The three biggest words in battery structures are “Area, Area, Area.” The more anode and cathode area a battery can expose to the electrolyte that carries ions and electrons between the positive and negative ends of the battery, the better. Most battery configurations, according to researchers at Carnegie Mellon University and Missouri University of Science and Technology, block a great deal of interaction between these elements. Their solution is to go porous in a microlattice battery, thanks to 3D printing.
Lattice architecture can provide channels for effective transportation of electrolyte inside the volume of material, while for the cube electrode, most of the material will not be exposed to the electrolyte. Source: Additive Manufacturing 23 (2018) 70-78
Electrodes present some surface area to the electrolyte, which can only interact with the surface area presented. Rahul Panat at Carnegie Mellon and Jonghyun Park at Missouri S & T have created a cube-shaped battery composed of microlattice electrodes which present significantly greater amounts of surface area to the electrolyte.
The title of their paper (with co-author Mohammad Sadeq Saleh) brings out this “area rule”: “3D printed hierarchically-porous microlattice electrode materials for exceptionally high specific capacity and areal capacity lithium ion batteries.” The abstract explains, “This work reports a major advance in 3D batteries, where highly complex and controlled 3D electrode architectures with a lattice structure and a hierarchical porosity are realized by 3D printing. Microlattice electrodes with porous solid truss members (silver – Ag) are fabricated by Aerosol Jet 3D printing (AJP) that leads to an unprecedented improvement in the battery performance such as 400% increase in specific capacity, 100% increase in areal capacity, and a high electrode volume utilization when compared to a thin solid Ag block electrode.”
Lattice battery features microscopic “hierarchical porosity” and high performance
The microlattice structure proved to be mechanically robust, not losing its minuscule shape after 40 charge-discharge cycles, and managed to retain its electrical capacities. The authors note that the technology can be applied to a wide range of electrochemical energy storage systems.
Panat, an Associate Professor in Mechanical Engineering at Carnegie Mellon, reflects, “I don’t believe anybody until now has used 3D printing to create these kinds of complex structures. Since this work was done at the laboratory scale, it’s a bit surprising to see that the researchers think it can be “Ready to translate to industrial applications in about two to three years.” As a droplet-based deposition technology, AJP is one of the only means of creating such precise and complex geometries. Panat asserts, “If this was a single stream of material, [as in FDM (Fused Deposition Modeling)/FFF (Fused Filament Fabrication) technology] as in the case of extrusion printing, we wouldn’t be able to make them.”
Fabrication process melds dots of silver in intricate maze to form structural, electrical cube. Like other 3D processes, fine thread of silver becomes heated, deposited in precise arrays
As noted by the researchers, batteries can be lighter for the same capacity as current storage devices – or more powerful for the same weight. The microlattice’s strength, electrical performance, and potential design flexibility could lead to uses in medical devices, drones and even full-size aircraft. “For example, a part of a drone can act as a wing, a structural material, while simultaneously acting as a functional material such as a battery.” This would bring one of your editor’s dreams closer to reality – the Grand Unified Airplane, in which the structure stores energy while collecting it from the act of flight itself. Sunlight, even the wind itself, could power the aircraft. With materials like the microlattice battery, this dream could be realized in at least some components of future aircraft.
UAVOS, located in the midst of surrounding Google properties in Mountain View, California, sells a wide variety of goods and services related to the unpiloted aircraft world. One of their biggest creations so far, the ApusDuo High Altitude Psuedo Satellite (HAPS) ran through a full series of tests. The 10-meter span prototype vehicle will test control algorithms, including takeoffs and landings and verify HAPS aerodynamics. According to UAVOS “Test flights fully confirmed the flight characteristics of the UAV.” This is good news, since their next step will be to make at least a 15-meter wing (49.2 feet) wingspan version. That will rely even more on “Control of roll, pitch, v-shape and slip…due to a controlled change in the angle of attack in particular sections of the wings” employed by the designers. Note the flexibility of the entire airframe during launch and flight.
These controls include the visibly tricky interactions of the two slender wings, a rare pair in tandem designed to allow their reactions to the air around them to maintain stability and structural reliability. Weighing a maximum of 23 kilograms (50.6 pounds), the ApusDuo stays within the FAA’s 55-pound limit for drones, but will occupy airspace between almost 40,000 and 65,000 feet. Plans seem to include a 28-meter (91.8 feet) version.
The company makes a full array of automated control systems and control stations for aerial vehicles from under 15 kilograms (33 pounds) to over 1,500 kilograms (3,300 pounds). They produce UAVs from 15 kilogram fixed wing craft to their Pipistrel conversion, and a range of rotary-wing vehicles up to 107 kilograms (235.4 pounds) takeoff weight.
