Germany is officially opening its first offshore wind farm in the North Sea after years of delays and technical problems.

Environment Minister Norbert Roettgen said Tuesday he expects the test field Alpha Ventus, consisting of 12 windmills, to "push wide open the gate to the age of renewable energies."

German utility companies EWE, E.ON and Vattenfall teamed up to build the euro250 million ($340 million) project and test conditions in areas far off the shore lines.

Alpha Ventus lies some 45 kilometers (28 miles) off the German coast in 30 meter (100 feet) deep waters, which led to technical difficulties in mounting the 155 meter (509 feet) high turbines.

The German government had originally hoped to open the first offshore wind farms as early as 2004.