HZB Makes H2 With Fool’s Gold

Hydrogen, two atoms of which are in every molecule of water, is wildly abundant, but elusive to extract for our transportation needs.  Common means of pulling the H2 from the H2O used fossil fuels, and thus negate the good intentions for its use.  Several people have tried cleaner means of “splitting water,” including Daniel Nocera of MIT and Harvard, and researchers around the world, including those in the Netherlands and Germany.  One notable recent accomplishment at the HZB (Helmholtz Zentrum Berlin) Institute for Solar Fuels involves a new composite photocathode that generates H2 “with high quantum efficiency” using sunlight.

The Institute says, “The photocathode consists of a thin film of chalcopyrite produced by HZB/PVcomB coated with a newly developed thin film of photo-resistant titanium dioxide (TiO2) containing platinum nanoparticles.”

Layering of HZB artificial photosynthesis photocathode

Layering of HZB artificial photosynthesis photocathode

Of course your editor, who wishes he had taken better notes in chemistry class, Googled the unfamiliar term.  A University of Michigan note on CuFeS2 – Copper Iron Sulfide explains, “Chalcopyrite was the mineral upon which Bronze Age civilizations were built. Within the last century, it also became the mineral foundation for our modern electrical age. Our primary source of copper, chalcopyrite’s name comes from the Greek words ‘chalkos’ and ‘pyrites’, which respectively mean ‘copper’ and ‘striking fire’. With its metallic luster and bright golden color, chalcopyrite can fool people into thinking it is gold. It is one of two minerals, the other being pyrite, that are commonly known as ‘fool’s gold’”.

With its pricey components, the layer covering the chalcopyrite film protects it from corrosion and acts as a catalyst, speeding formation of hydrogen and acting as a photodiode showing “photoelectric current density and voltage comparable to those of a chalcopyrite-based thin film solar cell.”

Electrodes used in splitting water, such as platinum or platinum-iridium alloys, are usually from the pricier side of the periodic table.  Despite the platinum nanoparticles in the coating over the chalcopyrite, the “fool’s gold” photocathode helps keep the price of these devices in a moderate range.

The polycrystalline TiO2 film contains a small amount of platinum in the form of nanoparticles, and produces “under sun light illumination a photovoltage of almost 0.5 volts and very high photocurrent densities of up to 38 mA/cm2; secondly, it acts as a catalyst to accelerate the formation of hydrogen, and finally, it is chemically protected against corrosion as well.”

The coating, developed by Anahita Azarpira during her doctoral studies in a team headed by Assoc. Prof. Thomas Schedel-Niedrig, uses a chemical vapor coating technique (sprayed ion-layer gas reaction/Spray-ILGAR) developed and patented at the HZB Institute for Heterogeneous Material Systems (EE-IH).

To make the coating , “titanium dioxide and platinum precursors are dissolved in ethanol and converted to a fog using an ultrasonic bath.”  As shown in the video, the “fog” spreads over the heated chalcopyrite substrate and “grows” a thin film in time, coating the substrate and embedded platinum nanoparticles.

Azarpira and her colleagues varied the amount of platinum in the precursor solution to optimize the properties of the novel composite photoelectrode device, finding best performance with about five-percent platinum (H2PtCl6) in the precursor solution   Schedel-Neidig reports, “ More than 80 percent of the incident visible sunlight was photoelectrically converted by this composite system into electric current available for the hydrogen generation, ” losing little light and attaining a high quantum efficiency.

That means little light is lost and the quantum efficiency is virtually very high. A recent article reports the composite shows high long-term stability over 25 hours and reveals large photoelectrocatalytic activity of about 690 hydrogen molecules produced per second and per active center at the surface under illumination.

As with all such research, much remains to be done.  1.8 Volts required between the composite photocathode and a platinum counter electrode still comes from a battery. Hence the solar-to-hydrogen efficiency has to be clearly improved.

Schedel-Niedig remains optimistic, saying the team “demonstrate[d] the feasibility of such future-oriented chemical robust photoelectrocatalytic systems that have the potential to convert solar energy to hydrogen. “ Working with a company in Schwerin, the team developed and tested a demonstrator device for solar hydrogen under the Light2Hydrogen project.

The team reports on their research in their paper, “Efficient and Stable TiO2:Pt-Cu(In,Ga)Se2Composite Photoelectrodes for Visible Light Driven Hydrogen Evolution. “ in the journal, Advanced Energy Materials.

Authors include Anahita Azarpira, Michael Lublow, Alexander Steigert, Peter Bogdanoff, Dieter Greiner, Christian A. Kaufmann, Martin Krüger, Ullrich Gernert, Roel van de Krol, Anna Fischer, and Thomas Schedel-Niedrig.

