Ammonia is emerging as a viable alternative to fossil fuels in combustion systems, aiding in the reduction of carbon emissions. However, its use faces challenges, including NOx emissions and low flame speed. Innovative approaches and technologies have significantly advanced the development and implementation of ammonia as a zero-carbon fuel. This review explores current advancements in using ammonia as a fuel substitute, highlighting the complexities that various systems need to overcome before reaching full commercial maturity in support of practical decarbonising global strategies. Different from other reviews, this article incorporates insights of various industrial partners currently working towards green ammonia technologies. The work further addresses fundamental complexities of ammonia combustion, crucial for its practical and industrial implementation in various types of equipment.

The carbon reduction effect of bio-based levulinic acid chemicals is a matter of concern. This work reports the life cycle assessment of methyl levulinate based on local biomass refineries in China. The final LCA results showed that the entire life cycle of methyl levulinate could reduce by approximately 24% of carbon emissions compared with fossil diesel of equal quality. To address the lack of effective uncertainty analysis in current LCA research on levulinic acid chemicals, this study conducted a comprehensive and detailed assessment of inventory data and utilized Taylor series expansion to obtain uncertainty of the LCA results. When connected to a localized background database, the LCA results showed high credibility. According to the sensitivity analysis and Aspen optimization results, further technical improvement schemes are proposed, including improving thermal efficiency, use of clean electricity, and use of clean methanol. Prospective analysis shows that combined implementation of the above strategies can further reduce the existing carbon emissions by more than half.

The Loess Critical Zone (LCZ) is located in the intersection of bedrock, groundwater, pedosphere, atmosphere and biosphere. It is a key issue to understand the structural characteristics and soil carbon (C) cycle of the LCZ. We summarized the mechanisms of C exchange between rocks and the atmosphere, and discussed the mechanisms of C stabilization and persistence of the LCZ. Due to the deep layer, C stocks of the CLZ could be underestimated. In light of the recent theory of microbial C pump, soil microorganisms play an important role in C cycle, however, the microbial function is not widely considered in C cycling model of the LCZ. For future studies, it is suggested to systematically study the C cycling process from plant canopy to bedrock by the framework system of the LCZ. A variety of techniques and methods are integrated to combine short-term and high-frequency observations with long-term positioning observations, and pay attention to the response and feedback mechanisms of soil organic C (SOC) cycling to global changes and human activities, especially the migration and transformation of SOC in each circle and interface of the LCZ. We also recommend the necessity for intensive and long-term C monitoring in LCZ over broad geographic scale, to improve microbial C model for accurately evaluating terrestrial C budget and its dynamics. Altogether, this is the first review of C cycling, spanning from the land surface down to the bedrock in the LCZ, which is significant implications for biogeochemical cycling of C in surface and deep layers down to the bedrock.

The potential for recycling graphitic carbon from lithium-ion battery (LIB) anodes has been overlooked due to its relatively low economic value in applications. This study proposed to use graphene nanoplates (GNPs), which were obtained from spent lithium battery anode graphite, treated with ball-milling method, for hydrothermal synthesis of MnO₂-supported graphene nanoplates (MnO₂/GNPs) composites materials. The composites exhibited excellent electrochemical characterization curves, indicating ideal capacitance characteristics. The analysis of MG24-20 material showed the good impact resistance and capacity retention around 100% with capacitance of 124.6F/g at 10 mV/s, surpassed similar samples using precious metals and high-end materials, enabling the reuse of spent graphite in energy conversion and storage system for effective utility.

The utilization of biochar derived from biomass residue to enhance anaerobic digestion (AD) for bioenergy recovery offers a sustainable approach to advance sustainable energy and mitigate climate change. However, conducting comprehensive research on the optimal conditions for AD experiments with biochar addition poses a challenge due to diverse experimental objectives. Machine learning (ML) has demonstrated its effectiveness in addressing this issue. Therefore, it is essential to provide an overview of current ML-optimized energy recovery processes for biochar-enhanced AD in order to facilitate a more systematic utilization of ML tools. This review comprehensively examines the material and energy flow of biochar preparation and its impact on AD is comprehension reviewed to optimize biochar-enhanced bioenergy recovery from a production process perspective. Specifically, it summarizes the application of the ML techniques, based on artificial intelligence, for predicting biochar yield and properties of biomass residues, as well as their utilization in AD. Overall, this review offers a comprehensive analysis to address the current challenges in biochar utilization and sustainable energy recovery. In future research, it is crucial to tackle the challenges that hinder the implementation of biochar in pilot-scale reactors. It is recommended to further investigate the correlation between the physicochemical properties of biochar and the bioenergy recovery process. Additionally, enhancing the role of ML throughout the entire biochar-enhanced bioenergy recovery process holds promise for achieving economically and environmentally optimized bioenergy recovery efficiency.

