ELECTROCALORICS - Laboratory for refrigeration and district energy

Direct Characterization of Electrocaloric and Magnetocaloric Responses in Multicaloric Composite Films

admin — Wed, 01 Jul 2026 05:57:47 +0000

Researchers from the Jožef Stefan Institute, the University of Ljubljana, the University of Barcelona, IFW-Dresden and collaborating institutions have published the article Direct observation of room-temperature electrocaloric and magnetocaloric responses in multicaloric composite films.

The study combines the electrocaloric ceramic PMN-10PT with the magnetocaloric La-Fe-Si-Co (LFSC) alloy. Using Powder Aerosol Deposition (PAD), the team fabricated dense multicaloric composite films approximately 5 μm thick. PAD enables the fabrication of functional thick films entirely at room temperature and offers an attractive route for integrating advanced caloric materials into future cooling devices.
A key achievement of the work is the direct characterization of both electrocaloric and magnetocaloric responses in the same multicaloric composite film at room temperature. The composite films exhibited an approximately 32 % higher electrocaloric temperature change compared to pure PMN-10PT films. The enhancement is attributed to Maxwell–Wagner polarization effects induced by the embedded magnetocaloric particles.
In addition, the magnetocaloric response was directly measured in the same composite films, experimentally confirming their multicaloric functionality and demonstrating the feasibility of combining electrocaloric and magnetocaloric effects within a single aerosol-deposited structure.
The results provide new insights into the development of multifunctional caloric materials and demonstrate the potential of multicaloric composite films for future solid-state cooling and micro-cooling technologies targeting electronics, sensors, and other miniaturized systems.

Link: https://www.sciencedirect.com/science/article/pii/S0955221926004607

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Thermag XI 2026: A successful gathering of the solid-state thermal community

admin — Tue, 16 Jun 2026 06:01:05 +0000

The 11th IIR Conference on Solid-State Cooling, Heating and Energy Harvesting – Thermag XI, held from 7-11 June in Ljubljana, Slovenia, has concluded successfully.

This milestone event brought together researchers, engineers, and industry experts from around the world to exchange the latest advances in solid-state cooling, heating, and energy harvesting. Thermag XI provided a unique forum for sharing cutting-edge research on functional materials, emerging concepts, and their integration into next-generation energy systems.

The presentations reflected a wide range of research activities, from fundamental studies and materials development to device prototyping, modelling, and practical applications that contribute to more sustainable energy technologies. The conference proceedings will be published soon on the IIR website: https://iifiir.org/en/conference-proceedings.

We sincerely thank all authors for their submissions and the reviewers for their valuable contributions. Special appreciation goes to the keynote speakers, session chairs, scientific committee, and organizing team whose efforts made the event possible. We also gratefully acknowledge the support of the International Institute of Refrigeration (IIR), the Slovenian Energy Association (SZE), the Chinese Association of Refrigeration (CAR), the Faculty of Mechanical Engineering at the University of Ljubljana, and all sponsors and partners.

The following topics were presented:

THE CONVENTIONAL AND ROTATING MAGNETOCALORIC EFFECT OF A GADOLINIUM PARALLEL PLATE MAGNETIC REGENERATOR – INFLUENCE OF GEOMETRY (Rafael Almeida, Rodrigo Kiefe, Darja Gačnik, Ricardo M. C. Pinto, João O. Silva, Katja Klinar, Henrique Souza, Gonçalo Oliveira, João S. Amaral, Andrej Kitanovski, João H. Belo)

IMPLEMENTATION AND VALIDATION OF AN ACTIVE ELECTROCALORIC REGENERATOR COMPONENT IN TCC BUILDER (Grega Belšak, Izak Oberčkal Pluško, Katja Vozel, Andrej Kitanovski, Markys Cain, Katja Klinar)

NUMERICAL STUDY ON THE FREQUENCY DEPENDENCE OF THE DIRECT MAGNETOCALORIC EFFECT OF GADOLINIUM FILM (Zhonghao Chang, Jorge Revuelta-Losada, Erika Fontana, Nora Dempsey, Katja Klinar, Andrej Kitanovski, Jia Yan Law, Victorino Franco)

VALIDATION OF THE NUMERICAL SIMULATION OF A HIGH-FREQUENCY REGENERATIVE THERMOMAGNETIC GENERATOR HYPEREG (Kamyar Dobakhti, Katja Klinar, Urban Tomc, Jure Javornik, Andrej Kitanovski)

