H2, Where Are You?

Elon Musk publicly disdains hydrogen-powered automobiles, but then he has $5 billion riding on his battery megafactories and continued success with his Tesla line of automobiles.  Others with a more disinterested point of view discuss H2’s difficulties – and its promise as a vehicle fuel.

America, for instance, has a mere 128 hydrogen fueling stations, and the European Union only 143 as of February 2012.  Even with planned expansion of this infrastructure (California is spending $180 million in private and public funds on a planned 46 stations), the landscape might not be ready for large numbers of fuel cell vehicles for a decade or more.


For comparison, there are about 29,000 battery-charging stations in the U. S., with both government and private enterprise offering such services.  The Kohls store and all Walgreens Pharmacies in my area have plug-in stations for EVs, for instance, and the I-5 freeway, from British Columbia to Baja, California, has stations every 25 to 50 miles.  With battery-powered EV and hybrid sales exceeding 250,000 in the last decade, this technology is an accepted part of the transportation infrastructure.

Highly modified Lange Antares flies on fuel cells powered by hydrogen in large wing tanks

Highly modified Lange Antares flies on fuel cells powered by hydrogen in large wing tanks

Because, at least in battery-supporting developers’ minds, hydrogen has issues that require solutions before it can become a viable liquid fuel or power fuel cells for millions of vehicles.

To counter the objections, the U. S. Energy Department has launched the $1 million H2 Refuel H-Prize.  “This two-year competition challenges America’s engineers and entrepreneurs to develop affordable systems for small-scale, non-commercial hydrogen fueling. These projects will continue to deploy hydrogen infrastructure across the country to support more transportation energy options for U.S. consumers, including fuel cell electric vehicles (FCEVs).  Successful entries will install and test systems that generate hydrogen from resources available at most homes, like electricity or natural gas, and provide the hydrogen to fuel vehicles. This competition plans to offer a $1 million cash prize to the team that demonstrates the best system.”

The Department notes that, “Hydrogen infrastructure remains the most critical barrier to the widespread adoption of FCEVs,” and that “both government and industry are focused on identifying actions to encourage early adopters of FCEVs, by conducting coordinated technical and market analysis and leveraging other alternative fueling infrastructure to enable cost reductions and economies of scale. For example, infrastructure being developed for alternative fuels such as natural gas, as well as fuel cell applications including combined heat and power, backup power and fuel cell forklifts, can help pave the way for mainstream hydrogen vehicle infrastructure.”

ENFICA by Turin Polytechnic professor Giulio Romeo has flown since 2010, set records.  Model below uses fuel cells, solar power to stay aloft for extended periods

ENFICA by Turin Polytechnic professor Giulio Romeo has flown since 2010, set records. Model below uses fuel cells, solar power to stay aloft for extended periods

The Energy Department takes credit for reducing the cost of automotive fuel cells by 50 percent since 2006, doubling fuel cell durability and reducing the amount of platinum by 80 percent since 2005.  Their H-Prize competition will provide incentives to teams who will have one year to design a system, find partners and a site to install that system, “and register for the competition before submitting data and designs to a team of independent judges.”  The judges will select top teams as finalists, who will then have seven months to build, install and prepare their systems for testing.

Registration to compete in the H-Prize and more information is available on the H2 Refuel website.

In recent workshops with industry leaders, the DOE has discussed goals of producing low-cost hydrogen at $2.30 per kilogram for “forecourt” or on-site production (1,500 kg/day) and $2.00 per kilogram for centralized (50,000 kg/day) by 2020, and reducing hydrogen delivery from the point of production to the point of use in consumer vehicles to <$3/gallon of gasoline equivalent (gge) by 2015 and to <$2/gge by 2020 (delivery only, all costs in 2007$).

Since the Toyota FCV holds five kilograms of H2 in two 10,000 pounds-per-square-inch pressurized tanks, delivery of such fuel requires larger, extremely high-strength tanks for storage or transportation – one challenge to confront.  Luckily, aerospace manufacturers have created processes such as filament winding to make such tanks lightweight as well as strong.

But the $2 gge fuel cost would mean a measly $10 per tankful on the FCV, good for over 300 miles, and very competitive with batteries.  Consumer Reports lists the vagaries of current pricing: “There is no established cost for a kilogram of hydrogen but at a Washington, D.C., station several years ago it went for about $8 per kg. That would work out to about 13 cents per mile, which is much more than an electric vehicle (typically 3 to 5 cents). Still, Toyota is likely to provide free hydrogen fill-ups as part of the lease plan or purchase price. That follows the lead of Hyundai, which offers a fuel-cell version of the Tucson SUV.  A Department of Energy study estimates a cost of $4.49/kg for dispensed hydrogen from natural gas.”

