While we wait (with increasing patience or impatience depending on our personalities) for the next round of battery developments to make pure electric airplanes a reality, hybrid possibilities abound.  The definition of “hybrid” might not be as coherent as those used for automobiles.  Some “hybrids in this entry allow extended letdowns following a primary engine failure.  In that case, the added electric motor/generator gives extra minutes to find a safe landing space.  While both motor and primary engine are operational, the system acts much like an automotive hybrid system, both motor and engine combining outputs for added power, or the electrical portion recharging batteries while the engine maintains cruise power.

Some are more like automotive serial systems, an engine-driven generator charging batteries which power the propulsion motor.  Pipistrel, though the Hypstair project, has a 200-kilowatt (268-horsepower) unit ready for test flights in 2017, according to Tine Tomazic, Director of Research and Development.

Several Flying Now

Several years ago, Flight Design in Germany attached a generator/motor setup to a Rotax engine.  The electrical add-on would assist in takeoffs, charge batteries while in flight, and take over as a primary power source if the gasoline engine failed.  This same hybrid approach applies to similar current systems.

Axter Aerospace

Mounted on a Tecnam P92, the Axter Rotax/electric motor combination allows up to 15 minutes of 40-horsepower flying if the Rotax fails.  That should be enough to find a landing area and make a safe letdown.  The Spanish company now markets the powerplant with a variable-pitch propeller.

Ashot Ashkelon

This Israeli system had a brief moment in the spotlight, but seems not to be included in the company’s lineup at this time.  Ashot Ashkelon manufactures many aerospace components, and their hybrid system is shown in coverage of their displays at the Le Bourget Air show in 2015.  The system is markedly similar to Axter’s.

E-Genius’s Hybrid System

e-Genius has been flying with its add-on pod for over a year now, and tests show predictions of 1,000 kilometer (620 mile) trips are doable.  The 20-kilowatt generator burns five liters per hour, and is turned on after e-Genius has gained sufficient altitude to make its added sound level imperceptible from the ground – a practice that seems perfect for a noise-conscious world.

Close to Flight

Equator’s Hybrid System

Both the Equator P2 and e-Genius rely on the Aixro/Engiro hybrid generator-motor system for flight.  Equator’s units include a 60 kilowatt-hour generator powered by an Aixro Wankel engine, and the motor at the propeller puts out 100 kilowatts (130 horsepower).  Thomas Brodreskift and his crew recently fired up the system and all looks well for its eventual flight tests.


As Tine Tomazic explains in an interview with AVWeb’s Paul Bertorelli, This most powerful of hybrid systems, destined to make the modified Panthera a high-performance hybrid.

Under Development

MDC’s Micro-Turboalternator

This micro-turboalternator drives a lightweight permanent magnet generator, which the makers claim consumes only one pound of fuel per hour per kilowatt output.  Its claimed power-to-weight ratio is “1.7 kilowatts per pound, six times the specific power, or 12-15 times the energy density of lithium polymer batteries.”  The design places the power turbine driving the bypass flow at the front of the combustor rather than at the engine exhaust.  A compact recuperator recovers heat from the exhaust decreases fuel consumption.

Given company figures, a 20-kilowatt microturboalternator would weigh under 12 pounds and consume 20 pounds (three gallons) of fuel per hour at full output.   This performance possibly led to the project garnering funding from DARPA and NASA.

DARPA Funds Liquid Piston

Using its High Efficiency Hybrid Cycle (HEHC), The Liquid Piston X Engine has few parts and three combustion events per rotor revolution, resulting in tremendous power density, according to its makers.  One of these coupled to a compact generator may prove useful for ultralight-type aircraft.  Whether fuel consumption becomes an issue remains to be seen at this point.

NASA’s Forays into Hybrid Power

In the video here, Mike Ricci, Vice President of Engineering at Launchpoint Technologies shows off a few of the company’s offerings.  As interviewer Lee Teschler, Executive Editor at Design World points out, Launchpoint is a NASA contractor, apparently involved with several recent projects.

Launchpoint’s portfolio shows extremely light generator sets, using off-the-shelf components from the model aircraft industry as starting points.  With the redundancy inherent in hybrids, less-expensive components could prove to be viable and at least nominally reliable.  Used in pairs or greater numbers, they could be a low-cost answer for light aircraft such as ultralights, self-launching sailplanes or motorgliders.

Promise for Near-term Solutions

Hybrid systems are a possible answer for near-term solutions to making aviation cleaner, if not totally pollution free.  Many entries and their combinations at all power levels make tempting excursions into researching these possibilities an exciting challenge.  We’ll have examples in new entries soon.


If Santa Lived in a Soho Loft and Built Drones

There is much happening in electric aviation, including this flying Santa Claus, dangling from what is claimed to be the world’s largest homemade drone.

