ARPA-E seeks to mitigate the greenhouse gas emissions associated with commercial air travel at minimum economic cost by developing elements of an ultra-high efficient aircraft propulsion system that uses Carbon Neutral Liquid Fuels (CNLFs).[1] Since these fuels generally either have lower specific-energies (kWh/kg) or are projected to have higher cost than traditional fossil-based jet fuels, ultra-high conversion efficiency is critical for the economic viability of this approach. An electrified propulsion system framework postulated by ARPA-E (Fig. 1) could potentially leverage multiple sources of stored energy (e.g. CNLF, batteries, etc.) to facilitate emerging propulsion concepts (e.g. distributed propulsion) and enable net-zero carbon emissions for long range, narrow-body, commercial aircraft.
The objective of the Range Extenders for Electric Aviation with Low Carbon and High Efficiency (REEACH) program is the development of one element of the electrified propulsion system framework: a system for the conversion of chemical energy contained in energy dense CNLFs (green block in Fig. 1) to electric power for aircraft propulsion and hotel loads. (The development of the all-electric powertrain depicted in Fig. 1 is the objective of a separate ARPA-E FOA.[2])
[1] CNLFs are defined in this FOA as energy dense liquid fuels with no net greenhouse gas emissions or net carbon footprint. They are made by converting molecules contained in air (N2, CO2), water, and/or biomass using renewable energy into energy-carrying fuels that are liquid at moderate temperatures and pressures.
[2] Aviation-class Synergistically Cooled Electric-motors with iNtegrated Drives (ASCEND) FOA to be released by ARPA-E.