In follow-up entries, we’ll look at whether fuel cell-powered aircraft make sense from a physical and economic sense, new technologies that show promise for EV use, and the environmental costs, as well as benefits, of hydrogen power.


Solar Flight SUNSTAR – a New High-Flyer

Eric Raymond has been designing and building solar-powered aircraft for 28 years, and flew Sunseeker 1 across the United State in 1990, Sunseeker 2 over the Alps in 2009, and has started touring Italy in the world’s first two-seat sun-powered aircraft, the Duo.  After three such outstanding efforts, what direction will his new design take?

He took away any mystery on that today by unveiling his fourth aircraft, an optionally manned, high altitude platform, SUNSTAR.  Eric claims, “more performance potential than any of the other projects now under development.

“Compared to other solar UAVs (unmanned aerial vehicles) being developed, the Sunstar promises higher flight speeds in a turbulence-tolerant design, for operation in real world conditions.”

“Sunstar takes advantage of sailplane aerodynamic design philosophy to achieve the lowest possible power requirement to maintain flight at high altitudes.”  It takes technology tested on the Sunseeker Duo “to a whole new level.”

Having reached station altitude, the central, pusher propeller can deploy.  Its slow turning will use minimum power for greatest endurance

Having reached station altitude, the central, pusher propeller can deploy. Its slow turning will use minimum power for greatest endurance.  Illustration courtesy Solar-Flight

Capable of unmanned flight for months at a time, the airplane can also fly with a pilot for shorter missions, but its primary mission is as an unmanned telecommunications platform, staying on station longer than humanly tolerable.  Eric Raymond adds this perspective, “”What we are designing is known as an atmospheric satellite, which operates and performs many of the functions as a satellite would do in space, but does it in the atmosphere. Uplink and downlink speeds will be far better than a satellite, due to the shorter distance (than from a space satellite).”  At the same time, one Sunstar aircraft serves a much larger ground area than any land-based tower.

The airplane, now in advanced design stage, will have the best coverage of solar cells ever achieved, according to Solar-Flight.   “A proprietary lamination of a new type of solar cell forms a perfectly smooth skin. For maximum power at low sun angles some solar arrays are mounted on the sides of the aircraft.”

With pusher propeller holding altitude on minimum power, "climb" propellers fold neatly onto sides of nacelles for minimum drag.  Courtesy: Solar-Flight

With pusher propeller holding altitude on minimum power, “climb” propellers fold neatly onto sides of nacelles for minimum drag. Illustration courtesy Solar-Flight

The three-motor configuration allows the airplane to take off on the front motors, climb to altitude, and deploy the very large pusher propeller at the rear of the cargo/pilot pod.   Once that propeller, optimized for high altitude, holds the airplane’s station altitude, the two motors on the booms shut down and their propellers fold back to minimize drag.  Solar-Flight adds, “This central motor is designed for the low power cruise condition, for minimal power consumption while on station.

In an email, Eric explains, “There are good reasons for this configuration.  If you remember, when the Voyager flew around the world, they shut off an engine for more efficient cruising.  In this case, the very large prop needed for high altitudes can’t get enough ground clearance, so take off is performed with that prop folded back, as per the attached renderings.”

Sunstar showing folded rear propeller which can only be opened when the airplane is at altitude

Sunstar showing folded rear propeller which can only be opened when the airplane is at altitude.  Illustration courtesy Solar-Flight

Eric shares his long-term hopes for the project.  “…We will not start construction until enough funding is in place to finish the prototype.  Our business plan details two years to first flight, and production examples could be flying a year after that.  A lot depends on payload requirements.”

Sunstar’s design relies on a modular system configurable for a variety of missions. The interchangeable central pod can acts as a multi seat cockpit, or an un-manned instrument pod. “A pressurized cockpit for the occupants is also in the planning stage. The wingspan can be changed for different missions, by eliminating some wing sections. “

To be flown initially with a pilot on board, then optionally manned, the airplane will eventually achieve fully autonomous operation, subject to the governing country’s regulations.   “The inclusion of a manned cockpit in the prototype allows much more freedom in testing, considering the restrictions placed on un-manned aircraft over populated areas.”  From the beginning, all controls will be “fly-by-wire,” probably necessary because of the long span and the ability to add and remove wing panels for different missions.  Prototypes of SUNSTAR’s systems are already flying in Solar Flight’s flagship, the Sunseeker Duo.

