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Fuel Cell – clean energy – hydrogen

Célula a Combustível - Fuel Cell - Pila de Combustible
Fuel cell - electric power from hydrogen

Fuel Cell – Electric Power from Hydrogen

Fuel cell is an electrochemical transducer, continuous operation, which converts chemical energy into electrical energy by combining an oxygen atom with two hydrogen atoms, producing water, electricity and thermal energy. It operates under high energy efficiency, because it directly converts chemical energy into electrical energy without losses from the conversion of the chemical energy of fossil fuels, for example, thermal energy for subsequent conversion into electrical power (without the thermodynamic constraints of the Carnot cycle).

Its operation produces low environmental impact: no vibration, no noise, no combustion, no particulate emissions and, depending on the technology, without greenhouse gas emissions. In addition, in the current stage of development, without emission of acid gases and low pollution.

It is of continuous operation, because unlike chemical batteries, generates electricity as long as fuel supply and oxidant and never ‘lose power,’ as with batteries and common batteries.

When combined in sets are cells called Fuel, this association is justified to produce currents and electrical charges consistent with current energy needs.

Hydrogen as fuel

The conversion system of the electricity used by the fuel cell operates in reverse electrolysis, combining hydrogen atoms to oxygen atoms forming water in the process. This feature allows use of a wide range of composite chemical species, predominantly of hydrogen, such as hydrogen gas, passing by hydrocarbons of mineral origin, gasoline, for example, to hydrocarbon vegetable origin, such as ethanol, our known alcohol anhydrous.

Many active substances are shown to act as fuel for the fuel cell, among them stand hydrogen, methanol, hydrazine, ethanol, low molecular weight hydrocarbons, among others.

Hydrogen

Hydrogen atom
(Unscaled)

It is the most abundant chemical element in the universe, the lower density, and its most common isotope, has a proton and an electron and there is no neutron. This feature makes it unique. It is stabilized in two ways: 1) by sharing an electron, through molecular bond, with another family member or group of non-metal, or 2) accommodating an electron through ionic bonding with a member of the family or group metals . The connection with the first embodiment is oxygen.

Pure hydrogen is the ideal fuel for fuel cells, but its use is not favorable due to the cost of obtaining and mainly due to difficulties in storing, transporting and handling this substance. Even in liquid form or combined in the form of metal hydride there is a justified concern that imposes stringent safety requirements. Alternatively studies, for example, reforming of methanol or ethanol. In this technology, the hydrogen is separated from the alcohol to be used when the cell molecule. This technology has some advantages compared to the use of pure hydrogen. In addition to its lower cost, it is the most compatible with the current infrastructure installed fuel distribution. This PEMFC’s class is called DEFC (English, Direct Ethanol Fuel Cells), which despite being considered a promising technology for vehicle and portable applications, still presents a major technological challenge to achieve the levels of electrical current and power hit by cells that consume pure hydrogen.

There is great interest in developing fuel cell using pure hydrogen as a fuel:

  • avoids contamination of electrodes in adverse reactions
  • It reduces the number of system components
    • in charge of the reform of hydrocarbons
  • increases the system performance
    • because of the higher density of hydrogen,
      among others.

Hydrogen is provided on the anode side. This chemical species is not found in the environment without being combined with another element. Therefore, it is necessary to separate and sometimes store and transport for use as fuel (of course, these steps consume energy and a greater or lesser degree, causing environmental impact). There are several consolidated (and developing) procedures for this purpose. Electrolysis of water, hydrocarbons or alcohols reform, biomass gasification, among others, are examples of processes to obtain this input.

Oxidants

By definition ‘Oxidant’ is the chemical species that gives electrons in a chemical reaction.

Oxygen

Oxygen atom
(Unscaled)

Found abundantly in the atmosphere in concentrations exceeding 20%, in the form of gas, there is great interest in using this state as there are no problems of acquisition, transportation, storage, maintenance.

Oxygen. Possibly the most abundant chemical species of the earth, it is found in high concentration in the atmosphere. It is provided on the cathode side and generally in a gaseous state at ambient pressure and the homogenous mixture that is found in the air. However, for increasing yield, it can be supplied under pressure or dissolved in water, for example.

Result

Engineering operation of a Fuel Cell


Example operation of a PEMFC

Eduardo Stefanelli

Engenheiro por profissão, professor por vocação