Multi-stage reverse electrodialysis (MSRED) offers a promising way for efficient salinity gradient energy harvesting. Here, an improved model of the MSRED system under serial control strategy is proposed. The technical-economic analysis is conducted with considering discount, depreciation and different regional tax and electricity price levels under the maximum net power output conditions. Results reveal that net power output and energy efficiency both increase first with increasing stage numbers, reach their maximum values, and then decrease. For 5 M/0.05 M solutions, the optimal net power output of 4.98 kW is obtained at the stage number n = 12. The optimal stage number corresponding to the maximum net power increases with increasing feed solution concentrations. Due to the compromise between net power generation and capital cost, there exist optimal stage numbers leading to the lowest LCOE and largest NPV, respectively. Higher feed solution concentration can significantly decrease the system LCOE and increase the NPV. The optimal stage number corresponding to the maximum NPV increases with increasing feed solution concentrations. In Germany, for 5 M/0.05 M solutions, the lowest LCOE of 0.061 €·kWh⁻¹ is achieved at n = 3 while the highest NPV over the system lifecycle of 52,005 € is obtained at n = 8. Lower tax, higher electricity price, appropriate membrane price and stage numbers, and high salinity gradient sources can significantly accelerate the commercial completeness of the MSRED systems.

Ammonia serves as an irreplaceable raw material for nitrogen fertilizers, which is essential for global food production. In addition, it has been recently endowed with a new function as a carrier of renewable energy, demonstrating significant research prospects. However, the highly developed ammonia industry results in abundant nitrogenous wastes in nature, thus causing severe nitrogen pollution and disrupting the global nitrogen cycle. The environmentally friendly electrocatalytic technologies for upcycling nitrogenous wastes to green ammonia represent a highly valuable transformation strategy. In this review, we present three effective pathways for the electrocatalytic reduction of nitrogenous wastes to green ammonia, including nitrate reduction reaction (NO₃RR), nitrite reduction reaction (NO₂RR), and nitric oxide reduction reaction (NORR). Furthermore, achievements and challenges associated with electrocatalysts for green ammonia synthesis are discussed in terms of noble metal-based electrocatalysts, non-noble metal-based electrocatalysts, and metal-free electrocatalysts. Moreover, this review provides a systematic perspective on reaction mechanisms, catalyst design, and future developments, offering new insights and prospects for the value-upgrading cycle of nitrogenous substances. By exploring the potential of green ammonia synthesis, we aim to contribute to the development of sustainable and environmentally friendly ammonia production.

China is committed to the targets of achieving peak CO₂ emissions around 2030 and realizing carbon neutrality around 2060. To realize carbon neutrality, people are seeking to replace fossil fuel with renewable energy. Thermal energy storage is the key to overcoming the intermittence and fluctuation of renewable energy utilization. In this paper, the relation between renewable energy and thermal energy storage is first addressed. Then, the classifications of thermal energy storage and Carnot batteries are given. The aim of this review is to provide an insight into the promising thermal energy storage technologies for the application of renewable energy in order to realize carbon neutrality. Three types of heat storage methods, especially latent heat storage and thermochemical heat storage, are analyzed in detail. The application of thermal energy storage is influenced by many heat storage properties, such as temperature range, heat storage capacity, cost, stability, and technical readiness. Therefore, the heat storage properties for different heat storage technologies are reviewed and compared. The advantage and challenge of different heat storage technologies and Carnot batteries for carbon neutrality processes are analyzed. Finally, the prospects of different heat storage technologies are summarized.

Thermal-integrated pumped thermal electricity storage (TI-PTES) could realize efficient energy storage for fluctuating and intermittent renewable energy. However, the boundary conditions of TI-PTES may frequently change with the variation of times and seasons, which causes a tremendous deterioration to the operating performance. To realize efficient and flexible energy storage in operating conditions, a novel composition-adjustable TI-PTES is proposed, and the operating performance is investigated and compared with composition-fixed TI-PTES. Simulation results show that, compared to composition-fixed TI-PTES, the energy storage efficiency of TI-PTES could be enhanced by the absolute value of 4.4-18.3% by introducing composition adjustment method under various boundary conditions. Besides, tuning sub-system composition could simultaneously adjust the capacities of power input, heat storage and power output, realizing a more flexible operating range for TI-PTES. A case study for an isolated energy community shows that composition-adjustable TI-PTES could realize 100% conversion of off-peak electric energy and reduce daily investment by 35.6% compared with composition-fixed TI-PTES.

Heat pumps are a solution for decarbonising home heating in the UK. However, the readiness of UK homes for heat pumps is an area of concern regarding the policies aimed at increasing heat pump adoption. This work combines multiple perspectives in evaluating the technical readiness of homes with the market readiness of installers and homeowners to proceed with installing heat pumps. The effectiveness of past heating and energy efficiency policies in the UK are reviewed, along with building regulations, incentives to promote energy efficiency and the effectiveness of heat pump technology in heating homes. Current policies support the cost of a heat pump but home improvements to make homes ‘heat pump-ready’ can be necessary to achieve optimal heat pump system performance.

Sodium-ion batteries are considered one of the perspective alternatives to lithium-ion batteries due to their affordability and plentiful supply of sodium. However, traditional sodium-ion batteries that use organic electrolytes pose a threat to public safety and the ecological environment. As a result, aqueous electrolytes with high safety and cost-effectiveness are becoming more popular. Unfortunately, typically aqueous electrolytes face limitations in ionic conductivity and have relatively high freezing points, which hinder their ability to function at extremely low temperatures. These issues can be resolved with an easy-to-use method called electrolyte additive. The research on electrolyte additives for subzero-temperature aqueous sodium-ion batteries has not been systematically reviewed at present. This review aims to provide a comprehensive summary of the electrolyte additives for subzero-temperature aqueous sodium-ion batteries. Furthermore, the potential development paths of electrolyte additives to promote the advancement of electrochemical energy storage are also explored.

