Gregoire's CleanTech Blog

Methanol: The New Hydrogen - advances in methanol synthesis, coupled with improved fuel cell technology, could make it a viable alternative to gasoline.

Hydrogen has been getting plenty of hype as a potential replacement transportation fuel, for cutting carbon dioxide emissions and reducing dependence on fossil fuels. But methanol would be far better than the more reactive and volatile hydrogen, argues George Olah, a chemist and Nobel laureate, in a new book, Beyond Oil and Gas: The Methanol Economy.

Olah notes that methanol, a clean-burning liquid, would require only minor modifications to existing engines and fuel-delivery infrastructure (see "The Methanol Economy"). And manufacturing it could even make use of carbon dioxide, a source of global warming. Methanol's benefits have long been understood -- now recent advances in methanol synthesis and methanol fuel cells could make this fuel even more attractive.

Currently, about 90 percent of the worldwide production of methanol (CH₃OH) is derived from methane (CH₄), the main component of natural gas. Today's methods of making methanol have two stages: converting methane into syngas, a mixture of primarily carbon monoxide and hydrogen, and then into methanol. Although these steps have become more efficient over time, the elimination of the syngas step could save money, since it currently accounts for up to 70 percent of the cost of making methanol.

In an effort to eliminate this cost, Olah and his colleagues have explored ways of converting methane directly into methanol. "You take methane and stick in just one oxygen atom," says Olah, director of the Loker Hydrocarbon Research Institute at the University of Southern California (USC). "Easily said, but not so easily done." The problem is that methane is chemically inert, and combines readily with oxygen only at high temperatures. A catalyst helps, but commonly used catalysts themselves work only at 300 degrees Celsius or higher. At these temperatures, most of the methanol produced is oxidized to carbon dioxide and water. Indeed, methanol yields from such reactions can be as low as 2 percent.

Recently discovered lower-temperature catalysts offer better yields, says Roy Periana, associate professor of chemistry at USC. Using a platinum-based catalyst dissolved in concentrated sulfuric acid at 200 degrees Celsius, Periana has achieved a methanol yield of more than 70 percent. He's now looking for less expensive catalysts, and has found some promising ones.

Olah and his colleague Surya Prakash, professor of chemistry at the university, have developed an alternative method for converting methane to methanol, using a halogen such as bromine. In the presence of special catalysts and at less than 250 degrees Celsius, methane reacts with bromine to form methyl bromide (CH₃Br) and hydrogen bromide (HBr). Methyl bromide then reacts with water to form methanol. The bromine from the hydrogen bromide can be recovered by reaction with air, and reused.

Making methanol from natural gas -- which still involves fossil fuels and increases carbon dioxide in the atmosphere -- is just the first step, says Olah. Chemists have long known that methanol can be made by combining carbon dioxide and hydrogen. Such a process requires considerable energy, for example, to harvest the hydrogen from water, but this energy could come from carbon-free sources such as nuclear or wind power. The carbon dioxide could be captured from flue gases, and eventually directly from the atmosphere, he says.

In such a system, the carbon dioxide released by burning methanol would be cancelled out by the carbon dioxide captured to make it. So the process would be carbon neutral, and the methanol produced would be a convenient liquid fuel that could replace petroleum-based fuels. If the carbon dioxide comes from air and the hydrogen from water, this method of making methanol would be like fast photosynthesis: "We don't have to wait for plant life to slowly convert excess carbon dioxide into hydrocarbons," Olah says. "We can substitute for Mother Nature."

Olah emphasizes that the methanol produced in this way would not be a new energy source, but simply a convenient way of storing energy. Its advantage over hydrogen would be the ability to use existing engines and infrastructure with only minor modifications.

