Climate change has, more than anything else, imposed innovative challenges for present human energy systems. This course begins with an overview of global energy systems based on oil, carbon, nuclear and hydro power as well as supplementary systems. Three areas are given particular emphasis: firstly, energy end use efficiency, its historical development and future prospects; secondly, renewable energy and the ongoing change at its technological frontier; thirdly, transports, their different systems, use of energy and impact on the environment as well as ongoing technological change. Both positive and normative aspects of the interplay between economic growth and energy are treated. Among the first aspects is the so called decoupling of energy and GDP, for example whether the third industrial revolution implies a reduction of energy use. Normative aspects consider institutional and political factors which determine incentives for innovation.