Hydrogen energy storage system integrated with the surplus energy from Hydropower plant in the context of Nepal: A parametric study

Abstract

Abstract With the search for emission-free energy sources, hydrogen is considered a reliable alternative to store energy from renewable sources like wind, solar, thermal, and hydropower. Hydrogen has minimal environmental implications and can be stored and transported whenever there is an energy demand that other intermittent sources cannot suffice. This project aims to study the integration of hydropower with a hydrogen production and storage plant in Nepal to utilize excess energy supply that will exceed the country’s demand shortly. The excess power from the hydropower will be used to produce hydrogen from the water coming out from the tailrace. This water will also be a coolant for cooling the hydrogen before passing to the storage unit. This parametric analysis shows the effect of variation in the hydrogen inlet pressure before it enters the compressor unit and the impact of variation in storage tank pressure on the energy and exergy efficiency of the overall hydrogen production and storage system. In the first case, the inlet pressure varies from 0 to 20 MPa at three different constant storage pressures 40 MPa, 60 MPa, and 90 MPa. An increase in inlet pressure gradually increases energy and exergy efficiencies, but an increase in storage pressure lowers this efficiency. The reduction is more significant at a high value of inlet pressure. In the second case, the storage pressure varies between 20-80 MPa with constant inlet pressure at 0.1 MPa, 1 MPa, and 5 MPa. The increase in storage pressure gradually reduces efficiency, whereas the higher inlet pressure has higher efficiency. Hydrogen fills the gap between supply and demand of energy, so considering hydrogen production with multiple-stage compression and integration of three sources of energy: wind, solar, and hydropower has an excellent prospect for consistent and low carbon emission solutions.