Hydrogen Fuel Cell Cars

1. Comparing Fuel Cells with Batteries

Like batteries, fuel cells power electric drive cars by producing electricity through an electrochemical process. Both have anodes, cathodes, and an electrolyte. Unlike batteries that must be recharged or replaced periodically, fuel cells continue to produce electricity as long as they are supplied with fuel. While several types of fuel cells exist, proton exchange membrane (PEM) fuel cells are the most common being developed for vehicles because they are the simplest, produce lots of kilowatts of power in a small volume, and operate at reasonably low temperatures.

2. How a Fuel Cell Works

This is a bit of a science lesson but worth the read: The PEM fuel cell is supplied with hydrogen fuel and oxygen - actually air - and produces electricity, heat, and water. Hydrogen enters on the anode side and passes through a precious metal catalyst, typically platinum, where the hydrogen molecules split into H+ ions (protons) and electrons. The PEM (the electrolyte) passes positively charged protons and blocks negatively charged electrons. Electrons are conducted through the anode and travel through an external circuit, producing electricity on their way to the cathode. Here, they meet up with protons coming through the membrane and with oxygen, or air, to form two oxygen atoms with a strong negative charge. This negative charge attracts the two H+ ions, which combine with an oxygen atom and two of the electrons to form a water molecule. Water vapor and heat are the only byproducts of a fuel cell, compared to the array of noxious gases emitted through the tailpipe of an internal combustion engine.

3. Stacks of Fuel Cells are Needed

A single fuel cell produces less than one volt of electricity, so many fuel cells are combined into fuel cell stacks and many stacks are connected together to produce the power needed to drive a vehicle. They are connected in series to produce high voltages and in parallel for high currents.

4. Fuel Cells are Very Efficient

When connected to an inverter - a device that converts output power from DC (direct current, the type of electricity in your car) to AC (alternating current, the type in your house) - and powering an electric motor that drives the wheels, a fuel cell car's overall efficiency is about 60 percent. In comparison, the overall efficiency of a typical gasoline-fueled vehicle is only about 20 percent.

5. Long Time Coming and a Ways to Go

The fuel cell was discovered in 1838 by Christian Friedrich Schönbein in Germany, with the first one built by Welsh scientist Sir William Robert Grove in 1843. These amazing devices were pretty much forgotten until the 1950s, when General Electric scientists developed the first practical fuel cell for the Gemini space capsule. In 1966, General Motors built the first hydrogen fuel cell road vehicle, the Electrovan. Cost remains the greatest impediment to widespread use of fuel cells, with much of this cost involving the precious metal catalysts required for a fuel cell's operation. Research is under way to reduce costs by using fewer precious metals, less costly alternatives, and by the recycling of platinum, especially from catalytic converters where precious metals like platinum are widely used. Another challenge is the lack of an infrastructure to distribute hydrogen to motorists, although this is the focus of much activity on the part of energy companies, automakers, other commercial interests, and government at many levels.

Credits: greencar.com