All systems to be used on Sunstar have been tested on the Sunseeker Duo.  Photo courtesy Solar-Flight

All systems to be used on Sunstar have been tested on the Sunseeker Duo. Photo courtesy Solar-Flight

Eric hopes to attract strategic partners, who would be able “to help define mission-specific optimization and bring the project to completion.”  Eric invites those with an interest in developing this project to “Visit our web site for in flight video footage of our current state-of-the-art solar powered airplanes.”

{ 1 comment }

Graphene 3D Lab, Inc. has demonstrated that graphene can be easily mixed with thermoplastics commonly used in fused deposition modeling (FDM) 3D printers. The company has demonstrated a mixture of plastics and graphene that can be turned into nanocomposite material filament which can then be used within any standard FDM 3D printer.  They have managed to craft a functioning battery which may be incorporated into a 3D printed object during printing. These filaments show good thermal and electrical conductivity and are shown in the video forming a 3D printed battery.

Different components require separate “printings” at present, but company CEO Dr. Daniel Stolyarov explains that future iterations of the process will be able to simultaneously produce multiple material parts.  His corporate biography lists significant accomplishments. “In his previous role at Energetiq, Dr. Stolyarov and his team won the 2011 Prism Award for the Laser-Driven Light Source they developed. He has also co-authored papers with Nobel and Kavli prize winners, as well as members of the National Academy of Sciences.”  Others in the firm seem equally well qualified.

Graphene-loaded filaments look just like plastics familiar to "Makers"

Graphene-loaded filaments look just like plastics familiar to “makers”

The electrolyte as shown in this demonstration project is apparently solid, potentially less prone to thermal runaways and flammability than liquid equivalents.  Even at that, the demonstration battery produces as much voltage as a typical AA cell.  Since the filaments used for printing can be modified to meet functional needs, the Lab’s technology could allow manufacture of complete products, with electrical and structural qualities tuned to the product’s application.  Graphene 3D Labs explains, “Being added to polymers in the form of nanoplatelets, graphene affects materials in extraordinary ways. After the addition of graphene, materials then share many of the phenomenal properties of the graphene itself. They become mechanically strong and their thermal and electrical conductivity are greatly improved.”

Layers are now printed individually, but will be created in single process in upcoming process

Components are now printed individually, but will be created in single sweep in upcoming  process

The company explains the use of FDM technology.  “Fused Deposition Modeling is a 3D printing technology based on heating up plastic polymers and depositing them layer-by-layer through an extruder to create a physical object. It is also the most widely used method of 3D printing and the method which our current technology is based on. FDM printers have been used in a variety of disruptive ways, including: 3D printed end use parts for NASA’s Mars Rover, sporting goods, and medical devices. FDM 3D printing has even been used to create affordable prosthetics and an exoskeleton to assist the disabled.”  The idea of a self-powered prosthetic has a certain interest here, with other applications including self-powered electric vehicle parts.

Dr. Emil Greenhalgh at Imperial College London and Volvo in Sweden have been working on structural batteries for several years.  Dr. Stolyarov and his associates may be closing in on how to manufacture such components rapidly and inexpensively.  With your own FDM printer (among the most common “maker” type home systems) you may even be able to try this at home.


Solar Impulse 2, HB-SIB, flying now for several months, is being readied for a trip to Abu Dhabi, the capital of the United Arab Emirates and host city for Solar Impulse’s around-the-world flight.  From there, early in 2015, it will embark on its around-the-world flight, alternately flown by Bertrand Piccard and Andre’ Borschberg.

The program continues the drive and immense logistical planning evidenced by Solar Impulse 1’s across-America flight last year.  “What better way to demonstrate the importance of the pioneering, innovatory spirit than by achieving ‘impossible’ things with renewable energy and highlighting new solutions for environmental problems?”

This attitude will be necessary to overcome the challenges of five-day, cross-ocean flights each pilot will face, and to meet the meteorological conditions following the equator much of the way.

The bigger, heavier SI2 will cross deserts, the Great Wall of China, and repeat its journey across America on its five-month circumnavigation of the globe.  Beginning in March, 2015 from Abu Dhabi, Solar Impulse will make stops in Asia, the United States, southern Europe and North Africa before returning to the host city in July, 2015.

