CCSI researchers have developed an equation-based optimization framework to facilitate the design and optimization of large scale fossil energy systems. This framework is being initially demonstrated for oxycombustion power plants, which are ideal candidates for optimization, given the complex trade-offs regarding flue gas recycle strategies, heat integration and design of cryogenic separation systems. Two recent papers, based on results described at the GHGT-12 Conference in October 2014, describe a hybrid 1D/3D boiler model that balances accuracy and computational expense, and an equation-based optimization framework for power plants.