Hybridization of solar and biomass energies, as two types of renewables, represents a resourceful way of complementing each other to overcome their individual drawbacks. In the present work, two novel solar-biomass hybrid power generation systems are proposed, modeled and compared with each other as well as with the standard biomass-based system without solar energy. In both the proposed systems biomass is first gasified in a gasifier and then syngas is used in a gas turbine plant combined with a Rankine cycle. In proposed systems the solar energy is used in the bottoming Rankine cycle, where the first system employs it in an indirect way to heat the feed water before deaerator while the second system adopts the solar energy in direct steam generation mode to generate additional steam for low pressure steam turbine. Thermodynamic and economic models are developed to investigate the systems' performances from the viewpoints of energy, exergy, economic and environmental. According to the results of economic evaluation, the levelized cost of electricity for standard, the first and second proposed configurations are obtained 79.34, 79.88 and 74.94 $/MWh, respectively. Also, the values of 0.79, 0.77 and 0.62 t/MWh are calculated for CO2 emission for standard, the first and second proposed configurations, respectively.