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High Power Density Carbon Neutral Electrical Power Generation for Air Vehicles

Tennessee Technological University will combine a Solid Oxide Fuel Cell (SOFC) stack with a gas turbine combustor to address challenges faced in all electric propulsion-based aviation. The combined SOFC combustor concept maximizes power density and efficiency while minimizing system complexity, weight, and cost. By eliminating components and subsystems typically found in fuel cell-gas turbine hybrid systems, this design provides operational flexibility with a rapid response to flight and load conditions and enables system startup in less than 30 minutes. This elegant and revolutionary SOFC-combustor concept meets specific power and energy requirements to enable economically viable net-zero greenhouse gas emissions for long-range electric commercial aviation.

ARPA-E REEACH Announcement

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Cryo Thermal Management of High Power Density Motors and Drives

In partnership with Hyper Tech Research, this project aims to design and demonstrate a multi-MW, high-efficiency, and high-power density integrated electric propulsion motor, drive, and thermal management system that meets the performance requirements of future hybrid electric, single-aisle passenger aircraft. The proposed technology incorporates an advanced and high-performance induction electric machine with a novel advanced thermal management techniques for synergistic cooling that safely uses cryogenic bio-LNG as the energy source for power generation and a large thermal-battery cooling system to provide a highly compact, light, and efficient thermal management system capability throughout all the different flight phases of a commercial narrow-body aircraft. If successful, the system will allow for a cost-effective motor capable of operating at a higher current density compared with existing conventional non-cryogenic motors without using superconductors.

ARPA-E ASCEND Announcement

Atmosphere Independent Bipropellant Solid Oxide Fuel Cells (SOFCs) for On-Orbit Space Power

Sustained duration power output onboard modern spacecraft is primarily constrained by the rate of photovoltaic energy collection or the limited energy density of batteries. An alternative energy source is mandatory during eclipse, lunar night scenarios, or short manned missions such as the Apollo program where the long duration energy consumption made batteries infeasible. As a solution, the chemical energy of the propellants onboard a spacecraft can be utilized for electrochemical work in a fuel cell, thereby taking advantage of the much higher specific energy of liquid fuels. The hypergolic pair MMH/NTO represent a specific energy density approximately eight times that of modern space-worthy lithium-ion batteries. The option to use propellants for thrust and/or power greatly reduces the invested weight in the final plumbing and storage. Regenerative fuel cells have already been studied as a prospective power sources for satellites, as well as reusable fuel cells fed with hypergolic propellants for spacecraft. A similar solid oxide electrolyzer cell has already been successfully integrated into the Mars Perseverance rover. This project seeks to validate the concept of a solid oxide fuel cell integrated with a hypergolic bipropellant propulsion system.

Hypersonic On-Board Power and Thermal Management System

Hypersonic vehicles offer promise as a platform to support traveling worldwide.  However, hypersonic vehicles lack the ability to produce onboard power with traditional generators due to their use of supersonic combusting ramjets (scramjets), which do not have rotating shafts from which power can be extracted. Therefore, hypersonic vehicles lack significant electrical power production for supporting advanced electronics, electric actuators and weapons.  Hypersonic vehicles require extensive thermal management systems as well.  Electric power production by APUs can be derived from many different technologies, including internal combustion engines, gas turbines, fuel cells, batteries, thermoelectric, nuclear or magnetohydrodynamic generators.  Hypersonic flight introduces challenges when it comes to producing power onboard.  For example, access to air is not trivial.  Air may be provided through engine bleeds, which is provided at extreme temperatures, >700ÂșC.  This reduces the specific power of internal combustion and gas turbine engines.  Therefore, an alternative technology which does not require air or can utilize high temperature air sources is beneficial.  Thermal electric devices need cooling air for a heat sink and nuclear based technologies introduce technical and political challenges.  Batteries provide a viable solution but are limited in energy density and the ability to perform in missions >30 minutes.  As an alternative, a solid oxide fuel cell (SOFC) can operate within these conditions.  SOFCs utilize high temperature air sources for their oxidants. Therefore, SOFC provide an opportunity for power production on hypersonic vehicles.