An alignment of economics, demographics, climate change and technology has set in motion an ongoing transformation of the global energy system. Growing populations, with improved living standards and increasingly concentrated in urban centres, have dramatically raised the demand for energy services. At the same time, a growing consensus over the dangers posed by climate change has prompted people and governments worldwide to seek ways to generate that energy while minimising greenhouse gas emissions and other environmental impacts. Rapid technological progress, combined with falling costs, a better understanding of financial risk and a growing appreciation of wider benefits,