Solar Impulse 2 will require a great ground game, too, with a team to match

Solar Impulse 2 will require a great ground game, too, with a team to match

As with Solar Impulse 1’s flight to Morocco in June 2012, the move to depart from and arrive in Abu Dhabi has symbolic import.

“Flying to Morocco’s Ouarzazate region is filled with symbolism as it is both Solar Impulse’s and the Moroccan Agency for Solar Energy’s (MASEN’s) common message: to invest in innovative projects today for job creation and sustainable growth tomorrow.”

Abu Dhabi and Masdar, that country’s renewable energy company, will host Solar Impulse as it prepares for its flight.  The big plane will be delivered by cargo plane late in the year and begin test flights and training in January.  It will also be showcased during the World Future Energy Summit as part of the Abu Dhabi Sustainability Week, which is hosted by Masdar between January 17 and 22, 2015.

The Solar Impulse blog reports, “This well-matched partnership will show Abu Dhabi to be a center of expertise when it comes to renewable energy and at the same time Solar Impulse will demonstrate the far-reaching applications of clean energy during the first solar-powered flight around the world,” declared Bertrand Piccard. André Borschberg continued: “We have chosen this location as being the best and most suitable departure point for the round-the-world tour, due to its climate, infrastructure and commitment to clean technologies.

Pictorial of airplane's salient points, projected voyage

Pictorial of airplane’s salient points, projected voyage,  Approximately 5,000 more solar cells are involved than on Solar Impulse 1, and motors produce seven horsepower more each

Solar Impulse lists the following as a sketch of their coming flight:

  • 2 pilots, Bertrand Piccard and André Borschberg, flying one after the other in the single-seater cockpit
  • 1 airplane: Solar Impulse 2
  • Zero fuel on board
  • A 35,000 kilometer (22,000 miles) journey
  • 500 flying hours approx.
  • 10 legs approximately, some lasting more than 5 days and nights
  • A 5-month mission (March-August 2015)
  • A 60 people support team

This massive support team seems appropriate for the massive airplane, with a wingspan larger than a Boeing 747 Intercontinental.  The journey, at ultralight speeds, will be a test of patience and technology, and one which we will follow avidly.



Chip Yates Awarded Louis Bleriot Medal by FAI

Chip Yates, founder and head of the Flight of the Century, has been honored by the Federation Aeronautique International for records set in 2013.  Chip’s web site announced the honor last week.

“Record-setting entrepreneur and pioneer Chip Yates will be honored on October 16 by the World Air Sports Federation (Federation Aeronautique Internationale) for changing the course of aviation history.

“Yates has been selected to receive the FAI’s Louis Bleriot Medal for his record-setting flights in 2013, which established new international landmarks in speed, altitude and distance for electric flight.

Chip Yates Setting records in 2013 in Long-ESA which Wired Magazine said "stomps Cessnas"

Chip Yates Setting records in 2013 in Long-ESA which Wired Magazine said “stomps Cessnas”

“The award will be presented at the Opening Ceremony of the FAI General Conference in Pattaya, Thailand, where Yates will become part of the distinguished list of honorees since 1936 who have made outstanding contributions to aeronautics and astronautics. Prior honorees include the inspirational Dick Rutan and other aviation greats from the US, Switzerland, Austria, Canada, Italy, Finland, Australia, the UK and elsewhere.

“Yates paid tribute to those who have worked with him to push electric aviation to the forefront. ‘This is thanks to your efforts to turn a far-fetched dream into reality,’ he said. ‘And we’ve only just begun!’”

The FAI web site explains the Medal was established in 1936 in memory of Louis Bleriot, first to fly the English Channel and former Vice-President of the FAI.  Although “three Medals may be awarded each year to the respective holders of the highest records for speed, altitude and distance in a straight line established in the previous year by light aircraft of the first three sub-classes, as defined in Section 2 of the Sporting Code,” such records are not easily attained.  Chip is the first winner in four years, for his record in his Long-ESA (Electric Speed and Altitude) in the C-1b Group VI class: Electric Land Airplanes weighing 1,102-2,205 pounds.   His flights last year between September and November included this noteworthy record, ratified earlier this year by the FAI.

