This thesis presents the thermodynamic and economic assessment of gas power cycles for 100 MW solar thermal power generation systems. A gas power cycle for solar power generation is a totally different technology from the current state of the art solar power generation systems. As a result, this thesis provides an assessment of the solar power generation systems with gas power cycles and provides guidance in the selection of design and operating parameters for gas power cycle based solar power generation system. The gas power cycle based power generation systems are assessed by means of thermodynamic and economic models developed and simulated using commercial thermodynamic analysis software. The gas cycle based power generation systems considered in this study are Cold Gas Turbine, High Temperature Solar Gas Turbine and Lorentz Cycle Gas Turbine. The system models are assessed for their thermodynamic performance using theory based turbo-machinery models with practical performance and loss data. In addition, extensive cost models have been developed for assessing the economic performance of the system models to determine their practical feasibility. The results from this study indicate that the most economical power generation system is the HTSGT system for a high peak cycle temperature utilizing the central receiver power tower solar collector system. The LCGT system also has a comparable performance at the same operating temperature. The CGT system assessed for operating with parabolic trough solar collector system at a lower peak cycle temperature had an inferior performance compared to the current state of the art technology for the power generation using parabolic troughs.