Lee Hsun Lecture Series

Topic: Generating Electricity from Waste Heat using Magneto-structural Materials

Speaker: Prof. Ekkes Brück, Delft University of Technology, the Netherlands.

Time: 10:00-12:00, (Tue.) Sept.17, 2019

Venue: Room 249，Lee Hsun Building, IMR CAS

Abstract:

Magneto-caloric power conversion can be used to convert heat into electricity that up to now was considered as waste. This new technology therefore has the potential to significantly contribute to the energy transition on a global scale.

With the advent of giant magneto-caloric effects (MCE) that occur in conjunction with magneto-elastic or magneto-structural phase transition of first order (FOT), room temperature heat-pump applications became feasible. In this context the MnFe(P,X) system is of particular interest as it contains earth abundant ingredients that are not toxic. This material family derives from the Fe P compound, a prototypical example known since a long time to exhibit a sharp but weak FOT at 210 K (-63°C) [1]. Other promising materials are based on La(Fe,Si)13 [2].

Magneto-caloric power-conversion calls for a somewhat different combination of properties [1], in particular a large latent heat that is favourable for a heatpump, is detrimental for power conversion as a lot of heat is needed to change the temperature. Yet a large change of magnetization is required to generate a high torque in a device as depicted in Fig. 1, which suggests one should either employ materials exhibiting exchange inversion or second order materials. Magnetically highly responsive materials in combination with the field generated by a permanent magnet open the way to new technology for magnetic refrigeration, heat pumps and power generation. Employing the highly efficient coupling between the degrees of freedom of magnetic spins and lattice vibrations in a solid, will render energy conversion and energy generation technologies that get close to the theoretical limits.

References:
[1] L. Lundgren, G. Tarmohamed, O. Beckman, et al. Phys. Scr. Vol. 17, p.39-48 (1978)
[2] F.X. Hu, B.G. Shen, J.R. Sun et al. Appl. Phys Lett. Vol 80, p. 826-828 (2002)
[3] T. Christiaanse and E. Brück. Metallurgical and Materials Transactions E, Vol. 1 p.36-40 (2014)

KEYWORDS: Materials for Energy, Magnetocaloric, waste heat recovery.