Fuel Cell Technology

Summary of the Lecture

H2-O2 reaction - Most of the time Hydrogen and Oxygen react together and forms water molecule spontaneously.

Internal electron transfer - During this reaction internal electron transfer (electricity) takes from Hydrogen atoms to Oxygen atoms. But since this transfer is internal, it is of no use.

Physics of Fuel cell - Fuel cells force electrons to move through an external path, by introduction of a barrier in between. A barrier which will transfer only Hydrogen ions, but not electrons.

So electrons flow through the external circuit and produces electricity in a fuel cell, In the meantime Hydrogen ions which are capable to sneak through the barrier moves and combine with Oxygen ions. Here same chemical reaction happens but in a different fashion.

Membrane Electrolyte - Most common barrier used for H2-O2 fuel cell is Membrane electrolyte.

Anode & Cathode - Every fuel cell requires one anode and one cathode, which are acting as catalysts. Function of anode is to aid dissociation of H atom into H ion. Cathode helps in combining Oxygen and Hydrogen ions together in order to form water molecule.

GDL - Such a fuel cell will require Gas Diffusion Layer (GDL) at both sides, main function of which is to allow passage of gas at both the sides, provide a compartment for product water removal and conduct electricity and heat out of the system.

Stacking different Fuel cells - Bipolar plates help in stack different fuel cells together, thus augments voltage of fuel cell. It also helps in distributing gases on both sides of the plate.

Compression plates - GDL works well under high pressure, so 2 compression plates are used increase pressure of the system.

Electricity collectors are used to transfer electricity produced inside the system to external circuit.

Electro Chemical Mechanism – H2 and O2 which are supplied at both ends of bipolar plates pass through GDL and reach anode and cathode respectively. At anode H atoms become H⁺ ions and electrons. Electrons which are not able to pass through membrane electrolyte flow through the external circuit and produces electricity. It then combines with O atom and produce O^2- ion. H⁺ ions which can penetrate through the membrane, travels through it combine with O^2- ion at the anode side and produces water. Due to high temperature of Fuel cell this water produced will be in vapor state and can be carried away by a blowing air supply

• PEM Fuel cells - This kind of fuel cells is known as Proton Electrolyte Membrane fuel cells. PEM fuel cells are considered to be the most versatile one for industrial use.

Advantages of Fuel Cells

Some advantages of fuel cell are listed below

• Green Energy - H2 powered fuel cells are green source of energy, since they do not emit CO2 as in conventional internal combustion engines.
• Quite operation - Since there are no rotating parts in fuel cell it is always quite in operation.
• High power density - Fuel cells produce high amount of power for same weight of equipment compared to other conventional source of energy. This makes fuel cells preferred method in space applications.
• High Conversion Efficiency - Since Fuel cells convert chemical energy directly into electricity their efficiency is not constrained by 2nd law of thermodynamics. In effect fuel cells have got good conversion efficiency, they can convert 60-70% chemical energy into electrical energy.

What is Impeding Fuel Cell Technology?

So many advantages for Fuel cells, but still this technology hasn't made way through industrial and technical applications as it should have. So what is impeding this technology from getting into your life?
Main reason which impede fuel cells technology is its high cost.High cost incurred mainly due to cost of membrane electrolyte and other accessories. But recent developments to cut cost of Fuel cell are positive.It is expected that in 20 years Fuel cell technology will be able compete other power generation technologies commercially.