Fuel Cells

Fuel cells efficiently generate electrical power without causing pollution. Unlike power sources that use fossil fuels, fuel cells use hydrogen and oxygen and therefore the by-products from an operating fuel cell are heat and water. The hydrogen atoms enter a fuel cell at the anode and oxygen at the cathode.

Why should I be aware of this?

It is probably the only energy generation technology to offer a combination of benefits including low or zero emissions, high efficiency and reliability, multi-fuel capability, flexibility, durability, scalability and ease of maintenance. There is no noise pollution as fuel cells operate silently.

As long as fuel is supplied, the fuel cell will continue to generate power. Fuel gets converted to energy through an electrochemical process, and not by combustion. This makes the process clean, quiet and two to three times more efficient than fuel burning.

Benefits

• High efficiency
• Virtually no gaseous emissions (SOx, NOx, or air toxic metals)
• No combustion needed
• Quiet operation
• No moving parts in the energy converter
• Fuel flexible
• Both high- and low-temperature fuel cells can be used for different applications
• Unattended or remote operation
• Modular design can be used to match size with performance requirements
• Demonstrated endurance and reliability

All about fuel cells

The first fuel cell was invented in 1839 by Sir William Grove who called it a gas voltaic battery. Fifty years later, scientists Ludwig Mond and Charles Langer coined the term fuel cell while attempting to build a practical model to produce electricity.

Basic workings of a fuel cell

Though the basic workings of a fuel cell may not be difficult, it’s far more complicated to build inexpensive, efficient, reliable ones. The choice of electrolyte is important in designing efficient fuel cells. Today, the main electrolyte types are alkali, molten carbonate, phosphoric acid, proton exchange membrane (PEM) and solid oxide. The first three are liquid electrolytes; the last two are solids.

The type of fuel also depends on the electrolyte. Some cells need pure hydrogen, and therefore demand extra equipment such as a “reformer” to purify the fuel. Other cells can tolerate some impurities, but might need higher temperatures to run efficiently. Liquid electrolytes circulate in some cells, which may require pumps. The type of electrolyte also dictates a cell’s operating temperature–“molten” carbonate cells run hot, just as the name implies.

Greater efficiency

The fuel cell will be a more efficient competitor to many other energy­ conversion devices, including the gas turbine in power plants, car gasoline engine, the laptop battery etc. Combustion engines like the turbine and the gasoline engine burn fuels and use the pressure created by the expansion of the gases to do mechanical work. Batteries convert chemical energy back into electrical energy when needed.

A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances.

Commercial uses

Fuel cells have endless possibilities for commercial exploitation. Major automakers are developing fuel cell car on a commercial basis . Fuel cells are used to power buses, boats, trains, planes, scooters, forklifts, even bicycles. There are fuel cell-powered vending machines, vacuum cleaners and highway road signs. Miniature fuel cells for cell phones, laptop computers and portable electronics will soon have miniature fuel cells.

It is also being used in hospitals, credit card centers, police stations, and banks to provide power to their facilities. Wastewater treatment plants and landfills are using fuel cells to convert the methane gas they produce into electricity.

Types of fuel cells

• Alkali fuel cells. They operate on compressed hydrogen and oxygen and generally use a solution of potassium hydroxide (chemically, KOH) in water as their electrolyte. Efficiency is about 70 percent, and operating temperature is 150 to 200 degrees C, (about 300 to 400 degrees F). Cell output ranges from 300 watts (W) to 5 kilowatts (kW).
• Molten Carbonate fuel cells. They use high-temperature compounds of salt (like sodium or magnesium) carbonates (chemically, CO3) as the electrolyte. Efficiency ranges from 60 to 80 percent, and operating temperature is about 650 degrees C (1,200 degrees F).
• Phosphoric Acid fuel cells. They use phosphoric acid as the electrolyte. Efficiency ranges from 40 to 80 percent, and operating temperature is between 150 to 200 degrees C (about 300 to 400 degrees F).
• Proton Exchange Membrane fuel cells. Work with a polymer electrolyte in the form of a thin, permeable sheet. Efficiency is about 40 to 50 percent, and operating temperature is about 80 degrees C (about 175 degrees F).
• Solid Oxide fuel cells. use a hard, ceramic compound of metal (like calcium or zirconium) oxides (chemically, O2) as electrolyte. Efficiency is about 60 percent, and operating temperatures are about 1,000 degrees C (about 1,800 degrees F). Cells output is up to 100 kW.

CopperBytes

• Fuel cells will make it possible to economically generate electricity at remote locations, reducing dependence on large central power generating plants.
• Portable backup power supplies are being developed to take advantage of the fuel cell's high efficiency, quiet operation, and high reliability.
• At twice the efficiency of internal combustion engines, fuel cells are expected to penetrate the vehicular market in just a few short years. Trucks, trains, submersibles, and passenger vehicles are expected to be some of the first markets employing fuel cells in large quantities.
• Fuel cells are being developed to power small weapons systems. Fuel cell-powered tanks and personnel carriers could travel in complete silence, with almost no infrared signature.

References:

• What is a fuel cell?
• Fuel Cell Basics
• Fuel Cell Basics