What happened to Solar Impulse 2’s batteries on those long five days and nights over the Pacific?  It took months of enforced downtime in Hawaii to have new batteries made, sent from Korea, installed, tested, and flown again.  Could the plane have completed the flight on the original batteries?

Full-scale testing of SI2 battteries after addition of cooling system and before its departure from Hawaii

Full-scale testing of SI2 battteries after addition of cooling system and before its departure from Hawaii

Kokam, manufacturer of the airplane’s cells, has released new information that provides details of the drive system and relieves a few lingering anxieties.  An over-riding concern was that batteries overheated on the Japan to Hawaii part of the mission, topping out at 50 degrees Centigrade (122 degrees Fahrenheit) – above their design temperature.  Your editor has thought deeply about what Andre’ Borschberg must have gone through every day of the five over the Pacific, seeing the temperatures on the four battery packs climbing as he pointed the airplane’s nose up in its saw tooth flight profile.

Borschberg explained that stress in a comment on SI2’s blog.  “”I feel exhilarated by this extraordinary journey. I have climbed the equivalent altitude of Mount Everest five times without much rest. The team at the Mission Control Center in Monaco was my eyes and my ears. The MCC was battling to give me the possibility to rest and recover, but also maximizing the aircraft’s energy levels and sending me trajectories and flight strategies simulated by computer. This success fully validates the vision that my partner Bertrand Piccard had after his round-the-world balloon flight to reach unlimited endurance in an airplane without fuel.”

Kokam's Z-fold construction would add surface area to allow more interaction of active materials

Kokam’s Z-fold construction would add surface area to allow more interaction of active materials

Concern, intense monitoring and precise directions enabled the pilot, craft and the four 38.5 kilowatt-hour battery packs to make it through five days and nights of high tension.  Kokam’s “Ultra High Energy NMC battery packs” one per motor gondola, have a total of 154 kilowatt-hours of energy storage.  The 150 Amp-hour cells made 17 flights totaling 26,744 miles (43,041 kilometers), fed by the 17,248 silicon solar cells on the wings, fuselage and horizontal stabilizer.  Those cells produced 11,000 kWh of electricity during the around-the-world voyage.

The lithium nickel manganese cobalt cells produce high energy, sometimes associated with a propensity for thermal runaways.  If the cobalt would lead to that, the manganese seems to act as a butter to prevent such problems, and NCM chemistry has a good safety record.  The cells’ 96-percent efficiency keeps helps reduce temperatures during charging, and the pouch-type configuration provides a larger surface area to disperse heat than that available to prismatic or cylindrical cells..

Solar Impulse technicians decided to remove the battery packs when the airplane landed in Hawaii.  Testing in Germany, where the batteries are packaged for use in SI2, found the cells were undamaged even after exposure to higher than normal temperatures, and had lost only that capacity they would have in more normal circumstances.

Large area presented by pouch cell allows battery to act as large heat sink

Large area presented by pouch cell allows battery to act as large heat sink

Andre’ Borschberg explained the SI2 team did not blame the batteries for the mid-journey hiatus.  “When you are designing an experimental aircraft every additional system is a potential source of failure, and that is why we had not initially integrated a cooling system. As we had the time in Hawaii to replace the batteries, we decided to integrate the cooling system to give the airplane more flexibility, especially in very high temperature environments. The overheating problem was in no way related to any issue with Kokam’s batteries, which have delivered excellent performance for Solar Impulse 1 and on every leg of the flight with Solar Impulse 2, supporting our record- breaking circumnavigation of the globe.”

SI2’s batteries were subjected to extremes of temperature and multiple days of uninterrupted charging and discharging, and still managed to perform at high levels of performance and reliability.  This in itself should provide encouragement to others now designing future electric aircraft.

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2X Battery Commercially Available This Year?

We would love to see a 5X or even 10X battery in our future, but that will happen, quite possibly, at the speed of an eight-percent increase per year, as demonstrated for the last several decades of battery development.

That would mean waiting for about 10 years for battery energy densities to double.  What if we could double energy density right now, as in starting commercial production of a battery with 2X the energy density of those currently available?