Altitude: 4,481meters (14,697 feet) World Record on a C Aeroplane (c-1b Landplanes: take-off weight 500 to 1000 kg) on 10.07.2014: Altitude in (sustained) horizontal flight: 4,439 meters (14,559.9 feet).  Interestingly, the FAI does not mention the fact that his airplane was powered by electricity, noteworthy because the record beat those of previous fossil-fuel powered aircraft.


ORNL Makes It Two for Two

Oak Ridge National Laboratory has announced that their researchers have built and demonstrated a high-voltage (5 V) lithium, solid-state battery with a usable life of more than 10,000 cycles, at the end which test the battery retains more that 90-percent of its original capacity.  That makes two such claims in a week, with ORNL’s battery comparable to that developed by Nanyang Technology University (NTU) and reported on in this blog last week.

ORNL solid state battery shows high Coulombic efficiency, high capacity retention after 10,000 cycles

ORNL solid state battery shows high Coulombic efficiency, high capacity retention after 10,000 cycles

ORNL points out that, “For a given size of battery, the energy stored in a battery is proportional to its voltage. Conventional lithium-ion batteries use organic liquid electrolytes that have a maximum operating voltage of 4.3 V. Operating a battery above this limit causes short cycle life and serious safety concerns.”

“In this latest study, the Oak Ridge team replaced the conventional liquid electrolyte with a ceramic solid electrolyte of lithium phosphorus oxynitride (Lipon), and used a LiNi0.5Mn1.5O4 cathode and Li anode at a charge voltage to 5.1V.”

The abstract for Juchuan Li, Cheng Ma, Miaofang Chi, Chengdu Liang, and Nancy J. Dudney’s paper, “Solid electrolyte: the key for high-voltage lithium batteries,” in Advanced Energy Materials shows that the team used an entirely different chemistry from NTU’s titanium oxide-based design.

Voltage profiles of the (a) LiNi0.5Mn1.5O4 solid-state lithium battery and (b) a LiNi0.5Mn1.5O4 liquid battery discharged at different rates. The battery was charged at C/10 before each discharge measurement. Li et al.Click to enlarge.

Voltage profiles of the (a) LiNi0.5Mn1.5O4 solid-state lithium battery

Voltage profiles of the (a) LiNi0.5Mn1.5O4 solid-state lithium battery and (b) a LiNi0.5Mn1.5O4 liquid battery discharged at different rates. The battery was charged at C/10 before each discharge measurement. Li et al.Click to enlarge.

(b) a LiNi0.5Mn1.5O4 liquid battery discharged at different rates. The battery was charged at C/10 before each discharge measurement

This work demonstrates that replacing the conventional liquid electrolyte with a ceramic solid electrolyte of lithium phosphorus oxynitride (Lipon) eliminates the limit of conventional lithium-ion batteries. A model battery of LiNi0.5Mn1.5O4/Lipon/Li has been operated over 10,000 cycles at a charge voltage to 5.1V.  The solid state battery retains more than 90% of its original capacity after 10,000 cycles. Such a battery has a cycling lifetime of more than 27 years with a daily charge/discharge cycle, exceeding the lifetime of most devices and even vehicles. This work infuses new life into the existing chemistry of high-voltage lithium batteries.  

Here, readers can see the first page of the group’s report (with the following five pages coyly shaded to enforce payment of standard fees journals charge for enhancing your knowledge).  Seeing more costs extra, the scientific equivalent of a peep show.

Along with NTU’s work, Sakti3 and Toyota have recently released information on solid-state batteries that show great promise for higher energy density, greater safety and longer lives for batteries.


Audi Drives Hockenheim with “Bobby”

“Bobby” is Audi’s computerized “driver” for their RS 7, which they demonstrated before thousands of spectators in the grandstands at the 4.574 kilometer (2.842 mile) Hockenheim race track in Baden-Wurttemberg, Germany on October 19.

The video, despite the somewhat sometimes annoying narration, gives a good impression of the run, showing the acceleration, braking and cornering through all 17 turns from both inside and outside the car.  The inside views belie the speed the car attains, looking a bit unearthly by the precise, smooth lines the car takes, the envy of any “real” race car driver.

Green Car Congress reports, “The Audi RS 7 piloted driving concept car drove a clean racing line at the Hockenheimring—full throttle on the straights, full braking before the corners, precise turn-in and perfectly metered acceleration when exiting the corners. Forces of over 1.3 g occur during braking, and lateral acceleration in the corners can reach 1.1 g. Tests on the track in Hockenheim suggested an expected top speed of 240 km/h (149.1 mph) and a lap time of 2 minutes and 10 seconds.”  The track record, by the way, was 1:13.780 set by F1 driver Kimi Räikkönen,in a McLaren in 2004.

Audi, of course, could not but help be proud of their accomplishment.  Professor Doctor Ulrich Hackenberg, a Technical Development Board member at Audi AG, said, “The top performance by the Audi RS 7 today substantiates the skills of our development team with regard to piloted driving at Audi. The derivations from series production, particularly in terms of precision and performance, are of great value for our further development steps.”

Dazzling array of sensors, all hidden in bodywork, enable RS 7 to attain race-car speeds - driverless

Dazzling array of sensors, all hidden in bodywork, enable RS 7 to attain race-car speeds – driverless

Unlike Google’s Priuses and Lexuses plying the roads in the Bay Area and their bubble cars scooting around their Mountain View campus, Audi’s driverless car retains its smooth lines and hides all its sensors within its bodywork.   The number of devices on the RS 7, including a differential GPS and 3D camera system front and rear, front, rear and top view cameras, infrared camera, front and rear radar sensors, front, rear and side crash sensors, and ultrasonic sensors, are a bit overwhelming, but allow the car to sense its position on the track within 1 centimeter.  That’s probably responsible for the crowd-pleasing parking job at the run’s finish.

According to Green Car Congress, “Experts from Volkswagen Group Research, the Electronics Research Laboratory (ERL) and Stanford University (both in California) are supporting Audi as partners in the further development of piloted systems.”  Doubtless, the group will continue to refine the technology and produce more practical applications for non-competition drivers.


We’ve witnessed several attempts to produce an “artificial leaf,” a device emulating the photosynthesis of plants, but providing hydrogen and oxygen that could power fuel cells in electric vehicles instead of plant sugars to make trees and flowers grow.  One of the biggest problems so far has been the rare and costly materials necessary to generate hydrogen.

Ècole Polytechnique Fédéral de Lausanne (EPFL) scientists has come up with a low-cost alternative, using abundant materials called perovskites and budget electrodes to produce hydrogen from water with a 12.3 percent conversion efficiency – a record for fairly common materials.

Perovskites are a calcium titanium oxide mineral that come in a variety of colors and can be bog-common or extremely rare, approaching rare earth mineral status.  The CaTiO3 used by Michael Grätzel is of the common variety, but that doesn’t seem to detract from its performance as a hydrogen-production agent.

That, and the inexpensive materials used in the device’s electrodes cause Jingshan Luo, a post-graduate student on the project, to note,” “Both the perovskite used in the cells and the nickel and iron catalysts making up the electrodes require resources that are abundant on Earth and that are also cheap, However, our electrodes work just as well as the expensive platinum-based models customarily used.”

The work, done at the Laboratory of Photonics and Interfaces at EPFL, is led by Grätzel, who directs the Laboratory of Photonics and Interfaces at the Polytechnique.  According to his university biography, “He pioneered the use of mesoscopic materials in energy conversion systems, in particular photovoltaic cells, lithium ion batteries and photo-electrochemical devices for the splitting of water into hydrogen and oxygen by sunlight. He discovered a new type of solar cell based on dye sensitized nanocrystalline oxide films. Mass production has started in October 2009. Author of over 1,000 publications, two books and inventor of more than 50 patents, his work has been cited over 134,000 times (h-index 167) making him one of the 10 most highly cited chemists in the world.”  He’s also won awards that take up a very long paragraph in his bio.

Pulling on past experience, Grätzel and his team have created a solar converter with “spectacular” performance.  It could generate electricity directly, but that would limit its energy use to simultaneous delivery and keep that energy from being used at night.  Grätzel and his researchers chose to store the hydrogen generated by their device.

Profusion of bubbles show perovskites actively making hydrogen and oxygen in water exposed to sunlight.  Photo: EPFL

Profusion of bubbles show perovskites actively making hydrogen and oxygen in water exposed to sunlight. Photo: EPFL

One indicator of the converter’s performance is the fact that it uses only two cells to generate hydrogen.  Jingshan Luo explains, “A voltage of 1.7 V or more is required for water electrolysis to occur and to obtain exploitable gases.  This is the first time we have been able to get hydrogen through electrolysis with only two cells!”  Usually, three or more 0.7 V silicon cells are needed, whereas just two 1.0 V perovskite cells are enough, showing a big bump in efficiency for the more common material.

