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 Market (Denmark, Finland, Norway and Sweden): 48%
  • the Western Interconnection of the United States: 45%
  • the New Brunswick System Operator in Eastern Canada: 37%
  • Mexico, 29%
  • the Iberian Peninsula (Spain and Portugal together): 27%
  • Japan: 19%.

The book does this with a four-step Flexibility Assessment (FAST) method for assessing existing flexible resources, which can then be used to balance increasingly variable supply and demand:

  1. assess the ability of the different flexible resources to change their production or consumption
  2. examine the aspects of the power system that will constrain them from doing so
  3. calculate the maximum requirement for flexibility of a given system resulting from fluctuating demand and output from wind plants and the like
  4. identify how much more variability can be balanced with existing flexible resources.

“While some areas are clearly more flexible than others, all power areas assessed show that greater technical potential for balancing variable renewable energy output exists than is commonly supposed,” said Richard Jones, the IEA Deputy Executive Director, when launching the book at EREC 2011, Europe’s Renewable Energy Policy Conference, on 24 May in Brussels.

“The results from these case studies demonstrate that variability needs not be an impediment to deployment,” he continued. “As long as power systems and markets are properly configured so they can get the best use of their flexible resources, large shares of variable renewables are entirely feasible from the balancing perspective.”

Photo by Evgeni Dinev.