UAVOS recently flew another of their creations, a Pipistrel Sinus (pronounced see-nus) under full autonomous control of their on-board systems. A Light Sport Aircraft such as the Sinus can carry a payload of 200 kilograms (441 pounds) for up to five hours, making it a useful tool for many applications. With a payload of only 40 kilograms (88 pounds), the Pipistrel can carry more fuel and stay airborne for up to 20 hours. The flight included a fully autonomous takeoff, navigation to a selected destination and back and a fully-autonomous landing.
As UAVOS continues its flight tests on a growing number of vehicles, the company’s leading statement, “Beyond human capacity, under machine control,” will probably become even more apparent. Civilian and military uses for their aircraft and systems are well defined on their website.
Aircraft quite often seem to get designed as an assembly of separate components, wings an entity unto themselves, engines or motors something attached to the fuselage or wings, and not always seen as a set of matched components until final assembly. Quite often, different components are compromised from their optimal shape or structure because of the need to integrate them with other parts of the craft. One group of researchers is finding ways to even cause components to begin communicating among themselves.
Some parts, such as engines or motors, are hung on the wing or fuselage as replacements for earlier design variants. The new powerplants may provide additional power, but they may also interfere with the overall performance and handling of the airplane.
Dr. Phillip Ansell of the University of Illinois
University of Illinois researchers led by Dr. Phillip Ansell, assistant professor in the Department of Aerospace Engineering in the College of Engineering has explored this subset of aeronautics and come to the conclusion that wings and propulsion need to be an integrated whole. “If we allow those two systems to talk to each other, there is a lot of increased complexity in the flow field over the wing and into the propulsor – which also substantially alters the performance. We’ve taken two subsystems – propulsion and aerodynamics – and we’ve said that these are not isolated subsystems. These are now one thing.”
Very much like experiments performed by Dr. David Ullman in his home wind tunnel in Independence, Oregon, Dr. Ansell’s work involved, “Using a 3D printed model of an airfoil, which is a cross-section of a wing, mounted inside a subsonic wind tunnel. We had a model with ducted fans mounted over the trailing edge of the airfoil. The flow goes across the upper surface and then into the fan.”
Ansell’s team’s research might lead to aircraft such as the French ONERA Ampere
With graduate student Aaron Perry of the U of I and Michael Kerho from the Rolling Hills Research Corporation, Ansell attempted to understand the coupling between ducted fan systems and wing sections and how their interactions can modify overall aerodynamics of the total flight system.
Ansell explains, “If we integrate the propulsors, which in this case are fans, into the wing, we can improve the aircraft’s propulsive efficiency by ingesting the low-speed air across wing surface into the propulsor. But it’s challenging to figure out how to do it in a smart way.”
Another possibility would be use of integrated ducted fans as in the Lilium VTOL machine
Seeing that a ducted fan on top of the wing changed the aerodynamic behavior of the airfoil when fan’s throttle setting was changed, he explained, “We can adjust the throttle to make the fan spin faster or slower, so that I now have a high-speed jet that’s coming out the back end and acts to substantially lift the aircraft through a phenomenon known as supercirculation. It also changes the flow across the surface. I have little regions of the flow on the surface called boundary layers. Whenever I ramp up the throttle and start pulling air into that propulsor, it thins out the boundary layer. It modifies the distribution of the pressure across the airfoil itself. There are some complex things happening. That fan RPM talking to the aerodynamics of the larger airfoil is substantial.”
We can’t just think of increasing the throttle and adding thrust as an isolated function any more, he added. “It’s not that simple because it also changes the air flow over the wing. The different orientations of the end of the fan changes the performance of the wing section as well as the pressure distribution because it changes the local flow quality characteristics. We have now quantified that and can understand some aspects of what that looks like.
“We were able to take measurements to better understand what those variations in coupling characteristics are. Previously we knew that if we ramp up the throttle on this fan, the result is a thrust vector pointed in a certain direction. Now we know that it will also modify my local wing aerodynamics.”
He explains his design: “Propulsion is built into the airfoil so that the intake sucks in the flow across the upper surface (of the wing), and exhausts the air out the trailing edge. This provides us new ways to tailor the way the pressure is distributed across the airfoil surface and also employ our propulsion system directly at the location of the wing wake. Both of these effects offer distinct benefits within an aircraft design.”
Hybrid-electric with multiple redundancy: three independent drive units in one engine block. Should a module fail, flight can continue with two remaining components. Scalewings engine exists as concept, development work expected to take three years.
This caused your editor to go quickly to the ScaleWings home page, where a beautiful P-51 Mustang in 70-percent scale dazzles. The airplane is available in Ultralight, Light Sport Aircraft, and Experimental configurations using engines from the UL and Rotax lines up to a Chevrolet LS300, with a supercharged variant offering up to 600 horsepower. Their brochure, in German or English gives a great overview of the features of this carbon-fiber replica.
Scalewings has an even more exciting powerplant on the way, especially for those of us who value our own hides. Their triple-redundant engine/motor combines a naturally-aspirated four-stroke engine, a turbocharged four-stroke engine, and an electric motor. If any one unit fails, the plane can fly the other two.
One V-twin engine is naturally-aspirated, one is turbocharged, and they both share their shaft with an electric motor
Flyer Magazine quotes Hans Schwöller, described as a “mastermind” on the company’s website and managing director of the ScaleWings group, explaining his “secret recipe”:
“’The ground-breaking concept of the multiple-redundant aircraft engine consists, in its standard configuration, of three interlocking engines of which two work on the basis of efficient two-cylinder 4-stroke injection engines.
“’The third drive in the form of a high-performance, state of the art electric motor, delivers enormous additional performance, as required, or can also be used for noise protection for accelerating, take-off and climbing to cruising altitude.’”
The integration of all these units in the same casing and using the same crankshaft is a bit of magic, and the sharing of support mechanisms is even more intriguing.
Compact dimensions of what is essentially two V-twin engines, one electric motor
Schwöller continues, ““It is irrelevant if the oil or water cooling system fails or important engine components such as engine control, injection, ignition, crankshaft, connecting rods or valves fail. The drive even continues to work if engine components become fully blocked. Flight can even continue with just one single functioning module.’”
Other firms’ projects to create redundant internal combustion/electric hybrid motors have not been this elaborate. Flight Design and Rotax collaborated on a system originally intended to power that company’s CT Light Sport Aircraft, but which ended up powering Embry Riddle’s EcoEagle in the 2011 Green Flight Challenge. Another product, Axter’s electric motor mounted on the nose of a Rotax engine, was originally designed to allow 20 minutes of flight on battery power if the engine failed. They now have a newer version but don’t show specifications for that option.
Scalewing’s engine comprises these modules, which can be assembled in a variety of way, apparently:
2 x 2 cylinder naturally aspirated engine with 180hp (132kW)
Electric engine unit with 77.7 hp (58kW) plus 2 x 2-cylinder naturally aspirated engine = 260hp (190kW)
2 x 2-cylinder turbo engine + electric engine unit = 350hp (257kW).
Since the Mustang can manage something as powerful as a 600-horsepower LS300 engine, it will manage the hybrid with ease. The engine itself gives hopes that it will be available to other designers who see merit in the reliability it should provide. Your editor thinks it may derive great interest from the eVTOL market, especially.
Vertical Daily News this morning reports on the DHL Parcelcopter 4.0 as it delivers medicines to an island in Lake Victoria on the northern tip of Tanzania. The Parcelcopter is a fourth generation design from Wingcopter, a German drone manufacturer. It’s found delivering packages autonomously in German mountain demonstrations and now in differently rugged terrain, flying life-saving packages to a remote island.
Parcelcopter on delivery mission somewhere over Tanzania
Compare such speedy deliveries to the time, personnel, and energy required on the six-hour overland route of 150 miles (240 kilometers). ). As Vertical Daily News notes, “That makes it nearly impossible to provide emergency medication or to quickly refill cool chain commodities that are out of stock.” Medicines and blood or tissue samples require refrigeration, and time in transit can often ruin precious commodities. To prevent spoilage, the DHL machine has an insulated cargo compartment.
Wingcopter’s founders and designers, Darmstadt University students Jonathan Hesselbarth and Tom Plümmer, developed their project with support from the Technical University of Darmstadt’s Highest innovation and start-up center. Combining helicopter and conventional aircraft features, their design shows flexibility and multiple possibilities for different applications. The video gives an on-board view of how an earlier iteration fo the machine functions.
Operators see new opportunities for addressing logistic challenges in the public health sector in many parts of Africa, especially supplying hospitals and pharmacies, according to Vertical Daily News. “Medical care for the roughly 400,000 residents of the Ukerewe island district of Lake Victoria, for instance, is severely limited. This is partly due to the poor infrastructure and difficult terrain.”