FINITE ELEMENT MODELING AND OPTIMIZATION OF A MAGNETIC FIELD SOURCE FOR THERMOMAGNETIC GENERATION (Radel Gimaev, Katja Klinar, Andrej Kitanovski)

NUMERICAL MODELING OF AN ACTIVE MAGNETIC REGENERATOR BASED ON THE ROTATIONAL MAGNETOCALORIC EFFECT (Radel Gimaev, Darja Gačnika, Urban Tomc, Rafael Almeida, Rodrigo Kiefe, João H. Belo, João S. Amaral, Katja Klinar, Andrej Kitanovski)

PHASE-CHANGE MATERIAL THERMAL DIODES FOR CALORIC REFRIGERATOR (Karl Joulain, Katja Klinar, Katja Vozel, Andrej Kitanovski, Younès Ezzahri)

A GENERALIZED MODELLING APPROACH FOR ACTIVE ELECTROCALORIC REGENERATORS (Matija Kalin, Darja Gačnik, Katja Klinar, Andrej Kitanovski)

HYPEREG: HIGH-FREQUENCY MAGNETOCALORIC REGENERATOR (Andrej Kitanovski, Katja Klinar, Jure Javornik, Simon Nosan, Jakob Perne, Simon Bogić, Blaž Jagodic, Urban Tomc)

THE PERSPECTIVES OF ULTRA-HIGH-TEMPERATURE SOLID-STATE HEAT PUMPS (Katja Klinar, Darja Gačnik, Radel Gimaev, Andrej Kitanovski)

BRIDGING THE THERMAL GAP: THE ROLE OF FLUIDIC AND MECHANICAL THERMAL CONTROL DEVICES IN ADVANCING CALORIC TECHNOLOGIES (Katja Klinar, Urban Tomc, Katja Vozel, Andrej Kitanovski)

THERMAL CONDUCTIVITY OF CELLULOSE-BASED COMPOSITE FILMS (Vanja Kokol, Vera Vivod, Katja Klinar)

MODELING OF THERMOACOUSTIC GENERATOR IN TCCBUILDER (Izak Oberčkal Pluško, Harini Nivetha Raja, Grega Belšak, Jingyuan Xu, Katja Vozel, Andrej Kitanovski, Katja Klinar)

EVALUATION OF CURIE TEMPERATURE EFFECTS IN THE PERFORMANCE OF ACTIVE MAGNETIC REGENERATORS – PART I: SECOND ORDER PHASE TRANSITION (Urban Tomc, Guilherme F. Peixer, Chistian R. H. Bahl, Kaspar K. Nielsen, Jaime A. Lozano, Jader R. Barbosa Jr., Andrej Kitanovski)

DIGITAL MICROFLUIDIC THERMAL SWITCH CAPACITORS FOR MAGNETOCALORIC COOLING (Blaž Velkavrh, Hana Uršič, Urška Erjavec Nagode, Andrej Kitanovski, Lukas Beyer, Jens Freudenberger, Klara Lünser, Enric Stern-Taulats, Lluis Mañosa, Urban Tomc)

ENHANCING SOLID-STATE THERMAL RECTIFICATION VIA TEMPERATURE-DEPENDENT THERMAL CONTACT RESISTANCE (Katja Vozel, Andrej Kitanovski)

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New article: Roadmap for electrocaloric films characterization

admin — Thu, 28 May 2026 08:06:32 +0000

The article Roadmap for electrocaloric films characterization, published in iScience (Cell Press), presents a numerical investigation of substrate and infrared (IR) coating effects on the characterization of electrocaloric thick-film structures for future cooling applications.

Researchers from the Laboratory for Refrigeration and District Energy at the Faculty of Mechanical Engineering, University of Ljubljana, in collaboration with the Jožef Stefan Institute, investigated how substrate thermal properties and high-emissivity black coating thickness influence the accuracy of infrared temperature measurements of electrocaloric materials. The aim of the study was to establish guidelines for optimized characterization of electrocaloric structures at the micro- and nano-scale.

Using numerical simulations, the researchers demonstrated that substrates with low thermal effusivity and low thermal conductivity significantly reduce heat losses during measurements, enabling more accurate determination of the electrocaloric response. In addition, the influence of electrocaloric film thickness and black coating thickness on the IR correction factor was systematically analyzed. The results show that low single-digit correction factors can be achieved when the electrocaloric layer is thicker than the coating.

The study provides important guidelines for reliable electrocaloric material characterization and offers a roadmap for the design of future micro-scale caloric cooling systems..

