Partrac, the marine data acquisition experts, has completed the first turbulence survey for the Carbon Trust-managed Turbulence in Marine Environments (TiME) project. This is the first time that a survey has been designed specifically to measure turbulence using different methods and technologies so that each can be evaluated, and turbulence can be mapped across a tidal energy development site.
The survey was undertaken in the Sound of Islay and was designed by Partrac with project partners, Ocean Array Systems, ABPmer, and ITPower. Innovative turbulence measurement instruments were provided by Rockland Scientific International (RSI) in Canada.
The survey included four standard ADCP units, and one advanced five beam Nortek AD2CP unit, each positioned on the sea bed. Three of the locations were at positions where tidal turbines will be installed. A RSI ‘Nemo’ turbulence mooring was also deployed so that turbulence data could be measured at turbine hub-height. The measurements were taken over a 28-day period during April and May. In addition, a VMP-250 (vertical micro-profiler) was used over two days to gather around 50 profiles of turbulence in the water column. All instruments were deployed to meet industry best practice with the ADCP pitch and roll parameters at less than 5 degrees for the duration of the monitoring period. Data was recorded at a high frequency, which is required to understand turbulence, and resulted in over 700,000 data records per instrument. All equipment was retrieved successfully.
Peter Wilson, a Director and co-owner at Partrac, said, “This is a very exciting project. This is the first time that such a large survey has been designed to specifically measure turbulence using a range of acoustic and non-acoustic measurement techniques. To get data at hub height is a first in such tidal currents and to be able to map turbulence across a development site will be invaluable to developers.”
The data collected has now been post-processed by Partrac and RSI and is being provided to the partners for the next stage in the project. ABPmer is undertaking resource characterisation, Ocean Array Systems is providing turbulence characterisation and hydrodynamic analyses, and ITPower is contributing their knowledge of engineering design and device performance.
The next survey deployment is planned for the Inner Sound of the Pentland Firth at the end of the summer 2014.
ABPmer has already successfully created and undertaken initial runs of high resolution (<20m) numerical tidal models of both the Islay and Inner Sound sites. These models, giving an accurate representation of the mean flow at the survey sites, have played a vital part in the detailed planning of the two surveys, and will later be used to understand how turbulent features may be accounted for in tidal resource modelling.
The TiME project was announced by the Scottish Energy Minister, Fergus Ewing, in February, when it was awarded funding from the Scottish Government’s Marine Renewables Commercialisation Fund (MRCF) Array Technology Innovation Programme for measuring and evaluating turbulent effects in tidal arrays in Scottish Waters. This MRCF project is being managed by the Carbon Trust.
As the tidal industry moves toward development of arrays, the current limited understanding of the effects of turbulence on loading, structure lifetimes and actual energy yield presents significant risk to stakeholders. This research project will ultimately deliver a unified framework for measuring, classifying and predicting the effect of turbulence on resource assessment, device design/operation and array yield.
Press Release, July 22, 2014