Measuring buoy marks the wind of change

A buoy-mounted wind measurement system to locate the best sites for offshore wind farms is being developed by a consortium including Qinetiq and Npower Renewables.

Called SeaZephIR, the system is based on light detection and ranging technology (LIDAR), which is used in police speed guns and works on the same principle as radar.

The device transmits light in the infrared frequency range, which interacts with a target object and is reflected back to the system, said Ian Locker, business development director for renewable energy at Qinetiq.

When the light hits a moving target the wavelength of the light reflected is changed slightly — an effect known as the Doppler shift. By measuring the movement of tiny dust and pollution particles carried along by the wind, engineers can measure the speed of the wind itself, said Locker.

The renewables industry currently uses fixed meteorology masts, which are complicated to install and require planning permission. Also, the height of wind turbines is increasing, up to 150m for 5MW devices. As meteorology masts are shorter, renewables firms are having to measure the wind at a lower height and then use modelling techniques to calculate the speeds higher up, he said.

‘Because this system can focus up to a height of 150m, it can measure the wind speed at the height of interest to the industry — the wind turbine height.’

Unlike fixed masts, the device can also be moved around the area under consideration, or to different sites, he said.

The three-year project, which also includes Trinity House Lighthouse Service, is partly funded by the DTI.

The system has already been tested on land, but has not yet been proven in an offshore environment, where the movement of the buoy with the waves could interfere with the measurements. So the team will spend the next year integrating the technology into the buoy and developing an electronics system to measure and compensate for the movement of the waves.

The system will then be tested offshore for the next two years.