Full-Spectrum Solar-Generated Hydrogen

Osaka University researchers have created a new material based on gold and black phosphorus to produce clean hydrogen fuel using the full spectrum of sunlight.  Most solar apparatus used in “water splitting” rely on materials such as titanium dioxide.  These are limited to obtaining energy from the ultraviolet (UV) part of the solar spectrum, however.  The rest of the spectrum is wasted.

Osaka’s team “developed a material to harvest a broader spectrum of sunlight,” using a three-part composite.  The different parts maximize absorption of light and enhance the efficiency of the unit for water splitting.  The core, a “traditional” semiconductor of lanthanum titanium oxide (LTO) is coated with tiny nanoparticle specks of gold.  The gold-covered LTO is then mixed with ultrathin sheets of black phosphorus (BP), which acts as a light absorber.

LTO, BP and gold combine to produce greater excitation on solar-collecting surface. Electron microscope images of visible-NIR (near infrared) light responsive photocatalyst composed with black phosphorous (BP), lanthanum titanate (LA2Ti2O7, LTO), and gold nanoparticles (Au)

Bonding the gold-coated LTO to the BP layer makes a serendipitous combination.  Team leader Tetsuro Majima says. “BP is a wonderful material for solar applications because we can tune the frequency of light just by varying its thickness, from ultrathin to bulk. This allows our new material to absorb visible and even near-infrared light, which we could never achieve with LTO alone.”

The report continues, “By absorbing this broad sweep of energy, BP is stimulated to release electrons, which are then conducted to the gold nanoparticles coating the LTO. Gold nanoparticles also absorb visible light, causing some of its own electrons to be jolted out. The free electrons in both BP and gold nanoparticles are then transferred into the LTO semiconductor, where they act as an electric current for water splitting.”

Absorbing a broader spectrum of light and conducting electrons more efficiently, the “unique interface” between BP and LTO results in a material 60 times more active than LTO along.

Majima says, “By efficiently harvesting solar energy to generate clean fuel, this material could help to clean up the environment.  Moreover, we hope our study of the mechanism will spur new advances in photocatalyst technology.”

The abstract for their paper can be found on the web site for the Angewandte Chemie International Edition, 2017.
Abstract: Efficient utilization of solar energy is a high-priority target and the search for suitable materials as photocatalysts that not only can harvest the broad wavelength of solar light, from UV to near-infrared (NIR) region, but also can achieve high and efficient solar-to-hydrogen conversion is one of the most challenging missions.Herein, using Au/La2Ti2O7 (BP-Au/LTO) sensitized with black phosphorus (BP), a broadband solar response photocatalyst was designed and used as efficient photocatalyst for H2 production. The optimum H2 production rates of BP-Au/LTO were about 0.74 and 0.30 mmol g@1h@1 at wavelengths longer than 420 nm and 780 nm, respectively. The broad absorption of BP and plasmonic Au contribute to the enhanced photocatalytic activity in the visible and NIR light regions.Time-resolved diffuse reflectance spectroscopy revealed efficient interfacial electron transfer from excited BP and Au to LTO.  which is in accordance with the observed high photoactivities.

Mingshan Zhu, Xiaoyan Cai, Mamoru Fujitsuka, Junying Zhang, Tetsuro Majima; “Au/La2Ti2O7 Nanostructures Sensitized with Black Phosphorus for Plasmon-Enhanced Photocatalytic Hydrogen Production in Visible and Near-Infrared Light,” Angewandte Chemie International Edition, 2017

Their findings would seem to have implications for all solar collectors, with greater efficiency possible for solar cells.


Dubai, already having penned a similar agreement with China’s eHang, will start test runs of autonomous air taxis in 2017 with the Volocopter.

Volocopter’s Eventful Year

Volocopter has had an eventful year, introducing its latest model, the 2X, at this year’s Friedrichshafen Aero E-Flight Expo and opening its new corporate headquarters.  Now, it looks forward to demonstrating its craft in regular service.  e-Volo writes, “Our vision becomes reality: Dubai’s government “Roads and Transport Authority” (RTA) has signed an agreement with us regarding the regular test mode of Autonomous Air Taxis (AAT) in the emirate. The test will start in the fourth quarter of 2017, and the project has been scheduled to run for five years.”

The Volocopter 2X, according to its makers, is simply foolproof, having 100 microprocessors and a large number of sensors helping maintain vehicle stability, even in turbulence.  Volocopter has demonstrated hands-free flight on several occasions.

Stability is part of its safety factor, and 18 rotors with compensating mechanisms ensure that the Volocopter can maintain flight even with several motors out of commission.  Nine battery packs and controllers allow continued operation even with the loss of one.  If all else fails, a ballistic parachute (“for incorrigible pessimists”) enables the occupants’ descent “to the ground, very gently, still securely seated in the aircraft.”

Operational and safety factors for Volocopter 2X

Simplicity and safety complement the green operation its makers claim for Volocopter, looking beyond its current state of pollution-free flight to improved batteries, longer range and increased utility.  All these factors will get a good workout in the skies between skyscrapers.  E-Volo looks forward to the challenge.  “Now this technology will experience further testing in Dubai under extreme climatic conditions. We see Dubai as the pioneer for a huge evolving market and are convinced that many other metropolitan areas will follow.”

The Verge notes that Dubai is, “A testing ground for some of the transportation world’s more futuristic and outlandish ideas.”  Tests start in the fourth quarter of 2017, and are scheduled to last five years.  Alexander Zosel, co-founder of Volocopter, said, “We are very grateful and proud that the RTA has selected us as their partner after rigorous testing,” adding that his company’s “stringent safety standards” were one of the reasons for that selection.

