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Renewable Energy to Fuels Through Utilization of Energy-Dense Liquids

Most liquid fuels used in transportation today are derived from petroleum and burned in internal combustion engines. These energy-dense fuels are currently economical, but they remain partially reliant on imported petroleum and are highly carbon intensive. Alternatives to internal combustion engines, like fuel cells, which convert chemical energy to electricity, have shown promise in vehicle powertrains, but are hindered by inefficiencies in fuel transport and storage. Projects in the Renewable Energy to Fuels Through Utilization of Energy-Dense Liquids (REFUEL) program seek to develop scalable technologies for converting electrical energy from renewable sources into energy-dense carbon-neutral liquid fuels (CNLFs) and back into electricity or hydrogen on demand. REFUEL projects will accelerate the shift to domestically produced transportation fuels, improving American economic and energy security and reducing energy emissions.
For a detailed technical overview about this program, please click here.    

Bettergy Corp.

Low Temperature Ammonia Cracking Membrane Reactor for Hydrogen Generation

Bettergy will develop a catalytic membrane reactor to allow on-site hydrogen generation from ammonia. Ammonia is much easier to store and transport than hydrogen, but on-site hydrogen generation will not be viable until a number of technical challenges have been met. The team is proposing to develop a system that overcomes the issues caused by the high cracking temperature and the use of expensive catalysts. Bettergy proposes a low temperature, ammonia-cracking membrane reactor system comprised of a non-precious metal ammonia cracking catalyst and a robust composite membrane. A one-step cracking process will be used to convert ammonia into hydrogen and nitrogen, with the hydrogen passing through the selective membrane leaving only nitrogen as the byproduct. If the team is successful, the conversion efficiency will be higher than conventional methods because the hydrogen is removed from the system as it is being produced. The low-temperature reactor will provide greater reliability, ease of operation, and cost effectiveness to hydrogen fueling stations. The team's technology could also be applicable for stationary fuel cell systems and the semiconductor, metallurgy, chemical, aerospace, and telecommunications industries.

Chemtronergy, LLC.

Cost-effective, Intermediate-temperature Fuel Cell for Carbon-free Power Generation

Chemtronergy will develop an advanced solid oxide fuel cell (SOFC) system to electrochemically convert ammonia into electricity. Conventional SOFC systems are manufactured using ceramic fabrication techniques that are time-consuming, energy-intensive, and have high material costs. SOFCs also typically operate at 700-900°C to chemically activate the fuel feedstock and ensure that it is sufficiently cracked or reformed for electrochemical use. This high temperature, however, imposes harsh operating conditions and stresses on the materials, which further increases costs. To address these challenges, the team proposes to lower the operating temperature below 650°C and to develop anode, cathode, and electrolyte materials using a combination of advanced materials discovery, reaction kinetics modeling, and 3D printing technology for large-scale rapid prototyping. The team hopes to greatly reduce the cost of SOFC systems while providing a distributed power-generating option with high efficiency, long life, and a reduced carbon footprint.

FuelCell Energy, Inc.

Protonic Ceramics for Energy Storage and Electricity Generation with Ammonia

FuelCell Energy will develop an advanced solid oxide fuel cell system capable of generating ammonia from nitrogen and water, and renewable electricity. The unique design will also allow the system to operate in reverse, by converting ammonia and oxygen from air into electricity. A key innovation in this project is the integration of proton-conducting ceramic membranes with new electride catalyst supports to enable an increase in the rate of ammonia production. Combining their catalyst with a calcium-aluminate electride support increases the rate of ammonia formation by reducing coverage of the catalyst surface by hydrogen and allowing the nitrogen to use all of the catalyst area for reactions. The modular nature of this system allows for its deployment closer to the point of use at agricultural and industrial sites, working to both produce ammonia for immediate or delayed use and to use the ammonia to generate electricity after it has been transported to population centers.

