Brook Lang on Thermal Energy Storage

As renewable energy adoption accelerates, the challenge of storing energy when the sun is not shining or the wind is not blowing has become increasingly urgent. While lithium-ion batteries dominate headlines, another powerful solution is gaining traction: thermal energy storage. By capturing and storing heat or cold for later use, thermal storage systems are emerging as cost-effective and scalable “grid batteries” that support a more resilient and flexible energy system.

WHAT IS THERMAL ENERGY STORAGE?

Thermal energy storage involves storing energy in the form of heat or cold, rather than electricity. This stored thermal energy can be used directly for heating or cooling, or converted back into electricity when needed. Because heating and cooling account for a large share of global energy demand, thermal storage offers an efficient way to balance supply and demand while reducing strain on electrical grids.

Unlike chemical batteries, thermal storage systems often rely on abundant, low-cost materials such as water, salt, concrete, or specialized phase change materials, making them particularly attractive for large-scale applications.

SENSIBLE HEAT STORAGE

The simplest form of thermal storage is sensible heat, where materials store energy by changing temperature. Water tanks, concrete blocks, and molten-salt systems absorb excess heat and release it later when demand rises.

Molten salt storage is widely used in concentrated solar power plants, allowing them to generate electricity even after sunset. This technology enables renewable energy to behave more like traditional baseload power, improving reliability and grid stability.

LATENT HEAT AND PHASE CHANGE MATERIALS

More advanced systems use latent heat storage, which relies on phase change materials that absorb and release energy as they change state, such as from solid to liquid. These materials can store large amounts of energy at constant temperatures, making them ideal for applications where precise temperature control is critical.

Phase change materials are increasingly used in building materials, refrigeration systems, and industrial processes, improving energy efficiency while reducing peak electricity demand.

COLD THERMAL ENERGY STORAGE

Thermal storage is not limited to heat. Cold thermal energy storage systems produce ice or chilled water during off-peak hours when electricity is cheaper or cleaner. This stored cold is then used for air conditioning during peak demand periods, significantly reducing grid load.

Ice storage is already being deployed in commercial buildings, data centers, and district cooling systems, demonstrating how thermal storage can shift energy use without compromising comfort or performance.

SUPPORTING RENEWABLE INTEGRATION AND GRID RESILIENCE

Thermal energy storage plays a critical role in integrating renewable energy sources. By absorbing excess solar or wind power and releasing it later, these systems smooth out fluctuations and reduce the need for fossil fuel-based backup generation.

Additionally, thermal storage enhances grid resilience by providing backup heating, cooling, and power during outages or extreme weather events, supporting energy security at both building and community levels.

A COMPLEMENT TO BATTERY STORAGE

Rather than competing with batteries, thermal energy storage complements them. While batteries excel at fast-response electrical needs, thermal systems handle long-duration storage more economically, especially for heating and cooling applications.

THE FUTURE OF GRID-SCALE ENERGY STORAGE

As energy systems evolve, thermal energy storage is emerging as a practical and versatile solution for decarbonization. By transforming heat and cold into valuable energy assets, these technologies expand storage options beyond electricity and unlock new pathways to a cleaner, more resilient grid.

Thermal energy storage proves that the future of energy is not just about electrons; it is also about intelligently managing heat and cold to power a sustainable world.