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United Technologies Research Center

High Performance and Regenerative Redox-Air Flow Cells for Transportation Applications

United Technologies Research Center (UTRC) will develop a proof-of-concept for an innovative new vehicle energy-storage system. The UTRC team is leveraging experience from a previous ARPA-E project focused on grid-scale energy storage, the GRIDS: Breakthrough Flow Battery Cell Stack project, to develop a high-performance redox-air flow cell (RFC) system for EVs. A flow battery is a cross between a traditional battery and a fuel cell. Flow batteries store their energy in external tanks instead of inside the cell itself. If successful, the RFC will: (1) store its energy in a liquid solution at ambient pressure in a conformable plastic tank; (2) be readily packaged inside of an EV given the RFC's high power and energy densities, and (3) be rechargeable either onboard the vehicle like a conventional battery or by rapidly exchanging the discharged solution in the tank with charged solution at a refueling station. A novel recharging method will be employed to dramatically improve the round-trip energy efficiency for cells operating with an air electrode. Technologies like the RFC hold the potential to dramatically decrease the cost of EVs and enable greater adoption of EVs, allowing for increased energy efficiency, decreased petroleum imports, and substantial savings to the average consumer.

United Technologies Research Center

Development of an Intermediate Temperature Metal Supported Proton Conducting Solid Oxide Fuel Cell Stack

UTRC is developing an intermediate-temperature fuel cell for residential applications that will combine a building's heating and power systems into one unit. Existing fuel cell technologies usually focus on operating low temperatures for vehicle technologies or at high temperatures for grid-scale applications. By creating a metal-supported proton conducting fuel cell with a natural gas fuel processor, UTRC could lower the operating system temperatures to under 500 °C. The use of metal offers faster start-up times and the possibility of lower manufacturing costs and additional automation options, while the proton conducting electrolyte offers the potential for higher ionic conductivity at lower temperatures than regular oxygen conducting solid oxide electrolyte materials. An intermediate temperature electrolyte will be used to achieve a lower operating temperature, while a redesigned cell architecture will increase the efficiency and lower the cost of UTRC's overall system.

United Technologies Research Center

Synergistic Membranes And Reactants for a Transformative Flow Battery System (SMART FBS)

The team led by United Technologies Research Center (UTRC) will develop a redox flow battery system that combines next-generation reactants with an inexpensive and highly selective membrane. This SMART-FBS project addresses the two highest cost components in redox flow battery systems: reactants and membranes. The team plans to develop these two components simultaneously using core materials that will work in tandem. Polymer membranes will be developed that include benzimidazole or pyridine structures; ionic conductivity will come from the membrane's structure that allows acid to be imbibed into the polymer. This approach will allow for the use of a low-cost polymer that is durable, selective, and highly conductive. The new reactants will be large organic molecules based upon an extensive theoretical library of potential reactants that has already been established. Multiple membranes and reactants enable a variety of technology options, which should increase the likelihood of success. The project integrates and leverages benefits from each of the team members including: UTRC's state-of-the-art redox flow battery cell performance; innovations in membranes from the University of South Carolina; TPS polymers and membrane-manufacturing capabilities of Advent Technologies; novel active materials based on Harvard University's large library of organic reactants; and Lawrence Berkley National Laboratory's proficiency in characterizing and modeling transport in ion-exchange membranes. If successful, the team's innovations will enable widespread deployment of redox flow batteries for grid-scale electrical energy storage.

University of California, Los Angeles

Thermal Energy Storage With Supercritical Fluids

UCLA and NASA's Jet Propulsion Laboratory (JPL) are creating cost-effective storage systems for solar thermal energy using new materials and designs. A major drawback to the widespread use of solar thermal energy is its inability to cost-effectively supply electric power at night. State-of-the-art energy storage for solar thermal power plants uses molten salt to help store thermal energy. Molten salt systems can be expensive and complex, which is not attractive from a long-term investment standpoint. UCLA and JPL are developing a supercritical fluid-based thermal energy storage system, which would be much less expensive than molten-salt-based systems. The team's design also uses a smaller, modular, single-tank design that is more reliable and scalable for large-scale storage applications.

University of California, Los Angeles

Fuel Cells with Dynamic Response Capability Based on Energy Storage Electrodes with Catalytic Function

UCLA is developing a low-cost, intermediate-temperature fuel cell that will also function like a battery to increase load-following capability. The fuel cell will use new metal-oxide electrode materials--inspired by the proton channels found in biological systems--that offer superior energy storage capacity and cycling stability, making it ideal for distributed generation systems. UCLA's new materials also have high catalytic activity, which will lower the cost of the overall system. Success of this project will enable a rapid commercialization of multi-functional fuel cells for broad applications where reliable distributed generations are needed.

