As the world transitions towards renewable energy sources such as wind and solar, effective energy storage systems (ESS) are essential to ensure grid stability and energy security.
Storage solutions enable surplus electricity generated during peak production periods to be used when generation is low. Various energy storage technologies exist, including battery energy storage systems (BESS), heat batteries, and alternative storage solutions. This article, by Haush, examines key storage technologies, leading companies, scalability, and cost comparisons.
Battery Energy Storage Systems (BESS)
BESS provide rapid-response energy storage and are widely deployed for balancing grid supply and demand.
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Lithium-Ion Batteries:
These are the dominant technology, known for their high energy density and decreasing costs. Tesla’s Megapack, used in large-scale grid applications, and CATL’s utility-scale batteries are widely deployed. These systems are ideal for pairing with solar and wind farms, providing short to medium-duration storage. -
Sodium-Ion Batteries:
Emerging as a cost-effective alternative to lithium-ion, sodium-ion batteries utilise more abundant materials. Companies like Natron Energy and CATL are developing this technology, which is particularly suited for stationary storage applications such as data centres and renewable energy integration. -
Iron-Air Batteries:
Form Energy is pioneering iron-air batteries, which provide long-duration storage of up to 100 hours. They operate using iron, water, and air, offering a low-cost solution for large-scale energy storage.
Heat Batteries and Thermal Energy Storage
Heat batteries store energy in the form of thermal energy, which can later be converted back into electricity or used directly for heating applications. These solutions are especially useful for decarbonising industrial processes and heating systems.
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Phase Change Material (PCM) Batteries:
Companies like Sunamp produce PCM batteries, which store heat using materials that melt and solidify at specific temperatures. These are well-suited for domestic heating applications and district heating systems. -
Molten Salt Batteries:
Utilised in concentrated solar power (CSP) plants, molten salt systems store heat generated by solar thermal collectors. This allows for electricity generation even when sunlight is unavailable. Companies such as Abengoa and SolarReserve have deployed these systems in large-scale CSP plants. -
Concrete, Brick and Sand Batteries:
These thermal storage systems use materials like concrete or sand to store heat at high temperatures. VTT Technical Research Centre in Finland is developing sand-based heat storage systems that can be used in industrial processes or district heating networks. Rondo’s Heat Battery stores heat the way it’s been stored for centuries. Millions of tons of this kind of brick have been used around the world for centuries to store high-temperature heat.
Alternative Energy Storage Technologies
Beyond batteries, other innovative energy storage technologies are being developed to enhance grid reliability:
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Liquid Air Energy Storage (LAES):
Highview Power is leading the development of LAES, where air is cooled to a liquid state and stored. When energy is needed, the liquid air is expanded to drive turbines and generate power. LAES offers long-duration storage and is scalable for grid applications. -
Pumped Hydro Storage:
This established technology stores energy by pumping water to a higher elevation and releasing it through turbines when electricity is needed. Scottish Power and EDF Energy operate major pumped hydro facilities in the UK.
Scalability and Deployment
Each storage technology has different scalability and deployment potential:
- Lithium-Ion and Sodium-Ion Batteries: These systems are modular, making them suitable for residential, commercial, and utility-scale applications.
- Heat Batteries: PCM, Brick and sand batteries are highly scalable, with applications ranging from home heating to industrial heat storage.
- Molten Salt and Pumped Hydro: These solutions are best suited for large-scale energy storage, particularly in renewable energy plants and grid stability projects.
- LAES and Iron-Air Batteries: Suitable for large-scale applications, these technologies are emerging as viable solutions for long-duration storage.
Cost Comparison (CapEx and OpEx)
The capital expenditure (CapEx) and operational expenditure (OpEx) vary across storage technologies:
- Lithium-Ion Batteries: CapEx is declining, with current costs around £150-£200/kWh for utility-scale storage. However, raw material costs and supply chain constraints can impact prices.
- Sodium-Ion Batteries: Expected to be more cost-effective than lithium-ion, with estimated costs around £100-£150/kWh once commercial production scales up.
- Iron-Air Batteries: Projected CapEx of around £50/kWh, making them a low-cost solution for long-duration storage.
- Heat Batteries: PCM batteries have a lower CapEx (£50-£100/kWh thermal), while molten salt storage costs around £30-£60/kWh thermal. Sand and concrete storage solutions are even more cost-effective for large-scale applications.
- Pumped Hydro and LAES: Pumped hydro has high upfront costs but low OpEx, with a lifetime of over 50 years. LAES has an estimated CapEx of £100-£200/kWh but benefits from using readily available materials.
Cost Comparison (CapEx and OpEx)
A diverse mix of energy storage technologies is essential to support the transition to renewable energy. BESS, heat batteries, and alternative storage solutions each offer unique advantages in terms of cost, scalability, and deployment potential. As energy storage technologies advance, they will play a crucial role in ensuring the stability and reliability of the grid in a renewable-powered future.
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