Contents lists available at ScienceDirect Geothermics journal homepage: www.elsevier.com/locate/geothermics Energy, exergy and exergoeconomic analysis of a cogeneration system for power and hydrogen production purpose based on TRR method and using low grade geothermal source Hadi Ghaebi ⁎ , Behzad Farhang, Towhid Parikhani, Hadi Rostamzadeh Department of Mechanical Engineering, Faculty of Engineering, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil, Iran ARTICLE INFO Keywords: Geothermal energy Organic Rankine cycle Proton exchange membrane electrolyzer Working fluid Exergoeconomic analysis Cogeneration ABSTRACT In this research, a modified organic Rankine cycle (ORC) with a regeneration is used to generate power along with hydrogen. For hydrogen production purpose, a proton exchange membrane (PEM) electrolyzer is used, taking its required heating and power from the ORC. The proposed system is driven by geothermal energy. A comprehensive thermodynamic modelling (energy and exergy analysis) and exergoeconomic analysis are carried out for the proposed cycle, using various working fluids (i.e., R245fa, R114, R600 and R236fa) in order to compare their influences on performance of the integrated system. For this purpose, Engineering Equation Solver (EES) software is used in all conducted simulations which is proven to be the most professional and commercial software in thermodynamics. In addition, a comprehensive parametric study is carried out for investigating the effects of main thermodynamic flow parameters on the energetic, exergetic and economic factors of the in- tegrated system. The results showed that R245fa had the highest energy and exergy efficiencies of 3.511% and 67.58%, respectively. Furthermore, it is the most cost-efficient working fluid with 11.54 $/GJ and 4.921 $/GJ average costs per exergy unit for output power and hydrogen production, respectively. Regarding their opera- tional features and cost effectiveness, the working fluids R114, R600 and R236fa ranked successively after R245fa. Also R245fa had the lowest cost associated with the exergy destruction. Moreover, the results of parametric study showed that increasing of the evaporator pressure results in increasing of the output power, hydrogen production, and energy and exergy efficiencies, whereas the costs of output power and hydrogen production decreased. In addition, increasing the geothermal fluid temperature increases the output power, hydrogen production, and also their costs, while decreases the energy and exergy efficiencies. It is also found that an increase in the turbine extracted steam pressure (mean pressure) will increase the exergy efficiency, costs of produced power and hydrogen, whereas decrease the output power, hydrogen production, and energy effi- ciency. 1. Introduction Nowadays, due tothe decreasing fossil fuel sources and environ- mental pollutions caused by such fuels, most countries are trying to decrease their dependence on fossil fuels. Therefore, they carry out various research and experimentations on renewable and clean en- ergies. Geothermal energy is considered to be a clean and renewable en- ergy. Also, it is very cost-effective to generate high capacities of elec- trical power using geothermal energy (Alhamid et al., 2016; Michaelides, 2016). Geothermal energy temperature is varying in a range of 50 °C to 350 °C. Obviously high-temperature sources (larger than 220 °C) are the most appropriate kind of sources from the commercial standpoint. However, most geothermal sources are in a range of 90–220 °C and it is predicted that the next generation of geothermal power plants are going to use low-temperature sources (Shokati et al., 2015a,2015b). The organic Rankine cycle (ORC) is a power generating cycle that uses organic fluids with low boiling point which is established by low-temperature energy sources (Kalina, 1983). Meanwhile, hydrogen is considered as a clean energy carrier for generating environment adapting energies, which is used mostly in power plants and chemical industries (Balat, 2008; Winter, 2009). Furthermore, it can be used in fuel cell systems to produce electricity more effectively and with inconsiderable greenhouse consequences (Dincer, 2014; Kang et al., 2007). Nowadays, hydrogen can be pro- duced through fossil fuels, reforming processes of hydrocarbons and http://dx.doi.org/10.1016/j.geothermics.2017.08.011 Received 31 May 2017; Received in revised form 17 July 2017; Accepted 24 August 2017 ⁎ Corresponding author. E-mail address: hghaebi@uma.ac.ir (H. Ghaebi). Geothermics 71 (2018) 132–145 0375-6505/ © 2017 Elsevier Ltd. All rights reserved. MARK