Intermittency of supply is a common criticism of some renewable sources of energy, specifically wind and solar.But a new book from the International Energy Agency (IEA), Harnessing Variable Renewables: a Guide to the Balancing Challenge shows that there is a greater technical potential for balancing variable renewable energy output than is usually assumed.It calculates the ability of eight regions to balance large shares of variable renewable energy: * The British Isles (Great Britain and Ireland together): 31% * Denmark: 63% * the Nordic Power...