Refrigeration is one of the main sinks of the German and European electricity consumption and accordingly contributes to worldwide CO2 emissions. High reduction potentials are envisaged if caloric effects in solid materials are utilized. The recent discovery of giant entropy changes associated with ferroelastic phase transformations promises higher efficiency. Ferroic transitions enhance the entropy change of magneto-, elasto-, baro- and electro-caloric effects. Furthermore, because the refrigerant is in a solid state, the technology completely eliminates the need for high global-warming potential halofluorocarbon refrigerants. The smaller footprint for operation and the scalable mechanism open up further applications such as cooling of microsystems. While the principal feasibility of magnetocaloric refrigeration is already evident, the requirement of a large magnetic field (> 2 T) hampers wide industrial and commercial applications. It is expected that this obstacle can be overcome by materials with lower hysteresis and by using other types of fields (stress, electric).

In order to accelerate research on ferroic cooling DFG decided to establish the priority program SPP 1599 in April 2011. This SPP will address the following major challenges for introducing ferroic materials in practical cooling applications: Understanding of the underlying mechanisms, energy efficiency, effect size, fatigue, and system integration.

Projects proposals are required to cover one of the following "ferroic-caloric" material classes or combinations thereof: ferroelastic, ferromagnetic and ferroelectric materials. Proposals have to focus on basic or applied aspects of solid-state cooling processes.

In detail, the research programme of the priority programme will focus on four key problems related to ferroic cooling:

  • Which scheme is most efficient for solid state refrigeration?
  • Giant caloric effects occur only in the vicinity of a first order transformation. For comparison experiments should focus on the direct adiabatic temperature change and cooling efficiency.

  • Which length and time scales are involved?
  • Diffusionless transformations change the structure at the atomic scale. However, in real materials, the hysteretic transformation process creates complex microstructures spanning many length scales up to the macroscale. To understand hysteresis losses, collaborations should cover several length scales, consider coupling effects (thermo-mechanic-magnetic-electric) and, in particular, use suitable in-situ methods.

  • Which are the best materials and microstructures?
  • Solid state cooling does not only require a maximized entropy change but also heat capacity and conductivity contribute to the cooling power. Hysteresis losses and fatigue, which are critical due to the high cycle numbers required for cooling demonstrators, should be addressed. Research should centre on environmentally friendly materials.

  • Which are competitive device concepts?
  • The development of novel solid state cooling demonstrators is essential for the adaption of ferroic-caloric materials. Proposal should work out the advantage of the selected setup and consider the effort for the entire refrigeration system.

    The complexity of ferroic cooling requires a close collaboration of materials scientists, engineers, physicists and mathematicians. The aim of this priority programme is to bring groups from these disciplines together to combine their complementary expertise from basic research to application. Therefore joint proposals or bundles of proposals are encouraged. The number of principal investigators should reflect the complementary scientific expertise needed for the proposed research. These proposals should aim at a comprehensive assessment of efficiency of solid-state refrigeration, addressing the route from materials fundamentals to demonstrators. Proposals addressing methodological aspects relevant for understanding solid-state refrigeration must give detailed plans for bilateral cooperation with particular partners.

    Proposals considering liquid/ gaseous or thermoelectric refrigerants or focussing on actuation/sensor applications alone will not be funded. Also, concepts which aim on electric power generation will not be considered.

    +++ Final papers of SPP 1599 +++ Special Issue of Energy Technology +++


    20. + 21.10.2011 Kick-off for all interested scientists in Dresden

    November 2011 Public call for proposals

    09.03.2012 Deadline for submission of proposals

    Summer 2012 Evaluation

    Autumn 2012 Start of project

    Autumn 2018 End of project