Link: https://www.cell.com/iscience/fulltext/S2589-0042(26)01340-4

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High-temperature electrocaloric heat pump presented at the High-temperature heat pump symposium

admin — Fri, 23 Jan 2026 09:56:23 +0000

Researchers from the Laboratory for Refrigeration and District Energy (LAHDE) have visited High-temperature heat pump symposium in Copenhagen, Danmark. The event offered an excellent overview of the latest research and industrial developments in high-temperature heat pumps, with many insightful discussions and opportunities to exchange perspectives with experts from industry and academia.

We were pleased to present our work on solid-state electrocaloric heat pump in the poster session and to receive valuable feedback that will support our ongoing research. Many thanks to the organizers for a well-structured and high-quality symposium, and to all colleagues for the engaging discussions.

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Ultra-high-temperature electrocaloric heat pump

admin — Mon, 05 Jan 2026 09:01:01 +0000

Researchers from the Laboratory for Refrigeration and District Energy (LAHDE) have published first study on high-temperature electrocaloric heat pump in Journal of Energy conversion and management, one of the world’s leading scientific journal in the field of energy.

Nearly a quarter of waste heat is generated at temperatures exceeding 300 °C, yet conventional heat pump technologies remain inefficient in recovering and utilizing heat from such high temperature sources. In this study, we introduce a novel electrocaloric heat pump designed to operate with heat sources and sinks at ultra-high temperatures. The proposed heat pump system incorporates an active electrocaloric regenerator featuring PbZr_0.52Ti_0.48O₃ (PZT) epitaxial thin-film multilayers, which exhibit a superior electrocaloric adiabatic temperature change of 11.03 K at 402 °C (675 K), and pressurized helium gas as the working fluid. We conducted a parametric analysis to simulate the performance of the ultra-high-temperature electrocaloric heat pump and identified the optimal conditions for single- and multi-stage configurations. The single-stage setup achieved a maximum heating COP of 7.8 at a 30 K temperature span across the regenerator at a heat source temperature of 660 K. In comparison, the multi-stage configuration yielded the highest heating power 113.3 W/kg_EC and a max. COP 2.7 between 630 and 690 K. This study established a foundation for notable advancements in ultra-high-temperature heat pumps by employing electrocaloric energy conversion.

Link: https://www.sciencedirect.com/science/article/pii/S019689042501338X

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Emerging opportunities for high-temperature solid-state and gas-cycle heat pumps

admin — Sun, 21 Dec 2025 12:51:38 +0000

Researchers from the Laboratory for Refrigeration and District Energy (LAHDE), together with an international team, have published a study in Nature Energy (Springer Nature), the world’s leading scientific journal in the field of energy. The paper offers the first comprehensive assessment of an often-overlooked opportunity: alternative high-temperature heat-pump technologies that could replace inefficient fossil-fuel combustion and direct electric heating in industry and the energy sector. Doing so could significantly reduce energy use, greenhouse-gas emissions, and thermal pollution.

Heat lies at the core of the energy challenge. Around 50% of final energy consumption is used for heating and cooling, and roughly 50% of final energy is ultimately released as waste heat—heat that is frequently discharged into the environment via cooling towers, the warming of rivers or seawater, and other outlets. The study shows that high-temperature heat pumps can capture this waste heat and upgrade it efficiently to much higher temperature levels, suitable for demanding industrial processes.

Today’s commercial high-temperature heat pumps are typically limited to about 250 °C, whereas many industrial processes require higher temperatures—up to, or even beyond, 1000 °C. The newly published research therefore systematically presents and compares alternative approaches that could enable a step change: caloric, thermoelectric and thermoacoustic technologies, as well as mechanical processes based on Stirling and Brayton cycles.

Link: https://www.nature.com/articles/s41560-025-01908-4

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Visit of Prof. Xiaoshi Qian to LAHDE

admin — Mon, 28 Jul 2025 07:58:33 +0000

We were honored to host Prof. Xiaoshi Qian from Shanghai Jiao Tong University during his recent visit to Slovenia.

Prof. Qian delivered a compelling lecture titled “Harnessing Giant Electrocaloric Effect in High-Polar Entropy Materials”, offering fresh insights into the development of high-performance electrocaloric polymers. His talk sparked engaging scientific discussions with members of the LAHDE team, as well as with guests from the Faculty of Mechanical Engineering, University of Ljubljana, and the Electronic Ceramics Department (K5) at the “Jožef Stefan” Institute.

