What materials are commonly used in thermal energy storage?

Thermal energy storage (TES) involves storing thermal energy for later use, and it relies on a variety of materials to achieve this. These materials can be categorized into three main types: sensible heat storage, latent heat storage, and thermochemical storage.

Types of Storage Materials

Sensible Heat Storage

This type of storage involves storing thermal energy by heating or cooling a solid or liquid material. Common materials include:

• Water: Used in hot water tanks, which are common in UK homes and commercial settings.
• Rocks, concrete, and bricks: These solid materials are often used in underground thermal energy storage systems.
• Rock or gravel mixed with water: Often used in pit storage systems for seasonal thermal storage.

Latent Heat Storage

Latent heat storage uses phase change materials (PCMs), which absorb and release thermal energy as they change phase from solid to liquid or vice versa. Examples of PCMs include:

• Salt hydrates: These are effective for storing heat over a wide temperature range.
• PCM products: Used in niche applications, such as storing PV-generated electricity as heat or integrating into building materials.

Thermochemical Storage

Thermochemical materials store energy through reversible chemical reactions. Common materials include:

• Metal chlorides, metal hydrides, and metal oxides: These materials offer high energy density and can be used for inter-seasonal storage.

Real-World Applications in the UK

In the UK, thermal energy storage is increasingly important for supporting decarbonization efforts. Key applications include:

• Electric storage heaters: Found in approximately 1.8 million homes, these use off-peak electricity to store heat for later use.
• Hot water tanks: Used in over 11 million UK homes for intra-day heat storage.
• District heating systems: Large hot water tanks are used in these systems to provide heat to multiple buildings.

Practical Advice

When considering thermal energy storage for your home or business, keep in mind the following points:

Pros

• Energy Efficiency: TES can significantly reduce energy costs by using off-peak energy or surplus energy from renewable sources.
• Flexibility: Different materials allow for various storage durations and temperature ranges.

Cons

• Initial Cost: Setting up a thermal energy storage system can be expensive, especially for advanced technologies.
• Space Requirements: Depending on the system, significant space might be needed, especially for larger tanks or underground systems.

Common Mistakes

• Inadequate Sizing: Incorrectly sizing the storage system can lead to inefficient operation or insufficient capacity.
• Lack of Maintenance: Regular maintenance is crucial to ensure the longevity and efficiency of the system.

For homeowners and small businesses looking to implement thermal energy storage, it's important to assess specific needs, available space, and local regulations before selecting a suitable material or system. Advances in technology and policy support are expected to further improve the adoption and effectiveness of TES solutions in the UK.