Why Heat Storage Matters for Industrial Decarbonization
As industries worldwide push toward decarbonization, one of the toughest challenges remains replacing fossil fuels used for high-temperature heat. Steel, cement, and chemical production often require over 1,000 °C — a range where electrification alone struggles to compete.
Thermal energy storage is now emerging as a crucial enabler of clean industrial heat. Two leading approaches stand out: brick-based heat batteries, capable of storing vast amounts of energy at extreme temperatures, and sand-based systems, which offer scalable and low-cost storage for long durations. Together, they could redefine how the world powers its industries.
Brick vs. Sand: Two Paths to Thermal Storage
While both brick and sand heat batteries store renewable electricity as heat, they differ in design and performance.
Brick systems reach up to 1,500 °C and use refractory ceramics that tolerate constant thermal cycling. They are ideal for producing industrial steam and process heat — direct replacements for fossil-fuel boilers.
Sand systems typically operate at 200–700 °C, targeting district heating and seasonal storage. Sand’s abundance and stability make it perfect for storing energy for days or weeks with minimal losses.
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In short, brick batteries deliver high-temperature precision and rapid response, while sand batteries provide low-cost, long-duration stability. Both complement each other in the global clean-heat transition.
Rondo Energy’s Brick Battery: High-Temperature Power in Ceramic Form
In October 2025, California-based Rondo Energy activated the world’s largest industrial heat battery — a 100 MWh system delivering zero-emission steam.
The Rondo Heat Battery (RHB100) stores energy in refractory bricks made from silicon, oxygen, and aluminum — Earth’s most common elements. Resistive wires, much like in a toaster, heat the bricks up to 1,500 °C, converting renewable electricity into usable industrial heat.
Efficiency tests showed >97 % round-trip efficiency, with charging at 20 MW AC and discharge at 7 MW thermal. A full charge from a nearby solar plant takes just six hours.
With an energy density of 250–400 kWh/m³ and an expected 40-year lifespan, Rondo’s design provides robust, maintenance-free performance. At a cost below 10 USD per kWh (th), thermal energy storage is around ten times cheaper per unit than lithium-ion batteries, making it ideal for large-scale decarbonization.
“At this cost level, thermal storage offers an order of magnitude cheaper energy capacity compared to electrochemical batteries, making it ideal for heavy industry,” notes Rondo’s team.
Rondo has ongoing projects in North America, Europe, Asia and Australia, and plans for a 300 MWh expansion highlight the scalability of brick-based heat storage.
Polar Night Energy’s Sand Battery: Long-Duration Heat for District Networks
In Finland, Polar Night Energy has developed another approach — storing heat in sand instead of ceramics.
Its 100 MWh sand battery, completed in summer 2025, is the largest of its kind. The system consists of an insulated steel silo filled with sand heated by renewable electricity and linked to a local district-heating network.
The sand reaches 500–700 °C, maintaining heat for weeks with <1 % loss per day and 90–95 % efficiency. When needed, the stored energy is released as hot air, warming water that circulates through the grid.
The pilot system in Kankaanpää, Finland, can reduce oil consumption by 70 % and cut CO₂ emissions by ~160 tons annually. With 1 MW charging power, a full charge takes roughly 100 hours, offering slow but steady energy buffering.
Simple materials — sand, steel, insulation — and local sourcing make this solution affordable and easy to scale.
“While slower to charge and discharge, sand batteries excel in storing large volumes of heat for days at minimal cost and loss,” Polar Night Energy states. “They act as seasonal buffers for renewable grids.”
Technical Comparison: Performance and Efficiency
| Parameter | Brick Battery (Rondo Energy) | Sand Battery (Polar Night Energy) |
|---|---|---|
| Temperature range | up to 1,500 °C | 500–700 °C |
| Round-trip efficiency | ~97 % | ~90–95 % |
| Energy density | 250–400 kWh/m³ | 80–120 kWh/m³ |
| Storage duration | Hours to days | Days to weeks |
| Heat-loss rate | < 2 % / day | < 1 % / day |
| Cost per kWh (th) | < 10 USD | ≈ 10 EUR |
| Typical use case | Industrial steam & process heat | District heating & seasonal storage |
| Design lifetime | > 40 years | > 20 years |
Global Impact: How Thermal Batteries Cut CO₂ Emissions
Brick and sand heat batteries are a major leap toward industrial decarbonization. Industrial heat makes up three-quarters of total industrial energy use and about 25 % of global energy consumption.
By turning variable renewable power into reliable thermal energy, these systems balance grids, reduce fossil-fuel reliance, and lower operational costs. Their 30–40-year lifetimes ensure decades of low-carbon performance.
The two technologies complement each other perfectly: brick for high-temperature steam in industry and sand for stable mid-temperature heat in cities. Together, they can help cut billions of tons of CO₂ annually and form a core part of future clean-energy infrastructure.
Conclusion: A Dual Future for Clean Industrial Heat
Brick and sand heat batteries mark a new era in sustainable energy. Though their materials and temperature ranges differ, both solve the same challenge — storing renewable energy efficiently and releasing it as heat when needed most.
From California’s factories to Finland’s heating grids, these innovations prove that the road to decarbonized heat is already being built. As adoption grows, the combination of brick precision and sand scalability may well become a cornerstone of the world’s clean-energy future.
Sources
- Rondo Energy – Rondo Heat Battery (RHB100) Product Overview
- Rondo Energy Press Release – World’s Largest Industrial Heat Battery (Oct 2025)
- Polar Night Energy – Sand Battery Technology Page
- PV Magazine – World’s Largest Sand Battery Commissioned in Finland (2025)
- Energy Storage News – 100 MWh Sand Battery in Commercial Operation (2025)
- Interesting Engineering – World’s Largest Sand Battery Cuts CO₂ Emissions by 70% (2025)
- Brattle Group Report – Thermal Batteries and Industrial Decarbonization (2023)
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Acknowledgment of AI
Content developed using AI technology, with final review and refinement by our human editors to ensure clarity, coherence, and accuracy.
