3.3. Ossian Developments

This section considers how developments since the publication of the SCDS have affected the expenditure associated with Ossian as a whole.

Each PDE Option has an expected generating capacity of up to 3.6 GW, compared with 2.6 GW as presented in the SCDS. It was assumed that under PDE Option 1 the per MW costs and share of contracts by socio-economic study area would be comparable to the SCDS.
The effect of incorporating fewer, larger wind turbines than PDE Option 1, as PDE Options 2 to 4 do, are considered below.

It is anticipated that fewer, larger capacity wind turbines would reduce some types of construction expenditure, particularly for the inter-array cable supply and installation, anchoring solutions, and the installation of floating foundations and wind turbines. Scottish and rUK-based companies are expected to secure contracts in a number of these categories, and therefore this will result in a comparatively lower share of spend being secured in these in Scotland and the UK, and a lower economic impact than would be the case for a greater number of smaller capacity wind turbines.
Other areas, such as development, the manufacture of floating foundations and wind turbines, and the manufacture and installation of export cables, Offshore Substation Platforms (OSPs) and the operation and maintenance base are likely to be unaffected by the number and capacity of wind turbines in each of the PDE Options.

For operation and maintenance expenditure, core operations are not expected to change, while expenditure on repairs and maintenance (in per MW terms) is expected to decrease due to the lower number of wind turbines. Expenditure associated with rents and transmission charges, which is based on either capacity or output, is expected to remain the same.

The Proposed offshore export cable(s), which carries electricity to the grid, was originally assumed to connect on the east coast of Scotland. However, the Proposed offshore export cable corridor(s) will connect to an onshore converter station(s) in England, meaning that the Proposed offshore export cable(s) could be significantly longer, resulting in higher cable manufacturing and cable laying costs. It was therefore assumed that the cost would be two times greater than previously anticipated, which is equivalent to around an extra £1.1 billion across manufacturing and fabrication and installation.
It was assumed that there would continue to be opportunities for cable laying for Scottish and rUK suppliers, although under the SCDS commitment scenario the offshore export cable(s) are expected to be manufactured outside of the UK.

The Proposed landfall will be located in England, meaning that contracts associated with the Proposed onshore export cable(s) installation and Proposed onshore converter station(s) (collectively referred to as the “Proposed onshore transmission infrastructure”) would not be secured in Scotland as assumed within the SCDS. The total spending associated with these categories is not expected to change as a result of the potential relocation of the landfall.

Transmission Network Use of System (TNUoS) charges are one of the main components of operation and maintenance spend associated with an offshore wind farm. Spending associated with TNUoS was estimated and an assumption was made about the share secured in Scotland and rUK.
Based on the average TNUoS charge paid by offshore wind developers in 2023/24 (Electricity System Operator, 2023) and after excluding the share associated with the capital repayments, it was estimated that the annual operational costs associated with transmission could be £106 million.
Under the original SCDS it was anticipated that 100% of this spending could be secured in Scotland. However, due to the uncertainty around landfall location as noted in sections 3.3.2 and 3.3.3, it is has been assumed within this technical report and within the socio-economics EIA chapter (volume 2, chapter 18) that this would be rUK spend.

3.4. Expenditure by PDE Option

Based on the original expenditure assumptions set out in the SCDS and the adjustments discussed in section 3.3, the expenditure associated with each PDE Option is set out in Table 3.2, Table 3.3, Table 3.4 and Table 3.5. It should be noted that the operation and maintenance expenditure is an average of the first six years, which was included as part of the SCDS commitment scenario.

Up to 265 Wind Turbines	Scotland	rUK	Total
Development	£358 m	£94 m	£471 m
Manufacturing and fabrication	£2,555 m	£749 m	£7,823 m
Installation	£1,148 m	£222 m	£2,748 m
Construction	£4,061 m	£1,065 m	£11,042 m
Annual operation and maintenance	£125 m	£131 m	£276 m

Up to 218 Wind Turbines	Scotland	rUK	Total
Development	£358 m	£94 m	£471 m
Manufacturing and fabrication	£2,462 m	£728 m	£7,639 m
Installation	£1,011 m	£222 m	£2,550 m
Construction	£3,832 m	£1,044 m	£10,660 m
Annual operation and maintenance	£113 m	£129 m	£259 m

Up to 186 Wind Turbines	Scotland	rUK	Total
Development	£358 m	£94 m	£471 m
Manufacturing and fabrication	£2,457 m	£715 m	£7,596 m
Installation	£919 m	£222 m	£2,416 m
Construction	£3,734 m	£1,032 m	£10,483 m
Annual operation and maintenance	£104 m	£127 m	£247 m

Up to 130 Wind Turbines	Scotland	rUK	Total
Development	£358 m	£94 m	£471 m
Manufacturing and fabrication	£2,475 m	£687 m	£7,522 m
Installation	£756 m	£222 m	£2,181 m
Construction	£3,588 m	£1,004 m	£10,174 m
Annual operation and maintenance	£90 m	£124 m	£227 m