The abstract for that paper reads: “Novel thin film composite photocathodes based on device-grade Cu(In,Ga)Se2 chalcopyrite thin film absorbers and transparent conductive oxide Pt-implemented TiO2 layers on top are presented for an efficient and stable solar-driven hydrogen evolution. Thin films of phase-pure anatase TiO2 are implemented with varying Pt-concentrations in order to optimize simultaneously i) conductivity of the films, ii) electrocatalytic activity, and iii) light-guidance toward the chalcopyrite. Thereby, high incident-photon-to-current-efficiencies of more than 80% can be achieved over the full visible light range. In acidic electrolyte (pH 0.3), the most efficient Pt-implemented TiO2–Cu(In,Ga)Se2composite electrodes reveal i) photocurrent densities up to 38 mA cm−2 in the saturation region (−0.4 V RHE, reversible hydrogen electrode), ii) 15 mA cm−2 at the thermodynamic potential for H2-evolution (0 V RHE), and iii) an anodic onset potential shift for the hydrogen evolution (+0.23 V RHE). It is shown that the gradual increase of the Pt-concentration within the TiO2 layers passes through an efficiency- and stability-maximum of the device (5 vol% of Pt precursor solution). At this maximum, optimized light-incoupling into the device-grade chalcopyrite light-absorber as well as electron conductance properties within the surface layer are achieved while no degradation are observed over more than 24 h of operation.”

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Singapore Firm, Boeing Team Up on Hydrogen

EV World reports that a Singapore-based company, Horizon Energy Systems, has test flown the world’s first hydrogen powered quadracopter, a small UAV that is claimed to fly for hours, instead of the minutes a lithium battery pack would provide.

The report asks that tantalizing question for all who suffer from range anxiety, especially while in flight.  “What if you could increase flying time by a factor of ten? Instead of half-an-hour, you could keep the UAV flying for five hours, and then charge it in a couple minutes time? That’s what Singapore-based Horizon Energy Systems is promising. They have developed micro fuel cells that can be fueled by three types of hydrogen storage systems from small compressed gas cylinders to ‘on-demand’ hydrogen generation chemical cartridges rated at 700 Watt-hours per kilogram (Whr/kg), significantly higher than the best lithium batteries.”

Horizon's Hycopter can fly for hour on a dollop of hydrogen

Horizon’s Hycopter can fly up to four hours on a dollop of hydrogen

Horizon’s Hycopter micro UAV quadracopter stores 120 grams (0.26 pounds) of hydrogen in its structure, equivalent to three kilograms (6.6 pounds) of lithium batteries. According to EV World, “Since the Hycopter has less weight to lift, it can fly longer: the company claiming up to four hours of flight time.”

As noted above, Horizon Energy Systems produces three different approaches to storing H2:

  1. Gaseous fuel storage of compressed hydrogen. This option costs $1 per hour for 200 Watts, and offers the least system complexity if there is enough room in the airframe to accommodate the tanks.
  2. “On demand” hydrogen generation using liquid chemical cartridges. This option offers the same energy available but in half the volume of the tanks of compressed H2.  It’s also slightly lighter and “loses” the weight of fuel as it is consumed.  This, of course, would be important in a small UAV, which might weigh no more than a few pounds.
  3. “On demand” hydrogen generation using solid chemical cartridges. Horizon explains that there are no catalysts required, and the chemicals offer unlimited storage duration.

From their specification sheet, we see that a one kilowatt AeroStak system, complete with controller, would weight 2.25 kilograms, or 4.95 pounds.  The system also requires an external 36 Volt power supply. Stack size of the 50-cell unit is 252 x 126 x 190 millimeters (9.92 x 4.96 x 7.48 inches).  Advertised as “10 times lighter and smaller than other Horizon fuel cells,” how do Aerostaks stack up against lithium-ion batteries?

Your editor chose to make a 10 kW stack as a comparison unit for the Eck-Geiger lithium-ion battery pack used in many ultralight motorgliders, such as the Swift.  10 one-kW stacks could be arranged as a block about 10 x 15 x 7.5 inches, or possibly in a string that could be 100 x 5 x 7.5 inches, or in other configurations that would fit into an airframe.  We’ll stick with the first arrangement, since that comes close to the Flytec’s battery module size.

Using Horizon’s ratio of 0.26 pounds of hydrogen equaling 6.6 pounds of lithium batteries (energy density unspecified), it would take about 2.16 pounds of stored H2 to equal a Flytec 100 Amp-hour battery pack weighing 25 kilograms (55 pounds), according to Flytec’s 2015 listings.

This would give over an hour’s flight, based on Gerard Thevenot’s flight across the English Channel in 2009.  His La Mouette hang glider used the Eck-Geiger HPD-10 motor and consumed 550 grams, or about 1.3 pounds of hydrogen per hour.  2.16 pounds of H2 would have provided 1.66 hours of flight, a comfortable margin for that 22-mile trip.

It’s hard to judge whether the Horizon systems would give a 10-fold increase in endurance over batteries – the numbers don’t seem to indicate quite that, but the system does allow clean running, even though at this point, possibly higher operating costs than lithium batteries.  Their quoted $1 per hour for 200 Watts would equal $50 per hour for the full output of a 10 kW motor.

Such stacks and their attendant hydrogen-generating systems could be used as the sole means of powering an aircraft, or possibly in conjunction with a conventional battery pack as a range extender.  Depending on unit cost and availability, Horizon Energy Systems’ packs may provide an alternative worth exploring, although one may be tempted to find a cheaper fuel source.

