Small-scale hydrogen liquefaction with a two-stage GiffordeMcMahon cycle refrigerator Akihiro Nakano a, *, Tetsuhiko Maeda a , Hiroshi Ito a , Masao Masuda b , Yoshiaki Kawakami b , Atsushi Kato b , Manabu Tange c , Toru Takahashi d , Masahiro Matsuo e a National Institute of Advanced Industrial Science and Technology, Energy Technology Research Institute, 1-2-1 Namiki, Tsukuba East, Tsukuba, Ibaraki 305-8564, Japan b Takasago Thermal Engineering Co., Ltd., Research and Development Center, 3150 Iiyama Atsugi City, Kanagawa 243-0213, Japan c Shibaura Institute of Technology, Department of Mechanical Engineering, 3-7-5 Toyosu Koto-ku, Tokyo 135-8548, Japan d University of Tsukuba, Department of Engineering Mechanics and Energy, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan e JECC Torisha Co., Ltd., 2-8-52 Yoshinodai, Kawagoe, Saitama 350-0833, Japan article info Article history: Received 1 April 2010 Received in revised form 17 May 2010 Accepted 24 May 2010 Keywords: Hydrogen liquefaction GM refrigerator Liquid hydrogen Hydrogen storage Hydrogen energy system abstract We manufactured a small-scale hydrogen liquefier with a two-stage 10 K GiffordeMcMa- hon cycle (GM) refrigerator. It had a hydrogen tank with the volume of 30 L that was sur- rounded by a radiation shield. This liquefier continuously liquefied gaseous hydrogen with the volumetric flow rate of 12.1 NL/min. It corresponds to the liquefaction rate of 19.9 L/day for liquid hydrogen. We proposed a simple estimation method for the liquefaction rate and confirmed that the estimation method well explained the experimental result. To evaluate the estimation method, we applied the estimation method to other liquefiers. In case of a liquefier with the GM refrigerator, we confirmed the estimation method was available for predicting the liquefaction rate. However, in case of a liquefier with the pulse tube refrigerator, the results of the estimation indicated small values as compared with the experimental data. We discuss the details about the estimation method of the liquefaction rate for the small-scale liquefiers. ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. 1. Introduction We have investigated the totalized hydrogen energy utiliza- tion system for applying it to commercial buildings that consists of a unitized reversible cell, which has the fuel cell and the water electrolysis functions, and of metal hydride tanks using AB5 type metal hydride alloy [1,2]. We produce hydrogen using water electrolysis mode of the unitized reversible cell and store the hydrogen in the metal hydride tanks in nighttime, and generate electric power by means of the fuel cell mode of the unitized reversible cell in daytime. In case of emergency, we have a plan to use liquid hydrogen, which is transported from a hydrogen station. In this case, the metal hydride tanks store the boil-off gas from liquid hydrogen. To investigate the absorption/desorption charac- teristics of the metal hydride alloy for the boil-off gas, we designed and manufactured a small-scale hydrogen liquefier, which was the liquid hydrogen supplier, using a two-stage 10 K GiffordeMcMahon cycle (GM) refrigerator. At the present day, large-scale liquefier industrially produces liquid hydrogen. The JouleeThomson cycle (Linde cycle) is the simplest liquefaction cycle. The hydrogen gas is compressed and then cooled below the inversion temperature of 202 K in a heat exchanger before it passes through a throttle * Corresponding author. Tel.: þ81 29 861 7250; fax: þ81 29 851 7523. E-mail address: a.nakano@aist.go.jp (A. Nakano). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 35 (2010) 9088 e9094 0360-3199/$ e see front matter ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2010.05.104