In a milestone for the fledgling marine power sector, Alstom’s 1-MW tidal turbine (Figure 6) generated power for the first time at the European Marine Energy Centre’s tidal test site in Orkney, Scotland.
|6. Streaming ahead. Alstom’s 1-MW tidal stream turbine began generating power for the first time at the European Marine Energy Centre’s tidal test site in Orkney, Scotland this March. Courtesy: Alstom|
Alstom recently acquired the company that had spearheaded development of the tidal stream turbine, Tidal Generation Ltd., from Rolls-Royce. The company had previously tested a 500-kW tidal turbine successfully. The 1-MW device is in Scotland as part of the Energy Technologies Institute–commissioned and cofunded ReDAPT (Reliable Data Acquisition Platform for Tidal) consortium project. Detailed testing and analysis in different operational conditions off Orkney will continue throughout 2013 over an 18-month period in order to further improve tidal power technology. The next step is to install pilot arrays prior to full commercial production, Alstom said in early March.
The tidal turbine consists of a three-bladed, pitch-controlled rotor, with a diameter measuring 18 meters (m); a standard drivetrain; and power electronics inside the nacelle. The 22-m-long nacelle is installed onto a separate seabed-mounted foundation and weighs less than 150 metric tons. Alstom said the turbine has other notable features, including that it is “easy to transport” in a single tidal cycle using small vessels. Also, it has an “intelligent” nacelle: “Thrusters rotate the nacelle to reflect the direction of the tide, managing ebb and flood tides seamlessly as well as maximising energy production.”
Making a marked departure from the traditional tidal barrage system, tidal stream turbines are massive stand-alone turbines that work much like wind turbines—but with a much higher energy density, because saltwater is 850 times denser than air.
The first commercial tidal stream turbine, a 122-foot-long inverted windmill with a nameplate capacity of 1.2 MW, dubbed the SeaGen, was installed in Strangford Laugh, a shallow inlet in Northern Ireland and began producing power in 2008. Siemens last year fully acquired that device’s developer, Marine Current Turbines. SeaGen’s performance has reportedly prompted Siemens to push two new SeaGen demonstrations. The 8-MW Kyle Rhea project in Scotland and the 10-MW Anglesey Skerries project in Wales are said to be in the advanced stages of development.
—Sonal Patel is POWER’s senior writer.