A homeowner’s guide to phase change materials

What is a phase change material?

Phase change materials, often shortened to PCM, are materials that can store and release large amounts of energy by changing state. The easiest way to understand this is to think about water turning into ice, or ice melting back into water.

When water freezes, it stores energy. When ice melts, it absorbs heat. The change between these two states allows energy to be stored and released in a very efficient way.

PCM technology takes this idea much further. Instead of using water, modern phase change materials are specifically designed to melt and solidify at specific temperatures, allowing them to store heat exactly where it is needed.

This is the technology at the heart of Sunamp heat batteries.

How does the PCM inside a Sunamp heat battery work?

Inside a Sunamp Thermino heat battery is a specially developed phase change material called Plentigrade.

Unlike a traditional hot water cylinder that stores litres of hot water, a Sunamp stores energy within this solid material. When the heat battery is charged, electricity or another heat source (such as a heat pump) warms the Plentigrade material until it changes phase.

During this process, the material absorbs energy and stores it as latent heat.

The clever part is that the energy is stored while the material changes state, rather than simply raising the temperature of a large volume of water. This allows a significant amount of energy to be stored in a much smaller space.

When hot water is needed, the process reverses. The Plentigrade material changes back and releases the stored heat, transferring that energy to the water passing through the heat battery.

The result? Hot water on demand, without the need for a traditional cylinder full of stored water.

Why is Plentigrade different from simply heating water?

A traditional hot water cylinder relies on sensible heat storage. This means energy is stored by increasing the temperature of the water inside the tank.

The problem is that water takes up a lot of space, and as the cylinder sits there it slowly loses heat. This is why cylinders need insulation, and why they often require large airing cupboards or dedicated plant space.

A phase change material works differently. Most of the energy is stored during the point where the material changes state. This allows much more energy to be stored in a smaller volume.

For homeowners, this means a Sunamp heat battery can deliver the same purpose as a much larger cylinder while taking up significantly less space.

Why does Sunamp use phase change materials?

The aim behind Sunamp’s technology is to make hot water storage smaller, smarter and more efficient.

Many homes still rely on large hot water cylinders designed around older heating systems. These cylinders can be inconvenient in modern homes where space is limited, and they are not always ideal when paired with renewable technologies such as solar panels.

The Plentigrade PCM inside a Sunamp heat battery allows energy to be stored compactly. A Thermino unit can often replace a much larger cylinder, freeing up valuable storage space while still providing mains pressure hot water.

This makes heat batteries particularly useful for flats, smaller homes, extensions and properties where a traditional cylinder simply does not fit.

Can a Sunamp store energy from solar panels?

Yes. One of the biggest benefits of a heat battery is its ability to work alongside renewable energy.

Solar panels generate electricity during the day, but many households use most of their energy in the morning and the evening. Without storage, excess solar generation may be exported back to the grid.

A Sunamp can use surplus electricity to heat the Plentigrade material, effectively turning unused solar energy into stored hot water.

Instead of exporting excess energy for a small payment, homeowners can store it and use it later for showers, baths, and household hot water.

When combined with solar PV and battery storage, a Sunamp can become part of a wider energy system designed to maximise self-consumption.

Are phase change materials safe?

The PCM used inside Sunamp heat batteries has been developed specifically for energy storage applications. Unlike a traditional cylinder, a Sunamp does not store a large volume of hot water under pressure. The heat is stored within the Plentigrade material, with water heated as it passes through the unit.

This design also removes some of the concerns associated with storing large quantities of warm water for long periods of time.

The unit is sealed, compact, and designed for everyday domestic hot water use.

Do phase change materials last?

A key requirement for any energy storage technology is durability.

The Plentigrade material inside a Sunamp is designed to go through repeated cycles of charging and discharging. Each time the heat battery charges, the PCM melts and stores energy. When it discharges, it solidifies again and releases that energy.

This cycle can happen thousands of times over the life of the product.

Sunamp heat batteries are built for long-term domestic use, with warranties covering the storage core and heating components.

Are heat batteries the future of hot water?

As homes become more electric, the way we think about energy storage is changing.

For many years, storing energy meant storing fuel or heating large amounts of water. Modern homes now need smarter ways to use renewable electricity, cheaper overnight tariffs, and low carbon technologies.

Phase change materials offer a way to store heat efficiently without needing large tanks or complicated systems.

The Plentigrade technology inside Sunamp heat batteries shows how materials science can solve everyday problems. By storing energy in a compact thermal battery, homeowners can enjoy reliable hot water while making better use of renewable energy.

For anyone looking to reduce their reliance on gas, improve energy efficiency or make better use of solar power, a heat battery is an important part of the future home.