1 Introduction
The Chinese Academy of Engineering (CAE) has published the annual reports of
Engineering Fronts 2024 [
1–
3]. A multi round interaction method, involving iterative selection and judgment between experts and data, was adopted. Through the deep integration of expert review and data analysis, a total of 92 engineering research fronts and 92 engineering development fronts were selected. Among them, 3 engineering research fronts and 3 engineering development fronts were identified in the field of
Energy and Electrical Science and Technology. Notably, the interpretation of 1 engineering research front and 1 engineering development front served as an important guide for the future development of
Energy and Electrical Science and Technology, highlighting new trends and characteristics of global engineering innovation in this discipline.
Engineering Fronts 2024 also provided valuable insights for topic selection in the energy sub-journal
Frontiers in Energy of the flagship journal,
Engineering, of CAE.
2 Method and procedures for engineering research fronts
With support from the Energy and Mining Engineering Division Office in CAE, the selection of engineering research fronts was conducted in three stages: data preparation, data analysis, and expert review.
In the data preparation stage, domain, library, and information experts in this field identified 101 journals and 757 conferences as retrieval data sources for the research fronts.
In the data analysis stage, the Web of Science methodology was applied to select the top 10% of highly cited papers published between 2018 and 2023, considering factors such as journal versus conference papers and publication years. These papers formed the core dataset for research front analysis. Co-citation analysis was then used to cluster the highly influential papers and identify key themes in the literature. To address gaps caused by limitations in data mining algorithms, experts nominated additional fronts to complement the quantitative analysis.
In the expert review stage, domain experts assessed, discussed, and reviewed the engineering research fronts based on their expertise and comprehensive scientific and technological intelligence, including technological trends, policies, and news reports, and integrated them into each stage determined by the forefront. After extensive questionnaire surveys and multiple rounds of expert discussions, 3 engineering research fronts were ultimately selected in the fields of Energy and Electrical Science and Technology, as detailed below.
2.1 Research on integrated CO2 capture and in situ utilization
Integrated carbon dioxide (CO2) capture and in situ utilization refers to the technology by which adsorbed CO2 is converted into high-value products without undergoing traditional temperature and pressure swing desorption processes. The core of this technology lies in complete CO2 capture and conversion within the same material system, eliminating the need for separate processes such as CO2 separation, purification, storage, and transportation. In theory, this approach can significantly reduce costs and energy consumption while simplifying the overall system. The CO2 capture process can involve solid adsorption or solution absorption, which is then coupled with catalytic conversion. The mainstream technical route uses adsorption-catalytic dual-functional materials, which consist of alkali/alkaline earth metal oxide adsorbents and precious metal or transition metal catalysts. The adsorbed CO2 is converted in situ through reaction processes such as methanation, reverse water gas gasification, and methane dry reforming.
The main research directions and development trends for integrated CO2 capture and in situ utilization include: ① the development of high-performance, low-cost, and long-life dual-functional materials, along with understanding the coupling reaction mechanism of CO2 adsorption and in situ catalytic conversion; ② process parameter optimization and the integration of renewable energy technologies; ③ large-scale demonstration applications and the technical and economic analysis in real-world scenarios.
2.2 Discovery of high ionic conductivity solid electrolytes
Compared to organic liquid electrolytes, solid-state electrolytes have a wider electrochemical window and enhanced safety, making them a promising direction for the development of future power and energy storage batteries. One of the main challenges facing all-solid-state batteries is their limited charging and discharging rates. The strong ion interactions in bulk solid electrolytes and the high impedance at the electrolyte-electrode interfaces create migration energy barriers that are up to 10 times higher than those in liquid electrolytes, retarding the charging and discharging processes. High Li-ion conductivity solid electrolytes are generally composed of inorganic ionic compounds.
Thanks to their stable ion transport channels and good mechanical adaptability at interfaces, sulfur-based solid electrolytes exhibit a lithium-ion conductivity greater than 10 mS/cm at room temperature, which is comparable to that of commercial liquid electrolytes. By designing the electrolyte composition and studying interfacial stability, the reaction and diffusion energy barriers can be reduced, further improving lithium-ion conductivity of solid electrolytes.
The development directions for electrolyte composition design include optimizing chemical composition and crystalline structure to increase ion conduction channels and minimize ion-ion interactions, thereby facilitating the free diffusion of lithium ions. Research on interfacial stability primarily focuses on developing interface passivation layers, coating layers, and reducing interfacial stress.
