Introduction: balancing variations

Renewable energy sources are large but some are variable. The use of variable sources for energy supply will require some way of compensating for this. Power grids already balance variations in conventional energy supply and variations in energy demand and the approaches used for this can be expanded to deal with renewables, even when renewables supply 20–30% or more of the electricity on a grid. The main option is to use fossil plants to back up renewables. However at higher levels of renewable input, heading for 50% and beyond, other, additional, balancing mechanisms may also be needed, including energy storage, smart grid demand response and supergrid imports and exports. This introductory chapter looks at the variations associated with the various renewable sources and then outlines the options for dealing with them, which are then explored in more detail in the rest of the book.