The U.S. offshore wind industry has certainly taken its time forming, and perhaps for good reason. Slow and steady may win the race, but in this case it is less about winning and more about wisdom. As Saint Augustine observed: “Patience is the companion of wisdom.”
Offshore wind development is a costly venture, but one the UK, for example, has managed to decease by 32% over the past five years. This is, in part, because of improved foundations, turbines, and O&M efficiencies. Patience has meant that the local industry has the good fortune of hindsight, thanks to the 20-plus year history of the offshore wind in the UK and Europe.
To date, the United States has only one five-turbine project south of Block Island, R.I., but more projects are in the development pipeline. By one count, U.S. planners foresee 28 offshore wind projects with a total potential capacity of 23,735 MW. As of writing, developers have secured 11 commercial leases from the Bureau of Ocean Energy Management (BOEM), which oversees federal waters, to build over 14 GW of offshore wind off the coasts of Rhode Island, Massachusetts, Virginia, Maryland, New Jersey, Delaware, and New York.
One lesson the offshore industry seems to have learned early on is read from the same playbook. Case in point: the U.S. recently launched a new offshore standards initiative. The three-year project is a collaborative effort between industry stakeholders (such as AWEA, the NREL, DOE, BOEM and others). The goal is to update AWEA’s 2012 offshore compliance recommended practices and develop a set of standards for the offshore wind sector that are recognized by the American National Standards Institute.
Standards are particularly important for offshore projects because the risks are greater than on land. Safety starts with the crew transfer vessels and technicians working offshore. In addition, the wind turbines, foundations, and underwater cables have greater potential for wear and corrosion from exposure to seawater, and must be designed to endure offshore conditions.
While anti-corrosive materials and protective coatings may seem obvious for environments that routinely expose equipment to saltwater and harsh offshore conditions, engineers are still researching for an ideal combination of materials, components, and safety standards for the industry.
To get an idea of what’s new, here are a handful of recent inventions that may benefit the local offshore wind industry, particularly as more projects are approved and developed in U.S. waters.
Place steel in water long enough, and it will rust. For this reason wind developer, E.ON, in cooperation with Rambøll Germany, has formulated a specialized anti-corrosion coating for steel foundations offshore.
The new Thermal Spray Aluminum (TSA) coating is said to significantly reduce corrosion on monopole foundations for a 25-year operating lifetime, and reduce metal deposits into the sea by several hundred tons.
The TSA coating process is automated to save time, costs, and ensure a smooth, continuous application. A robot with two arc burners sprays a 350 μm thick layer of molten aluminum onto each foundation, and then seals the surface with resin. This process is carried out under stringent safety and environmental protection standards, and is nearly dust-free. For the first time, E.ON recently applied TSA to 60 steel foundations for the Arkona offshore wind farm in the German Baltic Sea.
Impact-monitoring for safer docking
The sea makes no promises, especially for U.S. projects sited in deep water with high winds. To complicate matters, vessels must accommodate stringent requirements regarding the total impact force permitted against offshore structures, including wind turbines and offshore docks or platforms (say, when dropping off or picking up workers). Boats and vessels are typically expected to remain within pre-specified ranges of impact force, and to operate only within certain environmental conditions. This means docking will often be challenging for equipment and crew-transfer vessels.
UK Electronic Solutions’ Oceanic Dynamics aims to make learning this skill easier for captains. Oceanic Dynamics is a self-contained motion and impact-monitoring system. According to the developers, the system protects the longevity of offshore assets by monitoring and reporting vessel impact on structures, passenger comfort and safety, and engine performance and reliability. Oceanic Dynamics is also able to monitor fuel efficiency, engine data, and route information, and a vessel’s stability in the water—potentially leading to a smoother sail.
Offshore cable protection
Unlike onshore wind-farm installations, offshore cabling routes are typically more difficult to access, install, and repair. Therefore, cable protection is essential to reduce the risk of faults or damage. Trelleborg’s NjordGuard protects offshore wind-farm power cables by reducing drag and snagging risks. Trelleborg says the system requires minimal assembly, is easily extendable, and can be manufactured to meet any diameter cable. What’s more is the system can be installed, removed, and reused without the use of remotely operated vehicles or diver intervention, thereby improving safety and reducing installation challenges.
“The solution also permits monopile and J-tube installations for wind-turbine generators and offshore substation platforms without procedural variation,” said John Deasey, Renewables Sales Manager at Trelleborg’s UK offshore operation.
Securing turbine cargo with a twist
The transport of wind-turbine cargo offshore requires a range of safety procedures that ensure the equipment and onboard crew remain unharmed.To this end, DNV GL has launched a joint industry project (JIP) to develop recommended practice intended to de-risk the adoption of a wind turbine cargo fastening process, known as “twisties.”
The twisties concept is a modular project-cargo transport frame that is sea-fastened using container twist locks. Twist-lock, stackable blade racks are now typical on the decks of installation vessels.
According to DNV GL, Transporting turbines and other wind farm components using “Twisties” significantly lowers construction program durations. It also allows installing greater quantities of turbines to be installed using a defined number of turbine installation vessels. In fact, the concept demonstrates cost savings of over 25% in some cases when compared to conventional installation practice.
“Establishing a JIP will de-risk the implementation of this technology and promote the ‘unitization’ of wind project cargo,” said Chris Garrett, Senior Offshore Wind Farms Engineer, DNV GL. “Understanding the technicalities of existing wind industry transportation methods let us demonstrate the benefits that a standardized unit approach will bring to the entire industry.”
Robot-led underwater inspections
Researchers at the Technical University of Demark are working on a modular robot for use in offshore wind-turbine platforms. The robot will first be used for underwater inspections, with the long-term aim of it helping with repairs on foundations and rigs.
For example, the robot could install and replace sensors in a subsea docking station, which could be placed on the foundation of a wind turbine to provide continuous monitoring.
Currently, remotely operated vehicles (ROV) along with divers are hired to inspect and repair damage to foundations. However, such arrangements are costly and weather-dependent.
“The underwater robot will have the great advantage that it can be permanently installed on an underwater foundation where it can monitor and operate independently of the weather conditions,” said Professor Mogens Blanke from DTU Electrical Engineering, acting supervisor for a few of the PhD students contributing to the research.