Getting to Net Zero: What happens when the wind stops blowing?

Whilst Extinction Rebellion occupies London’s streets to highlight the climate and ecological emergency, leaders from across the energy industry assemble nearby at Aurora Energy Research’s Battery Storage and Flexibility Conference to discuss key questions and find solutions to challenges associated with delivering a net zero energy system:

• How much zero-carbon capacity such as renewables will be needed?
• How would we operate a system dominated by variable renewables?
• What happens when the wind doesn’t blow for a week?
• How much flexible generation capacity would we need, and what forms would this take?
• How can we achieve this whilst avoiding the types of blackout experienced on the 9^th August this year?

New analysis released today by Aurora Energy Research – the leading independent European energy market analytics company – tackles these questions.

Delivering a net-zero power system will require a significant expansion of low carbon generation capacity – which could come in the form of renewables, nuclear and Carbon Capture and Storage.

Aurora’s scenario for delivering net zero requires wind and solar capacity to increase by more than 100GW, from 33GW today to more than 140GW in 2050 – as well as 20GW of new nuclear and 3GW of CCS.

The variable nature of wind and solar output means that deploying renewables at this scale creates some significant challenges for the operation of the power system:

Firstly, the power system must always match demand and supply. This becomes harder in a system increasingly reliant on variable renewables. Short duration storage technologies such as batteries and pumped hydro can play a role by balancing renewables output over timescales of hours or days, and feeding power back into the grid when it is needed. Aurora identifies the need for up to 30GW of short-duration storage in 2050 in a net zero scenario to help balance renewables output.

Even with this storage in place, there would be ‘excess’ power which cannot be balanced out over hours or days – and if unused would need to be curtailed and lost. This could grow to as much as 185TWhs per year in 2050 as renewables capacity is increased. However, this excess generation could be used in other ways – for example to produce hydrogen for use in decarbonising heating, transport or industry.

Secondly, the variable output from renewables can change rapidly, and there is a need for backup capacities which can quickly ramp up and down to complement this. At present the biggest swings in residual demand are up to 5.4GWs in one half hour. However, this will grow over time as renewables become more dominant such that in 2050 we see swings in residual demand of 8.5GWs.

Thirdly, we need to ensure that a zero-carbon system always delivers reliable power. In a 2050 power system which is more dependent on wind, a critical consideration becomes how to manage a prolonger cold windless spell – or what is called a “Kalte Dunkelflaute” in German. Aurora’s analysis of historical data shows that extended windless spells happen for around 2 weeks per annum, when weekly wind output falls to less than half of that in an average week. Aurora estimates that over 20GW of backup capacity would be required to cater for this event.

Meeting these needs of the power system is straightforward in a world where this backup and flexibility is provided by gas generation (as it is currently). In a net zero system we need to consider alternative forms of long-duration zero-carbon capacity such as flow batteries, compressed or liquid air storage, hydrogen storage, or gas with CCS. However, although most of these options have been technically proven, they are not yet commercially viable under current market and policy conditions.

Delivering a net-zero power system will therefore require policy and market interventions – which could take a number of forms. In order to do this in the most cost-effective way, Aurora calls on Government, Ofgem, and the System Operator to follow the following three principles:

1. Price the externalities – a carbon tax or trading system is an efficient method to reduce carbon emissions.
2. Define the system needs – increasing renewables and removing thermal generation will create system operability challenges. These need to be clearly defined and tackled through transparent markets. Decentralisation of the power system means that some of these needs are location-specific and can best be solved with local flexibility markets.
3. Let the market decide – define the system needs and let the market provide the cheapest solutions. Pursue technology-agnostic policies and regulations based on system requirements, to drive competition and innovation.

Ana Barillas, Principal at Aurora Energy Research commented: “The UK has set an ambitious target to deliver a net zero economy by 2050. We estimate that over 100GWs of new wind and solar capacity will be required to deliver this in the power sector. This poses significant changes for operation of the power system – ensuring that the lights stay on despite the fluctuations in renewables output. Achieving this will require up to 30GW of short duration storage, and 20GW of longer duration firm capacity.”

Richard Howard, Research Director at Aurora Energy Research commented: “Whilst Extinction Rebellion occupies London’s streets to highlight the climate and ecological emergency, Aurora Energy Research has released analysis which highlights the scale of the challenges in getting to net zero. Balancing a net zero power system will require low carbon forms of flexibility which are not yet commercially viable to be delivered at a large scale. Government will need to intervene to bring these options to fruition – through carbon pricing, and technology-agnostic flexibility markets to drive competition and innovation.”

 At Aurora’s annual industry-leading event, Government and private sector experts will discuss the evolution of the power market towards a net zero system, the emerging technologies, and the financing challenges for flexible assets. Fintan Slye, National Grid SO’s Director – UK Systems Operator, will address the role of flexible assets in achieving net zero. Shadow Energy and Climate Change Minister Alan Whitehead MP will share Labour’s plan for power sector decarbonisation and flexibility.