Demethoxylation was kinetically and spectroscopically studied over three catalysts with different Ru⁰/Ru^δ+ ratios. In-situ spectroscopic tests demonstrated that the synergy between Ru⁰ and Ru^δ+ was crucial, and Ru⁰ was in charge of H₂ activation and adsorption of aromatic ring while Ru^δ+ adsorbed with O in methoxyl. A Langmuir-Hinshelwood kinetic model was proposed, and ratio of Ru⁰/Ru^δ+ was the key in deciding the rate-determining step (RDS): i) desorption of toluene was RDS over catalyst with high Ru⁰ ratio; ii) dissociation of H₂ was RDS over Ru^δ+ enriched catalyst; iii) demethoxylation was rate-determined by CO water-gas shift (WGS) when Ru⁰/Ru^δ+ approached ~ 1. The best performance was obtained over Ru/NiAl₂O₄-200, which effectively enabled both C-O bond activation and rapid recovery of adsorption sites for aromatic rings. Finally, in-situ DRIFT studies on methoxy decomposition and CO-WGS unraveled that the electronic composition of Ru was more stable in Ru/NiAl₂O₄-200 which contributes to its excellence.

The state of New York admitted 143 million metric tons of carbon emissions from fossil fuels in 2020, prompting the ambitious goal set by the CLCPA to achieve carbon neutrality. The paper focused on analyzing and predicting carbon emissions using four different machine-learning algorithms. It examined emissions from fossil fuel combustion from 1990 to 2020 and validated four different algorithms to choose the most effective one for predicting emissions from 2020 to 2050. The analysis covered various economic sectors including transportation, residential, commercial, industrial, and electric power. By analyzing policies, the paper forecasted emissions for 2030 and 2050, leading to the identification of different pathways to reach carbon neutrality. The research concluded that in order to achieve neutrality, radical measures must be taken by the state of New York. Additionally, the paper compared the most recent data for 2021 with the forecasts, showing that significant measures need to be implemented to achieve the goal of carbon neutrality. Despite some studies assuming a trend of decreased emissions, the research revealed different results. The paper presents three pathways, two of which follow the ambitious plan to reach carbon neutrality. As a result, the emission amount by 2050 for the different pathways was projected to be 31.1, 22.4, and 111.95 of MMt CO₂ e, showcasing the need for urgent action to combat climate change.

This paper provides an overview of financial economics-based research on carbon risk with an emphasis on corporate finance. In the corporate finance literature, carbon risk refers to the impact of society’s transition to a low-carbon economy on firm value due to tightening regulations, changing consumer preferences, reputational damage, etc. We focus on the links between carbon risk and different firm performance factors, such as firm risk, cost of capital, financial performance, firm value, and corporate decisions. Although research on carbon risk is still emerging in the corporate finance field, the amount of literature on this topic has been increasing, especially in the last 2 years. We find that some results are robust, while others are mixed. This indicates that conflicting hypotheses still exist, leading to a need for more in-depth exploration.

Climate change is an ever-present issue, which has a vast variety of potential solutions, one of which being carbon capture. This paper aims to use bibliometric analysis techniques to find trends in carbon capture within the technologies of adsorption, absorption, membranes, and hybrid technologies. The Web of Science core collection database performed bibliometric searches, with the ‘Bibliometrix’ plug-in for R software, performing the bibliometric analysis. Bibliometric data spanned across 1997-2020 and the investigation found that adsorption technologies dominated this period in terms of citations and articles, with hybrid technologies being the least produced but rising in scientific productivity and citations. The Analysis found China and the United States of America to be the dominant producers of articles, with global collaboration being central to carbon capture. The ‘International Journal of Greenhouse Gas Control’ ranked as the top producer of articles however, the ‘ACS Applied Materials & Interfaces’ was the leading journal in terms of H-index.

With the excessive use of fossil energy and concern for environmental protection, biomass gasification as an effective means of biomass energy utilization has received widespread attention worldwide. Supercritical carbon dioxide (SCCO₂) (T ≥ 31.26 °C, P ≥ 72.9 atm) has the advantages of near liquid density and high solubility, and the supercritical carbon dioxide gasification of biomass will be a promising technology. However, there has been no research on the technology at present. In this work, experimental study on supercritical carbon dioxide gasification of biomass were carried out in a batch reactor. The influences of temperature, residence time, the amount of carbon dioxide and catalyst on gas yield and fraction were investigated. Experimental results showed that the gas yield and carbon gasification efficiency (CE) of biomass gasification increased with increasing temperature, reaction time or the amount of carbon dioxide. As the gasification temperature increased from 700 °C to 900 °C, the gas yield increased from 23.53 to 50.24 mol/kg biomass and CE increased from 47.26% to 94.53% in CO₂ atmosphere at 30 min. The gasification efficiency of biomass was greatly improved with catalyst, and the effect of impregnated catalyst was better than that of mechanical mixing. The gas yield increased from 23.72 to 50.24 mol/kg biomass with the increasing of the equivalent ratio from 0 to 1 at 900 °C and 30 min. Finally, a detailed supercritical carbon dioxide gasification mechanism of biomass was proposed.

