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How do hydrogen fuel cells work?

Although fuel cell technology is a relatively new way to produce energy, it is frequently improving. Fuel cells have been used by NASA to power the space shuttle and the technology is being harnessed more in vehicles as well as household appliances such as boilers. But what is fuel cell technology and how does it work?

What is a fuel cell?

Put simply, a fuel cell converts hydrogen into electricity via a chemical reaction.

Every fuel cell has two electrodes: anode and cathode. The cathode is negatively charged and the anode is positively charged. An example of an anode and a cathode working together is in a battery. A battery has a positive side and a negative side, and when you slot the battery into place, it connects the electrical circuit and allows the current to flow around the device. However, in order for the current to flow in the right direction, an electrolyte is required to carry the electrically charged particles from one electrode to the other, and a catalyst is required to speed this process up.

Electrolytes, anodes, cathodes and catalysts are all needed to allow the chemical reaction to take place to produce the required electricity. Fuel cells can’t ‘run out’ because they constantly receive the chemicals they need to convert fuel to electricity, unlike a battery where the chemicals are contained on the inside and are used up until there’s no more left.

How does a fuel cell work?

Now you know what a fuel cell is made up of, but how does it convert fuel to electricity?

Hydrogen fuel is supplied to the anode and oxygen is supplied to the cathode on the other side of the fuel cell. At the cathode, the electrons and positively charged hydrogen ions combine with oxygen to form water, which flows out of the cell. This is the only byproduct of fuel cell reactions. At the anode, a catalyst causes the hydrogen to split into positive hydrogen ions and negatively charged electrons. A polymer electrolyte membrane (PEM) only allows positively charged ions to pass through it to the cathode. The negatively charged electrons must travel along a circuit to get to the cathode, which creates an electrical current. 

Both hydrogen and oxygen are required for a fuel cell to create electricity. Together, they combine to create water, which is drained from the cell.

One fuel cell wouldn’t be enough to power anything like a boiler or a vehicle. Instead, individual fuel cells are assembled together to form what’s known as a stack. A fuel cell stack can be as big or small as needed to create the right amount of electricity. 

Why are fuel cells important?

There are lots of benefits associated with using fuel cells to produce electricity. We’ve listed just a few of the most important ones.

Most fuel cells produce almost no noise when they’re running, which makes an attractive choice for use in commercial or public spaces, such as a hospital or an office.

They have a much higher efficiency than diesel or petrol engines, and could save you up to 40 per cent on your heating bill. Most fuel cell boilers have an energy efficiency rating of at least A++. According to the Canadian Hydrogen and Fuel Cell Association, fuel cells are two to three times more efficient than combustion engines.

When combustion is taking place, the laws of thermodynamics need to be applied, particularly in a large power plant. With fuel cell technology, these laws don’t apply in the same way, so there’s no limit to the technology’s use in a large plant.

Fuel cell technology could be used to power all the vehicles in the world, replacing traditional petrol and diesel engines. The only byproducts of creating electricity in this way are heat and water, neither of which are as harmful to the environment as the chemicals produced by petrol and diesel engines. The byproducts of fuel engines include nitrogen oxide, carbon monoxide, sulphur dioxide and volatile organic compounds (VOCs), all of which pollute the air and can cause lung and throat problems.

Fuel cell technology could stop the creation of such pollution and is a renewable energy source that doesn’t rely on potentially harmful fuels that produce high volumes of CO2. The fuel cells will continue to produce electricity as long as there is a continuous supply of oxygen and hydrogen. This could mean, in the future, that we fill our cars up with hydrogen gas instead of fuel, which may cut emissions by around 30 per cent. 

What are fuel cells used for?

NASA is currently the primary user of hydrogen technology for its space programme. The agency has used liquid hydrogen to fuel the space shuttle since the 1970s, and now they use giant hydrogen batteries for electrical resources. The water that is produced as a byproduct of the fuel cell technology can be drunk by the crew.

Fuel cell technology is being used in boilers too. Combined heat and power boilers feature fuel cells that generate electricity that can be used on site while at the same time creating heat that can be harnessed to provide hot water and central heating. Any excess electricity can also be exported to the National Grid. Suitable for use in a variety of homes and commercial buildings, these highly advanced boilers can cut users’ energy bills and carbon footprints.

Fuel cells don’t run out like a battery, which means they have the potential to power devices such as mobile phones, tablet devices and laptop computers. This could mean that, as the technology evolves in the future, we may never have to charge our mobile phones. This also makes fuel cells a good backup power source for buildings such as offices or hospitals in case the mains power goes off.

According to Renewable Energy World, hydrogen could join electricity as an important energy carrier. An energy carrier is a kind of fuel that can be stored for later use. Wind and the sun can create electricity using light and movement, however they can’t produce energy all the time. Instead, the energy can be stored until it’s needed. Hydrogen can also be stored in this way and could be transported to other locations when it’s needed. 

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