Fuel Cells
Fuel Cells | Fuel Cell Construction | The Chemistry behind Fuel Cells | Different Kinds of Fuel Cells | Applications of Fuel Cells | Obstacles for Fuel Cells to Over Come
 
 

Fuel Cells

A new form of energy production has been in the works since the space race in the 1950'0s. It’s not quite a battery, but it isn’t quite a combustion engine either. Fuel cells seem to be the wave of the future for electricity production.

Recipe for Electricity: Fuel Cell Construction

Electricity is nothing more than flowing electrons. That means that power generation is nothing more than finding out how to free electrons. Fuel cells rely on hydrogen for its electrons. There are many different fuel cells for every kind of application. But every fuel cell has the same essentials. They all have an anode (negative electrode) comprised
of hydrogen gas, and a cathode (positive electrode) of oxygen. In the middle is an electrolyte that only allows protons to pass through it. In between both electrodes and the electrolyte are catalysts that facilitate the reactions.

Let There Be Hydrogen: The Chemistry behind Fuel Cells

The fuel cell works by injecting molecular hydrogen (H2) molecules into the anode. The hydrogen molecules react with the catalyst. The catalyst is usually a thin coat of powdered platinum on carbon paper. This breaks up the hydrogen into a proton and an electron. The proton goes across the electrolyte, (remember, it only accepts protons) while the electron is fed through the circuit and goes to work, whether it be powering your oven or providing horsepower to your new ustang.

Upon finishing their job, the electrons return to the cell through the cathode. There, the catalyst assists the oxygen molecules, the hydrogen protons and the hydrogen electrons in making water. The chemical reactions are the following:

Anode:
2H2 => 4H+ + 4e-

Cathode:
O2 + 4H+ + 4e- => 2H2O

The whole reaction ends up looking like this:
2H2 + O2 => 2H2O

This reaction only creates about 0.7 volts. Because of this, there are several cells built into a stack. This multiplies the voltage up to useable levels.

The Fuel Cell Family: Different Kinds of Fuel Cells

Fuel cells differ in two ways. The most important difference is the electrolyte. Different electrolytes provide different voltages and different properties. The fuel cell destined to appear under car hoods is called a Proton Exchange Membrane Fuel Cell. The stacks that will be used to fuel the car are about the size of an average sized printer.

Other fuel cells are much bigger (ranging in size from a large central air conditioning unit to a compact car.) These cells are stationary and can provide electricity to an apartment complex, an office building or 60 family homes. These include phosphoric-acid, solid oxide and molten carbonate fuel cells. All of these fuel cells are large and take a relatively long time to heat up (or “prime the hydrogen pumps”) which is why they are not suitable for automobiles. These large-scale fuel cells operate at high temperatures as well, (they range from about 1,000° F to 1,800° F) which allows engineers another way of producing energy. The heat from the fuel cells can be used to boil water (perhaps the water it produces) and turn steam turbines for even more electricity.

The Revolution: Applications of Fuel Cells

Fuel cells have the potential to slip into every kind of electronic device. A few applications could include:

  • Cars- as stated before, fuel cells the size of a printer could provide enough juice to power as well (if not better than) a combustion engine. Slightly larger units are already in place in several bus systems across the United States. The hydrogen for both forms of transportation may be provided through propane, methanol or natural gas.
  • Personal Devices (Laptops, cell phones, hearing aides) - fuel cells have the tremendous potential to get into every electronic device we come in contact with. Fuel cells offer the possibility of laptops and cell phones with energy life measured in days or weeks, rather than hours. The fuel cell is scalable, which means it can go small enough to power medical devices that normally require battery replacement.
  • Stationary Power Production and Backup- larger-scale fuel cells could allow every city to have its own power station, rather than a centralized power grid. Power generation could become so decentralized that each housing development or apartment complex could be self-sustained with its own power. This would drastically cut down on pollution and ugly power lines. Hospitals and airports could (some already do) have backup power supplies that kick in, in the event of a power failure.

The Achilles Heel: Obstacles for Fuel Cells to Over Come

It is important to remember that fuel cells are not batteries. While they share similar
properties such as the ability to change chemical energy into electrical energy, fuel cells
require hydrogen fuel to continue working. Oxygen is easy to find, for obvious reasons
(it’s floating in the air) but hydrogen (while it is the most abundant element in the
universe) must be cultivated from other molecules. Free hydrogen is volatile and hard to
store.

Hydrogen can be extracted from several different fuels:

  • The Classics: natural gas, gasoline, diesel gas and propane all contain massive amounts of hydrogen that can be used in a fuel cell.
  • Green Gas: renewable gasses and fuels also offer hydrogen, these fuels can be ethanol, methanol, landfill gas, bio-gas, and methane.
  • Water: water is two thirds hydrogen, and the most abundant molecule on Earth. Through electrolysis, the oxygen and hydrogen can be separated and put to use.
  • Exotic: there are very exotic forms of hydrogen fuel, these include peanut shells, algae, and sodium borohydride (highly corrosive, toxic, flammable, and highly water-reactive compound).

Currently, hydrogen costs are about $3.00 a gallon. But by 2010, the Department of Transportation promises to reduce the cost to under a dollar. The cost of the hydrogen is dependent mostly on the delivery system of the hydrogen. Hydrogen can be pumped through pipe lines (this is already employed in industrial settings). Hydrogen can also be drawn from the above fuels and carried on-board the cars just as gas is in combustion engines. The best alternative would be for fueling stations to be powered by solar, wind, or hydroelectric power and use that electricity to separate hydrogen from water using electrolysis. There are already two such stations working in southern California.