Luckily, Parcelcopters require very little infrastructure to carry out their missions since they take off and land vertically. “After delivering its cargo, it can easily be loaded with blood and laboratory samples to take back to the mainland.” This versatility and speed could help quell epidemics or pandemics, “allowing an early response to slow the spread of viral diseases like Ebola.”
A More Sophisticated Infrastructure
Other groups such as Matternet, Zipline, and Flying Donkeys have worked in Africa to deliver medical supplies. DHL has joined them and has a history in Bavaria, testing a more sophisticated form of delivery using drones. The video shows the evolution of the DHL Parcelcopter, but since it was completed in 2016, misses the fourth iteration of the drone.
DHL customers in Reit im Winkl and Winklmoosalm plateau were able to sample aerial deliveries at specially-developed Packstations, “dubbed the Parcelcopter Skyport.” 130 autonomous loading and offloading cycles were ultimately performed.
Whether delivering parcels in the Alps or critical medical supplies in the veldt, DHL’s Parcelcopters show that their approach to “last-mile” delivery is an increasingly useful one.
We’ve looked at an array of different biofuel sources ranging from used cooking oil and algae to farm and municipal waste. This is essential as the percentage of airline emissions becomes a bigger part of our overall greenhouse gas situation. The Guardian reports, “A 2017 estimate said air travel accounted for 2.5% of all carbon dioxide emissions, with the total emissions expected to quadruple by 2050.”We’ll look here at how some of the early efforts have panned out and examine a late-breaking surprise or two.
According to the Guardian, “A Qantas plane powered partly by mustard seeds has become the world’s first biofuel flight between Australia and the United States, after landing in Melbourne on [January 30, 2018].”
A Qantas 787-9 Dreamliner made the journey from Los Angeles to Melbourne using a a blended fuel 10% derived from the brassica carinata, an industrial type of mustard seed that functions as a fallow crop. Photograph: Brent Winstone/PR IMAGE
A major test, the 15-hour flight used a blended fuel 10-percent of which came from the brassica carinata, a mustard seed used as a fallow crop between regular crop cycles.
Qantas’ Boeing Dreamliner 787-9 “Reduced carbon emissions by 7 percent compared with the airline’s usual flight over the same LA to Melbourne route. Compared pound for pound with jet fuel, carinata biofuel reduces emissions by 80% over the fuel’s life cycle,” according to the Guardian. Qantas has flown with biofuels since its first trials in 2012, using a 50-percent blend of used cooking oil.
Daniel Tan, an agriculture expert from the University of Sydney, said mustard seed could double as a valuable crop and a source of sustainable fuel for farmers.
“Almost within a day after harvesting, they can press the oil out in their own shed and use it straight into their tractors,” he said. “Basically it’s good for growing, and also farmers can also use it. If they grow wheat every year it’s not good for the soil. They can grow mustard seed in between the wheat crops, every second or third year, press the oil and use it locally or export it for use in aviation fuel. One hectare (about 2.5 acres) of the crop can be used to produce 400 liters of aviation fuel or 1,400 liters of renewable diesel.
“A lot of the biodiesel now being processed is actually from waste oil from places like fish and chip shops. A lot of these oils can be processed, but the problem is that they can’t get consistent supply. The big problem with the biodiesel industry in Australia is mainly the continuity of supply.” Qantas hopes to use biofuels, supplied by U. S. company SG Preston, on all Los Angeles-based flights by 2020.
Other Airlines, Other Approaches
Other airlines, perhaps with less faith in the power of mustard seeds to move large jets, are using a wide array of plant and waste materials to produce jet fuel.
An Alaska Airlines Cooperative
Alaska Airlines, Boeing and SeaTac Airport have been cooperating on using farm and municipal waste to produce renewable jet fuel, but Boeing’s efforts have stretched as far as the United Arab Emirates, where a plan to develop halophyte plants (which can thrive in salt water) continues with the Khalifa University. Boeing also works with partners in biofuel development on six continents, a sign of deep involvement and earnest commitment.
A letter from Paul McElroy, with Boeing Commercial Airplanes Environment Communications, explains the company, “led the approval of the first pathway and that fuel has been flown successfully on thousands of commercial flights. Boeing continues to work tirelessly within ASTM, the international standards body… develop and commercialize new sources of aviation biofuel.”
His letter notes, “Boeing is now partnering with the U.S. Federal Aviation Administration and other stakeholders to gain approval for a biofuel called HF-HEFA (high freeze-point-hydrotreated esters and fatty acids), which is produced from fats, oils and greases. Known as ‘green diesel’ when used in ground transport, global production capacity exceeds 1 billion gallons annually. To verify this fuel’s performance and characteristics, Boeing tested two blends of HFHEFA on its ecoDemonstrator program’s 787 and 757 flight test airplanes. Approval of this fuel would make a price-competitive sustainable biofuel available that could meet more than 1 percent of global aviation fuel supply needs.”
Alaska Airlines, Boeing, and SeaTac have partnered to provide an infrastructure to supply biofuels to all airlines flying from Seattle
Alaska Airlines wants to lead in these ambitions. “As an airline, we require large volumes of fuel to run our business. While technology and operational flying efficiencies have reduced the amount of fuel we use and the associated emissions, they are not enough to lower emissions to achieve industry-wide goals of carbon neutral grown by 2020, and a 50% reduction in emissions by 2050, compared to a 2005 baseline. In 2016, They partnered with Gevo on three commercial flights using alcohol-to-jet fuels, completed two
“Alaska was the first domestic airline to fly multiple scheduled flights using aviation biofuel, and we have committed to use only aviation biofuels that meet stringent sustainability criteria.” Alaska’s 2020 goal of using sustainable aviation biofuel in at least one airport is a work in progress, with several mileposts showing the airline’s progress. In 2016, Alaska partnered with Gevo and completed three biofuel flights using fuel produced by the alcohol-to-jet (ATJ) process. They flew twice on biofuel that used corn as a feedstock, and that November, flew from Seattle to Washington, D. C. on ATJ made from post-harvest forest residues.
The Port of Seattle encourages further development of SAF, with a goal of having all commercial flights powered by sustainable fuels by 2028. The Port sees its roles in providing infrastructure, financing, land use, advocacy and partnerships as crucial to the plan’s success. A note on financing shows assistance from some heavy hitters in the environmental world. The Port reports, “In 2017, Carbon War Room/Rocky Mountain Institute and SkyNRG investigated the feasibility of using different airport revenue streams at Sea-Tac to help bring down the cost to all airlines compared to petroleum jet fuel, as well as support the build-out of fueling infrastructure. The report identified a range of funding sources, and included ways an airport could be involved without directly paying for fuel.”
United’s Far-Flung Suppliers
Other airlines have similar goals and timelines. United Airlines, in a letter expressing its goals, claims to have improved its fuel efficiency by 45 percent since 1990, “but that’s only the first step.” United is working toward “a collective industry goal of 1.5 percent average improvement of annual fuel efficiency through 2020, carbon neutral growth beginning in 2020 and a 50 percent reduction airline CO2 emissions by 2050. United hopes not only to be a good corporate citizen but to guard against oil price instability. Its efforts led the Natural Resources Defense Council (NRDC) to name United a “Leading Airline for having a strong range of commitments and supply chain implementation.”
United became the first airline globally on SAF on an ongoing daily basis. AltAir Fuels in Los Angeles supplies fuels made from agricultural wastes and non-edible natural oils. AltAir fuels lower greenhouse gas (GHG) emissions more than 60 percent compared to petroleum-based products. AltAir’s fuels are certified for sustainability by the Roundtable for Sustainable Biomaterials.
Since 2015, United partnered with Fulcrum BioEnergy, a company pioneering conversion of waste and household trash into low-cost, sustainable aviation fuel. United will have Fulcrum SAF refineries near all its U. S. hubs, producing nearly one-billion gallons in their first ten years of operation, nearly three times the amount United uses yearly. This will keep trash out of landfills, lower United’s emissions, and probably power other operation’s fuel needs.
A Worldwide Organization Promotes SAF
Irina Slav, writing for the industry watchdog Oilprice.com, tells us, “The International Air Transport Association has set an ambitious goal for its members: transporting a billion passengers on flights using biofuel by 2025. The goal is a demonstration of IATA’s efforts to help cut carbon dioxide emissions. The aviation industry is a major source of these, after all.”
She goes on to explain that although biofuels might cut into Big Oil’s profit margins, such alternatives will not grow big enough to be a major threat to the oil business. More expensive than regular jet fuel, some biofuels price themselves out of a very competitive market.
The International Air Transit Association (IATA) backs the drive to promote biofuels. Chief Executive and Managing Director Alexandre de Juniac says, “We want 1 billion passengers to have flown on a SAF (Sustainable Aviation Fuel)-blend flight by 2025. That won’t be easy to achieve. We need governments to set a framework to incentivize production of SAF and ensure it is as attractive to produce as automotive biofuels.” IATA estimates, though, that only half a billion passengers might fly on “biofueled” flights by the target date. You can see the organization’s biofuel report here.