Being thinks it’s worth exploring, although in a context where expenses may not be a primary concern.  As these things become more common, costs will probably come down, and that will be a benefit to all of us.

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Salting the Battery

Ideally, battery materials should be abundant, cheap, and safe.  NaCl (salt) seems to manage three out of three of these, but can it manage the energy and power density of less abundant and more expensive materials such as lithium?

Faradion, an English enterprise specializing in “advanced energy storage solutions,” thinks that the salt of the earth may indeed be part of the secret sauce in their new battery.  Initial applications will probably be in large energy-storage systems associated with renewable energy, but forward-looking statements (we used to call them predictions) show the potential for lighter, smaller batteries that could compete with lithium-ion cells.

Faradion foresees energy and power densities competitive with the best lithium-ion batteries

Faradion foresees energy and power densities competitive with the best LiFePO4 batteries

Since the introduction of new technology does not usually come from a single source, Faradion is partnered with co-funders Innovate UK, the UK’s innovation agency; Williams Advanced Engineering and the University of Oxford.

The group is building 3 Amp-hour prismatic cells “containing Faradion’s novel cell chemistry, and are being incorporated into battery packs by Williams.”  This will require no major changes in existing battery manufacturing lines.

Faradion’s chairman, Chris Wright, explains.  “Sodium‑ion does everything lithium‑ion does, but cheaper,” he says. “If a manufacturer already has a lithium‑ion plant, there is no incremental capital cost because it uses the same equipment. According to Argonne National Lab’s BatPaC data model, a 16kWh sodium‑ion pack is 30% cheaper.”

Faradion 12-cell module with battery management system (BMS)

Faradion 12-cell (3 Ah each) module with battery management system (BMS) designed by Williams Advanced Engineering

In Faradion’s PowerPoint presentation on Na-ion batteries, lithium forms about 0.005 percent of the earth’s crust, while sodium constitutes about 2.6 percent (the sixth most abundant element – even though it never appears naturally as an element), and can be produced from simple drying of seawater (Lewis and Clark left a drying cairn in Seaside, Oregon where they produced salt for their animals and themselves). Because of this relative availability, a carbonate form of lithium costs about $7,000 per ton, while an equivalent weight of sodium carbonate costs less than $200.  But, sodium has an ionic radius about 1/3 bigger than that of lithium, and because of that size cannot use inexpensive graphite as an anode in Na-ion batteries.  Even with that limitation, material costs end up being lower overall.

Again, the manufacturing end retains all the techniques used in lithium batteries.  Best Magazine reports, “’If someone wanted to convert a line to sodium‑ion there is literally nothing that needs to be changed apart from the materials used,’ says Chief Technology Officer Jerry Barker. ‘The technicians running the line wouldn’t notice any difference.

“’We double‑side coat the anode and cathode; layer the materials step‑by‑step with a separator, we electrolyte‑fill for the porosity in the electrodes and separator; there are two or three formation cycles; we degas; then we make the final seal.

“’We could jelly‑roll for 18650 cells or use a Z‑fold arrangement of a continuous layer of separator instead of individual stacks with a square separator, but whichever process we would choose it is exactly the same process as for lithium‑ion.’”  This ability to use existing process lines is similar to the use of existing semiconductor chip manufacturing lines by Sakti 3, and will enable quick startups and technology transfer.  The same techniques used in their NaCl batteries will work with improved lithium iron phosphate (LiFePO4) batteries, for which Faradion has also developed chemistries.  Their manufacturing techniques will lower costs for these cells, according to the company.  Lower prices will come from the lower costs of primary materials, and the ability to use existing facilities with little or no modification.

Test e-bike with large Faradion battery modules (for ease of manufacture on prototype)

Test e-bike with larger-than-necessary Faradion battery modules (for ease of manufacture on prototype)

Getting into a market, though, presents some difficulties.  The firm explains that entry into the automotive market might be slowed by problems of obtaining licenses and clearing regulatory hurdles, so it’s looking at starting in cargo e-bicycle power packs, and domestic solar energy storage for homes and communities.

With a readily available non-volatile material, Na-ion batteries seem to have a future in battery development.  The leaders at Faradion think they can reach energy densities that would make their batteries attractive to EV developers.  We wish them luck.

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EAS IX: JoeBen Pulls off a Hat Trick

JoeBen Bevirt, founder and head of Joby Aviation and Joby Motors , is obviously a workaholic, and not only gave a talk at EAS IX, but had an example of his Lotus unpiloted aerial vehicle at the AUVSI (Association for Unmanned Vehicle Systems International) conference in Atlanta, Georgia on the same weekend.

Joby's Lotus UAV showing split-tip wing that transforms into a large tip rotor

Joby’s Lotus UAV showing split-tip wing that transforms into a large tip rotor

Two weeks before that, his demonstration wing for the LEAPTech program was speeding across the desert at NASA’s Armstrong Flight Research Center (AFRC), Edwards Air Force Base in California. JoeBen told Symposium attendees all about his S2 personal aerial commuter and LEAPTech, a joint development with NASA.

