This paper presents the mathematical model of a lead-acid battery, which is often used as the energy storage unit in hybrid power systems. The lead-acid battery is complex, nonlinear device exhibiting memory effect. In the hybrid power system, the battery plays very important role in sense that it controls all other energy converters integrated. The operating voltage of a PV system is determined by the battery, the turn-on and turn-off of the diesel genset is guided by the battery SOC. The battery is modeled to elaborate current-voltage characteristics based upon the important phenomenon like self discharge, gassing effect in the view of hybrid power system application. The model is developed in Matlab/Simulink environment. The measured current in the time period of 3 weeks in 90 Ah, 12V battery is used as input to the model and the output voltage of model is compared with measured one. The current-voltage behavior of the model is much closed to real one. The model is used for real time application.

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At present more than 2 million kl fossil fuels are imported by Nepal per year, which is increasing at the rate of 7% annually on an average since 2012. The transportation sector alone accounts for more than 63% of the total fossil consumption. The major demand of fuels for transportation sector is diesel used by heavy-duty vehicles with high payload. The diesel demand for the year 2050 is projected to rise by 18%. There is a need for alternative fuel to diesel, which is also called hard-to-decarbonize fuel. Green hydrogen produced by electrolysis can be possibly used to power heavy locomotives due to its impressive properties as a heavy-duty transportation fuel. Several countries have already identified hydrogen as the future fuel for decarbonizing the transportation sector. Hydropower resource can be converted to green hydrogen as an energy storage medium and electrifying transportation sector. This paper identifies the need for an alternative to diesel fuel in the transportation sector and attempts to introduce hydrogen as a decarbonizing fuel to electrify the heavy-duty transportation sector of Nepal. Attempts are made to investigate the economic and environmental benefits of hydrogen in Nepal for heavy duty transportation sector in comparison to conventional fuels.

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