Research in Alternative fuel technology

How a Fuel Cell Works

Fuel Cells use hydrogen with oxygen from air to produce electricity. The electricity generated powers a vehicle’s motor.

Fuel cells have captured worldwide attention as a clean power source for electric vehicles. Many auto manufacturers are developing EVs powered by fuel cells, generating interest and enthusiasm among industry, environmentalists and consumers.

In principle, a fuel cell operates like a battery. A fuel cell converts chemical energy directly into electricity by combining oxygen from the air with hydrogen gas. However, unlike a battery, a fuel cell does not run down or require recharging. It will produce electricity as long as fuel, in the form of hydrogen, is supplied.

Hydrogen can be produced from a variety of fuels, including gasoline, methanol, ethanol and natural gas. It can also be produced through electrolysis, a process that splits water into hydrogen and oxygen using electricity. In the future, hydrogen may be supplied from solar, wind and other renewable sources.

What are the benefits?
A fuel cell EV, powered by an electric motor, promises the air quality benefits of a battery-powered EV, combined with the driving range and convenience of a conventional gasoline engine:

• Zero or near-zero smog-forming emissions,
• Increased fuel efficiency
• Lower maintenance costs
• Impressive driving range
• A quieter, smoother ride
• Plenty of power for entertainment features, Internet connections, GPS, and more

  How the fuel cell works

The core of the fuel cell consists of a membrane electrode assembly (MEA), which is placed between two flow-field plates.

The MEA consists of two electrodes, the anode and the cathode, which are each coated on one side with a thin catalyst layer and separated by a proton exchange membrane (PEM). The flow-field plates direct hydrogen to the anode and oxygen (from air) to the cathode.

When hydrogen reaches the catalyst layer, it separates into protons (hydrogen ions) and electrons.

The free electrons, produced at the anode, are conducted in the form of a usable electric current through the external circuit. At the cathode, oxygen from the air, electrons from the external circuit and protons combine to form water and heat.

Parts of a fuel cell

Expanded Single Fuel Cell
A single fuel cell consists of the membrane electrode assembly and two flow-field plates.

Hydrogen
Hydrogen flows through channels in flow field plates to the anode where the platinum catalyst promotes its separation into protons and electrons. Hydrogen can be supplied to a fuel cell directly or may be obtained from natural gas, methanol or petroleum using a fuel processor, which converts the hydrocarbons into hydrogen and carbon dioxide through a catalytic chemical reaction.

Membrane Electrode Assembly
Each membrane electrode assembly consists of two electrodes (the anode and the cathode) with a very thin layer of catalyst, bonded to either side of a proton exchange membrane.

Air
Air flows through the channels in flow field plates to the cathode. The hydrogen protons that migrate through the proton exchange membrane combine with oxygen in air and electrons returning from the external circuit to form pure water and heat. The air stream also removes the water created as a by-product of the electrochemical process.

Flow Field Plates
Gases (hydrogen and air) are supplied to the electrodes of the membrane electrode assembly through channels formed in flow field plates.

Fuel Cell Stack
To obtain the desired amount of electrical power, individual fuel cells are combined to form a fuel cell stack. Increasing the number of cells in a stack increases the voltage, while increasing the surface area of the cells increases the current.

Learn more about the Technology Driving Fuel Cell Innovation.

Most demonstrations today involve testing one requirement at a time - freeze start, power density, cost reduction - which involves tradeoffs in other requirements. 

One company has created a 10-cell demonstration fuel cell stack, reducing the amount of platinum by 30%, and subjecting the stack to start-ups from -20° C, all without compromising performance.  Engineers employed a drive cycle testing protocol that simulated real world driving, similar to tests used by auto manufacturers today.  The protocol included starts, stops, rapid acceleration and deceleration, much harsher than steady state testing.