In many ways, with its low emissions and an octane rating of 100, methanol is already a better fuel for internal combustion engines than gasoline. A methanol engine can run at a higher compression ratio, and is easier to cool. But methanol has some drawbacks: it has lower vapor pressure than gasoline, which makes engines sluggish on cold starts, and it burns with an invisible flame, which could be a safety hazard, since it would be hard for emergency workers to detect in an accident, for example. To mitigate these problems, methanol today is usually blended with 15 percent gasoline to make a fuel mix known as "M85."

Methanol is an even better automotive fuel when used in combination with fuel-cell technology, says Paul Erickson, assistant professor in mechanical engineering at the University of California, Davis. Fuel cells, which convert chemical energy directly into electricity, are more efficient than engines that burn fuel. The hydrogen fuel cell, in particular, has been widely proposed as a clean and efficient alternative to gasoline-powered internal combustion engines. Erickson's laboratory has a functioning hydrogen fuel-cell bus with an onboard reactor that "reforms" methanol to produce hydrogen for its fuel cells. "We completely avoid having to store hydrogen," Erickson says.

Onboard "reforming," however, consumes space and energy. In 1993, Prakash, Olah, and a team at the Jet Propulsion Laboratory in Pasadena, CA, jointly invented a fuel cell that runs directly on a mixture of methanol and water. The cell's positive and negative electrodes are separated by a membrane designed to allow only protons from the methanol to migrate from one electrode to the other. Early versions of this membrane, however, allowed some methanol to get across and react with oxygen at the second electrode, which reduced the voltage of the cell and wasted energy in the form of heat.

In 2001, Prakash and his colleagues developed a new membrane that is both cheaper and more resistant to crossover. With this refinement, the direct methanol fuel cell gives an efficiency of 35 percent, about twice that of an internal combustion engine, but well short of its theoretical efficiency of 97 percent.

The direct methanol fuel cell is currently too expensive to be used in passenger cars. Its high cost comes mainly from the platinum and ruthenium used as catalysts. Prakash and others are developing a variety of approaches to reduce the amount of catalyst needed: making the catalyst more active, increasing its surface area, and using nanoscale methods. When this technology matures, Erickson believes it might replace the hydrogen fuel cell. "An inexpensive, high-power direct methanol fuel cell is the Holy Grail," he says.

By Chandra Shekhar

Source : Technology Review

High Efficiency Solar Cells Coming to Earth

The race to bring the high efficiency solar cells used in space down to earth has intensified. The Rochester Institute of Technology’s NanoPower Research Lab just announced $846,000 in new funding from the Department of Defense to advance its development of nanotechnology structures in space solar cells.

These multijunction cells achieve efficiencies close to 40 percent by using expensive III-V semiconductor materials that are not economical in terrestrial applications. There are many researchers experimenting with the application of novel nanotechnologies to photovoltaics—carbon wires, tubes etcetera. RIT and a number of others are applying quantum dots to the existing space technology—triple-junction cells consisting of gallium arsenide, indium phosphide and geranium layers—to increase the absorption efficiency and light spectrum.

The incumbent space applications suppliers are gearing up for a terrestrial market. Emcore recently joined the Defense Research Projects Agency’s (DARPA) Very High Efficiency Solar Cell (VHSEC) program, which aims to double the efficiency of terrestrial solar cells over the next 50 months. VHSEC is providing $53 million in funding to program participants over the next few years, the largest commitment to solar research to date. The semiconductor component maker has reached 36 percent efficiency and plans to be in production this year. SpectraLab, the leading developer of solar cells used in space, holds the efficiency record at 39 percent. It says the terrestrial market is still a few years off.

A few stealth startups hope to get there sooner. Cyrium Technologies, which closed $3 million in venture capital financing in December, plans to reach 45 percent efficiency levels in 2007. The high price of silicon is making the semiconductor III-Vs more attractive, but the real challenge of bringing the material and fabrication costs down remains.

