This Exploratory Topic seeks to develop technologies for medium-voltage (>10 kV) power distribution cables, connectors, and circuit breakers for fully electric aviation applications. Future all-electric, twin-aisle aircraft will require more than 50 MWs of power distribution capability; therefore, the targeted outcome of this topic is to enable megawatt scale distribution with minimal impact on weight while maintaining the high reliability and safety requirements of aviation. Projects will develop functioning prototypes tested to relevant aviation standards in order to broadly address the following critical technical challenges in this space:
- identifying appropriate wiring materials with optimum gravimetric power densities and minimum electrical losses, and evaluating corresponding vacuum or cryogenic systems if necessary
- identifying insulating materials with high dielectric strength, good thermal conductivity, low specific weight, conformality, malleability, and air-void minimization
- assessing connector designs
- developing circuit breakers for aviation applications
- addressing partial discharge related reliability issues that arise from low air pressure environments in aviation
Air travel remains a growing contributor to U.S. Greenhouse Gas (GHG) emissions, with recent estimates placing commercial air travel at nearly 3% of total domestic GHG emissions. In response to this, in 2020, ARPA-E launched two focused programs, REEACH and ASCEND, that may enable the mitigation of GHG emissions in the space through the adoption of electric aviation technologies. REEACH works to develop chemical energy conversion systems to convert Carbon Neutral Liquid Fuels (CNFLs) to electric power for aircraft propulsion; while ASCEND encourages the development of lightweight and ultra-efficient integrated electric motors, drives and thermal management systems to facilitate net-zero carbon emissions. CABLES teams will further complement these programs and their goal of developing electric aviation solutions by addressing another challenge existing within all-electric aircraft, power distribution.
Projects Funded Within This Exploratory Topic
GENERAL ELECTRIC GLOBAL RESEARCH
MEGAWATT ANY-ALTITUDE GAS INSULATED CABLE SYSTEM FOR AIRCRAFT POWER DISTRIBUTION (MAAGIC)
GE Research will develop a safe, lightweight, and altitude-capable megawatt power cable system with electromagnetic interference shielding capability for large aircraft. The proposed 10 MW cable system is expected to achieve ten times greater power density than conventional technology without degradation by partial discharge and is fire safe and oil resistant. This cable system will enable all-electric distributed propulsors for future large aircraft to achieve zero emissions by using aluminum conductors insulated and cooled with CO2, both of which are readily available, manufacturable materials. The proposed cable technology can also be used in other applications requiring high cable power density with a relatively small footprint including electric ships, submarines, and offshore wind turbine platforms.
ILLINOIS INSTITUTE OF TECHNOLOGY
SUPERCONDUCTING MOMENTARY CIRCUIT INTERRUPTER: FAULT PROTECTION WITH ULTRALOW LOSS AND ULTRAFAST RESPONSE FOR FUTURE ELECTRIC AVIATION
Fault protection must be provided for future turboelectric aircraft’s medium-voltage direct current power systems, but not necessarily from conventional circuit breakers. Illinois Institute of Technology will develop a 10 kV/150A superconducting momentary circuit interrupter (SMCI) to provide fault protection with ultralow power loss (<1 W), ultrafast response (<10 μs or ten millionth of a second), and high-power density. The architecture comprises an SMCI with a fast mechanical disconnect switch. Under normal operation, the SMCI conducts a DC load current through a high-temperature superconducting winding of a pulse transformer. Under a fault condition, the SMCI injects a high transient voltage via the transformer, drives the fault current to zero quickly, and holds the current as a small AC ripple current, allowing the mechanical switch to open safely and isolate the fault.
VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY
HIGH POWER DENSITY COST-EFFECTIVE MV DC AIRCRAFT CABLE
To make the power density of electric aircraft closer to conventional aircraft, an electric power system (EPS) with high power delivery and low system mass is necessary. As an essential component of aircraft EPS, cables are necessary to transmit power from one node to another. Virginia Tech will develop a high-power density, cost-effective ±5 kV cable for twin-aisle all-electric aircraft. Innovations include conductors with increased current-carrying capacity; a multilayer, multifunctional insulation system made of exceptionally high thermal conductivity materials; and a new insulation solution for higher voltages with superior mechanical strength and electrical reliability. Designed for DC voltage, the new insulator will allow fewer partial discharge events and provide improved electromagnetic interference protection.
UNIVERSITY OF TENNESSEE
ULTRA-LIGHT TIGHTLY-INTEGRATED MODULAR AVIATION-TRANSPORTATION ENABLING SOLID-STATE CIRCUIT BREAKER (ULTIMATE-SSCB)
A medium voltage direct current (MVDC) system provides lower distribution losses, higher power carrying capacity, and reduced conductor material compared with its low voltage alternative current counterpart. These benefits are critical to meet stringent weight and size requirements for aviation applications. The University of Tennessee will develop a lightweight, reliable, efficient, and flexible protection solution for future electrified aircraft propulsion systems that are expected to use a 1 kV to 10 kV MVDC distribution system. The team will develop a modular architecture with a highly integrated customized module, use advanced solid-state semiconductor devices cooled at cryogenic temperatures, and integrate protection intelligence to achieve project objectives.
ADVANCED CONDUCTOR TECHNOLOGIES
LIGHTWEIGHT, HIGH-POWER DENSITY, SELF-PROTECTING SUPERCONDUCTING POWER CABLES AND CONNECTORS FOR ELECTRIC AIRCRAFT APPLICATIONS
Advanced Conductor Technologies will develop two-pole, high-temperature, superconducting DC power cables and connectors with a power rating of up to 50 MW to enable twin-aisle aircraft with distributed electric propulsion to reduce carbon emissions. The cables and connectors will contain insulation independent of the cryogenic medium used as coolant and allow an operating voltage of 10 kV. Because they have intrinsic fault current limiting capabilities, the cables can protect the power distribution network from over-currents. This intrinsic capability will reduce the complexity of the power distribution network while improving its reliability.
HYPER TECH RESEARCH
POWER TRANSMISSION CABLE FOR ELECTRIC AIRCRAFT USING BIO LNG FOR COOLING AND THERMAL MANAGEMENT
There are two key engineering challenges in the development of 10 kV, 10 MW electric power distribution cables for double-aisle passenger aircraft. One is providing sufficient electrical insulation at high voltages and the second is transferring heat away from the conductors. Hyper Tech Research will decrease the resistivity of copper-clad aluminum conductors by a factor of three by maintaining the temperature of the conductors at around 120 Kelvin. The goal of the technology is to reduce the conductor size, cryostat size, and cable volume and weight to significantly lower the mass-per-unit length of the cable. The team proposes to use available carbon neutral fuel, such as bio-liquefied natural gas (Bio-LNG), for electrical insulation and as a heat transfer medium. After cooling the cable, the Bio-LNG fuel will be consumed in an onboard turbogenerator or fuel cell.