And in this interesting behind-the-scenes video we find that Casey Neitstat either has arms of steel, or a clever harness maker who probably outfits touring companies for Peter Pan stage presentations.  The 16-motor system seems capable of hauling a fairly large human skyward, but some critics think this is a sham of some sort.  Your editor sides with the theory that this is a real drone, since Samsung has seen fit to link its name to the project (and the video evidence seems fairly convincing).  In the interests of full disclosure, though, Casey has pulled some fakery in previous stunts, so take this all with several grains of salt, just in case.

If this isn’t enough Casey and Santa-dragging drones for you, try on the VR headset you got for Christmas and indulge in the full 360-degree treatment.

Casey claims to have given up Vlogging (video logging), but his web site lists four ways to access the fruits of his ever-excited imagination: two YouTube channels, Facebook, Twitter, Beme (the app he sold to CNN), and Instagram.  Like Santa, he is everywhere.


Flying (Quietly) Like a REAL Bird!

Not Just an Academic Exercise

Justin Jaworski, Lehigh University assistant professor in the Department of Mechanical Engineering and Mechanics, P.C. Rossin College of Engineering and Applied Science, writes, “From antiquity to Harry Potter, owls continue to captivate and mystify us. Perhaps owls’ most mysterious feat is their ability to fly silently, which enables them to both sneak up on prey and hunt on the wing using their ears alone. For over 80 years, silent owl flight has been linked to a set of unique plumage features, but only recently have the mechanisms to suppress the ‘swoosh’ noise from owl wings been addressed in earnest.”

Justin Jaworski with an object of his studies

Justin Jaworski with an object of his studies

This suppression of noise ensures that prey hunted by owls never know what hits them.  The doves that frequent your editor’s deck, for instance, have no such noise-limiting features, and make quite a racket when the door opens for their morning feeding.  Likewise, a pair of Mallard Ducks who’ve decided to blend in with the small songbirds are audible swooping in from over 50 feet away.

Jaworski has made detailed comparisons of the noise levels generated by different birds, and then gone to microscopic detail to analyze how owls achieve their stealthy flight.  Such findings may make neighborhood airports better neighbors, or reduce the number of noise claims by people living near wind turbines.  Researchers explain that finding might apply to reducing “noise created by air seeping through automobile door and window spaces.”

Jaworski notes that many species of owls suppress their noise at sound frequencies about 1.6 kilohertz (kHz) – above the range that can be heard by most humans.  Because of their great success in picking off small rodents and even rabbits, owls must be taking advantage of that quiet approach.

Three key elements of the owl's quiet wing: a serrated leading edge, a downy canopy across the upper surface feathers, and a fringed trailing edge

Three key elements of the owl’s quiet wing: a serrated leading edge, a downy canopy across the upper surface feathers, and a fringed trailing edge

The owl’s wing includes a serrated leading edge, a “canopy” of downy feathers that overlap and direct airflow across the wing’s chord, and a soft fringe along the trailing edge.  Recreating a “velvety” down canopy on a production aircraft wing could be a tough project, Jaworski and his fellow researchers came up with a 3D-printed trailing edge consisting of “finlets.”  After having tried a variety of open-mesh cloths – including wedding veils – the team found that the threads cross-wise to the airflow did not contribute materially to noise reduction.  They created a series of parallel fibers that direct the air across the wing and off the trailing edge and that emulate the sound-deadening effect of the owl’s wing.  The 3D-printed trailing edge can be fitted to existing wings – giving a 10dB reduction sound without harming overall performance.

Streamwise-oriented 'finlets' are installed on a wing or blade trailing-edge to reduce trailing-edge noise by up to 10dB without substantial changes to the aerodynamic performance and over a range of angles of attack. Photo: Nathan Alexander

Streamwise-oriented ‘finlets’ are installed on a wing or blade trailing-edge to reduce trailing-edge noise by up to 10dB without substantial changes to the aerodynamic performance and over a range of angles of attack. Photo: Nathan Alexander

These noise-reducing effects have been known since at least 1932 and documented in 1972 and 1974 papers.  Jaworski and fellow researchers from four universities contributed to two papers, “Bio-inspired trailing edge noise control” in the American Institute of Aeronautics and Astronautics Journal and “Bio-inspired canopies for the reduction of roughness noise” in the Journal of Sound and Vibration.  These efforts not only include more precise measurements than earlier efforts, but led to a practical product for real-world applications.

Siemens’ Owl-like Feathers

Siemens has a totally practical intent for their trailing edge treatment of wind turbine blades.  The company called their owl-like appendage “DinoTail,” soon to be in serial production according to the company.  Siemens credits the need for near-silent operation of wind turbines to make them acceptable for on-shore operation.  Improved aeroacoustic performance should allow wind turbines greater latitude in placement around otherwise off-limits population centers.  The technology can also allow pulling greater production without increasing noise.

