The Future of Energy Systems and the Crucial Role of Long-Duration Power Storage

I recently had the pleasure of listening to a podcast featuring Michael Liebreich and Professor Sir Chris Llewellyn Smith, during which they delved into the future of energy systems and the crucial role of long-duration power storage. As an Emeritus professor of physics at the University of Oxford and former director general of CERN, Llewellyn Smith has been spearheading a study for the Royal Society, which examines the UK power system with a focus on long-duration power storage.

The study's goal was to identify the most cost-effective and reliable solutions for addressing the intermittent nature of wind and solar power. Initially, the study focused on a simplified case, excluding nuclear power, biomass, biogas, European interconnections, and North African wind and solar power. Llewellyn Smith shared the study's conclusion that storage is the most affordable option for ensuring a stable power supply in the UK.

Llewellyn Smith also touched on the balance between generation overcapacity and the need for storage. He mentioned that there is a flat minimum in energy provision costs, which lies between generating 25% more wind and solar power than the electricity demand and storage is 60% to 70%. This suggests that the optimal solution doesn't need to be precise, as long as it falls within this range. The study also considered worst-case scenarios, such as extended periods of low wind and solar generation. They emphasised the necessity of long-term energy storage options like hydrogen in salt caverns to maintain a consistent power supply during times of low wind or sun. Batteries, on the other hand, were deemed unsuitable for long-term storage due to their high costs and the need for frequent usage to make them economically viable.

Alternative methods of energy storage

The conversation also explored alternative storage methods, including demand response and pumped hydro. While demand response may help for short periods, it is inadequate for addressing longer periods of low power supply. Pumped hydro may be suitable in certain regions, such as the northeastern United States, but it is not a viable option for the UK. Overall, the discussion emphasised the significance of energy storage systems in maintaining power supply consistency and minimising costs in a renewable-energy-based system.

The speakers also examined the limitations of various energy storage solutions, including pumped hydro, flow batteries, compressed air storage, gravitational mechanical storage, and liquid air storage. They explained that pumped hydro's capacity in the UK is a thousand times smaller than what is needed. Flow batteries, while interesting, are currently too costly due to their reliance on vanadium, an expensive material. Gravitational mechanical storage, though potentially useful for rapid response storage, cannot provide the necessary amounts of energy.

Energy demand in the UK to double by 2050

The conversation then turned to the energy demand in the UK, which is expected to more than double by 2050 due to the electrification of transportation and heating. The exact increase in demand is uncertain, as it depends on factors such as the extent of electrification in heating and industry.

The speakers also discussed the cost of electricity generation using wind and solar, as well as the cost of storage. They estimated that the cost of wind and solar energy would be around ￡35 per MWh, with storage costs at ￡80 per MWh. The average cost of electricity in the system would be around ￡60 per MWh.

They also touched on the total investment needed for wind and solar energy generation and storage, estimating that it would cost around ￡100 billion for each. Additionally, the National Grid estimates that ￡100 billion would need to be invested in the grid by 2050.

The speakers highlighted that surplus electricity generated would be entirely used for hydrogen production. However, there might be concerns regarding curtailment and the location of the surplus electricity. They suggested that if there is cheap, surplus electricity available, new uses for it may emerge, such as drying biomass or producing hydrogen for other purposes.

Later the conversation revolved around the production and storage of hydrogen, as well as the economics involved in using electrolysers for hydrogen production. The researchers believe that placing electrolysers next to storage sites is the most cost-effective option, as transmitting electricity is cheaper than transmitting hydrogen.

The cost of hydrogen production is estimated to be between ￡52 and ￡90 per MWh, which is considered an upper bound. There is potential for cost reductions through various factors, such as using refurbished gas pipelines for transportation.

The conversation also touched upon the possibility of using nuclear energy for hydrogen production, but it was acknowledged that this is a complex issue. The use of Compressed Air Energy Storage (CAES) in conjunction with hydrogen was also discussed. Advanced CAES systems, which store heat in addition to air, could potentially lower the cost of hydrogen production by as much as 5%.

The challenges of energy storage

In this part of the conversation, Michael Liebreich and Professor Sir Chris Llewellyn Smith discussed the challenges of energy storage and its optimisation. They highlighted the importance of having multiple types of storage systems, such as compressed air and hydrogen, to balance their usage and minimise costs. However, the current market doesn't encourage investments in long-term storage solutions, which are crucial for a sustainable energy system. To address this issue, they proposed the idea of a central agency, similar to the Bank of England's monetary policy committee, to manage the buying and selling of power and facilitate collaboration between generators and storage operators.

The conversation also touched on the potential role of nuclear energy in this context, especially in terms of hydrogen production. Although they have not yet thoroughly explored this area, they are considering whether nuclear power could provide a viable alternative for hydrogen production, particularly with advanced reactor designs. Finally, they acknowledged the need for significant generation capacity to convert stored hydrogen back into electricity, which raises questions about the required scale of investment in new infrastructure.

Conclusion

In the final part of the conversation between Michael Liebreich and Professor Sir Chris Llewellyn Smith, they discussed the feasibility of a clean electric supply to decarbonise the UK economy. They emphasised that it can be done, with a maximum cost of ￡90 per MWh, which is more expensive than the historical costs of polluting power but still within a viable range. They also discussed the importance of hydrogen storage in salt caverns, mentioning that there is enough capacity in the UK to store 100 times the necessary amount of hydrogen. While there is limited global experience in constructing and operating such caverns, the experts believe that it is possible to build the required infrastructure. They concluded that a clean electric supply is achievable, but the implementation depends on effective policy and market incentives.