Lithium battery energy density doubles every 10 years, according to J. R. Straubel

Lithium battery energy density doubles every 10 years, according to J. R. Straubel

Solid Energy Systems, led by MIT alumnus Qichao Hu, has announced it is ready to hit the market in the next year.  According to MIT News, “SolidEnergy plans to bring the batteries to smartphones and wearables in early 2017, and to electric cars in 2018. But the first application will be drones, coming this November. ‘Several customers are using drones and balloons to provide free Internet to the developing world, and to survey for disaster relief,’ Hu says. ‘It’s a very exciting and noble application.’”

What level of manufacturing and how quickly the company can ramp up to meet demand wait to be seen, although their dedication is evident in the BBC interview, the reporter trudging through a Boston winter to see the plant in action (or at least what the team would show him).  It we see a number of drones overhead carrying larger cameras because of the improved energy density of their batteries, we’ll know the future is on its way.

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Students at the National University of Singapore (NUS) have a history of creating ultra-lightweight flying machines that are also green – floating around on electric power.  Their earlier effort, Snowstorm, a 24-rotor, single-person lifting device, so far has hovered only indoors.

Eight engineering students, working within the school’s “Frogworks” program, have escaped into the great outdoors with their Delta, the world’s lightest electric paraglider – according to the school.

Lightweight trike adds only 49 kilograms (107 pounds) to Delta

Lightweight trike, primarily carbon fiber and aluminum, adds only 49 kilograms (107 pounds) to Delta

With two eight-kilowatt electric motors, four 14S lithium polymer battery packs, and tricycle landing gear, the Delta weighs in at 49 kilograms (107.8 pounds) empty weight.  Delta can carry a 75-kilogram (165 pound) pilot.  Cleverly constructed of carbon fiber and aluminum, the craft is claimed to be “the lightest aircraft in the world that can take off and land with wheels while carrying an adult pilot.”

Pilot xxx with Delta team following successful test flight for NatGeo

Pilot Narint Lohathong with Delta team following successful test flight for NatGeo

Fourth in a series of vehicles designed and built by NUS students in the Design-Centric Program (DCP) at the NUS Faculty of Engineering, the Delta was constructed for a National Geographic television program. “Machine Impossible” (viewable only in Asia, alas).  Test flown by pilot Narint Lohathong on March 19 at the Sungai Rambai Aerodome in Malacca, Malaysia, the airplane took off quickly but noisily (especially for an electric airplane).

Its 31-inch propellers might be replaced by longer blades turning slower, a good way to reduce prop noise.  That might take bigger, slower-turning motors, and then the age-old problem of greater weight comes to the fore.  Right now, the airplane can fly 36 kilometers per hour (22.3 mph) for about six kilometers (3.7 miles).  Not a terribly practical commuter, even, Delta is a three-month project meant to suit the needs of a TV show more than the needs of the flying public.

Mr Chan Wai Yang, a Year 3 engineering student at NUS, explains the greater significance of the machine.  “Designing and building The Delta was an experience like no other. We had a great learning experience as we went about tackling various aspects of the project, from constructing the physical frame to designing and implementing the aircraft’s electric energy system and pilot safety system. It was an engineering challenge we greatly relished,”

Safety systems include a roll cage to protect the pilot, fiberglass rods that act as shock absorbers for the main wheels, barrier nets between the pilot and propellers, and motor kill switches to shut things down quickly.

Instrumentation consists of four battery monitors. Large kill switches enhance safety for pilot

Instrumentation consists of four battery monitors. Large kill switches enhance safety for pilot

Associate Professor Martin Henz, project supervisor and advisor at the DCP seconded Yang’s endorsement of the project.  “We are thrilled to have this opportunity to build an all-new machine for the National Geographic Channel. Designing and building The Delta allowed us to push the limit of our creativity and engineering know-how,  while building upon our experience from previous successful FrogWorks projects. We will continue to fine-tune The Delta, and at the same time, we also look forward to creating more sustainable recreational vehicles, be it on land, at sea or in the air. Such projects have tremendous values in the education of our students in Engineering.”

