Storage of fluctuating wind energy

Over the last 15 years wind energy becomes more and more important in Germany. The total installed capacity of wind generation was 19300 MW (June 2006) with new installation of about 900 MW in the first 3 months in 2006. In 2010 the contribution of renewable energy to the gross electricity consumption shall be 12.5 per cent (renewable energy sources act EEG) and in 2020 20 per cent. The acceptance of utilisation of wind power in Germany is very high. Wind energy supply varies over day time, over the year and regional. In addition demand of electrical power varies over daytime and over the year but not correlated with the variation of wind. The average full load hours of the German wind generation is about 1600 h/a and will increase 2010 to about 1960 h/a based on increasing off-shore wind parks in Germany. In 2010 24 GW wind plants are planned on-shore, in the North Sea additional 4.4 GW off-shore wind parks and in the Baltic Sea about 1 GW off-shore wind generation. This will increase 2015 to 8.4 GW (North Sea) and 1.4 GW (Baltic Sea). The load centers in Germany are in the central and southern parts of Germany far away from the main wind park locations at the coasts or off-shore. To transport this high power to the load centers some hundred kilometre of new AC and DC lines have to be built together with new compensation and control equipment to strengthen and operate the system securely. 4 main corridors each with a capacity of 2000-4000 MW are necessary to bring the power to the load centers. In the last years there is a discussion about the necessity of such a large improvement of the system and the possibilities to solve the transportation targets closer related to the average available wind power and not related to the size of installed wind power capacity. A possible alternative is the installation of energy storage systems based on compressed air (so called compressed air energy storage CAES) stored in large underground caverns. The paper will show the available technology and the possibilities to combine this storage equipment with wind parks to use wind parks in a way of quasi conventional power plants.