Design of an innovative system for hydrogen production by electrolysis using waste heat recovery technology in natural gas engines

Abstract

This research proposes designing and implementing a system to produce hydrogen, utilizing the thermal energy from the exhaust gases in a natural gas engine. For the construction of the system, a thermoelectric generator was used to convert the thermal energy from the exhaust gases into electrical power and an electrolyzer bank to produce hydrogen. The system was evaluated using a natural gas engine, which operated at a constant speed (2400 rpm) and six load conditions (20 %, 40 %, 60 %, 80 %, and 100 %). The effect of hydrogen on the engine was evaluated with fuel mixtures (NG + 10 % HEF and NG + 15 % HEF). The results demonstrate that the NG + 10 % HEF and NG + 15 % HEF mixtures allow for a decrease of 1.84 % and 2.33 % in BSFC and an increase of 1.88 % and 2.38 % in BTE. Through the NG + 15 % HEF mixture, the engine achieved an energy efficiency of 34.15 % and an exergetic efficiency of 32.84 %. Additionally, the NG + 15 % HEF mixture reduces annual CO, CO2, and HC emissions by 9.52 %, 15.48 %, and 13.39 %, respectively. The addition of hydrogen positively impacts the engine's economic cost, allowing for a decrease of 1.56 % in the cost of useful work and a reduction of 3.32 % in the cost of exergy loss. In general, the proposed system for hydrogen production represents an alternative for utilizing the residual energy from exhaust gases, resulting in better performance parameters, reduced annual pollutant emissions, and lower economic costs.