Freeze Start at -20° C: Freeze starts were demonstrated from -20° C.  The test lowered the fuel cell stack and its supporting systems to -20° C and then subjected the unit to a drive cycle test from start-up through power down. The unit was then allowed to cool to -20° C and the test was repeated. Fifty consecutive freeze start cycles were conducted with no degradation in performance or damage to the stack.  While we have a future goal of operating at -30° C, a -20° C temperature is well within the operating requirements for most of North America and Europe. Water generation is a by-product of fuel cell operation.  As such, managing water within fuel cells presents a substantial challenge in freezing temperatures and has been a key hurdle in the commercialization of the technology.

Durability of 2,000+ Hours or the Equivalent of More than 100,000 Driving Kilometers: The 10-cell stack was continuously operated through numerous drive cycles from August through December 2004.  Actual testing results demonstrated durability to nearly 2200 hours before a 5% reduction in performance was observed.  At this point, the test was stopped with no indication of any membrane damage - a key failure mechanism in fuel cells. The U.S. DOE goal for durability is 5,000 hours.

Reduced Catalyst Loading Cuts Costs: The new stack design incorporated a 30% reduction in platinum catalyst loading with no reduction in performance.  Baseline catalyst loading was reduced from approximately 1 mg/cm2 to approximately 0.7 mg/cm2.  Meeting performance, durability and freeze-start requirements is more difficult with less platinum catalyst.  This is a significant development that moves  towards meeting reduced cost targets, since platinum is one of the most expensive components in a fuel cell stack.

WHAT NEXT?
Our 2005 Technology goal is to demonstrate next generation automotive fuel cell stack technology that meets -25° C freeze start, costs less than $85/kW when manufactured in high volumes and achieves at least 2,000 hours of lifetime, and developing a commercially viable automotive fuel cell stack technology by 2010

As with any emerging technology, until recently, the fuel cell industry had no established technology benchmarks or milestones against which to measure progress.  However, the US Department of Energy (US DOE) recently updated its Hydrogen, Fuel Cells and Infrastructure Technologies Program’s Multi-Year Research, Development and Demonstration Plan, written in 2003, laying out industry targets for fuel cell cost, durability and performance.

Durability

For tomorrow’s consumer of fuel cell powered vehicles, durability means delivering the same level of performance and reliability they expect from today’s internal combustion technology. Using real drive cycle testing, more than 2,000 hours of durability in technology demonstration, equivalent to 100,000 kilometers under regular driving conditions.

Freeze Start Capability

Managing the water produced by fuel cells presents a challenge in freezing temperatures and, as such, to the commercialization of fuel cell technology. Companies have already achieved fuel cell stack start-up at -20°C, within 100 seconds, to 50% of the rated power for the stack. A  2010 target for stack freeze start is -30°C, in 30 seconds, to 50% rated power.

Power Density

 Reduction in volumetric power density is the ability to package the fuel cell stack into increasingly smaller spaces within a vehicle. The target of 2,500 Wattsnet/liter is more aggressive than the US DOE’s target and will go a long way towards liberating the true design potential of fuel cells in future automotive design.

 

Stack Cost

The cost of automotive fuel cells will need to be competitive with today’s internal combustion engines for the technology to be adopted widely. The target cost for the fuel cell stack, like the US DOE’s, is $30 USD/kW by 2010. Stack technology innovation, new materials development and system optimization are the drivers for achieving this cost target..

 

Technology Trend-lines

Improvements in any one of the four target areas (volumetric power density, freeze start capability, durability, or fuel cell stack cost) without impact to one or more other area, is essential to the development of a commercially viable fuel cell stack by 2010. By that time, there is the intent to develop automotive fuel cell stack technology with the following characteristics: 5,000 hours of lifetime freeze start capability to -30° C volumetric power density of 2,500 Watts net per liter fuel cell stack cost of 30 US dollars per kilowatt .

 

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Vehicular Alliance
The benefits of alliances has been demonstrated over time by the increased development activities by our partners and customers and their accelerated commercialization plans. DaimlerChrysler, Ford and Honda are now introducing fleet demonstration vehicles and have already delivered some into the hands of customers. A number of the world's major automakers have stated that they expect fuel cell vehicles to be commercially available between 2010 and 2012.