Gas Technology Institute

A Novel Catalytic Membrane Reactor for DME Synthesis from Renewable Resources

Gas Technology Institute (GTI) will develop a process for producing dimethyl ether (DME) from renewable electricity, air, and water. DME is a clean-burning fuel that is easily transported as a liquid and can be used as a drop-in fuel in internal combustion engines or directly in DME fuel cells. Ultimately carbon dioxide (CO2) would be captured from sustainable sources, such as biogas production, and fed into a reactor with hydrogen generated from high temperature water splitting. The CO2 and hydrogen react on a bifunctional catalyst to form methanol and a subsequently DME. To improve conversion to DME, GTI will use a novel catalytic membrane reactor with a zeolite membrane. This reactor improves product yield by shifting thermodynamic equilibrium towards product formation and decreases catalyst deactivation and kinetic inhibition due to water formation. The final DME product is separated and the unreacted chemicals are recycled back to the catalytic reactor. Each component of the process is modular, compact, and requires no additional inputs aside from water, CO2, and electricity, while the entire system is designed from the ground up to be compatible with intermittent renewable energy sources.

Giner Inc.

High-Efficiency Ammonia Production from Water and Nitrogen

Giner will develop advanced membrane and catalysts electrolyzer components that can electrochemically generate ammonia using water, nitrogen and intermittent renewable energy sources. Their electrochemical reactor operates at a much lower pressure and temperature than conventional methods, which can lead to significant energy savings. Some of their key innovations include metal nitride catalysts and high temperature poly(aryl piperidinium) anion exchange membranes (AEM) to boost the ammonia production rate and enhance process stability. The components will be integrated into Giner's existing water electrolysis platform to maximize the overall system efficiency. The project team has a diverse set of expertise which it will use to develop advanced catalysts and membranes; to integrate a water electrolyzer that can be easily manufactured; and to perform a techno-economic analysis that addresses the use of renewable energy sources. When completed, the system will decrease ammonia production capital and operating costs significantly compared to conventional processes.

Molecule Works Inc.

Novel Electrochemical Membrane Reactor for Synthesis of Ammonia from Air and Water at Low Temperature and Low Pressure

Molecule Works will develop an electrochemical membrane reactor to produce ammonia from air, water, and renewable electricity. The team proposes a solid-state, thin-film alkaline electrochemical cell that has the potential to enhance ammonia synthesis productivity and energy efficiency, while lowering the cell material and fabrication costs. Current systems for ammonia production all have several challenges. Some use acidic membranes that can react with ammonia, resulting in lower conductivity and reduced membrane life. Others that operate at low temperatures (<100°C) may have low rates of reactions, while those that operate at high temperatures (>500°C) have long-heating processes that make them less practical for intermittent operation using renewable energy. Alkaline electrolytes have a number of advantages over traditional cells. Notably, alkaline electrolytes allow a larger area of the catalyst for nitrogen activation, increasing the rate of ammonia production. The team's system operates at a much lower temperature and pressure than the traditional ammonia production process. The modular nature of the system will also allow it to be deployed near the point of use.

Opus 12 Incorporated

Renewable Electricity-Powered Carbon Dioxide Conversion to Ethanol for Storage and Transportation

Opus 12 will develop a cost effective, modular reactor to electrochemically convert CO2 to ethanol in one step using water, air, and renewable electricity. Electrochemical reduction of CO2 has been demonstrated in laboratories to produce different fuels and chemicals, but these technologies do not provide efficient conversions and can only be executed in non-economical reactors. The Opus 12 team will integrate its novel cathode layer formulation, containing CO2 reducing catalysts and a polymer electrolyte, into an existing proton exchange membrane (PEM) electrolyzer architecture. Their unique polymer-electrolyte blend used in the cathode catalyst layer acts to minimize competing reactions by controlling the pH at the active sites. Currently, PEM electrolyzers are limited to hydrogen production, but the team's approach expands their use to include high-efficiency ethanol synthesis. PEM electrolyzers are also a well-established technology and integrating them into an existing reactor architecture reduces system capital costs and scale-up risk. PEM electrolyzers can also ramp quickly, allowing the use of intermittent, low-cost renewable electricity. They operate at high current density, leading to a small footprint, and they are operationally simple, with no need for specialized operators on site. The team's system will operate at less than 80°C and near atmospheric pressure with a coproduct of pure oxygen. The team's pilot reactor will be one of the first examples of a PEM electrolysis system used to generate a liquid fuel directly.

