Wednesday, 5 August 2015

John Guthrie, Energy Efficiency Manager, ABB writesImagine being able to accurately simulate the conditions of the world’s oceans, all from the comfort of dry land. Well that’s exactly what has been achieved at the University of Edinburgh thanks to some extensive teamwork between Edinburgh Designs – a world leader in hydrodynamic test tank equipment – and several divisions of ABB in creating the University’s FloWave Ocean Energy Research Facility.

Incorporating a range of ABB electrical and control equipment including servo drives and low voltage variable-speed drives, the 30 m diameter, 2.4 million litre test tank is a world first. Previously 1/100th scale prototypes would be used for controlled marine testing in the hope that a scaled up version would behave similarly in open water. FloWave allows for 1/20th scale models, at which engineers can now throw almost any wave or current imaginable.

While showing off FloWave’s crowd-pleasing wave formations and almighty splashes is a fun party trick, the serious business here is in using the facility to replicate real ocean conditions as accurately as possible. This is important to a wide range of different industrial sectors, but of particular interest in tidal energy generation research. Rather than spending a fortune on towing a full-scale model out to sea and hoping for the best, FloWave allows rigorous testing at the prototype stage on a scale that until now simply wasn’t possible.

Thanks to a long-standing relationship between Edinburgh Designs and ABB, we were the first people they turned to when it came to all things electrical on this project. Over the course of 25 years we’ve shared technology and engineering expertise in helping Edinburgh Designs push the boundaries of wave simulation, utilising the breakthroughs that ABB continues to make in motion control technology.

The £10.3 million project gave ABB a great opportunity to not only show the expanse of its portfolio but the skills of its engineering teams. The entire electrical and control system uses ABB components from variable-speed drives, servo drives and motors to circuit breakers, relays, switches, fuses and PLCs.

The test tank is encircled by a ring of 168 wave maker paddles. The design means the waves have no reflections and therefore allow multi-directional wave and current generation for model testing. Each paddle has a robust brushless AC servomotor, with the velocity, position and force feedback of each one being controlled by its own ABB MotiFlex e100 servo drive.

Because the impedance of water is extremely tricky to replicate, Edinburgh Designs designed their own control card in which they built high precision filters to correct the system to get the best match. As such the wave settle time is very fast for a large tank, allowing a quick re-start of a wave in a new direction. In normal operation the Edinburgh Designs computer system controls all this equipment to combine thousands of simple sine waves together into a fully controllable ‘random sea’ that is 99.9 percent representative of real sea conditions.

And all without having to get your feet wet!

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