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An electric aircraft is an aircraft that runs on electric motors rather than internal combustion engines, with electricity coming from fuel cells, solar cells, ultracapacitors, power beaming,[1] and/or batteries.
Currently flying electric aircraft are mostly experimental demonstrators, including manned and unmanned aerial vehicles. Electrically powered model aircraft have been flown since the 1970s, with one report in 1957.[2]
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In 1883 Gaston Tissandier was the first to use electric motors in airship propulsion.[3] The following year, Charles Renard and Arthur Krebs flew La France with a more powerful motor.[3]
Nikola Tesla envisaged using electrically powered aircraft, powered by beams from the ground or the ionosphere.
Electric motors have been used for model fixed-wing aircraft since from at least 1957, with a challenged claim from 1909.[4]
In 1964 William C. Brown demonstrates on CBS News with Walter Cronkite a model helicopter that receives all of the power needed for flight from a microwave beam.[5]
In 1973, Fred Militky and Heino Brditschka converted an HB-3 to an electric aircraft. Heino flew it for 14 minutes that same year.[6]
In 2007 the non-profit CAFE Foundation held the first Electric Aircraft Symposium in San Francisco.[7]
In 2009, a team from the Turin Polytechnic University made a conversion of a Pioneer Alpi 300. It flew 250 km/h for 14 minutes.[8]
By 2011 the use of electric power for aircraft was gaining momentum. At AirVenture in that year the Electric Aircraft World Symposium was held and attracted wide attention. It was sponsored by GE Aviation and included presentations by US Air Force, NASA, Sikorsky Aircraft, Argonne National Labs and the US Federal Aviation Administration.[9]
The 27 lb (12 kg) unmanned AstroFlight Sunrise, the result of an ARPA contract, made the world's first solar-powered flight from Bicycle Lake, a dry lakebed on the Fort Irwin Military Reservation, on 4 November 1974. The improved Sunrise II flew on 27 September 1975 at Nellis AFB.[10][11][12]
The world’s first official flight in a solar powered, man carrying aircraft took place on April 29, 1979. The Mauro Solar Riser was built by Larry Mauro and was based on the UFM Easy Riser biplane hang glider. The aircraft used photovoltaic cells that produced 350 watts at 30 volts, which charged a Hughes 500 helicopter battery, which in turn powered the electric motor. The aircraft was capable of powering the motor for 3 to 5 minutes, following a 1.5-hour charge, enabling it to reach a gliding altitude.[13]
The Solar-Powered Aircraft Developments Solar One was designed by David Williams under the direction of Freddie To, an architect and member of the Kremer prize committee and produced by Solar-Powered Aircraft Developments. A motor-glider type aircraft originally built as a pedal powered airplane to attempt the Channel crossing, the airplane proved too heavy to be successfully powered by human power and was then converted to solar power,[14] using an electric motor driven by batteries that were charged before flight by a solar cell array on the wing.[15] The maiden flight of Solar One took place at Lasham Airfield; Hampshire on June 13, 1979, one day after Brian Allen had successfully pedalled the Gossamer Albatross across the English Channel.[16]
The Gossamer Penguin, a smaller version of the human powered Gossamer Albatross was completely solar powered. A second prototype, the Solar Challenger, flew 262 km (163 mi) from Paris to England.[17] On 7 July 1981, the aircraft, under solar-power, flew 163 miles from Cormeilles-en-Vexin Airport near Paris across the English Channel to RAF Manston near London, flying for 5:23. Designed by Dr. Paul MacCready the Solar Challenger set an altitude record of 14,300 feet.[18]
The human piloted Solair 1 was developed by Günther Rochelt and based on a Farner canard design.[2][19] It employed 2499 wing-mounted solar cells giving an output of between 1.8 kW (2 hp) and 2.2 kW (3 hp). The aircraft first flew at Unterwössen, Germany on 21 August 1983.[2] It flew for 5 hours and 41 minutes, "mostly on solar energy and also thermals".[2] The aircraft is now displayed at the German Museum in Munich.[19] The newly developed piloted Solair II made its first flight in May 1998 and further test flights that summer but the propulsion system overheated too fast.[19] Development stopped when Günther Rochelt suddenly died in September 1998.
