What are fuel cells?

A Fuel Cell unit is an appliance which produces not only electricity for a home, but also provides a certain level of heating and hot water too. Furthermore, like solar panels and heat pumps, they do this in a much more environmentally friendly way than burning fossil fuels.

Burning fossil fuels, such as natural gas and oil, to heat our homes releases carbon into the atmosphere – a major contributor to climate change. Rather than burning fuel, a fuel cell converts hydrogen into electricity through a chemical process and three products are created:

• Electricity
• Heat
• Water

Using hydrogen leaves no carbon footprint.

What’s more hydrogen fuel cells maintain a high level of efficiency. 1kg of hydrogen contains roughly the same amount of energy as 2.8kg of gasoline, almost 3 times as much energy.

What is hydrogen?

Of all the chemical elements, hydrogen is the most plentiful in the universe. It is the first element in the periodic table and has the atomic number 1.

It is the main ingredient of stars, including over 90 per cent of our Sun, and a thin mist of it is scattered through space. About 60 per cent of the atoms in our bodies are hydrogen and it is one of the two key ingredients in water.

Hydrogen is the lightest gas and when used as a fuel, it is either highly compressed or condensed.

It is no more dangerous than conventional fossil fuels – quite the reverse. Compared to gas and oil, hydrogen stands out on account of its very positive properties. Moreover, hydrogen is not carcinogenic and can be used without leaving any residues.

Hydrogen is odourless, colourless, very energetic and makes an excellent fuel. You can heat your home or cook a meal by using hydrogen, the same way many homes use natural gas.

Pure hydrogen as an energy source is:

- not explosive
- not self-igniting
- not subject to decay (such as acetylene)
- not oxidising
- not poisonous (no air pollutants)
- not corrosive
- not radioactive
- not carcinogenic

Hydrogen leaves no carbon emissions and is now set to play a crucial role helping us to tackle the climate crisis and wean the world off greenhouse gas emissions. In a net-zero CO2 world, studies estimate that hydrogen could account for up to a quarter of our overall energy needs.

How do fuel cells work?

Hydrogen fuel cells are made up primarily of 4 main parts:

- Anode
- Cathode
- Electrolyte membrane
- Catalysts

Here comes the tech stuff!

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 by-product 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.

Unlike batteries, which need to be recharged, fuel cells never run out – they will continue to work as long as it's being provided with fuel.

The Viessmann Vitovalor

The award-winning Vitovalor PT2 from Viessmann is a fuel cell heating appliance that uses the principle of cogeneration to generate both power and heat. To do so, the fuel cell requires not only oxygen but also hydrogen, which is obtained from natural gas in an earlier process.

The PT2 consists of two units: a fuel cell module and a gas condensing module for covering peak loads. The two units can be transported separately, enabling fast installation even in basement rooms where space is tight.

The first unit of the Vitovalor, made by Panasonic, houses the reformer, inverter and fuel cell stack (a series of multiple fuel cells). Before the direct current generated by the fuel cell is fed into the household power circuit, the built-in inverter converts it into alternating current.

The second unit of the Vitovalor serves primarily to provide heat during times of peak demand. That is, when it is very cold outside or when a lot of hot water is required at short notice. It consists of a gas fuel cell appliance, a DHW cylinder, a heat exchanger and a heating water buffer cylinder with integral indirect coil for DHW heating.

Other components in the second unit are a weather-compensated control unit, hydraulic components and an electricity meter. Both units are supplied via a common gas line. They also share a common flue system, which makes installation as easy as for a wall mounted gas condensing boiler.

Are hydrogen and fuel cells here to stay?

The gas industry has been systematically replacing the metal pipes in its network with yellow polyethylene ones. Around 90% of the pipes will have been replaced by 2030. This is good news for hydrogen because the gas reacts with the old metal pipes, making them brittle. However the polyethylene pipes would be safe.

Most boilers these days are being manufactured as “hydrogen-ready” and it is looking highly possible that one day our properties will be fed with hydrogen instead of mains gas.