For thirty years now, the technology of wind turbines has developed increasingly large, efficient and reliable machines. This progress has been decisive, as much as incentives, to the deployment of wind farms in Europe, America, China, India and other countries. A wind generating capacity of 138 GW was on line worldwide as of the end of 2011.
Such success has been supported by national and international research programmes. Worth of special mention is the international co-operation under way since 1977 under the aegis of the IEA (International Energy Agency) and commonly known as the IEA Wind Implementing Agreement (http://www. ieawind.org). At present, this Agreement has 25 contracting parties: 22 entities from 20 OECD countries, the European Commission and the associations EWEA and CWEA. For Italy, the agreement has been signed by ENEA and RSE, both members of the Executive Committee. In addition to management issues, information exchange, and the drawing-up of an Annual Report on wind energy developments, the Executive Committee launches international research projects, named Tasks, where members can join forces on topics that could hardly be tackled by a single country. Up to now, 32 Tasks have been launched, of which 20 successfully completed, 2 stopped and 10 in progress. Task 11 is carried on continuously. Besides working out recommended practices, some of which have been a basis to prepare IEC Standards, Task 11 arranges meetings among experts on topics of recognised interest. The other ongoing Tasks deal with wind plants in cold climates, power systems with large amounts of wind generation, cost of wind energy, small wind turbines, social acceptance of wind projects, wind tunnel data for aerodynamic models, codes and models for offshore wind energy, wind flow models, wind measures by LIDAR, and (still under approval) reliability of wind turbines.