It is worth noting that the physicochemical processes, such as ion transport and interface electrochemistry between solid electrolyte phases and electrodes, exhibit distinct coupling effect involving chemical, electric, and force fields. By comprehensively considering these multi-field couplings, experimental studies and theoretical models of solid-state electrolytes under real working conditions can effectively reveal the failure and runaway mechanisms in practical applications, which is an important direction for the future development of high-ionic conduction solid-state electrolytes.
2.3 Study on large model of power system operation and maintenance
The power system is one of the largest and most complex man-made systems in the world. In the context of developing a new type of power system, the integration of a large number of distributed energy resources and flexible loads has resulted in high dimensionality, nonlinearity, and dynamicity in system operation and maintenance. Traditional static modeling and centralized optimization methods can hardly satisfy the requirements in terms of calculation efficiency and accuracy.
State-of-the-art AI techniques, particularly large-scale models, show promise in addressing these challenges. Large-scale models typically refer to neural networks with extremely large parameter scales capable of learning complex patterns from diversified datasets. For instance, these models can extract patterns from power system time series measurements, images, and topologies to support system operation and maintenance. More specifically, large-scale models include large language models (LLMs) like ChatGPT, which can integrate and generate multi-domain knowledge through user interactions, offering an effective way for power system operation and maintenance.
However, several issues remain in the research on large-scale power system AI models: ① Fine-tuning of large-scale models with limited data. Unlike vast amount of textual data available on the Internet, power system operational data, especially data from extreme operating conditions, are relatively scarce. This limits the ability to train large-scale AI models from scratch. It is important to study methods for efficiently training these models with limited data samples. ② Robustness and interpretability of large-scale AI models. Large-scale models, by design, learn statistical rules based on deep neural network with hyperscale parameters, the process of which is difficult to interpret and may result in inaccurate results, which contradicts to the reliability requirements for power system operation. ③ Data security. Power system operational data is highly sensitive and secured, and training AI models using this data raises concerns about data security and privacy.
3 Method and procedures for engineering development fronts
The selection of engineering development fronts was also conducted in three stages: data preparation, data mining, and expert review.
In the data preparation and mining stage, the Derwent Innovation patent database was used as a basis for constructing the preliminary patent data search scope and search strategy. This was achieved by utilizing the manual code of Derwent World Patent Index (DWPI), the International Patent Classification (IPC), and the U.S. Patent Classification (USPC) System, along with specific technical keywords. Experts in the field, along with specialists from Library and Information Science, refined and improved the patent search formulas, resulting in the identification of 117 unique search formulas.
In the data analysis stage, experts performed searches using the DWPI and Derwent Patent Citation Index (DPCI) platforms for patents published between 2018 and 2023. The vast number of patent documents retrieved were then filtered according to two indicators: “average annual citation frequency” and “technology coverage width”. The top 10000 patent families in the field were comprehensively evaluated. Additionally, semantic similarity analysis of the patent text was conducted, followed by theme clustering based on the DWPI title and abstract fields. This process resulted in the creation of a ThemeScape patent map, providing a clear and intuitive overview of developing technologies in the field of Energy and Electrical Engineering.
In the expert review stage, domain experts analyzed the results based on their professional expertise supplemented by other sources of comprehensive intelligence, such as industry dynamics, science and technology policies, and news reports. Their input was used to propose potential development fronts, integrating these into each phase of the front determination process.
Finally, domain experts merged, revised, and refined the interpretations of the patent map, incorporating the expert nominated fronts to identify 8 alternative engineering development fronts. After conducting extensive questionnaire surveys and multiple rounds of expert meetings, 3 engineering developments fronts in the fields of Energy and Electrical Science and Technology were ultimately selected and interpreted below.
3.1 High energy density, long life, and low-cost solid-state battery technology
Solid-state batteries utilize solid-state electrolytes instead of the liquid electrolytes and separators found in traditional batteries. This shift offers larger energy density, longer cycle life, and improved safety. Enhancing the energy density of solid-state batteries increases the endurance mileage of electric vehicles, supporting the development of electric heavy-duty trucks and electric aircraft. Specifically, solid-state batteries with an energy density of 400 Wh/kg and a stable cycle life of 2000 cycles could increase the endurance mileage of electric vehicles to 1000 km, which is crucial for the widespread adoption of pure electric vehicles. In addition, such batteries could power a two-seater light aircraft for thousands of flights, making them keys to the emerging low-altitude economy. Solid-state batteries can significantly reduce the weight of aircrafts and increase their thrust-to-weight ratio, revolutionizing modern transportation through electrification.