On land, sea, and in the air, students at the National University of Singapore are exploring the limits of time and technology – and coming up with must-see TV at the same time.


Even with Batteries, Paul MacCready Was Right

Dr. Paul MacCready repeatedly urged us to do more with less, getting big results from modest use of materials.  That philosophy may be upheld yet once again by researchers from the Helmholtz-Zentrum Berlin (HZB) Institute of Soft Matter and Functional Materials.

As reported here many times, people like Dr. Yi Cui at Stanford University, researchers at MIT, the Fraunhoffer Institute in Germany and many others are attempting to find the magic combination of ingredients that will allow us to transcend the weight penalty we currently trade for payload in heavier-than-desired electric aircraft.

Lithiation in

Lithiation in HZB cell, with majority of lithium ions adsorbed in thin layer closest to electrolyte boundary layer.  Lithium ions migrate through the electrolyte (yell0w) into the layer crystalline silicon (c-SI).  During the charging cycle, a 20-nm layer (red) develops on the silicon electrode, adsorbing extreme quantities of lithium ions.  Illustration: HZB

Scientists at the HZB, led by  by Prof. Matthias Ballauff have directly observed for the first time a lithium-silicon half-cell during its charging and discharge cycles.  Dr. Beatrix-Kamelia Seidlhofero carried out the experiments using the neutron source located at the Institute Laue-Langevin in Grenoble, France.  She explains, “We were able to precisely track where the lithium ions adsorb in the silicon electrode using neutron reflectometry methods, and also how fast they were moving.”

This precision allowed the team to see how lithium ions “migrate” into thin films of silicon – often the center of experiments to increase the energy stored in lithium batteries.  Researchers determined the energy storage capacity of lithium-ion batteries “might be increased by six times” by using silicon instead of graphite in the anodes.

Substantiating the idea that “less is more,” Dr. Seidlhofero found that, “Lithium ions do not penetrate deeply into the silicon. During the charge cycle, a 20-nm anode layer develops containing an extremely high proportion of lithium. This means extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.”

Since 20 nanometers equals only 0.0000000787 inches, the material layer is extremely thin, and the materials needed to react with it are exceedingly small.  Dr. Seidlhofero found two different zones on the test electrodes, with the action taking place close to the surface.  Near the boundary to the electrolytes, the 20-nm layer showed extremely high lithium content, with 25 lithium atoms lodged among 10 silicon atoms.  A second, adjacent layer contained only one lithium atom for 10 silicon atoms.  Both layers combined are less than 100 nm thick after the second charging cycle, according to researchers.

Materials such as graphite used in many batteries can only “stably adsorb” a small number of lithium ions during charging.  Silicon can adsorb many more ions, but tends to crack under stress.  This stressing and relaxation eventually causes electrodes to crumble and batteries to fail.  Other researchers have tried a variety of fixes for this problem over the last several years.

Note lithiation occurs most strongly at interface of electrode and electrolyte. Illustration: HZB

Note lithiation occurs most strongly at interface of electrode and electrolyte. Illustration: HZB

In HZB’s testing, after discharging the battery, the team found about one remaining lithium ion per silicon node in the electrode’s silicon boundary layer exposed to electrolytes.  The fact that most of the activity takes place at a surface level might prevent flexing and cracking at deeper levels, but that’s just your editor’s shallow surmise.

The HZB  press release concludes, “Seidlhofer calculates from this that the theoretical maximum capacity of these types of silicon-lithium batteries lies at about 2300 mAh/g. This is more than six times the theoretical maximum attainable capacity for a lithium-ion battery constructed with graphite (372 mAh/g).”

The Institute adds a grace note that “very thin silicon films should be sufficient for adsorbing the maximum possible amount of lithium, which in turn would save on material and especially on energy consumed during manufacture – less is more!”

Certainly a 6X battery, all that much lighter for the same level of energy, would be heaven-sent as far as aircraft are concerned.

