Rather than linking each UK Round 3 offshore wind development to the country's electricity grid individually - or radially - the option of developing co-ordinated offshore networks has been examined by UK energy regulator Ofgem and the government's Department of Energy and Climate Change (Decc).
The final report of the offshore transmission co-ordination project concludes that in some locations substantial savings could be achieved if generators shared transmission assets rather than each connecting individually to the mainland grid.
Grid-design options have been assessed for nine UK Round 3 zones: Moray Firth, Firth of Forth, Dogger bank, Hornsea, East Anglia, Hastings, West Isle of Wight, Bristol Channel and Irish Sea. The financial benefits of co-ordinated rather than radial grids appear to be zone-specific.
For relatively small near-shore Round 3 projects, such as E.on's 600MW Hastings (Rampion) project, a radial point-to-point connection is likely to be optimal. Assessment of the Firth of Forth and the East Anglia zones indicates there may be no practical financial difference between the two grid-design approaches.
However, across the larger Dogger Bank and Hornsea zones co-ordinated networks could result in a 16% cost saving when compared with a radial configuration, concludes the report, assuming that the required 2GW HVDC technology is available. If 2GW cabling is not possible, a co-ordinated approach could prove more expensive.
Co-ordinated offshore grids offer the possibility of lower capital costs, fewer environmental impacts and reduced planning-related delays. The prospect of co-ordinated networks to serve the offshore wind sector was a major driver in the decision to extend National Grid's system operator responsibilities beyond land. However, many who contributed their views during the consultation stage of the project said they believed the UK's existing policy and regulatory framework could prove insufficient to ensure significant levels of grid co-operation.
The modelling that underpins the UK government's report was undertaken by TNEI/PPA Energy and Redpoint Energy and assumed a series of offshore installation scenarios by 2020 of between 9GW and 23GW.
Improving the financial viability of offshore wind farms via the use of co-ordinated networks is also raised in the latest offshore wind-power survey produced by management consultancy PwC. "Grid access is proving a bottleneck in all countries trying to realise offshore wind capacity," states the survey. "A modular approach where each wind farm is connected on a stand-alone basis makes sense only if other wind-farm plans are not yet definite. But if they are, planning the grid connection collectively could allow valuable economies of scale and scope to be achieved that will benefit all offshore wind farms and, ultimately, the taxpayer."
PwC's survey also acknowledges a lack of clarity about who would be responsible for network development: "There are questions around who should be responsible for the connection - the developer, the national transmission system operator (TSO) or other players".
Ninety percent of European power utility respondents to PwC's survey said they believed that mandating utilities to lay grid lines needed "a lot" or "some" improvement, and 80% said they believed more financial support was needed for grid connections.