University of Delaware researchers said they have developed a method for constructing offshore wind farms and proven that it is less expensive, faster and could make possible offshore wind deployment at a scale and pace able to keep up with the region’s scheduled retirements of other power plants.

The researchers said they calculated that their process will cost up to $1.6 billion less per project than conventional approaches and take half the construction time. (Read the full research report [pdf].)

The key insight was that the entire structure — from seafloor mounting to the top of the turbine — can be assembled in one piece in port, moved as a unit and, in one step, placed into the sea floor.

Lady Liberty x 2

The reference design used 10-megawatt turbines with support structures, together standing twice as tall as the Statue of Liberty and weighing 2,500 metric tons, the equivalent of 183 semi tractor-trailers. Figuring out how to build and move them around in port was the final hurdle addressed in the five-year study’s new construction method.

Instead of today’s method, which consists of carrying out parts separately and individually assembling each in the ocean, an on-shore assembly line is created. The result, researchers say, is that more money is spent in port, but far less money is spent at sea.

Non-monetary benefits also exist, they say. For example, shifting more of the assembly to land enables construction to proceed regardless of the weather and reduces time at sea from three days to 10 hours for each turbine installed.

Wind turbine assembly as envisioned by the Delaware research team. Source: University of DelawareWind turbine assembly as envisioned by the Delaware research team. Source: University of DelawareIntegral to the method is to anchor the turbines by suctioning large buckets to the seafloor rather than pounding in long cylinders of steel, called piles. This also means that the foundation doesn’t penetrate as deeply into the seafloor, which reduces costs for everything from the attachment process to the surveying required in advance. And without pile driving noise, the installation has no acoustic impact on marine mammals.

Testing Scenarios

The team began with a dozen possible design solutions, which they reduced to four construction scenarios worth evaluating for detailed engineering and cost.

To assess the different approaches, the team designed a hypothetical 1-gigawatt wind farm in the Delaware Wind Energy Area off Rehoboth Beach, Delaware, using the port near Delaware City.

A related assessment of seafloors showed the new approach could be effective from Cape Hatteras, North Carolina, to Massachusetts, and that it has the potential to work elsewhere after similar geological evaluation.

Research on turbine bearing wear and failure led the team to conclude that transporting turbines with installed blades would reduce lifetime. Transport with attached blades also would be unstable. Instead, the researchers developed a mounting for transport and a method for attaching the blades in place once at sea.

This project was funded by the U.S. Department of Energy as project DE-EE0005484. The full report is available at Industrializing Offshore Wind, along with two videos to compare the new construction method and the conventional approach.