Vortex generators on the forward part of the blade, combined with a “combination of serrations and combs” on the trailing edge of each blade, “creates fine vortices at the point where the fast air stream from above the blade profile meets the slower flow from below. As a result, the aerodynamic noise from the trailing edge of the blade is reduced significantly.”

Siemens DinoTail, a bit coarser than Jaworski's trailing edge, but designed for large-scale turbine blades

Siemens DinoTail, a bit coarser than Jaworski’s trailing edge, but designed for large-scale turbine blades

At the Wind Energy Hamburg 2016 trade show, Stefan Oerlemans, Key Expert in Aeroacoustics with Siemens Wind Power, explained, “This structure that was inspired by owl wings does not compromise the aerodynamic performance.”  Since the combed teeth are a second generation of the original DinoTail add-ons, they will replace the original items on onshore wind turbines, and on future new models.

A high level of biomimicry seems like a good way to advance aeronautics and efficient capture of wind energy.  The birds, especially wise old owls, have been doing it right all along.


EC04 Design Wins 2016 Berblinger Prize

A Big Win for Stuttgart Team

Dipl-Ing Ingmar Geiß, Deputy Project Leader for e-Genius at the Institute of Aircraft Design at the University of Stuttgart, shared this pleasant news:  “I am happy to tell you that our hybrid-electric “ECO4” has won the Berblinger Prize 2016.  ECO4 combines an optimized electric airframe with a modern combustion engine generating electricity. This combination leads to an aircraft which cruises at 120 knots and consumes 40 percent less fuel than comparable state-of-the-art airplanes with conventional propulsion. As a further advantage, a small but powerful battery system enables a silent take-off without the combustion engine running, reducing significantly the noise emissions.”

EC04's configuration is similar to that of Icare, e-Genius

EC04’s configuration is similar to that of Icare, e-Genius

The Berblinger Prize

Gunter Czisch, mayor of Ulm, presented the 23,000 euro ($24,035 US) prize to the team, which intends to invest the amount “directly into the further development of the airplane.”  The prize was founded in recognition of Albrecht Ludwig Berblinger, “the little tailor of Ulm, who tried to cross the river Danube in 1811 with a glider.  Although capable of flying, his glider crashed due to severe turbulence.  A jury of 16 members from aerospace industry, universities, research institutions and representatives of the town of Ulm decide the winner.

Stuttgart team with Berblinger Prize. Ingmar Geiss is front row left

Stuttgart team with Berblinger Prize. Ingmar Geiss is front row left

A Masterful Design

Part of Ingmar’s Master’s Degree program, EC04 represents an expansion of his earlier work with e-Genius, the two-seat, battery-powered craft that won second place in the 2011 Green Flight Challenge.  e-Genius has since been flown by Klaus Ohlmann to set several records and undertake long cross-country flights.  Extending that range, a new pod holding a Wankel engine and generator allows flight up to 620 miles, well beyond the comfort range of most pilots.

EC04 will increase the range to 1,200 nautical miles – with four persons on board (1,800 miles with three up).  EC04 will have a quiet takeoff distance of 600 meters (1,968 feet) and a climb rate of five meters per second (984 feet per minute).  Considering its 45-kilowatt (60 horsepower) Diesel-powered generator, predicted performance is remarkably similar to that of a 180-horsepower Cessna SkyhawkA Cessna 172M at 75-percent power, cruising at 8,000 feet, will burn through its 38 gallons of useable fuel in 4.7 hours, according to the Cessna 172 Guide.  That’s a fuel burn of 8 U. S. gallons per hour.

EC04 has tricycle gear, easy entry to what looks to be a roomy cabin

EC04 has tricycle gear, easy entry to what looks to be a roomy cabin

The EC04 would supposedly represent a 40-percent savings, making its equivalent fuel burn 4.8 gallons per hour, for an economy of 28.75 mpg, or 115 passenger miles per gallon.  Your editor will be happy to be corrected or updated on these back-of-envelope figures, since these seem low compared to what the HY4 and e-Genius manage.

A Strong History

EC04 continues the long-term work of Professor Rudolf Voit-Nitschmann, who developed the motor on vertical stabilizer configuration with Icare 2, a solar-powered craft that first flew in 1996.  E-Genius continued with this configuration.  At the 2011 Green Flight Challenge, the Professor explained to your editor that the propeller’s placement allowed low drag, its blast impinging only on the upper part of the stabilizer and rudder.  E-Genius has proven itself for the last five years with increasingly long flights, the latest powered by a hybrid system similar to that proposed for EC04.


