Methods and solar power generation systems including a working fluid circuit providing for the flow of supercritical carbon dioxide (S-CO.sub.2) therein. The methods and systems may also include a solar energy receiver in thermal communication with the working fluid circuit providing for solar heating of the S-CO.sub.2 working fluid; a power turbine in fluid communication with the S-CO.sub.2; a generator mechanically coupled to the power turbine; a compressor turbine in fluid communication with the S-CO.sub.2 and a compressor mechanically coupled to the compressor turbine such that the compressor is configured to compress the S-CO.sub.2 within a portion of the working fluid circuit. The methods and systems may optionally include a secondary power block in thermal communication with a primary power block. The methods and systems may optionally include thermal energy storage. Various embodiments may be implemented in a modular fashion and located on or within a solar energy tower.
 The United States Government has rights in this invention under Contract No. DE-AC36-08G028308 between the United States Department of Energy and the Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory.