Waste to hydrogen: Investigation of different loads of diesel engine exhaust gas

In this study, green hydrogen production by utilizing diesel engine exhaust gas waste heat in steam and organic Rankine with internal heat exchanger with two thermoelectric generators and proton exchange membrane electrolyzer combined system under different load conditions is investigated. Thermo-economic, enviro-economic and exergo-environmental analyses of the maximum hydrogen production point determined for different waste heat conditions are carried out. Total and specific investment cost and levelized cost of hydrogen determined under different loads are compared. Simple and dynamic payback period, profit ratio of investment and net present value of the combined system at different selling prices of hydrogen are determined and their feasibility is analyzed. Carbon reduction and carbon credit gain amount due to green hydrogen produced in line with zero emission targets are compared under different waste heat conditions. Exergetic sustainability index of the system were determined within the scope of exergo-environmental analysis. In terms of economic and environmental performance, a hydrogen cost of 2.04 $/kg was obtained under 100% load and a carbon saving of 7211 $ was achieved depending on the hydrogen produced. Dynamic payback period and net present value were found to be 4.467 years and 404,696 $, respectively, if the hydrogen selling price was 5 $/kg under 100% load. It is found that a 50% load reduction leads to an increase in dynamic payback period and levelized cost of hydrogen by 18.6% and 13.72%, respectively, and a decrease in net present value and profit ratio of investment by 54.39% and 12.39%, respectively. On the other hand, since the exergy destruction decreases with the decrease in the load, exergo-environmental index is found to decrease by 2.03%.