By way of example, existing infrastructure in Germany has enormous storage capacity available, due to the country’s huge gas consumption.
According the German Ministry for Economic Affairs and Energy, natural gas accounts for approximately 20.5 per cent of the nation’s primary energy consumption, with overall consumption of 85 Bcm in 2014, while the total length of the German gas network sits at around 510,000 km. More than 20 per cent of annual gas sales can be stored in underground storage reservoirs over a period of a month, or even years.
Given this existing capacity, surplus power from renewable energy sources can be used to power hydrogen electrolysis and feed hydrogen directly into the natural gas grid.
“The only method to store this amount of power is to convert it into a chemical substance – hydrogen – which we can then inject into the gas grid, or convert into methane,” Dr Linke says.
“Our grid, the transmission compressor units, underground storage facilities and gas appliances are capable to operate with different gases. A blend with 2 per cent, or even up to 10 per cent hydrogen, is unproblematic. Higher hydrogen production rates can be absorbed as well if we convert hydrogen to methane.
“For this process carbon dioxide is used – preferable to renewable sources like biomass. That means that you can store an enormous amount of energy in the natural gas grid.
“Generally speaking, the storage capacity is sufficient to integrate the entire power production from wind energy of more than 30 GW installed capacity. Therefore, the natural gas grid can become the backbone of the power grid. This is what we call the convergence of two systems, or sector coupling, so coupling of the power sector with the gas sector.”