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> How Fuel Cells Work
> Types of Fuel Cells


 

 

A fuel cell is a device that generates power by converting hydrogen into electricity through a chemical reaction. In its simplest form, fuel cells are just like batteries, except they do not need to be recharged or replaced - they simply need a supply of fuel and air. Fuel cells also provide instant power and are a green energy source with very low to zero emissions.

When looking at a fuel cell, it is useful to break the system into four distinct parts: the fuel cell stack, BOP (balance of plant), EMS (energy management system) and the cartridge. All of these components operate together to determine the overall size, output and efficiency of a fuel cell. Different characteristics or parameters for each of these components can dramatically affect the overall performance and operation of the fuel cell system. In fact getting optimal performance from a system is often a delicate balance of  managing air flow and temperature (BOP), along with algorithms and sensors (EMS) that all affect the reaction that occurs inside the fuel cell stack.

The Fuel Cell Stack
The fuel cell stack is responsible for generating power. This reaction differs depending on the type of fuel used by the system. In the case of Antig, Antig stacks are designed to be used with methanol, which is part of the wood alcohol family. Inside the stack, there are a number of modules, each made up of a number of cells. Each cell is part of what is called a MEA (membrane electrode assembly). MEA's have a negative side (anode) and a positive side (cathode), and squeezed between the two is a membrane coated with a special catalyst. This catalyst separates each element from the methanol and water, breaking the hydrogen into positive and negative ions. Once separated, positively charged hydrogen ions (protons) pass through the fine meshed membrane from the anode side to the cathode side. The negatively charged hydrogen ions (electrons) are unable able to pass through this membrane and are routed around the membrane to the cathode side via an external circuit. As they travel through this external circuit, they generate electricity. Once on the cathode side the electrons are reunited with their partner protons to once again form hydrogen. At the same time air is passed through the cathode side which mixes with the hydrogen atoms to form water, which completes the fuel cell process.

 
An example of a typical direct methanol fuel cell reaction where methanol combines with water to produce heat, in the form of CO2, and hydrogen. After the reaction, hydrogen mixes with oxygen to form water.

Factors Affecting Fuel Cell Performance
Fuel cells are designed to operate in specific types of conditions. For example, oxygen is a key element required to complete the reaction, as it removes spent hydrogen from the system as water. If no oxygen is present, or not in enough quantity, the reaction will either slow down or stop completely. Also, in direct direct methanol fuel cells (DMFC), water management is important as it helps move hydrogen protons from the anode side across the membrane to the cathode side. If too much water moves across, then the cathode side can be easily "flooded'. Not enough water, then the membrane cannot transfer enough protons to facilitate the reaction. Finally, the fuel used also has an impact, both on the power of the system as well as it's operating conditions. In the case of solid oxide fuel cells, the reaction needs to occur within 600C ~ 1000C, while methanol systems operate best between 40 ~ 80C. This balance between air, water and heat management is both an art and science that ultimately determines the overall performance of a fuel cell system.

Click here to learn more about specific types of fuel cells and their operating conditions.