Ms. Slav explains that loan guarantees and capital grants might help if sometimes skeptical banks will cooperate. The industry hopes to trend toward carbon neutral growth and reduce net emissions. Currently, emissions average between 114 grams of CO2 per kilometer on long-haul flights and 260 grams per kilometer for shorter flights. IATA suggests biofuels could cut this by as much a 80 percent. Ms. Slav concludes that the economics will be the tricky part, with producers concentrating on reducing costs and governments providing incentives and probably regulation. Look for higher fares and greater Big Oil activity in biofuels, she cautions.
More to Come
With Zunum and Airbus coming forward with medium-size, medium-range single-aisle airliners, and Pipistrel and the MAHEPA organization coming forward with hybrid small aircraft, biofuels will have a promising place in near-future aviation. We have only shown a few players here, with much more to come on the national and international front in the near future.
Ashish Kumar, CEO of Zunum Aero, announced that his firm will partner with Safran Helicopter Engines to use that firm’s Ardiden 3Z engine as the powerplant for Zunum’s 10-passenger regional airliner. He lists the advantages this installation will provide.
Safran (formerly Turbomeca) Ardiden 3Z turbine engine will power generator on Zunum ZA10 regional airliner
“Our ZA10 aircraft, under development for entry in the early 2020s, will be powered by dual power sources: propulsion batteries, and a Safran turboshaft in the 1,700 to 2,000 shaft horsepower (shp) Ardiden range. This new model, the Ardiden 3Z, will be used as a hybrid power source achieving demanding cost, efficiency and uptime requirements. It will be coupled with an electric generator, and the integrated turbo-generator will deliver 500 [kilowatts] of electric power to supplement propulsion batteries on key stages of flight and over long ranges. Upgrades such as advanced materials and integrated lifecycle management for hybrid service will dramatically reduce operating costs of the engine by extending the life of critical components.”
Florent Chauvancy, Safran Helicopter Engines EVP OEM Sales, added: “The Ardiden 3Z represents a very powerful complement to the ZA10 because of its exceptional performance, along with low operating and maintenance costs. This announcement marks a new step forward in demonstrating Safran ability to offer hybrid propulsive solutions for tomorrow’s mobility solutions.”
Zunum ZA10 in currently depicted configuration. Underwing pods are new addition and batteries in wings are smaller than previous illustrations
Kumar claims the ZA10 will operate at costs around $250 per hour. For comparison, a local flight school near your editor rents an instrument flight equipped Piper Geronimo Apache for $255 per hour cash – $265 credit card. Kumar claims operating costs are 60- to 80-percent lower for the Zunum craft than “comparable conventional aircraft.” According to Wikipedia, these costs are based on using power grid electricity instead of exclusively jet fuel and include “replacing the rechargeable battery packs every six months after 1,000-1,500 cycles.”
Ground testing in Chicago area facilities has been ongoing, with flight tests originally scheduled for 2019. Through the fourth quarter of this year and into early 2019, the total power system will be upgraded and tested in stages. The Ardiden 3Z engine will be tested in France and the U. S., then integrated with a modified Rockwell Turbo Commander test vehicle in 2019. With similar weights and performance to the ZA10, the Rockwell will provide valuable data as testing progresses. The powerplant package and batteries will be well tested before they are integrated in to the first Zunums.
Rockwell Turbo Commander will take on lop-sided look with conventional turboprop on one wing and electric ducted fan on the other
Zunum expects to deliver its first ZA10’s in “the early 2020s,” with upgrades to successive prototypes until the start of certification in 2020 to 2021.
Dominic Gates, writing for the Seattle Times, explains the “evolution of Tesla-style lithium ion battery technology” is crucial to the project, “Yet the rapid changes to that technology are complicating the effort.” Batteries will change a great deal between now and the ZA10’s first flight, and even more by the time the airplane is certified for passenger service. Zunum engineers, “Anticipate having to redo the battery certification process multiple times even after that, as the technology improves.”
Zunum’s chief technical officer, Matt Knapp, said the uncertainty about the shape, size, or weight of the battery pack is, “Driving my mechanical engineers nuts. They are having to figure out how to accommodate a changing energy source and size over the lifetime of the aircraft… We don’t have a crystal ball to lock down a (battery) production partner for 2022,” when Zunum wants to start final Federal Aviation Administration (FAA) certification of the airplane. Knapp explains this means recertification and requalification as new batteries become available.