Grätzel explains, “Once you have hydrogen, you store it in a bottle and you can do with it whatever you want to, whenever you want it,”  burning it in a boiler or engine, or using it in a fuel cell to generate electricity when desired.  Either way, the combustion releases only water vapor.

Michael Grätzel and his research team of Jingshan Luo, Jeong-Hyeok Im, Matthew T. Mayer, Marcel Schreier, Mohammad Khaja Nazeeruddin, Nam-Gyu Park, S. David Tilley, and Hong Jin Fan, published their paper, “Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts,” in the September 26 issue of the journal, Science.

The profusion of tiny bubbles escaping from the electrodes as soon as the solar cells are exposed to light say it better than words ever could: the combination of sun and water paves a promising and effervescent way for developing the energy of the future.  Since most such discoveries have applications for solar cells, hydrogen generation, and possibly batteries, we anxiously await the team’s even more efficient perovskite breakthrough.


Reduced weight and component volumes are important for both cars and aircraft, allowing lighter overall construction and greater flexibility in fitting those components into compact spaces.  The U. S. Department of Energy has set 2020 targets for things like batteries and power inverters – the device that turns direct current from batteries into alternating current to run electric motors. 

Researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL)used 3D printing and “novel silicon carbide (SiC) wide band gap (WBG) semiconductors to craft a prototype power inverter for electric vehicles that is lighter and can handle more power than current units.  It nearly meets the DOE’s power density and specific power targets and exceeds the efficiency target handily.


DOE 2020 target

ORNL prototype

Power density

13.4 kW/L

13.33 kW/L

Specific Power

14.1 kW/kg

11.5 kW/kg


>94% Power


 DOE has put 1.45 million into integrating WGB technology, novel circuit architectures and advanced packaging into electric drive systems.  They hope to “reduce cost, improve efficiency, and increase power density.”

50-percent 3D printed now, ORNL's smaller, lighter power inverter will eventually be a product of 100-percent additive manufacturing

50-percent 3D printed now, ORNL’s smaller, lighter power inverter will eventually be a product of 100-percent additive manufacturing

Heading this effort, ORNL’s Madhu Chinthavali led the Power Electronics and Electric Machinery Group on this project.  His ongoing efforts can be reviewed in this PowerPoint presentation.

Besides providing greater efficiency over a wide range of temperatures than conventional circuitry, wide bandgap technology enables devices to perform more efficiently, possess higher inherent reliability, and operate at higher frequencies.

Additive manufacturing helped researchers explore complex geometries, increase power densities, and reduce weight and waste while building ORNL’s 30 kW prototype inverter.

ORNL’s design and its advantages were augmented by the use of additive manufacturing (3D printing) to produce the actual hardware.  According to Chinthavali, “With additive manufacturing, complexity is basically free, so any shape or grouping of shapes can be imagined and modeled for performance. We’re very excited about where we see this research headed.”

The ORNL reports that, “Using additive manufacturing, researchers optimized the inverter’s heat sink, allowing for better heat transfer throughout the unit. This construction technique allowed them to place lower-temperature components close to the high-temperature devices, further reducing the electrical losses and reducing the volume and mass of the package.

“Another key to the success is a design that incorporates several small capacitors connected in parallel to ensure better cooling and lower cost compared to fewer, larger and more expensive ‘brick type’ capacitors.”  3D printing also enables rapid changes within one production run, enabling improvements to be incorporated in the next prototype as quickly as computer drawings can be downloaded to the computer.

The prototype 30-kilowatt inverter is liquid-cooled and features 50 percent printed parts.  Future efforts will have up to 3D printing and strive for even lighter, more compact structures – half the size of currently available commercial vehicle units.  Chinthavali projects an inverter with four times the power density of their prototype.

Others involved in this work include Curt Ayers, Steven Campbell, Randy Wiles and Burak Ozpineci.

Research for this project was conducted at ORNL’s National Transportation Research Center and Manufacturing Demonstration Facility, DOE user facilities, with funding from DOE’s Office of Energy Efficiency and Renewable Energy.


Five Years, 685 Entries, Great Readers

Today marks the completion of your editor’s fifth year collecting and reporting on progress that will make electric aircraft and green flight a reality.  It is only possible with the well informed, highly intelligent and unbelievably kind readers who respond to these efforts.

Thank you for your continued readership and excellent critiques of fact and opinion.  Let’s make the future of our dreams happen.