Dispatchable power generation at sea – proposal for a next step in system integration.
First published in Dutch, as an opinion piece in Energeia of 30 September 2022
In Dutch government’s letter to Parliament on ‘Offshore wind energy 2030-2050’, it proposes a new way of building the energy infrastructure for North Sea wind power, for good reasons: not wind farm by wind farm, as has been done up to now, but targeting large-scale energy hubs. In such hubs, conversion to hydrogen can take place as well; demonstration projects for that are announced for this decade.
In our future energy system, we will also need a substantial storage capacity for hydrogen. With the expected decrease in the cost of electrolysis, it will be attractive to produce hydrogen when supply of wind and solar electricity exceeds the direct demand for electricity. This will happen during peaks that can last days or weeks, but the use of hydrogen in industry, for example to replace cokes and thermal coal in steel production, will have a flat demand pattern.
For that hydrogen storage, there are offshore options as well. The salt layers under the North Sea floor enable the creation of new salt caverns. That is possible under land as well, particularly in the North and East of our country, but construction of a large number of salt caverns there will probably trigger resistance from people living there. When old gas fields under the North Sea prove to be suitable, the potential for large-scale storage there increases substantially.
Hydrogen storage under the sea floor is already being considered, amongst others by TNO and EBN. The combination of electrolysis at sea with hydrogen storage nearby is attractive then. For transport to the onshore users, it may be possible to convert gas pipelines now used to transport natural gas from North Sea fields to land.
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% in a decade from now, in the Netherlands – there is a need for zero-emission dispatchable power generation capacity too. At the logically low capacity factor hydrogen-fueled units are suitable candidates for that: 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; they are already used on offshore oil and gas platforms. Later, fuel cells, now still expensive due to the small market size, can be used 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 the scarce landing points for those. In the modeling study for ‘System integration of offshore wind 2030-2040’, these moments turned out to be the moments 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.
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, a system 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 Dutch 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 does not make it, the other components will still be useful.