, such as the adaptation and application of the building information modelling concept and digital twins, which are topics already proven to help other industries to render processes more efficient, reduce costs and risks throughout the entire lifecycle of a project. Moreover, it explores new approaches on Supervisory Control and Data Acquisition architectures for remote monitoring of PV assets, highlighting the promising role of 5G wireless technologies such as Narrow Band Internet of things. Finally, concerned about the growing amount of PV waste due to the exponential growth of installed capacity on a global scale, this article covers relevant Circular Economy approaches being adapted to PV, pointing out the most significant research and development efforts that are pushing towards a more sustainable, environmentally friendly and economically viable end of life management for modules and balance of system.

Our global economy based on burning fossil fuels reached a turning point in the 2020s as problems arising from climate change are becoming increasingly evident. An important strategy to decrease anthropogenic CO2 emission relies on carbon capture and storage (CCS). However, the challenges associated with long-term storage of CO2 in the gas phase highlight the need for a viable Chemical Fixation of CO2. In this scenario, electrochemistry gains prominence since electricity from renewable sources can provide the electrons needed for CO2 electroreduction. The main drawback is the high stability of CO2, the most oxidized form of carbon. Our intention in this Perspective is to give a concise overview of CO2 electroreduction, focusing on why working in the gas phase may help overcome mass transport limitations due to the low solubility of CO2 and how the chemical environment can affect selectivity and activity. We also explore a carbon-emission analysis applied to a CO2 electrochemical system. To do so, we assumed a Brazilian scenario, that is, the carbon footprint associated with electricity generation in the country. Since Brazil relies on more renewable energy sources, an electrochemical reactor that converts CO2 to oxalate with a conversion efficiency (CE) of 20% is enough to result in CO2 abatement, that is, an oxalate production with a negative carbon footprint. Compared with the United States of America, such a system would need to operate at higher CE, 50%, to produce similar results. These results evidence how intricate the implementation of an electrochemical plant is with the carbon footprint of the electricity source.

The cumulative installed capacity of photovoltaics has passed 1 TW, of which about two-thirds were only installed in the past five years. Many of these new installations incorporate novel module and cell designs that have not yet been subjected to long-term in-field characterization. Indoor accelerated stress testing has historically been a valuable methodology to identify fault mechanisms, estimate degradation rates, and to ensure the safety and normal operation of modules in the field. Still, these methodologies deliver an incomplete image of the exact stress mechanisms that photovoltaic systems are subject to outdoors, which vary with location, time of day, and time of year. In this work we review different outdoor methods to measure current–voltage (I–V) characteristics of photovoltaic systems, discuss how the environmental conditions impact those characteristics, and examine alternative methodologies for acquiring light and pseudo I–V characteristics more applicable to larger scale installations. This review also provides an insight into methods useful for real-time monitoring and degradation analysis at the module and string level.

Battery safety is a critical factor in the design of electrified vehicles. As such, understanding the battery responses under extreme conditions have gained a lot of interest. Previously, abuse tolerance tests were applied to measure the safety metrics of different types of batteries. Nevertheless, conducting these tests in various conditions is usually expensive and time consuming. Computational modeling, on the other hand, provides an efficient and cost-effective tool to evaluate battery performance during abuse, and therefore has been widely used in optimizing the battery system design. In this Perspective, we discuss the main progresses and challenges in battery safety modeling. In particular, we divide the battery safety models into two groups according to the stage in a typical battery failure process. The first group focuses on predicting the failure conditions of batteries in different scenarios, while the second one aims to evaluate the hazard after the onset of battery failure like thermal runaway. Although the models in these groups serve different purposes, they are intercorrelated and their combination provides a better understanding of the failure process of a battery system. The framework, capabilities, and limitations of typical models in each group are presented here. The main challenges in building battery safety models and their future development and applications are also discussed.

Aluminum (Al) metal has long been known to function as an anode in lithium-ion batteries (LIBs) owing to its high capacity, low potential, and effective suppression of dendrite growth. However, seemingly intrinsic degradation during cycling has made it less attractive throughout the years compared to graphitic carbon, silicon-blends, and more recently lithium metal itself. Nevertheless, with the recent unprecedented growth of the LIB industry, this review aims to revisit Al as an anode material, particularly in light of important advancements in understanding the electrochemical Li-Al system, as well as the growth of activity in solid-state batteries where cell designs may conveniently mitigate problems found in traditional liquid cells. Furthermore, this review culminates by highlighting several non-trivial points including: (1) prelithiatied Al anodes, with β-LiAl serving as an intercalation host, can be effectively immortal, depending on formation and cycling conditions; (2) the common knowledge of Al having a capacity of 993 mAh g−1 is inaccurate and attributed to kinetic limitations, thus silicon and lithium should not stand alone as the only ‘high-capacity’ candidates in the roadmap for future lithium-ion cells; (3) replacement of Cu current collectors with Al-based foil anodes may simplify LIB manufacturing and has important safety implications due to the galvanic stability of Al at high potentials vs. Li/Li+. Irrespective of the type of Li-ion device of interest, this review may be useful for those in the broader community to enhance their understanding of general alloy anode behavior, as the methodologies reported here can be extended to non-Al anodes and consequently, even to Na-ion and K-ion devices.