Scottish wind farms called upon in the Balancing Mechanism: Management of wind resources is a critical tool for National Grid in dealing with system constraints, supply and demand imbalance and increasingly inertia*. Data from Cornwall Insight’s Balancing Mechanism (BM) Service highlights that wind was the first most utilised renewable technology asked to turn down in the BM.
Further analysis also showed that of the top 14 onshore wind generators by accepted bid volumes – those asked to turn down production – all were located in Scotland in August 2019.
The below chart shows this price range for the top 14 onshore wind generators by accepted bid volumes in August. It also indicates that bid prices were in the range of -£65/MWh to -£73/MWh. As a result, generators were asked to turn down their output.
James Brabben, Wholesale Manager at Cornwall Insight, said:
“This trend is fundamentally down to the high proportion of onshore wind located in Scotland, but also constraints on the network. Effectively when there is high wind output in Scottish wind farms, especially Northern Scotland, restrictions on the physical network make it difficult to transport power to areas with more demand, which are predominantly located further south.
“National Grid will often constrain wind production to avoid system issues and provide a constraint payment. This issue has been exacerbated recently with problems surrounding the newly commissioned High-Voltage Direct Current HVDC Western Link. Instead of reducing constraint payments recently these payments have hit record monthly highs this year and topped £8.5mn alone in August.
“Constraints are clearly reflected in BM actions, analysis from Cornwall Insight shows that 91% of wind actions taken in August are what is known as ‘SO-flagged’. This is where balancing actions are flagged as system issues – such as constraints – rather than energy issues.
“The high volume of flagged actions clearly shows how physical system constraints are impacting the BM, leading to large volumes of wind generation each month being curtailed. While the development of further onshore wind in Scotland is crucial for further growth in renewable electricity, interactions with the physical network will create challenges and likely lead to greater levels of activity in the BM unless further network reinforcements or solutions are found.”
*Inertia determines how quickly frequency changes on the electricity system. The higher the level of inertia the lower the level of RocoF (Rate of Change of Frequency) and the more time National Grid ESO has in returning frequency back to stated levels. Inertia levels have been reducing on the electricity system in GB over recent years with the increasing penetration of variable renewables and closure of some large scale thermal assets. Large scale thermal assets typically provide inertia to the system as they are synchronously coupled to the network, unlike most renewables technologies.
Press release by Cornwall Insight