HZB’s findings are published as,  “Lithiation of Crystalline Silicon As Analyzed by Operando Neutron Reflectivity,” in ACS Nano.  Authors include Beatrix-Kamelia Seidlhofer, Bujar Jerliu, Marcus Trapp, Erwin Hüger, Sebastian Risse, Robert Cubitt, Harald Schmidt, Roland Steitz, and Matthias Ballauff.


CAFE board member John Palmerlee alerted your editor to news that the federal government is creating yet another round of incentives to “spark” development of “significantly smaller, lighter and less expensive batteries.”

One possible outcome from PNNL in research to obtain 500 Watt-hours per kilogram battery

One possible outcome from PNNL in research to obtain 500 Watt-hours per kilogram battery

A consortium of researchers led by Pacific Northwest National Laboratory (PNNL) will receive up to $10 million a year over five years to perk up battery performance, with the goal of creating a 500 Watt-hour per kilogram battery pack, about three times that of currently available commercial offerings.  The new batteries should be “reliable, safe and less expensive,” according to consortium director and PNNL materials scientist Jun Liu.  Research will come from partners nation-wide, including:

  • Brookhaven National Laboratory
  • Idaho National Laboratory
  • SLAC National Accelerator Laboratory
  • Binghamton University (State University of New York)
  • Stanford University
  • University of California, San Diego
  • University of Texas at Austin
  • University of Washington
  • IBM (advisory board member)

Even though the goals and the budget seem similar to those explained by Energy Secretary Steven Chu two years ago, his directive included research on alternative materials, such as magnesium and yttrium, combining research and even “making new materials.”  That project was led by the Argonne Laboratory and was already nearing its second year, while the current program has PNNL leadership and is just beginning.  It focuses on lithium-metal batteries, with lithium instead of carbon as the battery’s negative electrode.  Cathodes can be made from many materials, and research will attempt to “prevent unwanted side reactions in the whole battery that weaken a battery’s performance.”

As with the earlier study, researchers hope to develop practical solutions for automotive and battery manufacturers which “can be .quickly and seamlessly implemented by industry.”  The consortium will also welcome ideas from outside sources, setting aside 20 percent of its budget for “seedling projects,” allowing findings from the larger “battery research community.”  Outcomes will benefit not only EV development, but could advance stationary grid energy storage.

$10 million per year split among 10 academic and scientific institutions seems almost trivial, especially compared to unit costs for something like the F35, the cheapest model of which is priced at $148 million and the most expensive at $337 million.  Regardless of the argument for either “investment” in producing better batteries or enhancing national security, $50 million spread over five years would probably not buy one F35 engine.

The White House provides this fact sheet for the five-year project.


Alan Soule Escapes the (Old) Iron Curtain

Now in its 57th day, the around-the-world-in-80 eDays tour finds itself in Ukraine, having crossed China, Kazakhstan, and a big chunk of Russia since mid-July.  Alan Soule’ a CAFE board member, drives the only American entry, A Tesla S sedan.  From time-to-time, he is joined by assistant drivers on the long trek.   He and the Czech team are well ahead of the other drivers, still clustered in the Moscow area.

The trip through China involved obtaining driver’s licenses for everyone, negotiating many ways to pull electricity from the main power supplies to charge the 11 teams’ vehicles, and enjoying the local cuisine.

Alan Soule' giving a farewell address to his Chinese hosts

Alan Soule’ giving a farewell address to his Chinese hosts

As one might guess, there aren’t necessarily a lot of Tesla Superchargers or Aerovironment Turbodocks in the Ghobi Desert, and the Swiss team shows several alternatives they jury-rigged on their expedition.

Swiss team found many "alternative" charging stations. This looks like the most conventional

Swiss team found many “alternative” charging stations. This looks like the most conventional

Whether you remember David Niven, Jackie Chan, or (Heaven help you) the Three Stooges in the cinematic version of this epic journey, they didn’t have to find charging stations, often totally unsuited to the task at hand, and improvise connections potentially (unavoidable pun) harmful to car and driver.

