Chilling with electrocaloric ceramics: comprehensive investigation towards ultimate power, temperature Span and Heat pump coefficient of performance – CooliSH

Conventional refrigeration systems use refrigerant gases, whose choice results from a trade-off between efficiency, safety, availability, and environmental impacts. In particular, the third-generation refrigerants (hydrofluorocarbons or HFCs) is a significant greenhouse gases contributor (GHG), alone responsible for approximately 3% of global GHG emissions. Even if new low-GHG alternatives were implemented, these gases cannot be perfectly contained in refrigeration systems, generating gas leaks into the atmosphere, and its long-term effects remain to be quantified.
Caloric materials behave like solid refrigerants and could represent an alternative approach—based on different physical principles—leading to high-efficiency systems without the drawbacks mentioned above. In this context, electrocaloric materials, as well as magnetocaloric and elastocaloric materials, have led to recent very promising experimental proofs of concept. However, on the one hand, the scarcity of materials (rare earth elements, for example) could pose a major problem; on the other hand, this refrigeration alternative is still at a very early stage of development, and many fundamental questions remain.
The CooliSH proposal aims to study the use of electrocaloric materials for refrigeration based on lead-free formulations using abundant elements. The project focuses in particular on three identified scientific challenges: (i) the complex problem of heat and mass transport, (ii) electrical energy management, and (iii) the difficulties of scaling up and integrating the functions required for refrigeration into a holistic approach.
The first point refers to the thermodynamic cycles involved in electrocaloric refrigeration. The underlying physical processes are not yet fully understood, leading to empirical development by academic teams. Furthermore, there is a need to improve heat exchange to enable devices with higher cooling power. The plan is to study how to break axial flows to improve liquid-solid heat exchange, using various means such as obstacles or surface structuring. The CooliSH project plans to develop innovative solutions for improved heat exchange, validated by modeling and experimental visualization of flows and thermal gradients.
The second point addresses the problem holistically and seeks solutions to control the charging/discharging processes of electrocaloric ceramics, taking into account scale effects. This last aspect exploits the advantage of actuating electrocaloric materials with an electrical voltage, which requires the development of new strategies adapted to highly nonlinear capacitive behavior, strategies of different nature depending on the power ranges considered. Electrocaloric materials behave like electrical capacitors, converting a fraction of the supplied electrical energy into heat. Recovering remaining electrical energy is a key process in achieving the highest refrigeration power/power consumption ratio, surpassing current systems.
Finally, beyond advances in each of the aforementioned disciplines, the CooliSH project aims to develop an experimental proof of concept based on lead-free materials, integrating innovative solutions for controlling heat transfer and electrical energy management, with expected performance well beyond the state of the art in terms of refrigeration power and refrigeration temperature.