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Understanding Fuel Cells

Understanding Fuel Cells

By Jeff Youngs,
While gasoline has been the most logical fuel choice for motorized vehicles for more than a century, there's no question that a shift to another fuel source will occur. Demand for oil is increasing globally, and as we all know, the world's oil supply is not unlimited. In addition, greenhouse gases can cause serious environmental consequences.

Many people believe that the logical solution for this problem eventually leads to fuel cells. Yet, bringing fuel cell vehicles to the point of mass production is not easy. The issues the auto industry faces are complex in terms of technology, fuel infrastructure, safety, and cost.

How fuel cells work

A fuel cell vehicle is essentially a hybrid vehicle that operates in a manner similar to today's existing gas/electric hybrids. A fuel cell is powered by an electric motor, which gets its electricity from a fuel cell stack rather than an internal combustion engine, as in today's hybrids. While the internal combustion engine gets its energy from gasoline, the fuel cell stack gets its energy from hydrogen. The hydrogen is combined with oxygen to generate electricity, which is in turn directed to the electric motor.

Similar to existing hybrids on the market that can operate at times solely on power from the electric motor, fuel cell vehicles can use the fuel cell stack alone to power the motor. However, most models include a secondary device, most commonly a battery, for added performance in more demanding driving situations, such as passing or climbing a grade.

Inside the fuel cell

Fuel cells break down hydrogen into positive- and negatively-charged particles, creating electricity, which in turn powers the vehicle. Regardless of the type of fuel cell, vehicles with this type of engine are much more energy efficient than gas- or diesel-powered (internal-combustion) vehicles. The most efficient internal combustion engine has about 30 percent efficiency rate, meaning that 70 percent of the energy generated from the engine is lost as heat. Fuel cells, on the other hand, deliver from 40 to 70 percent efficiency. What's equally impressive is that the only emission from a fuel cell is water. Internal combustion engines, on the other hand, produce emissions that cause smog (smog-forming emissions) and carbon dioxide, which is thought to contribute to global warming.

Making hydrogen

One of the biggest issues facing the auto industry is how to cost-effectively produce and deliver the hydrogen fuel that would be required to make mass production of fuel cells realistic. Despite the fact that hydrogen is the most common element in the universe, it is often bound with other common molecules, such as water, methanol, natural gas, or even gasoline. As a result, the hydrogen must be extracted from its primary source through a process that breaks the hydrogen bond with the other element(s). Currently, the most common way to produce hydrogen (which is used as a power source in various industries) is to extract it from natural gas, using a steam reforming process. Water, wind, solar, and biomass (plant material, vegetation, or agricultural waste that is used to produce fuel) are all possibilities for generating some of the hydrogen supply, in much the same way that these clean resources provide some of our electricity now.

Storage problems mean short range

Another issue is how to store enough hydrogen onboard a vehicle to provide a cruising range similar to the 300- to 350-mile range of today's vehicles. Currently, fuel cell vehicles run on pressurized hydrogen. In theory, to increase the driving range, the hydrogen must simply be placed under greater pressure, allowing more of it to be stored in the same tank. But, as one can imagine, the concerns for leakage and other problems, especially in the event of a collision, grow as storage pressure increases.

Despite the lingering bad reputation that hydrogen may have received from the Hindenburg blimp accident in 1937 (although it was later determined that hydrogen was not the cause), hydrogen requires about the same level of safety precaution as gasoline. The biggest difference is that hydrogen burns clean, meaning that it isn't necessarily visible when it's burning. A greater issue is meeting city, state, and federal government standards for storing hydrogen.

A hydrogen fueling station on the corner

The final challenge to making fuel cells a reality is the infrastructure that would allow vehicles to be refueled conveniently and quickly. The good news is that the refueling process for fuel cell vehicles is already comparable to that of gasoline-powered vehicles today. However, putting a fueling station that dispenses hydrogen on every corner is no simple task.

What may make a network of hydrogen fueling stations a reality are two things: many cities already have underground pipelines that deliver hydrogen for industrial use, and many gas stations are already set up to dispense compressed natural gas using a system that could be modified to dispense pressurized hydrogen. Plans are in place to build a network of hydrogen fueling stations in California, Florida, and the Northeast, although the timing for these plans is continually changing.

Next steps

Real-world research is helping to further the development of fuel cell vehicles, but it will be quite a while before they are on sale at the local dealership. When they are available, they will likely be sold alongside gasoline-powered vehicles and hybrids, at least initially.

Oil and gas are likely to remain dominant energy sources until around 2040, according to a study conducted by Royal Dutch/Shell, although the study did indicate that fuel cell vehicles could account for 25 percent of new-auto sales in industrialized nations as early as 2020.

The years between now and the time fuel cell vehicles arrive in showrooms will be a time of education within the industry and for consumers. Each type of alternative-fuel vehicle, whether it is a hybrid, or runs on compressed natural gas, ethanol, or some other fuel source, is helping to bridge the gap between today's internal combustion vehicles and the vehicles of tomorrow.
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