Swiss team improvised with great alacrity on their trip through western China

Swiss team improvised with great alacrity on their trip through western China


Was it the red wire or the blue wire? Swiss team's options probably didn't include instruction manual

Was it the red wire or the blue wire? Swiss team’s options probably didn’t include instruction manual

With only 23 days left in the run, it looks like most teams will complete the earthly transit on time.  We wish them all well, and look forward to Alan’s report of his adventures.


In the Small World category, the team leader of the 2011 Green Flight Challenge winning team is designing the next generation of a drone that can carry blood and stool samples from remote and otherwise inaccessible parts of Madagascar to a central laboratory where the samples can be analyzed.  Jack Langelaan, Professor of Aerospace Engineering at Pennsylvania State University, is working with Vayu Aircraft to develop a vertical takeoff and landing machine specially crafted to meet the needs of the ValBio Centre.

Early version of Vayu drone has functionality of proposed Courier, but lacks sleek lines

Early version of Vayu drone has functionality of proposed Courier, but lacks sleek lines

The video shows an early version of the drone, while pictures on Vayu’s web site depict a sleeker, more refined approach.  The functionality for both machines would seem to be identical, but the styling for the projected future version is far more “marketable.”

Dr. Peter Small, Founding Director of Stony Brook’s Global Health Institute, sees the flights as a win-win for drones and villagers. “The flights to and from villages in the Ifanadiana district [of Madagascar] ushers in a new era in bringing healthcare to people living in really remote settings. This would not have been possible without the support of the government and people of Madagascar.  In this context drones will find innumerable uses such as accelerating the diagnosis of tuberculosis and ensuring the delivery of vaccines.”

To ensure the drone making the deliveries does not cause operator injury, ducted fans provide lift for takeoffs and landings.  The fans embedded in the wing have a mechanically-actuated door on top and passively-activated louvers on the lower surface to protect people working around them.  An additional pair of ducted fans on the trailing edge sit on detachable struts “that aid in convenient transport and vehicle handling.”  They can rotate up to 110 degrees in one axis.  Although they assist in takeoffs and landings, their primary function is to provide thrust for forward flight.  You can see the operation of the fans, covers and louvers in this short video.

Batteries can provide 60 to 120 minutes endurance and a range up to 60 kilometers’ (37.2 miles’) range with a full payload.  That payload can be up to 2.2 kilograms (4.84 pounds) and sits on the aircraft’s center of gravity.  Besides medical samples, the nine liter payload bay can accommodate cameras and sensors with connections to onboard power and a data port that can connect the payload with the aircraft’s avionics.  80-percent lightweight carbon fiber construction makes the sizable payload possible.

Cutaway shows Courier's batteries in nose, centrally-located payload bay

Cutaway shows Courier’s batteries in nose, centrally-located payload bay

One advantage Vayu claims for its VTOL craft is that it does not need to be hand launched like some drones, and that the Courier UAV can land itself, using its “high-resolution optical tracking system and GPS” to set down in a parking space-sized area.

To lower costs, Courier UAV™ mixes custom software, an open-source codebase, and off-the-shelf motors and servos.  This enables others to work with the base machine and customize to suit different applications and environments.

Because Courier is battery powered, no fumes from fossil fuels can contaminate samples or medicines delivered by this clean flight vehicle.  Wings, fans, motors, landing gear, batteries and payload are all removable, and the dismantled airframe can be carried on small trucks, trailers, or even on horseback, making the aircraft usable in even the most isolated areas.

Valbio Research Centre has ideal roof for drone landings (top of picture)

Valbio Research Centre has ideal roof for drone landings (top of picture)

Stonybrook’s research station, the Centre ValBio at NamanaBe Hall on the borders of Ranomafana National Park, is a modern, green building with three laboratories and lodgings for up to 52 visiting scholars.  A triangular roof jutting out from the building seems ideally suited for aerial visits by drone.

Centre ValBio works with a wide variety of researchers, including Patricia Wright, whose 28-years of research and advocacy for the island’s lemurs is portrayed in a recent IMAX film.  Even the film-makers might want a drone for future efforts.


Two major types of fuel cells vie for vehicle designers’ attention: PEM, or proton exchange membrane types, and solid oxide fuels cells (SOFCs).

