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How do fuel cells work?

Posted by Sharon Russell-Verma on 18 July 2016 at 11:05 am

In some circles micro-fuel cells are being heralded as the future of clean energy, so today we are going to look at how fuel cells work. But let’s start at the beginning – what is a fuel cell?

What is a fuel cell?

A fuel cell is a device that generates electricity by a chemical reaction. In contrast to a steam-powered generator system, the fuel cell does not first convert chemical energy into mechanical energy. Fuel cells, like electric cells (batteries), have no moving parts. However, unlike batteries, they use outside materials (gases) to produce an electric current. Moreover, they generate electrical power quietly and efficiently, without pollution.

History of fuel cells

The first fuel cells were invented in 1839 by William Grove, but it wasn’t until the 1950s when English scientist Francis Bacon produced the fuel cell stack, that their potential became apparent. This is because fuel cells are modular and a single fuel cell produces a very small amount of electricity, so by stacking them one on top of another and linking them together they could produce more electricity. In fact, the US space program was made more possible thanks to the use of fuel cells to generate power for probes, satellites and space capsules. Since then, fuel cells have been used in many other applications such as powering hospitals, hotels, office buildings as well as in cars, buses and motorcycles. Yet despite this, they are still seen as ‘innovative’ today, perhaps due to the fact that the technology remains widely unknown.

How do they work?

There are many different types of fuel cells, but they all consist of two electrodes; one positive (the anode) and one negative (the cathode). The reactions that produce electricity take place at the electrodes. Fuel cells also have an electrolyte (a solution that conducts an electric current) which carries electrically charged particles from one electrode to the other, and a catalyst which speeds the reactions at the electrodes. The fuel used to drive the reaction is hydrogen but oxygen is also required. If pure hydrogen is used, fuel cells only produce water, thus eliminating all emissions such as carbon dioxide and other greenhouse gases otherwise caused by electricity production. One drawback of fuel cells is that they do not store energy; they produce power only as long as hydrogen ions and oxygen are supplied.

Source: Caltech.edu/research
 

Types of fuel cells

There are five major types of fuel cells to choose from depending on what the energy is needed for. The main difference among fuel cell types is the electrolyte; fuel cells are classified by the type of electrolyte they use and include:

  1. alkali
  2. molten carbonate
  3. phosphoric acid
  4. proton exchange membrane (PEM) and
  5. solid oxide 


Phosphoric acid cells are the ones most commonly used in Combined Heat and Power (CHP) systems, but molten carbonate and solid oxide fuel cells can also be used for combined heat and power generation. Disadvantages of the systems include slow ramping up and down rates, high initial cost and short lifetime. Furthermore their need to have a hot water storage tank is a disadvantage in the domestic market place where space may be in short supply. Nevertheless, recent research has shown that the fuel cell market is growing, and it is estimated that the (non-vehicle) fuel cell market will reach 50 GW by 2020.

Fuel cell in UK homes

The good news is that fuel cell systems are already being used in the UK. The first energy efficient fuel cell system has been installed in a family home in Surrey. The BlueGen gas-to-electricity generator is supplied by Ceramic Fuel Cells Limited and is the UK’s first ever installation of a microgeneration certificate scheme (MCS) accredited micro power and heat fuel cell in a new build home, providing power, heating and hot water. The micro-CHP provides all the heat needed for the home - there is no separate boiler or other heating device. At the moment the BlueGen micro-CHP is the only fuel cell product eligible for the UK Feed-In Tariff (FiT) and the manufacturers claim that the unit can save up to four tonnes of carbon per year.

Future of fuel cells

Fuel cells could help to us to reduce our overdependence on less efficient fossil fuels and at the same time help greatly reduce emissions into the atmosphere. So what’s the catch...? Well at the moment, for most applications they are still too expensive to compete with conventional methods of producing electricity or heat, however with the huge interest in fuel cells, their future looks bright.

More information about Combined Heat and Power (CHP) on YouGen.

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