Hydrogen – A very flexible energy carrier
Hydrogen is the most common and the lightest element of all. Hydrogen gas consists of two hydrogen atoms and has the chemical symbol H2. The name Hydrogen is Greek for “water-former” since water is created when hydrogen is burned. At standard temperature and pressure, hydrogen is a colorless and odorless gas. Common ways to store hydrogen is either compressed at 200 – 700 bar or as a liquid which it becomes at –253ºC.
As electricity, hydrogen is an energy carrier. It’s not a primary energy source but can be used to store, transport and provide energy. Its energy density is high per unit mass. One of the advantages of hydrogen is that it can store energy from all sources, both renewable, fossil and nuclear power. Hydrogen as an energy carrier is a very flexible alternative. Therefore hydrogen will play a key role in the necessary transition from fossil fuels to a sustainable energy system.
Many sources, many possibilities
Hydrogen is a commonly used element and reactant in a wide range of industrial procedures. The most common way to produce hydrogen is by steam reforming natural gas. But biogas, oil and coal can be used to extract hydrogen as well. Electrolysis, where electricity splits water to hydrogen and oxygen, is a useful method for producing hydrogen from renewable energy sources like wind, solar and hydro power. In this way hydrogen can play a role to balance the grid when more renewable and intermittent energy sources are introduced.
In the chemical and petrochemical industry, a large amount of hydrogen is produced as a byproduct. The hydrogen from the chemical industry is an important source of fuel for the first infrastructure being built up for FCEVs. For future hydrogen infrastructure the source for production will depend on the given local conditions.
Safe and easy to handle
Hydrogen gas is explosive under certain conditions, but is not more difficult to handle than other fuels and energy carriers. Hydrogen is transient and disappears quickly in open air, as if a leak should occur during fuelling or at a car accident. Hydrogen is non-toxic and burns rapidly. This does not mean that hydrogen is totally safe. An explosion can occur if oxygen and hydrogen is blended in a confined space under specific conditions. As with other fuels and energy carriers, hydrogen must be handled with special requirements. Since hydrogen has been used in the industries for over a century, we have very good knowledge of how to deal with it in order to minimize the risk of incidents.
Fuel Cell – An efficient energy converter
A fuel cell is an energy converter that efficiently transforms the chemical energy in hydrogen to electricity and heat. The rest product is pure water. Fuel cells can be used for a variety of applications. One is producing the electricity for an electric engine in a vehicle. The efficiency is high in both the fuel cell and the electric engine when driving a car of regular size. Compared to a regular car with combustion engine, the FCEV will be about twice as efficient.
Electricity created through anodes, cathodes and membranes
There are different kinds of fuel cells. Generally you can say that a fuel cell consists of an anode side and a cathode side that are separated with a membrane that only allows protons to pass (forcing the electrons to take a detour). When pressurized hydrogen gas passes the fuel cell from the anode side, the hydrogen molecules split into H+ions and electrons. The electrons cannot get through the membrane and have to take the detour to the external circuit where they generate electricity. On the other side of the external circuit, on the cathode side, the electrons get back to the H+ions and connect with oxygen atoms and water (H2O) is created. A single fuel cell produces only about 0.7 volts. To get the voltage to a higher level, many separate fuel cells are combined to form a fuel-cell stack.
A battery’s best friend
Modern batteries have less energy loss than fuel cells and will play an important role in future transport. But the disadvantages with batteries are that they demand long charging times and are quite heavy. The combination of fuel cells and batteries in vehicles has proven very beneficial. Supplemented with fuel cells, electric cars will dramatically increase range and the refuelling takes only a few minutes. Most of the major car manufacturers are now in the final stages of developing electric cars with fuel cells. In 2015 they are ready for serial production.