Part of the LEAPTech program has included building a truck platform for testing the 18-motor wing.  This is a fascinating bit of engineering in itself.

YouTube does not yet show a test run with the truck and wing, but this news item includes it here.

LEAPTech (Leading Edge Asynchronous Propeller Technology) is a NASA Team Seedling Award under the Convergent Aeronautics Project of ARMD (Aeronautics Research Mission Directorate). The team is made up of LaRC, or Langley Research Center (lead design), AFRC (lead integration), ESAero (Data Acquisition and Instrumentation) and Joby Aviation (Truck Design/Fabrication, wing design/fabrication, motor design and system power).

The S2 is a two-seat vertical takeoff and landing (VTOL) aircraft that seems like an expansion of Joby’s earlier Monarch, a single-seat machine. Its 12 rotor/propellers would carry the occupants on an up-to-200-mile, autonomous flight to destinations of their choosing.

Joby Aviaton's S2 in high-speed cruise

Joby Aviaton’s S2 in high-speed cruise

JoeBen describes heliports as expensive, noisy, and perceived as dangerous by the general public. For those reasons, they are often rejected by city and neighborhood planners. But he claims his VTOL electric aircraft could be 100 times quieter than a helicopter, and benefit from its rotor blade tip speeds in hover of 350 feet per second, well under the supersonic threshold.

Making a direct comparison, JoeBen says the S2 has a higher disk loading and higher mass than a Robertson R22,but also a higher cruise speed and a lower, much less noisy, rotor tip speed. With its 12 motors, it would be safer than a helicopter, with extreme redundancy and fail-safe systems.

Such a machine would appeal to air taxi operator, and maybe even offer transportation alternatives like Uber a vehicle that could expand its operations to 70 to 250 mile hops. With an operating cost of 2.00 per mile, operators could be profitable at today’s taxi rates. Comparing rates, a taxi ride from San Francisco International Airport (SFO) to Fremont, California is around $55.00 for the 32.8 mile ride by the most direct route, and will take at least 38 minutes. Bay Area Rapid Transit charges $11.25 for the same trip, but takes over an hour and 40 minutes. A direct, air-miles route is 28 miles, costing $56.00 in operating costs, and taking less than 15 minutes. People will be willing to pay a modest premium for the convenience and speed of the trip.

These advantages would grow on longer routes, where the airplane’s high speed would enhance point-to-point times. With Dr. Seeley’s on-airport pocket airparks, the convenience level would be as great as that of finding a ground taxi, or probably greater than fighting one’s way to a mass-transit stop. With all these projects progressing rapidly, JoeBen and his team including Alex Stoll and Edward Stilson, among others, are helping define aviation’s future. It should be a green, quiet future.

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Getting Sideways in SI2

Any pilot who’s had to land an airplane at its crosswind limit knows that each airplane has a point where its controls cannot overcome the sideways force, and one cannot perform the final level, straight-down-the-runway touchdown.  Usually, pilots do a go-around or find a more wind-oriented runway.  Solar Impulse’s explanation under the video tells why this is almost impossible under deteriorating conditions with a craft as huge and slow as SI2.

Take note of the control inputs test pilot Marcus Scherdel makes in the final moments of the August 30, 2014 flight.

The Solar Impulse team released this video in the last week, perhaps to explain why the crew is waiting for a positive “weather window” before embarking on a planned five-day epic voyage from Nanjing, China to Hawaii.

“Solar Impulse was still in flight test phase when Markus Scherdel, the experienced test pilot, was put to a challenge by strong crosswinds during landing. Si2 returned from a flight to Payerne Airfield and performed a planned low approach before landing. A go around and subsequent approach takes on average 20 minutes, during which the winds increased significantly and unexpectedly to 4 knots (4.6 mph) crosswind component. The pilot had no other option but to land despite the situation as the weather was rapidly deteriorating. Right before landing, the pilot got gust from the side, blowing the plane off the runway to the right. He then needed to correct back to the center line. Markus never lost his smile, although he was imposed a great work load, trying to avoid landing next to the runway or losing balance. This demonstrates how Solar Impulse is sensitive to turbulences.”

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EAS IX: Phil Barnes Double Header

Phil Barnes, aviation consultant, opened each days’ sessions at this year’s Electric Aircraft Symposium: on Friday with a talk on dynamic soaring as taught by the birds, and on Saturday on regenerative power to keep a dynamic soaring aircraft in perpetual flight without any outside energy source other than the sun.

Phil has 31-years of experience in the performance analysis and computer modeling of aerospace vehicles and subsystems at Northrop Grumman. He has been to Antarctica twice to photograph and study the flight dynamics of the Albatross, lessons he applies to the ideals of dynamic soaring and energy retrieval in flight.

His Friday morning talk, “How Flies the Albatross,” discussed the flight mechanics of dynamic soaring, that mode of maintaining or gaining altitude from horizontal wind gusts, something the albatross uses to fly huge distances searching for food for itself and its family.  From the observations of well-known naturalists, he showed the bird “could soar against strong winds without a beat of its wings (Jacques Cousteau), something elaborated on by David Attenborough and first attested to by Isaac Newton (1725) and Lord Rayleigh (1883).

