Hydrogen fuel cells are efficient, zero emission devices that quietly and reliably generate electricity.
A fuel cell is a device that generates electricity through an electrochemical reaction, not combustion. In a fuel cell hydrogen and oxygen are combined to produce electricity, heat and water. Hydrogen fuel cells are very clean and versatile, producing zero emissions while being an extremely efficient, reliable and quiet source of power.
PEM (proton exchange membrane) fuel cells are a type of hydrogen fuel cell being widely commercialised across multiple applications and business sectors. They convert the chemical energy of hydrogen fuel directly into electricity via a solid conducting membrane sandwiched between two electrodes. Below is a simplified illustration of a working PEM fuel cell.
The hydrogen molecule donates its electron at the anode, leaving positively charged protons. Electrons travel through the circuit and protons through the membrane to the cathode, where they form water. The flow of electrons or electricity is the primary product of the fuel cell with pure water the only byproduct.
Each cell typically produces 0.6 t0 0.7V and by connecting a number of cells in series, fuel cell stacks of a desired voltage can be produced.
Each cell in a fuel cell is sandwiched between two metallic bipolar plates. Bipolar plates have channels designed into their structure for transporting hydrogen and oxygen (from the air) to the electrodes, transporting product water away to the exhaust and as part of the cooling system. The plates also act as electrical conductors and to give mechanical strength.
A fuel cell stack is a number of fuel cells stacked together like a sandwich using bipolar plates (an anode and cathode combined in one).
One advantage of fuel cell technology is that it is both scalable and modular. To achieve desired power output, you only need to stack cells together.
A fuel cell power system or module is the complete set of components that integrate with the fuel cell stack so that electricity is produced. The fuel cell requires other systems to make it a complete power source, including air, fuel and control systems.
PEM fuel cells display the highest power densities of any of the fuel cell types, which makes them particularly attractive for transportation and portable applications where minimum size and weight are required. They contain no corrosive liquid electrolyte and are robust in construction and are modular and scalable in design. They are low temperature fuel cells, which usually operate below 100 degrees oC, and can thus be fabricated from less costly, less exotic materials.
Because of these factors PEM fuel cells have the advantage of potential application across a very wide range; from portable power at a few watts to hundreds of kilowatts for vehicular and stationary power.
Both fuel cells and batteries produce electricity. Batteries however make electricity from energy they have stored inside, whereas fuel cells make electricity from fuel in an external fuel tank. So that while a battery may run dead, a fuel cell will make electricity as long as fuel is supplied. For hydrogen fuel cells, hydrogen is the fuel which is stored in a tank connected to the fuel cell. When hydrogen in the tank runs low, you refill it, or replace it with a full tank. The refilling of a hydrogen tank typically takes just a few minutes, much faster than the several hours it can take to recharge batteries.
