Description:
TECHNOLOGY AREA(S): Materials
OBJECTIVE: Development of a man-portable 2kW SOFC system with 13kW power spikes. System to power robotic vehicles, ground vehicle auxiliary systems or exoskeletons. System durability will be increased as well.
DESCRIPTION: Solid Oxide Fuel Cell (SOFC) systems allow for power generation using hydrocarbon fuels (such as JP-8, propane, butane or methane) which are readily available, instead of hydrogen gas, which is not as easily obtainable and requires additional storage and/or equipment to use and produce. In addition, SOFC systems also have high power densities (1), high electrical efficiencies (1), a lower acoustic signature than internal combustion engines (2), produce water as a byproduct (3), have the highest tolerance for sulfur in the fuel of any fuel cell type (3) and do not require the use of precious metal catalysts for operation (3). These advantages make SOFC systems (i.e. stack and balance of plant components) useful as auxiliary power sources to charge batteries on robotic vehicles and exoskeleton systems, run peripheral equipment to alleviate power consumption from the main power plant, export power from the vehicle to power stationary devices and have the ability to run near-silent for silent watch operations. Despite these advantages, SOFC stack technology used in today’s light-weight, man-portable systems are not capable of suppling enough power in the space-claim provided and also have low system durability. Smaller scale SOFC systems currently exist that would fit into a similar space claim as proposed here, but the power supplied by those systems is lower than 2kW. The 2kW of power generated by the SOFC stack, with the system capable of up to 13kW intermittent power spikes using internal batteries, proposed in this topic is viewed as an adequate starting power for use with robotic vehicles, auxiliary systems on ground vehicles and exoskeleton systems. Advancement of new novel materials used within the system construction (such as catalysts used in electrode construction and oxygen transport materials used in electrolyte construction), increased catalyst loading, optimized system design and innovative geometries used in stack design to increase active surface area can all be investigated and developed to address this issue. The SOFC system (i.e. SOFC stack, internal batteries for 13kW power, fuel and balance of plant components) will have the following requirements in addition to meeting the 2kW power. The system will have a power density of at least 94 W/kg or have a total mass of 45 kg while having a total system volume of 4,000 cubic inches or less. The system will produce 36-48V of electricity and be able to supply power using the attached fuel source for 4-5 hours continuously. The system will be able to thermally cycle between 50-100 times without the SOFC system power degrading below 2kW (excluding internal battery power). The system will be able to operate for at least 1,000 hours (combined operation time or single continuous use) without the SOFC system power degrading below 2kW (excluding internal battery power). The system will have a start time of 30 minutes or less to achieve 2kW of continuous power with 13kW intermittent power. The target system cost, for commercialization purposes, is expected to be between $5,500/kW and $8,000/kW based on projected system costs from the DOE. The system will be capable of being operated with compressed hydrogen gas or with light hydrocarbon fuels (such as butane, propane or methane). These system requirements are standard with less compact SOFC systems, which should be preserved for this more compact system as well (4), (5).
PHASE I: This phase will focus on conducting a feasibility study to determine the best approach to achieve the SOFC systems requirements listed above. This study will be used to identify materials and different fabrication approaches that will allow the SOFC system to achieve the desired system power output. The feasibility study will also focus on methods of increasing system durability and methods of eliminating failure points during operation.
PHASE II: Phase II will focus on optimizing the SOFC system design and conducting durability experiments. Experiments will be conducted in stages first by using single cells or short stacks (5-cell stacks). Stack size will then gradually be increased and each new stack size will be tested to identify degradation and durability failure modes until a full stack passes testing criteria. SOFC system power will be increased to 2kW by conducting experiments on the system to identify points of parasitic losses and novel approaches of manufacturing the SOFC system to minimize those losses through different material choices or system design. A preliminary investigation should also be completed in order to determine the cost of fabricating the SOFC devices and stacks.
PHASE III: The system should be scalable to provide power to the military in such areas as: 1. Robots and exoskeletons used for reconnaissance and bomb disposal, 2. Drone aircraft used for reconnaissance and short to medium ranged strikes, and 3. Auxiliary power to ground vehicles to save energy costs and for silent watch capability. The system should also be scalable for the commercial market to provide power in areas of: 1. Power generation for homes, 2. Auxiliary power for ground commercial vehicles, and 3. Auxiliary power for light commercial aircraft. The system should also conform to particular dimensions of a space claim and provide the required amount of power for each application.
REFERENCES:
1: Y. Li et al., Energies, 8, (2015), http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=27&ved=0ahUKEwia_YzW8ufTAhUq54MKHcQKCZg4FBAWCEswBg&url=http%3A%2F%2Fwww.mdpi.com%2F1996-1073%2F8%2F3%2F1896%2Fpdf&usg=AFQjCNG01yLyw-Cotgmq_PQplkF3VJflCA&sig2=E4AVjBfZZaWaFAIykT4y_w
2: National Research Council, Meeting the Energy Needs of Future Warriors, (2004), https://books.google.com/books?id=Z6BVAgAAQBAJ&pg=PA23&lpg=PA23&dq=SOFC+lower+acoustic+signature&source=bl&ots=4Sx1FqL1Df&sig=4_IhylmWerrb2m0SGNzYEpvmeEk&hl=en&sa=X&ved=2ahUKEwjM7cvow7jdAhWE0VMKHRwqBd8Q6AEwAXoECAkQAQ#v=onepage&q=SOFC%20lower%20acoustic%20signature&f=false
3: Office of Energy Efficiency & Renewable Energy, Fuel Cell Technology Office, (2018), https://www.energy.gov/eere/fuelcells/types-fuel-cells
4: Atrex Energy, Product Specification, http://www.atrexenergy.com/services-resources/technical-information
5: Protonex, P-200i SOFC Technical Specifications, https://protonex.com/wp-content/ uploads/2016/04/ Protonex-P200i.pdf
KEYWORDS: Solid Oxide Fuel Cell, Fuel Cell, Alternative Energy, Auxiliary Power, Exportable Power, Ground Vehicles, Robotics, Exoskeleton