Space Island Group (SIG) has a bigger and bolder idea—producing solar energy with space satellites and beaming the power down to earth. In a press release out this month, SIG says it hopes to secure a $200 billion, 20-year energy purchase agreement with China or India to cover 5 percent of the project costs. SIG may also have to find some otherworldly project backers. The largest project financing to date, the channel tunnel, at $15 billion, involved a global syndicate of 220 banks.

Lien: EcoLog :: High Efficiency Solar Cells Coming to Earth.

Cheap Hydrogen Fuel : GE says its new machine could make the hydrogen economy affordable, by slashing the cost of water-splitting technology.

Among the many daunting challenges to replacing fossil fuels with hydrogen is how to make hydrogen cheaply in ways that don't pollute the environment. Splitting water molecules into hydrogen and oxygen using electricity from energy sources such as wind turbines is one possibility -- but it's still far too expensive to be widely practical.

Now researchers at GE say they've come up with a less expensive, easy-to-manufacture apparatus that can directly produce hydrogen via electrolysis for about $3 per kilogram -- a quantity roughly comparable to a gallon of gasoline -- down from today's $8 per kilogram. That could make it economically practical for future fuel-cell vehicles that run on hydrogen.

Electrolyzers are fairly simple technologies: water is mixed with potassium hydroxide electrolyte and made to flow past a stack of electrodes. Electricity causes the water molecules to crack into hydrogen and oxygen gases, which bubble out of the solution. The chemistry makes a good high-school science experiment -- but commercial-scale quantities of hydrogen are extracted far more cheaply from natural gas.

The core problem in improving electrolyzers for hydrogen manufacture is not how to improve the fundamental conversion efficiency, says Richard Bourgeois, an electrolysis project leader at GE Global Research in Niskayuna, NY. "You can only make it so much more efficient; there isn't a lot you can do. So we've attacked the capital costs," he says.

Today's electrolyzers are made of metal plates bolted together manually, with gaskets between them, and the whole unit is typically housed in a chamber made of the same metals used in the electrodes, says Bourgeois. The materials are expensive and assembly requires costly labor.

Bourgeois' research team came up with a way to make future electrolyzers largely out of plastic. They used a GE plastic called Noryl that is extremely resistant to the highly alkaline potassium hydroxide. And because the plastic is easy to form and join, manufacturing an electrolyzer is relatively cheap.

Inside the plastic housing, metal electrodes still do the same job. But because GE is using less electrode material, the reactivity of the electrodes' surfaces is improved. To do this, the researchers borrowed a spray-coating process -- normally used to apply coatings for parts on jet engines -- to coat the electrodes with a proprietary nickel-based catalyst with a large surface area.

GE has demonstrated the technology in a prototype, and is now building a larger production module -- one that can produce

1 kilogram

of hydrogen per hour -- for testing in its labs later this year. A machine of that scale could be attached to small electricity sources to produce hydrogen on the side. The technology also has the potential to be massively scaled up to create a hydrogen gas station.

GE's new electrolyzer could be ready for production in a few years. "You can talk about transitioning to a hydrogen economy, but really these things don't move unless the economics are there," Bourgeois says. "This takes enough capital cost out of the whole electrolyzer system, so when you buy this and amortize it over so many years, you compete with gasoline."

Paul Bakke, an electrical engineer and program manager at the U.S. Department of Energy in Golden, CO, says a cheap electrolyzer could be a key component of the future hydrogen economy. "As far as I know, GE is the only one who has tried to tackle this problem," he says. "Assuming GE is successful in being able to produce these things with a high level of reliability and low cost, it will break through the barrier that has traditionally been there for electrolyzers -- namely, the capital cost barrier."

Bakke adds: "I would say it's an important piece; it may not be the only way to make hydrogen, but it's an important piece. Natural-gas reforming may be a near-term bridge, but in order to get away from the environmental concerns, we will have to go to electrolysis, derived from wind turbines and solar panels and so forth."

By David Talbot

Source : Technology Review

Practical Fuel-Cell Vehicles : Hybrid vehicles operating in an unusual environment are lifting the prospects of fuel cells.

