CXC researchers Marcel Nedd and Keith Bell, University of Strathclyde, discuss the findings of their recent report on security of electricity supply.

 Just a few months ago, Storm Arwen caused widespread damage across the UK. In Scotland, following damage to the network, more than 100,000 homes were left without electricity, as were hundreds of businesses and transport operators. For some, it took more than a week for power to be restored. Arwen was billed as ‘one of the worst storms in a generation’[1]. Yet, it was followed, within weeks, by Storms Malik and Corrie – and further, widespread power outages.

 Coping with the impact of more frequent extreme weather events is one of several challenges facing the UK’s electricity supply landscape. Over recent decades, the system has adapted to accommodate a vast increase in energy from renewables and a corresponding decrease in large, fossil-fuelled power stations. Scotland has also seen a reduction in production of energy from nuclear power with the recent closure of Hunterston[2]. As well as changes to the sources of energy, the technologies on the system are changing with less use of the sorts of large electrical machines that have been the mainstay for many decades and more use of energy sources connected via power electronic interfaces. This potentially radically alters the dynamics of the system. While all these changes are happening, security of supply still needs to be ensured – being able to access enough dependable sources of electricity to meet the demand for power sufficiently often, and to prevent, contain and recover from any power supply interruptions.

 Our new report  draws on a survey and workshop conducted with industry experts and key stakeholders to build a picture of Scotland’s security of electricity supply today and in the future. It focuses on five aspects linked to security of supply and two others that relate to greenhouse gas emission-reduction targets and offshore wind ambitions. The research identifies some significant challenges while also highlighting steps that can help ensure security of supply as the energy transition continues and the use of variable renewables such as wind and solar power increases.

While expressing strong support for reducing greenhouse gas emissions to net zero, stakeholders raised concerns about how achievable Scotland’s 2030 and 2045 emissions reduction targets are. Many were also not confident Scotland would meet its offshore wind generation capacity ambition by 2030 – although the consultation was carried out before the results of the Scotwind offshore leasing round were announced.

Participants in the research highlighted that it will become more challenging for the electricity system in Scotland to provide a secure and stable supply over the period to 2030 – in particular when faced with periods of ‘wind drought’ when there is little power from wind farms and in ensuring sufficient resilience against disturbances. At the same time, noting Scotland’s place as part of a GB-wide electricity market and network interconnections with other countries, these industry experts and stakeholders expressed confidence in the system’s ability to meet Scottish electricity demand going forward. However, this is dependent on market frameworks and regulatory arrangements keeping pace with changes to the sources of electricity and the technologies.

Key stakeholders proposed a number of actions to help address the challenges identified. These proposals are aimed at both the UK and Scottish Governments as well as electricity network companies, the regulator – Ofgem – and the electricity supply industry as a whole. They include the need to:

• develop a vision for managing a complex electricity system that reconciles various approaches to managing demand alongside consumer protection;
• address market barriers and revise sector regulatory standards to ensure that services from generators, flexible demand and energy storage facilities to support stable operation of the system can be efficiently and effectively delivered and coordinated;
• speed up deployment of engineering solutions to the changing characteristics of the system;
• ensure that the new standard governing speed of restoration in the event of a national blackout is fully complied with;
• explore how local electricity systems and the concept of ‘resilience as a service’ (whereby market-based solutions can help maintain supplies in the event of loss of power from the main network) can contribute to security of supply;
• consider the costs and benefits of a regional capacity market or a similar mechanism aimed at ensuring security of supply in every region of the network, incentivising strategic development of schedulable sources of power at key locations;
• consider the costs and benefits of facilitating new pumped storage hydropower projects and their potential long-term value to the system.

As the recent storms underlined, power outages are highly disruptive for individuals, communities and business. The research revealed strong support for decarbonisation of the electricity system. However, given the many challenges and changes facing the energy sector there is a need to plan ahead and to adapt to ensure security of supply.

At the time of the work, Marcel Nedd was with the Dept. of Electronic and Electrical Engineering at the University of Strathclyde. He is now with SP Energy Networks.

Keith Bell is with the Dept. of Electronic and Electrical Engineering at the University of Strathclyde.