The large-scale vegetation restoration project on the Loess Plateau increased the ecosystem carbon (C) stocks and affected C budget in arid and semi-arid ecosystems. The specific details affecting the C stocks, their distribution, and dependence on land use and climate were never presented and generalized. We assessed the effects of climate factors and soil properties on ecosystem C stocks through field investigation across the Loess Plateau. The total C stocks in the four ecosystems: forestlands [0.36], shrublands [0.24], grasslands [1.18], and farmlands [1.05] was 2.84 Pg (1 Pg = 10¹⁵ g), among which 30% were stored in topsoil (0-20 cm), 53% in above-ground biomass, and 17% in roots. The total ecosystem C density decreased according to the climate from the southeast (warm dry) to the northwest (cold moist) of the Loess Plateau. The ecosystem C density decreased with increasing temperature (from 5 to 15 °C), but increased with precipitation (from 200 to 700 mm). Variation partitioning analysis and structural equation models indicated that ecosystem C density was more explained by climate compared with soil properties. This supports the theory and empirical findings that large scale pattern of ecosystem C density is predominantly regulated by climate on the Loess Plateau. Our results highlight that grasslands are more predestined to store C compared with the other ecosystems, and the C stored in roots is substantial and should be considered when assessing C stocks and strongly contributes to soil organic matter formation. We suggest that investing in roots can be an effective strategy for meeting part of Loess Plateau C reduction goals to mitigate climate change, which is necessary for validating and parameterizing C models worldwide.

The conversion of CO₂ into fuels and valuable chemicals presents a viable path toward carbon neutrality. The aim of this study is to investigate the potential of metal-doped graphene catalysts in the reduction of CO₂ to C₁ products. 20 typical M-graphene (M = metal) catalysts were established based on DFT calculations. Six candidate catalysts, i.e., V-, Cr-, Mn-, Ni-, Mo-, and Ta-graphene catalysts, were selected by combining the hydrogen dissociation ability and the energy band gap of the catalysts. Subsequently, the adsorption characteristics and hydrogenation reactions of CO₂ over the six candidates were explored. CO₂ tends to adsorb at the M site through vertical adsorption and carbon-oxygen co-adsorption. V- and Cr-graphene catalysts promote the production of intermediate COOH, whereas Mn-, Ni-, Mo-, and Ta-doped surfaces are more favorable for HCOO formation. Concerning the hydrogenation to CO and HCOOH, V-, Cr-, Ni- and Mo-graphene catalysts preferentially yield CO from COOH, whereas Ta-doped graphene favors the formation of HCOOH. In total, the competitive hydrogenation of CO₂ reveals the selectivity of the C₁ products. Cr- and Ni-graphene favor the production of HCOOH and CH₃OH, whereas V-, Mn-, Mo-, and Ta-graphene primarily yield CH₃OH.

Development of suitable hole transport materials is vital for perovskite solar cells (PSCs) to diminish the energy barrier and minimize the potential loss. Here, a low-cost hole transport molecule named SFX-POCCF3 (23.72 $/g) is designed with a spiro[fluorene-9,9'-xanthene] (SFX) core and terminated by trifluoroethoxy units. Benefiting from the suitable energy level, high hole mobility, and better charge extraction and transport, the PSCs based on SFX-POCCF3 exhibit improved open-circuit voltage by 0.02 V, therefore, the PSC device based on SFX-POCCF3 exhibits a champion PCE of 21.48%, which is comparable with the control device of Spiro-OMeTAD (21.39%). More importantly, the SFX-POCCF3 based PSC possesses outstanding light stability, which retains 95% of the initial efficiency after about 1,000 h continuous light soaking, which is in accordance with the result continuous output at maximum power point. Whereas, Spiro-OMeTAD witnesses a rapid decrease to 80% of its original efficiency after 100 h light soaking. This work demonstrated that an efficient alignment of energy levels between HTL and perovskite will lead to significant highly efficient PSCs with remarkably enhanced light stability.

Nigeria, at the 2021 Conference of Parties (COP26) meeting in Glasgow announced a commitment to transitioning her carbon economy to reach net-zero by 2060. One year after, the country’s drive for carbon neutrality is shrouded with uncertainties despite numerous policies targeted at it. This study employed the Multilevel Perspective (MLP) and PESTLE (Political, Economic, Social, Technological, Legal, Environmental) analytical framework to assess the politics of low-carbon transition in Nigeria. We used a triangulation of literature review, document analysis, and survey to build the theoretical, historical, and empirical bases for the enquiry. The findings show that the current low-carbon transition process is characterised by few potential drivers and many barriers with critical uncertainty effects. The key drivers are: Nigeria’s potentials for carbon sink/nature-based solutions; vast renewable energy resources; strong niche market demand; and huge opportunities for employment in the renewable energy sector. The major barriers are: poor management of the energy regime; weak infrastructural base; dependence on global climate fund; fossil fuel-based economy; cost of renewable energy options; and impacts of climate change, among others. The barriers with critical impacts outweigh the potential drivers at the ratio of 4:1 thereby playing greater role in characterizing Nigeria’s transition pathway as the ‘reconfiguration transition pathway’ within the ‘emergent transformation context.’ Therefore, unless the identified regime barriers are eliminated, the current transition pathway may not deliver the low-carbon targets. Considering the huge mitigation potentials of Nigeria’s vast forests and natural ecosystem for carbon sink, the study recommends investment in nature-based solutions in synergy with energy system management as the most convenient and cost-effective pathway to attaining carbon neutrality by 2060.