University of California, San Diego

Advanced Energy Storage Modeling, Performance Evaluation and Testing

The University of California, San Diego (UCSD) will conduct testing of existing ARPA-E energy storage technologies in both laboratory and grid-connected conditions. Home to one of the country's largest microgrids, UCSD will apply its advanced understanding of microgrid operation in the California market to select and value applications for storage, in grid-connected and islanded conditions, and to develop duty cycles for energy storage in order to serve individual and stacked applications. UCSD plans to test cells and modules from ARPA-E-funded battery developers in its battery laboratories, and UCSD experts will assist ARPA-E battery developers in resolving issues and enhancing performance. Those batteries that perform well in laboratory testing using the selected duty cycles will then be deployed for extended testing on UCSD's microgrid. This approach will allow UCSD to achieve test results that represent a wide spectrum of applications, determine system performance under a variety of conditions, and eventually generate initial performance data that can be shared with electric utilities and other potential grid storage buyers to inform them of the promise of early-stage storage technologies.

University of California, San Diego

Novel Electrolytes Via Compressed Gas Solvent for Higher Voltage

The University of California at San Diego (UCSD) is developing an early-stage concept for an advanced electrochemical energy storage system. If successful, the new approach would enable higher-energy density and higher-power systems that are able to operate over a much wider temperature and voltage range than today's technologies. Similar to how water is used as a suspension medium for the acid in a conventional lead-acid car battery, the research team is studying the use of certain gases liquefied under pressure as solvents in novel electrolyte systems. The team's work will enhance our understanding of the electrochemical mechanisms involved, and demonstrate their energy storage and cycling capabilities. The work will evaluate the new electrolyte solvents for safety, non-toxicity, non-flammability, performance and cost compared to the traditional organic solvents used today.

University of California, San Diego

Self-Forming Solid-State Batteries

The University of California, San Diego, in partnership with Liox Power and the University of Maryland, will develop a self-forming, high temperature solid-state lithium battery that solves the critical cost and performance problems impeding commercialization of solid-state batteries for electric vehicles. The battery will possess a very long life due to a chemical mechanism that repairs cycling damage automatically. This self-healing electrolyte will also limit the growth of dendrites. Dendrites are branchlike metal fibers that can grow to span the space between the negative and positive electrodes, thereby causing a short circuit. The team plans to reduce costs by designing a manufacturing process for forming solid-state electrolytes and cathodes in a single step by depositing a graded lithium/phosphorous/sulfur composite material as both the cathode and electrolyte. In theory, this composition should be able to remove any deformations due to dendrite formation by a simple thermal cycling process. A non-flammable polymer used within this composite will both add structural strength and eliminate the need for flammable liquid electrolytes. The team projects that the battery will cost half of current lithium-ion batteries while doubling the energy density.

University of Colorado, Boulder

Anion Channel Membranes

The University of Colorado at Boulder (CU Boulder) will develop a new type of anion-exchange membrane for chloride (Cl-) transport that is based on a nanoporous lyotropic liquid crystal structure that minimizes cation crossover by molecular size-exclusion and charge exclusion. Due to a lack of suitable Cl- conducting membranes, flow batteries often use microporous membranes or cation-exchange membranes (CEM) to separate the two electrode chambers. Microporous membranes are inexpensive, but do not provide perfect barriers to intermixing of the reactants (or "crossover") that reduces the battery's efficiency and, in some cases, damages critical components. In contrast, CEMs such as Nafion provide better isolation but are far more expensive, and also permit the migration of water and protons which can change the pH (acidity) and lead to inefficiencies and undesired side reactions in the battery. This project aims to develop a low-cost separator that eliminates crossover in all-iron flow batteries. The membrane allows for ion transport via nanochannels, which are engineered to have sizes below those of common hydrated cations, thus exhibiting perfect cation rejection. In the all-iron battery, key benefits of reduced crossover include increased roundtrip efficiency as well as the reduction of pH swings and water transport, and hence the reduction or elimination of the rebalancing stacks and system management schemes. In the future, the membrane developed in this project could also be used with other lower cost redox couples, including those using two different elements as active species. The low cost, increased efficiency, and long lifetime of these membranes have the potential to significantly increase the economic viability of flow batteries.