To avoid issues such as battery overheating that grounded early 787 Dreamliners, “Knapp said the fundamental design requirement for Zunum’s battery system is that two or more cells can overheat without spreading to the entire pack and creating a fire, according to the Times… How to do this is pretty well known. It’s a matter of doing it in a lightweight and consistent manner.“
That near-mythical 10X (of current lithium cells’ energy density) battery hangs out there on the distant horizon, promising automobiles that can exceed 1,000 miles range, or light aircraft that can carry four at Cessna-like distances. Right now, we have two-place trainers good for an hour’s laps around the circuit, and the hope for improvements soon. OXIS Energy, a UK-based company, has achieved 425 Watt-hours per kilogram at the cell level, and looks to go higher in the near future.
Lithium-Sulfur – A Worthy Alternative?
Promoters of lithium-sulfur batteries suggest their products have several desirable characteristics and performance boosts that may transcend the limits of lithium-ion cells. Sion Power, for instance, claims availability of their Licerion battery with an even better 500 Watt-hours per kilogram and 1,000 Watt-hours per liter.
OXIS Energy’s graph of current and future performance for their lithium-sulfur batteries
On the same track, OXIS Energy has announced they have a demonstrated 425 Wh/kg cell, expected to rise to 450 Wh/kg by the end of the year and to 500 by the end of 2019. These numbers, as those for Sion’s cells, are about double or greater those for the best lithium-ion batteries now being sold. Inside EVs reports, “On the module level, energy densities now stand at 300 Wh/kg, but by the end of 2019, OXIS Energy hopes to reach 400 Wh/kg.” (Their bolding)
OXIS’ 16-Amp-hour pouch cells are currently available for High-Altitude Pseudo Satellite use and Sion’s batteries have been used in Airbus’ Zephyr HAPS program.
OXIS works along several development lines, and CEO Huw W. Hampson-Jones explains their direction and future.
Note that battery management systems, packing, and wiring for these cells will reduce the total capacity per kilogram, although they should still be more potent per pound than their lithium-ion competitors. Several other factors come into play that add to lithium-sulfur cells’ attractiveness. The cells can be fully discharged without damage, for instance, something that would shorten the life of a lithium-ion battery significantly. They have a broader temperature tolerance range than lithium-ion. And they can withstand nail penetration without bursting into flames while continuing to deliver their rated voltage.
An even more brutal test pits an OXIS battery pack against a NATO 5.56 mm round (roughly equivalent to a .22 caliber long rifle shell).
OXIS is working on packs to HALE aircraft and other drone use, and on a 30 kW-hr battery pack for a two-seat light aircraft under development. All this bodes well for future light aircraft and larger electric airframes.
Horizon Energy Systems (HES), originally based in Singapore, has pursued lightweight hydrogen propulsion systems for the last 12 years, primarily for amall drones. Going larger, the company announced plans today for Element One, “the world’s first regional hydrogen-electric passenger aircraft.”
HES Element One will fly four on 14 hydrogen-powered motors
A four-passenger, 14-motored (!) monoplane, Element One will carry the lucky foursome 500 to 5,000 kilometers (310 to 3,100 statute miles). This distributed power system claims “virtually no change to its current drone-scale systems,” which is a little puzzling, considering the largest of such systems produces no more than 1,000 Watts. The scale of the Element One and its power packs is ambiguous, with illustrations showing a nine-axle trailer with attached solar panels ostensibly powering the on-site production of H2.
HES fueling station uses solar power to generate hydrogen, then stores it in easily swapped pods that plug into motors
One illustration depicts a drone-launching site with fuel pods possibly approximating the size of the units that will be used on Element One. These are larger and their scale relative to the people in the illustration gives an approximation of their size.
H2 containers plug into power modules, appear to have controls for interaction with motor
The pods are part of an autonomous refueling system developed by HES and its partner H3 Dynamics, working from Aerospace Valley, an R&D center in France. They note, “One of H3 Dynamics’ divisions specializes in ultra-light hydrogen energy systems for aeronautical applications (drones), light mobility (soldier systems) or data capture in remote areas.” This pairing has established partnerships with a wide variety of European firms, academic and industrial organizations.
Dedicated refueling trolleys will retrieve used fuel pods, insert freshly charged units
That range will enable greater performance than that of other technologies, according to HES founder Taras Wankewycz. “It’s now possible to break past the endurance limits of battery-electric flight using HES’ ultra-light hydrogen energy storage in a distributed propulsion arrangement. Element One’s design paves the way for renewable hydrogen as a long-range fuel for electric aviation.” Range will depend on whether the hydrogen is stored in liquid or gaseous form, according to HES.