PEMs (also known as polymer electrolyte membrane fuel cells) require an expensive catalyst such as platinum, and hydrogen as fuel. Hydrogen itself is costly to produce and runs up the operating cost for such a fuel cell.

Schematic for Nissan e-NV200 SOFC vehicle

Schematic for Nissan e-NV200 SOFC vehicle

Nissan Motor Co., Ltd. timed things to coincide with the 2016 Olympics opening in Rio de Janeiro, Brazil for the introduction of their solid oxide fuel cell vehicle, a van that runs on bio-ethanol electric power.  Nissan’s Carlos Ghosn claims this to be a first, with benefits for potential users.

“The e-Bio Fuel-Cell offers eco-friendly transportation and creates opportunities for regional energy production…all the while supporting the existing infrastructure. In the future, the e-Bio Fuel-Cell will become even more user-friendly. Ethanol-blended water is easier and safer to handle than most other fuels. Without the need to create new infrastructure, it has great potential to drive market growth.”

The e-NV200 van, reputedly necessary as the prototype because of the relative bulk of the SOFC system, runs on 100-percent ethanol and charges a 24 kilowatt-hour battery from its 5 kilowatt fuel cell to produce a cruising range of 600 kilometers (372 miles) – a figure certain to capture the interest of future customers.

Now touring public roads in Brazil, the e-Bio Fuel-Cell vehicle, announced by Nissan in Yokohama last June, has a powertrain that “is clean, highly efficient, easy to supply, and it runs on 100-percent ethanol or ethanol-blended water. Its carbon-neutral emissions are as clean as the atmosphere, which will be the part of natural carbon cycle. Also, the e-Bio Fuel-Cell offers the brisk acceleration and silent driving of an EV, along with its low-running costs, while boasting the driving range of a gasoline-engine vehicle.”  All this is according to BiofuelsDigest.com, certainly a cheerleader for this approach to mobility.

Theoretically, the use of ethanol, controversial in its use in gasoline-powered cars, allows integration into existing infrastructure.  One thought is that since the test vehicle holds only 30 liters (roughly eight U. S. gallons) for its competitive range, “people may only need to stop by small retail stores to buy fuel off the shelf.”  One imagines two-liter bottles of the fuel, easily carried by most shoppers.

Made primarily from sugarcane (abundant in Brazil) and corn (abundant in America’s Midwest), ethanol and ethanol-blended water would be problematical in using food crops to make fuel.  That criticism might be mitigated by the van’s possible 46.5 mpg fuel economy on ethanol.

The U. S. Department of Energy notes, the Renewable Fuel Standard (RFS) limits the amount of ethanol produced from starch-based feedstocks to 15 billion gallons. This ensures there are enough feedstocks to meet demand in livestock feed, human food, and export markets.

The Department show cellulosic sources for ethanol, including corn stover,  wood waste, and the ever-popular but seemingly elusive switchgrass, as viable substitutes for food-based feedstocks for the liquid fuel.

Potential for cellulosic ethanol in the next few decades

Potential for cellulosic ethanol in the next few decades

“They are either waste products or purposefully grown energy crops harvested from marginal lands not suitable for other crops. Less fossil fuel energy is required to grow, collect, and convert them to ethanol, and they are not used for human food.”

Nissan hopes to realize “a zero-emission and zero-fatality society for cars,” certainly part of many efforts by government, industry, and academia lately.  Nissan states they, “Will continue.. to promote vehicle intelligence and electrification. Nissan’s brand promise of ‘Innovation That Excites’ is delivered with ‘Nissan Intelligent Mobility,’ which focuses on how cars are powered, driven and integrated into society through a more enjoyable driving experience.”

Now, start working on making this system more compact so it will fit in a light airplane.


Don’t Smoke ‘Em Even if You’ve Got ‘Em

Biofuels would be wonderful if they didn’t starve people while feeding trucks, cars and airplanes.  Living with such a constraint, though, might prove to be productive, profitable, and environmentally sound.

