4
Energy Sciences

INTRODUCTION

The energy sciences competency focuses on mechanical and electrical power generation, storage, conditioning, and distribution; energy conversion; and emerging concepts for lasers, directed energy (DE), and DE protection and propagation. The competency has four core competencies: battery science, directed energy, expeditionary power, and power integration. The battery science core competency focuses on research related to electrochemical energy storage technologies; design, development, characterization, and analysis of battery materials and interfaces; and hybrid power systems technology. The directed energy core competency focuses on research related to materials, optics understanding, and atmospheric transmission effects for the delivery of and protection from highly focused energy. The expeditionary power core competency focuses on research related to emerging and disruptive technologies in energy materials, compact power subsystems, alternative energy sources, energy scavenging, and long-lived power ideas. The power integration and architecture core competency focuses on research related to power control, generation, distribution, conditioning, conversion, and thermal management.¹ The Panel on Assessment of Energy Sciences received presentations and posters focus on the work of the energy sciences competency and its four core competencies on September 12–14, 2023. Below is a summary of the review’s findings.

TECHNICAL QUALITY OF THE CORE-COMPETENCY RESEARCH

Battery Sciences Core Competency

Accomplishments and Advancements

The battery sciences core competency focuses on battery and electrochemical storage technologies that have the potential of being deployed under extreme operational conditions (e.g., low temperature). The projects that were presented during the September 2023 assessment tended to focus on new electrode and electrolyte materials with some attention paid to devices and systems. The projects follow what is generally being pursued at other national laboratories and universities.

In comparing the scientific quality of the research within the battery science core competency with that at other leading research institutions, it is important to define the character of the work. Much of the work within this core competency can be best characterized as engineering innovation versus scientific research. Engineering innovation involves designing a material, a device, or software to solve a problem or exploit an opportunity, synthesizing/building/coding that envisioned solution, and testing its performance against some set of target metrics. Scientific research involves the formulation, testing, and

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¹ Core competency descriptions in this passage come from U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory (ARL), 2022, “Foundational Research Competencies and Core Competencies,” March.

modification of hypotheses (the scientific method). Work at universities, even in colleges of engineering, is more aligned with the scientific method, while work at ARL is more aligned with engineering innovation. With that, the quality is generally high. In particular, the projects are well formulated with solid technical approaches. In addition, the staff members are accomplished and well suited for the projects. Furthermore, the posters presented during the review were informative and the presenters were excellent. The presenters also provided enlightened responses to scientific questions suggesting a deep understanding of the area.

Research Portfolio Opportunities

Overall, the methods and tools employed in this core competency are sound for the selected projects although the modelling efforts would benefit from additional use of machine learning methodologies. In addition, some of the experimental characterization efforts continue to depend on ex situ versus in situ or in operando operation. Understanding function under conditions that simulate those during deployment more directly address the competency goals. Additionally, it was not apparent how extreme conditions were being considered other than perhaps safety (e.g., use of water as solvent versus organics). Future presentations may consider being more explicit in defining how the work addresses competency goals.

The extramural presentation “Electrochemistry—Batteries and Fuel Cells,” highlighted the multidisciplinary collaborations across the Army Research Laboratory (ARL), academia, government, and industry that focused on understanding and controlling electrochemical redox reactions and transport of species that are coupled with electrode, catalysis, electrolyte, and interface to provide the foundation for exponential advances in sensors, batteries, fuel cells, and technology not yet foreseen for the soldier.² ARL provided examples of extramural research projects, which included work to:

• Understand fundamental ionic storage mechanisms in atomic layers of transition metal oxides for next-generation aqueous Zn-ion batteries. This work seems to use an Edisonian approach (i.e., trial and error). There is an opportunity to better define principles and incorporate machine learning (ML).
• Tune molecular rigidity to create “pour” ionic liquid electrolytes for multivalent batteries. This is promising work in particular with regard to the low lithium-triflouromethanesulfonyl coordination in diamondoid-derived ionic liquids as compared to what is seen in traditional ionic liquids. A few questions emerged, which include: Is there a way to accelerate candidate selection? What other substituents have been employed? Is there a way to accelerate candidate screening?
• Understand unusual conductivity behavior in the double perovskite (Sr1.9VMoO6−δ [SVMO]) materials. A question emerged as to how will these materials work with high O2 (and sulfur).
• Understand the implications for applications in high temperature energy conversion. The research could be strengthened with a greater focus on the fundamental electrolyte/battery issues that limit performance under extreme conditions, which primarily means temperature, but may include vibration, shock or other environmental issues.

