Motion Control & Drives


Making waves

October 2009 Motion Control & Drives

A project for developing the use of wave energy for the generation of electricity features AC drives from Control Techniques. The drives are a key feature in wave-

power projects around Europe.

Inverness-based Wavegen, part of Voith Siemens Hydro Power Generation, is a wave energy company dedicated to the development of marine renewable energy technology.

On the Isle of Islay, off the west coast of Scotland, Wavegen has an inclined oscillating water column (OWC) generating facility that is used both for generating power and for testing new designs of Wells turbine generators.

Two 250 kW counter-rotating turbines have been generating power for several years at this ‘Limpet’ (land installed marine powered energy transformer) unit, which utilises the power of a surge-dominated wave field adjacent to the shore. The water depth at the entrance to the OWC is typically seven metres and the air chamber is designed to maximise the capture of wave energy and power output.

Now, one of the turbines has been removed to provide Wavegen with a test-bed for a new design of small turbogenerator that can be incorporated into breakwaters, coastal defences, land reclamation, port walls and community power schemes. These are a fifth generation of Wells generators and incorporate all of the learning and cost-reduction gained from development and practical operation of the Limpet plant.

“It was crucial that we selected the right drive system to accommodate both our changing needs during the development process and the requirements of future customers of these breakwater generators,” explained Dr Tom Heath, engineering manager at Wavegen. “We considered five drives suppliers and Control Techniques proved to be a clear choice for several reasons,” he says. “The over-riding factor was the facility to program the drives in a high level language. It proved to be very easy to adapt the SyptPro control language used by Control Techniques – and their willingness to give us total access to the drive functions proved crucial.”

Two 32 kW Unidrive SP drives are fitted; one to control the turbine speed, the second running in regenerative mode to feed AC power to the grid. Both are fitted with SM-applications modules to provide powerful on-board programming of the system and the first, additionally, has an Ethernet communications module. Because of the high-level of I/O required – some 20 channels, monitoring temperature, speed, chamber pressure and pressure drop across the butterfly valve etc – additional I/O is provided locally with a Beckhoff unit.

Wave motion drives air up (or down) the inclined water column as can be seen in the diagrams. In turn this drives the bi-directional flow, uni-directional Wells turbine that runs at up to 4000 rpm and which is connected to an induction generator.

Pressure transducers in the chamber feed the RMS pressure back to an SM-applications module via the Beckhoff unit. The program calculates the optimum speed for the turbine and the unit can be started. The Unidrive SP motors up the turbine to the optimum speed and then switches from motoring to generating mode, allowing the low-inertia turbine to drive free, with the air pressure, but limiting its maximum speed. Then, using a five-minute moving average of the chamber air-pressure, the maximum turbine speed is adjusted every 30 seconds to give an optimum output from the Wells turbine installation.

Normally, the Wells turbine runs 24 hours a day in fully automatic mode, except when very high sea states require throttling back by using the butterfly valve.

“The Unidrive SP AC drives, with their Ethernet connectivity, have proved ideal during our development phase. In the future, this will be equally important so that we can provide our clients with technical support via the Internet,” concludes Heath.

For more information contact Bill Tedd, Control Techniques, +27 (0)11 462 1740, bill.tedd@emerson.com, www.controltechniques.com



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Sawmills and sugar mills underpin growth for SEW-Eurodrive
October 2019, SEW-Eurodrive , Motion Control & Drives
Ageing sawmills and sugar mills in KwaZulu-Natal represent a significant growth opportunity for SEW-Eurodrive to introduce its latest energy-efficient technology. This is an increasing trend as both the ...

Read more...
Smart devices for Ex areas: Unbelievably simple mistakes that prevent control.
September 2019, Michael Brown Control Engineering , Editor's Choice, Motion Control & Drives
I am often astounded by finding really basic problems with controls in plants, which have operated that way for years. These problems are so basic that one can only wonder at how these controls could ...

Read more...
DLM V-Drives
September 2019, Dupleix Liquid Meters (DLM) , Motion Control & Drives
DLM V-Drives control the latest generation of permanent magnet and standard induction motors. DLM offers the AMC (advanced motor control) and EPC (efficient pump control) V-Drives, which are available ...

Read more...
Complete drive solutions to boost efficiency and cut costs
September 2019, SEW-Eurodrive , Motion Control & Drives
The importance of the sugar industry in KwaZulu-Natal to SEW-Eurodrive as a key growth area for its complete drive solutions was underscored when it exhibited at the Congress of the South African Sugar ...

Read more...
RS announces drive controller kit
September 2019, RS Components SA , Motion Control & Drives
RS Components has announced the launch of the K4 Drive System Development Kit (K4DSDK) from ebm-papst, one of the world’s leading manufacturers of high-efficiency fan and motor drive products. Targeting ...

Read more...
Feed mill project relies on SEW-Eurodrive
August 2019, SEW-Eurodrive , Motion Control & Drives
SEW-Eurodrive has supplied 120 geared motors to Dalein Agriplan for a customised 100 tph feed mill for a major beef producer in the Free State. This is not only one of the largest single projects undertaken ...

Read more...
Dust solutions for conveyor systems in bulk handling
August 2019 , Motion Control & Drives
BLTWorld works closely with ScrapeTec, to offer advanced solutions for conveyor systems used in the handling of materials with excessive dust. “AirScrape, TailScrape and DustScrape have been developed ...

Read more...
Case History 167: Test your analytical capabilities
July 2019, Michael Brown Control Engineering , Editor's Choice, Motion Control & Drives
Answer to the question at the end of Case History 166 (www.instrumentation.co.za/8690r) In the last Case History article, I suggested you try and see what was not so good about a level control, which ...

Read more...
BMG drives sewage and effluent management
July 2019, Bearing Man Group t/a BMG , Motion Control & Drives
BMG supplies a range of drives designed specially for optimum efficiency in sewage treatment applications. “Nord drives, which consist of Unicase helical shaft mount geared motors, have special features ...

Read more...
Bauer motors for water treatment plants
July 2019 , Motion Control & Drives
According to Bearings International (BI) electric motors product manager Lewis Hiepner, the arduous operating conditions at water-treatment plants mean that the motors specified not only have to be high-efficiency, ...

Read more...