Fuel cell

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The fuel cell is an electrochemical device that converts the chemical energy contained from hydrogen into electrical energy and water. Today, unfortunately fossil fuels have impurities, many of them composed of sulfur, and the high temperatures reached in the combustion process involve a reaction of nitrogen present in the air.

In addition, the amount of oxygen present is not always sufficient for the total burning of the fuel, generating carbon macroparticles. All these factors are responsible for considerable pollution.

Another problem is the efficiency of chemical energy use contained in fuel. Most of the energy released in direct combustion, such as that occurring in the burning of fuel in car engines and thermal power plants, is in the form of heat.

In conclusion, the biggest problems of energy production by combustion are:

• fossil fuel is not renewable;
• the use of energy is small (low efficiency);
• severe environmental pollution, creating serious problems for health and material assets.

The fuel cell is an equipment that performs an electrochemical reaction between oxygen and hydrogen that does not represent combustion. Normally these systems have high efficiency, are silent and can be assembled in a modular way, since they have no moving parts.

Fuel cells stimulate the procurement of a local solution as the hydrogen source becomes particularly flexible. There are six types of fuel cells that differ basically in the constituent elements, in the operating temperature and in the purity of the gas used.

Operating principle

The fuel cell is a type of battery in which the continuous supply of energy occurs provided it is continuously fed with the gases. The overall process reaction in the fuel cell using hydrogen is: 2H2(g) + O2(g) => 2H2O + energy.

When hydrogen comes into contact with a catalyst (platinum or platinum-ruthenium alloy, platinum-iridium or other materials), it gives off electrons to the metal or alloy producing H+. These protons are carried by the electrolyte, which in the PEM cell case is a polymeric membrane (Nafion®). This membrane, besides carrying the protons, is an electrical insulator.

The electrons, in turn, are conducted by an external circuit generating a flow of electrons and thus electric current and power. In the case of oxygen, which can be obtained from the atmosphere itself, water vapor is produced with the arrival of hydrogen protons through the membrane and the circulation of electrons.

Features and applications:

• has high electrical conversion efficiency, reaching 50%;
• has high conversion efficiency with cogeneration up to 80% (heat can be used to heat water);
• generation on site, without chemical pollution, as it only produces water, and without noise pollution;
• estimated useful life of up to 40,000 hours;
• the cost is still high because it is a new technology and is not produced on a large scale.

Fuel cell applications:

• space vehicles;
• backup power;
• vehicle power generation: electric and hybrid vehicles;
• stationary generation in industries and homes;
• portable generation as power for mobile phones and laptops.

Scenarios

Despite large investments in research and all the effort, especially from industrialized countries (such as the United States), the scientific and technological impasses have not yet been overcome. It is expected that in 50 years there will be advances towards making fuel cell technology products commercial and available.

Today the cost of a PEM type fuel cell generation unit for use as power backup is approximately 5 thousand euros per kilowatt. This value for certain market niches can already be considered competitive. However, it is still far from a wide application of this type of equipment.