Those of us with car experience that dates back to the 70’s may well remember the challenges of using aluminum in a vehicle’s powerplant as exemplified by the ill-fated aluminum engine block used in Chevy’s Vega. The prime motivation for its use of course was the substantial weight reduction offered by aluminum over cast iron. Advances since have enabled aluminum to find its niche in today’s powerplants and realize the weight reduction. Now though, a different and more alluring attribute of aluminum may have it poised to become a key component in the powerplant of next generation cars; the sought-after panacea known as the fuel cell. According to Brian Osterberg, CEO of HyAlEnergy, it is the Holy Grail for fuel cells.
Aluminum (or aluminium as it’s known outside of North America) is the third most abundant element comprising 8% of the earth’s crust. It was first produced in an impure form from salts only about 200 years ago. Later work led to it being extracted in a pure form from bauxite ore. However, due to the difficulty in extracting it at that time, aluminum was more expensive than gold. It wasn’t until the advent of electricity and the Hall-Héroult electrolytic process at the end of the 1800’s that aluminum became economical enough to be used in a wide variety of applications including another epic fail; aluminum wiring. Aluminum though requires an enormous amount of energy to extract it from bauxite. New aluminum production uses nearly 100 times the energy of steel, which helps to explain the huge disparity in last year’s new production between the two (1,600 million metric tons of steel versus only 51 for aluminum). Nevertheless, nearly 1 billion tons of aluminum have been produced since the 1880’s and 75% of it is still in use today. Most of that is within buildings, cables, machinery, and transportation with a little less than 5% used for packaging such as beverage cans and foil trays. The great thing about aluminum is that it’s completely recyclable with no loss in quality or volume. This ability essentially renders aluminum a renewable resource; especially if the energy to recycle it comes from renewable sources such as hydropower as it does at the Alcoa plant in Quebec, Canada.
What makes aluminum intriguing for vehicle power is that it has one of the highest specific energy densities (specific energy x energy density) of any material; nearly twice that of gasoline or diesel. Apparently, most of the extraordinary amount of energy used in its initial production is retained in the metal (over 8 kWh/kg) and ready to be released given the proper environment. That environment is water. At essentially room temperature, pure aluminum in contact with water releases energy that can be used to generate electricity or extract hydrogen from the water as aluminum loves to bond with oxygen. About half of the energy released from the aluminum water reaction becomes heat, which can also be utilized. The use of aluminum to generate electricity has been well documented of late following the announcement of Israeli startup, Phinergy, partnering with Alcoa to commercialize aluminum-air batteries. However, its use as a possible hydrogen generator for onboard vehicular fuel cells is less publicized. Recent breakthroughs in the process of obtaining on-demand hydrogen from water and aluminum have made it seemingly viable despite a 2008 report by the DOE (updated in 2010) indicating it was unlikely to be suitable for onboard vehicular applications.
The main challenge of the process is keeping the aluminum in contact with water. The byproduct of the aluminum-water reaction is aluminum oxide (alumina). Alumina is the same material produced at the final stage of the process used to extract it from bauxite and can therefore be easily recycled. This intriguing attribute renders aluminum essentially the only known closed-loop fuel. As the reaction begins though, alumina coats the surface of the aluminum in a process called passivation that prevents the reaction from continuing. The alumina must be continually cleared from the surface of the aluminum either by mechanical or chemical means to keep the reaction going. How that is accomplished is key to also controlling the reaction in order to continually generate the required amount of hydrogen to power the fuel cell. There are several competing methods to accomplish this; some of which may hold promise.
One method proposed by Franzoni F, et al. in a 2010 paper in the International Journal of Hydrogen Energy employed a metal grinder, which could be powered by the process, to reduce the aluminum to 20-50 micron particles. Aluminum of this size can be completely combusted in as little as 5 msec depending on ambient pressure and temperature. While adding a grinder to a vehicles powerplant doesn’t seem practical or desirable, it does demonstrate that sufficiently small particles can be successfully fed into the aluminum-water reactor to generate required amounts of hydrogen using this process. Imagine fueling up on aluminum flakes and water.
A more practical method was developed by another Israeli startup, Alchemy Research. Their process, dubbed Alydro for Aluminum Hydro, initially raises the temperature to the melting point of powered aluminum (900 deg C) where steam is then injected into the molten aluminum to initiate the reaction. Since alumina cannot adhere to liquid aluminum, the reaction can continue. The heat generated from the reaction is then used to sustain the elevated temperature. A working prototype of their reactor was demonstrated in November 2011. Alchemy was purchased by another Israeli company, CompuLab, in January of 2013 and it is uncertain what further developments, if any, have been made since. Their website and its content are no longer accessible and CompuLab has no information about the acquisition on their website. Simple posts on Alchemy’s Twitter and Facebook pages are all that can be found to indicate they are now fully owned by CompuLab.
