Two prototypes left in the running -- Horns Rev extension

The technology choice for the 200 MW extension of the existing 160 MW Horns Rev offshore wind plant in Denmark is between two suppliers: Vestas and Siemens. Danish project developer Energi E2 has also chosen its offshore foundation type, according to the company's Henrik Noppenau.

The specific turbines under consideration are still prototypes, Noppenau told delegates at the Copenhagen Offshore Wind conference in October. One is the Siemens 3.6 MW unit with a 107 metre rotor diameter and the other a 4.5 MW Vestas V120 with a 120 metre rotor. E2 plans to erect one unit of each on Danish soil in 2006 and test them for about a year until the company makes its technology decision.

"We expect our test program will provide a confident basis for buying one of these turbines for Horns Rev II," said Noppenau. "We don't think it will be realistic to consider Repower's turbine by then," he added, referring to the 5 MW prototype being tested by the German wind turbine manufacturer.

E2 owns or partially owns three operating offshore wind plant in Denmark -- the 5 MW Vindeby project from 1991 (the world's first offshore wind plant), the 40 MW Middelgrunden station off Copenhagen from 2001 and the 165 MW Nysted station from 2003, all of which use Bonus (now Siemens) turbines on concrete gravity-based foundations.

"At Nysted, we had considered monopiles and steel. But the competition clearly showed we got the best solution and cheapest price with concrete and gravitation," Noppenau said. "Price is not the only parameter. It only counts for approximately 99%," he said, grinning. "Let's see if the steel people can find something that will last for 20 years offshore. When you see some of the monopiles out there now, you don't get the impression this is yet possible," he said, referring to corrosion on the monopiles at Horns Rev -- photos of which were shown to conference delegates at the Copenhagen conference.

The Danish energy agency awarded the Horns Rev II contract to E2 in the summer. Like Horns Rev I and Nysted, it will also be a government demonstration project. The concession for a fourth demonstration project, a 200 MW extension of Nysted, is not yet awarded. E2 plans to install and commission Horns Rev II in 2009.

The Horns Rev II grid connection will be taken care of and paid for by the new system responsible transmission company, "There will be no uncertainty regarding grid connection and no planning delay. Compared to other countries, this is a very strong model. We can concentrate on building the offshore wind farm and not use time on discussions with grid companies," said Noppenau.