Carbon capture and storage (CCS) is an important technology that can contribute to the reduction of greenhouse gas emissions. It involves the capture of CO2 from point sources such as power plants and subsequent storage in secure geological reservoirs. However, capture incurs parasitic power loss; thus, compensatory power from clean sources such as renewables will be needed to make up for the power losses. The conventional capture process is designed for steady-state operation, but flexible capture is possible to offset the intermittency of renewable energy. Systematic planning for robust CCS systems is needed to incorporate flexible mechanisms in CO2 capture. In this study, a mixed integer linear program (MILP) is developed to robust CCS retrofit subject to operational adjustments for multiple periods or scenarios. Retrofit decisions include options for flexible and non-flexible capture, accounting for trade-offs between the two options. Operational adjustments pertain to decisions to switch off the flexible capture plants to compensate for depressed renewable energy supply. A case study is presented to demonstrate the optimization model. From the case study, flexible mechanism can provide a more robust planning, where low availabilities of renewable energy can contribute up to 18% of the power demand.