Overall, the ARL extramural researchers may consider increasing the focus of the research on determining how one could break coupling between energy density, power density, and cyclability, and seek additional partnerships with researchers that could accelerate progress. Additionally, one final

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² U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory (ARL), “Electrochemistry—Batteries and Fuel Cells,” document for the Army Research Laboratory Technical Assessment Board, received September 12, 2023.

suggestion is that the core competency may consider focusing more on fundamental issues, including ionic storage mechanisms and the chemistry and structure of the electrolyte/electrode interface, since key performance characteristics (e.g., safety, stability, and lifetime) will be influenced by the composition and structure at the electrolyte/electrode interface.

Energy Conversion Core Competency

Accomplishments and Advancements

The energy and power requirements for sustained platform operations continue to increase as more power-consuming sensors, communications, and intelligent weapon systems are deployed in a multi-domain operational environment. To address these needs, the energy conversion core competency focuses on new approaches to convert energy and increase system energy efficiency in order to enable future forces to operate with limited opportunity for resupply. The research portfolio consists of a wide range of projects with programs in energy materials, compact power subsystems, alternative energy sources, energy scavenging, and long-lived power ideas.³ The energy conversion core competency consists of a well-balanced portfolio of projects that include both foundational and fundamental work, as well as projects involved in operational science research.

The research projects address important scientific questions in energy conversion and overall, the execution is done at a very high level and in a timely manner. Highly qualified staff with diverse backgrounds and expertise complement each other in their respective research teams and expertly execute the various challenges in their energy conversion projects. Very impressive progress and results were demonstrated in many of the projects, and as a result, several of the researchers are considered leaders in their respective field of research.

For example, in just a few years since ferroelectric nitrides were reported in 2019, a team at ARL, leading the effort of film growth and characterization, demonstrated high-temperature switching results that are unmatched by any other group in the world. Other examples of research that is highly regarded by the international community are the research programs in plasmonic chemical energy conversion and nuclear excitation by electron capture. Both programs presented novel results and analyses that led to findings that are controversial and have the potential to change the landscape of future research in their respective areas.

Research Portfolio Opportunities

The research being done within the energy conversion core competency demonstrates ARL’s very strong experimental capability. Although much of this research does include modeling and computational aspects, the modeling is sometimes simplistic. In some projects, research could be strengthened by increased efforts in modeling and computation to help guide and interpret experimental work. An increase in modeling and computational research may require additional staff expertise in modeling and computation as it aligns to the needs of the energy conversion projects or further collaborations with outside researchers.

Directed Energy Core Competency Research

Accomplishments and Advancements

The directed energy core competency is engaged in research related to the delivery of and protection from highly focused energy. The research portfolio, as described during the presentations, includes programs to develop new laser materials and laser concepts to counter advanced threats that are unique to military systems and not supported by commercial research and development, although there is

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³ U.S. Army Combat Capabilities Development Command (DEVCOM) Army Research Laboratory (ARL), 2022, “Foundational Research Competencies and Core Competencies,” March.

justifiably a heavy reliance on industry collaborations for development of laser materials. The main thrust of the directed energy core competency is on the development of high-power fiber lasers based on notionally accepted principles applied to novel materials and fiber designs. Described activities are a mix of 6.1 and 6.2 research and development efforts were a mix of in-house research with extensive industry and academic collaborations and extramural research. The overall technical quality of directed energy core competency is generally good, with significant variations across different activities, including some that are judged to be very high quality.

The assessment criteria ask for commentary on the use of research methods and methodologies. The directed energy research at ARL, as presented, reflects a collection of efforts, most of which are being carried out in depth with a judicious mix of theory, modeling, simulation and experimental verification. The programs rely heavily and effectively on extensive collaborations with academia, national laboratories, and industry to complement the various expertise required for program execution.

Power Integration and Architecture Core Competency

Accomplishments and Advancement

In general, the research observed in the power integration and architecture core competency is competitive with state of the art work being done elsewhere. This common thread of underlying competence, knowledge of state of the art, appropriate methods of investigation, and building on discoveries was well displayed during the review. The research within the power integration and architecture core competency exhibits a solid technical quality and understanding. The ARL researchers are competitive with their peers in academia, industry, and government in their realization and understanding of the technical issues and challenges at a fundamental science level. There is a common high level of competence displayed across these prototype research platforms, presentations, and posters.