Compressed natural gas (CNG) has several things going for it.  It is cheaper than gasoline or diesel fuel, has lower emissions, and for a conventional piston-engined airplane, is the equivalent of over 130 octane, far more powerful than 100-octane low lead (100LL) and cleaner burning.

CNG Fuels in England

CNG filling stations are growing across the country as fleet owners take advantage of the economics of converting their vehicles, but are still few and far between in the west, with the exception of California.  There are under 900 stations throughout America.  Alluring as CNG might be for drivers, pilots used to paying $5.50 per gallon for avgas should be charmed by CNG’s price of $1.00 per gallon equivalent.

That is with conventional, fossil-based CNG, basically a storable version of natural gas.  That leads to its less-desirable characteristics.  First, it pollutes, too, and is a source of greenhouse gases.  Second, natural gas has a hard time overcoming its association with fracking, or hydraulic fracturing – the injection of water, chemicals and sand into rock that contains natural gas.  This forces gas from the fractured seams for collection.  But it also leaves the underlying shale or rock formation weakened – possibly leading to earthquakes.  Oklahoma, which has a disproportionate number of CNG distribution stations, also has a recent uptick in temblors.  Beyond that, groundwater pollution is often associated with fracking and natural gas extraction.

Biomethane can be readily added to pipeline supplying CNG's pumps throughout England

Biomethane can be readily added to pipeline supplying CNG’s pumps throughout England

A non-fossil version of CNG would seem desirable.  GNG Fuels in England is working on that, along with a distribution network that takes advantage of existing supply lines.  Claiming to be the UK’s leading supplier of CNG, GNG Fuels now sources its entire production from biomethane.  The company explains, “The biomethane is made from the gas harvested through the processing of waste generated by food production, which is then injected directly into gas pipelines. The gas is subsequently compressed at CNG Fuels’ own high-capacity refueling stations in Leyland (Lancashire) and Crewe (Cheshire).”

We’ve discussed liquid jet fuels made from municipal and farm waste in recent entries, and both United and Alaska Airlines have made flights fueled partly with non-fossil materials even forest slash debris.

Economics and Environment

United Kingdom-based CNG Fuels purveys a renewable biomethane fuel, which they claim to be ”The most cost-effective and lowest-carbon alternative to diesel for heavy goods vehicles (HGVs). The fuel is 35%-40% cheaper than diesel, and emits 70% less CO2 on a well-to-wheel basis. It therefore offers fleet operators the chance to significantly reduce running costs and emissions.”  Several British trucking firms have committed to using the new biomethane fuel for their long-distance haulers.

CNG reports, “The biomethane is independently verified as renewable and sustainable, and approved under the Department for Transport’s Renewable Transport Fuel Obligation (RTFO) scheme.”

At 65 p (pence or $0.83 US) per kilogram, bio-CNG is equivalent to paying 49p per liter ($0.62/liter, or $2.35/gallon US) for diesel.  Compare this to current prices for “diesel petrol,” currently at 117 p per liter ($1.25), or the equivalent of $.84 per U. S. gallon.  This low price is without government subsidies, making the economics even more attractive.  Apparently, the biomethane, made in waste treatment facilities that break down organic matter, is “not supported by the Renewable Heat Incentive or other subsidy schemes.”

Distribution and Economics

England is small enough, and with an established high-pressure gas grid, that adding a network of refueling stations is reasonable and economically feasible for CNG.  Whether operators will find the economics reasonable is another question.  GNG “is targeting operators of high-mileage HGVs, who stand to make the biggest financial savings and carbon impact. Its customers’ vehicles travel an average of 125,000 miles every year, and CNG-powered trucks are more expensive than those that use diesel.

”However, for HGVs covering this mileage, fuel savings can recoup the extra cost within around two to three years. Furthermore, CNG fuel-powered engines meet the latest Euro 6 emissions standards, and are up to 50% quieter than diesel engines.”

Ford has sold a good many CNG/propane vehicles over the past decade, with sales growing annually.  After paying for a $315 factory prep, a customer can take his large pickup to a “Ford Qualified Vehicle Modifier,” who will install the dual-fuel package for $7,500 to $13,000.  Most who own big-rig pickups in commercial operations put enough miles on to justify the conversion costs.

That price differential for storing compressed gas led to Honda’s attempt at a Civic using LNG/CNG to disappear quietly from the market.  Its higher initial cost, indifferent performance, and lower fuel economy did not endear it to consumers.

Natural Gas Airplanes?

Russia’s Tupolev works attempted a hydrogen-powered airliner, the TU-155, in 1988, converted it to natural gas, but dropped the project with the fall of the Soviet Union.

