Fuel Cell Technology Gets Practical
Paula Doe, SEMI, San Jose -- Semiconductor International, 7/13/2007
Improving fluorinated materials and steady engineering work are starting to make fuel cells practical in niche markets.
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| Peter Podessor (Source: SFC Smart Fuel Cell AG) |
Key to the company's efficient fuel cells are nanomembranes from DuPont (Round Rock, Texas), which reportedly use less platinum to keep down costs and whose nanostructured surface allows the cells to be more compact. A water management system within the cell provides the source of water, so the cartridge can be pure methanol. The methanol releases its electrons directly when it meets the platinum catalyst, thus requiring no reformation steps whatsoever. The electrons are shunted around to the anode, while the protons pass through the membrane to react with oxygen from the air on the other side. The process heats the cell to ~40°C, releasing water vapor and carbon dioxide in about the same amounts as in the breath of a child.
The main commercial market, so far, is for compact off-grid power generation for recreational vehicles and boats, and for industrial uses such as remote sensing, weather stations and traffic information signals, where the fuel cell can typically extend 8 hours of operating time from a battery to up to eight days — and users are willing to pay an initial price of some $2000-$3000 for the ability to work off-grid for extended periods. SFC is also supplying compact power supply units to eight European military organizations for field testing, significantly reducing the soldiers’ weight load and allowing longer operating time away from base. One electric bike maker is using the cells, and Podesser said the light electrical vehicle niche of scooters, golf carts and metropolitan transport will likely be a big market.
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| Commercial applications of fuel cells. (Source: SFC Smart Fuel Cell AG) |
The sweet spot for the methanol cells is the 10 W to 1 kW range, said Podesser, leaving the higher power applications to hydrogen fuel cells, with their more complex required infrastructure.
Though fuel cells may still be expensive, the refill cartridges are relatively cheap and available. Podesser said the company now has some 500 points of sale across Europe. The company advertises that a 10 L refill cartridge — essentially a plastic jug of methanol with safety features — costs ~$30 (€22), which is enough power to run a satellite television for 130 hours.
Fuel cell powered cars are also making steady progress in range and reliability, reports The California Fuel Cell Partnership (CaFCP, Sacramento, Calif.). The new prototypes now have higher-pressure hydrogen tanks that hold twice as much fuel, increasing capacity to 7-8 kg for a range of 350-500 miles. With a kilogram of hydrogen roughly equivalent in energy content to a gallon of gasoline, the demonstration cars typically get 50-65 miles/kg. Improved membranes and higher-purity fuel are improving running time, with fuel cell provider UTC Power recently demonstrating 5000 hours of cell performance, close to the target for commercial vehicles, said CaFCP Director Chris White.
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Early commercial versions of the vehicles are expected to be available somewhere around 2010-2015, with volume production around 2018-2020. But hydrogen-powered buses may well be practical sooner, with state regulations requiring reduced emissions, limited fixed routes and larger fuel tanks. DOE’s recent evaluation of Oakland AC Transit’s three initial experimental prototype buses in regular service found running costs were down to about 2.5× that of diesel (excluding capital costs), while maintenance and parts costs were about 45% less.
CaFCP now has 24 hydrogen fuel stations in the Sacramento, San Francisco and greater Los Angeles areas to supply its 200 demonstration vehicles out on the road. The first of the stations has started supplying 700 bar (10,000 psi) gas for the new higher-pressure tanks. Coming this fall is a high visibility station near the highway in Sacramento that will use power generated by its solar panels in off-peak hours to produce its hydrogen from water on site.
Key to much of this improving fuel cell performance is a range of specialty fluorinated materials, including fluoroelastomers used as high-performance seals to prevent hydrogen permeation, which can adversely affect catalyst performance in the fuel stack. In addition, fluorinated fluids are used to manage and dissipate heat in the fuel stack and balance of plant areas. Particularly important are improvements in the proton exchange membranes, which selectively accept the hydrogen protons but repel the electrons, shunting them around to the anode.
Specially designed versions of these membrane molecules can improve fuel cell performance. Solvay Solexis (Milan, Italy) designed the reactive groups it adds to its polymer to have very short side chains, which Global Marketing Manager Raymond Bastnagel said makes them more efficient and durable at higher temperatures. "Our designed material with its short side chains is semi-crystalline, so it's stronger and more durable at the higher temperatures," he said.
Podesser, White and Solvay’s Vincent Meunier will be among the featured speakers discussing these ideas and other trends and technologies at the Emerging Technologies & Markets TechXPOT Renewable Energy session on Thursday, July 19 at SEMICON West in San Francisco, along with speakers from Applied Materials, Oerlikon, Dow Corning and Sunpower. For more information, visit www.semiconwest.org .
