New Phase-change Materials for Domestic Heat Storage, Low Carbon Heating and Reduced Fuel Poverty

Research by Professor Colin Pulham and group has solved long-standing stability issues associated with phase-change materials based on salt hydrates, enabling the commercialisation of the world’s first residential heat batteries.

The challenge: enabling heat storage technology for lower carbon heating

With over twice as much heat and cooling energy consumed in the world as electricity, technologies that enhance efficiency and enable better use of renewable energy in this crucial sector have an important role to play in the fight against global warming. Realising that storage of thermal energy is key to this, Sunamp Ltd set out to develop heat battery technology that could store energy from any source as heat and release it on demand to provide space heating and hot water. Their technology proposed innovative use of phase change materials (PCMs) which store and release heat as they change phase. However, the company quickly found that available PCMs failed after only a few heating and cooling cycles.

New phase change materials for reliable and long-lasting heat storage

Seeking research input to tackle this problem, Sunamp was introduced via Interface to Professor Colin Pulham, who brought years of expertise in crystallisation science1,2. Research by Pulham and his group, including use of the Diamond Light Source to interrogate the evolution of PCMs during temperature cycling, enabled the development of new PCM formulations that retain their high energy density and stability over more than 40,000 cycles.

Heat storage battery in a cupboard

The world’s first commercially viable residential heat batteries

With these new formulations at their core, Sunamp have brought to market the world’s first commercially viable residential thermal energy storage systems. Their UniQ range of heat batteries increase efficiency and maximise use of locally generated renewable energy and off-peak electricity, thereby reducing use of fossil energy sources and thus carbon emissions. Simply by reducing heat loss compared to traditional hot water cylinders, Sunamp heat batteries installed so far have reduced CO2 emissions by 4.6 kilotonnes. Heat batteries also save households money, with proven savings of up to 75% on utility bills.

Installations in social housing across central Scotland have confirmed the financial savings and increase in comfort for residents and demonstrated the impact that heat batteries can have in tackling fuel poverty. Resident testimony confirms the improvement to their quality of life: "It saves a lot of money, put it that way. You’re getting your hot water for free. Before that, this house was a really cold, cold house…It makes a lovely difference.”

Housing association resident and heat battery recipient Joan, who has noted valuable savings and increased comfort
Happy resident with a Sunamp heat battery charged from solar PV.

Sunamp is growing quickly as heat battery sales ramp up across the UK and beyond and their technology, supported by new PCM formulations developed by the Pulham group, is quickly being extended into new applications to provide emissions savings and environmental benefits – in the automotive, commercial and industrial sectors, and for domestic cooling.

Student Opportunities

Ongoing close collaboration between the Pulham group and Sunamp provides exciting opportunities for School of Chemistry students at both undergraduate and postgraduate levels. Through practical experience, students learn about heat-storage technologies and how their discoveries in the laboratory can be commercialised to contribute to the company’s success. Recent projects have included the evaluation and optimisation of new PCMs for both heating and cooling applications, and the development of high-temperature solid-solid PCMs for thermal management of vehicles aimed at improving fuel economy and reducing emissions. 

Related Publications

  1. I.D.H. Oswald, A. Hamilton, C. Hall, W.G. Marshall, T.J. Prior and C.R. Pulham, “In-situ characterization of elusive salt hydrates - the crystal structures of the heptahydrate and octahydrate of sodium sulfate”, J. Am. Chem. Soc., 2008, 130, 17795-17800. DOI: 10.1021/ja805429m.
  2. I.D.H. Oswald, I. Chataigner, S. Elphick, F.P.A. Fabbiani, A.R. Lennie, J. Maddaluno, W.G. Marshall, T.J. Prior, C.R. Pulham and R.I. Smith, “Putting pressure on elusive polymorphs and solvates”, CrystEngComm, 2009, 11, 359-366. DOI: 10.1039/B814471K.
  3. D.E. Oliver, A.J. Bissell, X. Liu, C.C. Tang and C.R. Pulham, “Crystallisation studies of sodium acetate trihydrate – suppression of incongruent melting and sub-cooling to produce a reliable, high-performance phase-change material”, CrystEngComm, 2021, 23, 700-706. DOI: 10.1039/D0CE01454K.

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