By use of electronic structure calculations we aim to provide an atomistic understanding of the microscopic processes that come into play in materials for energy applications. The various processes that are envisioned range from surface catalyzed reactions to photon-to-chemical energy transformation reactions. Density functional theory is able to, in most cases, predict how different materials, surfaces and molecules will preform when affected by the circumstances that apply for a specific process. This might for instance be the activity of a catalyst material.