Performance analysis and optimization of a hydrogen liquefaction system assisted by geothermal absorption precooling refrigeration cycle Ceyhun Yilmaz a,* , Onder Kaska b a Department of Mechanical Engineering, Afyonkocatepe University, Afyonkarahisar, 03200, Turkey b Department of Mechanical Engineering, Osmaniye Korkut Ata University, Osmaniye, 151-742, Turkey article info Article history: Received 8 April 2018 Received in revised form 25 July 2018 Accepted 2 August 2018 Available online xxx Keywords: Geothermal energy Hydrogen liquefaction Thermoeconomic Optimization abstract The present paper deals with the hydrogen liquefaction with absorption precooling cycle assisted by geothermal water is modeled and analyzed. Uses geothermal heat in an ab- sorption refrigeration process to precool the hydrogen gas is liquefied in a liquefaction cycle. High-temperature geothermal water using the absorption refrigeration cycle is used to decrease electricity work consumption in the gas liquefaction cycle. The thermoeco- nomic optimization procedure is applied using the genetic algorithm method to the hydrogen liquefaction system. The objective is to minimize the unit cost of hydrogen liquefaction of the composed system. Based on optimization calculations, hydrogen gas can be cooled down to 30  C in the precooling cycle. This allows the exergetic cost of hydrogen gas to be reduced to be 20.16 $/GJ (2.42 $/kg LH 2 ). The optimized exergetic cost of liquefied hydrogen is 4.905 $/GJ (1.349 $/kg LH 2 ), respectively. © 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction In addition to playing an important role in the world economy, energy is the most important issues of the world economics and policies from past to present. Sustainable energy econ- omy is one of the leading research topics for all the world governments. Sustainability refers to the continuity of things in the larger sense. But in terms of engineering knowledge, it refers to using natural resources of Earth in a way that maintains their sustainability. In the scope of energy, sus- tainability refers to the energy supply that can be sustained without hurting potential dangers future supply of energy. This description serves green energy or renewable energy connotation today. The sustainable energy economy always takes to be base concept through the applications. The most energy required for storages, transports, and production is commonly selected using fossil fuels. But with a few scientific break- throughs hydrogen, the most abundant element in the uni- verse could be the energy carrier of a future sustainable end clean energy society. Maybe one step of this objective is hydrogen technology. Advanced energy technologies have developed a lower cost and easily used to produce and liq- uefied hydrogen through the low energy processes. Scientists have been searching for a good process to a solution that can * Corresponding author. E-mail address: ceyhunyilmaz@aku.edu.tr (C. Yilmaz). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2018) 1 e11 https://doi.org/10.1016/j.ijhydene.2018.08.019 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Yilmaz C, Kaska O, Performance analysis and optimization of a hydrogen liquefaction system assisted by geothermal absorption precooling refrigeration cycle, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.019