Rensselaer Polytechnic Institute

A Novel Hollow Fiber Membrane Reactor for High Purity Hydrogen Generation from Thermal Catalytic Ammonia Decomposition

Rensselaer Polytechnic Institute (RPI) will develop an innovative, hollow fiber membrane reactor that can generate high purity hydrogen from ammonia. The project combines three key components: a low-cost ruthenium (Ru)-based catalyst, a hydrogen-selective membrane, and a catalytic hydrogen burner. Pressurized ammonia vapor is fed into the reactor for high-rate decomposition at the Ru-based catalyst and at a reaction temperature below 450°C. Ceramic hollow fibers at the reactor boundary will extract the high purity hydrogen from the reaction product. Residual hydrogen will be burned with air in the catalytic burner to provide heat for ammonia cracking. Both the high-purity hydrogen and the heated exhaust from the catalytic hydrogen combustion are fed past the ammonia vapor before it enters the reactor, increasing its temperature and improving the overall efficiency of the process. The team seeks to develop a compact and modular membrane reactor prototype that can deliver hydrogen at high rate per volume from ammonia decomposition at relatively low temperatures (<450°C) and high conversion (>99%).

Research Triangle Institute

Innovative Renewable Energy-based Catalytic Ammonia Production

Research Triangle Institute (RTI) will develop a catalytic technology for converting renewable energy, water, and air into ammonia. Their work focuses on three innovations: the development of an ammonia synthesis catalyst for improved reactions, refinement of the ammonia synthesis to handle intermittent loads, and optimized and scalable technologies for air separation to produce high-purity nitrogen. Their ammonia synthesis catalyst features increased surface area, high dispersion, and high thermal stability - enabling the system to operate at much lower temperatures and pressures, lowering energy consumption by 35%. It also reduces the balance of plant costs by simplifying the design and decreasing refrigeration loads. By using low-cost nitrogen purification techniques, they aim to lower the cost and amount of nitrogen required. When completed, the project will result in a small-scale ammonia synthesis system that is economically viable and can start and stop in synchronization with intermittent renewable power sources.

SAFCell, Inc.

Distributed Electrochemical Production and Conversion of Carbon-Neutral Ammonia

SAFCell will develop a novel electrochemical system that converts ammonia to hydrogen. The key innovation is the use of a solid acid electrolyte, a type of electrolyte that is stable in the presence of ammonia while under the operating conditions needed for reactions. Solid acid fuel cell stacks operate at intermediate temperatures (around 250°C) and demonstrate high tolerances to typical anode catalyst poisons such as carbon monoxide and hydrogen sulfide without a significant decrease in performance. The system also aims to realize the conversion of ammonia along with the purification and compression of hydrogen in a single, cost-effective system, thus greatly simplifying the infrastructure required to transport and store hydrogen. These properties give solid acid fuel cell devices advantages over other fuel cell technologies in cost, durability, start/stop cycling, fuel flexibility, and simplified system design.

Skyre, Inc.

Electricity From an Energy-Dense Carbon-Neutral Energy Carrier

Skyre will develop a system to capture carbon dioxide (CO2) emitted from industrial or chemical processes, electrochemically convert it into methanol, and further transform the methanol into dimethyl ether (DME). DME can be stored and transported using existing infrastructure and can be converted into electricity to provide power for transportation and distributed energy generation. To convert CO2 to methanol, new catalysts that improve efficiency and lower costs will be developed that are highly selective and durable, building on the team's prior work with transition-metal-supported catalysts. The CO2 reduction technology is designed to be modular and scalable. The system does not require a continuous supply of power and can, therefore, use intermittent renewable energy sources. These technologies offer a path to better utilize domestic resources, providing long-term energy storage from wind and solar, and long-distance energy delivery from remote locations.

Storagenergy Technologies, Inc.

High Rate Ammonia Synthesis by Intermediate Temperature Solid-State Alkaline Electrolyzer 

Storagenergy Technologies will develop a solid-state electrolyzer that uses nitrogen or air for high-rate ammonia production. Current electrolyzer systems for ammonia production have several challenges. Some use acidic membranes that can react with ammonia, resulting in lower conductivity and reduced membrane life. Operation at conventional low temperatures (<100°C) traditionally have low rates of reactions, while those that operate at high temperatures (>500°C) have long-heating processes that make them less practical for intermittent operation using renewable energy. The Storagenergy team has chosen a system that operates at an intermediate temperature (100-300°C) and uses an alkaline membrane environment to minimize side-reactions with the ammonia. To develop their technology, the team will combine a low-cost solid-state hydroxide conducting membrane, a nanostructured cathode catalyst, and a noble metal-free nanoparticle catalyst on the anode. This proposed system will synthesize ammonia more efficiently and at much lower temperatures and pressures than traditional ammonia production techniques. The modular nature of the system will also allow it to be deployed near the point of use.

