In a scenario in which the UK’s decarbonisation targets are met by large-scale generation on the transmission network, offshore wind farms could have a combined capacity of 29.9GW by 2030 and 43.4GW by mid-century.
The grid operator predicted "strong" offshore wind growth in each pathway examined in its Future Energy Scenarios report.
The report set out four possible forecasts based on differing levels of decarbonisation and decentralisation.
However, under a more decentralised scenario whereby the UK fails to achieve the 80% carbon reduction by mid-century, UK offshore capacity might only reach 16.8GW by 2030 and 21GW by 2050, according to National Grid.
National Grid also predicted onshore wind will grow in all scenarios. However, a "facilitative policy environment for local wind schemes" is assumed in each forecast.
Under the most favourable scenario, in which the energy landscape becomes more decentralised, onshore capacity could reach 23.4GW by 2030 before expanding to 50.7GW by mid-century.
The UK's current onshore wind fleet stands at just over 12GW.
The grid operator stated due to its "favourable wind conditions and availability of land", much of this capacity growth would be in Scotland.
However, under the ‘steady progression’ pathway, minimal growth could lead to total onshore installations reaching 15.5GW in 2030 and 16.4GW twenty years later.
In this scenario, there is a greater emphasis on large-scale generation, including offshore wind and nuclear, as opposed to the more localised solar and onshore wind projects.
There would be "little difference" in cost between the two scenarios in which wind – onshore and offshore – expands the most: Two Degrees and Community Renewables.
The former would deploy large-scale generation such as offshore wind and nuclear, with high capital expenditure, while the latter would use higher volumes of small-scale generation such as solar and onshore wind, with 43GW extra capacity by 2050.
National Grid did not see further price falls occurring for onshore wind.
However, the report's authors wrote: "We anticipate some positive spill-over effects from offshore wind developments. This could include innovation in maintenance and the further growth of supply chains.
"Co-location with storage is another factor that can enable developers to reduce connection costs and access other revenue streams."
Under all its scenarios, National Grid predicts:
- There will be high levels of overall generation growth – especially in the more decarbonised scenarios. "High levels of intermittent and inflexible generation will require high levels of new flexibility, and there may be some periods of oversupply," the authors explained. "Interconnectors and electricity storage will play a key role in easing this";
- Carbon intensity of electricity generation will fall quickly;
- Greater levels of flexibility, including higher levels of storage, will be needed.
National Grid’s report comes in the same week that the UK’s National Infrastructure Commission issued a report recommending onshore wind be readmitted back into the contract for difference (CfD) auction scheme from the early 2020s.
Plans to end the previous Renewables Obligation support scheme were first announced in 2015, and the government also barred onshore wind projects from competing in the UK’s second CfD auction.
Reacting to the reports, Greenpeace’s chief scientist Doug Parr said: "The government needs to move faster on renewables and electric vehicles to meet carbon targets.
"These scenarios clearly demonstrate how government policy is central to the speed of decarbonisation and public adoption of cleaner technologies."
The UK currently has more than 12.1GW of onshore wind and more than 7.1GW of offshore wind installed, according to Windpower Intelligence, the research and data division of Windpower Monthly.
Under the Climate Change Act 2008, the UK must reduce greenhouse gas emissions by 80% from 1990 levels by 2050.