Energy assessment of an integrated hydrogen production system

Abstract

Hydrogen is believed to be the future energy carrier that will reduce environmental pollution and solve the current energy crisis, especially when produced from a renewable energy source. Solar energy is a renewable source that has been commonly utilized in the production process of hydrogen for years because it is inexhaustible, clean, and free. Generally, hydrogen is produced by means of a water splitting process, mainly electrolysis, which requires energy input provided by harvesting solar energy. The proposed model integrates the solar harvesting system into a conventional Rankine cycle, producing electrical and thermal power used in domestic applications, and hydrogen by high temperature electrolysis (HTE) using a solid oxide steam electrolyzer (SOSE). The model is divided into three subsystems: the solar collector(s), the steam cycle, and an electrolysis subsystem, where the performance of each subsystem and their effect on the overall efficiency is evaluated thermodynamically using first and second laws. A parametric study investigating the hydrogen production rate upon varying system operating conditions (e.g. solar flux and area of solar collector) is conducted on both parabolic troughs and heliostat fields as potential solar energy harvesters. Results have shown that, heliostat-based systems were able to attain optimum performance with an overall thermal efficiency of 27% and a hydrogen production rate of 0.411 kg/s, whereas, parabolic trough-based systems attained an overall thermal efficiency of 25.35% and produced 0.332 kg/s of hydrogen.

Keywords

• Hydrogen production
• Solar
• Rankine cycle
• Thermodynamic analysis
• Electrolyzer
• Parabolic trough