As part of the visit, we had the opportunity to showcase our laboratory facilities and share some of LAHDE’s current research efforts, from recent patents and experimental work to our broader research activities. Our colleagues from the Jožef Stefan Institute also presented their advanced material characterization capabilities, which further enriched the exchange. The visit highlighted several shared research interests and laid the groundwork for future collaboration in the field of caloric and solid-state cooling and heating technologies.

We sincerely thank Prof. Qian for his visit, the insightful discussions, and the opportunity to strengthen international scientific ties. We look forward to continued collaboration and knowledge exchange.

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World Refrigeration Day

admin — Thu, 26 Jun 2025 06:19:08 +0000

World Refrigeration Day, celebrated on June 26, was established to raise awareness about the critical role refrigeration, air conditioning, and heat pumps play in modern life. It honors the birth of Lord Kelvin (William Thomson), a key figure in thermodynamics. The day highlights the industry’s contributions to health, food safety, energy efficiency, and environmental protection. Institutions and organizations around the world celebrate it with educational campaigns, public events, webinars, and technical seminars, aiming to inspire innovation and promote sustainable practices in cooling technologies.

TCCbuilder: an open-source tool for the analysis of thermal switches, thermal diodes, thermal regulators, and thermal control circuits

admin — Mon, 11 Nov 2024 07:21:40 +0000

Researchers of the LAHDE laboratory of the Faculty of Mechanical Engineering, University of Ljubljana, have developed an open-source tool for 1D modeling of thermal control circuits, TCCbuilder. It is the first tool of its kind that enables quick and easy modeling of thermal control circuits thanks to its graphical user interface and thr associated library of materials used to create thermal control elements.

In addition to the library of materials, there is also a library of already designed thermal control elements from the literature. Researchers from various fields are invited to complement both libraries as well as to add functionality to the tool. Thus, TCCbuilder is not only an indispensable tool for simulations, but also a platform for the exchange of information and networking of researchers in the field of heat transfer and materials.

The tool is presented in the article TCCbuilder: an open-source tool for the analysis of thermal switches, thermal diodes, thermal regulators, and thermal control circuits, which describes the validation and examples of the use of the tool. The article is published in the journal iScience (IF = 4.6), Special Issue: Advanced thermal control: fundamentals and applications.

The article is freely accessible under the following link: https://doi.org/10.1016/j.isci.2024.111263

Summary:

In the area of thermal management, thermal control elements (TCEs) and thermal control circuits (TCCs) are proving to be innovative solutions to the challenges of temperature control and heat dissipation in various applications, ranging from electronic cooling to energy conversion and temperature control in buildings. Their integration promises to improve power density, energy efficiency, system reliability and system life expectancy. With the aim of connecting researchers in the field of thermal management and accelerating the development of TCEs and TCCs, we have developed an open-source TCC simulation tool called TCCbuilder that enables a quick and easy time-dependent 1D numerical analysis of the behavior of TCEs and TCCs. It uses the heat conduction equation to solve temperature profiles in different devices. The TCCbuilder application offers features not previously available with any other TCC modelling tool: a large adjacent library of materials and TCEs as well as a user-friendly graphical user interface (GUI).

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Calorics 2024, Cambridge

admin — Wed, 25 Sep 2024 10:25:17 +0000

The Calorics 2024 conference took place in the historic city of Cambridge (UK), at the Møller Institute in Churchill College. This event brought together leading experts, researchers, and industry professionals to exchange ideas and insights on the latest advancements in caloric materials and heat-pump technologies.

The presentations highlighted the recent development in magnetocaloric, electrocaloric, elastocaloric, and barocaloric materials, as well as their potential integration in (multi)caloric devices such as heat pumps and active regenerators.

The LAHDE’s contribution to the conference was Prof. Andrej Kitanovski’s presentation: »Challenges, opportunities, and future roadmap for energy applications of magnetocaloric materials«.

One of the standout moments of the conference was the demonstration of a refrigerator utilizing the barocaloric effect to efficiently pump heat, presented by Xavier Moya. Its cooling power was impressive enough to chill beers to the perfect temperature, which were then served to attendees after the presentations. We cannot wait for the day when we can have solid-state refrigerators in our own homes.

Attending the Calorics 2024 conference was an exceptional experience, offering invaluable opportunities for learning and collaboration, encompassed by the engaging discussions with fellow attendees. The wide range of presentation topics provided deep insights into the latest caloric materials and technologies.

We are excited to attend and present our research at the upcoming Calorics conference. We can’t wait to see how the field will develop in the future.

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