The concept More Electric Aircraft (MEA) aims for changing the aircraft systems to be fully powered by electricity.
Recent advances in electrical motors, energy storage systems, and power electronics converters (PEC) are leading the aircraft propulsion to become increasingly electrical (Sliwinski et al. NASA’s Subsonic Fixed Wing project identified four “corners” to be overcome: noise, emissions, aircraft fuel burn, and field length (Kim et al. Despite this, several goals must be achieved to make the technology viable. Hybrid-electric propulsion system (HEPS) appears as the most viable solution for an energy efficient, cleaner and quieter aeronautical propulsion, since it is able to combine the advantages of the conventional propulsion system and the all-electric approach (Sliwinski et al. Some of the main advantages of HEP compared with the traditional propulsion are: (a) increasing the global aircraft efficiency (b) increasing aircraft reliability, power distribution/quality, and flight range (c) emissions and noise reduction (d) capacity of extending the market to smaller airports (Sliwinski et al.
This hybridization can be achieved combining ICEs or FCs with EMs and batteries (González Espasandín et al. This alternative has been called by some authors hybrid-electric propulsion (HEP) (Hung and Gonzalez 2012). Whereas air transport industry is responsible for a considerable part of greenhouse gas emissions, a concept where ICEs and electric motors (EM) are combined in the propulsion to increase vehicle efficiency and reduce the impact is being analyzed (Zhang et al. In addition, the foreseen financial benefits of increased energy efficiency have motivated the transport industry to invest in propulsion alternatives (IATA 2019). However, its environmental impact in terms of noise and pollutant emissions has gained public attention (IATA 2019). Since the introduction of jet engines, the air transport industry has doubled its size every 20 years, the highest rate in transport sector, and it is expected to continue in a similar rate in the next years. Brazilian research in these challenging areas is in the beginning, and a multidisciplinary collaboration will be critical for success in the next few years. Computational models supported by powerful simulation tools will be a key to support research and aircraft HEP design in the coming years.
Turbo-electric hybrid architecture combined with distributed propulsion and boundary layer ingestion seems to have more success for regional aircraft, attaining environmental goals for 20. All-electric architecture seems to be more adapted to UAM. The last one will gradually come into service, starting with small aircraft according to developments in energy storage, fuel cells, aircraft design and hybrid architectures integration. The first one is expected to come into service in the next 10 years with small devices. Two commercial areas are in evolution, electrical urban air mobility (UAM) and hybrid-electric regional aircraft. Several changes on aircraft propulsion will occur in the next 30 years, following the aircraft market demand and environmental regulations. The present work is a survey on aircraft hybrid electric propulsion (HEP) that aims to present state-of-the-art technologies and future tendencies in the following areas: air transport market, hybrid demonstrators, HEP topologies applications, aircraft design, electrical systems for aircraft, energy storage, aircraft internal combustion engines, and management and control strategies.