As the world sees the amount of renewable energy supply to the electricity grids increase, the intermittent nature of this supply when compared with traditionally stable demand becomes increasingly difficult.
Individual wind farms now generate gigawatts of electricity which makes the need to create an effective energy storage solutions increasingly important. Countries which exceed 20% renewable content in their energy mix face source curtailment due to grid balancing issues. So, local and grid-wide instabilities are beginning to emerge. This is driving the need for long term, large scale energy storage solutions.
Various technologies exist which address different electrical system requirements of which hydrogen is one.
Water electrolysis is one of the most promising solutions to the problem on a large and long term scale. Excess/curtailed energy from various renewable sources can be passed through a rapid response PEM electrolyser (see hydrogen production) which splits water into oxygen and hydrogen. The produced hydrogen can be stored in classic pressurised tanks, pipes and underground caverns – this is a particularly potent technique because hydrogen gas has the highest energy content per unit of mass of any fuel, making it great for holding and thus distributing energy!
Many countries have a natural gas distribution grid. The use of this grid as a sink for the produced hydrogen, either as a mix or a pure gas can offer vast amounts of renewable energy storage – see gas grid injection. The hydrogen can also be combined with carbon dioxide to produce synthetic methane (SNG). Power-to-Gas is the generic name given to this process. This SNG can be introduced to the natural gas system.
The hydrogen produced from electrolysis can therefore be stored using technology that is being implemented in Ireland today, whether it be as a gas under high pressure in underground stores, at very low temperatures, as a liquid or adsorbed to specific molecular complexes. Hydrogen’s wide array of possibilities means that it has the potential to be the forefront of the energy storage solutions for years to come.