Constructing and analysing offshore hydrogen system designs powered by wind farms in the North Sea - A multi-sink multi-source network optimisation approach

Abstract

To provoke the needed energy transition, European Union (EU) countries initiated significant offshore wind energy investments in the North Sea. However, there also exist adverse aspects to the use of higher renewable electricity levels:

• renewable energy sources, such as offshore wind energy, may threaten the security of our energy system, since they are characterised by a high variability, and limited predictability and controllability;

• the effectiveness with respect to decreasing greenhouse gas emissions is limited, because electrification can be not applied within all sectors, such as heavy industry and heavy duty transport;

• a large increase in offshore wind capacity requires moving further off shore. This results in relatively high costs because of the energy losses within the (longer) electricity cables.


One way of coping with these challenges, is by producing hydrogen offshore, by means of wind energy, and transporting it to shore by for example repurposing the existing offshore natural gas infrastructure. Such an offshore hydrogen system located in the North Sea might sound favorable; however, the feasibility of such a system on this scale is yet to be determined.

In this thesis the possibility is investigated to design a future proof offshore hydrogen system. Such a system would consist of (current as well as new) wind farms, electrolysers to produce hydrogen by using (a part of) the electricity generated by the wind farms, and an infrastructure to bring the hydrogen to shore. Given the EU investment plans in offshore wind energy, a phasing period is used from 2030, 2040, to 2050. This research is done by:

• deriving multiple hydrogen system designs by for example optimising the transmission infrastructure;

• analysing the supply potential of these system designs.


The results show that a cost-competitive hydrogen system in the North Sea can be realised. The proposed system design has a Levelised Cost Of Hydrogen (LCOH) of 2,08 EUR/kg and a positive Net Present Value (NPV) for the most relevant pricing scenarios. This LCOH is relatively low compared to other researches, which are mostly between 2 and 3,5 EUR/kg.

An interesting result concerns including refurbished pipelines of the existing offshore gas infrastructure. When using only new pipelines, the transmission infrastructure costs increase with 36%. Furthermore, the results show that it is more cost-efficient to downscale electrolyser capacities than to use the peak of the available electricity to determine the capacity of the electrolysers. Additionally, the productivity of the wind farms can increase up to even 220% by using the different electricity surplus for hydrogen production.

Based on this research, recommendations can be given:

• National governments should formulate policy on whether or when gas extraction in the North Sea should stop. Thereupon, the (energy) transmission system operators should scope their plans towards transporting offshore hydrogen to onshore, as well as start planning the onshore hydrogen backbone.

• The EU should decide whether to build one interconnected system in the North Sea, or multiple isolated (per country) hydrogen systems. Based on this decision, it is important to start shaping rules and standards for hydrogen trade, as well as determining regulatory regimes to support offshore hydrogen production.

• Further research should be done on the electrolyser costs and efficiencies, as well as the different types of electrolyser locations; on the possibilities of hydrogen storage; and, to include (regional) hydrogen demand values.