In the next few years, at least five offshore wind projects will hit U.S. waters. As developers prepare for construction, port facilities must also make preparations to support these projects. So what might an ideal port look like?
According to the Massachusetts Clean Energy Center, one developer suggests a port would need a 1,000-ton crane mounted on rolling tracks. The crane would transfer components from a delivery vessel to a storage location. A large loading and unloading area is need for assembly and storage.
A port facility must have adequate laydown space for delivery, storage and assembly of turbine components. Among developers, OEMs and staging facility data, the estimated area varies widely. But a minimum of 10 acres was required with ideally a 15 to 25-acre area. When all components of a large development are to be fully stored on land prior to installation, including both assembly and foundation components, the area required would be about 200 acres.
In general, the logistics of manufacturing, assembly and installation would not require all elements on the ground at one time. To maximize the use of construction equipment, vessels and crews, turbine suppliers require storage based on two factors: having a supply of turbine components ready for assembly and deployment, and having an additional area ready for instances when weather precludes deployment to the installation site while import vessels continue delivering components to the staging port. While turbine assembly continues, newly arrived unassembled turbine components need storage. Based on recommendations and assuming storage of 20 or more turbines at any one time, the minimum space needed in this case is about 8.5 acres.
Water-depth requirements relate directly to the vessel type, draft and function. The minimum water depth at mean low water applies to both the navigation channel and the berth. The deepest draft vessel used for transporting offshore wind components sets the navigation channel depth criteria. The vessel length of the largest expected vessel establishes the berth dimensions. With overlapping visits from import vessels, and transport and installation vessels, multiple berths or longer berths become a requirement. Horizontal channel clearance depends on vessel beam and component overhang during transport to installation sites. Unobstructed vertical clearance is highly recommended because of likely deployment methods in the future. Turbine OEMs expect tall tower sections to be transported to the installation site in the upright position. If the turbines are fully assembled for transport, then the nacelle and blade add significantly to this height.
Furthermore, various installation tasks require jack-up vessels–the retracted legs of which would be in the up position. There may be methods to work around vertical obstructions, such as placing a connector pin in the legs that would allow the legs to bend or using a hydraulic leg that compresses within itself, however, these methods add to costs and construction time.
Additional accommodations for interior storage and fabrication space are necessary at the port facility.
By Nic Abraham, Managing Editor, Windpower Engineering & Development