Energy storage will play a crucial role in the future clean energy system.
The integration of clean energy sources like wind, solar and hydrogen poses a unique challenge: matching supply and demand. By storing surplus renewable energy, available for dispatch during energy deficits, we could achieve a secure, stable grid.
This article explores the various facets of energy storage. We’ll cover the different models of energy storage, the UK’s forecasted capacity, and innovative systems like Storelectric’s CAES.
The types of energy storage
Energy storage technologies span a diverse spectrum, each catering to specific duration and scalability requirements. There is a large scale of duration for these solutions. Put simply, that means there’s lots of variation in how long a storage technology can maintain its full capacity power output.
Very Short-Duration Storage (Up to four hours of energy discharge).
This includes technologies like flywheels and super-capacitors, ideal for rapid response and stabilising the grid. These can generate synthetic inertia, which is crucial for black-starting the grid during a nationwide power outage.
Short-Duration Storage (Four to twelve hours of energy discharge).
Battery Energy Storage Systems (BESS) such as lithium-ion, dominate this segment. These offer storage durations from minutes to several hours, crucial for balancing supply and demand fluctuations.
Long-Duration Storage (Anything more than 12 hours of energy discharge).
This includes technologies like compressed air energy storage, pumped hydroelectric storage and thermal storage systems. These can store energy for extended periods, ranging from several hours to days or even months. As a result, these systems are essential for meeting sustained energy demands during periods of low renewable generation.
The UK’s current energy storage landscape
RenewableUK published data in January 2024 underscoring the UK’s rapid advancement in energy storage infrastructure. Their EnergyPulse energy storage report showed a 68.6% increase in the total pipeline of battery projects over the previous year. This increase saw battery capacity grow from 50.3GW to 84.8GW, which represents:
- 3.5GW of operational capacity,
- 3.8GW under construction,
- 24.5GW consented,
- 27.4GW submitted in the planning system,
- 25.7GW at an early development stage.
This rapid expansion is supported by a trend of larger storage project sizes, with the average scheme size increasing to 80MW. A decade ago, the average was just 2MW, so this growth represents significant development. This signals high investor confidence and the importance of connecting viable storage solutions to the grid.
The new Labour-led UK Government has recognised the tremendous financial benefits of energy storage, projecting savings of up to £10 billion per year by 2050. They intend to utilise the new National Wealth Fund to spur public and private investment in storage. In doing so the UK will hopefully see a drastic increase in the LDES storage capacity. Along with supporting UK climate targets, this policy shift is of enormous economic benefit to the UK. The energy storage market is projected to create 24,000 jobs and continue to foster investment in British industry.
Why renewables need energy storage
Renewable energy sources are intermittent by nature. They rely on specific environmental conditions to generate power – sun, clear skies and high wind. This means there are periods of surplus generation and of deficit. Energy storage mitigates this intermittency issue by storing excess renewable energy during peak production times, subsequently releasing it during periods of high demand or low generation. This capability enhances grid stability, reduces reliance on fossil fuel backup generation, and optimises renewable energy utilisation.
The threat of climate change, increased reliance on renewable energy sources, and the rapid adoption of electric vehicles all pose challenges to existing electricity systems globally. Energy storage has become an essential part of the new electricity mix, providing flexible power supply, reducing costs, and ensuring reliable services for consumers. For a low-carbon future, the electricity system will need storage at all points and across a vast range of discharge times, from less than one-tenth of a second to over a year.
Storelectric’s CAES model: Innovation in large scale, long duration storage
Among the innovative approaches to long-duration energy storage (LDES), Storelectric’s adiabatic Green CAES™ stands out. This technology leverages compressed air stored in underground salt caverns, utilising surplus electricity to compress air during periods of low demand. When energy demand rises, the stored air is released to drive turbines and generate electricity, all without the need for additional fuel combustion. This approach offers high efficiency, scalability, and cost-effectiveness compared to traditional energy storage solutions like pumped hydro.
Storelectric’s Green CAES™ uses a thermal energy management system to recover heat from the compression process and reuse it in the power cycle. This results in higher efficiency than other adiabatic CAES technologies and allows for construction in a wider range of locations due to flexibility in cavern pressures. The technology is cost-effective, reliable, and can be constructed from readily available equipment.
CAES has a proven track record, with operational systems since 1978 in Huntorf, Germany, and 1991 in McIntosh, Alabama, USA. However, these models rely on gas fired power stations, which Storelectric’s innovation eliminates the need for, reducing emissions and improving overall efficiency.
