Thermal Batteries: The Next Frontier in Low-Carbon Energy Storage

As businesses and governments race to decarbonise, much of the focus has been on electrification and battery storage — but not all energy is electrical. In fact, around 50% of global final energy consumption is used for heat. That’s where thermal batteries come in — a lesser-known, but rapidly emerging energy storage solution that could reshape how we heat our buildings, run our industrial processes, and balance energy supply.

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What Are Thermal Batteries?

A thermal battery is a device that stores energy in the form of heat rather than electricity. This stored heat can later be released and used directly, or in some cases, converted back to electricity.

Unlike chemical batteries, thermal batteries use materials that absorb and retain heat—such as molten salts, sand, concrete, or specially engineered bricks. These materials can reach very high temperatures and hold that thermal energy for hours or even days with minimal loss.

Think of them as a giant thermal flask — but instead of coffee, they store renewable heat.

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How Do They Work?

At a basic level:

1. Charging phase: Excess energy (typically from renewables like solar or wind) is used to heat up a storage medium.
2. Storage phase: The material retains the heat, often at temperatures exceeding 500°C.
3. Discharge phase: The stored heat is released as needed — to warm buildings, drive industrial processes, or power a heat engine to generate electricity.

Some systems use phase change materials (PCMs), which absorb large amounts of heat as they melt or solidify, improving storage density.

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Real-World Applications

Thermal batteries aren’t just theoretical. Here’s where they’re being deployed:

• Industrial heat processes: Sectors like steel, cement, glass, and food production need consistent high-temperature heat. Thermal batteries can deliver it while cutting fossil fuel use.
• District heating systems: Urban thermal networks can use thermal batteries to balance supply and demand, storing heat from solar thermal or biomass for use during peak times.
• Commercial buildings: Paired with solar PV or off-peak electricity, they can preheat water or air to reduce grid demand during the day.
• Grid balancing: Some startups are developing hybrid systems that store thermal energy and then reconvert it to electricity to help stabilise grids.

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Why This Matters for Energy Efficiency

• Lower conversion losses: If you need heat, storing it directly (rather than converting it to electricity and back again) is much more efficient.
• Grid optimisation: Thermal batteries help shift energy consumption away from peak times, reducing grid stress and infrastructure costs.
• Cost-effective: Materials like sand or bricks are cheap and abundant, making thermal batteries more scalable than lithium-ion in some applications.
• Decarbonisation enabler: They unlock the use of intermittent renewables for sectors that can’t easily electrify.

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Final Thoughts

Thermal batteries may not have the high-tech glamour of lithium or hydrogen, but they offer something just as valuable: practical, scalable, and efficient energy storage for heat. For many businesses, especially in manufacturing or commercial property, they could become a vital tool in the net-zero toolkit.

If you’re a business with high heat demand or looking at on-site energy optimisation, it might be time to explore how thermal storage could work for you.

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