Volocopter’s prototype VC200 took its first crewed flight last year. And at Europe’s largest general aviation trade fair earlier this year, the company revealed its first production model: the 2X. It has a maximum range of 17 miles when flying at a speed of 43 mph. Its maximum flight time is 27 minutes at an optimal cruise speed of 31 mph, but if range were no concern, the 2X can fly at a maximum speed of 62 mph.

Volocopter 2X and the eHang 184

The Verge elaborated that, “Volocopter won’t be the only flying taxi service buzzing through Dubai’s airspace. RTA also recently struck a deal with the Chinese drone company Ehang to test its single-person quadcopter as a transit alternative. Uber is also in talks with the emirate city to publicly demonstrate its own flying taxi service in 2020. And if flying through the air in an autonomous drone isn’t your bag, perhaps you’d be more interested in tube-based travel: Dubai is working with LA-based startup Hyperloop One to build the world’s first passenger-ready hyperloop.”

The English Publication, The Engineer, gives a few technical points.  “Designed and built in Germany, the Volocopter can fly autonomously using 18 individual rotors powered by nine swappable batteries. The aircraft has a top speed of 100km/h [62 mph] and maximum flight time of around 30 minutes.”  If all goes well, RTA looks forward to seeing a quarter of all trips in Dubai carried out by autonomous transport by 2030.

His Excellency Mattar Al Tayer, Director-General and Chairman of the Board of Executive Directors of RTA, explains RTA’s role in the tests. “The RTA is working with the Dubai Civil Aviation Authority to develop the legislative and operational guidelines, define specifications and standards applicable to operators in the emirate such that these legislations will be ready. It is noteworthy that the operational and legislative structures will be the first of their kind worldwide.”

Earlier this year, Chinese company eHang signed an agreement with the RTA to begin testing their single-seat 184 as an on-call aerial taxi.  Since the two vehicles carry different payloads and have similar vertical takeoff and landing capabilities, comparisons will doubtless be made, but both will have to demonstrate reliable operation under the Dubai sun.

And on the Waterfront?

Kittyhawk Aero recently demonstrated its Flyer for an appreciative San Francisco audience.  It made your editor wonder if Kittyhawk could provide low-altitude commutes to one’s private island four kilometers from the central city, while e-Volo and eHang stage a friendly competition above.  The “select few” who prosper in this rich city will probably jump on board.  Warning: a real-estate pitch follows – but also provides a glimpse of what it would be like to fly over and through this astounding city.


Aviation Week reports from the Paris Air Show on a “disruptive” entry in electric aviation.  Eviation, founded by Omer Bar Yohai, is primed to deliver a change in transportation as we know it.  Yohai says, “The dominant solutions available today are deeply flawed and demand disruption.”

The company’s promotional video only hints at the company’s intentions.  Their vision statement on their web site, though, indicates a skyward aspiration: “Making electric aviation the fast, competitive and clean answer to on-demand mobility of people and goods.”  Aviation Week’s Noam Eshel quotes Bar Yohai as saying, “We design, test and build the tools that will enable future of regional transit by air, changing consumers’ perception of both distance and time.  Five years from now, EViation is set to enable cheap, high-speed, sustainable and convenient regional commuting using light aircraft, tightly integrated with on-demand ground transport solutions. Currently, a sub-scale prototype is undergoing testing and risk-reduction evaluations. The company expects its first firm orders from its lead customer next year.”

EViation has three aircraft ready to provide that disruption:

Alice, a six- to nine-seat aircraft will cruise at 10,000 feet with a range of up to 350 miles at a speed of 220 knots (253 mph).  Optimized for air taxi operations, the aircraft will sell for about $1.4 million.

Eviation’s all-electric aircraft takes the spotlight at the Paris Air Show (PRNewsfoto/Eviation Aircraft Ltd.)

Alice ER, the “luxury” model, will cost $1.9 million, but will carry six lucky passengers at 28,000 feet in a pressurized cabin, and travel up to 800 miles at a speed of 250 knots (287.5 mph). It will be able to “fly from any airstrip capable of operating general aviation.”

According to EViation, “Operators will benefit from the lower energy and reduced maintenance costs, while low noise and zero emissions enable such electrically powered planes to operate from landing strips close to urban areas.”

Working within a general aviation framework will enable Bar Yohai’s vision to serve a broad market.  “With this aircraft, air taxi operators will be able to serve customers on-demand travel [to] the nearest landing strip for the price of a train ticket.”

EViation says its can incorporate autonomous flight controls that can be integrated into current regulatory frameworks.  Bar Yohai says. “We became part of NASA’s on-demand mobility program and GAMA (General Aviation Manufacturers Association) and the FAA electric aviation committees.”

EViation Orca at Paris Air Show displays same configuration as Alice, but smaller size

On a smaller scale, Orca is an unmanned variant, able to carry a maximum gross weight of 250 kilograms (550 pounds) for more than 497 miles at a cruising speed of 144 knots (165.6 mph). It can be remain airborne for more than eight hours, carrying a payload of 50 kilograms (110 pounds). A true VSTOL (very short takeoff and landing) craft, it can operate from a 99-foot long runway.