Storelectric’s Green CAES™ vs. batteries
Perhaps two of the most popular energy storage models are CAES and Batteries, with both solutions touted as the solution to the energy crisis. While batteries are a popular choice for energy storage, CAES offers several advantages for large-scale, long-duration storage needs.
Cost and efficiency
Grid-connected batteries can be expensive upfront and are not very efficient. If you double a battery’s size, the cost can rise by about 85%. Extending the life of a battery can increase the cost by 75-85%. In comparison, extending the duration of a CAES system is more cost-effective, only raising the price by about 15-30%. As batteries scale up, so do their costs. On the other hand, CAES plants benefit from increased scale, reducing capital and operational costs as they expand.
Multitasking abilities
One of the main strengths of CAES is its ability to deliver multiple services concurrently. These include:
- Balancing services,
- Ancillary services,
- Inertial services,
- Reactive power
- Load, voltage and frequency regulation,
- Black start capability without needing dedicated plants.
This multi-tasking ability makes CAES a more versatile and efficient option for long-term energy storage.
Batteries offer synthetic inertia, which is helpful for recovery from failures but less effective in preventing them. Real inertia from CAES provides continuous stability to the grid, maintaining frequency and phase control. CAES plants produce these services as a by-product of regular operation, adding to their efficiency and cost-effectiveness.
Lifespan and safety
CAES systems can have a lifespan of up to 150 years with minimal maintenance requirements, while battery systems typically last 8-10 years and degrade rapidly under heavy use. CAES also avoids the risks associated with exploding and burning batteries, which have a history of causing fires and explosions in grid-connected installations around the world.
So which is better?
Compressed Air Energy Storage offers compelling advantages over batteries for large-scale, long-duration storage needs. This is not to say that there isn’t a place for batteries in the storage landscape; We need a diverse range of technologies to suit an equally diverse range of storage needs. Batteries and CAES should co-exist for different functions. By taking a nuanced approach to energy storage, we can enable secure renewable power across every sector in the UK.
How energy storage models can work together
Different energy storage technologies complement each other within the grid ecosystem. For instance, while batteries excel in rapid-response applications, CAES systems like Storelectric’s Green CAES™ provide reliable, long-duration storage suitable for seasonal energy demand fluctuations. This complementary relationship ensures a balanced and resilient energy infrastructure capable of meeting diverse energy needs across various timescales. No single set of technologies can handle the vast range of discharge times required by the grid. Instead, very short, short, and long duration energy storage solutions can work cooperatively.
The most widely used storage model is long-duration storage, primarily from pumped hydro plants. However, these facilities are often costly, take years to build, and lack location flexibility. In contrast, lithium-ion batteries dominate the shorter-duration market but are not ideal for stationary power applications requiring sustained delivery. We could mitigate the unique benefits and downfalls of different storage models by employing them together, in different areas of the same system to build a cohesive, secure energy landscape.
The UK’s energy storage forecast
The UK plans to add more than 25GWh of new grid-scale capacity by 2031. This forecast includes significant investments in co-located solar PV and storage projects, expected to comprise around 20% of planned capacity.
The National Grid ESO predicts that by 2050, the UK will need at least 50GW of storage power capacity and just under 200GWh of capacity. This is definitely an ambitious forcast, but one the UK is capable of achieving by employing a cohesive, multifaceted storage system.
The energy storage market in the UK is growing at an annual rate of 15%, driven by the increasing need for flexible, reliable power supply solutions. Operational capacity is projected to rise from 4.6GW/5.9GWh to 7.4GW/11.6GWh by the end of 2024. This growth is supported by a surge in submitted and approved planning applications, reflecting the high levels of investor confidence and the strategic importance of energy storage in the UK’s energy transition.
Looking forward
As we transition to a renewable energy future, the importance of energy storage cannot be overstated. The ability to store and dispatch energy when required is vital for maintaining grid stability and ensuring a reliable supply. The UK’s projected expansion in storage capacity, supported by governmental policies and innovative technologies like Storelectric’s CAES, provides a solution to renewable intermittency, meaning we could conceivably achieve Labour’s goal of a net zero grid by 2030. By integrating a variety of storage technologies, from short to long-duration systems, we can create a resilient, efficient, and sustainable energy grid. This multifaceted approach not only supports our climate targets but also drives economic growth and job creation, making energy storage the key to a greener future.