TU-155 went away with Soviet Union

TU-155 went away with Soviet Union


Aviat’s Dual-Fuel CNG Demonstrator

Seen at Oshkosh in 2014 outside the Innovation Pavilion, Aviat’s Husky with a large bulge underneath was flown on both 100 low-lead (LL) aviation gasoline and compressed natural gas.  In a recent call to Bill Sullivan, he explained that the airplane had been an “engineering challenge,” but has not been offered for sale since its public display.  He’s flown it on 100LL, and noted that CNG offered the equivalent of 130 octane.  An engine would need higher-compression pistons and other modifications to take full advantage of the added potential of the fuel.  The lack of lead in CNG might also produce great wear in the engine, that “LL” feature in aviation gas necessary for extending engine life.

Questioned about the bulky fuel container, Sullivan explained that was a first-generation tank, and that later improvements had condensed that bulk considerably.  We’re on the fifth generation currently.  Range would be limited to what could be done on that single tank, since other airports in the region might not have GNG available.  An entirely new infrastructure would be required to allow anything other than training flights mostly kept close to the departure airport.  In this respect, CNG trainers would be restricted much like Pipistrel’s Alpha Electro trainer (until better batteries become available).

What to Do?

If GNG can be made even cleaner by adding or substituting biomethane, several advantages accrue, including fewer emissions from the vehicle and less methane being released into the atmosphere from rotting plant matter.  The fuel can be less expensive, but the necessity of modifying the vehicle to take advantage of that can be off-setting.  This may be more easily accomplished in a compact, heavily agricultural land such as England, but harder to pull off in the far-flung reaches of America.

As gas prices rise again (predicted to top $3.00 a gallon again early in 2017), fleet owners and airline magnates will look at economical solutions more favorably.  Given changes in the political infrastructure, we might be surprised at the next turn in our ongoing story.

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SolarStratos Unveils a High-flying Motorglider

Raphael Domjan is an adventurer in every sense of the word.  He’s sailed around the world on solar power, and attempted to paddle his way across the Northwest Passage in a solar-powered kayak. And now, he’s revealed an airplane that could carry him to the stratosphere on solar power.

SolarStratos is a 24.9-meter (81.7 feet) span motorglider shown to the public for the first time yesterday in Payerne, Switzerland.  With stage smoke and rock-concert lighting glittering from the solar cells on its wings and tail, the Calin Gologan-designed craft materialized before the crowd of 400 (according to Calin) gathered in the specially-built hangar.

Raphael Domjan’s stratospheric solar plane was unveiled December 7 in Payerne, Switzerland, to 300 guests, including ambassadors, partners, government representatives and the world’s media. Photograph courtesy of SolarStratos

Raphael Domjan’s stratospheric solar plane was unveiled December 7 in Payerne, Switzerland, to 300 guests, including ambassadors, partners, government representatives and the world’s media. Photograph courtesy of SolarStratos

At a loaded weight of only 450 kilograms (990 pounds), SolarStratos should climb well on its dual motor, a mere 19 pounds itself.  A planned flight time of approximately five hours to take pilot and passenger to the planned 75,000 foot, near-space experience.  On only 42.8 horsepower swinging a 2.2-meter (7.2-feet), four-bladed propeller, this is, outside of the Perlan Project’s sailplane or high-altitude balloons, perhaps the lowest power of any record altitude attempt.

Where Perlan uses a pressurized cabin to protect its occupants and permit them to (we hope) breathe easily, SolarStratos has an unpressurized cabin, but with elbow room to allow movement even with occupants in bulky pressure suits.

Calin further explained that “Our two companies, PC-Aero GmbH (Manned applications) and Elektra-UAS GmbH (autonomous and remotely-piloted flight) merged in Elektra Solar GmbH which is now officially a spinoff from DLR ( German Aerosoace Center), Institute of Robotics and Mechatronics.”

The combination of high adventure and high technology has led to a beautiful aircraft with an ambitious flight plan.  We wish them the greatest of fortunes.


A New Twist on Retractable Motors

GP Sailplanes in Poland recently partnered with MGM Compro of the Czech Republic to add electric power to its line of small, sleek sailplanes.  Concentrating initially on the 13.5 meter racing class (44.29 feet), GP’s craft provide high performance with light weight and compact dimensions.

A Long Reach on the Antares

Putting a retractable motor and folding propeller into such a tight space required some clever engineering.  Think of the tall mast on the Lange Antares or the Arcus two-seater.  These are large, heavier machines, so the propeller, mast and motor can be accommodated (tightly) in their fuselage.  The video gives a good view of just how close the quarters are on the Antares at about the 3:14 mark.  With a 118-square-foot wing area and 59-foot wing span (the 18T model), the average chord of the Antares is two feet.