Barnes reports on his web site, “The albatross travels overall downwind faster than the wind. Indeed, the albatross circumnavigates Antarctica several times per year, in as little as 46-days per trip. Only with dynamic soaring can the albatross fly so fast and far.”  Going into the wind, the Albatross ascends into an increasing headwind, the essence of dynamic soaring.  With the boundary layer over the ocean an estimated 250 feet thick, these birds have more than enough “ceiling” in which to explore dynamic exploitation of the vertical gradients of a horizontal wind.

Others are thinking along the lines Phil Barnes discussed in his EAS talk.

Others are thinking along the lines Phil Barnes discussed in his EAS talk.  Oceanographer Phil Richardson created this “conceptual illustration of a robotic unmanned aerial vehicle soaring over the ocean, taking advantage if the same physics that an albatross does to fly fast and efficiently.” Photo: Phil Richardson, Woods Hole Oceanographic Institution

Barnes illuminates the physics of dynamic soaring with a simple explanation – riding with a model airplane in a car with a sunroof.  “Let’s say we are driving our car at 90 km/hr with the moonroof open. Just beneath the moonroof we hold a model airplane. Although the model at this point is traveling at 90 km/hr it has no airspeed, and thus no usable kinetic energy, relative to the air in the car. Were we to let go of the model it would fall to the floor of the car. If, however, we were to raise the model just above the moonroof, it would suddenly gain 90 km/hr. of airspeed and the corresponding amount of kinetic energy. Once released, the model would convert its newfound kinetic energy into potential energy by climbing high in the sky.”

He uses dynamic soaring force diagrams, showing direct quantitative proof of Lord Rayleigh’s qualitative descriptions of the phenomenom, and explains the three orthoganal accelerations showing that Newton’s laws are applied in the bird’s soaring flight.  Including factors such as turn rate and modulated thrusts adds up to a complicated nine factors that help determine the success of the bird’s efficient exploitation of horizontal wind currents.

An albatross deals with this complex math and does something that would have driven our flight instructors wild – it holds its head level with the horizon, keeping its “sensor platform” constant with the plane of the horizon.  Phil notes that his simulation program (which readers can try out on Phil’s web site) keeps the head of his idealized bird level, something of which he is quite proud.

Phil concludes that wind gradients, not waves; and airspeed, not groundspeed, make dynamic soaring possible.  This type of soaring makes net progress in any direction – something the Albatross has mastered in its 50 million-year journey to perfection.

In the second-day opener, Phil was back to show the strong relationship between his studies of Albatross flight and the potential of regenerative flight, something that would enable nearly perpetual flight using electronics technology similar to that used on cars such as the Toyota Prius.

Phil Barnes Regenosaur, taking inspiration from the Albatross and the Toyota Prius

Phil Barnes Regenosaur, taking inspiration from the Albatross and the Toyota Prius

His Regenosaur comes from observation of Albatross flight, simulation of dynamic soaring and the thoughts of aerodynamicists such as Hermann Glauert and Paul MacCready, including Glauert’s early thoughts on wind turbines and ridge lift, and MacCready’s speculations on the possibilities of regenerative flight.

Barnse’s windprop combines the functions of a propeller and a wind turbine, and must be carefully designed to work in pinwheeling mode and derive the most thrust from a propeller based on the “Betz conditions,” named after A. Betz, who theorized minimum energy losses from lightly-loaded propellers as early as 1919.  The windprop would have eight blades carefully set for blade twist to satisfy Betz conditions, and drive a brushless motor/generator that could provide thrust, and then feed energy back to the aircraft’s batteries through a “six-pack” inverter-rectifier designed for efficient regeneration, actually amplifying the effects of the windprop.  These ideas are more fully explained in Phil’s presentation on his web site.

As always, Phil Barnes gave a thorough and challenging analysis of how to learn from nature and apply those lessons to a promising approach to perpetual flight.

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Goshawk Goes Electric

The GosHawk was conceived as an electric aircraft and technology has FINALLY caught up with it, according to designer Greg Cole. Its sailplane-like proportions allow it to fly with the smallest of power inputs, and real soaring is possible with the electric propulsion system completely shut down, Greg says.  This author finds it suits its namesake with a sporty nature and a natural beauty.

Flowing lines of Goshawk show strong design heritage from Windward Performance

Flowing lines of GosHawk show strong design heritage from Windward Performance, even in unfinished form.  Photo courtesy of Greg Cole

The GosHawk is also planned in two additional versions with internal combustion engines. The HKS 700E engine is a fuel-efficient two-cylinder unit seemingly ideal for motorgliders or touring gliders. His airplane with this engine’s 56 horsepower available can attain a 100 mile per hour cruise at a fuel consumption of 100 miles per gallon, or 200 passenger miles per gallon (pmpg). Greg also plans on using the ubiquitous Rotax in 85 BHP form.