Solar energy is the most sustainable alternative to fossil fuels. The production of solar thermochemical fuels from water/carbon dioxide not only overcomes the intermittent nature of solar energy, but also allows for flexible transportation and distribution. In this paper, the challenges for solar thermochemical H₂/CO production are reviewed. New perspectives and insights to overcome these challenges are presented. For two-step cycles, the main challenges are high temperatures, low conversions and the intensive oxygen removal work. Theoretically feasible temperature and pressure ranges are needed to develop reactant materials. The fundamental mechanism to reduce the temperature and the potential to improve the efficiency by minimizing the oxygen removal work need be revealed. Various material modification strategies and advanced reactors are proposed to improve the efficiency by reducing the temperature and enhancing heat transfer process. But the oxygen removal work required has not been minimized. For multi-step cycles, the main challenges are the separation of corrosive acid and insufficient reaction kinetics. For the separation of acids, many methods have been proposed. But these methods require extra energy and causes undesired side reactions or byproducts. The reaction kinetics have been enhanced by improving catalysts with noble materials or complex fabrication methods. Developing novel multi-step cycles using metal oxides, hydroxides and carbonates may be promising.

Photovoltaic/thermal (PV/T) utilization has been regarded as a promising technique to efficiently harvest solar energy, but its thermal efficiency highly degrades in cold seasons because of remarkable heat loss. Although various methods, such as using air or vacuum gap, have been used to reduce heat loss of the PV/T, heat radiative loss still exists. In addition, unlike selective solar absorbers, the current PV/T absorber behaves like an infrared blackbody, showing great radiative heat loss. To overcome this drawback, a novel aerogel PV/T (referred to as “A-PV/T” hereinafter) collector based on solar transparent and thermally insulated silica aerogel is proposed, which can reduce the heat loss from both the non-radiative and radiative heat transfer modes. Experimental testing demonstrates that the thermal efficiency improvement of 25.1%-348% can be achieved for PV/T within the collecting temperature range of 35-70 °C when silica aerogel is introduced, indicating a significant efficiency enhancement. Compared with traditional PV/T (referred to as “T-PV/T” hereinafter) collector, the stagnation temperatures of the A-PV/T collector are 96.7 °C and 103.1 °C in outdoor and indoor environments, which are 27.4 °C and 25.8 °C greater, respectively, indicating a heat loss suppression of the aerogel. Moreover, simulation reveals that useful heat can hardly be provided by the T-PV/T collector in cold seasons, but the A-PV/T still exists a high solar thermal performance, showing good seasonal and regional applicability.

Sodium ion batteries (SIBs) have attracted great interest as candidates in stationary energy storage systems relying on low cost, high abundance and outstanding electrochemical properties. The foremost challenge in advanced NIBs lies in developing high-performance and low-cost electrode materials. To accelerate the commercialization of sodium ion batteries, various types of materials are being developed to meet the increasing energy demand. O3-type layered oxide cathode materials show great potential for commercial applications due to their high reversible capacity, moderate operating voltage and easy synthesis, while allowing direct matching of the negative electrode to assemble a full battery. Here, representative progress for Ni/Fe/Mn based O3-type cathode materials have been summarized, and existing problems, challenges and solutions are presented. In addition, the effects of irreversible phase transitions, air stability, structural distortion and ion migration on electrochemical performance are systematically discussed. We hope to provide new design ideas or solutions to advance the commercialization of sodium ion batteries.

In order to achieve global carbon neutrality in the middle of the 21st century, efficient utilization of fossil fuels is highly desired in diverse energy utilization sectors such as industry, transportation, building as well as life science. In the energy utilization infrastructure, about 75% of the fossil fuel consumption is used to provide and maintain heat, leading to more than 60% waste heat of the input energy discharging to the environment. Types of low-grade waste heat recovery technologies are developed to increase the energy efficiency. However, due to the spatial and temporal mismatch between the need and supply of the thermal energy, much of the waste thermal energy is difficult to be recovered. Thermal energy storage (TES) technologies in the forms of sensible, latent and thermochemical heat storage are developed for relieving the mismatched energy supply and demand. Diverse TES systems are developed in recent years with the superior features of large density, long-term, durable and low-cost. These technologies are vital in efficient utilization of low-grade waste heat and expected for building a low or zero carbon emission society. This paper reviews the thermal storage technologies for low carbon power generation, low carbon transportation, low carbon building as well as low carbon life science, in addition, carbon capture, utilization, and storage are also considered for carbon emission reduction. The conclusion and perspective are raised after discussing the specific technologies. This study is expected to provide a reference for the TES technologies in achieving zero-carbon future.

Low-grade heat recovery has received increasing attention as an essential contributor to improving overall energy utilization efficiency and facilitating the carbon neutrality commitment. Here, we developed a techno-economic analysis model of converting low-grade heat into electricity and hydrogen via the osmotic heat engine (OHE) and power-to-gas facility to alleviate the dilemma of lacking practical application scenarios of waste heat. The contribution margin is optimized in real time by either sending the electricity generated by the OHE into the electrolyzer for hydrogen production or selling it at market price in Wuhan, China, thus to identify the economically viable OHE costs under different conditions. Results show that the allowed heat engine cost is significantly impacted by the capacity factor, lifetime and discount rate. The effect of the capacity size of power-to-gas facility on allowed heat engine cost strongly depends on the hydrogen price. The allowed OHE cost increases with the elevating waste heat temperature for each heat transfer scenario. The hybrid energy system can be economically competitive compared with current mature technologies when the waste heat temperature is higher than 68 ℃ and 105 ℃ for fluid and air as heat transfer fluid, respectively. The economically viable heat engine cost is expected to gradually decline from 50,043 ¥/kW to 18,741 ¥/kW within next 15 years. Incentive policy would boost the economic viability of converting low-grade heat into electricity and hydrogen.

