Comparing hydrogen networks and electricity grids for transporting offshore wind energy to shore in the North Sea region. A spatial network optimisation approach.

Abstract

In the North Sea (NS), offshore wind farm (OWF) capacity is expected to explode in the coming years to support decarbonisation goals. To bring these vast amounts of energy to shore, offshore hydrogen production and transportation to shore via pipelines is seen to be a plausible solution. Previous literature has investigated spatially explicit hydrogen networks in the Dutch extended economic zone (EEZ). However, capacitated networks were not considered. This research builds on the previous literature and addresses the following: 1) the effects of spatial complexity and reuse of oil & gas (O&G) infrastructure on networks, 2) the properties of a fully interconnected NS network and 3) a comparison between hydrogen networks and electricity grids.

A three-part model was devised; creating cost surfaces, generating candidate networks and finding optimal network layouts. A cost surface is created using PyQGIS, assigning weighing values to spatial uses in the NS. Using these cost surfaces, candidate networks (PyQGIS) are generated by running least cost paths between sources (offshore hydrogen supply points), sinks (onshore hydrogen demand points), and existing network infrastructure in the NS. Finally, the optimal network layout model (Python) is used to find capacitated infrastructure networks. Costs are calculated in post-processing, finding the network and system levelised costs of hydrogen (LCOH).

The results show that including spatial complexity increases capacity-lengths by 50% - 90% compared to a greenfield approach, as the network routes around high ’cost’ spatial uses. Reusing infrastructure leads to cost savings of 40% for hydrogen networks, as 84% of the network consists of reusing existing O&G infrastructure at low costs. Smaller savings are seen for electricity grids (5%), as only cable corridors can be reused, which do have a low cost saving. Interconnected networks are 38% (hydrogen) to 58% (electricity) larger when compared to isolated networks. Careful planning of interconnection is required to avoid overinvestments in capacity between countries. The interconnected network costs of hydrogen networks range between 14 - 21 B€, while electricity grids range between 87 - 116 B€. In a system context, the difference in LCOH between all scenarios is small, between 1.95 and 2.15 €/kg, suggesting that offshore hydrogen is competitive in 2040.

Based on this study, recommendations can be given. Firstly, extending the scope of the onshore onshore hydrogen backbones to offshore can provide significant cost savings by reusing infrastructure. To facilitate this, regulatory support is needed for integrating O&G infrastructure with OWF and energy islands, as it is currently lacking. Investigating the interactions between spatial uses and network planning can feed marine/maritime spatial planning in order to define large interconnected corridors across EEZs for future installations of infrastructure. These corridors could allow sensible interconnection between countries, avoiding unharmonised networks. Finally, future research should widen the optimisation scope to consider onshore connections and dynamic hydrogen supply and demand, leading to more accurate representations of offshore connections in the NS, while avoiding unnecessary costs in overcapacitated connections.