Empowering Variable Renewables: Options for Flexible Electricity Systems

The IEA was tasked by the 2005 Gleneagles G8 Summit to draw together findings in the field of grid integration of renewable electricity, and to prepare recommendations for the G8 Hokkaido Toyako Summit, in July 2008. This report focuses specifically on measures to increase the flexibility of power systems – their ability to operate reliably with significant shares of variable renewable electricity (var-RE). The term “power system” is here used to denote the whole chain of electricity production, transmission, trading, distribution and consumption. Measures involving capital investments to increase the flexibility resource of a power system, including additional flexible generation capacity, energy storage, and inter-area interconnection capacity, have been looked at in detail previously by the IEA. This report focuses on a portfolio of measures available with today’s technology to optimise access to and the use of this resource, through modification of the operation and design of electricity markets and transmission, thus enabling higher var-RE share. Chapter two discusses variability, and how a system-wide approach to the integration of var-RE power plants can have a smoothing effect on their output, before touching on the issues of forecasting and predictability. Chapter three outlines a methodology to assess power system flexibility. Chapter four highlights measures to increase flexibility, which relate to the operation of physical power markets, while chapter five covers the optimisation of transmission and distribution networks – the grid. Finally, chapter six provides conclusions.