Energy analysis of novel hybrid solar, biomass, and natural gas combined cycle plants

The integration of renewable energy into conventional power plants is a key strategy for enhancing efficiency and reducing emissions. This study investigates the performance of hybrid combined cycle plants integrating natural gas, solar energy through parabolic trough collectors, and biomass. Three configurations were analyzed to explore different integration strategies: solar energy is introduced in the topping gas cycle (i), in the bottoming Rankine steam cycle (ii), in both sub-cycles (iii). In all configurations, biomass is integrated via direct combustion in a post-combustor. Furthermore, the effect of biomass post-combustion on the topping cycle was evaluated. Indeed, a heat exchanger was implemented downstream of the biomass combustor to further preheat the air exiting the solar field before it is introduced into the natural gas combustor. A model was developed for the parabolic trough collector, while the other plant components were simulated using Thermoflex®. In addition to the overall net electric efficiency and to assess the contribution of each renewable source separately, key performance indicators were defined, including the solar-to-electric efficiency, and the total power share from all renewables. Results indicate that the configuration integrating solar energy in both sub-cycles, along with biomass post-combustion, achieves the highest overall efficiency, reaching up to 66%. However, Pareto criteria reveals that the configuration with solar integration into the bottoming cycle and biomass post-combustion is the best trade-off between the considered renewable parameters. This configuration allows to reach the highest electricity share from renewables (34.3 %) while maintaining competitive global efficiency.