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What are fuel cells ? and how do they work?

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A fuel cell is an electrochemical device that converts the chemical energy of a fuel such as hydrogen or methanol into electrical energy through a pair of oxidation-reduction reactions, in other words, it is a device that produces electricity from mixing fuel with oxygen. The most environmentally friendly fuel cells use hydrogen as a fuel and oxygen as an oxidant producing electricity and water. This device act as an electrochemical battery, however, it never gets drained as long as the fuel and oxidant are introduced.

The water molecule is composed of an oxygen atom and two hydrogen atoms, separating them requires energy, this separation process is referred to as electrolysis or electrochemical water splitting. The mixing of water and hydrogen occurs in the fuel cells and releases energy in the form of heat and electricity.

Fuel cells are composed of two metal plates called electrodes: An anode and cathode separated by an electrolyte that is an ionic conductor but blocks the flow of electrons forcing them to move through an external circuit and thus producing electricity.

Hydrogen or a hydrogen-rich fuel, such as methane is introduced at the anode level, whereas the air (containing oxygen) that acts as an oxidant is injected at the cathode.

One of the most important advantages of fuel cells is their high efficiency which exceeds 60% for high-temperature fuel cells, and the possibility to be used as a CHP (Combined heat and power) generating electricity and heat. Hydrogen fuel cells have no harmful emissions, as the only product of the reaction is H2O molecules (water). Fuel cells play a major role in the hydrogen industry and can be for domestic, industrial, and mobility (cars and urban transport), the low environmental, visual, and noise impact of these devices makes them an attractive alternative.

The production of hydrogen can either be from fossil fuels through steam reforming this process releases carbon dioxide, or it can be extracted from water, through decomposition of the water molecule using electricity from excess wind or solar energy, in this case, the hydrogen is referred to as ‘green hydrogen ‘because no harmful emissions are released.

Micro fuel cells can now be used for domestic applications. For instance, the German company Home Power Solutions worked on a system composed of a PEM fuel cell, an electrolyzer, and a photovoltaic system. Excess solar power during sunny days/summer is used for the electrolysis of water, then the hydrogen is stored to be used during winters/ nights in a fuel cell to provide both electricity and heat. This system can be easily integrated with existing solar panels which makes it a very attractive solution to reduce the dependency on the grid and ensure continuity of electrical and thermal energy production.

References

Cigolotti, V., Steinberger-Wilckens, R., McPhail, S. J., & Devianto, H. (2012). High-temperature fuel cell plants and applications. Fuel Cells in the Waste-to-Energy Chain, 145–162. https://doi.org/10.1007/978-1-4471-2369-9_9

Cassir, M., Jones, D., Ringuedé, A., & Lair, V. (2013). Electrochemical devices for energy: Fuel cells and electrolytic cells. Handbook of Membrane Reactors, 553–606. https://doi.org/10.1533/9780857097347.3.553

Temperature Fuel Cell. Temperature Fuel Cell – an overview | ScienceDirect Topics. (n.d.). Retrieved May 12, 2022, from https://www.sciencedirect.com/topics/engineering/temperature-fuel-cell

Hub: Fuel processing for low-temperature and high-temperature fuel cells: Challenges, and opportunities for sustainable development in the 21st Century: 10.1016/S0920-5861(02)00231-6. Sci. (n.d.). Retrieved May 12, 2022, from https://sci-hub.hkvisa.net/10.1016/s0920-5861(02)00231-6

The fuel cell-powered home: An approaching reality? FuelCellsWorks. (2019, February 20). Retrieved May 12, 2022, from https://fuelcellsworks.com/news/the-fuel-cell-powered-home-an-approaching-reality/

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