Another, and perhaps more interesting, method has been developed by the Phillips Company (not Philips), a pharmaceutical non-profit based in the Choctaw Nation of Oklahoma. This method uses what’s called Catalytic Carbon, uniquely activated by Phillips, as a catalyst to promote and control the splitting of water using aluminum. The CC-HOD (Catalytic Carbon – Hydrogen on Demand) process was demonstrated publically in January of 2013 resulting in the production of hydrogen at up to 30 gallons per minute. The technique can purportedly use any type of water including saltwater. The technology was licensed to a UK firm, Bion Energy of the Bion Group; however, no further information has been forthcoming since that time though Phillips continues to offer Catalytic Carbon for hydrogen production.
Yet another interesting method has been developed by Jerry Woodall of LED fame. An MIT graduate having worked at IBM, Purdue, and now UC Davis; Woodall has pioneered much of the LED technology used in products from DVD players to laser pointers. While working with gallium aluminum arsenide, he discovered that gallium serves as a great catalyst to control the aluminum-water reaction in what’s now known as the Woodall Process. Woodall formed an early stage startup, HydroAlumina, to commercialize his work. It currently offers a stationary reactor to generate ultra pure hydrogen and alumina but no further news on the vehicle front.
In another potential process developed by the late Dr. AVK Reddy, sodium hydroxide is used as a catalyst to control the process. Dr. Reddy, a former medical doctor, discovered the process and spent 7 years developing the technique in India before announcing it to the press in late 2012. Osterberg, a long time colleague of Dr. Reddy’s, indicates that he and Reddy’s remaining team are continuing the work and hope to have further announcement by the end of 2014.
While these methodologies differ in how they tackle the challenge of keeping the reaction going and controlled, they share several common advantages. In each case, the pure alumina byproduct can be recovered and recycled. While recycling alumina uses quite a bit more energy than recycling scrap aluminum (70% versus only 5% of the energy used to make it from scratch), it produces primary aluminum, which is suitable for any application including vehicular components. Recycled scrap aluminum produces only secondary aluminum with limited applications such as beverage cans. Any catalyst used in the processes is not consumed and can be reused repeatedly. Furthermore, the processes are purported to be able to produce sufficient quantities of hydrogen to power a vehicle fuel cell on-demand. It takes nearly 9 kilograms each of aluminum and water to produce 1 kilogram of hydrogen. The water/steam byproduct from burning the resulting hydrogen can be recovered with about 65% efficiency to then be reused in continuing the process. Alchemy Research indicated that aluminum-water “fuel” in quantities equivalent to a tank of gasoline can power a car for close to 1,500 miles; nearly three times farther than some of the best gasoline-powered models. So with all these appealing qualities, what is holding back the use of aluminum for on-board, on-demand hydrogen within vehicular fuel cells?
From a technical standpoint, there are likely several kinks left to be worked out. It’s difficult to know since, if there have been any further refinements to these processes; they seem to now be shrouded in secrecy (or obscurity). From a logistics standpoint, there would certainly be much work to be done. While dotting the landscape with hydrogen refueling stations could be avoided, the packaging and distribution of aluminum would need to be sorted along with the collection and transportation for smelting of the alumina byproduct.
Another issue is the global supply of both aluminum and water. The 2008 DOE report indicated that it would take 575 million metric tons of aluminum per year to power 300 million vehicles. That’s more than half the aluminum ever produced. Keep in mind also that, given the lifespan of aluminum used in buildings, machinery, and transportation; the amount to be regularly recycled is limited. So it’s a good bet that much more primary aluminum would need to be produced, at least initially. However, Forbes just reported that aluminum demand is low while capacity remains high so the industry could likely use a shot in the arm. An equal amount of water is also required but can be recovered through the combustion of hydrogen. Additionally, at least one of the methods is able to utilize the earth’s abundance of salt water.
The economics of aluminum-water fuel are particularly interesting. Aluminum is not cheap and is considerably more expensive than gasoline at the moment though gasoline continues to rise. A gasoline gallon equivalent (GGE) of hydrogen is 1 kilogram, which again requires nearly 9 kilograms of aluminum to produce. At today’s price of nearly $2 per kilogram, a GGE of aluminum would cost $18 compared to a gallon of gasoline at today’s average price of $3.35. However, for every kilogram of aluminum used nearly 2 kilograms of pure alumina are produced, which can be sold for recycling back into aluminum. Today, the going price for alumina is essentially a percentage of the price of aluminum (about 20%) so the two fluctuate together. There is a push to price alumina on its own merits, which could increase the price considerably given the right circumstances. The bottom line is that the possibility exists for aluminum fuel to cost next to nothing.
One thing is sure though, generating hydrogen on-board the vehicle would be a lot simpler than transferring and storing hydrogen for use in vehicular fuel cells. While further development efforts of these intriguing possibilities seem to be under wraps, they may very well be continuing with some well-heeled partners. Maybe it’s no wonder that Toyota is foregoing the current electric vehicle craze in pursuit of hydrogen-powered fuel cell vehicles?!