Plentigrade phase change technology

Storing energy as heat and releasing it when, and where, it's needed

Sunamp thermal batteries are energy-saving thermal stores containing Plentigrade: our high-performance phase change materials (PCMs) that deliver heating or cooling reliably, safely and efficiently.

Plentigrade, with its perpetual phase changing ability, is at the core of our products.

Our breakthrough technology was created in collaboration with the University of Edinburgh, ranked among the top 20 universities in the world, and the UK’s national synchrotron particle accelerator, Diamond Light Source. To find out more about the chemistry behind Plentigrade, read our blog.

The 'Sustained with Plentigrade' quality mark on our products assures performance, efficiency, safety, and reliability.

Sustained with Plentigrade

Plentigrade is the remarkable PCM inside our thermal batteries which absorbs and releases thermal energy during a melting and freezing process in a similar way to the gel in a pocket handwarmer.

The PCM uses latent heat – the energy needed to break the PCM’s crystal structure to change it from solid to liquid – to store energy on melting to a liquid and to release energy at a controllable, constant temperature on freezing to a solid.

Plentigrade guarantees high energy output and an almost unlimited lifespan, yet its composition remains unchanged.

Its best-in-class reliability is underscored by internationally recognised certification. Sunamp also holds multiple patents for Plentigrade PCMs.

Stores 4 to 10x more energy than conventional materials

Cost reducing

The unique Plentigrade formula stores thermal energy at a lower cost and higher efficiency that other battery technologies.

Greater efficiency

Our flagship Plentigrade P58 material stores up to four times more energy than water which means our Thermino heat batteries are smaller than traditional hot water cylinders.

Industry leaders

Others have tried, but no one before has succeeded in perfecting our combination of exceptional long-life, recyclability, safety and high energy density.

Across a range of temperatures

We can change the trigger temperature when Plentigrade melts and freezes.

This means Sunamp batteries can be used for cold, ambient or hot temperature applications.
For example:

  • -22°F (-30°C) for refrigeration
  • 41°F (5°C) for cooling such as cold chain storage
  • 136°F (58°C) for domestic hot water and space heating
  • 244°F (118°C) for high temperature >176°F (80°C) hot water applications such as sterilization


Sunamp is the only thermal battery manufacturer in the world to be awarded RAL Certification, the only global standard for Phase Change Material and PCM products.

The award confirms the performance of our flagship Plentigrade P58 material with no noticeable degradation to 10,000 cycles in the Thermino product – the equivalent of over 13 years of daily use.

Award from the UK’s prestigious Royal Society of Chemistry

Sunamp won the 2022 Industry-Academia Collaboration Award for our successful and innovative partnership with The Edinburgh University School of Chemistry. 

This work led to the commercial development of our world-leading thermal storage technology using novel formulations of phase change materials.

Learn more about the chemistry behind Plentigrade

Dr David Oliver, Sunamp’s materials development manager, explains what a phase change material is and why it is important.