All the craft rely on three fundamental technologies for their success: propulsion, airframe and energy.  Aviation Week quotes Bar Yohai explaining, “Our solution is electric from conception, taking a holistic approach to aircraft design, allowing us to fully optimize the benefits of electric aviation.”  Electric propulsion gives “design freedom” with selective placement of power units, redundancy and “benefits to benefits to airflow, cooling, noise, and safety.”  Distributed propulsion enables “trimming and steering with propulsion adjustments.”  Coupled with airframes excelling in speed and efficiency, “we’re literally pushing the envelope of efficient elegance.”  Modern design techniques allow “rapid methods of ideation and validation.”

Advertisement showing potential landing spot for Orca, capable of touching down in 99 feet

Most interesting for followers of electric aircraft, EViation has turned to Israel’s Phinergy Ltd’s aluminum air battery, which on the company’s web site claims eight kilowatt-hours per kilogram of aluminum.  EViation says that the battery is “coupled with a high power rechargeable battery buffer, and managed by a clever mission specific power analytic algorithm.   This unique technology provides high energy density “at a cost that beats gas, and with zero emissions.”  Their web site claims 1,000 kilometer (620 mile) range for electric cars (1,600 kilometers or 992 miles in the video)  powered by Phinergy systems and three-to-five-minute recharging.  Phinergy also claims relatively easy transition to an infrastructure that could support the batteries.

Phinergy’s four-year-old video shows a battery pack that looks and acts like a fuel cell.  It uses fresh (presumably distilled) water to recharge.

EViation has partnered with Magnaghi Aeronautica SpA, the manufacturer of the SkyAero aircraft, and FBM, an Israeli producer of carbon-based composites, which manufactured the all-composite prototypes.  They’ve also teamed with Leonardo and Dassault Systems to pursue unmanned variants of the (nine-passenger) design, with up to a gross takeoff weight of five tons.   They revealed the aircraft and the partnerships at this week’s Paris Air Show.

Attendees at the CAFE Foundation’s Electric Aircraft Symposium will be able to hear a presentation by Omer Bar-Yohay, Co-Founder and CEO, Eviation Aircraft Ltd. detailing the company and its unique electric aircraft.


Had the residents of Landshut, a 13th-century city in Lower Bavaria, chanced to look up at the right time over the last few weeks, they might have glimpsed a bright yellow shape looking back at them.  Calin Gologan’s latest Elektra One Solar carries a suite of cameras that can transmit 2D movies in 4K resolution to a ground station up to 40 kilometers (25 miles) away.  Through sophisticated software, the images can be translated into 3D maps with a resolution of five centimeters (just under two inches), the primary mission of the flights.

Elektra One over the streets of Landshut, Bavaria

Partner ViaLight, a 2009 spin-off of the DLR (the German Aerospace Center), provided the hardware and software that allows up to 100 Gbps (gigabits per second) data transmission speed, and thus enables such high resolution for the aerial images.  The system can also transmit “Big Data,” using the high-speed optical links.

According to Elektra Solar GmbH, a merger of the companies PC-Aero GmbH and Elektra UAS GmbH, the project “successfully performed many flights with the Elektra One aircraft over the old town of Landshut for 3D high-resolution mapping.”  Flying autonomously according to a “very exact preprogrammed path,” the essentially noiseless, pollution-free flyovers delivered a series of stunning images.

Elektra One with pod containing cameras, communications gear

Such images require special communications systems.  ViaLight explains that it “Offers laser communication solutions allowing high data rate and long distance wireless data transmission between moving objects for terrestrial, airborne and space applications. Laser communication can be thought of as the optical fiber for the skies and ViaLight’s products provide backbone connectivity to link aircraft, unmanned aerial vehicles (UAVs), high altitude platforms (HAPs), satellites and their respective ground stations.”

Pre-programmed route over Landshut

Calin says the “Remote Eye” concept enables low-cost flight over towns at low altitudes and will be applied to the Elektra Two Solar, “the future of intelligent surveillance,” for high-altitude flights.  Significant growth in the airplanes’ capabilities allows even grander future plans.

Ground station tracking Elektra’s progress

According to Elektra Solar GmbH, “The latest version of Elektra One, named Elektra One Solar has a wing span of 13 m, a glide ratio of more than 30 and is equipped with solar cells on the wing surface as a range extender. With the support of Elektra UAS, the second partner of the merger (and spinoff from DLR’s Robotics and Mechatronics Center – RMC), these airplanes are now prepared for the test and demonstration of optionally-piloted and unmanned operation, using advanced autopilot and remote ground control station technologies. “

High-resolution image showing grid lines on the water

We’ve written about Elektra Two Solar recently, and Raphael Domjan’s ambitious plans for high-altitude tourism.  He and Calin continue to demonstrate their ability to fulfill their lofty ambitions, and we wish them continued success.


Batteries Following Roads Less Taken

When you come to a fork in the road, take it.  Yogi Berra

Technology and new products continue to enhance the development and realization of electric and solar aircraft.  Two approaches to batteries, both of which explore roads less taken, have some promise for aircraft use.

Shine Some Light on It

What if your battery could be recharged just by exposing it to light?  A team of South Korean researchers, affiliated with UNIST (Ulsan National Institute of Science and Technology) has developed a single-unit, photo-rechargeable portable power source based on high-efficiency silicon solar cells and lithium-ion batteries (LIBs).  Rechargeable under solar or artificial light, the unit could power other electronic devices, “even in the absence of light.”

