How phase-change materials are saving lives

The Dulas solar-powered direct-drive vaccine fridge uses phase-change materials to store vaccines more effectively, helping save human lives.

The Dulas solar-powered direct-drive vaccine fridge uses phase-change materials to store vaccines more effectively, helping save human lives.

By Jason Deign

Phase-change materials (PCMs) are boldly going into an energy storage realm where even the most modern battery technologies have failed to deliver: saving lives.

Dulas, a Welsh renewable energy technology company, is using PCMs in place of batteries as an essential component of solar-powered direct-drive refrigerators for off-grid vaccine storage in developing countries.

On Monday the company announced a contract to supply 345 of its VC200 fridges to health and aid agencies working in Yemen, Sierra Leone and Nigeria.

The company said the deal represented “a significant expansion” of its partnerships with the World Health Organisation (WHO), the United Nations Children’s Fund (UNICEF) and the Institute of Human Virology in Nigeria.

Dulas will be sending 60 fridges to the Institute of Human Virology, 143 to the WHO in Yemen and 142 to UNICEF in Sierra Leone. “There is the potential for further orders in the near future,” said the company. 
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Study points to PCM breakthrough

Research from TermoFluids and the Tesconsol consortium may provide a breakthrough in the use of phase-change material for thermal energy storage in concentrated solar power plants. Photo credit: KIC InnoEnergy

Research from TermoFluids and the Tesconsol consortium may result in the breakthrough of phase-change material for thermal energy storage in CSP plants. Photo: KIC InnoEnergy

The case for using phase-change materials (PCMs) for thermal energy storage is being bolstered through research using a modelling technique out this year.

The technique, developed by a team in Catalonia, Spain, has uncovered a PCM tank approach that could theoretically allow up to 74% of stored thermal energy to be returned from storage.

It might also reduce the amount of storage material needed in solar thermal plants by 32% compared to traditional two-tank molten salt systems, CSP Today reports.

The approach, called multi-layered solid PCM (MLSPCM), works by using two PCM layers separated vertically by a layer of filler materials such as cheap, readily available granite or quartzite.

The filler keeps the top and bottom PCM layers close to their optimum discharging and charging temperatures, respectively. Overall, the amount of PCM material needed would be much less than in a PCM-only setup, which should help reduce costs.

And since each PCM layer is kept close to its optimum charge or discharge temperature, the efficiency of the system is increased.
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Solar thermal energy storage loses its way

Does phase-change material storage have advantages over molten salt thermal energy storage for a concentrated solar power plant? Photo credit: Crescent Dunes Solar Energy Project, SolarReserve

Is phase-change material storage better than molten salt thermal energy storage for a concentrated solar power plant? Photo: Crescent Dunes Solar Energy Project, SolarReserve

Too much salt is not just bad for your health. It could also harm the likelihood of thermal energy storage (TES) cost reduction across the entire concentrated solar power (CSP) industry.

Right now, molten salt TES is seen as critical in justifying the high cost of CSP versus other renewable energy sources, such as solar PV or wind.

TES allows CSP, or solar thermal energy, to deliver stable, round-the-clock power, which is more valuable to grid operators than the intermittent generation provided by renewable alternatives.

But it is just possible that a growing preference for molten salt among CSP developers could hamper the chances of adopting more efficient and cost-effective types of TES.
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