NASA's Pathfinder and Helios were a series of solar and fuel cell system-powered unmanned aircraft. AeroVironment, Inc. developed the vehicle under NASA's Environmental Research Aircraft and Sensor Technology program.[20][21]
In 1990 the solar powered airplane Sunseeker successfully flew across the USA, piloted by Eric Raymond.[22] It used a small battery charged by solar cells on the wing to drive a propeller for takeoff, and then flew on direct solar power and took advantage of soaring conditions when possible.[23]
The Sunseeker II, built in 2002, was updated in 2005-2006 with a more powerful motor, larger wing, lithium battery packs and updated control electronics.[24] As of Dec, 2008 it was the only manned solar powered airplane in flying condition and is operated regularly by Solar Flight.[23] In 2009 it became the first solar-powered aircraft to cross the Alps, 99 years after the first crossing of the Alps by an aircraft.[25]
China's first solar powered aircraft "Soaring" was designed and built by Danny H. Y. Li and Zhao Yong in 1992. The body and wings are hand-built predominantly of carbon fiber, Kevlar and wood. The design uses winglets to increase the effective wing span and reduce induced drag.[26][27]
The German solar powered aircraft "Icaré II" was designed and built by the institute of aircraft design (Institut für Flugzeugbau) of the University of Stuttgart in 1996. The leader of the project and often pilot of the aircraft is Rudolf Voit-Nitschmann the head of the institute. The design won the Berblinger prize in 1996, the EAA Special Achievement Award in Oshkosh, the Golden Daidalos Medal of the German Aeroclub and the OSTIV-Prize in France in 1997.[28]
Built by Lange Flugzeugbau GmbH, the LF20 [29] was a heavily modified DG800. First flown in 07.05.1999, the aircraft was used as a flying testbed and technology demonstrator. Powered by NiMh cells and using the same EA42 propulsion system as the later Antares 20E, the LF20 could climb 1725 m on one charge.
The Antares 20E is an electric, self-launching sailplane with a 42-kW DC/DC brushless motor and lithium-ion batteries. It can climb up to 3,000 meters with fully charged cells.[30] The first flight was in 2003. The Antares 20E was the first aircraft with an electric propulsion system to obtain a certificate of airworthiness. The same goes for the propulsion system (EA 42). The aircraft is currently in series production with more than 50 aircraft delivered. In 2011 the aircraft won the 2011 Berblinger competition,[31] an ambitious aerial challenge for “green” aircraft.
In 2005 Alan Cocconi, who founded the California (USA) electric-propulsion research company AC Propulsion, flew an unmanned airplane for 48 hours non-stop, propelled entirely by solar energy. This was the first such around-the-clock flight, on energy stored in the batteries mounted on the plane.[32]
The first short-hop (350m) test flight of the Solar Impulse prototype was made on 3 December 2009.[33]
In its present configuration it has a wingspan of 210 ft (64 m), weighs 3,500 lb (1,588 kg) and is powered by four 10-horsepower (7 kW) electric motors. The aircraft has over 11,000 solar cells on its wings and horizontal stabilizer. Power from the solar cells is stored in lithium polymer batteries and used to drive 3.5-metre (11 ft) propellers turning at a speed of 200–400 rpm. Take-off speed is 19 knots (35 km/h) and cruising speed is 60 kn (111 km/h).[34][35]
The aircraft had its first high flight on 7 April 2010, when it flew to an altitude of 1,200 meters (3,937 feet) in a 1.5-hour flight on battery power alone. The Solar Impulse team is planning to use the aircraft to circumnavigate the globe in 2012.[36]
The aircraft first flew on purely solar power, charging its batteries in flight, on 28 May 2010[37]
On 8 July 2010 it completed the first manned 24-hour flight completely powered by solar power.[38][39][40]
The Association pour la Promotion des Aéronefs à Motorisation Électrique (APAME) (English: Association for the Promotion of Electric Powered Aircraft) first flew its Electra electric-powered open-cockpit airplane at 1150 hrs (local) on Sunday, 23 December 2007 at Aspres sur Buech airfield, Hautes Alpes, France. Test pilot Christian Vandamme flew the strut-equipped aircraft for 48 minutes, covering 50 km (31 mi). The Electra is powered by an 18-kW (24 hp) disk-brush electrical motor driven by a 47 kg (104 lb) lithium polymer battery power pack.[41][42]
Matsushita Electric Industrial Co. and undergraduates at the Tokyo Institute of Technology teamed up to build an aircraft powered by 160 AA battery cells and successfully flew it for a distance of 391 meters (1,283 ft) in July, 2006.[43]
The FCD (Fuel Cell Demonstrator) is a project led by Boeing that uses a Diamond HK-36 Super Dimona motor glider as a test bed for a fuel cell powered light airplane research project.[45]
