When Cella Energy CEO Stephen Voller demos little squares of white fluffy material, he isn’t holding cotton swabs from a local pharmacy. Neither is he tossing a handful of cereal when he showcases tiny white pellets that look like Cheerios dipped in sugar. The materials he presents are complex nanoparticle compounds, which may hold the answer to the long-pursued challenge of safely and effectively storing hydrogen fuel.
"Each one of these when heated will release hydrogen gas," he says of the small heap of pellets in his palm. “You get about a balloon worth of hydrogen gas from that."
A near-perfect solution to energy and emission problems, hydrogen fuel is efficient and clean – it generates water as its waste product. But because it’s a gas, it’s hard to store and transport. It’s also potentially dangerous when stored in pressurized tanks.
Cella’s method attempts to get the positive out of this alternative fuel while solving some of its problems. The company uses ammonia borane, a solid chemical compound that consists of one boron and one nitrogen atom accompanied by six hydrogen atoms. When heated more than 100 degrees centigrade, the compound releases hydrogen, but not in a very friendly form. “The trouble is that it melts when you heat it so you end up with this horrible gunk,” says Voller. “So if you use it in your laptop or your car you will gunk up your car or your laptop.”
So Cella cofounder Stephen Bennington, a scientist from Rutherford Appleton Laboratory near Oxford, UK, devised a clever solution. In his method, ammonia borane molecules are encapsulated inside the chains of polyethylene oxide, a polymer used in many industrial applications. “Polyethylene has these kind of linear chains like a rope,” Bennington says. “The ammonia borane goes inside the strands of the rope.”
To create the more useful nanostructure for storing hydrogen, the polyethylene and ammonia borane are freeze-dried into a powder and then shaped into pellets, which are coated by a layer of filter plastic. “That cleans the hydrogen and it comes out much more pure,” Bennington says, adding that the plastic pellets can be reused.
The company’s technology promises a gamut of applications, including revolutionizing the car industry. Future hydrogen-powered cars could be equipped with devices that pump the pellets into a “hot cell” where they would be heated to release the fuel, and then into a waste tank that collects the empty beads. Instead of gas stations, drivers would pull up to refueling stations to load up a few pounds of pellets and empty the waste tank.
Cella’s engineers have already started working on engine prototypes for these possible future automobiles, which Voller says he expects to have in trials within five years. The company is also investigating another approach, which Bennington calls diesel co-combustion. “If you feed hydrogen into the diesel engine it improves the combustion of the diesel so you get some small efficiency gains,” he says.
Vans and sedans won’t be running on pellets next year, but unmanned aerial vehicles might. Cella has developed pellet-based battery-life extender cartridges that fit into the aircraft’s wing and can keep drones in the air three times longer than the lithium-ion battery. Inside the cartridge, hundreds of tiny pellets can be “fired up” one by one, assuring the continuous flow of hydrogen into a fuel cell to generate electricity.
Voller and Bennington formed Cella as a spin-off from Rutherford Appleton Laboratory in 2010, and wrote a business plan on how to commercialize the technology. A few months later, Space Florida, a U.S. aerospace economic development agency, became interested in their ideas, and in late summer 2012 Cella opened an office at the Kennedy Space Center. “NASA and Kennedy have probably been the largest users of hydrogen worldwide for years because they use it in space shuttles,” Voller says.
Space Florida president Frank DiBello says: “We saw the potential of the technology and how it works – we saw that it would be a game changer. We provide space in the building that Space Florida owns and we helped them open the door to the certain markets they can have.”
It turned out there was yet another market for Cella’s hydrogen nano-compounds: radiation shielding for the people and electronics inside space shuttles and satellites. “It’s a different type of radiation than you get inside nuclear reactors on Earth because the particles are very high energy,” Voller says.
Hydrogen is known for its radiation-shielding properties, but using it for this purpose in its gaseous form is impractical. However, Cella’s thin cotton-like nanocompounds have proven to be better suited for such insulation than polyethylene, the material currently used in space vehicles. The white fluffy tissues can stop radiation 30 percent better than polyethylene. The next step is to prove if the product is a viable commercial idea, Bennington says, so Cella is looking for partners who make electronics for satellites to see if they are interested in testing the nanomaterials to extend the life of their components.
Just like with the car industry, this technology will take time to develop and test, Voller says. But if long-duration spaceflight is to become a reality, astronauts exposed to radiation longer would need better protection. “If you’re going to go to Mars, it’s going to take about two years to make the round trip,” he says. “This will keep you alive.”
Top Image: Hydrogen-containing pellets. Courtesy Cella Energy.