Offshore wind power has become one of the workhorses of the European energy transition, and the North Sea is its hotspot. Plans are now being made to connect large capacities of offshore wind to energy hubs, where transmission can be combined with hydrogen production and storage. For periods with little wind and sun, we will need a lot of dispatchable generation capacity in our power system, i.e. electricity sources that can be brought online on demand, for which hydrogen is a prime candidate. Adding this to the offshore energy hub as well could make good sense.
HYDROGEN PRODUCTION AND STORAGE AT SEA
Denmark, Germany, The Netherlands and Belgium are moving towards a new way of building the energy infrastructure for North Sea wind power: not wind farm by wind farm, but in large-scale energy hubs. In such hubs, conversion to hydrogen can take place as well and demonstration projects have already been announced for this decade.
In a future electricity system with high shares of wind and solar power there will be periods of days and weeks in which the wind and solar power production together exceed the direct demand for electricity. The expected decrease in the cost of electrolysis will make it attractive to produce hydrogen in such periods. However, the use of hydrogen in industry follows a flat demand pattern, for example to replace cokes and thermal coal in steel production. To bridge the peaked supply of hydrogen with this flat demand for it, we will also need a substantial storage capacity for hydrogen in our future energy system.
Offshore options for hydrogen storage are available. The salt layers under the North Sea floor enable the creation of new salt caverns, and depleted gas fields may be reused for storage on an even larger scale. This is possible under land too, but construction of a large number of salt caverns or using old gas fields to store hydrogen may encounter resistance from people living there.
Hydrogen storage under the sea floor is already being considered, amongst others by TNO and EBN in the Netherlands. This makes the combination of electrolysis at sea with hydrogen storage nearby attractive. For transport to the onshore users, it is possible to convert gas pipelines now used to transport natural gas from North Sea fields to land.
ADDING DISPATCHABLE POWER GENERATION
An interesting next step can be to site dispatchable power production on the energy hubs as well. In a system in which most electricity comes from wind and solar – over 70% by 2030, in Germany, the Netherlands, and Denmark – there is a need for zero-emission dispatchable power generation capacity too. This can be switched on to produce power in periods of days and weeks with too little wind and solar.
Hydrogen-fuelled units are suitable candidates: they have relatively low investment costs per unit of capacity, and they can deliver the desired flexibility. At first, these will be gas turbines or combined cycle units; these are already used on offshore oil and gas platforms. In the future, fuel cells, now still expensive due to the small market size, can be an option as well.
The nice thing is that, when low wind speeds trigger a demand for dispatchable power, the electricity cable from the energy hub to land has capacity available, for the same reason. This way, the combination of functions leads to an even better use of costly cable capacity and their scarce landing points. In a major Dutch modelling study, these moments turned out to coincide with the highest demand for hydrogen transport capacity too. So, it is an advantage to have the dispatchable power capacity close to the hydrogen storage.
INTERNATIONAL CO-OPERATION TO MAKE IT HAPPEN
When, as foreseen, the energy hubs will become part of an international energy network, the complete system can work even more efficiently: around the North Sea, the hours with a high demand for dispatchable power will occur at different times.
This way, the combination of offshore wind with hydrogen production, hydrogen storage, and dispatchable power generation can become a robust pillar of the zero-emission electricity system of the future.
To make this happen, we will need to make policy choices to promote this development in an integral way, since such a total concept will not develop at the right speed organically. We would need an exploration of the concept soon, followed by steering towards building the combination at the location of one of the North Sea energy hubs now to be planned.
Successively, we can take the necessary steps to assess the solution on its merits. When, in the end, one of the components turns out not to be feasible, the other components will still be useful.
About the author:
Kees van der Leun has been an energy transition consultant for over 35 years, after joining the start-up Ecofys in 1986. In recent years, he has focussed on strategies for energy system integration, including work for Gas for Climate, the European Hydrogen Backbone, and North Sea Wind Power Hub. In 2021, he founded the new consultancy Common Futures together with Daan Peters. The growing team fully focusses on energy system optimisation, with special attention for the integration of offshore wind and the role that renewable gases can play.
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- Publication date
- 24 January 2023
- European Climate, Infrastructure and Environment Executive Agency