University of Delaware

High-Voltage and Low-Crossover Redox Flow Batteries for Economical and Efficient Renewable Electricity Storage

The University of Delaware is developing a low-cost flow battery that uses membrane technology to increase voltage and energy storage capacity. Flow batteries store chemical energy in external tanks instead of within the battery container, which allows for cost-effective scalability because adding storage capacity is as simple as expanding the tank, offering large-scale storage capacity for renewable energy sources. However, traditional flow batteries have limited cell voltages, which lead to low power and low energy density. The University of Delaware is addressing this limitation by adding an additional exchange membrane within the electrolyte material of the battery, creating 3 separate compartments of electrolytes. Separating the electrolytes in this manner allows unprecedented freedom for the battery to exchange ions back and forth between the positive and negative end of the battery, which improves the voltage of the system.

University of Delaware

Highly Conductive, Stable and Robust Hydroxide Exchange Membranes Based on Polyaryl piperidinium

The University of Delaware with their project partners will develop a new class of hydroxide exchange membranes (HEMs) for use in electrochemical devices such as fuel cells. Hydroxide exchange membrane fuel cells (HEMFC), in contrast to PEM fuel cells, can use catalysts based on low-cost metals as well as inexpensive membranes and bipolar plates. However, a low-cost HEM that simultaneously possesses adequate ion conductivity, chemical stability, and mechanical robustness does not yet exist. To address this challenge, the team has developed a family of poly(aryl piperidinium) HEMs that are highly hydroxide conductive, chemically stable, and mechanically robust. These polymers will be designed to provide unprecedented chemical stability, while simultaneously enabling high ion-exchange capacities and low swelling ratios, and mechanical robustness. A major part of the team's project will focus on enhancing the mechanical robustness of HEMs under different levels of humidity. The feasibility of roll-to-roll membrane production will be determined as part of the commercialization efforts. The proposed HEMs have the potential to make hydrogen fuel cell vehicles economically competitive with gasoline-powered vehicles. 

University of Maryland

Highly Conductive, Robust, Corrosion-Resistant Nanocarbon Current Collectors for Aqueous Batteries

The University of Maryland will develop a new type of current collector using a film that is composed of functionalized few-walled carbon nanotubes (FWNTs) and polymers. The team seeks to develop a thin, low-cost current collector that displays high conductivity, excellent mechanical strength, flexibility, and manufacturing scalability. Carbon nanotubes have high conductivity, but in their pure state lack the needed mechanical strength. The FWNT concept will "functionalize" or bolster the outer walls by integrating polymers to increase the mechanical strength. This will give the product the dual benefits of direct tube-on-tube contact for fast recharging and increased mechanical strength and stability from the polymers. Replacement of metal mesh by FWNT-polymer film will not only address current collector corrosion concerns, but will also offer increased energy density due to the substantially lighter weight of these carbon-based materials compared to traditional metallic current collectors.

University of Minnesota

Solar Fuels via Partial Redox Cycles with Heat Recovery

The University of Minnesota is developing a solar thermochemical reactor that will efficiently produce fuel from sunlight, using solar energy to produce heat to break chemical bonds. The University of Minnesota envisions producing the fuel by using partial redox cycles and ceria-based reactive materials. The team will achieve unprecedented solar-to-fuel conversion efficiencies of more than 10% (where current state-of-the-art efficiency is 1%) by combined efforts and innovations in material development, and reactor design with effective heat recovery mechanisms and demonstration. This new technology will allow for the effective use of vast domestic solar resources to produce precursors to synthetic fuels that could replace gasoline.

University of New Mexico

Electrochemical Ammonia Synthesis for Grid Scale Energy Storage

The team led by the University of New Mexico will develop a modular electrochemical process for a power-to-fuel system that can synthesize ammonia directly from nitrogen and water. The proposed synthesis approach will combine chemical and electrochemical steps to facilitate the high-energy step of breaking the nitrogen-nitrogen bond, with projected conversion efficiencies above 70%. By operating at lower temperature and pressure and reducing the air-separation requirement, this technology reduces overall system complexity, thus potentially enabling smaller-scale production at equal or lower costs. Furthermore, the smaller-scale process does not need consistent, baseload power to operate and therefore could be compatible with intermittent renewable energy sources, placing it on a path to be carbon-neutral.