Tucking the Motor into a Tighter Space

GP’s aircraft are much smaller, with narrow chord wings, part of their high aspect ratios.  That gives a smaller center of gravity range.  RecreationalFlying.com suggests not exceeding a CG range of 20 percent – less than eight inches on a typical trainer.  For the Antares, that range is less than five inches.  The GP14 SE has a mean aerodynamic chord of about 20 inches, so the CG range is closer to four inches.  Constrained by a need to keep CG travel to a minimum, the designers came up with an ingenious solution, something they label RESLS – retractable electric self launching system.

A Lightweight, Compact Package

Weighing only 374 pounds (170 kilograms) empty and 924 pounds at maximum takeoff weight, the GP14 should perform well with its 25 kilowatt (34.5 horsepower) Rotex motor.  The four kilowatt-hour Sony Li-ion battery pack is 44 pounds of the empty weight, and it’s possible to add four kW-hr or two kW-hr packs to extend endurance.  Since these fit in the wings, the center of gravity is not affected.  Wide-body pilots can fit into the standard fuselage, but those lucky enough to be of lower heft can have a slim fuselage option, making the plane perform even better.

Thanks to Martin Dvorsky of MGM Compro for alerting your editor to this news.


5X Lithium Sulfur Battery with a Gut Feeling

Bio-mimicry presents itself in aerodynamics, from the emulation of soaring bird’s wing shapes on sailplane’s surfaces to owl-feather-like trailing edges on wind turbines.  We don’t often think of biological equivalents in energy storage (your editor didn’t until now, at least).  But researchers at Cambridge University in England and the Beijing Institute of Technology in China have turned to the small intestine for their breakthrough in battery development.

Tiny cells lining the human intestine inspired these researchers to develop a prototype of a lithium-sulfur battery that they claim could have five times the energy density of conventional lithium-ion batteries.  Dr. Paul Coxon from Cambridge’s Department of Materials Science and Metallurgy says “This gets us a long way through the bottleneck which is preventing the development of better batteries.”

Is That You, Villi?

Structure of villi in the small intestine

Structure of villi in the small intestine

Villi in the gut help process food being digested, trapping nutrient particles in millions of tiny, “finger-like protrusions” which increase the absorbent surface area over which digestion takes place.  In batteries, surface area enables greater electrochemical reaction between anodes, cathodes and electrolytes.

Dr. Vasant Kumar and his Cambridge team created and tested a lightweight nanostructured material with tiny zinc-oxide wires, which they placed on the battery’s electrodes.  According to researchers, “This can trap fragments of the active material when they break off, keeping them electrochemically accessible and allowing the material to be reused.”  This prevents loss of active materials and increases the life span of the battery.

How This Works in a Lithium-Sulfur Battery

A typical lithium-ion battery is made of three separate components: an anode (negative electrode), a cathode (positive electrode) and an electrolyte in the middle. The most common materials for the anode and cathode are graphite and lithium cobalt oxide respectively, which both have layered structures. Positively-charged lithium ions move back and forth from the cathode, through the electrolyte and into the anode. Illustration: Futurism.com

A typical lithium-ion battery is made of three separate components: an anode (negative electrode), a cathode (positive electrode) and an electrolyte in the middle. The most common materials for the anode and cathode are graphite and lithium cobalt oxide respectively, which both have layered structures. Positively-charged lithium ions move back and forth from the cathode, through the electrolyte and into the anode. Illustration: Futurism.com

Different materials determine how much energy can be squeezed into the battery.  Carbon electrodes can take on six lithium ions per carbon atom.  Sulfur can take on many more, making the battery theoretically more energy dense.  At least five times more so, if we’re to believe the Cambridge/Beijing researchers.  That’s where there the electronic villi come into action.

Mimicking Our Inner Workings

During discharge, when we get the stored energy back as work, “The lithium and sulfur interact and the ring-like sulfur molecules transform into chain-like structures, known as a polysulfides. As the battery undergoes several charge-discharge cycles, bits of the polysulfide can go into the electrolyte, so that over time the battery gradually loses active material.”

To emulate the work villi do in the body, researchers “Have created a functional layer which lies on top of the cathode and fixes the active material to a conductive framework so the active material can be reused. The layer is made up of tiny, one-dimensional zinc oxide nanowires grown on a scaffold. The concept was trialled using commercially-available nickel foam for support. After successful results, the foam was replaced by a lightweight carbon fiber mat to reduce the battery’s overall weight.”

Study co-author Dr. Yingjun Liu explained, “Changing from stiff nickel foam to flexible carbon fiber mat makes the layer mimic the way small intestine works even further.”The high surface area exposed on the fingers and its strong chemical bond with the polysulfides allows the material to last longer, and increases the lifespan of the battery.

“This is the first time a chemically functional layer with a well-organised nano-architecture has been proposed to trap and reuse the dissolved active materials during battery charging and discharging,” said the study’s lead author Teng Zhao, a PhD student from the Department of Materials Science & Metallurgy. “By taking our inspiration from the natural world, we were able to come up with a solution that we hope will accelerate the development of next-generation batteries.”

