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A No Nonsense Guide to Thermal Stores

A No Nonsense Guide to Thermal Stores

Thermal stores serve as a reservoir for heat, capturing excess energy when available and releasing it when needed.

This technology offers a versatile means of capturing otherwise wasted thermal energy from renewable energy sources, such as solar panels or heating devices, like boilers.

Thermal stores absorb excess heat for reuse, which helps balance out supply and demand in naturally fluctuating energy installations.

For example, if your solar batteries run out, you can temporarily extract thermal energy from your thermal stores, which you can use to heat water for radiators, showers, taps, etc.

This guide delves into thermal stores, how they work, and how they can complement industrial energy systems.

What Is a Thermal Store?

A thermal store is a specialised thermal energy storage unit designed to accumulate and retain heat energy from various sources.

Heat sources absorbed by thermal stores can include renewable energy installations like solar collectors and wind turbines and more conventional heat-generating systems like boilers.

Essentially, the thermal store takes excess heat, which would otherwise be wasted and stores it for later use. The store absorbs heat and can be ‘extracted’ for later use – somewhat acting as a thermal energy ‘piggy bank.’

By storing surplus thermal energy when an excess is available, a thermal store provides a robust mechanism for energy retrieval during periods of increased demand or decreased supply.

  • A thermal store serves as a "heat bank," collecting and storing heat so that you can use it exactly when you need it, mitigating waste and inefficiency.
  • Thermal store systems can integrate with a wide range of heat sources, such as solar energy, wind power, and traditional gas or electric boilers.
  • By storing heat when it's abundantly available, a thermal store can release it when a primary energy source might not be as reliable, like cloudy days for solar energy.
  • By balancing out supply and demand, thermal stores can make industrial heating systems more stable and efficient, ultimately saving money and reducing energy waste.

What are Thermal Stores used for?

Domestic Applications

In residential environments, thermal stores are ideal for maintaining hot water availability and heating.

They are often integrated with renewable energy systems, such as solar panels, to store excess thermal energy and make it available when required.

By storing excess energy, thermal stores ensure a consistent hot water and heat supply, thereby enhancing overall household energy efficiency and resilience against fluctuations in external energy supply.

Industrial Applications

In industrial contexts, thermal stores find utility in many applications, including but not limited to process heating (e.g. manufacturing processes which require heat), waste heat recovery, and cogeneration systems (which produce both heat and electricity).

Thermal stores can act as a buffer to minimise the operational strain on boilers and other heating systems, enhancing the operational lifespan of these assets.

Also, thermal stores are useful for processes requiring stable and continuous thermal energy supply, such as pharmaceutical, food processing, and chemical industries.

How do Thermal Stores work?

Sensible Heat

Sensible heat storage is the most common type of heat storage. It involves raising the temperature of a storage medium – typically water, but sometimes other materials like sand or bricks – to store energy.

The heat is recovered by releasing the medium's stored energy, typically through heat exchangers.

One key advantage of sensible heat storage is its relative simplicity, proven effectiveness and relatively low cost.

Latent Heat

Latent heat storage employs phase change materials (PCMs) that absorb or release thermal energy when they undergo a phase change, such as from solid to liquid or vice versa.

Because these materials can store large amounts of heat energy with minimal temperature changes, they’re ideal for applications requiring high-energy density storage.

Common materials used include paraffin waxes and certain types of salts. The primary advantage of latent heat storage systems is their higher energy storage density than the aforementioned sensible heat storage systems.


More experimental thermochemical heat storage methods are based on exothermic and endothermic chemical reactions to store and release heat.

Unlike sensible and latent heat storage, thermochemical storage can, in principle, offer almost limitless storage times as the chemical substances involved can remain stable for extensive periods.

Thermal stores offer a flexible means to capture excess thermal energy from systems and store it for later use. This complements renewable energy systems that are vulnerable to a high level of supply and demand fluctuation.

Thermal store technology has accelerated with advancements in latent heat and thermochemical stores.

Sensible heat stores have also become more efficient, offering domestic and business users another way to tap into renewable energy and the savings that come with it.

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