Professor Sang-Young Lee and Professor Kwanyoung Seo of Energy and Chemical Engineering at UNIST have presented a new class of monolithically integrated, portable PV–battery systems (SiPV–LIBs) based on miniaturized crystalline Si photovoltaics (c-Si PVs) and printed solid-state lithium-ion batteries (LIBs). Using a thin-film printing technique, the solid-state LIB is directly printed on the high-efficiency c-Si PV module.

Sequence of manufacturing and layers of finished product

Professor Lee says, “This device provides a solution to fix both the energy density problem of batteries and the energy storage concerns of solar cells. More importantly, batteries have relatively high power and energy densities under direct sunlight, which demonstrates its potential application as a solar-driven infinite energy conversion/storage system for use in electric vehicles and portable electronics.”

More compact than separate PVs or LIBs alone, the single unit “exhibits exceptional photo-electrochemical performance.” It can charge in less than two minutes with a  (photo-electric conversion/storage efficiency of 7.61 percent.

Fabricated from a solid-state LIB with a bipolar cell configuration directly on the aluminum (Al) electrode of a c-Si PV module through an in-series printing process.  The seamless arrangement acts simultaneously as a current collector of the LIB, and as an electrode for the rear-electrode type solar cells. This direct connection and single Si substrate allow the battery to be charged without the loss of energy.  It also allows simplified manufacturing of the device.

To test their solar cell/battery researchers inserted the SiPV–LIB device into a pre-cut credit card. They then drew connectors ton the back of the credit card using a commercial Ag pen (a kind of flux dispenser) to connect the SiPV–LIB device with an LED lamp, a smartphone, and an MP3 player.

Performance of credit card prototype

Under sunlight, The SiPV–LIB device charged in under two minutes, holding that charge even in 60°C (140°F) temperatures and at a low light intensity of 8 mW/cm2 (milliwatts per square centimeter), the light in a dimly-illuminated room.  This ability to hold a charge would allow such a material (considerably larger than a credit card) to be applied to top and bottom surfaces of wings, for instance.  Still in development, the device, if it could be expanded to larger applications, could be a significant material for vehicles of all types.

Professor Lee concludes, “The SiPV–LIB device presented herein shows great potential as a photo-rechargeable mobile power source that will play a pivotal role in the future era of ubiquitous electronics,”

Their paper, “Monolithically integrated, photo-rechargeable portable power sources based on miniaturized Si solar cells and printed solid-state lithium-ion batteries,” appears in the April issue of the journal, Energy and Environmental Science.

Fill It Up with Electrolytes

What if you could fill up your electric vehicle just as you pump gasoline into your fossil-fuel burner today?  Purdue researchers might have an “instantly rechargeable” method that is safe, affordable and environmentally friendly for recharging electric and hybrid vehicle batteries that anyone who tops up their own tank can perform.

The technique eliminates those lengthy recharging times and allows the use of existing infrastructure (slightly modified).  John Cushman, Purdue University distinguished professor of earth, atmospheric and planetary science and a professor of mathematics, has co-founded Ifbattery LLC, (IF-battery) to further develop and commercialize the technology.

Noting the growing sales of electric and hybrid vehicles, Cushman explains, “Current electric cars need convenient locations built for charging ports.  Eric Nauman, co-founder of Ifbattery and a Purdue professor of mechanical engineering, basic medical sciences and biomedical engineering, adds, “Designing and building enough of these recharging stations requires massive infrastructure development, which means the energy distribution and storage system is being rebuilt at tremendous cost to accommodate the need for continual local battery recharge.  Ifbattery is developing an energy storage system that would enable drivers to fill up their electric or hybrid vehicles with fluid electrolytes to re-energize spent battery fluids much like refueling their gas tanks.”

At this point, things depart the conventional fueling analogy.  Gasoline or Diesel fuel, consumed in the customer’s vehicle, fouls the atmosphere and doesn’t return to its point of origin.  In Purdue’s approach, “the spent battery fluids or electrolyte [would] be collected and taken to a solar farm, wind turbine installation or hydroelectric plant for re-charging.”

Cushman explains, “Instead of refining petroleum, the refiners would reprocess spent electrolytes and instead of dispensing gas, the fueling stations would dispense a water and ethanol or methanol solution as fluid electrolytes to power vehicles.”

The added step doesn’t seem to faze the co-founder.  “Users would be able to drop off the spent electrolytes at gas stations, which would then be sent in bulk to solar farms, wind turbine installations or hydroelectric plants for reconstitution or re-charging into the viable electrolyte and reused many times. It is believed that our technology could be nearly ‘drop-in’ ready for most of the underground piping system, rail and truck delivery system, gas stations and refineries.”

Professor John Cushman in his Purdue laboratory

Recharging stations would need to be centrally located in clusters of such refueling stations to make the two-way trip with the fluids economically feasible.  Perhaps local wind or solar farms could reduce the distances the fluids would travel.

Other flow batteries exist, according to Mike Mueterthies, Purdue doctoral teaching and research assistant in physics and the third co-founder of Ifbattery.  For instance, NanoFlowCell in Switzerland fields the Quant and Quantino cars fueled by two different types of salt water.  Mixing the two in a fuel cell generates electricity to run the cars’ motors, but some type of post processing still needs to take place after the cars have exhausted the energy potential in the water.

The Ifbattery system is unique, according to Meeterthies, in hot having a component that tends to be the Achilles heel of most flow batteries.  “…We are the first to remove membranes which reduces costs and extends battery life.”