Thanks to the high power/energy densities together with lower cost, potassium ion hybrid capacitors (PIHCs) have broad application prospects. Nevertheless, the significant volume changes during K⁺ intercalation/deintercalation together with the misfit between anode as well as cathode limit their further development. Herein, hierarchically porous nitrogen-doped carbon (N-HPC) is fabricated and used as two electrodes materials for PIHCs. The three-dimensional hierarchical porous structure and large interlayer distance of N-HPC afford enough space to alleviate the volume expansion of potassium. Furthermore, the suitable N doping enables additional active sites towards K⁺ storage and improves electrical conductivity of electrodes. Hence, the constructed PIHCs assembled with dual N-HPC electrodes deliver a high energy density of 103.5 Wh kg^‒1 at 1000.0 W kg^‒1. Meanwhile, the PIHCs devices also display superior cycling stability, achieving a capacity retention rate of 70.2% after 10,000 cycles at 1.0 A g^‒1.

The goals of national energy security and sustainable development necessitate the role of renewable energy, of which biomass energy is an essential choice for realizing the strategic energy diversification and building a low-carbon energy system. Microbial conversion of flue-gas-derived CO₂ for producing biodiesel and biogas has been considered a significant technology in new energy development. Microalgae carbon sequestration is a hot research direction for researchers. However, three fundamental problems relating to energy/mass transfer and conversion remain as follows: (1) contradictory relationship between high resistance of cell membrane micropores and high flux of flue-gas-derived CO₂ limits mass transfer rate of CO₂ molecules across cell membrane; (2) low biocatalytic activity of intracellular enzymes with high-concentration CO₂ results in difficulties in directional carbon/hydrogen conversion; (3) competition between multiple intracellular reaction pathways and high energy barriers of target products hinder the desirable cascade energy transfer. Therefore, key scientific issues of microbial energy conversion lie in the understanding on directional carbon/hydrogen conversion and desirable cascade energy transfer. Multiple researches have established a theoretical foundation of microbial energy conversion which strengthens energy/mass transfer in microbial cells. The innovative results in previous studies have been obtained as follows: (1) Reveal mass transfer mechanism of vortex flow across cell membrane micropores. (2) Propose a strategy that directionally regulates enzyme activity. (3) Establish chain reaction pathways coupled with step changes.

China’s national Emissions Trading Scheme (ETS), the largest ETS in terms of the amount of CO₂ regulated, was launched on the trading platform operated by the Shanghai Environment and Energy Exchange (SEEE) on July 16th 2021, and has successfully completed its first compliance cycle on December 30th, 2021. During the operation of its first cycle, China’s national ETS differs from other international ETSs in many aspects, including trading products and participants, allowance allocation method, compliance term, and offset mechanism, leading to certain unique trading patterns. Some unique settings are worth noticing including key emitters dominated by state-owned enterprises (SOEs) who also dominate transactions, large-scale power groups’ carbon strategies, allowances for 2 years of 2019 and 2020 being processed in one compliance period and allowed inter-year banking of allowances. All these have led to trading patterns characterized by cyclical demand-driven trading, insufficient trading capabilities of regulated entities, stable allowance price and an increased price of CCER. Nonetheless, the successful running of its first compliance cycle offers invaluable experience for future ETS development in operational mechanism improvement, sector coverage expansion, allocation optimization, and introduction of different types of market players and tradable products, and provides a good reference for future international expansion.

Hydrogen, as a clean energy carrier, is of great potential to be an alternative fuel in the future. Proton exchange membrane (PEM) water electrolysis is hailed as the most desired technology for high purity hydrogen production and self-consistent with volatility of renewable energies, has ignited much attention in the past decades based on the high current density, greater energy efficiency, small mass-volume characteristic, easy handling and maintenance. To date, substantial efforts have been devoted to the development of advanced electrocatalysts to improve electrolytic efficiency and reduce the cost of PEM electrolyser. In this review, we firstly compare the alkaline water electrolysis (AWE), solid oxide electrolysis (SOE), and PEM water electrolysis and highlight the advantages of PEM water electrolysis. Furthermore, we summarize the recent progress in PEM water electrolysis including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts in the acidic electrolyte. We also introduce other PEM cell components (including membrane electrode assembly, current collector, and bipolar plate). Finally, the current challenges and an outlook for the future development of PEM water electrolysis technology for application in future hydrogen production are provided.

Distributed energy system, a decentralized low-carbon energy system arranged at the customer side, is characterized by multi-energy complementarity, multi-energy flow synergy, multi-process coupling, and multi-temporal scales (n-M characteristics). This review provides a systematic and comprehensive summary and presents the current research on distributed energy systems in three dimensions: system planning and evaluation, modeling and optimization, and operation and control. Under the regional environmental, resource, and policy constraints, planning distributed energy systems should fully integrate technical, economic, environmental, and social factors and consider device characteristics, system architecture, and source-load uncertainties. Further, this review presents four modeling perspectives for optimizing and analyzing distributed energy systems, including energy hub, thermodynamics, heat current, and data-driven. The system’s optimal operation and scheduling strategies, disturbance analysis, and related control methods are also discussed from the power system and thermal system, respectively. In all, more research is required for distributed energy systems based on an integrated energy perspective in optimal system structure, hybrid modeling approaches, data-driven system state estimation, cross-system disturbance spread, and multi-subject interaction control.