Successful test flights took place in February and March 2008.[45]
Boeing's partners in the project are Intelligent Energy of Britain (fuel-cell); Diamond Aircraft of Austria (Airframe); Spanish Sener (control system); Spanish Aerlyper (integrate motor with airframe); Advanced Technology Products, a U.S. company (motor, batteries, flight testing).[46]
The QinetiQ Zephyr is a lightweight solar-powered unmanned aerial vehicle engineered by the United Kingdom defence firm, QinetiQ. As of 23 July 2010 it holds the endurance record for an unmanned aerial vehicle of over 2 weeks (336 hours).[47]
It is of carbon fiber-reinforced polymer construction, the 2010 version weighing 50 kg (110 lb)[48] (the 2008 version weighed 30 kg (66 lb)) with a span of 22.5 metres[48] (the 2008 version had 18 metres (59 feet)). It uses sunlight to charge lithium-sulphur batteries during the day, which power the aircraft at night. The aircraft has been designed for use in observation and communications relay.[49]
The 2008 Zephyr version flew for 82 hours, reaching 61,000 foot in altitude in July 2008, the then unofficial world record for the longest duration unmanned flight. In July 2010 the 2010 version of the Zephyr made a world record unmanned aerial vehicle endurance flight of 336 hours, 22 minutes and 8 seconds (more than two weeks) and also set an altitude record of 70,000 feet.[50][51]
The SkySpark is a joint project of engineering company DigiSky and Polytechnic University of Turin. The two-seat Pioneer Alpi 300 has a 75 kW (101 hp) brushless electric motor powered by lithium polymer batteries. The aircraft achieved a world record of 250 km/h (155 mph) for a human-carrying electric aircraft on 12 June 2009.[52][53]
The Green Pioneer solar powered aircraft research programme was announced at the 4th China International Aviation and Aerospace Exhibition in 2002. The experimental programme was intended to provide research data for future Chinese solar powered aircraft. The programme was run by New Concept Aircraft (Zhuhai), the China Aviation Industry Development Research Center, and China Academy of Space Technology. The project leader and chief designer was Danny H. Y. Li.[54][55]
In June 2010 European aerospace company EADS unveiled an electric version of the 1970s vintage Colomban Cri-cri ultralight aircraft powered by four electric engines. The Cri-Cri will have lithium batteries and will be able to fly for 30 minutes at 60 kn (111 km/h) or 15 minutes of aerobatics at speeds up to 135 kn (250 km/h), with a climb rate of 1,000 feet per minute. The aircraft is a demonstrator for future technology, as Jean Botti, EADS's chief technical officer explained: "The Cri-Cri is a low-cost test bed for system integration of electrical technologies in support of projects like our hybrid propulsion concept for helicopters." The Cri-Cri first flew on 2 September 2010 at Le Bourget airport near Paris.[56][57]
The battery powered e-Genius was designed and built by the Institute of Aircraft Design (Institut für Flugzeugbau) of the University of Stuttgart Germany for the 10–17 July 2011 Green Flight Challenge in Santa Rosa, California. The design has similarities to their earlier solar powered aircraft Icaré II and seems to share most of the components with the fuel-cell powered Hydrogenius. The aircraft is a converted motorglider and uses a tail-mounted 80 hp (60 kW) electric motor. The e-Genius performed its first 20 minute flight on 25 May 2011. In July 2011 the aircraft flew for over two hours between two points near Mindelheim, Germany, at an average speed of more than 100 mph (161 km/h).[58][59][60]
The ENFICA-FC is a project of the European Commission, to study and demonstrate an all-electric aircraft with fuel-cells as the main or auxiliary power system. During the three year project, a fuel-cell based power system was designed and flown in a Rapid 200FC ultralight aircraft.[61]
The Puffin is a proposed hover-capable, electric-powered, low-noise, personal, vertical takeoff and landing (VTOL) technology-concept, proprotor aircraft. It would be capable of flying a single person at a speed of 150 miles per hour. Range is expected to be less than 50 miles with initial battery technology. The design has a 13.5 foot wingspan and stands 12 feet tall on the ground in its take-off or landing configuration.[62]
As of January 2010[update], a one third–size, hover-capable Puffin demonstrator was planned for March 2010. Future designs might incorporate additional rotors to provide redundant systems.[63]
As of August 2010[update], the one-third scale model of the Puffin was on display at the NASA Langley campus for filming for the Discovery network series “Dean of Invention.” The Puffin simulator was also demonstrated. The Puffin will appear in the eighth and final episode of the show.[64]