Not So Fast

Alas, as with so many such developments, things done at laboratory scale sometimes take another decade to reach commercial reality.  Talk of Manhattan Project levels of investment and urgency never seem to gain ascendancy for peace-time endeavors.  Let’s hope this and similar efforts find willing investors.

See the researchers’ results in the October 26, 2016 edition of Advanced Functional Materials


Gleaning the Forests for Jet Fuel

Three congresspeople flew on wood-waste fumes this week, aboard an Alaska Airlines Boeing 737-800 on its way from Seattle-Tacoma International Airport (SEATAC) to Washington, DC.  It was the first commercial flight to “to be powered by a blend of renewable jet fuel made from forest residuals.

20-percent alcohol-to-jet (ATJ) fuel made from forest waste goes into Washington, DC-bound 737-800

20-percent alcohol-to-jet (ATJ) fuel made from forest waste goes into Washington, DC-bound 737-800

Waste Products Replace Fossil Fuels

Alaska, Boeing, and SEATAC have partnered on including biofuels in the mix since early 2015, as reported here.  Later that year, United made flights out of Los Angeles International (LAX) using a blend of fossil-based jet fuel and biofuels made from farm and municipal waste.  Keeping waste out of landfills and producing a lower carbon-footprint fuel has several benefits.  In the case of forest waste, those branches, limbs and twigs that litter the forest floor after a timber harvest, cleaning that debris away lowers fire risk in the warm seasons and makes renewable isobutanol.

Developed through a five-year project led by Washington State University and the Northwest Advanced Renewables Alliance (NARA) initiative and the U. S. Department of Agriculture, the program is now nearing completion.  This first flight on the 1,080 gallons produced so far marks a practical demonstration of the fuel’s viability.

Funded with $39.6 million grant from the National Institute of Food and Agriculture (NIFA)  “To support research on biofuels and biochemical, foster regional supply chain coalitions, empower rural economic development and educate the public on the benefits of bioenergy,” the project comprises 32 member organizations from industry, academia and government laboratories.

Good Enough for Dignitaries

GreenAir quoted some distinguished passengers.  “Three members of the House of Representatives were on the flight, including Congresswoman Suzan DelBene. ‘This flight demonstrates that Washington state’s innovation economy is once again at the forefront of collaborative, transformative research by using material that would otherwise be discarded to create a new biofuel,’ she said. ‘We have a tremendous opportunity in our region to build a new green economy and find innovative solutions to address climate change for our health and future generations, as this project highlights.’”

“US Senator for Washington, Maria Cantwell: ‘The flight comes after years of investments to help the aviation biofuels industry take off. By creating these sustainable biofuels, we will revitalize our rural agriculture communities, foster economic growth, reduce greenhouse gas emissions and cur our dependence on foreign oil while growing our competitiveness in global markets.’”

NARA Executive Director Ralph Cavalieri said, “This flight is a tribute to all of our NARA partners, and especially to NIFA who supported our mission to facilitate the revolutionary development of biojet and bioproduct industries in the Pacific Northwest using forest residuals that would otherwise become waste products.”

Gevo CEO Pat Gruber added, “We are pleased that we had the opportunity to prove, through the NARA project, that cellulosic sugars from wood can be used to successfully make commercial jet fuel.”

Gevo lab workers in Englewood, Colorado test wood-based fuel

Gevo lab workers in Englewood, Colorado test wood-based fuel

 GreenAirOnline reports, “Alaska and Gevo have already partnered on commercial biofuel flights from Seattle to San Francisco and Washington DC in June this year that used a 20% Alcohol to Jet (ATJ) blend derived from sustainable non-edible field corn grown in South Dakota.”

Alaska Airlines Senior Vice President for Communications and External Relations, Joe Sprague, said the biofuel used on yesterday’s flight was “especially exciting since it is uniquely sourced from forest residuals in the Pacific Northwest.”

Obviously, one flight with 20-percent biofuel will not cure rising emissions, but “the airline said if it were able to replace 20% of its entire fuel supply at Seattle-Tacoma, it would reduce CO2 emissions by about 142,000 tons per year.”


A 24-Volt Airplane Motor?

One of the big surprises in last month’s webinar hosted by the EAA and presented by Brian Carpenter of Rainbow Aviation Services/Adventure Aviation was the 24-Volt motor being developed for the EMG-6 ultralight motorglider.

