Hydrogen is the most common element in the universe but on earth it does not exist as a gas. To be useful for energy,  the hydrogen must be produced from hydrogen compounds, including fossil fuels or water. In order to extract hydrogen from these compounds, you have to exert energy.

Honda introduced an interesting fuel cell car   with a way to generate Hydrogen from water. (Photo is the Honda FCX Clarity with Solar Station)

The concept is to generate enough Hydrogen overnight (about a pound) to allow a typical commute -  30 to 35 miles.

A Solar Hydrogen Station is employed with a 48-panel, 6.0kW solar array utilizing thin film solar cells composed of copper, indium, gallium and selenium (CIGS.)  Compatible with a "Smart Grid" energy system, during daytime peak power times, it can export renewable electricity to the grid, thereby remaining energy neutral for the electricity used at night to generate hydrogen.  The Fuel Cell Car is also equipped with a cylinder "fast fill" storage system that can allow the car to go 280 miles.  The concept is during the week, you would fill-up at home and for a weekend drive purchase hydrogen from a "fast fill" facility.

A Polymer Exchange Membrane Fuel Cell (PEMFC) is one of the simplest and efficient types.  A fuel cell is an electrochemical energy conversion device.  It converts the chemicals hydrogen and oxygen into water, and in the process it produces electricity. The PEMFC has a high power density and a relatively low operating temperature ranging from140 to 175 degrees Fahrenheit so that it doesn't take very long  to warm up and begin generating electricity.

How a PEMFC Fuel Cell Works

The PEMFC has four basic elements:

The Anodecconducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit.

The Cathode has channels etched into it that distribute the oxygen to the surface of the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with the hydrogen ions and oxygen to form water.

The Electrolyte is the Proton Exchange Membrane which looks like  kitchen plastic wrap, and only conducts positively charged ions.

The Catalyst facilitates the reaction of oxygen and hydrogen. It is usually made of platinum nanoparticles very thinly coated onto carbon paper or cloth

THE PROCESS:
Pressurized hydrogen gas (H₂) entering the fuel cell on the anode side. This gas i­s forced through the catalyst by the pressure. When an H₂ molecule comes in contact with the platinum on the catalyst, it splits into two H⁺ ions and two electrons (e^-). The electrons are conducted through the anode, where they make their way through the external circuit, such as a motor, and return to the cathode side of the fuel cell.

On the cathode side of the fuel cell, oxygen gas (O₂) is being forced through the catalyst, where it forms two oxygen atoms. Each of these atoms has a strong negative charge. This negative charge attracts the two H⁺ ions through the membrane, where they combine with an oxygen atom and two of the electrons from the external circuit to form a water molecule (H₂O)

Fuel Cell Efficiency

Fuel cells are about 80% energy efficient.  Powering an electric motor with the appropriate gearing etc that can be about 80% efficient for an overall 64% total energy efficiency.

That compares to an internal combustion engine which is about 17 to 20% efficient. 

A battery powered car is about 72% efficient with a 90% efficient battery (about 10% heat is generated) and an 80% motor/gearing efficiency.

Interesting Information Related to Welding Gas

Hydrogen has an atomic weight of 2.02 compared to Argon with an atomic weight of 39.9.  This is a consequence: 

A typical cylinder of Argon contains 336 cubic feet of gas measured at atmospheric pressure when pressurized to2640 psi.  The cylinder weights 177 lbs full and 143 lbs empty or there is a 34  lbs or Argon contained in the cylinder.

The same size cylinder with Hydrogen also weights 143 lbs empty.   To hold the same 336 CF of gas (measured at atmospheric pressure) it needs to be pressurized to a similar 2400 psi.  However because of its low molecular weight it only weights 145 pounds full or the gas only weights only about 2 lbs!

The ratio of molecular weights defines the weight it contains compared to Argon, i.e.

34 lbs Argon X (39.9/2.02) = 1.72 lbs of Hydrogen. 

Of note, Nissan has developed a composite aluminum carbon fiber container that can be pressurized to 10,000 psi which would hold 4 times the amount of gas in a given volume.

Some of Our Other "Green" Web Pages You Might Like to Visit: