Energy plays a key role in realizing sustainable development in both advanced and developing countries alike, and it is therefore vital that investment in technological development be sustained in order to maximize the benefits of currently available energy resources. However, the question as to how that investment should be directed is a contentious one, and involves numerous parallel questions relating to efficiency, resource availability, cost effectiveness and environmental impact, among others. Furthermore, uncertainty remains as to the extent to which technological innovation can satisfy future global energy requirements, regardless of the future energy balance.