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Executive Summary

The report assesses the need and best methods for large-scale electricity storage in Great Britain (GB) to support a net-zero electricity system powered by wind and solar energy. It concludes that GB can meet future electricity demand using high levels of wind and solar generation, supplemented by storage, at costs competitive with low-carbon alternatives. Hydrogen storage in underground salt caverns is the leading candidate, while other technologies show promise. The analysis highlights the importance of long-term storage for variability and the need for policy reforms to incentivize investment.

Major Conclusions

• Large-scale storage, primarily hydrogen-based, is essential to complement wind and solar energy, which vary significantly.
• The cost of electricity is lower with high wind/solar penetration supported by storage, compared to alternatives like nuclear or gas with carbon capture.
• Hundreds of TWh of storage capacity will be required by 2050, far exceeding current levels.
• Long-duration storage is least cost-effective using hydrogen in salt caverns, though other technologies can reduce costs.
• Grid modernization, demand management, and market reforms are crucial for integration.

Analysis of Electricity Demand, Supply, and Storage Need

Electricity demand in GB by 2050 is projected at around 570 TWh/year. Wind and solar are likely to dominate due to cost-efficiency, with a 70/30 mix preferred for minimizing storage needs. Weather variability necessitates storing tens of TWh for extended periods, often requiring hydrogen storage. Accurate modeling requires multi-decadal weather data to avoid underestimating long-term risks.

Storage Technologies

Storage is categorized by response time:

1. Minutes to hours: Lithium-ion batteries for short-term grid services (e.g., frequency regulation).
2. Days to weeks/months: Advanced compressed air energy storage (ACAES), liquid air energy storage, thermochemical storage (early stage), and pumped hydro (marginal impact). ACAES complements hydrogen well.
3. Long-term (years): Hydrogen in salt caverns (high potential), ammonia, and synthetic fuels (costlier; better for transport).

Hydrogen and Ammonia:

• Hydrogen (LHV storage) is cheaper and can be stored underground in GB (East Yorkshire, Cheshire, Wessex), though site availability is limited.
• Ammonia is a gas storage contender but more costly without hydrogen infrastructure; global usage has declined since peak industrialization.

Grid-Level and Other Storage:

• Grid operators need timely scheduling protocols for efficient storage mix (e.g., hydrogen and ACAES combination lowers costs by ~5%).
• Long-duration storage is essential; batteries and flow batteries add flexibility but higher methane/leasing risks.
• Heat storage (e.g., water pits) can reduce electrical demand.

Cost Considerations

• Hydrogen storage dominates long-term costs, but efficiencies compensate for lower round-trip values.
• Total system costs (wind/solar + storage + transmission + grid services) can range from £52 to £92/MWh in 2050.
• Adding baseload (nuclear or gas+CCS) may increase costs unless marginal.
• Storage costs are highly dependent on scale, with salt caverns showing the best potential but requiring further R&D/commercialization.

Market and Governance Issues

• Existing markets may not support storage investment due to long-term idleness; reforms like regulated asset bases or contracts for difference are needed.
• Weather variability and demand spikes require demand-side responses or imports.
• Innovation in storage scheduling (e.g., using weather forecasts) and international collaboration could lower costs.

Further Steps and Opportunities

• Demonstrate large-scale hydrogen storage now and integrate with grid technologies.
• Prioritize R&D for PEM electrolysers, iridium reduction, and flow batteries.
• Explore novel storage like thermochemical systems and hydrogen-fueled engines.
• Policy must address critical minerals, funding, and deployment.
• Maintain flexibility for climate change advancements and ensure learning-by-doing reduces costs.

References

The Royal Society maintains a glossary and detailed supplementary material. Key studies include analyses by Barrett et al. (2021) on multi-year storage and IEA reports on hydrogen and storage technologies.