Cushman enumerates other benefits of membrane-free batteries.  “Membrane fouling can limit the number of recharge cycles and is a known contributor to many battery fires.  Ifbattery’s components are safe enough to be stored in a family home, are stable enough to meet major production and distribution requirements and are cost effective.”

Ifbattery licensed part of the technology through the Purdue Research Foundation Office of Technology Commercialization and has developed patents of its own. The company is a member of the Purdue Startup Class of 2017.

Cushman presented the teams’ paper, “Redox reactions in immiscible-fluids in porous media — membraneless battery applications” at the recent International Society for Porous Media 9th International Conference in Rotterdam, Netherlands.


Long Hours of Droning On

Several different organizations are trying different ways to keep unmanned aerial vehicles, UAVs, up longer.  We’ll look at three recent efforts in long-endurance missions, each with a unique technological approach.

Wirth Research – Hydrogen Fuel Cell

Wirth Research is now constructing a new tilt rotor, Vertical Take Off and Landing (VTOL), hydrogen fuel cell powered, advanced terrain-mapping drone.  Carrying a payload of sensors and onboard data processing capabilities, the vehicle will be powered by a complete H2 storage, control and power system provided by HES of Singapore, a specialist in ultra-light hydrogen fuel cells.

Wirth VTOL UAV transitions to horizontal flight for rapid transit

The Wirth machine’s missions range from precision agriculture, to pipeline and cable inspection for utilities, surveillance and other security-related tasks, through to detection and monitoring support for ordnance clearance operations.  Combining the ability to carry a large payload and provide up to six-hour endurance in the VTOL configuration meant shifting from battery to hydrogen power.

HES Founder and CEO, Taras Wankewycz, said, “We are shifting gears from a 200Wh/kg lithium battery capability to a 700Wh/kg fuel cell energy density capability, one that would radically change the applicability of drones, such as long-distance delivery, large area inspections at faster speed and lower cost, and a reduced need for expensive high altitude sensor payloads.”

The company explains, “This UAS system can be adapted to carry and power a variety of sensors including stereo high-resolution gimbaled optical cameras, high-resolution infra-red sensors, LIDAR imagers and ground penetrating radar sensors.  The ability to carry and power such an extensive range of payloads makes this UAS technology ideal for a variety of industry sectors with multiple applications beyond its primary task of terrain mapping.”

Wirth has a great deal of experience applying computational fluid dynamics and manufacturing capabilities to race car development, architecture, commercial vehicles and the general automotive industry.  This experience enables Wirth to expedite new creations, moving from Technology Readiness Level (TRL) 3 to TRL 6 in under six months on this project.

U. S. Navy – Solar Energy

Researchers at the U.S. Naval Research Laboratory (NRL), Vehicle Research Section and Photovoltaic Section, building on the proven concept of autonomous cooperative soaring of unmanned aerial vehicles (UAVs).  The team investigates combining “autonomous soaring algorithms and solar photovoltaics for capturing energy from the environment to extend the endurance of an aircraft.”

Members of the ‘Solar-Soaring’ research flight crew (l-r) Dan Edwards and Trent Young holding the photovoltaic (PV) UAV based on the SBXC sailplane. Photo: U.S. Naval Research Laboratory

Dr. Dan Edwards, an aerospace engineer, explains, “NRL has twice flown our solar UAV (based on the SBXC sailplane) over 10 hours using a combination of solar photovoltaics and autonomous soaring as part of the ‘solar-soaring’ research program.  This research is investigating the value of combining autonomous soaring algorithms and solar photovoltaics for capturing energy from the environment to extend flight endurance and mission operations of an aircraft.”

A custom-built, drop-in photovoltaic array replaces the wing’s original non-solar center section. A power management and distribution system converts the power from the solar arrays into direct current (DC) voltage, which the electric motor can use for propulsion, or to recharge a “smart battery.”

The autonomous soaring software algorithm commands the aircraft to orbit in any nearby updrafts, very similar to soaring birds. To test the solar-only performance, the algorithm was disabled for the two solar flights.  The motor switches off automatically if thermals or upward wind gusts increase the airplane’s altitude along the pre-defined flight path, allowing “passive soaring.”

According to NavalToday.com, “The UAV equipped with solar wings incorporated PV (photo-voltaic) arrays from Alta Devices, Inc. It flew for 11 hours, 2 minutes on April 19, 2017. Takeoff occurred at 7:46 a.m., approximately an hour after sunrise, with the battery’s state of charge at 90 percent. Landing occurred at 6:48 p.m., approximately an hour before sunset, with the battery’s state of charge at 26 percent. Thermal activity was very weak and almost all of the flight was spent running the motor. Near solar noon, the solar array provided sufficient power to cruise on solar power alone.”

Edwards noted, “The experiments confirm significant endurance gains are possible by leveraging thermal updrafts and incident solar radiation, rather than ignoring these free sources of energy.  Future testing will focus on quantifying the trade space between improvements in solar cell efficiency and combining with autonomous soaring for improved solar-recharging.”

As background, the Navy has set some endurance records with drones before, flying a hydrogen fuel-cell-powered Ion Tiger in 2013 for over 48 hours.  Alan Cocconi flew “So Long” for 48 hours in 2008, the first two-day, two-night solar-powered flight.   QuinetiQ’s Zephyr managed an 83 hour, 37 minute record in 2008.  The solar-cells fed batteries on the solar-powered machines to allow flying at night.

Such long-endurance flights have obvious military applications for gathering continuous information, surveillance, and reconnaissance (ISR).  Persistence can pay off in uninterrupted views of disaster areas, or searches for lost hikers, for instance.

