Taking a coordinated approach to the connection of offshore windfarms could save consumers up to £6.5 billion by 2050, National Grid Electricity System Operator (ESO) has forecast in a new report.
The ESO said building an integrated offshore transmission network rather than connecting windfarms on an individual basis could reduce capital expenditure by £5.5 billion (19 per cent) over the next three decades and operational expenditure by £1 billion (14 per cent).
The study was conducted as part of the review of offshore transmission infrastructure led by the Department for Business, Energy and Industrial Strategy (BEIS). It was based around the ‘Leading the Way’ scenario from the ESO’s latest Future Energy Scenarios in which offshore wind capacity surpasses 83GW by 2050.
The ESO said an integrated approach to the development of offshore transmission infrastructure could reduce network costs by up to 18 per cent by the middle of the century, although the savings are likely to be much greater – up to 30 per cent – in instances where large volumes of generation need to be connected to an already congested part of the onshore network, or where the windfarms are located far out to sea.
“As the volume and distance of offshore connections increases, the integrated option becomes increasingly cost effective,” the report explained. “The regions in which the benefits are highest are also those with the fastest earlier deployment. There is therefore benefit from moving to an integrated approach as soon as possible.”
Some of the savings would come from reduced flows on the onshore network, which could fall by between 35 and 60 per cent depending on the region. There could also be significant environmental and social benefits, with the number of onshore and offshore assets, cables and landing points being introduced by around 50 per cent.
National Grid said the majority of the technologies required to build an integrated offshore transmission network is available now or will be by 2030, the exception being high voltage direct current (HVDC) circuit breakers, which are not currently in commercial use in Europe.
The ESO said: “Almost all the HVDC systems in operation today have been developed as point-to-point systems without the use of circuit breakers.”
“If HVDC circuit breakers are not available in time, an integrated approach can still be progressed,” it added. “However, there would be more network infrastructure required, coming at an additional cost. This would also have the potential to increase the likelihood of network faults and therefore impact on system reliability and operability.”
The study also assumed that cables with an individual capacity of 1.8GW will be available by 2040: “Two such cables together in a bi-pole arrangement will allow connections of 3.6 GW. Currently, the highest individual HVDC cable capacity that is widely available is 1.4 GW, with higher capacities limited in supply options.”
National Grid additionally identified several potential regulatory barriers, saying a review of the Grid Code to clarify the rules for windfarms connected an offshore network is “essential”.
It said the Security and Quality of Supply Standard, which “effectively limits offshore connections to 1.32 GW normal loss of power infeed risk”, should likewise be reassessed, whilst also noting: “If changes to the infeed loss are progressed, there will be corresponding operational changes and costs associated with the requirement for an increased reserve holding.”
ESO director Fintan Slye said: “Our project is assessing the most beneficial approach to offshore networks, examining a range of different technical and engineering solutions to grid connections – all aimed at ensuring value for money for consumers, facilitating offshore wind’s contribution to the net zero target and reducing the environmental and social impact of the connections onshore.
“Our initial analysis already shows the potential for significant cost savings and a reduced need for physical infrastructure but it’s crucially important we hear from a variety of stakeholders in this consultation, including coastal communities, developers and transmission owners. These views will help shape recommendations and proposals as the project moves forward.”