Solar Heat Storage: Eliminating Gas Heating

This series of articles is a partnership between SPECIFIC, SUNRISE and the Active Building Centre. Our projects work with academic, industry and community partners in the UK and the Global South to research and develop solar technologies and to drive change in the construction industry.

While our projects each have distinct objectives and approaches, our shared message is simple: buildings don’t have to cost the Earth.

Our vision for transformation comes with many challenges across technical, political, social and economic norms. In this series we will share some of the work we’re doing to address each of these. This is the sixth blog of nine, and is an update on the research being done by our Thermochemical Storage Group.


The UK Government is banning gas boilers in new homes from 2025 in a bid to tackle emissions. We caught up with our Thermochemical Storage Group Lead, Dr Jon Elvins, to discuss how solar-powered technology can be used to heat buildings instead.

How does SPECIFIC’s thermochemical storage work contribute towards Climate Change target? 

At 37%, heating is the largest contributor of UK Greenhouse Gas emissions. We are working on an alternative method of heating buildings by using chemical salts such as calcium chloride. By capturing, storing and utilising heat within storage materials, we will be able to reduce overall demand, consequently reducing the overall CO2 impact, as well as the financial cost, of heating. 

Can you tell us about SPECIFIC’s work on full-scale demonstrators?

We’re looking at making the technology manufacturable and testing it on real buildings. SPECIFIC not only undertakes research but is quite advanced within heat storage demonstration, whereas other storage groups have been researching this from a purely scientific viewpoint.

Within the thermochemical storage field, our work is on a par with other groups for storage research and our capabilities are consistent with our peers. However, SPECIFIC is one of the only groups in Europe to undertake detailed work on demonstration and upscaling involving large volumes, while the majority of other groups concentrate on the research element of thermal storage at lab scale (i.e. single particles). Our large scale demonstrator at the SHED (Solar Heat Energy Demonstrator) in Margam, for instance, has a capacity of 800kg.  Since 2016, the whole industrial unit has been heated by solar energy, with an estimated energy saving of 75%. 

How does your fundamental research feed into this demonstration program?

We perform similar comparisons for thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) but our approach involves considering how this will work in a real-life scenario within a system – a building powered by solar energy.  

There are other groups looking at scale-up, but this is around different thermal storage configurations. For instance, one group is looking at liquid based systems, others are using similar apparatus but different material components – not SIM. SPECIFIC is the only group that incorporates demonstration at such large scale at present. 

We have a range of demonstrators: Ernie (20 – 30g), Bert (100 – 600g), Dalek charge rig (100 – 600g), Kenny (1 – 4kg), SHED (800kg) 

Colour-change SIM over a 16 hour period

What are the challenges involved with this technology?  

We are currently working on controlled heat release, as there are a number of variables, including the release profile from the salt, the power from the salt and the delivery of the fuel. When these factors work together consistently and in a predictable manner, this technology has the potential to be truly transformative. 

This type of technology is also currently overlooked by policy makers within the UK Government. Once its potential is recognised, we hope that funding is likely to increase, meaning we can work on larger-scale research and introduce it to buildings across the UK much sooner. 

What’s the next step? 

We are now focusing on the charge cycle, industrial waste heat recovery (working with local partners like Tata Steel), and upscaling further. Within the next year, the technology will be used to heat the air and water in our Active Classroom. This will provide us with data to assess the potential of using SIM (Salt in Matrix) in future Active Buildings. 

Watch the video below for more information on how SUNRISE, SPECIFIC, and the Active Building Centre work together to show how buildings can be designed differently:

Read other blogs in this series with SUNRISE and ABC:

Blog #1: Public involvement with a community in India: Q&A with Carol Maddock and Khushboo Ahire

Blog # 2: Designing Active Buildings

Blog #3: The Active Classroom: still providing insights and performing well

Blog #4: Translating ‘Active Buildings’ to India: Q&A with Arunavo Mukerjee

Blog #5: Active Buildings for Future Generations

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