In order to mitigate global warming, the international communities actively explore low-carbon and green development methods. According to the Paris Agreement that came into effect in 2016, there will be a global stocktaking plan to carry out every 5 years from 2023 onwards. In September 2020, China proposed a "double carbon" target of carbon peaking before 2030 and carbon neutrality before 2060. Achieving carbon peaking and carbon neutrality goals requires accurate carbon emissions and carbon absorptions. China's existing carbon monitoring methods have insufficient detection accuracy, low spatial resolution, and narrow swath, which are difficult to meet the monitoring requirement of carbon sources and sinks monitoring. In order to meet the needs of carbon stocktaking and support the monitoring and supervision of carbon sources and sinks, it is recommended to make full use of the foundation of the existing satellites, improve the detection technical specifications of carbon sources and sinks monitoring measures, and build a multi-means and comprehensive, LEO-GEO orbit carbon monitoring satellite system to achieve higher precision, higher resolution and multi-dimensional carbon monitoring. On this basis, it is recommended to strengthen international cooperation, improve data sharing policy, actively participate in the development of carbon retrieval algorithm and the setting of international carbon monitoring standards, establish an independent and controllable global carbon monitoring and evaluation system, and contribute China's strength to the global realization of carbon peaking and carbon neutrality.

CO₂ capture is a process with a high energy consumption, and its large-scale implementation should be based on comprehensive analysis of its impact on the energy, economy, and environment. The process of injecting CO₂ into existing oil fields is a well-known enhanced oil recovery (CO₂-EOR) technique. Using CO₂ as a working fluid to recover oil can compensate for the energy consumption of the capture and transport processes, increasing the feasibility of CO₂ capture while achieving carbon sequestration. In this study, a full-chain CO₂ capture, utilization, and storage (CCUS) system based on the post-combustion capture method is deconstructed and coupled. A full-chain energy consumption calculation software is developed, and optimization analysis of the energy consumption system is conducted. The energy budget of the oil displacement utilization is deconstructed, and the advantages of the water alternating gas (WAG) method are clarified from an energy budget point of view. The analysis reveals that the benefits of CO₂-EOR are far greater than the energy consumption of other CCUS processes, and CCUS-EOR is a CO₂ utilization method with positive energy benefits. Based on the simulation of the effects of N₂ and CH₄ on the recovery factor, a multi-well combined injection-production method is proposed, and the reasons for increasing profit are analyzed.

This study revisits the question of “whether firms are doing well by doing good?”. We examine shareholders-sponsored corporate socially responsible (CSR) proposals related to Environmental, Social, and Governance (ESG) that are voted to pass or fail by a small margin. The adoption of those “close call” proposals is regarded as equivalent to a random assignment of CSR policies and, therefore, provides a quasi-experimental setting to capture the causal influence of CSR on firm performance. We apply the regression discontinuity design (RDD) and find that CSR proposals’ passage leads to a significant positive abnormal return on the voting day. The results are robust with both parametric and nonparametric approaches of RDD and different polynomial orders. However, we fail to identify a significant change in financial performance in the long-term. One possible reason is that passing a CSR proposal could be symbolic, rather than substantial.

The Paris Agreement, a landmark in the multilateral process of global climate governance, not only demonstrates the greatest inclusiveness and feasibility based on science and principles, but also points out the general direction of the global green and low-carbon transition. The Agreement has set a global goal to hold the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels, and to pursue efforts to limit the temperature increase to 1.5 degrees Celsius by the end of the century. To achieve this long-term objective, developed countries should take the lead in reducing emissions as soon as possible, which is fundamental to the achievement of net-zero global emissions at an early date. China’s goal of striving to peak carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060 shows its great ambition, strength, and responsibility as a major country, indicating that China is committed to realizing carbon neutrality from carbon peaking in the shortest time in global history, and will make greater efforts and contributions to achieve the goals set out in the Paris Agreement.

Cost-effective CO₂ capture is essential for decarbonized cement production since it is one of the largest CO₂ emission sources, where 60% of direct emissions are from CaCO₃ decomposition and 40% are from fuel combustion. This work presents a low-carbon cement manufacturing process by integrating it with renewable energy for electric heating and thermal storage to replace the burning of fossil fuels in the conventional calciner. The low-carbon renewable energy reduces the indirect CO₂ emissions from electricity consumption. The high-temperature CO₂ is employed as the heat transfer fluid between the energy storage system and the calciner. In the proposed basic manufacturing process, the CO₂ from the CaCO₃ decomposition can be directly collected without energy-consuming separation since no impurities are introduced. Furthermore, the remaining CO₂ from fuel combustion in the kiln can be captured through monoethanolamine (MEA) absorption using waste heat. In the two situations, the overall CO₂ emissions can be reduced by 69.7% and 83.1%, respectively, including the indirect emissions of electricity consumption. The economic performance of different energy storage materials is investigated for materials selection. The proposed manufacturing process with a few high-temperature energy storage materials (BaCO₃/BaO, SrCO₃/SrO, Si, etc.) offers a higher CO₂ emission reduction and lower cost than alternative carbon capture routes, i.e., oxyfuel. The cost of CO₂ avoided as low as 39.27 $/t can be achieved by thermochemical energy storage with BaCO₃/BaO at 1300 °C, which is superior to all alternative technologies evaluated in recent studies.

