Fuel vs. battery

Toyota Motor Corp. is working toward a 2015 rollout of a hydrogen-powered fuel-cell electric car. By doing so, Toyota is diverging from other carmakers, which have been developing battery-powered electric cars with large battery packs. Battery-powered electric vehicles and plug-in hybrid vehicles need to be recharged from an external electricity source.

Honda and Hyundai are competing to produce fuel-cell vehicles within the next two years. Southern California fleets have tested the Honda FCX Clarity, a hydrogen fuel-cell vehicle, for more than seven years.

GM and Ford have also worked to develop fuel-cell vehicles in the past decade and are not far from joining the competition, if a market emerges.

The Chevrolet Volt was conceived as a multifuel vehicle with an electric motor and drive train that could be powered by electricity derived from several sources, including a hydrogen fuel cell. Project Driveway leased 100 hydrogen-powered Chevrolet Equinox fuel-cell vehicles to test fleets over two years to get real-world operating data.

During timed land-speed trials at Bonneville Salt Flats in 2007, the hydrogen-powered Ford Fusion 999 showed a fuel-cell car could exceed 200 mph.

Both fuel cells and battery cells create electricity from chemical reactions. However, a secondary battery cell is more like a storage unit that accepts electric energy from an external source and then releases it to an electrical load upon demand. When the energy storage capacity is depleted, a secondary battery cell must be recharged to full capacity. Discharging and recharging a battery cell is like a two-way street that uses the same reciprocal circuit path through the cell’s anode and cathode terminals.

A fuel cell requires a steady injection of fuel to keep making electricity. It is like a one-way street where fuel passes from a separate storage tank into the cell to create a chemical reaction that creates electricity.

But with a hydrogen fuel cell, stored hydrogen is forced under pressure through a proton exchange membrane with an internal chemical catalyst, such as platinum or palladium.

After the catalyst reacts, the fuel cell produces electricity and condensed water vapor as a byproduct when the hydrogen combines with ambient oxygen in the air.

The electricity is used to recharge a battery pack or drive an electric motor directly; water vapor is evacuated through an exhaust pipe. The electric motor drives the car’s wheels without harmful emissions.

The California Air Resources Board has certified that automobiles using either energy cell can be categorized as zero-emission vehicles.

Thanks to federal research incentives and funding under the Clinton, Bush and Obama administrations, much research and expense have been devoted to refining battery and fuel cells’ capacity and efficiency over the past 20 years.

However, while battery cell recharging infrastructure has been developing internationally over the past five years, hydrogen refueling infrastructure is just starting.

Hydrogen, the universe’s most abundant element, can be produced from many different sources, including hydrocarbon fuels and water.

During the past decade, the University of Nevada, Las Vegas, Center for Energy Research has experimented with designing a prototype hydrogen fuel-cell utility vehicle.

Student research teams have also studied how to crack hydrogen from water by using solar photovoltaic panels and electrolysis.

Las Vegas’ fleet installed a hydrogen refueling station in 2002, then tested the Honda FCX Clarity and fuel-cell bus prototypes.

The next few years will reveal whether this technology can be refreshed and accepted by the consumers.

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