What thermal energy storage is – and how does it work?

08 September 2020 | OVO Energy

Technology has come on in leaps and bounds when it comes to renewable energy for the home. And energy storage is a very important part of this. It means we can grab hold of renewable energy whenever it’s available, and then store it for when we need it. That makes energy storage ideal for those of you keen to start creating the sustainable home of your dreams!

Sustainable heating for your home

Why is storing energy important?

As we get more and more renewable energy generation into the national grid (like wind turbines and solar panels), there’s more opportunities to capture that energy when it's available, and store it – ready for when we need to use it at home.

There are lots of ways to store energy: electric batteries, electric vehicles, large hydro-power… but another option is to store it as heat for our radiators and showers.

And storing energy as heat means renewables (like solar panels and heat pumps, for example) become an even better option. Especially when you think that most of the energy we need for our homes (over 80%) is for heating and hot water1.

Let’s take a closer look at how thermal energy storage works.

What is thermal energy storage?

Thermal energy storage (AKA heat storage) covers all the different ways of storing energy, so it can be used for heating or hot water when it’s needed. 

For example, if you have solar panels for a lot of the time they might make more electricity than you can use in an average day. Storing this extra power for heating, is a brilliant way to maximise that power.

Live in a home where the heating system doesn’t give you enough heat on demand? Or where heat or electricity is produced when you don’t actually need any? Thermal storage is a really great way to deal with these problems – helping to keep costs down, making your carbon footprint lighter, and just generally making life at home easier (and cosier!) 

This kind of storage is compatible with many types of heating systems and renewable sources of energy: whether it’s gas or oil boilers, solar panels, heat pumps, biomass boilers, or wood-pellet stoves. They all generate energy that you can then store – with the right equipment. 

Thermal energy systems – what’s available?

Thermal stores are like your standard hot-water tank (or cylinder) in a regular heating system. Mostly there to give you hot water for showers and baths. Some heating systems also have ‘buffers’, which are small stores of hot water, giving you instant hot water while you wait for the boiler to kick in.

Heat batteries are a pretty new technology for home heat storage. And we’re huge fans of this tech! They can be used to store heat from a range of different sources to give you heating and hot water. Plus, these neat batteries take up less space than a hot water tank – giving you more space in the airing cupboard. Or even letting you turn that space into something more useful! They can also store heat for longer, and don’t lose heat to their surroundings – like water tanks do. 

How thermal energy systems work

Thermal stores (such as hot water tanks) work by storing heat in the form of hot water – this heat will last for hours.

Thermal stores can get most of their heat from one source – just like a standard hot-water tank connected to a gas boiler. But did you know they can have multiple sources of heat too? For example an immersion heater, as well as (or instead of) a boiler.

Immersion heaters run directly from electricity, so you can connect different types of renewable systems, as well as a conventional boiler, to your hot water tanks. Using these, you can make sure you’ve always got heat when you need it – and keep the carbon emissions down!

Heat batteries use something called ‘latent heat’ to store their energy as heat. It’s quite techy, but here’s how it works: heat or electrical energy is used to convert a ‘phase change material’ (PCM) from one state to another (in other words, from solid to liquid). This captures a lot of energy. 

When comparing it to a cylinder, there is much less heat loss from a heat battery, thanks to the insulation being significantly better.  This means PCM heat batteries store more energy in a smaller space, and lose less energy from heat loss – because the stored temperature is lower. Sounds complex, but this is all good news! 

When you need to get the heat back out again, the process is reversed (converting the PCM from liquid back to solid) causing a release of heat. Which can be used to heat your water – genius!

Thermal energy solutions store hot water for your home

There are a few other bonuses here too. Because heat batteries don’t store lots of water, there is no risk of legionella (a bacteria that likes to grow in some hot water tanks if they aren’t regularly heated to very high temperatures). And if you ever get a leak – there’s no large store of water waiting to flood your home. Phew!

Who offers thermal energy storage solutions?

Sunamp is a specialist in thermal energy storage solutions. And it’s got the technology down to a tee. As front runners in this area, Sunamp is definitely one to consider when you update your heating system. 

Sunamp Heat Batteries are currently the most compact thermal storage technology out there. They’re the ultimate space saver. And they give you heating and hot water brilliantly, while fitting in with your preferred heating controls.

Environmentally friendly, safe, and superbly efficient, the fact they’re so compact is an extra bonus. Wherever you’ve got a bit of room, they can be hidden away – like under the kitchen sink or stairs. Plus, there’s no need for a separate hot water storage tank.

They’re super versatile. They can replace a standard hot water tank, work with existing boilers or mains electricity, and help you find new ways to save energy and money – by linking up with a variety of renewable energy sources.

Sunamp UniQ:

Sunamp UniQ

The UniQ range of heat batteries can heat up all types of homes, depending on how much hot water you need. They’re all stackable (yup, that’s one on top of the other!) and have an A+ ERP rating (ERP is an Energy Related Product rating – which helps you identify energy efficiency).

Here’s the UniQ range. See how much energy each battery provides, and the size of tank they can replace:

  • UniQ 3: 3.5kWh, replaces 70L cylinder
  • UniQ 6: 7kWh, replaces 140L cylinder
  • UniQ 9: 10.5kWh, replaces 210L cylinder
  • UniQ 12: 14kWh, replaces 280L cylinder

Here are some amazing Sunamp benefits:

  • Make best use of your renewable systems, for electricity and heat 

  • Reduce CO2 emissions from your home

  • Lighter and smaller than thermal stores

  • Cheaper than a similar capacity electric battery

  • Super easy to fit, low maintenance, and they have a lifespan of over 40,000 cycles (that’s about 50+ years of average use!)2

  • Plus, Sunamp is the first, and only, heat battery maker in the world to be awarded A Grade RAL Certification (the independent quality mark, and only global standard for Phase Change Material (PCM) and PCM products).2 Find out more about Sunamp

The benefits of thermal energy systems

Considering all the new tech available today, we think that thermal energy storage is one of the best solutions for your home. 

Making your mind up: things to consider 

Here’s a bit of homework you can do, to help your installer get the best solution for your home. Have a think about:

  • How many heat sources do you want to feed into your thermal store?
  • How many people live in your home?
  • How big is your home?
  • How is heat distributed around your home?  
  • Do you want to use smart technology to track your energy usage?

Join our Zero Carbon Heating Trial!

Zero Carbon Heating Trial

We want to show that kicking carbon out of our homes starts by changing the way we heat them. So why not join our pioneering Zero Carbon Heating trial

The way we heat our homes counts for 15%1 of the UK’s carbon emissions. Our trial aims to change this. And you could get the chance to see for yourself how effectively Sunamp energy storage solutions work with air source heat pumps! 3

If you’d like to get involved, we’ll install up to £15,000 worth of brand new tech in your home (including a Sunamp UniQ battery), so you can see it all first hand. Interested? Find out more about OVO Zero Carbon Heating Trial.

1 This figure comes from this report by the Committee on Climate Change and its Adaptation Committee.

2 RAL Certification provides an audited test for long term performance of PCM. Sunamp’s award follows a rigorous test programme, which involved heating and cooling the batteries for 10,000 cycles to demonstrate the material’s performance levels and working life. 

3 Not all systems will have Sunamp installed in this trial. This depends on what is best for your particular home and is subject to an on site survey.

For more information on Sunamp visit their website.