Its empty weight of 510 pounds with the HKS powerplant shows the skills Greg’s company, Windward Performance achieves with pre-impregnated carbon fiber layups. Greg has crafted a 50.8 foot wingspan aircraft that weighs about 220 pounds less than a 65-hp Piper J-3 and still retains sailplane load limits (+5.3g / -3.0g). Part of this is due to the use of a modified version of the DuckHawk wing, designed for dynamic soaring in this single-seat high-performance sailplane. In two-seat service with a motor and batteries, it’s still stronger than a utility-class General Aviation craft.

GosHawk’s high never-exceed velocities (depending on model) demonstrate its excellent strength and verify its high-speed capabilities.  Its 38:1 lift-to-drag ratio at 46 knots (52.9 mph) and 130 feet per minute minimum sink rate at 46 knots (52.9 mph) highlight its aerodynamic cleanness.

Greg says, “We plan to retain the V, SV, and VNX designation started with the DuckHawk. V would be the very lightest (perhaps the most interesting) and with lower speed limits (120 KEAS* Vne, or l38 mph). The SV would have a 200 KEAS Vne and higher gross weight limits. The VNX would push the Vne up to 225 KEAS.”

Projected rate of climb at 700 pounds is 1,200 feet per minute at 85 knots (97.75 mph), a nice cruising climb while still clearing obstacles. On the other end, Goshawk’s stall speed of 42 knots (48.3 mph) enables short-field landings, especially with its low total mass.

Its side-by-side configuration makes it a good training platform, and its soaring capabilities will allow thermal, slope, and wave exploration. The motor can be restarted at altitude for self retrieval if required.

Greg’s electric propulsion system will enable the same performance and an hour’s endurance using currently-available batteries. The airplane is nearing completion at Windward Performance’s workshops in Bend, Oregon, waiting installation of its environmentally-friendly motor system.

Greg plans to offer three battery capacities in increments of 5 kilowatt-hours (kW-Hrs). Endurance with 5kW-Hr is 30 minutes, making GosHawk more of a self launching sailplane. Greg explains, “The full battery capacity, or load if we can say that, will dig into performance and add 180 pounds (90 pounds per 5 kW-Hr) to the weight but give it an almost usable range. Gross weights of the SV and Vnx versions will be 1,150 pounds. It is likely that the weight of the 5kW-Hr capacity version will equal that of the HKS-powered aircraft.”

Weights and performance numbers are based on currently available batteries, which are projected to improve with time. We look forward to seeing the new motor installation and Goshawk’s first flights.

*KEAS: knots equivalent air speed – calibrated airspeed corrected for atmospheric properties at the particular altitude.

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EAS IX: Mike Ricci Explains PWB, Safety

Dreamliner battery nightmares have troubled the dreams of electric flight for the past two years.  Michael Ricci, Vice President of Engineering with LaunchPoint Technologies, gave attendees at this year’s Electric Aircraft Symposium a crash course (pun intended) in the many types of failure modes electric aircraft face.  Luckily, he also provided ways to mitigate and eliminate those failure modes.

Michael Ricci of LaunchPoint Technologies explains Propulsion by Wire (PBW) to EAS IX attendees

Michael Ricci of LaunchPoint Technologies explains Propulsion by Wire (PBW) to EAS IX attendees

He introduced a concept called “Propulsion by Wire” (PBW), the main thrust for electric aircraft and roughly akin to the commonly discussed “Fly by Wire” concept.  Asking what product specifications for electric propulsion will look like, he answered his own rhetorical question with the technical requirements for reasonable interaction, a useful user interface, airworthiness, and safety.

Starting with the last issue first, safety (which should always come first), we need to be able to continue safe flight after a single component failure.  There are some surprising, counter-intuitive things at work here.  Depending on whether we start with a qualitative hazard analysis or a quantitative fault tree analysis, we want to design systems that don’t become catastrophic when one component fails.  Aircraft have structural redundancies to prevent total overall failure when one item is damaged.  That kind of design thinking allowed bomber crews to make it home in aircraft missing large pieces, and even enabled Captain Sullenberger and First Officer Skiles to make a water landing in the Hudson River after their Airbus collided with a large flock of Canada Geese.

A Failure Mode, Effects, and Criticality Analysis (FMECA) looks at single points of failure, and in aircraft, according to Mike, strive for a low failure rate of 10-7, or one failure per hundred million flight hours.  That would seem close to perfection, but isn’t realizable in the real world.  The perfect part, even with demonstrated reliability, works with other components.  An engine is a good example.  Combining groups of components with 10-5 (one failure in 100,000 hour) reliability might give an aggregate for the complete engine of 10-4, an order of magnitude less reliable than each of the individual components.  Lycoming engine components, according to Mike, run between 10-4 (one failure in 10,000 hours) and 10-5  (one in 100,000 hours).  These are not always total engine stoppers, but may reduce performance or lead to the necessity to find an alternative airport.

Following FMECA, designers often use FTA, failure or fault tree analysis, seeing what the failure of one component might take with it.  The combined analyses help account for the reliability we enjoy with modern mechanical engines, and we like to think electric motors are simpler and more reliable than their mechanical counterparts, but how do we help promote high reliability?