MIT – Sipping Gas

Jennifer Chu reports from MIT that a large multi-discipline team has created a long-wing-span drone that can carry 10 to 20 pounds of communications equipment at 15,000 feet – for up to five days.  At an all-up weight “just under” 150 pounds, the UAV’s five-horsepower gasoline engine can keep it aloft for up to five days.  That’s “longer than any gasoline-powered autonomous aircraft has remained in flight,” according to the researchers.

John Hansman, the T. Wilson Professor of Aeronautics and Astronautics; and Warren Hoburg, the Boeing Assistant Professor of Aeronautics and Astronautics, led the Beaver Works team, students in a two- or three-semester course to design, build and test their designs. The U. S. Air Force approached this group to design a long-duration UAV powered by solar energy.

After long study and analysis, the MIT team decided to go with a more traditional power source.  Professor Hansman explains, “[A solar vehicle] would work fine in the summer season, but in winter, particularly if you’re far from the equator, nights are longer, and there’s not as much sunlight during the day. So you have to carry more batteries, which adds weight and makes the plane bigger.  For the mission of disaster relief, this could only respond to disasters that occur in summer, at low latitude. That just doesn’t work.”

Using GPkit, Professor Hosburg’s vehicle optimization software tool, the team was able to examine “around 200 constraints and physical models simultaneously.  Team members determined that solar wouldn’t work for long-duration flights just anywhere in the world, they performed the same modeling for a gasoline-powered machine.  Their findings showed such a plane could “stay in flight for more than five days, at altitudes of 15,000 feet, in up to 94th-percentile winds, at any latitude.”

MIT Jungle Owl team holds 24-foot wingspan UAV

The team built a carbon-fiber, 24-foot wingspan realization in 2016, being careful to stay within the FAA’s 55-pound weight limit for drones.  It can be loaded with fuel and payloads to increase its weight to 150 pounds, though.   It’s also able to be dismantled and packed into a FedEx box and sent to disaster zones, presumably outside FAA jurisdiction.

Launched from a compact car, the prototype made a short flight proving its aerodynamic worth.

According to Hansman, “These vehicles could be used not only for disaster relief but also other missions, such as environmental monitoring. You might want to keep watch on wildfires or the outflow of a river.  I think it’s pretty clear that someone within a few years will manufacture a vehicle that will be a knockoff of this.”

This research was supported, in part, by MIT Lincoln Laboratory.

Summing Up

Research provides different configurations and different power systems to fulfill different missions.  With efficiency in mind, even the fossil-fuel powered versions can achieve long flights on the lowest use of resources.


Urs Villiger, with the assistance of, “A network of aviation specialists…under the leadership of Calin Gologan CFD Consultants,” crafted a sleek four-seater, the Traveler TR230.  That airplane, originally flown with an internal combustion engine, has apparently been recrafted as a hybrid craft.  Gologan, along with Dr. Volker Kassera, did the majority of the aircraft’s design.

First flown on December 4, 2015, the gas-powered Traveler was very much a fixed landing gear airplane, replete with wheel pants.  The large canister under the cowling and forward part of the fuselage is a so-called “Swiss muffler,” a great deal like a “glass-pack” used by American hot-rodders in the 1950’s.  It was developed by experimenters in Switzerland to comply with noise regulations.  The major background noise heard in the video is from a Diamond motorglider powered by a Rotax engine – indicating the effectiveness of the Swiss muffler.

According to electric-flight.eu, the “former entrepreneur and Hobbypilot is now devoting his entire leisure time to the development and construction of his future electric aircraft.”  He showed a large scale model at AERO 2017 and hopes to “present” the full-scale aircraft in 2018.

TR230 Traveler was constructed first as an IC-powered airplane

Originating with the Traveler TR230, developed by MSW Aviation with a “Kolbus engine,” according to electric-flight, it’s unclear if the new hybrid is a rebuild of the existing airframe or a completely new machine.  Regardless, the wheels are tucked inside and the configuration has s more streamlined nose, probably reserved for batteries to make up for the loss of the engine.

The TR 230’s lines are there, but a 220-kilowatt electric drive unit similar to the one mounted on the Votec Evolaris sets high on the vertical tail.  The drive weighs only 45 kilograms (99 pounds), still requiring a significant structure to hold it in place.  A speed reducer will turn a Mühlbauer five-blade propeller at a reasonable rate.  Makers say 400 kilograms (880 pounds) of batteries “should at least be sufficient for short domestic flights.”  Developers plan a future hybrid version with longer range.

A poster advertising Evolaris’ display at Aero shows both the Traveler Hybrid and the Votec Evolaris aerobatic plane, and includes a line for the EVO 230 kilowatt motor, for aircraft with takeoff weights up to two tons.  Evolaris is a spin-off from Berne University of Applied Sciences, and the two young mechanical engineers have worked two years on the development of their own electric drive systems, featured on both the aerobatic and hybrid craft. MSW supervised building the aircraft.

Electric hybrid version has retractable gear, tail-mounted motor and propeller

Partners include Brusa Elektronik AG, a maker of high-performance electric motors; Suter Racing AG, supporting the project in gear manufacturing, mechanical engineering and cooling technology; MT Propellers, noteworthy for its 90-percent market share in Europe and 30-percent share in America; Serto AG, specializing in cooling technology; and EAS, Experimental Aviation of Switzerland, helping people build and fly their own private airplanes.  Interestingly, the 530 member organization who are allowed supervision of the construction and maintenance of self-propelled aircraft, entrusted to them by the Federal Office of Civil Aviation (FOCA).

