During howling winter weather two years ago, the thousands of windmills dotting Denmark and its coastline generated so much power that Danes had to pay other countries to take the surplus. The incident was the first of its kind, and lasted only a few hours... Since then, there have been just two more instances in which the price of wind power in Denmark turned negative for a significant period of time because of excess wind.
This draws attention to the problems posed by the intermittancy and volatility of wind power and the need to effectively manage it. Apart from required complementary physical infrastructure, it also requires technologies that can store electricity. With an ambitious off-shore wind power generation plan, Denmark hopes to generate half its power from wind within eight years, up from less than a quarter currently. In this context, it is estimated that the supply of electricity might exceed demand for about 1,000 hours each year by 2020 unless there are substantial changes in the way electricity is managed in Denmark.
Among the technologies and practices being tried out to store wind power include pumping water uphill to reservoirs and releasing them to generate hydro-power later; extracting hydrogen from water through electrolysis and then using it to run fuel cells or synthesize gas to provide power when wind was unavailable; different types of batteries; and storing them in the batteries of electric vehicles.