[1] SSEN, ‘SSEN restores power to homes affected by storm Arwen’, 2021. http://news.ssen.co.uk/news/all-articles/2021/november/storm-arwen-red-alert/ (accessed Dec. 20, 2021)

[2] https://www.reuters.com/markets/commodities/edfs-scottish-nuclear-power-plant-hunterston-b-close-after-46-years-2022-01-07/ (accessed 07/02/2022)

Efforts to reduce greenhouse gas (GHG) emissions, together with the increase in electricity generated from renewable energy, are dramatically changing the electricity supply landscape. Among other things, this has involved the closure of large, fossil-fuelled thermal power stations. Such changes introduce challenges associated with security of electricity supply including: having access to enough dependable sources of electricity to meet all of the demand for power sufficiently often; and preventing, containing and recovering from interruptions to supply arising from disturbances. The latter includes the capability to restore supplies following a blackout of the whole country.

This study reports and reviews the opinions of industry experts and stakeholders regarding security of electricity supply in Scotland, collected in May 2021 via an online survey and subsequent discussions in a round table event (conducted under ‘Chatham House rules’) in July 2021. As well as perceptions of the status of security of electricity supply today and in the future, this report presents the consulted stakeholders’ views as to the most significant challenges and the steps needed to ensure security of electricity supply as the energy transition proceeds.

Main issues examined

Security of electricity supply aspects

1. Electricity imports: If there is not enough power available from power plant within a particular area at any one time to match demand in the area, demand could still be served by importing power.
2. Meeting Scottish power demand: Central to electricity security of supply is the capability to meet the consumer’s power demand with a sufficient level of reliability. Considering the transitioning power system, it is important to be confident that demand for electrical energy can be met reliably both now and in the future.
3. Power system operability: Operability of the power system concerns the ability to operate a stable system in which its physical limits and those of its various elements are respected. 
4. Scottish power system resilience: A resilient power system is one that can prevent, contain and recover from interruptions to electricity supply arising from disturbances to the system.
5. Power system restoration: In the event of widespread disruption, the power system must be able to quickly restore critical supplies, and thereby minimise the impact of the disruption to electricity supply. 

Environmental sustainability aspects

1. Meeting Scottish greenhouse gas emissions targets: This aspect provides insights as to the perceptions of power industry experts and stakeholders on the likelihood of achieving Scottish 2030 and 2045 emissions reduction targets.
2. Meeting Scottish offshore wind ambitions: This aspect provides insights on the perceptions of power industry experts and stakeholders on the likelihood of achieving 11 GW offshore wind capacity by 2030.

In recent history, the British electricity sector landscape has changed as more renewables, particularly solar and wind, are connected to the power system. Since 2004, electricity generated from renewables in the UK has increased tenfold, and in 2019 37.1% of total electricity generated was from renewable sources.  These changes have far-reaching implications for the operation of national electricity networks and for ensuring security of supply.

The larger renewable installations are connected to the high voltage transmission network that interconnects the whole of Britain. Smaller ones are connected into the regional lower voltage distribution networks that, typically, transfer power from the transmission network down to each individual electricity users.

The technology used to convert the primary energy source into electricity is very different for renewables such and wind and solar from that used for thermal sources such as fossil fuels and nuclear fission. A common feature of wind and solar generators is the use of power electronic converters. Although the uptake of renewables is in keeping with Britain’s emissions reduction and renewable energy targets, it has the side effect of displacing conventional fossil-fuelled generation and the technical characteristics that these synchronous machines provide to power system operation. As a result, the British Electricity System Operator, National Grid ESO (NGESO), frequently needs to pay conventional power plants to come online and deliver key system services to ensure the security of electricity supply.

Going forward, in April 2019 NGESO announced a target of being able to operate a GB electricity system with zero-carbon generation by 2025. In practice, this means that NGESO aims to operate the system without needing to take actions that would restrict the dispatch of zero-carbon generation in favour of providing balancing services using unabated fossil fuel power plants, avoiding the need to “constrain on” such generators in addition to any that the wholesale electricity market might already be using. In order to achieve this, new service specifications and procurement mechanisms will be required to give NGESO the option of accessing services from zero-carbon technologies rather than coal and gas plants.

Current and emerging system operability concerns in GB cover a broad range of topics. Work recently completed at the University of Strathclyde, outlined in this report, has reviewed: how NGESO currently uses balancing services to manage the power system; possibilities for the future provision of frequency response and reserve; prospects for short circuit current support from power electronic converters; and market changes required to avoid the need for NGESO to constrain on fossil-fuelled generation to support system operability in 2025.