The UK and World Energy Storage Conference
Esme Butler Davies, one of our Graduate Consultants, presented her MEng research at the UK and World Energy Storage Conference last week. Researchers, students and industry experts from across the world joined to speak about the advancements and challenges the world faces as it moves towards Net Zero. Many new technologies and innovations within widely commercialised technologies were discussed, and it was a great opportunity to bridge the gap between industry and research.
Esme’s research investigated novel materials and methods for use in Aluminium-ion batteries, providing environmentally friendly alternatives to current widely-used components. Her poster won a prize in the Materials For Storage category at the UK and World Energy Storage Conference.
Read on to learn more about the necessity of energy storage as we transition to a Net Zero Grid.
Why do We Need Energy Storage?
Renewable energy generators such as solar panels and wind turbines produce electricity in a variable manner depending on the weather. As we increase our dependency on these types of technologies in the transition to Net Zero, we introduce variability into the Grid. Currently, fossil fuel generators are ramped up and down to match fluctuations in demand, but we are unable to operate renewables in this way.
This mismatch between supply and demand creates challenges for grid stability. On a sunny or windy day, we might generate more energy than we need, but at night or during calm periods, we might not have enough. Without an effective way to store surplus energy and release it when needed, the Grid has to rely on fossil fuel backups or curtail renewable generation.
Energy storage is therefore needed to store excess electricity and deliver it during peak times or outages. Energy storage technologies make our power system more resilient, flexible, and efficient and they are essential for the transition to Net Zero.
What Types of Energy Storage Are There?
Energy storage has been used for many years to help balance supply and demand in the UK Grid. Technologies are chosen for a specific application depending on response times and storage duration. Therefore, there are different technologies to suit different applications. The most well-established and widely used technologies are pumped hydro storage, and lithium-ion batteries.
Pumped Hydro Storage
Pumped hydro is the oldest and most widely used form of large-scale energy storage. Notable hydro plants in the UK are Dinorwig and Ffestiniog in North Wales.
Pumped hydro is operated by pumping water uphill into a reservoir when electricity is cheap. When power is required, water is released and flows back downhill through large turbines, generating electricity. The response time is within seconds, with some designs reaching full production capacity within 2 minutes.
Globally, pumped hydro accounts for over 90% of installed energy storage capacity. It is highly efficient, scalable, and capable of storing large capacities for long durations. However, it requires specific topography and significant capital investment, limiting where it can be deployed.
Lithium-Ion Batteries
Lithium-ion (Li-ion) batteries have become a dominant storage technology in the UK market in recent years due to falling costs and their widespread use in consumer electronics and electric vehicles. These batteries are compact, quick to respond, and relatively easy to deploy. The technology is ideal for short-duration storage such as balancing the grid over the duration of a few minutes to a few hours. Utility-scale Li-ion battery farms are now providing critical grid services such as frequency regulation and peak shaving.
However, Li-ion performance can degrade over time, and concerns remain around the environmental impact of mining and recycling materials such as cobalt and lithium. Safety concerns are also prevalent due to the flammability of the materials used design.
What New Energy Storage Technologies are Emerging?
Despite the current widespread use of Lithium-Ion batteries and pumped hydro storage, they cannot provide all of the storage needs required in a resilient grid. A broader mixture of storage technologies is required which can deliver power over different durations and at varying scales, such as seconds to weeks, and different scales and costs. The following technologies are becoming more popular as
Flow Batteries
Flow batteries use a liquid electrolyte which is stored externally to the cell stack. The electrolyte is circulated through the cell stack during charge to generate electricity via electrochemical reactions. This is different to the traditional Lithium-ion design, which stores energy in a single, self-contained cell and utilises solid-state materials as part of the electrochemical reaction.
One of the biggest advantages of this technology is the scalability; if a larger capacity is required, the tanks containing the electrolyte can just be increased. Flow batteries also have longer lifespans and can be fully discharged without degradation to the materials within. Vanadium redox and zinc-bromine are among the most mature types of flow batteries.
Flow batteries are promising for medium-duration applications, such as supporting the grid for between 4–12 hours. However, they are physically much larger and more costly than Li-ion.
