Hydrocarbons contribute more than 95% of the world energy needs (85% fossil and 10% biomass). In a carbon-constrained world, systems using these resources must undergo radical transformation. The focus of our research has been on high efficiency, low-carbon energy from hydrocarbon sources, as well as hybridizing with concentrated solar thermal energy, through thermochemical conversion and combustion. We develop, validate and apply multiphysics multiscale simulation techniques, from the submicron scale to the system's scale, to engineer optimal, clean, low CO2-energy systems based on sound fundamental understanding of the underlying mechanisms. These include innovations in clean combustion for propulsion and power, gasification for power and biofuel production, and oxy-combustion and electrothermochemical conversion in ion-transport membrane reactors and high-temperature fuel cells for CO2 capture. Simulations are supported by high-performance computer systems, and state-of-the-art laboratories equipped with high-resolution optical diagnostics. We are funded by the US DOE, ONR and AFOSR; several energy giants including BP, ENEL, Bosch and Ford; international collaborations with MASDAR and KFUPM; and a significant award from KAUST. The program also benefits from inter-departmental collaborations with MIT faculty.