Signature Projects are intended to bring focus to a selection of U.S. Department of Energy's Water Power Technologies Office (WPTO) projects. By designating a Signature Project, the project reports, datasets, and associated papers can be easily discoverable. By bringing together all aspects of a project, whether a completed legacy project or an ongoing investigation, the MRE community can be informed of what investigations have been undertaken, which have succeeded, what tools are available, and where gaps in information persist.
RM1: Tidal Current Turbine
The Reference Model Project was a partnered effort to develop open-source marine hydrokinetic (MHK) point designs as reference models to benchmark MHK technology performance and costs, and an open-source methodology for design and analysis of MHK technologies, including models for estimating their capital costs, operational costs, and levelized costs of energy.
Reference Model 1 (RM1) is a dual variable-speed variable-pitch (VSVP) axial-flow tidal turbine device, designed for the Tacoma Narrows tidal current energy resource site in Puget Sound, Washington. RM1 comprises a monopile foundation and a crossarm assembly to mount the two rotors. The cross-arm assembly is nearly neutrally buoyant so the attached rotors can be recovered and redeployed with a minimal amount of lifting crane capacity; therefore, the design minimizes the handling requirements during deployment and recovery, which reduces overall cost in all O&M activities including access to the power conversion chain (PCC).
The site deployment depth (assumed to be uniformly 50 m deep for modeling purposes) permitted a rotor diameter of 20 m. The dual rotors on each unit are offset by 28 m from each rotor centerline. The total width of the device from blade tip to tip is therefore 48 m. The rotor centerlines are submerged 20 m (one rotor diameter) below the free surface to reduce cavitation potential and are positioned one and a half diameters (30 m) above the seabed to reduce boundary layer effects that can cause velocity, turbulent shear, and loading asymmetries across the rotor. The tower height is 45 m, with an embedment depth of 15 m.
The cross-arm was designed to create a neutrally buoyant structure with sufficient strength to withstand thrust loads from the rotors, drag loads on the structure, and the nacelle (turbine housing) weight. The tower joint cross-arm connection uses a 1.5 m diameter central cylinder and two smaller cylinders as guides in the stream-wise direction. These guides help to align the cross-arm as it is lowered back onto the tower and secures the cross-arm into place. The tidal turbine tower was designed as an un-tapered (i.e., same diameter from top to bottom) steel pile with a three-guide cross-arm connection joint at the top.
The two nacelles, located at each end of the cross-arm, contain the complete rotor/drivetrain assembly. The nacelle housing, which was designed as a pressure vessel, has three major fairing sections— forward, central, and aft. The center fairing surrounds a center structure that connects the nacelle to the cross-arm. The center structure contains one access hatch topside and four smaller maintenance hatches on the underside. Forward and aft fairings are stiffened in the longitudinal direction to increase the strength of the pressure vessel.
The powertrain consists of the following key components:
Seal and bearing assembly – keeps the enclosure water-sealed and transfers the loads from the rotor-shaft to the nacelle.
Rotor support structure – transfers loads from the rotor to the center structure and cross-arm. The steel rotor support consists of six rectangular tubes connecting the two large annular flanges.
Seal and bearing flange
Center structure – connects the nacelle to the cross-arm and supports all of the nacelle’s weight.
The seal/bearing assembly houses the rotor driveshaft, bearings, and seal components. This assembly consists of the following components:
Seal gland – for the rotor shaft end.
Rotor shaft – contains both bearings and end seals on the rotor shaft.
Bearing package canister – centers and mounts the rotor shaft to the rotor support structure.
This table lists documents associated with the RM1: Tidal Current Turbine project, including reports written by the project team and/or papers that have used the project outputs or are closely associated with them. To find additional project outputs, including related papers, datasets, and codes, explore the RM1: Tidal Current Turbine page on PRIMRE.