What is a Fuel Cell?

First invented in 1839 by William Grove, a fuel cell is an electrochemical energy conversion device that produces electricity by combining hydrogen and oxygen into water. Like batteries, fuel cells convert potential chemical energy into electrical energy and generate heat as a by-product. However, the chemical energy is stored inside batteries—rather than generated— they can only operate for a limited duration until they need to be discarded or recharged. Fuel cells, on the other hand, can continuously generate electricity as long as they are supplied with fuel (hydrogen) and an oxidant.

Fuel cells can be used anywhere you need power. In 2016, more than 65,000 fuel cells, totaling over 300 MW, were shipped worldwide. Continued growth in fuel cell usage has been encouraged by governmental green energy programs and tax credits in China, Europe, Japan and the USA.

Leading companies such as Apple, Verizon and Coca-Cola are generating power with stationary, hydrogen fuel cells. Hydrogen fuel cell vehicles from Toyota, Honda and other companies are coming to market and metropolitan areas are beginning to migrate to clean hydrogen-fuel buses. Hydrogen refilling stations in California and other states are overcoming the challenges of hydrogen distribution for consumers. Indeed, the US Department of Energy notes that hydrogen and fuel cells are on the verge of a “tipping point” much like solar energy was a number of years ago.

TYPES OF FUEL CELLS

Fuel cells are characterized by the type of electrolytes used to separate the fuel cell electrodes. Since different materials are electrolytic at different temperature levels, fuel cells are classified as low temperature, medium temperature and high temperature.

There are five primary types of fuel cells:

• Alkaline Fuel Cells (low temperature)
• Proton Exchange Membrane Fuel Cells (low temperature)
• Phosphoric Acid Fuel Cells (medium temperature)
• Molten Carbonate Fuel Cells (high temperature)
• Solid Oxide Fuel Cells (high temperature)

Each type of fuel cell has its own inherent strengths and weaknesses that make them more suitable for specific markets and applications.

For more information about fuel cells, download our white paper, “The Big Deal With Fuel Cells.”

ALKALINEFUEL CELLS

Alkaline fuel cells (AFCs) are among the most efficient type of fuel cells, reaching up to 60% efficiency (up to 87% combined heat and power). They were developed in 1959 by Francis Thomas Bacon. Using an alkaline electrolyte such as potassium hydroxide (KOH) in water and cathodes usually made with platinum, AFC Alkaline fuel cells also offer virtually instant operation without pre-heating, even at sub-zero temperatures. AFC were used by the NASA and MIR space programs to produce electricity and drinking water.

The alkaline fuel cell is comprised of a pair of porous electrodes—a positively charged cathode and a negatively charged anode—separated by an alkaline electrolyte or membrane electrolyte. Air, containing oxygen, is fed to the cathode gas chamber where it reacts with water to produce four OH- ions and four positive charges.

 

The OH- ions, attracted by the anode, pass from the cathode through the KOH electrolyte. Hydrogen, fed to the anode, reacts with OH- ions to form molecules of water and negative charges.

The electrons are attracted by the positive charge on the cathode and are forced through an external circuit as an electric current. The reaction produces useable heat and water as a byproduct.