Pulsus tidal turbine trials complete
Norwegian Ocean Power's Pulsus prototype turbine
Norwegian Ocean Power has successfully completed the initial trials on its Pulsus horizontal-axis spiral-design tidal turbine. These trials were primarily aimed at testing the bearings of the turbine which are a critical part of the unit.
Norwegian Ocean Power tow-tested the tidal turbine whilst measuring the loadings on the bearings and the load in the turbine blades. The work was carried out at Drammensfjorden in Norway where the dynamic test on the composite structure and bearings was performed.
The engineering, design, and the bearing itself was supplied by Vesconite Bearings, while Norwegian Ocean Power looked at the deflection and the bearing’s ability to absorb structural vibration resulting from the turbulence that can be associated with tidal turbine operation.
Kent Thoresen, the technical director at Norwegian Ocean Power, said, “We crossed a boat back and forth in front of the turbine to find data on the behaviour in turbulent streams. The bearing performed flawlessly, and had no problem handling sustained loads, shock loads or vibration. We were hoping to separate out any vibration from the structure and the trials were successful in showing this. There are many failed projects in the tidal energy industry due to turbulence that causes vibration and uneven force distribution. That is why it was important to fully test our unit in real sea conditions.”
“The structure bends and flexes with tidal currents, which can produce significant turbulence and considerable upward and sideward forces, so the testing of uneven forces is a key part of testing for this tidal-turbine. The thrust bearings moved backwards and forwards and eliminated the vibration as planned, which might have otherwise led to a systemic failure.”
The 0.5metre diameter Vesconite bearings which were installed on each end of the horizontal unit, also performed well in their ability to absorb vibration. They were chosen after the testing of various competing products that were less flexible and exhibited dry-run problems.
Norwegian Ocean Power has developed a tidal current turbine based on the Darrieus turbine design with one moving part that drives a variable speed direct drive generator, which in turns produces electricity. The company is focused on the development of its first commercial unit, planned to have the capacity of 350kW. The size of the turbine will be approximately 12 by 6 metres, with the ability to operate at water depths from 15 metres.
Norwegian Ocean Power is the owner, financer and developer of the innovative turbine technology, which will be installed in the sea off Norway next year and begin commercial production of 1TWh of energy per year for use in Norway. The intention is to start production on several turbines in 2017 and 2018, with the UK being the most likely first market for these turbines.
By Dag Pike