Could Super-Heated Sand and Salt in Thermal Batteries Be a Better Energy Storage Solution Than Lithium-Ion?
Storing power is one of the biggest challenges in our shift to clean energy. While sources like the sun and wind provide enormous amounts of electricity, they are not always available. The sun sets, and the wind calms. To create a reliable power grid that runs on clean energy 24/7, we need a way to save that power for when it’s needed most. For years, lithium-ion batteries have been the go-to solution, but they come with their own set of problems. A different, older, and surprisingly simple idea is now making a comeback: the thermal battery.
A thermal battery operates on a straightforward principle: it turns electricity into heat and stores that heat in simple, abundant materials. When you need the electricity back, the system uses the stored heat to generate power. It’s a technology that could fundamentally change how we manage energy for our homes, industries, and entire power grids.
How Does a Thermal Battery Work?
Think of a thermal battery like a giant, insulated box filled with a material that can hold a lot of heat for a long time. The process begins when there is an excess of electricity, for instance, from solar panels on a sunny afternoon.
Charging (Heating Up)
The surplus electricity is directed into the thermal battery, where it powers heating elements, much like the coils in a toaster or an electric stove. These elements heat up a storage medium, which can be something as simple and inexpensive as bricks, sand, or blocks of graphite. Some advanced systems use molten salts or silicon, which can reach incredibly high temperatures—in some cases, over 1,800 degrees Celsius—and hold that heat for hours or even days with very little loss.
Storing (Keeping it Hot)
The core of the battery is a heavily insulated container that keeps the storage medium hot. This insulation is crucial for efficiency, as it prevents the heat from escaping. The ability to store this intense heat for a long duration is what makes thermal batteries so promising for grid stability.
Discharging (Getting Power Out)
When electricity is needed, the stored heat is put to work. It can either be used directly as heat for industrial processes like making steel or cement, or it can be converted back into electricity. This conversion is often done using a heat engine, a device that uses a temperature difference to create motion, which then drives a generator to produce electricity.
The Growing Need for Large-Scale Energy Storage
The world is rapidly building more wind and solar farms to reduce its reliance on fossil fuels. This is excellent for the climate, but it creates a new challenge for grid operators. Unlike a traditional power plant that can be turned on or off at will, renewable energy sources are variable. This inconsistency requires a buffer—a way to store massive amounts of energy to balance supply and demand.
The market for this kind of storage is expanding at a remarkable pace. In the first quarter of 2024 alone, 993 megawatts (MW) of new grid-scale storage solutions were installed, an 84% increase from the previous year. Energy leaders predict that by 2030, the United States will need 98 gigawatts (GW) of large-scale battery storage, a massive leap from just 1 GW in 2019. The global grid-scale battery market was valued at over $9.7 billion in 2025 and is projected to grow at a compound annual growth rate of 26.5% through 2035.
Thermal Batteries Versus Lithium-Ion: A Comparison
Today, most grid-scale energy storage relies on lithium-ion batteries, the same technology that powers smartphones and electric cars. However, as the demand for storage grows, the limitations of lithium-ion are becoming more apparent, creating an opening for alternatives like thermal batteries.
Cost and Materials
Thermal batteries are built from cheap, abundant, and globally available materials like graphite, sand, and salt. Lithium-ion batteries, on the other hand, depend on materials like lithium and cobalt, which are expensive, have volatile supply chains, and often come with significant environmental and social costs associated with their mining. This makes thermal batteries a potentially much cheaper solution for storing huge amounts of energy.
Lifespan and Durability
A thermal battery can operate for decades with very little degradation. The materials inside are simply being heated and cooled, a process they can endure for thousands of cycles without losing much performance. Lithium-ion batteries have a shorter lifespan and lose their ability to hold a full charge over time, often needing replacement after a few thousand cycles.
Safety
Lithium-ion batteries contain flammable materials and, in rare cases, can experience a dangerous event called thermal runaway, leading to fires that are difficult to extinguish. Thermal batteries do not have this chemical fire risk. While they operate at very high temperatures, this heat is contained within a heavily engineered, safe system.
Long-Duration Storage
This is where thermal batteries truly stand out. While lithium-ion batteries are excellent for short-term storage (typically up to 4 hours), thermal batteries are designed to store energy for much longer periods—from 10 hours to several days. This makes them ideal for covering multiday periods of low wind or cloudy weather.
Environmental Impact and Recycling: The materials used in many thermal batteries, like graphite and silicon, are easily and fully recyclable. Recycling lithium-ion batteries is a complex and expensive process that is still in its early stages of development.
Antora Energy: A Startup Heating Up the Industry
The potential of thermal batteries has attracted significant investment. In the last year, venture capital funding for thermal battery startups exceeded $309 million. One of the leading companies in this space is Antora Energy, a startup based in California.
Antora’s system stores energy as heat in blocks of solid carbon, which are heated to glowing-hot temperatures in an insulated container. When power is needed, doors open to expose the hot blocks, releasing intense light. This light is captured by highly efficient photovoltaic (PV) cells—similar to solar panels—that convert the light directly into electricity.
The company has seen rapid growth and validation:
- Funding: Antora raised $150 million in a 2024 Series B funding round from major investors, including Bill Gates’s Breakthrough Energy Ventures and Decarbonization Partners, bringing its total funding to over $244 million.
- Expansion: The company has opened a large-scale manufacturing facility in San Jose, California, and has grown to over 200 employees.
- Government Support: Antora is benefiting from favorable government policies like the Inflation Reduction Act, which provides tax credits and funding for clean energy technologies. This support helps reduce the risk for industrial customers to adopt this new solution.
Antora is initially focusing on decarbonizing heavy industry, providing a zero-emissions alternative to burning fossil fuels for process heat. Its success demonstrates a clear path for thermal batteries to become a mainstream energy storage solution.
What’s Next for Energy Storage?
As the world continues to build a clean energy economy, the demand for reliable, long-duration, and cost-effective energy storage will only grow. While lithium-ion batteries will remain a vital part of the puzzle, especially for short-duration needs and electric vehicles, they cannot solve the entire problem alone.
Concerns about the cost, safety, and sustainability of lithium-ion are driving innovation in other technologies. Thermal batteries are emerging as a powerful contender, alongside other solutions like green hydrogen, iron-ion batteries, and sodium-ion batteries. With their simple design, cheap materials, and ability to store energy for long periods, thermal batteries are poised to play a crucial role in powering a stable and sustainable energy future.