Thermodynamic analysis of a new double-pressure condensation power generation system recovering LNG cold energy for hydrogen production |
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| Affiliation: | 1. Renewable Energies and Environmental Department, Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran;2. Hydrogen and Fuel Cell Laboratory, Faculty of New Sciences and Technologies, University of Tehran, Tehran, Iran;3. Department of Chemical Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, P.O. Box 11365-4435, Tehran, Iran;4. Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4, Canada;1. College of Petroleum Engineering, Liaoning Shihua University, Fushun, Liaoning 113001, China;2. School of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400054, China;3. College of Chemistry, Chemical Engineering and Environmental Engineering, Liaoning Shihua University, Fushun, Liaoning 113001, China;4. College of Pipeline and Civil Engineering, China University of Petroleum (East China), Qingdao, Shandong 266555, China;5. Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of China, Chongqing University, Chongqing 400044, China;1. Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, 200240, China;2. College of Mechanical Engineering, Shanghai University of Engineering Science, Shanghai, 201620, China |
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| Abstract: | Cold energy during the LNG regasification process is usually applied for power generation, but the electricity demand varies with the time. Therefore, a thought that transforming electrical energy into hydrogen energy by PEM electrolyzer is put forward to adjust the adaptability of power output to electricity demand. This paper proposes a new double-pressure condensation Rankine cycle integrated with PEM electrolyzer for hydrogen production. In this system, seawater is used as the heat source, and binary mixed working fluids are applied. Meanwhile, multi-stream heat exchanger is introduced to improve the irreversibility of heat transfer between LNG and working fluid. The key system parameters, including seawater temperature, the first-stage condensation temperature, the second-stage condensation temperature, and outlet temperature of LNG, are studied to clarify their effects on net power generation, hydrogen production rate and energy efficiency. Furthermore, the hydrogen production rate is as the objective function, these parameters are optimized by genetic algorithm. Results show that seawater temperature has positive impact on the net power output and hydrogen production rate. The first-stage condensation temperature, the second-stage condensation temperature, and outlet temperature of LNG have diverse effects on the system performance. Under the optimal working conditions, when the LNG regasification pressure are 600, 2500, 3000 and 7000 kPa, the increasing rate for optimized net power output, hydrogen production rate and energy efficiency are more than 11.68%, 11.67% and 8.88%, respectively. The cost of hydrogen production with the proposed system varies from 1.93 $/kg H2 to 2.88 $/kg H2 when LNG regasification pressure changes from 600 kPa to 7000 kPa. |
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| Keywords: | LNG cold energy Double-pressure condensation rankine cycle PEM electrolyzer Hydrogen production Heat transfer analysis |
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