(Right) The Northern Isles Network link

The objective of the ISLES study was not to ‘engineer’ a single ISLES concept for Front End Engineering and Design (FEED) or detailed engineering but to assess the landscape of existing and planned, offshore and onshore, generation and transmission, developments; and from this, construct a number of realistic concepts that allowed us to evaluate key challenges and questions surrounding any ISLES development. 

These include, inter alia, scale of generation, offshore technology and routing constraints, development competitiveness, market integration, connection capacity and reinforcement, the value of interconnection.

The initial maximum resource potential for the ISLES Zone is estimated to be of the order of 16.4 GW, comprising 12.1 GW of offshore wind and 2.3 GW of wave and tidal. The ISLES concepts, Northern ISLES and Southern ISLES, postulate the connection of 2.8 GW and 3.4 GW respectively of generation resource and interconnection capacity by circa 2020 described as "ambitious but achievable and backed by the European Regional Development fund. 

(Below) Northern Isles network topology

An undersea grid capable of transmitting 2.8GW of renewable generated electricity on a northern network stretching from Scotland to Northern Ireland.

And a second southern "ISLES" grid, would hook Wales with Ireland, and handle 3.4GW.

"No technological barriers" stand in the way of the idea, which would use high voltage direct current and voltage source conversion technology. 



Co-ordination of build under an integrated network has the potential to reduce environmental impacts and consenting uncertainties associated with onshore grid connection.

The Southern Isles network link (right)
Due to the cross-border nature of ISLES, there are particular challenges in navigating both complexand evolving onshore/offshore planning and licensing regimes, in addition to changing legislative frameworks in all three jurisdictions.

ISLES network CAPEX is of the order of £5.6bn for the combined concepts, equating to circa £1m/MW of offshore network capacity. The level of subsidy required for generation connected to ISLES to be bankable is estimated to be in the region of £79-85/MWh, approximately equivalent to 1.8-1.9 ROC.

ISLES combines interconnection and generation, a case can be made that this could result in synergistic benefits by increasing the utilisation of the network.

In the case of Southern ISLES specifically, approx. £170m per annum of savings are possible overall, mostly attributable to the all-island market. Expressed differently, if all these savings could be apportioned in some manner to offset the capital cost of the network, the subsidy level required would drop by around £4.50/MWh to £74.5/MWh.

(Below) Southern Isles Network topology
ISLES network CAPEX is broadly of the same order of magnitude, potentially 15-20% higher than comparable stand-alone projects which might be developed under the UK government’s Round 3 Offshore Wind Development process. However, the increased development costs can be offset through a variety of economic and market benefits.
 
The ISLES project would require  navigation of complex cross-jurisdictional legal barriers and be costly to implement. Subsidies required to get it up and running -- and likely to be borne by ratepayers -- work out to about $1.6m per MW of offshore network capacity.

The plans are part of a larger-scale EU effort to develop a continent-wide supergrid that would allow for the import and export of electricity based on the fluctuating availability of renewable energy sources such as wind, solar and wave.

Scottish Secretary for Finance and Sustainable Growth, John Swinney said the study, "shows that, by working together on a shared renewables grid, we could boost jobs, revenue and economic growth -- as well as helping secure future renewable energy supplies.

Northern Ireland Energy Minister Arlene Foster agreed. "The ISLES concept study presents us with a realistic picture of an energy future where the regional wind, wave and tidal energy resources located far off our coasts are harnessed and used for our mutual good."

She cautioned however "significant challenges to government and potential investors" when it comes to working through issues of regional jurisdiction and the integration of local transmission grids, as well as a need to avoid placing "undue costs on the end customer."

The offshore grid study comes shortly after the Marine Energy Science report and the  British Energy Minister Charles Hendry calling for greater cross-border cooperation between Britain and Ireland in the development of renewable energy. "Movement toward a single European energy market presents a real opportunity for Ireland and the U.K. to achieve substantial revenue benefits from electricity exports," he said.

Scottish Energy Minister Fergus Ewing welcomed Hendry's comments "This underlines the case the Scottish government has been making about moving beyond national territories into a single European energy market and his comments demonstrate Scotland is plugged into an interconnected Europe."