A 31 MW extension which added 14 Enercon E70 turbines to a wind farm near Delfzijl makes it the largest in the Netherlands at 43 MW -- and it is to grow again by the summer. Another 12 to 14 turbines are due to be installed in June, adding a further 27 MW to the development and bringing annual production to around 155 million kilowatt-hours a year. Before this year's flurry of activity it consisted of six Enercon 2 MW turbines. The project is being developed by a joint venture comprising renewables developer Eventus Duurzaam and investment firm Yard Capital. The country's second biggest wind farm in terms of capacity, a project of 17 Vestas 2 MW machines, is in Biddinghuizen, Flevoland. But in terms of production, the 17 GE Energy 1.5 MW turbines at Rotterdam Slufterdam, which produce some 100 million kilowatthours a year, top of the list for now.