University of Delaware

Direct Ammonia Fuel Cells for Transport Applications

The University of Delaware (UD) will develop a direct ammonia fuel cell operating near 100°C that will efficiently convert ammonia to electricity for electric vehicles and other applications. The team will develop new materials, including low-cost, high-performance hydroxide exchange membranes (HEMs) that can maintain stability near 100°C and novel ammonia oxidation catalysts. Proton exchange membranes are traditionally used in fuel cell applications, but HEMs have a number of advantages when ammonia is used as the direct fuel source including reduced side-reactions, prevention of ammonia crossover, and enabling of the use of lower cost catalysts. Finally, the team will target new developments in the full membrane electrode assembly structure and metal hardware fuel cell stack design, optimizing the system's operating conditions for effective water management and minimized fuel crossover. The goal is an ammonia-fed, cost-competitive fuel cell generating high power density, with rapid start-up enabled by the low operating temperature.

University of Minnesota

Small Scale Ammonia Synthesis Using Stranded Wind Energy

The University of Minnesota (UMN) will develop a small-scale ammonia synthesis system using water and air, powered by wind energy. Instead of developing a new catalyst, this team is looking to increase process efficiency by absorbing ammonia at modest pressures as soon as it is formed. The reactor partially converts a feed of nitrogen and hydrogen into ammonia, after which the gases leaving the reactor go into a separator, where the ammonia is removed and the unreacted hydrogen and nitrogen are recycled. The ammonia is removed completely by selective absorption, which allows the synthesis to operate at lower pressure. This reduced pressure makes the system suitable for small-scale applications and more compatible with intermittent energy sources. The success of preliminary experiments suggests that this new approach may be fruitful in reducing capital and operating costs of ammonia production.

West Virginia University Research Corporation

Renewable Energy to Fuels Through Microwave-Plasma Catalytic Synthesis of Ammonia

West Virginia University Research Corporation (WVURC) will develop a process to convert renewable electricity, water, and air into ammonia using plasma excitation at low temperatures and pressures. This process is different from both electrochemical conversion processes and catalytic processes like the HB process. In this form of physical activation, the microwave-plasma process can activate nitrogen and hydrogen, generating ions and free radicals that react over the catalyst surface to form ammonia. Under the correct conditions, microwave heating can selectively heat the catalyst to the temperature required for reactions without heating the surrounding area. This combination of a very hot catalyst and cool surroundings leads to overall lower reaction temperatures and improved energy efficiency. The lower pressure required for the process will also simplify the design. Both features enable better integration with renewable energy sources because the system can be turned on and off more quickly. Such advantages increase the cost competitiveness of the team's approach.

Wichita State University

Alkaline Membrane-Based Ammonia Electrosynthesis with High Efficiency for Renewable and Scalable Liquid-Fuel Production

Wichita State University will develop a renewable energy-powered electrochemical device for ammonia production at ambient temperature. This allows the unit to consume less energy but maintain high productivity. The goal is an alternative path for ammonia electrochemical synthesis from water and air without the need for the high temperature and pressure required by the Haber-Bosch process. The key innovation is the use of a hydroxide-exchange membrane (HEM) polymer electrolyte. The more commonly used proton exchange membranes (PEM) present major challenges leading to low efficiency for PEM-based ammonia electrosynthesis. Switching to HEMs will reduce side-reactions, allow the use of non-precious metal catalysts, and eliminate ammonia crossover and electrolyte contamination. As such, HEM-supported ammonia electrosynthesis may offer high coulombic efficiency and high ammonia productivity, without losing the key advantages of PEM-based electrosynthesis - operating under ambient conditions and using air and water as reactants. Unlike the Haber-Bosch process, electrochemical synthesis of ammonia can be made much smaller and can operate intermittently which allows better integration with renewable electricity.
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