The research at ARL has identified great and fundamental directions for investigation. Current research in thermal materials and systems reflects a comparable quality to what is being done elsewhere in government and academia. Appropriate topics are being addressed with the current focus on adaptation or fabrication of conventional materials. Their thermophotovoltaic (TPV) work is consistent with the quality of others in the field. ARL’s focus is on integration, an appropriate facet of work in the field, is of high quality and is competitive.

Furthermore, there is an obvious knowledge of state-of-the-art research among all ARL researchers. The researchers were able to competently answer appropriate questions about current topics, both those at hand and those that involved what is happening in their respective fields. They knew their fields well and could discern among topics and avenues to understand which would be fruitful. They are asking the right questions, based on their knowledge of their respective fields. Their contacts and projects with academia, industry, and government appear to have the right mix of partners and issues to keep them and their investigations current.

The topics that ARL researchers are investigating in power supplies are exactly what are challenging today’s industry leaders. ARL researchers are leveraging discoveries that others publish. They are opening new investigations where discoveries do not seem to be forthcoming as fast as appropriate, and they employ assets wisely. Additionally, the research methods and methodologies that ARL researchers are using are sound. The investigators recognize the need to understand the basic science of each investigation. The investigations are sequenced and prioritized. There is appropriate familiarity with the literature. Searches are done in a proper and timely manner, documenting strengths and weaknesses of the incumbent approaches. Innovative ideas are organized and investigated, sometimes with novel approaches, for example, investigating hybrid vehicles first and then electric vehicles, the reverse of conventional approaches. This proved to be a more productive approach. For other problems, a conventional approach worked well, defining problems, forming hypotheses, taking data, and building theories

Research Portfolio Opportunities

The assessment criteria ask if there are areas in the scientific portfolio where ARL is at major risk of not meeting its objectives. There are no places where the research is at major risk of not meeting its objectives. The assessment criteria also ask for commentary on the overall balance of the core competency’s research portfolio (e.g., core competencies, partnerships, supporting extramural partners) to address the cumulative competency goals. The core competency appears to be balanced nicely. The list of topics presented during the review covered an appropriate realm of relevant research and appears balanced among the fields within energy research. ARL’s partners have a fairly broad base within academia, industry, and government. There is a propensity to work with local, nearby entities. The extramural partners benefit from a great deal of diversity, defined here as a wide range of research partners from academia, industry, and government. These include the large intensive research universities to small state universities and private schools, defense primes to Small Business Innovation Research recipients, and large to small agencies within the government. ARL is making advancement toward improving this mix, expanding its partnership base from what is was perhaps 20 years ago.

The thermal sciences program has a likewise appropriate balance between intramural and extramural components and partners. It is encouraging to see a productive partnership with West Point. That did not exist only a few years ago. That relationship pays off over both short term and long term. For example, cadets are among ARL’s interns and the head of the West Point Department of Electrical Engineering and Computer Science was at ARL for several years; becoming a highly innovative researcher while there.

Gaining partnerships with capable research facilities within other agencies, such as the Department of Energy (DOE), requires much effort. DOE has a lot of relevant research and interested researchers and are good partners who have a similar basic science emphasis. Federal agencies have the unfortunate reputation for favoring a few reliable partners in academia and industry. ARL has done well in expanding this base of expertise through several programs but vigilance will be necessary to expand the realm of partners.

COMPETENCY PORTFOLIO OF SCIENTIFIC EXPERTISE

The ARL intramural and extramural scientists, engineers, and project teams supporting the battery science core competency are strong, and have most of the expertise needed to address the core competency goals. Additionally, it should be noted that there are some projects where the group has not reached critical mass. For example, the modeling and fast physics projects were reported to only support one to two full-time equivalent employees. Given the promise of the work, additional resources might be devoted to these projects.

The scientific expertise in the energy conversion core competency is very strong at both the intramural and extramural level. Programs in energy conversion require a multi-disciplinary research team in order to execute at a high level. In particular, the intramural ARL scientists and engineers have expertise in physics, chemistry, materials science, and electrical, mechanical, and nuclear engineering. Both intramural and extramural scientists and engineers are highly qualified individuals with noted accomplishments in their field of expertise. A number of the staff are respected leaders in their research area.