Mike suggested the use of built in tests and power-on self-tests as part of a modern approach to making electric aircraft safe.  Such systems would check and detect latent failures, and if failures did occur, make second failures improbable.

He premised a bus or channel that had a mean time between failure (MTBF) of 3,000 hours, and populated that channel with various electrical components.  Such systems would have line replaceable units (LRUs) that would be swapped out easily, even before failure, but as predicted by their MTBF lifetimes.  With “redundant everything,” even low reliability components can achieve high system reliability:  N+1 or N+2 electric tail rotors, for instance.

This may include using roughly equivalent components from different manufacturers, or different models from the same manufacturer.  Such approaches can use a democratic version of artificial intelligence, with different controllers “voting” on a next state or modulating function.  Because, in current design trends, every component has associated software, a single-event upset in the software or embedded firmware could have far-reaching consequences.

Mike suggested reviewing material in Michael Barr’s web site, with his presentation on Killer Apps, software glitches that have caused at least 30 deaths in the three examples given.  Flying by software means that the software has to be redundant and rely on an architecture that prevents any one failure from bringing an airplane down.  This type of fault-tolerant computing is necessary to prevent the kinds of accidents brought on by faulty software – such as one hybrid car’s unintended acceleration issues a few years ago.

There will always be pilot errors and mechanical failures, but electrical and software control systems will be called to attain an even higher standard.  Such systems need to be able to isolate faults to prevent damage to other parts of the system, to identify bugs before they become active, and to maintain the stability of the bus or channel that connects everything.

He had some practical ideas for the design of such systems, such as avoiding long leads, where inductance can cause problems.  He noted that over-voltage destroys components and can lead to battery pack failures.  Such steps help, but high reliability takes time to validate, unfortunately.  That’s where his most counter-intuitive thought summarized much of the talk – using redundant, lower-reliability components in combination can offer reliability while allowing speedier testing.

Throughout the discussion, he showed slides with schematics of a craft that looked very much like the GL-10 currently being tested by NASA, and which looks itself like a small version of what will become LEAPTech, on which LaunchPoint is working with NASA to provide a high-reliability battery management system.  Mike’s email says, “We are working fairly closely with the NASA folks doing the GL-10 VTOL testbed and with Mark Moore who is doing the LEAPTech project.  It is highly likely that the GL-10 testbed will be able to fly later this year using a hybrid propulsion system / gen-set provided by us.”

Michael Ricci explains LaunchPoint's involvement with NASA's LEAPTech program

Michael Ricci explains LaunchPoint’s involvement with NASA’s LEAPTech program

The many projects and diverse approaches that LaunchPoint brings to its clients shows an inventive and responsive company in action.  We were honored to have Michael Ricci on hand to share these innovations with us.

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Good News and a Bright Future from EAS IX

Sitting next to your editor for the first day of CAFE’s ninth annual Electric Aircraft Symposium, Paul Bertorelli from AVweb, took copious notes, made sound recordings, and during coffee and lunch breaks and in after-hours sessions, interviewed the accomplished faculty at the Symposium.  His thorough and far-reaching reports appear in his last several days’ postings to AVweb.  Having stressed mightily while attempting to take understandable notes from each speaker’s talk, your editor can only be impressed by Paul’s super reportorial abilities, and his communicating the scope and importance of what took place at EAS IX.

Professional film crew at EAS IX.  Watch for the video!

Professional film crew at EAS IX. Watch for the video!

From your editor’s perspective, several significant things took place this year.  Senior leadership from Airbus and Siemens presented talks affirming their companies’ commitment to making progress in electric aviation, with future plans to develop two and four-seat aircraft for European and American markets from Airbus, and to produce a range of light-weight, commercially-available motors from Siemens.

Siemens has 343,000 employees worldwide and revenues of 101.2 billion euros, or $111 billion U. S. dollars.  Airbus, During the 2014 Farnborough Air Show, won US$75.3 billion worth of business for a total of 496 aircraft, making it by far the largest Farnborough show for Airbus – both in terms of dollar value and also in the number aircraft.  Airbus has around 63,000 employees.

That these mega-corporations are willing to present in Santa Rosa, California to a Symposium organized by a non-profit organization makes CAFE intensely aware of the growing world-wide interest in electric aviation, and proud to be a part of that burgeoning momentum.

Pipistrel's Taurus G4, winner of GFC I.  We hope for many more Challenges and even greater progress.

Pipistrel’s Taurus G4, winner of GFC I. We hope for many more Challenges and even greater progress.

CAFE might be seen as the “Woodstock of Aviation,” over the last 35 years through its focus on “garage-band” levels of technology that were simple and available to home craftsmen.  These craftsmen took a scientific approach to improving the often mediocre aerodynamics of commercially available light aircraft, or designed and built their own aircraft in the pursuit of ultimate efficiency.  CAFE organized races at Oshkosh, and perfected precise test methods for measuring true aircraft performance.  The resulting performance and economy improvements drew leaders in General Aviation to collaborate with CAFE and culminated in 2011’s Green Flight Challenge.  That event featured the largest prize in aeronautical history, won by Pipistrel with their Taurus G4, closely followed by Stuttgart University’s e-Genius.  That event brought together the quietest airplane on record and the two most efficient. Both of which won prizes for their designers.

