Fred. Olsen has been working on a wave energy design called BOLT. It’s based on a floating platform attached to the seabed via moorings that are in turn attached to a specialized winch line product, which wind in and out of winches (one to three, depending on power requirements) as the sea surges. The winding motion creates energy – up to 10kW of average, exportable power with a standard unit in a high sea state - converted to electricity on board the facility via a custom designed maintenance free gear box and a standard Siemens generator set.
Even Hjetland, engineering manager for BOLT Sea Power, says it’s a design that’s been worked on for more than 12 years but that now has experience operating offshore Norway, the UK and in the Pacific (at a US Navy site off Hawaii). One of its next jobs is to provide a platform for a temporary 4G base station in the North Sea, working with communications firm Tampnet, to support field construction operations.
The lines used to drive the winches are UV (sunlight) and marine growth resistant, and the system still generates power in relatively calm sea states, says Hjetland. A system with one winch would be just 5-meter-diameter and weight 10-tonne, with up to 500kW of energy storage on-board.
Trials have included operations with the U.S. Naval Facilities Engineering Command, powering external oceanographic subsea sensors – including cameras and sonar systems - that were previously cabled, from a 30-meter test berth of the Navy’s Wave Energy Test Site (WETS), located offshore of Marine Corps Base Hawaii, near Kaneohe, on Oahu.
The system also included an underwater data-logging and non-contact power transfer solution, suitable for charging autonomous underwater vehicles (AUV), developed by Seattle-based startup, WiBotic. Part of this project also tested the ability to transfer power through the winch/mooring line itself, which would remove the need for an umbilical to subsea power users.
“We’re working with Tampnet next year to provide a floating, standalone 4G mast, by pulling a fiber cable from their existing network of subsea fiber cables and then beaming communication service during field construction phase when communication isn’t otherwise available,” says Hjetland. The floating structure will also house solar panels. The specific construction site has yet to be decided – it could be oil and gas or renewables.
“It could also be a platform for flying drones from for wind farm blade inspection,” he adds, “or at coastal fish farms. For oil and gas, standalone power and communications can offer charging power and control power. A UiD docking station could be installed wherever you want, instead of where power and communications are available.”