Overall scientific expertise in the directed energy competency, as seen from the presentations varies from generally good to excellent. The research being performed by ARL staff is mainly concerned with developing laser architectures and optical characterization and ARL staff are contributing to the advancing research technical areas with presentations, publications, and patents. The programs in the directed energy competency rely heavily on externally sourced expertise in laser materials and high-brightness diode pump sources. The majority of, if not all, fiber lasers, both glass and crystalline, as well

as diode pumps are procured from academic institutions, national laboratories, and industry, all of which are regarded as highly respected in their research or product development.

ARL has highly qualified people to support the power integration and architecture core competency. All of the presenters had the background, education, and experience to perform their work well. They publish appropriately and have ongoing work that fits their credentials. Many of ARL’s scientists, in the broader competency and the power integration and architecture core competency are among the best in their fields. There is a good mentorship program in place that is recruiting and mentoring a qualified and talented new generation of scientists.

ARL also attracts input from top scientists in several ways. There are partnerships through various research agreements. Through the extramural collaborations, some of the best universities and scientists are on projects with ARL people. Some visit ARL, but usually the work is done on the extramural researcher’s campus.

ARL researchers are involved in organizing conferences and participate in reviewing papers and research. Generally, this aspect of working with top scientists in the community is done well. Where possible, participation in professional societies such as IEEE, where much of the best research gets presented, is encouraged.

COMPETENCY FACILITIES AND RESOURCES

The equipment, information technology, and digital infrastructure at ARL coupled with that available through extramural collaborations, physical facilities, and digital resources seem appropriate for the battery science core competency projects. Its dry room is superb and has the appropriate capabilities for what is being researched. It is suggested that greater emphasis be placed on carrying out in situ or in operando characterization as opposed to ex situ work. The facilities and resources supporting the energy conversion core competency, in general, appear sufficient for program execution. There also appears to be adequate resources available to support the directed energy core competency. For the power integration and architecture core competency the facilities appear to be appropriate and excellent state-of-the-art work is being done within them. For more capacity and expertise, the Command, Control, Communications, Computers, Cyber, Intelligence, Surveillance and Reconnaissance (C5ISR) Center (formerly known as CERDEC) could be a valuable partner. ARL also has access to great facilities with external partners, and ARL is in an advantageous position of drawing from both internal and external facilities.

OVERALL SCIENTIFIC QUALITY OF THE COMPETENCY

The quality of the science and engineering in the battery sciences core competency is generally high and reflect what is being pursued at other national laboratories and universities. In particular, the projects are well formulated with solid technical approaches. The ARL intramural and extramural scientists, engineers, and project teams supporting the battery science core competency are strong, and have most of the expertise needed the core competency goals. They are accomplished and well suited for the projects. Overall, the methods and tools employed in this core competency are sound for the selected projects although the modelling efforts would benefit from additional use of machine learning methodologies. Additionally, it should be noted that there are some projects where the group has not reached critical mass. For example, the modeling and fast physics projects were reported to only support one to two full-time equivalents (FTEs). Given the promise of the work, additional resources might be devoted to these projects. The equipment, IT, and digital infrastructure at ARL coupled with that available through extramural collaborations, physical facilities, and digital resources seem appropriate for the battery science core competency projects.

The overall technical quality of the directed energy core competency is generally good to excellent, with significant variations in the various activities, and with some being of very high quality. The DE research at ARL, as presented, reflects a collection of efforts, most of which are being carried out in depth with a judicious mix of theory, modeling, simulation, and experimental verification. There appears to be adequate resources available to support the directed energy core competency.

The energy conversion core competency research is at par with top universities and research institutions. The core competency consists of a well-balanced portfolio of projects that include both foundational and fundamental work, as well as projects involved in operational science research. ARL’s research is at the forefront in many of its established research areas, and impressively has demonstrated leadership in expanding new research areas. Project execution is done at a very high level by highly qualified staff with diverse backgrounds and expertise that complement each other in their respective research teams. Both intramural and extramural scientists and engineers are highly qualified individuals with noted accomplishments in their field of expertise. Where expertise is lacking, ARL is using collaborations very effectively to fill in the gap where in-house equipment or expertise is lacking. There are no places where the research is at major risk of not meeting its objectives. The facilities supporting the core competency were also found to be excellent.

Within the energy conversion core competency, ARL is very strong in experimental capability. Although much of this research does include modeling and computational aspects, this modeling is sometimes simplistic. In some projects, research could be strengthened by increased efforts in modeling and computation to help guide and interpret experimental work. An increase in modeling and computational research may require additional staff expertise in these areas as it aligns to the needs of the energy conversion core competency projects or further collaborations with outside researchers.