Development and thermodynamic analysis of a low-carbon power and synthetic natural gas co-generation plant driven by hybrid biomass-solar energy

Abstract

An innovative low-carbon system based on gasification of wood and solar energy is proposed and analyzed for co-generation of power and synthetic natural gas. Produced synthetic fuel can be directly injected into the natural gas grid or utilized as a promising energy carrier in order to save surplus power to overcome the problem of intermittent nature of generated power by solar energy. The integrated system comprises an externally fired gas turbine cycle, a regenerative steam Rankine cycle, an organic Rankine cycle, proton exchange membrane electrolyzer, methane synthesis unit and photovoltaic solar system. Thermodynamic models are developed to evaluate system proficiency from energy, exergy, and environmental perspectives. Synthetic fuel production rate is evaluated in two different scenarios (solar supported and non-solar supported) under five electrolyzer operating loads as green hydrogen route. when 10 % of the power is allocated to produce the hydrogen required for the methanation process, overall exergy efficiency is obtained 39.19 % and 42.12 % for the solar energy scenarios, respectively. In this case, 1021 t/yr CO₂ is utilized by the solar supported system to produce 380.5 t/yr synthetic fuel with sustainability index of 1.645 while, 804.7 t/yr CO₂ utilized by the non-solar supported system to produce 299.8 t/yr synthetic fuel with sustainability index of 1.728. According to the Sankey diagram, externally fired gas turbine cycle is the primary source of thermodynamic inefficiency, with the gasification unit being the most exergy destructive component.