For the Netherlands, wind energy, and especially wind energy at sea, is one of the most important forms of sustainable electricity production. ECN part of TNO develops knowledge that makes it possible for offshore wind farms to produce electricity in the short term at unsubsidised competitive rates. One of the most important ways to reduce the costs of offshore wind energy is the development of larger turbines. ECN part of TNO is developing new knowledge for this: from the anchoring on the seabed to the aerodynamics of the wind turbine blade and from the maintenance of the turbines to the connection to the electricity grid. This basic knowledge is used by the government for policy making and by companies for the development of their products and services. Dutch companies are world players in the construction of wind farms at sea. ECN part of TNO has unique research facilities, such as the possibility to test a wide range of prototypes of wind turbines, which many large manufacturers use.