The Guardian describes efforts in America’s tobacco country to grow a crop that will be less destructive of human lungs and hearts if it is consumed in jet engines rather than in cigarettes.

“’We’re experimenting with varieties that were discarded 50 years ago by traditional tobacco growers because the flavors were poor or the plants didn’t have enough nicotine,’ explains Tyton [BioEnergy Systems] co-founder Peter Majeranowski.”

In a case that oddly enough is GMO free, “Researchers are pioneering selective breeding techniques and genetic engineering to increase tobacco’s sugar and seed oil content to create a promising source of renewable fuel. The low-nicotine varieties require little maintenance, are inexpensive to grow and thrive where other crops would fail.”

Fuel tobacco is a higher-value crop than hay, for instance, and “looser” farming techniques needed to grow it could increase profits to the farmer.

Besides Tyton, the Lawrence Berkeley National Laboratory, in partnership with UC Berkeley and University of Kentucky, received a $4.8m grant from the US Department of Energy to research the potential of tobacco as a biofuel.

Meanwhile, In South Africa

Half a world away, Boeing is partnering with South African Airways on Project Solaris, which saw its first tobacco-fueled passenger flight this year.  The Project uses a type of tobacco that would not be desirable for smokers.  Farmers can use “the same equipment and skills” needed to grow smoking tobacco, and “because the harvest is mechanized, it takes less labor to produce a crop.

Value chain for Solaris tobacco fuel, showing process and multiple products

Value chain for Solaris tobacco fuel, showing process and multiple products

One acre of such tobacco can yield up to 80 wet tons of biomass and byproducts, which can provide not only biofuel, but animal feed and fertilizers.

South African Airways flew its Boeing 737-800 from Johanneburg to Cape Town (1,220 kilometers – 758 miles) using 6,300 liters (1,664 U.S. gallons) of a jet fuel made from nicotine-free tobacco grown in the Limpopo region for the Solaris Project.

SAA, BoeingSkyNRGthe World Wildlife Fund-South Africa, and Sunchem, the developer of the novel energy tobacco crop, expect small landholders and commercial farmers to “grow sustainable bioenergy resources while stimulating socio-economic development in the region.”

As with oil, tobacco suffers from a global oversupply for the time being, so a new market is highly desirable for producers.  It may be helpful to SAA, too, reported to be in financial difficulties by Bloomberg, which comments on a hoped-for future for the airline and for tobacco fuel.  “Airlines are examining ways to power more flights from biofuels to limit the environmental impact of aviation and ease dependency on oil. Unprofitable SAA aims to have used 20 million liters (over 5,280,000 gallons) of bio-jet fuel by the fourth quarter of 2017, Ian Cruickshank, its head of environmental affairs, told reporters in Cape Town. He said the company is seeking to use 500 million liters (over 132 million gallons) by the same time in 2023.”

Project Solaris has created a special tobacco with smaller leaves, but largers “buds” or flowers that contain a significant amount on non-nicotine oil.  The stems and “waste” parts of the plant can make press cake for animal feed.  The plant can be used as fertilizer for other agricultural products and can provide water and crop protection, similar to other types of tobacco farming.  A boon to struggling farmers, the plant can provide up to three crops per year.

In 2015, Project Solaris earned the Roundtable on Sustainable Biomaterials (RSB) certification, one of the strongest sustainability standards for biomaterials in the world. The RSB certification provides a model to further expand the production of the Solaris crop in a sustainable way.

Not Only Tobacco, but Salt-water Plants

Boeing has also partnered with a consortium including Masdar University in the United Arab Emirates to produce biofuels from halophyte plants, which are able to thrive on saltwater.  In turn, they can be grown in desert regions irrigated by seawater, and provide a habitat for fish (which help fertilize the crop and provide a secondary food source).  No normally arable land is sidetracked to produce the fuel, which one expert describes as superior to the environmentally-destructive and low-grade materials coming from tar-sand production.

These efforts, well subsidized and backed by excellent science, show great promise for cleaning our skies and maybe even our lungs.