University of South Carolina

A Novel Intermediate-Temperature Bi-functional Ceramic Fuel Cell Energy System

The University of South Carolina is developing an intermediate-temperature, ceramic-based fuel cell that will both generate and store electrical power with high efficiencies. Reducing operating temperatures for fuel cells is critical to enabling distributed power generation. The device will incorporate a newly discovered ceramic electrolyte and nanostructured electrodes that enable it to operate at temperatures lower than 500ºC, far below the temperatures associated with fuel cells for grid-scale power generation. The fuel cell's unique design includes an iron-based layer that stores electrical charge like a battery, enabling a faster response to changes in power demand.

University of South Florida

Development of a Low-Cost Thermal Energy Storage System Using Phase-Change Materials with Enhanced Radiation Heat Transfer

USF is developing low-cost, high-temperature phase-change materials (PCMs) for use in thermal energy storage systems. Heat storage materials are critical to the energy storage process. In solar thermal storage systems, heat can be stored in these materials during the day and released at night--when the sun is not out--to drive a turbine and produce electricity. In nuclear storage systems, heat can be stored in these materials at night and released to produce electricity during daytime peak-demand hours. Most PCMs do not conduct heat very well. Using an innovative, electroless encapsulation technique, USF is enhancing the heat transfer capability of its PCMs. The inner walls of the capsules will be lined with a corrosion-resistant, high-infrared emissivity coating, and the absorptivity of the PCM will be controlled with the addition of nano-sized particles. USF's PCMs remain stable at temperatures from 600 to 1,000°C and can be used for solar thermal power storage, nuclear thermal power storage, and other applications.

University of Southern California

An Inexpensive Metal-free Organic Redox Flow Battery for Grid-scale Storage

USC is developing a water-based, metal-free, grid-scale flow battery that will be cheaper and more rapidly produced than other batteries. Flow batteries store chemical energy in external tanks instead of within the battery container. This allows for cost-effective scalability because adding storage capacity is as simple as expanding the tank. Batteries for grid-scale energy storage must be inexpensive, robust, and sustainable--many of today's mature battery technologies do not meet all these requirements. Using innovative designs and extremely low-cost organic materials, USC's new flow battery has the potential to reduce cost, increase durability, and store increased amounts of excess energy, thereby promoting greater renewable energy deployment.

University of Southern California

A Robust and Inexpensive Iron-Air Rechargeable Battery for Grid-Scale Energy Storage

USC is developing an iron-air rechargeable battery for large-scale energy storage that could help integrate renewable energy sources into the electric grid. Iron-air batteries have the potential to store large amounts of energy at low cost--iron is inexpensive and abundant, while oxygen is freely obtained from the air we breathe. However, current iron-air battery technologies have suffered from low efficiency and short life spans. USC is working to dramatically increase the efficiency of the battery by placing chemical additives on the battery's iron-based electrode and restructuring the catalysts at the molecular level on the battery's air-based electrode. This can help the battery resist degradation and increase life span. The goal of the project is to develop a prototype iron-air battery at significantly cost lower than today's best commercial batteries.

University of Tennessee

Advanced Reversible Aqueous Air Electrode

The University of Tennessee will develop a reversible Oxygen Reduction Reaction (ORR) catalyst that can be used both as a peroxide-producing electrolyzer and in reversible air batteries. The ORR catalyst development seeks to significantly improve peroxide electrolysis efficiency and achieve high charge and discharge rates in air-breathing batteries. In conjunction with the new catalyst, an anion exchange membrane (AEM) will be used to further increase the electrolyzer efficiency and reduce peroxide production costs. In the reversible air battery, the AEM increases battery power performance. Finally, a two-phase flow field design will increase both the current density and current efficiency for peroxide production and can also be used in the reversible air battery to build up a high concentration of hydrogen peroxide for energy storage. This technology could also enable onsite hydrogen peroxide production at small scale.

University of Washington

Optimal Operation and Management of Batteries Based on Real-Time Predictive Modeling and Adaptive Battery Management Techniques

University of Washington (UW) is developing a predictive battery management system that uses innovative modeling software to manage how batteries are charged and discharged, helping to optimize battery use. A significant problem with today's battery packs is their lack of internal monitoring capabilities, which interferes with our ability to identify and manage performance issues as they arise. UW's system would predict the physical states internal to batteries quickly and accurately enough for the data to be used in making decisions about how to control the battery to optimize its output and efficiency in real time. UW's models could be able to predict temperature, remaining energy capacity, and progress of unwanted reactions that reduce the battery lifetime.


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