A new technical route of organic matter capture and carbon fixation is proposed in response of the increasingly strict emission standards of volatile organic compounds (VOCs) in petrochemical industry and the Chinese national strategic development goals of carbon peak and carbon neutralization. A closed loop from raw materials to adsorbents for gas treatment can be achieved by two key technical characteristics: (1) construct a new mesoporous adsorbent with complete desorption and regeneration function by carbon nanotubes (CNTs); (2) convert gaseous organic matter which cannot be recycled in liquid/gas state to CNTs. It realizes the resource integration of "turning waste into treasure" and maximizes the carbon emission reduction effect of waste gas treatment process without consuming extra precious fossil fuel, compared with the traditional technologies of VOCs treatments, including combustion or catalytic oxidation. What’s more, the increase in supply of various green electricity is expected to change the current situation of large investment and heavy cost burden of environmental protection technology, and make a great contribution to the national carbon peak and carbon neutrality policy.

From a macro-energy system perspective, an energy storage is valuable if it contributes to meeting system objectives, including increasing economic value, reliability and sustainability. In most energy systems models, reliability and sustainability are forced by constraints, and if energy demand is exogenous, this leaves cost as the main metric for economic value. Traditional ways to improve storage technologies are to reduce their costs; however, the cheapest energy storage is not always the most valuable in energy systems. Modern techno-economical evaluation methods try to address the cost and value situation but do not judge the competitiveness of multiple technologies simultaneously. This paper introduces the ‘market potential method’ as a new complementary valuation method guiding innovation of multiple energy storage. The market potential method derives the value of technologies by examining common deployment signals from energy system model outputs in a structured way. We apply and compare this method to cost evaluation approaches in a renewables-based European power system model, covering diverse energy storage technologies. We find that characteristics of high-cost hydrogen storage can be more valuable than low-cost hydrogen storage. Additionally, we show that modifying the freedom of storage sizing and component interactions can make the energy system 10% cheaper and impact the value of technologies. The results suggest looking beyond the pure cost reduction paradigm and focus on developing technologies with suitable value approaches that can lead to cheaper electricity systems in future.

Due to the large amount of greenhouse gas (GHG) emissions and the high dependence on fossil energy, the aviation industry has attracted a lot of attention for emission reduction and sustainable development. Biomass is a green and sustainable renewable resource, and its chemical conversion to produce bio-jet fuel is considered to be an effective way to replace fossil jet fuel and achieve emission reduction. In this study, the cradle-to-grave life cycle analysis is conducted for three bio-jet fuel conversion pathways, including biomass aqueous phase reforming (APR), hydrogenated esters and fatty acids (HEFA), and hydrothermal liquefaction (HTL). Compared with fossil jet fuels, the three bio-jet fuels have a great advantage on global warming potential (GWP), contributing 29.2, 43.6 and 51.2 g CO₂-eq/MJ respectively. In general, as a relatively new bio-jet fuel conversion technology, the technology of aqueous phase reforming has minimal environmental impact. If the barriers of raw material availability and economy could be broken down, bio-jet fuel will have great development potential in replacing fossil jet fuel and realizing sustainable development.

Ammonia has been considered as a novel fuel for decarbonization purposes. However, emissions from combustion systems are still posing a problem. Therefore, experimental and numerical simulations have been conducted to study the concentration of exhaust emissions (Nitric oxide “NO”, Nitrous oxide “N₂O”) from burning the ammonia/hydrogen (NH₃/H₂) blend 85/15 (vol%). The effects were measured at various thermal powers ranging 10 to 20 kW and with different Reynolds numbers from 20,000—40,000. The experimental points were numerically investigated in the Ansys CHEMKIN-Pro environment employing seven chemical kinetic mechanisms taken from the literature. All experiments have been undertaken at standard atmospheric conditions. The experimental results showed that both NO and N₂O gradually increased when the Reynolds number increased from 20,000 to 40,000. Along with that, the concentration of NO emissions at the exhaust reported minimum level when the Re = 20,000 due to lower reactivity radical formation, all that led to a deterioration of the flame characteristics. Also, the integrated radical intensities of NO*, OH*, NH*, and NH₂* demonstrate an increasing trend as Re increased from 20,000 to 40,000. In terms of thermal power, N₂O suffered an abrupt decrease when the thermal power increased up to 15 kW, while the opposite occurs for NO. In addition, the radicals intensity of OH*, NH*and NH₂* figures show an increase in their concentration when the thermal power increased up to 15 kW then decreased with increasing thermal intensity to reach 20 kW, reflecting into increased NO productions and decreased N₂O levels. The numerical analysis showed that Stagni, Bertolino, and Bowen Mei were the most accurate mechanisms as these give a good prediction for NO and N₂O. The study also showed that the chemical reaction (HNO + O₂ ↔ NO + HO₂) is the main source of NO formation. While the chemical reaction (NH + NO ↔ N₂O + H) is responsible for the formation of N₂O by consuming NO and when there will be abundance in NH radicals. Finally, dealing with a blended fuel of high ammonia concentration encourages ammonia chemistry to become more dominant in the flame. It decreases the flame temperature, hence lowering heat loss between the flame and the surrounding.