The future of fuel-cell vehicles is already happening in an unlikely proving ground: forklifts used in warehouses. Several manufacturers are testing forklifts powered by a combination of fuel cells and batteries -- and finding that these hybrids perform far better than the lead-acid battery systems now typically used. In some situations, in fact, they could pay for themselves in cost savings and added productivity within two or three years.

The adoption of the technology points to a promising hybrid strategy for finally making fuel cells economically practical for all sorts of vehicles. While researchers have speculated for years that hydrogen fuel cells could power clean, electric vehicles, cutting emissions and decreasing our dependence on oil, manufacturing fuel cells big enough to power a car is prohibitively expensive -- one of the main reasons they are not yet in widespread use. But by relying on batteries or ultracapacitors to deliver peak power loads, such as for acceleration, fuel cells can be sized as much as four times smaller, slashing manufacturing costs and helping to bring fuel cell-powered vehicles to market.

The forklift hybrids use ultracapacitors, devices similar to batteries but able to deliver higher bursts of power. The fuel cell powers the forklift as it drives through a warehouse, while at the same time the cell charges the ultracapacitors. The ultracapacitors kick in to lift a pallet.

"If you had to do that with just fuel-cell power, you'd need a fuel cell about four times as large, which would be too big," says Michael Sund, spokesperson for Maxwell Technologies, an ultracapacitor manufacturer. "It would dwarf the forklift, and it would also be very expensive. Being able to downsize the fuel cell makes it smaller, lighter, and cheaper."

The use of the fuel-cell hybrids in forklifts could bode well for the auto industry. Cars and SUVs, like forklifts, have peak power demands. When cruising, they use less than one-quarter of an engine's maximum power, which is sized to provide acceleration and sustained power up long hills, says Brian Wicke, who's developing fuel-cell systems at GM.

Batteries and ultracapacitors could provide at least some of the accelerating power, allowing the fuel cell to be smaller. Last year, GM rolled out a concept car featuring a hybrid system, although it will be after the end of the decade before such a vehicle is available. Other major automakers are also pursuing the hybrid technology.

In addition to supplying peak power, ultracapacitors and batteries give fuel-cell vehicles the ability to recapture energy from braking, as happens now with commercial gasoline-battery hybrid vehicles. This can make the system much more efficient, especially in applications such as city driving. A vehicle powered by a fuel cell alone would not have this ability.

"You can't take energy into a fuel cell. You've got to have a battery," says Brian Barnett at Tiax in Cambridge, MA, a company that has provided analyses of fuel cells for the U.S. Department of Energy. "Why you would put an electric drive train system on the road, and not have the ability to accept regenerative braking is beyond me."

Exactly how much batteries could lower the cost of fuel cell-powered cars and SUVs would vary as car makers balanced the different strengths of fuel cells and batteries. Batteries and ultracapacitors can provide power at less cost than a fuel cell, but they run out of energy quickly. The strength of fuel cells is that they can keep running as long as they have hydrogen, and can be refueled faster than a battery can be recharged.

In the future, the mix of batteries and fuel cells could be optimized for different kinds of vehicles, says GM's Wicke. "There is a very broad mix of possibilities, starting with a fuel-cell vehicle which is augmented by a battery, all the way to a battery vehicle augmented by a fuel cell -- and you could have almost any mix in between," he says. GM is currently focused on the first approach, using a battery to boost the performance of a still relatively large fuel cell, while improving efficiency by capturing energy from braking.

While hybrid systems could help make fuel-cell vehicles more affordable, other obstacles need to be overcome before these vehicles take over the roads. Fuel cells can run only as long as hydrogen is available, and that will require better ways of storing hydrogen in the vehicle and distributing it. One of the reasons forklifts are a first application of hybrid fuel cells is that they never move far from their filling station.

By Kevin Bullis

Source : Technology Review