Much like other regional aircraft, Element One can open, “new aerial routes between smaller towns and rural areas using an existing and dense network of small-scale airports and aerodromes.” As noted before in this blog, that vision parallels that of William T. Piper, who saw his Cubs and Tri-Pacers landing on grass fields all over rural America, connecting village and towns that would otherwise not have airline access.
On the infrastructure front, HES partners with Wingly, a French startup offering “flight sharing services for decentralized and regional air travel.” Emeric de Waziers, CEO of Wingly, explains his firm’s hopes in this new field. “We analyzed the millions of destination searches made by the community of 200,000 pilots and passengers on our platform and confirm there is a tremendous need for inter-regional transport between secondary cities”, says. “By combining autonomous emission-free aircraft such as Element One, digital community-based platforms like Wingly and the existing high-density network of airfields, we can change the paradigm. France alone offers a network of more than 450 airfields but only 10% of these are connected by regular airlines. We will simply connect the remaining 90%.”
Element One with solar-powered fueling support system
To support that network of airports, “HES announced its plans to begin associating on-site hydrogen generation with fuel cell powered unmanned aircraft across a network of hydrogen-ready airports, in preparation for larger-scale electric aircraft such as Element One. HES is now in discussion with industrial-scale hydrogen producers to explore energy-efficient refueling systems using renewable solar or wind energy produced locally.”
With plans to fly it first aircraft in 2025, HES has time to develop a viable prototype, test it, and make that craft ready for production. Its plans are similar to that of the German HY4 flying into a “hydrogen-ready” network of regional airports. Certainly, the expansion of solar-powered H2 in both countries will mean “clean hydrogen” could be a potent power source in the future.
The University of Waterloo (Ontario, Canada – not far from Niagara Falls) News, reported, “Chemists make breakthrough on the road to creating a rechargeable lithium-oxygen battery.” Dr. Linda Nazar, Canada Research Chair in Solid State Energy Materials, led a team that “Resolved two of the most challenging issues surrounding lithium-oxygen batteries, and in the process created a working battery with near 100 per cent coulombic efficiency.”
The new work, which appears this week in the journal Science, Proves that four-electron conversion for lithium-oxygen electrochemistry is highly reversible.” Waterloo is the first to achieve this, doubling electron storage in lithium-oxygen (Li-O2 – also known as lithium-air) batteries. The video below touches on this and a great many other chemistries.
Dr. Nazar explains, “There are limitations based on thermodynamics. Nevertheless, our work has addressed fundamental issues that people have been trying to resolve for a long time.” As noted in the abstract for the Science paper, when Dr. Nazar and her colleagues changed from using an organic electrolyte to an inorganic molten salt, and replaced a porous carbon cathode to “a bifunctional metal oxide catalyst,” they reduced cell degradation and electrolyte consumption. This extended cycle life and produced near 100-percent Coulombic efficiency (almost every electron that goes into the battery is stored and available for output when called upon).
They achieve the near-theoretical energy density of Li-O2 cells while giving a “highly-reversible” charge/discharge characteristic and long life.
The lead author on the study is Chun Xia, a postdoctoral fellow, and co-author is Chun Yuen Kwok, a PhD student, both in Nazar’s lab.
The Natural Sciences and Engineering Research Council of Canada in part funded the project through their Discovery Grants and Canada Research Chair programs, along with the U.S. Department of Energy’s Joint Center for Energy Storage Research.
The abstract for the Science article, “A high-energy-density lithium-oxygen battery based on a reversible four-electron conversion to lithium oxide,” includes reasons lithium-oxygen cells have not been successful up to now.
Batteries based on lithium metal and oxygen could offer energy densities an order of magnitude larger than that of lithium ion cells. But, under normal operation conditions, the lithium oxidizes to form peroxide or superoxide. Xia et al. show that, at increased temperatures, the formation of lithium oxide is favored, through a process in which four electrons are transferred for each oxygen molecule (see the Perspective by Feng et al.). Reversible cycling is achieved through the use of a thermally stable inorganic electrolyte and a bi-functional catalyst for both oxygen reduction and evolution reactions.”
Since lithium-oxygen batteries could store up to 10 times more power than their “conventional” lithium cousins, rail-car-sized batteries could act as backups for a green energy grid. “Storing excess wind and solar power and delivering it on demand.”
So far, the Nazar team’s batteries have no degradation out to 150 cycles. As they demonstrate further charge/discharge cycles, they will eventually show their ability to take on the big jobs of the future. Although today’s lithium-oxygen batteries require further development, the idea of a 10 times improvement in energy density and long cycle life would certainly find a place in the green flight realm.