However, the energy density and cycle life of solid-state batteries are impacted by challenges such as interface instability, lithium dendrite growth, and electrolyte degradation. Moreover, the synthesis of solid-state electrolytes is complex and yields are low. Currently, solid-state electrolytes cost around 190 $/kg, which is far above the commercialization threshold of 50 $/kg. To address these issues, further improvements can be made by modifying through intrinsic material modification and manufacturing process optimization, the energy density and the cycle life of solid-state batteries can be further improved, and the synthesis cost can be reduced. The modification of intrinsic materials mainly develops from the directions of positive and negative electrode material modification, electrolyte structure design, and in situ solid electrolyte passivation layer formation. The main development directions for electrolyte development and manufacturing process optimization include the film deposition process, mass production techniques, and ultrafast and precise synthesis technologies. Among these, ultrafast and precision synthesis technology stands out as a crucial future trend. This technology enables the rapid and accurate synthesis of multi-component and even high-entropy solid-state electrolytes in just seconds, which can not only efficiently screen and explore electrolyte materials with specific target components, but also realize the accurate and uniform synthesis of multiple elements in single pure phase materials. This is an important trend in the future development and industrial-scale synthesis of solid-state battery materials.
3.2 Research and development of devices and systems of heat storage and hydrogen storage
Thermochemical energy storage is a technology that stores and releases heat through reversible gas-solid chemical reactions. One such reversible chemical reaction involves the alloy and hydrogen, which is also a form of solid-state hydrogen storage. Magnesium-based metal/titanium-based metal alloys react with hydrogen to form metal hydrides for hydrogen storage and the release of heat in the process. These hydrides can later be heated, undergoing decomposition reactions to release hydrogen gas. Therefore, this technology integrates both thermochemical heat storage and solid-state hydrogen storage.
Current research often treats thermochemical heat storage and solid-state hydrogen storage as separate technologies. However, the processes of storing and releasing hydrogen are inherently linked to the processes of storing and releasing heat and heat transfer, which affect each other. Moreover, the amount of heat released during the chemical reaction has a significant impact on the energy storage efficiency of solid-state hydrogen storage. In the future, integrating the storage and release of both hydrogen and heat could improve overall energy utilization efficiency.
A key challenge in advancing this technology lies in the design optimization of devices and systems. This optimization requires comprehensive consideration of factors such as high heat transfer performance, high system utilization efficiency, and reaction cycle stability for system integration. Achieving this goal will require cross-disciplinary collaboration, drawing on expertise from multiple disciplines such as chemistry, heat transfer, thermodynamics, and mechanical design. These integrated technologies hold the potential to deliver significant breakthroughs in hydrogen and heat storage.
3.3 Development of high-power wide-range bidirectional charging technology and equipment
High-power wide-range bidirectional charging technology refers to the bidirectional direct current (DC)/alternating current (AC) conversion between electric vehicles (EVs) and the power grid, which relies on the application of high-power bidirectional charging piles. These piles typically have AC input and output voltages of the power grid of either single-phase 220 V or three-phase 380 V, while the DC input and output voltages of EVs range from 200 to 1000 V, with a bidirectional power of up to 240 kW. This technology improves the utilization efficiency of energy and enhances the flexibility and economy of EVs, fostering greater interaction between EVs and the power grid.
The main research topics in this field include: bidirectional AC/DC and DC/DC conversion technology; extending the power and voltage range of bidirectional charging; voltage resistance, insulation, and heat dissipation; integrated management systems for bidirectional charging; bidirectional charging metering; communication protocols among EVs, bidirectional charging piles, and the power grid; and the optimization of bidirectional charging strategies.
Future research prospects include developing high-efficiency high-power bidirectional AC/DC converters; enhancing heat dissipation, reliability, and service life of charging piles through liquid cooling technology, which would also downsize the charging guns; and constructing the bidirectional charging energy management platform to enable information exchange and coordinated regulation among EVs, charging piles, and the power grid.
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