In July 2011 Pipistrel unveiled their Taurus G4 dual fuselage, four seat, single engine experimental aircraft that demonstrated the equivalent of 400 passenger miles per gallon efficiency. The aircraft joins two sailplane fuselages, with two seats each, with a single tractor configuration electric motor mounted between the fuselages. The aircraft carries 1,100 lb (499 kg) of Lithium polymer batteries. The aircraft has a 75 ft (22.9 m) wing and has a gross take-off weight of 3,300 lb (1,497 kg), making it the heaviest manned electric-powered aircraft built to date. It has a glide ratio of over 30:1 at 100 mph (161 km/h). The G4 first flew on 12 August 2011 and won the NASA Green Flight Challenge on 3 October 2011.[65][66][67]
On 13 April 2011, during the Aero Friedrischafen show, the Luxembourg Special Aerotechnics MC30E proof-of-concept aircraft[68] set a record for electric aircraft of 135 km/h (73 kn) over a return 15 km (8 nmi) circuit in the FAI RAL1E ID 16214 category. This aircraft was later retrofitted with a more efficient engine, in order to pursue further records in 2011.[69]
In 2011 Ultraflight Lazair designer Dale Kramer introduced an experimental electric-powered Lazair on an amphibious mono-float, with outrigger floats at AirVenture. The aircraft is powered by twin Bevirt JM1 Joby model aircraft powerplants and dual 16 cell 4 amp-hour battery packs that produce 63 volts, mounted in the the wings. The aircraft won Antique Ultralight Champion and Best Ultralight Amphibian at AirVenture. The aircraft is an experimental project and no production is planned.[70]
The electric Sikorsky S-300 of the Project Firely is one of the first electric rotorcraft.[71]
Several other electric aircraft are now being created for the Green Flight Challenge. These include:
The first commercially available production electric aircraft was the Alisport Silent Club self-launching sailplane. It was first tested in 1997. It is optionally driven by a 13 kW (17 hp) DC electric motor running on 40 kg (88 lb) of batteries that store 1.4 kWh of energy.[72]
The Air Energy AE-1 Silent came on the market in 1998.
In April 2007 the Electric Aircraft Corporation began offering complete electric ultralights and engine kits under the ElectraFlyer brand name, to convert existing ultralight aircraft to electric power, in what is the first commercial offering of an electric aircraft.
The 18 hp (13 kW) engine package weighs 26 lbs and an efficiency of 90% is claimed by the company. The battery consists of two lithium-polymer battery packs which provides 1.5 hours of flying in the trike application.[73][74]
In January 2008 the company introduced their new ElectraFlyer-C at the Sebring Light Sport Aircraft Show. This aircraft is a converted Monnett Moni motor glider equipped with an 18-hp electric motor, regenerative-braking-capable controller package and two lithium polymer battery packs. The engine weighs 29 lbs and the battery packs weigh 78 lbs total. The aircraft has a climb rate of 500 ft/min, cruise of 70 mph and an endurance of 90 minutes. It is capable of being recharged from a 110-volt source in six hours or from a 220 volt source in two hours. The aircraft began flying in May 2008 and was demonstrated before the crowds on August 2 at AirVenture 2008.[75]
In April 2009 the ElectraFlyer-C prototype was offered for sale on eBay. The designer intends to use the funds from the sale, plus a Lindbergh Foundation grant of $10,580 to complete two-place design that will eventually qualify for Light-sport aircraft status. The new design will incorporate composite construction, detachable wingtips to aid storage and will be powered by a 50 hp (37 kW) electric motor. Its design goals include a 28:1 glide ratio and a cruise speed of 80 mph (129 km/h) for two hours.[76]
Electraflyer president Randall Fishman announced in April 2010 that the company's latest model, the Electraflyer-X, would fly in May or June 2010. The aircraft will be a two-seater and will utilize a new 20 hp (15 kW) single rotor electric powerplant. Fishman is also developing 40 hp (30 kW) two-rotor and 60 hp (45 kW) three rotor engine designs.[77]
During AirVenture 2007 Sonex Aircraft announced that they are working on a series of alternate power initiatives, including an electric-powered aircraft. The electric powered Waiex motor glider was first flown in December 2010 and is powered by a 54 kW (72 hp) brushless DC electric motor, managed by a newly designed controller. Power is from a collection of 14.5 kW-hour lithium polymer batteries, giving the aircraft an endurance of one hour at low-speed cruise or 15 minutes of aerobatics.[78][79] This power system is being developed for the Sonex Electric Sport Aircraft, which will be available as a kit.[80]
