The Department of Energy (DOE) released the 2015 Quadrennial Technology Review (QTR), a more than 500-page report examining the status of foundational energy science and technology (S&T). The QTR also highlights the research, development, demonstration, and deployment (RDD&D) opportunities with a focus on technologies with commercialization potential in the mid-term and beyond. DOE intends to use the QTR in assisting decision makers as they set priorities, within budget constraints, to fund RDD&D and commercialization efforts that will develop more secure, affordable, and sustainable energy services.