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Going offshore (part 2)

The UK offshore wind, wave and tidal power resource could supply about six times current levels of electricity demand, and even if we only exploited part of it, the UK could become a net exporter of power, according to the first comprehensive assessment, The Offshore Valuation produced by an informal collaboration of government and industry organisations co-ordinated by the Public Interest Research Centre (PIRC).

Drawing on published data, it puts the total practical offshore resource at 2131 TWh p/a from 531 Gigawatts (GW) of generating capacity, 406 GW of which would be wind capacity. England had 54% of the total practical resource (286.5 GW), Scotland 39% (206 GW) and Wales 7% (39.5 GW), with wind power dominating in each region.

PIRC point out that their scenarios “are neither predictive nor prescriptive” but calculate that, even if only 29% of the total resource was exploited, by 2050, the UK could have 169 GW of offshore capacity, supplying 610 TWh, equivalent to total electricity consumption by that time, making the UK a net electricity exporter.

Most of the supply capacity (116 GW) would be conventional sea-bed mounted offshore wind but there would also be 33 GW of floating wind turbines, further out to sea, plus 5 GW of wave, 9 GW of tidal stream and 6 GW of tidal-range projects. This would create 145,000 new jobs, provide the Treasury with £28 bn in tax receipts and reduce carbon emissions relative to 1990 levels by 30%.

Under a more ambitious scenario, utilizing 76% of the total practical resource, by 2050 there could be 406 GW of offshore capacity generating 1,610 TWh – about the same as total UK energy demand (not just the electricity demand) expected by then. That would involve an additional 212 GW of floating offshore wind capacity, while wave would rise to 14 GW, tidal stream to 21 GW and tidal range to 10 GW. The jobs total would rise to 324,000, most of these being for the floating wind turbines.

Some of the scenarios are clearly very ambitious. Even using just 13% of the total, to supply 50% of UK power would need a 34 GW mix of back-up/storage/interconnector links to balance variable supplies, and if higher percentages were used then more cross-channel interconnection would also be needed for exporting excess power – 85 GW for the 169 GW scenario and 321 GW for the 406 GW scenario.

So what would it cost? Using DECC figures, PIRC estimates that the 169 GW scenario would cost £443 bn but calculates that in 2050 it would earn £62 bn p.a in net electricity exports. The 406 GW scenario would cost £993 bn and earn £164 bn p.a. Most of the technologies cost £100–125/Mh initially but get cheaper (10% p.a “learning rates” are assumed), though wave and tidal range are more costly, at ~ £175/MWh.

Most of the technology exists or is under development, but floating offshore wind turbines are relatively novel and clearly play a major role in the more ambitious scenarios. As noted in my previous offshore wind blog entry, some floating systems are already under development but there may be limits to what can be obtained from them. The PIRC report states: “The technical limitations of current designs restrict floating wind to water depths of between 60m and 700m. There has also been some concern that it will not be possible to install floating wind beyond 100nm from the coast due to the time taken to get to and from the site.” Also “access for installation and maintenance may be limited”. Of course, the longer undersea grid links to land will cost more. Even so, the resource is huge. The PIRC puts it at 870 TWh/yr, with a further 660 TWh/yr available beyond 100 nm out. That compares to 180–240 TWh/yr for conventional fixed offshore wind, additional to current site allocations.

The resource for wave and tidal range (barrages/lagoons) is seen as much smaller, at 40 TWh/yr and 36 TWh/yr respectively but that for tidal streams is seen as more significant at 116 TWh/yr. This is larger than some previous estimates. The PIRC says: “Until recently the UK’s practical resource had been estimated to lie within the range 4–30 TWh/yr. However, academic research has since highlighted uncertainty in both the underlying methodology and the assumptions used to estimate this resource, which has had the impact of increasing this range to 4–110TWh/yr.” It notes that the “kinetic energy flux” method is widely used (e.g. by Black and Veatch) but Stephen Salter’s “bottom friction” and David MacKay’s “shallow wave” method both give a factor of 10–20 more. To navigate these uncertainties a “bottom-up” calculation was employed by the PIRC to get the technical resource and this was then reduced by 60% to provide an estimate of the practical resource. It was put at 33–200 TWh/yr, corresponding to a power density of 5 MW/k sq m and 30 MW/k sq m respectively. The average of this range – 116 TWh/yr – was used in the report.

The group behind the report, co-ordinated by the PIRC, included the UK, Scottish and Welsh governments, the ETI, the Crown Estate, E.ON, DONG, RWE Innogy, Mainstream Renewables, RES, Scottish and Southern Energy, Statoil, and Vestas. The government’s Climate Change Committee also provided some support.

Tim Helweg-Larsen, director of research at the PIRC, said: “To discover that we own a resource with the potential to return the UK to being a net power exporter, and on a sustainable basis, is genuinely exciting, and a wake-up call to those in a position to foster the further development of this industry.” But, to put the UK on a path that allows it to access its “substantial and valuable” resource, the PIRC said that Round 3 offshore wind grid connections would have to be made “super-grid compliant” to enable potential future electricity sales to Europe. The PIRC wants the government to take a leading role in the current EU super-grid negotiations, to ensure that the UK derives maximum value from its design and implementation. The domestic supply chain would also have to be developed to enable economic deployment at scale, while new financing structures would have to be created to support the scale and pace of the industrial growth required.

Peter Madigan, head of offshore renewables at trade association RenewableUK, said that “we have long been saying that the North Sea will become the Saudi Arabia of wind energy” and the results of this study “amply bear this out”.

As I discussed in my previous blog entry on this topic, environmental impacts must of course be considered. For example, offshore systems have the potential for significant effects on marine wildlife, including dolphins, porpoise, grey seals and wildfowl but a range of environmental studies have been completed or are in hand and so far no major problems seem to have emerged that cannot be limited with by sensible design, location or mitigation measures. So it does seem that the UK could be on to a winner.

Source: PIRC

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