Fig. 5(a) showed the net present value (NPV) and payback period
(PP) of the H2-producing plant with different discount rate.
Obviously, the NPV increased and PP decreased with the discount
rate decreased from 30% to 0 which indicated that the
H2-producing plant was more attractive with lower discount rate.
The optimal NPV of USD1266654 and PP of 4.8 years were obtained
at discount rate of 0.