Net zero will need in excess of 100 GW of wind and solar

Given the current administration’s aversion to onshore wind, unless policy changes, most of that additional wind power would have to come from offshore wind.

The energy analyst said up to 30 GW of short-duration storage will be required to help balance renewables output and a solution will be needed to manage a ‘Kalte Dunkelflaute’ – or cold windless spell – where wind output can drop significantly for a week or more. Aurora estimates that 20 GW+ of firm backup capacity will be required in 2050 to solve this system challenge.

Aurora also believes that excess renewables generation could reach 185 TWh in 2050 and this could be used to produce hydrogen to decarbonise heating, transport or industry.

In June 2019, former UK Prime Minister Theresa May implemented legislation that aims to see the UK eradicate its net contribution to climate change by 2050. The Prime Minister claimed the legislation will mean the UK is ‘on track’ to become the first G7 country to legislate for net zero emissions.

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

“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,” Aurora said.

“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 30 GW 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 185 TWhs per year in 2050 as renewables capacity is increased,” said the energy analyst. “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 5.4 GW 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 8.5 GW.

“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 prolonged cold windless spell.

“Aurora’s analysis of historical data shows that extended windless spells happen for around two weeks per annum, when weekly wind output falls to less than half of that in an average week. Aurora estimates that over 20 GW 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.”

Given the above, Aurora believes that 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:

• Price the externalities – a carbon tax or trading system is an efficient method to reduce carbon emissions.
• 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.
• 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.

Aurora principal Ana Barillas said, “We estimate that net zero requires more than over 100 GW of new wind and solar capacity. This poses significant changes for operation of the power system – ensuring the lights stay on despite the fluctuations in renewables output. Achieving this will require up to 30 GW of short duration storage, and 20 GW of longer duration firm capacity.”