Taja Boscarol of Pipistrel in Slovenia relays the information that NASA has tested Pipistrel’s electric propulsion system as part of its electric flight research for the X-57 program.  It would seem reasonable to start by checking out Pipistrel’s well-tested motor package, one of the few that comes with fully-matched controller, batteries, and ancillary gear.

Pipistrel motor on Airvolt test stand at Armstrong Flight Research Center

Pipistrel motor on Airvolt test stand at Armstrong Flight Research Center

NASA performed its tests on its 13.5-foot Airvolt stand at the Armstrong Flight Research Center at Edwards Air Force Base, California.  Heavily instrumented, the Airvolt stand collects data through “high-fidelity sensors,” and transmits the collected information to a data acquisition unit that processes, records, and filters the measurements.  NASA and Pipistrel should be able to make good use of this data.

Normally installed on the Taurus Electro G2 motorglider, the Roman Susnik designed motor produces 40 kilowatts (53.6 hp.) at low rpm while producing high torque, an ideal combination for rapid climbs to soaring altitude.

Motor system as mounted on Pipistrel Taurus Electro G2

Motor system as mounted on Pipistrel Taurus Electro G2

NASA will collect “torque and thrust measurements, high-fidelity voltage analysis, power efficiency, and details on how the system behaves. A simulation model will be developed from that information to study flight controls, power management and transition issues of a distributed electric aircraft.”  All this is intended to prepare the way for the X-57 SCEPTOR (Scalable Convergent Electric Propulsion Technology Operations Research), a 14-motor speedster designed to fly on one-fifth the energy of a conventional aircraft of the same size.

Because factors such as electro-magnetic interference play a part in motors and the circuits controlling them, it’s useful to test and understand the characteristics of a single motor before teaming it up with 13 others.  Because Pipistrel’s motors are well-proven and known, they make a good baseline for further testing.  In the multi-motor systems, then, “variables can be reduced and multi-motor configuration optimized.”  This level of understanding and demonstrated performance should increase the element of certainty in ongoing development of the X-57.

Pipistrel Plug&Play system laid out. G2 would have two-blade propeller, though

Pipistrel Plug&Play system laid out. G2 would have two-blade propeller, though

Taja’s press release continues, “’Overall, we are getting excellent data,’ said Mr. Yohan Lin, Airvolt integration lead. ‘What we are learning will help us to understand this new technology, and be a starting point for complex challenges. Each system is different, but we will be ready.’”

Airvolt is one of many tools that support NASA’s goal of creating low-carbon aviation. Pipistrel was the first aircraft producer to make both fully electric 2-seat and 4-seat aircraft and, “fully supports this goal and is proud to be a part of it.”

As the winner of the 2011 Green Flight Challenge with its G4, a craft that set a still-unbroken record of 403.5 passenger-miles-per-gallon, Pipistrel has shown its dedication to achieving “green” aviation.

You can read a detailed report on the Airvolt Aircraft Electric Propulsion Test Stand, written by Aamod Samuel and Yohan Lin, both at  NASA Armstrong Flight Research Center, Edwards, California.

Taja shares other company accomplishments.  “Pipistrel has pioneered in-house projects, such as:

Lin performing adjustments on Airvolt test stand

Yohan Lin, Airvolt integration lead, performing adjustments on test stand.  Photo: NASA, Lauren Hughes

“- the World’s first serially produced electric 2-seat aircraft Taurus Electro G2 (2007),
“- the World’s first and for now (as of July 2016) still the only electric 4-seat aircraft – the Taurus G4 (2011), which claimed the victory at the NASA Green Flight Challenge;
“- Alpha Electro, the first practical electric trainer, optimised for basic training

“Pipistrel also provides customised development of systems and technologies for electric flight on manned and unmanned platforms. Public projects, where Pipistrel’s technology has been used and showcased among others include:
“-a very ambitious project of a hybrid aircraft propulsion system, the Hypstair:

“-cooperation with Siemens and other partners on the project of creating an electric aerobatic airplane, the Extra 330LE:

“Electricity is not the only promising source of green propulsion; hydrogen offers many options, too. That’s why Pipistrel participates in the Hy4 project.”