Hydrogen's capacity to play a beneficial role in the global energy system, connecting together renewable generating capacity with existing fossil fuel infrastructure, is moving from theory to reality.
In parallel with similar programmes by French energy giant GDF, oil major Shell and other leading energy players, in June German power utility E.ON took hydrogen from a power-to-gas demonstration plant in Falkenhagen, northwest of Frankfurt, and injected it into the nation's natural gas grid for the first time.
The demonstration plant had used surplus electricity from a nearby wind farm and transformed it into hydrogen by means of electrolysers made by Canadian company Hydrogenics.
Because of the intermittent nature of renewable energy sources such as solar and wind, which typically produce too much power or too little versus customer demand at a particular moment, they are a variable and therefore often unsatisfactory source of energy for the electricity grid.
That's because national electricity grid systems need to match the supply of generated power to demand at any given time and power companies are incentivised to meet that fluctuating demand through the existing tariff programmes, rather than relying on small-scale, but unpredictable 'distributed' renewable generation such as wind farms or solar parks.
Power-to-gas solves the renewables problem of intermittency by storing energy in the form of hydrogen, which can then be used to generate electricity, stored for later use or injected into the national gas grid.
The added benefits of hydrogen as a flexible energy carrier are that it can fit into a country's existing power infrastructure. There is no need to tear up the existing electricity and gas grid and start afresh.
As such, hydrogen can be stored by co-mingling it into the natural gas pipeline, reducing the overall level of carbon emissions from the gas grid. The stored energy can then be discharged where and when it is needed. The beauty of this approach is that it offers operators across the energy value chain an opportunity to increase both profitability and efficiency. For instance, renewable plant owners can arbitrage the wholesale price of their electricity between electricity and natural gas prices in the market place and, where they have the option of supplying fuel cell electric vehicles, gasoline prices as well.
In addition, the natural gas pipeline owner now has an asset which can be valued as a grid-scale energy storage solution as well as a transmission asset with the opportunity for improved pricing due to the higher thermal capacity of hydrogen blends compared with natural gas. Combined-cycle gas-fired power stations can also use the hydrogen-natural gas blend, increasing their efficiency and reducing their carbon emissions.
All this can be done within the existing infrastructure and without modifications with hydrogen blends containing up to 10-15% hydrogen. The E.ON demonstration is particularly significant as it ticks three boxes: it shows the benefits of hydrogen as a store for renewables-generated power, the flexibility of hydrogen gas within the existing natural gas infrastructure and the potential to achieve the significant and cost-effective scalability needed for energy grids worldwide.
The US Department of Energy recently released a report, "Blending Hydrogen into Natural Gas Pipeline Networks: A Review of Key Issues", which was optimistic about the benefits of injecting hydrogen into the gas pipeline system. Studies are underway into using hydrogen to produce low-carbon 'synthetic' methane. Although significantly less energy efficient than straightforward hydrogen blending, it would allow for more gas to be injected into the grid without significant modifications to the system.
During the E.ON test run, 160 cubic metres of hydrogen were successfully injected over the space of an hour. When the plant comes fully online - currently scheduled for the end of August - it will inject 360 cubic metres an hour of renewable hydrogen into the gas grid.