Hydrogen can be used to store energy, as a fuel for the internal combustion engine, gas turbine and the fuel cell (see section ‘Fuel cells’, Chapter 3).

Energy storage

There are a few examples of hydrogen being used to store energy in situations where excess electricity is being generated from sustainable sources such as wind and solar

power. These energy sources are intermittent and to balance out the dips in electricity production the stored hydrogen is used to fuel a generation system. One example is the island of Utsira off Norway where electricity is provided by wind power. Surplus electricity is used to electrolyse water and the hydrogen formed stored compressed in a large tank. When the wind does not blow the stored hydrogen is used in a modified internal combustion engine to drive a generator.

Another example was a combined photovoltaic and wind electricity generation system in Cooma, Australia (Shakya et al., 2005). Here again the surplus electricity was used to electrolyse water and the hydrogen stored compressed in a cylinder with a capacity of 5.5 m3 at 24.5 MPa (3552 psi). It was found that the electricity generated was more expensive than grid-connected electricity, as expected, but costs could be reduced as over 50% of the capital costs were the electrolyser and purification com­ponents. A reduction in the cost of these components would reduce costs consider­ably. The system still has great merit in situations where no grid supply is available.