A new Chinese aircraft was announced in 2009. The Yuneec International E430 is a two seat, V tailed, composite aircraft with a high-aspect ratio wing. Take-off speed is 40 mph and top speed is 93 mph. The aircraft is being developed as a homebuilt aircraft for the US market.[34][81]
The prototype E430 was displayed at EAA AirVenture Oshkosh in July 2009, by which time it had flown over 22 hours. The company claims that the battery packs have an expected lifespan of 1500 hours and cost US$7000 each, with the aircraft carrying 3-5 battery packs, giving two to two and half hours' endurance. The batteries can be recharged in 3 hours. The company projects that by the time the first customers require replacement battery packs that improved and less expensive ones will be available. Projected price for a commercially available light sport aircraft production version of the E430 is US$89,000.[82]
The e-Spyder is an electric-powered version of the Flightstar Spyder ultralight, developed by Flightstar Sportplanes president Tom Peghiny of South Woodstock, Connecticut, USA in cooperation with electric engine manufacturer Yuneec. The aircraft replaces the Spyder's two-stroke engine with a Yuneec 20 kW (27 hp) electric motor and two 28 lb (13 kg) lithium-polymer battery packs which provide a 40 minute endurance. The aircraft was exhibited at EAA AirVenture Oshkosh in July 2009 and is intended as a commercially available kit plane, forecast to be available for under US$25,000.[81][83][84]
The Lange Antares 20E is a self-launching motor glider with a 42-kW electric motor and SAFT VL 41M lithium-ion batteries. The motor actuates 2-blade fixed pitch propeller. It can climb up to 3,000 meters with fully charged cells. After launch it can function as a conventional, though heavy, glider. As of January 2010[update], over 50 had been built.[85]
Icaro 2000 Trike is a single-seat ultralight trike, with a conventional hang glider and the Flytec HPD 10 10 kW (13 hp) engine, developed by Manfred Ruhmer.[86]
The Schempp-Hirth Flugzeugbau Arcus-E was built in 2010. It was inspired by the Lange Aviation Antares 20E.[87]
In July 2010 Cessna announced it was developing an electrically powered Cessna 172 as a proof-of-concept in partnership with Bye Energy. Cessna CEO Jack Pelton stated that the project reflects "encouraging news for the future of mainstream general aviation." Pelton pointed out "the electric power plant offers significant benefits, but there are significant challenges to get there."[88][89]
The Elektra One is a development of a commercial electric aircraft design by PC-Aero of Germany. The single seat composite aircraft had its first flight in early 2011.[90] The Elektra One is powered by a 21 hp (16 kW) electric motor and is expected to have an endurance of three hours, with a 100 mph (161 km/h) top speed.[91]
The company is planning a whole line of aircraft including a version of the Elektra One with longer wings and built-in solar panels and an aerobatic version with double Elektra One's power and airframe strength. The company is also planning two and four seat developments.[91]
First made available commercially in February 2011, the Taurus Electro G2 is a two-seat self-launching sailplane. The 40 kW (54 hp) engine powers the aircraft from internally mounted lithium batteries for a 17-minute climb, after which the engine is retracted and the aircraft then soars as a sailplane. In April 2011 the Taurus won the 2011 Lindbergh Electric Aircraft Prize for "best electric aircraft" at the Aero show held in Friedrichshafen, Germany.[92][93]
A design concept has been put forward for soaring-type aircraft called regenerative soaring. In this approach, a propeller, using symmetrical blade sections, would be used as a turbine to recharge stored energy when the aircraft encounters an updraft.[94] At high altitudes, the energy available from vertical atmospheric motion within a thermal can exceed available solar power by a factor of ten or more.[94]
Recently proposed electric aircraft concepts for the future, feature unconventional and rather radical propulsion systems such as distributed propulsion technology.[95] Turboelectric power transfer in these propulsion arrangements contribute to energy conversation and feasible electric aircraft systems. Despite the aforementioned benefits, future electric aircraft concepts are also faced with a number of notable challenges[96] that are currently addressed by analysis tools such as ELECTERA. ELECTERA is a novel techno economic risk analysis scheme for future electric aircraft.[97] This scheme is proposed for initial design assessments of novel electric aircraft concepts at preliminary design stages.
Another proposed electric aircraft concept is the EADS VoltAir. It could be made within 25 years and features liquid nitrogen cooling for the engine.[98]
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