Electrocaloric heat pumps using two independently-controlled layers to achieve high cooling power. (15th December 2022)

• Record Type: Journal Article
• Authors: Najmi, Farrukh; Yi, Wei; Cheng, Z.-Y.
• Is Part Of: Nano energy. Volume 104(2022)Part B
• Publication Date: 2022-12-15
• Subjects: ECE Electrocaloric Effect -- ECM Electrocaloric Material -- TELM Ttwo-ECM-Layers Module -- CEHP Currently-existing ECE-based Heat Pump -- SO Thermal Source -- SI Thermal Sink -- VC Vapor Compression -- COP coefficient of performance; Electrocaloric effect -- Heat pump -- Cooling device -- Cooling power -- Electrocaloric, materials; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2022.107984
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: The development of electrocaloric materials (ECMs) with strong electrocaloric effect (ECE) in recent years offers a great opportunity for the development of solid-state heat pumps without using environmentally unfriendly vapor-based technologies. Currently existing ECE-based heat pumps (CEHPs) use one ECM layer that has to be moved back and forth between the thermal source (SO) and sink (SI), which raises reliability and safety concerns. Here, a design, which uses two layers of an ECM and the electric field on each layer is independently controlled with a special pattern, is introduced to develop ECE-based heat pumps with a high cooling power. In the design, the two ECM layers are permanently bound together and used as a single ECM module. The performance of the heat pumps is calculated using the newly introduced analytical solutions. First of all, it is found that the cooling power of CEHPs is strongly dependent on, while the cooling power of heat pumps using the two-ECM-layers module (TELM) is insensitive to, the materials used as the SO/SI. This would significantly expand the application of ECE-based heat pumps since in many applications there is no freedom to choose the materials to be used as the SO/SI. Secondly, the heat pumps using the TELM exhibit a high cooling power. For example, when different materials are used as the SO/SI, the cooling power of CEHPs would be changed over more than 100 times, while it is only changed less than 2 times when the TELM is used to replace the ECM layer used in CEHPs. And the cooling power of heat pumps using the TELM can be more than 7 times higher than the highest cooling power obtained in CEHPs. More importantly, the TELM can be permanently bound to the SO (or the SI) (i.e., the ECM is not moved at all during the operation), which would result in a high reliability. In this case, the cooling power of the heat pumps using the TELM can only be changed less than 25 % when different materials are used as the SO/SI and this cooling power is close to the highest cooling power obtained in the CEHPs. Graphical Abstract: ga1 Highlights: Two independently-controlled layers of an electrocaloric material are permanently bonded together as an ECE module. When the ECE module is used to replace the ECM in current designs the cooling power is enhance more than 7 times. When the module is permanently bonded to the SO/SI, the cooling power is ∼ 80 % of highest in current designs. The high cooling power obtained in designs using the ECE module is insensitive to the materials used as the SO/SI.