Wind turbines and solar panels are likely to play a critical role in achieving a low-carbon power sector that helps address climate change and local pollution, resulting from fossil fuel power generation. Because wind and solar power output is weather-dependent, it is variable in nature and somewhat more uncertain than output from conventional fossil fuel generators. It is therefore important to consider how to manage high penetrations of solar and wind so as to maintain electricity system reliability. This introductory course, delivered by Ieading academics from Imperial College London, with technical input and contributions from the National Energy Renewable Lab (Golden, Colorado), will discuss what challenges variable output renewables pose to the achievability of a reliable, stable electricity system, how these challenges can be addressed and at what costs. Its overall objective is to demonstrate that there is already a range of established technologies, policies and operating procedures to achieve a flexible, stable, reliable electricity system with a high penetration of renewables such as wind and solar. The course uses a variety of country and context-specific examples to demonstrate the concepts. Policy makers, regulators, grid operators and investors in renewable electricity will benefit from a solid understanding of these considerations, thereby helping them drive forward the development of a fit-for-purpose clean power system in their own regional context.