EMG-6 in side view with electric powerplant - still Part 103 legal, according to Brian Carpenter

EMG-6 in side view with electric powerplant – still Part 103 legal, according to Brian Carpenter

High and Low Voltages

Many, if not most of the electric motors flying on existing craft are higher voltage units.  For sake of an off-handed definition, we’ll divide low and high at below and above 50 Volts, something OSHA delineates in its regulation 29 CFR 1910.303(g)(2)(i), which “generally requires “’live parts of electric equipment operating at 50 volts or more’ to be ‘guarded against accidental contact by use of approved cabinets or other forms of approved enclosures’ or by other specified means.”  In its explanation, the Occupational Safety and Health Administration “considers all voltages of 50 volts or above to be hazardous. Electric current, not voltage, passing through the human body causes injury….”

And it really doesn’t take much amperage to take a person to the next realm.  Electric chairs, for instance, pass voltages from 500 to 20,000 Volts through the condemned’s body, but at currents of only five to 20 Amperes.  Shockingly, “A current of 0.070 ampere causes heart problems and may be fatal.”  The lesson is that all electric devices need to be treated with caution and respect.

While high power in aircraft electric motors comes from a combination of high voltages and high amperages (multiply the two to get the kilowatt output of the motor), Roman Susnik and EMRAX provide three voltage levels with correspondingly varied amperages to suit motors to different applications.

The Emrax 228, for instance, can be ordered in high, medium and low voltage configurations.  The high-voltage version can handle up to 600 Volts at a maximum current of 240 Amps.  The low-voltage model can run on 24 to 150 Volts, but at 900 maximum Amps.  Because the resulting torque is so great from especially the low-voltage motors, they can swing large propellers at low RPMs while providing significant thrust.  Certainly the early demonstration of low-speed torque shows low noise and an undocumented level of thrust at 450 RPM.  Most Emrax motors don’t exceed 2,200 RPM at full power.

A 48-Volt Automobile

A European car manufacturer, NanoFlowCell, produces two vehicles, the Quant F and Quantino, powered by liquid flow cell batteries.  The Quantino has four wheel-hub type 48-Volt motors, each capable of producing 200 Newton-meters (147.5 foot-pounds) of maximum torque.  We’ve covered the Quant in an earlier post.

This 48-Volt car ran 14 hours on a very level, smooth floor and still had 78-percent of the energy stored in its two 159-liter (84 gallons) tanks available, according to the company.  This demonstration, while impressive, is somewhat like Sanyo’s battery-powered six-year-old, 1,000 kilometer run without a recharge.  Run at 25 mph, Sanyo’s record was not a big challenge for even the draggiest vehicle.  It’s unlikely the Quantino went much faster, considering the confined quarters.

Salt water weighs about 8.5 pounds per gallon, so the Quantino is lugging around 714 pounds of motive power.  It has the same issue that batteries have, not diminishing in weight as the energy burns off.  Any car or airplane using either energy storage medium ends its journey as heavy as when it started.

48-Volt systems are becoming common in so-called “mild” hybrids with stop-start capabilities, but coming into their own as full-time powerplants for electric vehicles.  Beyond that NanoFlowCell warns of the “spectre” high-voltage dangers.

A 24-Volt Airplane Motor

Brian Carpenter has tried several electric motors on his EMG-6 motorglider, and is planning the first runs for the R&D motor developed in collaboration with that company.  The 24-Volt motor would turn a big propeller slowly, just as the Polini two-stroke also tested on the airplane manages.  A large, slow propeller is great for quick climbs to gliding altitude, and a battery pack can then be used intermittently to search for thermals or assure a return to the field.

Collaborating with Ed Donovan at R&D Cable, Brian describes the prototype motor as a good alternative to two-strokes, even borrowing small parts from them.  “The bolt pattern is the standard two-stroke Rotax engine bolt pattern. the bearing is the same as the front bearing on the Rotax E gearbox. The total motor weight will be in the neighborhood of 25 pounds when completed. There are 6 mounting locations on the rear of the motor housing. During testing at full power the outer housing gets slightly warm but the windings and the magnets remain cool even at full power operation. They are still undergoing some operational tests on the motor and perfecting the final design before going into the mass production phase and developing the tooling for the stamping dies for the winding core. The expectations are that the efficiency of the motor will exceed 95%. And reliability and durability are key components in the development of the motor. I would expect that this motor will have a TBO in excess of 10,000 hours. And overhaul cost will be the replacement of 2 bearings. We have been told that we should expect to have an operational motor available for installation before we depart for the Oshkosh airshow.”

Brian Carpenter mounting R&D motor. Note wide blades on 48-inch propeller, Alternative three-blade Sterna propeller is also under test

Brian Carpenter mounting R&D motor. Note wide blades on 48-inch propeller, Alternative three-blade Sterna propeller is also under test

If the high-torque ability to swing a propeller slowly in a high=thrust way turns out to combine the (relative) safety of low voltage with the ability to scramble for altitude, this may move more designers to opt for the low-voltage option.

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