To further the development of tidal energy capturing devices, the University of Washington, Applied Physics Laboratory (APL) began the Marine and Hydro-Kinetic (MHK) energy project. The project will utilize an instrumented test bed on which a variety of tidal energy turbine designs can be evaluated.
The R/V Henderson, operated by APL, will serve as the host vessel for the project. The vessel’s twin hull design, open forward deck, and large protected laboratory space make it ideal for the project. The relatively clean flow at the forward end of the pontoons provides an accessible and safe area to deploy the test bed for turbine testing. As part of this effort, the development of a handling system test bed concept was required.
Innovative Handling Systems
The APL chose our firm to develop a test bed and handling system concept for the project because of our strong reputation for innovative handling system concepts.
The test bed structure has to accommodate the easy attachment of single or multiple cross-flow turbines or an axial flow turbine. The structure must withstand flows up to 6 knots. In addition, the test bed structure should have minimal drag to reduce system loads. The handling system has to allow for safe, rough weather, and hands-free operation. It must provide safe stowage of the test bed while the vessel is underway. In addition, the concept should be cost-conscious by minimizing the necessary modifications to the R/V Henderson.
One of the strongest considerations in our design was turbine access. A design priority was to ensure that the evaluation team would be able to make adjustments to the turbine and perform maintenance in a wide range of weather and sea conditions without having to travel back to the dock. To do this, all parts of the turbine must be at deck level and within easy reach when the test bed is recovered.
With all the project constraints in mind, our team developed a vertical launch and recovery test system concept. The system consists of three main structures: a hoist tower, a lifting frame, and a test bed. The hoist tower is a fixed frame mounted to the ship which is used to guide and handle the lifting frame. The lifting frame is raised and lowered by an electric-powered winch system mounted on the tower frame. In addition to mounting the test bed, the lifting frame also houses the turbine load cells.
Like an elevator, the vertical launch and recovery system lowers the test bed into the water for testing and lifts it above the deck for transit and stowage. The simulation below shows the simple deployment process.
Two different types of turbines that can be installed on the test bed are shown below.
After the APL team approved the concept, Einhorn Engineering proceeded with engineering analysis. We needed to optimize the weight of the system while ensuring adequate structural strength. With this in mind, the tower space frame design was assessed using both finite element analysis as well as classical mechanics analysis techniques.
Seeing the project through
We have completed most of the fabrication drawings and we look forward to completing the remaining engineering work. Following this, our team plans to support the construction of the handling system and subsequent installation on the Henderson. As the design and engineering phase concludes, Einhorn Engineering is confident the test system will meet or exceed the requirements of the MHK turbine test program and we look forward to supporting the construction phase of the project.