Compressed Air Energy Storage (CAES)
CAES systems store energy by compressing air and storing it in underground caverns or high-pressure tanks. When electricity is required, the compressed air is heated, which causes it to expand through a turbine to generate power.
Traditional CAES systems use natural gas to reheat the air, reducing the environmental friendliness of the technology. Newer adiabatic CAES designs aim to capture and reuse the heat generated during compression, enabling zero-emission operation. Alternative fuels are also under consideration, such as biogas, biomass, or waste heat from industry.
CAES can offer large-scale, long-duration storage but requires suitable geological formations and complex engineering. Their response time is slower than pumped hydro (around 10 seconds), but the use of large geological formations means that they can store a high capacity of energy and discharge over a long period.
Flywheels
Flywheels store kinetic energy in a rotating mass. When energy is required, the rotational speed of the flywheel is slowed, and the kinetic energy is converted back into electricity.
Flywheels can respond in milliseconds, making them ideal for frequency regulation and grid stability. They also have a very long operational lifetime and require little maintenance. In the UK, there are some projects utilising flywheels for grid stabilisation in areas with high renewable penetration, as flywheels can provide the inertia, short circuit and voltage control services.
However, flywheels aren’t suited for long-duration storage. They typically store energy for seconds to a few minutes and are best used in combination with other technologies.
Thermal Energy Storage
Thermal systems store excess electricity as heat, often in materials such as molten salt, sand, or concrete. The stored heat can later be used to produce steam, which in turn drives turbines or provides industrial or district heating.
Thermal Energy Storage systems are particularly useful for integrating with concentrated solar power plants or industrial facilities. They provide a low-cost option which can store energy for hours to days.
Some companies are currently developing modular thermal storage systems for grid-scale applications.
Hydrogen Storage
Hydrogen is emerging as a flexible, long-duration energy storage solution which is particularly well-suited for seasonal storage and industrial applications. When surplus electricity is available, it can be used to power electrolysers that split water into hydrogen and oxygen. The hydrogen can then be stored in tanks or underground caverns and later converted back to electricity via fuel cells or turbines, or used directly as a clean fuel for transport, heating, or industry. While round-trip efficiency remains lower than other storage methods, the ability of Hydrogen to decouple energy generation from usage over the course of days, weeks, or even months makes it a key enabler of a fully decarbonised energy system.
With growing investment and policy support, hydrogen storage is expected to play an increasingly important role in the UK’s transition to Net Zero.
The UK and World Energy Storage Conference
Our Graduate Power Systems Consultant, Esme Butler Davies, recently attended the UK and World Energy Storage Conference at the University of Sheffield. It was positive to see a variety of different technologies under development, and a broad range of industrial names working alongside researchers to bring technologies to commercialisation. Researchers, students, educators and industry presented a variety of talks, seminars and presentations covering concept solutions to commercialised successes.
At the Conference, Esme presented her MEng research in the form of a poster. Her research investigated Aluminium-ion battery design and materials, which are currently under development.
Esme’s research utilised a Deep Eutectic Solvent for the electrolytes in the batteries, a material made up of two solid constituents which form a liquid at room temperature when mixed. The properties of the liquids are tuneable for specific applications, environmentally friendly, and easy to dispose of. Challenges of using such materials include their hygroscopicity (affinity to react with water), but the current methods for isolating such materials from air and moisture is expensive. Esme used a new method to isolate the electrolyte from air using a hydrocarbon layer. This provided a scalable and inexpensive method for electrolyte production without the need for costly specialist equipment.
Esme also reviewed the use of an environmentally friendly material to produce a graphite cathode. Traditionally, the binder solvent used in the production of many graphite cathodes (including in Li-ion) is a toxic and environmentally unfriendly chemical. Esme trialled the use of a binder which uses water, dramatically reducing the hazards associated with the current materials.
The materials produced using novel methods produced cyclable coin cells, proving that the technologies are charging and discharging. However, Aluminium-ion is still a long journey from commercialisation, and the battery mechanisms require further investigation to determine charge mechanisms and optimal materials.
Esme’s poster won a prize in the Materials For Storage category at the UK and World Energy Storage Conference.