Beam Reach

Race Rocks tidal current power project

As multiple agents in Western Washington begin the process of harnessing the tidal currents of the Salish Sea for generating electricity, it’s worth a close examination of what’s been learned by a pioneering tidal turbine project associated with the Race Rocks Ecological Reserve/Marine Protected Area. Through a partnership between Pearson College of the Pacific (288 students from 28 countries study International Baccelaureate) and Clean Current Power Systems (Vancouver, Canada), a project was initiated to provide renewable energy to the marine station and lighthouse.

Today, a tidal and solar power system has replaced the twin 15kW diesel generators that provided electrical power (and noise, air pollution, environmental risks) during most of the 20th century and much of the history of the Race Rocks reserve (established in 1980). I assume wind was judged inappropriate because so many sea birds nest and rest on the Rocks.  I’m still just learning about the details, but wanted to share some notes and frame-grabs I took while watching a nice overview video of the Race Rocks tidal power project.

My overall impression is the turbine is big.  Approximately 4m in diameter, the ~65kW turbine is designed to be scaled up to 1MW (presumably for future commercialization by CCPS). The forces exerted on the support column during the maximum 3.35 m/s tidal flows must be tremendous.  A cool innovation I didn’t anticipate is that the blades are designed to turn in current from opposite directions.  This means that the whole turbine assembly doesn’t have to rotate on the support column (like wind turbines do).

It’s hard to find measurements or engineering data on the blade rotation rate.  Quoting from generic references about tidal turbines on the EIA page, “The blades themselves rotate quite slowly relative to hydroelectric and wind turbines, namely a few revolutions per minute depending on current speed, blade curvature and size but always to maintain a blade tip speed of less than 7m/s (when cavitation is likely to occur)” and typical rotation rates are “10-20 rpm.”  For a blade radius of 2m, the tip velocity would be ~4m/s at 20rpm and ~2m/s at 10rpm.  Given the arrangement of guided vanes I certainly wouldn’t want to swim through it at those rotation rates… but maybe a fish would do alright?

Funding for the project has come from Encana (natural gas and oil company’s Environmental Innovation Fund) and Sustainable Development Technology Canada (non-profit foundation created by Canadian government; Vicky Sharpe).

Chronology:

• Late 2005: preparatory (concrete) work on island for cable route and battery storage
• Jul 2006: Drilling complete (after 3 weeks), piling installation continues
• Sep 2006: Installation of turbine; hydraulic and electrical performance testing begins
• Dec 2006: Testing complete; cables connected to shore storage; Summary Report on Environmental Monitoring final draft submitted
• Apr 2007: Turbine raised to repair bearings
• Oct 2008: New turbine with stainless steel bearings, lubrication system, and reinforced augmenter duct.

Artists depiction of installed turbine

Technical details (these are surprisingly hard to find… values to be filled in are in italic):

1. located ~100m from Island, ~15m depth, ~20m of water
2. The top of the turbine is at a mean depth of 10m, or ~5m below MLLW; thus the whole assembly reaches about 10m off the seafloor.
3. post diameter?
4. turbine and funnel dimensions? (~3m diameter, but not sure if that’s augmenter or blades)
5. power and voltage (what function of current speed?)

Diver guiding generator unit onto post

The generator sans cowling

Clean Current Power Systems staff interviewed in video

• Russel Stothers
• Glen Darou
• Virgil Young (aerospace)
• Chris Gora

Pearson College staff interviewed in video

• Gary Fletcher
• Dave Skilling

Other projects to keep an eye on:

• 1.2 MW project in northern Ireland
• Tidal prospecting by Snohomish County
• Pilot project planning by Tacoma Power
• Monitoring by Biosonics of the Verdant Power turbines in the East River, NY