#	Pagina
attuale pagina	/open-h2020/projects/200150/results.html

Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - BCOOL (Barocaloric materials for energy-efficient solid-state cooling)

Teaser

Summary

Cooling is essential for food and drinks, medicine, electronics and thermal comfort. Thermal changes due to pressure-driven phase transitions in fluids have long been used in vapour compression systems to achieve continuous refrigeration and air conditioning, but their energy efficiency is relatively low, and the working fluids that are employed harm the environment when released to the atmosphere. More recently, the discovery of large thermal changes due to pressure-driven phase transitions in magnetic solids has led to suggestions for environmentally friendly solid-state cooling applications. However, for this new cooling technology to succeed, it is still necessary to find suitable barocaloric materials that satisfy the demanding requirements set by applications, namely very large thermal changes in inexpensive materials that occur near room temperature in response to small applied pressures.

I aim at developing new barocaloric materials by exploiting phase transitions in non-magnetic solids whose structural and thermal properties are strongly coupled. These materials are normally made from cheap abundant elements, and display very large latent heats and volume changes at structural phase transitions, which make them ideal candidates to exhibit extremely large barocaloric effects that outperform those observed in expensive barocaloric magnetic materials, and that match applications needs.

My unique approach combines i) materials science to identify materials with outstanding barocaloric performance, ii) advanced experimental techniques to explore and exploit these novel materials, iii) materials engineering to create new composite materials with enhanced barocaloric properties, and iv) fabrication of barocaloric devices, using insight gained from modelling of materials and device parameters. If successful, my ambitious strategy will culminate in revolutionary solid-state cooling devices that are environmentally friendly and energy efficient.

Work performed

During this reporting period, I have recruited and trained a team of highly motivated Ph.D. students and research associates. My research team has synthesised a number of novel barocaloric materials, developed a number of bespoke advanced experimental techniques that permit direct measurements of barocaloric effects, and studied the barocaloric performance of some of the synthesised compounds and composites produced.

My research team has studied barocaloric effects in a number of non-magnetic solids that are made from cheap abundant elements. We found giant reversible barocaloric effects at room temperature that outperform those observed in the best barocaloric magnetic materials, and those predicted in inferior barocaloric ferroelectric oxides. Our exciting discoveries have led to a patent that has been filled by Cambridge Enterprise, and that has attracted attention across the largest refrigeration companies in Europe and the US.

In particular:

We found giant barocaloric effects driven using hydrostatic pressure in the superionic conductor silver iodide. Application of high pressure to this compound leads to the melting of the cation sublattice, yielding a large volume change and a large latent heat. The barocaloric performance in this compound varies only slowly on changing the operating temperature, as required for effective operation in prospective heat pumps. This work has led to a publication in Nature Communications [Nature Communications 8, 1851 (2017)].

We studied barocaloric effects in a number of hybrid organic-inorganic perovskites, via temperature and pressure dependent calorimetry and thermometry. These hybrid perovskites show giant barocaloric effects near room temperature, using order-of-magnitude smaller applied pressures than the magnetic materials, ferroelectric materials, and superionic conductors above. This work has led to a publication in Journal of Materials Chemistry C [Journal Materials Chemistry C 6, 9867 (2018)].

Final results

During this reporting period of the action, my research team has made very good progress on all the activities planned, and we have discovered a number of non-magnetic barocaloric materials that outperform the state of the art. From now until the end of the project, I expect to improve even more the barocaloric performance of our materials and composites, in terms of maximum pressure-driven isothermal entropy changes and pressure-driven adiabatic temperatura changes, in terms of minimum driving pressures, and in terms of low cost. I also expect to demonstrate envirornmentally friendly cooling by exploiting our materials in prototype cooling devices.