Microrefrigerators using lead-free ferroelectric refrigerants invented by Dr. G. P. Zheng, Assistant Professor of Department of Mechanical Engineering, was awarded Gold Medal at the 40th International Exhibition Inventions New Techniques and Products Geneva in Geneva, Switzerland.
The refrigeration units are solid-state refrigerants with a refrigeration effect better than 4 J/g. The microrefrigerators achieve the energy efficiency better than 86% and avoid using expensive heat switches or mechanical shifters, providing an environmentally friendly refrigeration solution.
Novel refrigeration methods that can be used to replace the vapor compression technology are desirable because of the abolishment of the refrigerant Freon in the near future around the world. Compared with other refrigeration technologies, the electro-caloric ferroelectric refrigeration technology has advantages in refrigeration efficiency, cost and easy implementation in applications. To date, most of the ferroelectrics are not practically used as refrigerants for such refrigeration technology because of their small refrigeration effect or the use of materials containing lead. In this invention lead-free ferroelectric ceramics that are environmentally friendly and are practical to be used in microrefrigerator are developed.
The microrefrigerators consist of electro-caloric ferroelectric refrigeration units whose size is 0.5-2 mm. Each refrigeration unit has 20-500 layers of ferroelectric refrigerant films. The refrigerants are lead-free and achieve a refrigeration effect better than 4 J/g under applied voltages of 40-300 V. The energy efficiency of the microrefrigerator is better than 86%.
The microrefrigerators are used for the cooling of hot spots in high-power micro-electronic components, devices and products. The ferroelectric refrigeration methods and the ferroelectric refrigerants developed in this invention are used to make very light refrigerators and air conditioners that can be used in electric vehicles and hospitals.