Offshore wind to green hydrogen: opportunity assessment

Footnotes

1 For unit conversion between kg and MWh, the report is using energy density of hydrogen based on Higher Heating Value (HHV) of 141.9 MJ/kg (39.4 kWh/kg) to reflect the most end-use agnostic estimates (e.g. ammonia or refining sectors can use hydrogen directly).

2 To gain a better understanding of the scale, the UK overall energy consumption in 2018 was 1,663 TWh.

3 Figure 1.1 only includes dedicated hydrogen production without hydrogen produced as a by-product.

4 Figure 2.3 only includes demand for pure hydrogen without hydrogen mixed with other gases.

5 Ammonia production refers to the fuel production for the shipping sector. Hydrogen use for industrial ammonia production is included within the industry use.

6 This statement indicates the scale of opportunity rather than making future projections within each sector.

7 Hydrogen blending is a process where low-carbon hydrogen is mixed with natural gas in the gas pipeline network to lower the carbon intensity of the end-product.

8 Sector coupling means integrating various supply and demand sectors into a whole-system network to increase the overall efficiency and cost-effectiveness.

9 Gas peaking plant (also known as peaker plants) are used for grid-balancing services, when electricity demand exceeds supply. They are used as a back-up power source, particularly within networks with higher shares of renewable power generation.

10 Partial oxidation is a chemical reaction method in which natural gas or heavy hydrocarbons are partially combusted in a reformer, producing a hydrogen-rich syngas

11 It should be highlighted that the average fuel economy of hydrogen buses is uncertain. One report stated a fuel economy of 10.3 kg of hydrogen per 100 km (Element Energy, 2017), which would decrease the cost parity in 2032 from £5.5 to £4.7/kg.

12 This cost is similar to Europe’s bunker fuel cost in Q4 2019, which was £0.44/kg (S&B, 2020).It should be highlighted that banker fuel cost is fluctuating significantly depending on the oil price. For example, banker fuel cost in April 2020 was only £0.17/kg.

14 It was assumed that brown hydrogen used as chemical feedstock does not attract any tax, since many brown hydrogen users generate their hydrogen on-site and use it as chemical feedstock in the same location.

15 Based on the following assumptions: Offshore wind capacity factor = 0.5, hydrogen system availability factor = 0.95, electrolysis efficiency (2025) = 18.87 kg/MWh (IRENA, 2018), electrolysis efficiency (2032) = 20.00 kg/MWh (Hydrogen Europe and Hydrogenics), electrolysis efficiency (2045) = 20.55 kg/MWh (Project Dolphyn).

16 Equal to Scotland’s hydrogen demand projections scenarios assessed in Section 2.2.

17 Offshore wind capacity required to be solely dedicated to hydrogen production, if Scotland’s entire hydrogen demand was to be met.