GFC gave Dr. Seeley entrée to influential people.  He presented his idea for the Sky Taxi, for instance, to John Holdren, Assistant to the President for Science and Technology, Director of the White House Office of Science and Technology Policy, and Co-Chair of the President’s Council of Advisors on Science and Technology (P-CAST).

Following GFC I, NASA’s Chief Technologist said that event was, “One of NASA’s smallest expenditures yet one of our biggest achievements last year.” Indeed, the $1.47 million NASA gave in prizes netted $7.6 million in investments by competitors, and at least 20 STEM (science, technology, engineering and mathematics) graduate theses. Even better, the competition was run by all-volunteer labor, including the entire CAFE Foundation board.

This “bang-for-the-buck” set of results caused the White House Office of Science and Technology Policy (OSTP) to call the GFC the “poster child of technology prizes,” and to authorize and encourage all federal agencies, “To use technology prizes to achieve breakthroughs.”

We may see a new “Age of Aeronautical Enlightenment” grow from these high-level acknowledgements, with those skilled in aerodynamics and electric power creating new and efficient vehicles spanning everything from ultralights to massive cargo haulers.  The fact that many innovations are coming from Europe might provoke some friendly competitive interest from Boeing, Northrop, GE and Lockheed, the first three of whom had representatives at EAS IX.  The world is waking up to electric aviation, with attendees from Norway, Italy, Germany, Spain, Canada, Japan, Brazil, Slovenia, India and France taking in the wealth of information presented this year.

The CAFE Foundation and its devoted board members put on a good show this year, and look forward to going even bigger and better with future Symposiums and Challenges.  Good things are on their way.

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If there were a pantheon of technological hipness, right now three front-runners for induction would be 3D printing, aerogel and graphene.  They all rank high on the disruptive technology scale, have enormous amounts of good press, and excite the imagination with their potential.

Lawrence Livermore National Laboratory researchers have gone beyond combining chocolate and peanut butter by blending the three higher-tech ingredients into a rather amazing battery material with excellent electrical and mechanical properties.  We have discussed the idea of structural batteries in this blog, and this new melding of technologies holds much promise.

Aerogel, as defined in the Laboratory’s announcement, “is a synthetic porous, ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. It is often referred to as ‘liquid smoke.’”

Aerogel rightly earns its name of "frozen smoke"

Aerogel rightly earns its name of “liquid smoke”

Lawrence Livermore researchers have used a 3D printing technique known as direct ink writing to craft an engineered architecture microlattice with well-defined pores – which are essential to the performance of the lattice.

Microlattice formed by a graphite oxide ink forced through a micronozzle to form 3D printed lattice structure

Microlattice formed by a graphene oxide ink forced through a micronozzle to form 3D printed lattice structure.  Illustration: Ryan Chen/LLNL

 Combining a 3D printed microlattice with aerogel makes a lightweight structure with high surface area, excellent electrical conductivity, mechanical stiffness and supercompressibility (the ability to withstand up to 90-percent compressive strain).

The announcement explains, “Previous attempts at creating bulk graphene aerogels produce a largely random pore structure, excluding the ability to tailor transport and other mechanical properties of the material for specific applications such as separations, flow batteries and pressure sensors.”  The pores turn out to be important, since the random structure inhibits mass transport.

Tailoring the pores to desired sizes improves electrical performance.  “In addition, the 3D printed graphene aerogel microlattices show an order of magnitude improvement over bulk graphene materials and much better mass transport.”

Marcus Worsley, a co-author of the Nature Communication paper on the research, explains, “Making graphene aerogels with tailored macro-architectures for specific applications with a controllable and scalable assembly method remains a significant challenge that we were able to tackle.  3D printing allows one to intelligently design the pore structure of the aerogel, permitting control over mass transport (aerogels typically require high pressure gradients to drive mass transport through them due to small, tortuous pore structure) and optimization of physical properties, such as stiffness. This development should open up the design space for using aerogels in novel and creative applications.”

The graphene oxide (GO) inks combine an aqueous GO suspension and silica filler to form a homogenous, highly viscous ink. These inks are then loaded into a syringe barrel and extruded through a micronozzle to pattern 3D structures.

Engineer Cheng Zhu, the other co-author of the journal article.says, that adapting the 3D printing technique to aerogels “makes it possible to fabricate countless complex aerogel architectures for a broad range of applications including its mechanical properties and compressibility, which has never been achieved before.”

The research appears in the April 22 edition of the journal, Nature Communications.  Other researchers contributing to the paper include, T. Yong-Jin Han, Eric B. Duoss, Alexandra M. Golobic, Joshua D. Kuntz, and Christopher M. Spadaccini.

Such research shows the potential to make ever lighter, more powerful batteries as just one possibility.  The fact that this featherlike material can also have beneficial structural properties makes this area of research a very exciting one.

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