With a team showing such dedication and expertise, the Traveler Hybrid should be a significant milestone in Swiss and electric aircraft development.


P3 is a new and different type of consulting service for a new and different kind of industry – electric aviation.  Consulting businesses usually manage to help others manage fairly conventional and well-traveled projects, limiting their practice to advising on how to meet budget and project timelines.  These are valuable insights that can help technical gurus overcome business issues, or management teams understand new technology.

But what happens when a whole industry is exploring new paradigms, shaping new world views and delving into areas that did not exist a short time before?  One consulting firm that did not exist before 1996 is making inroads into that unexplored territory.  A spin-off from RWTH University in Aachen, Germany, P3 started with a quality management project at Daimler.  In quick order, the founder expanded the business into a global enterprise with over 3,000 consultants, engineers and entrepreneurs and more than 30 subsidiaries and locations, including Dallas, Detroit, greater New York, Greenville, Los Angeles and Montreal in North America.

When future flight doesn’t resemble the past, how do you press forward? The Fly™ Citycopter has a control stick and a pair of cup-holders, but all else is not terribly familiar in this conceptual rendering

Sascha Kempf, a project manager for P3, explains part of the firm’s growth.  “The concept of P3 is not only to advise customers, but to support them. This means P3 is a hybrid of a management consultancy and an engineering service company and they work with their customers all the way from strategy to implementation, which is a rare combination. As a technology driven organization with a German engineering background, P3 customers mostly consist of large corporations as well as small- and medium-sized enterprises and start-ups in the aviation, automotive, energy and telecommunications sector. “

He explains the company’s relative lack of name recognition is an acceptable part of its approach.  “Probably you have never heard of them and that is totally fine. The success of the company is definitely not due to extensive marketing activities, as new projects usually develop out of direct customer recommendations and marketing has long been kept to a minimum. Co-Founder and CEO Christoph Theis jokes, that “people who apply at P3 already passed the first test, because they found us.” The diverse company portfolio also includes products like for example an innovative fire extinguisher or a cockpit electronic flight bag mount certified for aerospace applications.”

Analogies to automotive experience aren’t always helpful – especially as cars change dramatically

The multiple disciplines and expertise presented by project teams enable them to solve complex problems with multiple technology roots.  “The team consists of mechanical and aerospace engineers, operations and marketing professionals, software and communication specialists, electrical and energy engineers, management consultants and project managers. Thomas Prefi, Co-Founder and CEO says: ‘For the complex and fast-paced technology projects of the future, cross-disciplinary competence and expert-generalists are key to success.’”

Sascha explains how this works for aeronautical projects.  “The P3 E-Flying team concentrates on 3 major markets, which are VTOLs and the on-demand mobility concept, thin-haul commuter aircraft for short-range applications and hybrid-electric airliner and transport aircraft. Additionally, P3 E-Flying provides technology consulting services (battery, power electronics, e-motors, cost analysis), project- and program management support and customer-specific engineering solutions.”

Sascha adds, “Aviation aiming to become more sustainable should learn from the lessons and traps other e-mobility sectors like automotive already face, especially when it comes to battery technology, charging and infrastructure, change management and the overall acceptance of clean-tech innovations.”

Commenting on the Uber Elevate Summit 2017 in Dallas, Sascha notes, “It became clear that electric and hybrid aviation needs collaboration partners from different backgrounds. Seemingly, the hidden champion P3 took a step in the right direction contributing to sustainable skies.”

Asked if P3’s experience with GPRS (General packet radio service), a mobile device communications network used in some “connected car” applications would be applicable to autonomous aircraft, Sascha explained that the technology involved is less a problem than the regulatory aspects.

“GPRS might be a possible technology for autonomous aircraft, but as it is with the powertrain except for batteries, one of the biggest challenges will not be technology, it will be certification for aerospace purposes. What P3 can do is to provide solutions that work for telecommunications, the connected car and the future autonomous cars and transfer best practices to aviation. Basically, an autonomous aircraft is not more difficult to code than an autonomous car as you already have autopilot systems and not as much obstacles and scenarios you have to consider, only at Take-off and Landing. Nonetheless, especially for VTOLs, a sophisticated sense-and-avoid-, birdstrike-, cybersecurity- and a rogue-pilot-protection system are necessary. When it comes to air traffic management again technology will solve a lot of problems but the transition phase will require a lot (Overhauled airspace structure, better air-to-air communication, charging grid infrastructure, etc.).”

Future flight might allow human control in an otherwise automated sky. How will we integrate these elements?

He refers to projects in which P3 helped clients develop digital instrumentation for their vehicles, assisted another in achieving cost limits for power electronics, and yet another on calculating best practices and outcomes for high and low-voltage battery systems.  For one German car maker, P3 helped create a customer care roadmap, expediting customer service issues.  The firm assisted in finding optimum uses for batteries that had reached the end of service lives in vehicles, and finally determined the best way to recycle spent batteries.  P3 gave the car maker principles they used to launch a new model electric car, relying on demonstrated ideas developed across many new challenges.

Sascha defines an approach certain to appeal to potential clients.  “Our project management approach is that we keep the communication to our customers so close, that contradictory requirements always end in the customer’s best interest and not ours.”  Multi-discipline teams decide .on courses of action that will improve on the client’s ideas.

