Research and Development of Magnetic Heat Pump Technology ~A further advance towards the realization of high-efficiency CFC-free heat pumps~
June 19, 2012
Chubu Electric Power Co.,Inc.
Railway Technical Research Institute
Chubu Electric Power Co., Inc. (President and Director: Akihisa Mizuno; Location: 1 Higashi shincho, Higashi-ku, Nagoya; "Chubu Electric" below), the Railway Technical Research Institute (President: Hisashi Tarumi; Location: 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo; "Railway Institute" below) and Santoku Corporation (President: Chikara Okada; Location: 4-14-34 Fukae Kitamachi, Higashinada-ku, Kobe; "Santoku" below) are engaged in the development of a magnetic heat pump technology able to heat and cool by means of the rotation of permanent magnets as part of the Innovative Energy Saving Technology Project(*1). The research partners have now developed a fundamental magnetic heat pump technology that demonstrates high efficiency and represents a further advance in technological development towards the practical realization of these devices.
Magnetic heat pump technology differs from conventional heat pump technologies based on the compression and expansion of CFCs or gases used as substitutes for CFCs. This technology exploits the fact that heat is generated when a magnetic field is introduced to a magnetic working material(*2), and the temperature declines when the magnetic field is removed. Magnetic heat pumps are expected to operate with an almost ideal heat cycle, and thus to be effective in conserving energy, to benefit the environment by doing away with the use of CFCs and CFC substitutes, and to be quiet and produce low levels of vibration due to the fact that they will not use compressors. They are expected to find applications in future air conditioners and refrigerators.
In the current research, Chubu Electric and Santoku applied a metal melting and solidification technology(*3) to create a new material known as lanthanum-iron (La-Fe) material, which demonstrates approximately twice the change in temperature of the conventional magnetic working material gadolinium (Gd), and can be manufactured in units of kilograms.
The performance of La-Fe materials is known, but mass production technologies have not been available, and it has therefore not been possible to obtain sufficient quantities of the materials for evaluation of their performance as a magnetic heat pump material. The new development has made evaluation of these materials possible.
The mass-produced La-Fe material was fitted in a system, developed by the Railway Institute, which is able to evaluate the performance of mock-ups of magnetic heat pumps, and system performance was studied by Chubu Electric and the Railway Institute.
The results demonstrated that the use of the developed material enabled the realization of a refrigeration capacity of 100 W, approximately two times greater than that achieved when Gd is used. The system's coefficient of performance (COP)(*4), obtained by dividing refrigeration capacity (Q) by power consumption (P), was 4.5, indicating that the system's refrigeration capacity and efficiency will increase with improvements in the performance of the magnetic working material.
This outcome has advanced us further towards the development of systems that achieve a COP of over 10 when 10 kW-class systems at the level of practical use are projected. Looking towards the early introduction of this technology to automotive air conditioners, vending machines and other applications, we will continue to create prototypes and test more compact, higher efficiency kW-class systems through efforts that include the development of mass production technologies for new magnetic working materials and the optimization of the shape of the materials.
(*1) A national project initiated by the New Energy and Industrial Technology Development Organization (NEDO), which calls for proposals for relevant technologies. The present research and development project began in December 2011 as part of research towards the development of next-generation heat pumps. The research was commissioned on the basis of collaboration between industry, academia and government, with the involvement of the Interdisciplinary Graduate School of Science and Technology of the Tokyo Institute of Technology, Kobe University's Graduate School of Engineering, the Physics School of Kyushu University's Graduate School of Sciences, Sanden Corporation, and the Hokkaido Research Organization.
(*2) A material that acts like a magnet when it is introduced to a magnetic field (when a magnet is brought close to it).
(*3) A technology for forming a metal into any desired shape by melting and then cooling it.
(*4) Coefficient of performance(COP)= Refrigeration capacity / Power consumption. Energy savings increase the higher this number is.