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  Cool BatMan: Battery Thermal  Management System Based on High Power Density Microfluidic Magnetocaloric Cooling

Consortium of 4 institutions:

  • University of Ljubljana (Slovenia) – dr. Urban Tomc (coordinator)
  • Jožef Stefan Institute (Slovenia) – prof. dr. Hana Uršič Nemevšek
  • Leibniz Institute for Solid State and Materials Research (Germany) – prof. dr. Jens Freudenberger
  • University of Barcelona (Catalonia) – prof. dr. Lluis Mañosa

Overall budget of 510.000 € over a 3 year period (2022-2025)

The final goal of the project is to design, develop and test a compact digital microfluidic magnetocaloric cooling device proof-of-principle. 

 

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SUMMARY: Li-ion batteries are believed to hold the key to transitioning away from the fossil fuels dependence in the next decade. However, a major bottleneck in Li-ion’s efficient and reliable operation is their narrow temperature range where they operaAte at their fullest efficiency without major degradation. There are two key aspects of battery thermal management system (BTMS) development; high efficiency and compactness of the BTMS. Especially in e-mobility, compact BTMS, preferably with no moving parts, is of the utmost importance. The majority of BTMSs are still based on the vapor-compression cooling technology. Due to utilization of environmentally harmful refrigerants and moderate efficiency, there is a need for new and more efficient cooling technologies. One, showing such potential is magnetocaloric (MC) cooling technology. However, today’s state-of-art MC devices are facing certain challenges due to the issues in an inefficient heat transfer and hydraulic losses, which consequently lead them to utilize large amounts of magnetic and MC materials, leaving no room for compactness or cost competitiveness to conventional cooling.

 

Figure 1: a) Schematic of electrowetting on dielectric principle (left-inactivated droplet-high contact angle, right-voltage activated droplet-low contact angle); b) by careful design of electrodes and turning them on and off the droplet can move across the surface (left: both electrodes off, right: right electrode turns voltage on and the droplet moves over it due to the contact angle change).
Figure 1: a) Schematic of electrowetting on dielectric principle (left-inactivated droplet-high contact angle, right-voltage activated droplet-low contact angle); b) by careful design of electrodes and turning them on and off the droplet can move across the surface (left: both electrodes off, right: right electrode turns voltage on and the droplet moves over it due to the contact angle change).
Figure 2: Two potential operational strategies of proposed MC/EWOD thermal switch cooling device.
Figure 2: Two potential operational strategies of proposed MC/EWOD thermal switch cooling device.

 

THE AIM of the project Cool BatMan is to gain a fundamental understanding of a dynamic thermal behaviour of two different physical effects coupled together for application in a compact MC cooling device. The magnetocaloric material, with its magnetocaloric effect, will be coupled with an ElectroWetting On Dielectric (EWOD) phenomenon to form a unique magnetocaloric cooling principle. EWOD is based on wettability of liquid droplets on dielectric solid surfaces by varying the electric potential, which enables manipulation of individual droplets (e.g., movement) as shown in Figure 1. Fast manipulation and movement of small volume liquid droplets as heat transfer fluid across the magnetocaloric material (instead of continuous fluid flow) could lead to a dramatic reduction of hydraulic losses and significant reduction of MCM mass, which in turn would lead to a much more compact cooling device. Liquid droplets would operate as a thermal switch, where a droplet would absorb heat from a discrete MCM location and by rapid controlled movement release it to the other discrete MCM location or to the heat sink (Figure 2).

The end and main goal of the project is to design, develop and test a compact MC/EWOD cooling device proof-of-principle, which will be suitable for integration as BTMS for Li-ion batteries in e-mobility (automotive, maritime or railway).

 

 

A PROJECT WORKFLOW was carefully devised and is shown in Figure 3. It involves numerical modelling of the proposed MC/EWOD cooling principle at an initial stage. This will lay firm ground for a key aspect of the project, which is establishment of a quality and reliable MC/EWOD fabrication process (involves several technologically complex sub-steps). To master the fabrication process, a thorough fabrication process quality control (characterization) will be put in place at every step of the development. Such a feedback-wise investigative approach will ultimately lead to the development of the first MC/EWOD proof-of-principle cooling device.

 

 

 

Figure 3: Shematic illustration of the project workflow with indicated TRLs.  
Figure 3: Shematic illustration of the project workflow with indicated TRLs.  

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