The principles of Chemical Engineering are widely used in the energy industry. Traditionally, the Upstream (exploration and production) and Downstream (refining, manufacturing chemicals etc) industries have relied on an understanding of thermodynamics, fluid flow, transport phenomena, chemical kinetics, and reactor engineering to design projects, optimize operations and troubleshoot any issues. These same principles also apply to the new renewable/sustainable energy initiatives the industry is currently focusing on. In this talk, we will specifically discuss, via examples, on the applications of fluid flow and reactor engineering in both conventional (oil & gas) and upcoming (renewable/sustainable) energy businesses within Shell.