P3 has grown to 30 subsidiaries, including e-flight, batteries, etc., challenging traditional management practices.  They reach out to technical universities in Germany and the University of Michigan in America.  They are now negotiating efforts with MIT and Stanford for the P3 E-Flying Team.

New technologies require new approaches, and P3 seems to be open to exploring new directions in sustainable aviation.

(All renderings of the Fly™ Citycopter are from this source.)


Surefly – A Pickup and a Pick-Me-Up

We’re experiencing a myriad of multi-rotors lately, mostly in the vertical lift on demand, sky-taxi  category.  Workhorse, a company specializing in electric vehicles, has introduced the Surefly, an eight-rotor, hybrid-powered two-seater with actual pilots in mind.  Workhorse will reveal the aircraft at the Paris Airshow on July 19, possibly filling in the blanks for the internal-combustion engine and electric motors on the machine.

The company started with an award-winning conversion of a Pontiac Sky and has leapfrogged into the creation of unique electric vehicles.  These include not only Surefly, but  a hybrid pickup truck, a hybrid medium-duty step van useful for local deliveries, and Horsefly – an eight-rotor drone capable of delivering 10-pound packages.  Horsefly is launched from the step van, especially helpful in rural areas.

Surefly, as noted, has few listed specifications, but we can guess the 7.5 kilowatt-hour battery packs are Panasonic 18640 units, since the company is partnered with Workhorse and their batteries form the packs on the pickup and the step van.  A battery pack and controller at the motor end of each foldable arm enables short cable runs.  Full redundancy on each arm will allow continued flight even with the loss of several components.  Stephen Burns, CEO of Workhorse, says they decided that there could be no single point of failure that would bring the copter down.  That would be a hard landing with the machine’s 1,100 pound “curb weight” and its 1,500 maximum takeoff weight.

It’s also set up to enable simple control and safeguard the pilot and passenger.  Burns wanted his son to be able to fly Surefly to school and avoid traffic jams along the way.  The young man graduated from high school before that became a reality.  Still, Burns sees certification possible by 2019, although he admits regulatory hurdles are harder to overcome than technical ones.

The helicopter borrows a great deal of the technology from the W-15 Pickup, its 7,200 pound Gross Vehicle Weight Rating yielding a surprising 0-60 time of 5.5 seconds.  The W-15 can run 75 miles on batteries alone, and up to 310 miles on a full tank.  For its weight and size, the 28 city mpg, 32 highway mileage figures are excellent.  The company reports 5,000 advance orders from fleet sales.

Bigger still, Workhorce’s step van carries a maximum weight of 19,500 pounds, including the Horsefly delivery drone.  A well-organized delivery program can save fuel and enable extended reach from a sequential locations.  The company’s Metron™ telematics program, used to locate and keep track of performance metrics, probably helps guide the drone to its intended destination.

Workforce has a wonderful range of products, and we look forward to Paris in July.


Another Combined Motor-Controller System

Compact Dynamics, a German electronics firm associated with MAHEPA, the green aviation consortium, has developed two types of electric motor-controller combinations adaptable to aeronautical use.  Their Dynax® Transversal flow machines and Dynadyn® Radial flux drives integrate power electronics with the motor.

Dynax MGi25-48 combines motor and controller in one compact unit

Their Dynax MGi25-48, one of two lower-power motor-controller combination, is rated at 25 kilowatts (33.5 horsepower) maximum power at 58 Volts, and 20 kW continuous output.  The small motor can generate an impressive 75 Newton-meters (58.3 foot pounds) of torque from its 14 kilogram (30.8 pound) heft.  Even with its controller mounted atop, the full motor package is only 318 millimeters (12.5 inches) high, and 233 mm (9.17 inches) deep.  The motor itself is only 107 mm (4.2 inches) thick.  Its 10,000 rpm top speed obviously requires a propeller speed reduction unit for best efficiency.

A higher-voltage model, the MG40-400, apparently under development, will operate on 300 to 415 Volts, and put out 40 kW (53.6 hp.) from 350 Volts.  The motor weights 10.2 kg (22.44 pounds), but the controller adds 5.6 kg (12.32 pounds).

MG-40-400’s compact dimensions

Compact Dynamics’ Dynadyn radial-flux motors are more powerful, and a bit thicker than their lower-power cousins, but still compact and light weight, each weighing 13 kilogram (28.6 pounds) with integrated controllers.  The Dynadyn 75 has a maximum 75 kW (100.5 hp.) and 25 kW (33.5 hp.) continuous output: the Dynadyn 85 achieves 86 kW maximum and 55 kW (73.7 hp.) continuous power.  They generate 69 and 79 nM (50.9 ft-lbs. and 58.3 ft.-lbs.) of torque, respectively.  They weight 5.8 and 6.6 kg (12.76 and 14.52 pounds), respectively.

Dynadyn 75 motor-controller provides high torque, high efficiency

All motors are liquid cooled and are “Characterized by a very low moment of inertia and high dynamics. With the high power density and low weight there are different options for use of the Dynadyn®-drives in motorsports or aviation.”  All use CAN protocol and can be adapted for various applications with a number of options.  Prices will probably reflect those for those for the 500e drive system for Formula Student teams, 9,000 euros for a 42 kW (56.3 hp.) motor-controller combination.

Certainly, the motors have characteristics that can be adapted to aircraft use, and the company claims that it will produce configurations that suit client’s individual requirements.  These are similar to the Qinetix motor outlined here a few weeks ago.  It’s nice seeing competitive forces rising in the electric aerospace market.