Wave simulation specialists hope to make offshore wind turbines in deepwater more financially feasible by researching the best way to stabilise the floating structures they are installed on
Academics from Manchester Metropolitan University in the UK have won a grant to develop computer models to test the best methods to stabilise and control the motions of a turbine and its support structure.
Manchester Metropolitan University reader in computational fluid dynamics Dr Ling Qian, who works at the Centre for Mathematical Modelling and Flow Analysis at the university and is the lead academic for the project said, “If you want to locate wind turbines far from the shore in a water depth of more than 50 m, a fixed-bottom turbine becomes a very expensive and challenging engineering project. We need to develop a floating turbine that works in deep water.”
Based on a code they have developed, Dr Qian and colleagues will use the university’s high performance computer cluster to run a computer simulation of waves interacting with a platform based on an existing design for floating support structures. The design consists of three connected columns 50 m apart, creating a triangular frame in which the turbine sits, keeping the majority of the mast above the surface of the water. Dr Qian said representative waves from the North Sea will be used in the computer simulation.
The Manchester Metropolitan University model will incorporate two proposed stabilisation measures, first testing with one and then adding the second. The first, a tuned liquid damper, is a U-shaped tube filled with water, which sloshes as the platform moves and acts as a counterbalance and helps absorb movement; the second is heave plates placed under the columns like the suspension in a car to suppress motions.
Dr Qian said, “Under extreme wave conditions such as during storms, floating platforms will undergo large movements. Sometimes this movement is dangerous and leads to system damage. We need to make sure the device can survive storms with large waves. On the other hand, for the wind turbine to operate optimally we also need to control its motion.
“To enhance technical viability and to drive the cost down, further fundamental research is still needed. In this project, we will look at some novel and cost-effective techniques to stabilise a floating system so it can operate in high sea states.”
Once Dr Qian and his team have carried out their computer modelling, a 1:30 scale model of the turbine will be tested in a wave tank with research partners at Ningbo University in China.
The 12-month project, ‘Passive Control of Wave Induced Platform Motions for Semi-submersible FOWTs’, has been awarded £124,000 (US$151,000). The funds came from the Supergen Offshore Renewable Energy Hub.