ASL Environmental Sciences Inc. (ASL), of which ASL AQFlow is a wholly-owned subsidiary, has been carrying out successful flow velocity measurement programs in difficult ocean environments from the Arctic to the tropics with acoustic scintillation methods since 1977. ASL has been working in hydroelectric applications for over 20 years, since October 2000 as the ASL AQFlow subsidiary.

Early measurements at low-head plants

A prototype of the Acoustic Scintillation Flow Meter (ASFM) was introduced at Rocky Reach dam, Chelan PUD, in 1992.

The first model of the ASFM was used for flow studies at Fort Patrick Henry and Wheeler Dams, Tennessee Valley Authority, in 1997 and 1999.

The first production ASFM system was produced for the US Army Corps of Engineers (USACE), Portland District in 1998. Between 1998 and 2001, measurements with this system were conducted successfully at McNary, Bonneville, Lower Granite and The Dalles Dams.

ASFM Advantage™

In 2001, the second generation instrument, ASFM Advantage was released. It incorporated significant refinements, and has since been used effectively by:

• Nova Scotia Power - Canada
• Hydro Kennebec - USA
• US Army Corps of Engineers - USA
• Edison Sault Electric Company -USA
• BC Hydro - Canada
• Portland General Electric - USA
• Hydro Quebec - Canada
• Korea Water Resources Corp. - Korea
• Douglas County PUD - USA
• Electricité de France - France
• Gas Natural Union Fenosa - Spain
• Brookfield Renewable Power -Canada
• Compagnie Nationale du Rhone - France
• CEZ - Czech Republic

Initially the instrument was used for relatively short duration, one-time flow measurements. But because all ASFM Advantage instruments are located away from the flow, protected from debris impact, it was recognized that the technology is ideally suited for long-term, continuous flow monitoring.  

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ASFM Monitor™

Thus, in 2005, ASFM Monitor was introduced. This non-intrusive system, installed permanently in the intake, provides continuous, repeatable and reliable real-time monitoring of turbine discharge. Examples of its use may be found at:

• Turbine flow measurement in low-head plants –
  Hydro-Québec's and Corps of Engineers' experience
  with ASFM: continuous flow monitoring
• Field trial of an ASFM Monitor at Lower Granite December 2004 - January 2005
• The ASFM Monitor: A cost effective tool for real-time measurement of turbine discharge
  

Recent measurements at higher-head plants

Although the ASFM was initially developed for and used at low-head plants with no penstocks, its features make it an accurate, repeatable and cost-effective flow measurement method for higher head plants as well. Recent examples:

• Successful flow comparison test at GM Shrum Powerplant, 2016. The test compared two methodologies: acoustic time of travel (ATT) and acoustic scintillation (AS) (head> 180m)

  Flow Comparison Test at GM Shrum Powerplant

• BC Hydro case-study for measurement at G.M. Shrum, Northern British Columbia, 2012. (head > 180 m)

  Turbine flow measurement in intakes - a cost-effective alternative to measurement in penstocks

• Successful measurement at Slapy, Czech Republic, 2011.
  (head > 50 m)
  

  Discharge measurements at Slapy
  HPP – Comparison between acoustic scintillation and pressure-time methods

  
  
• Successful measurement at Kootenay Canal plant, British Columbia, 2009. (head> 80m)

  Acoustic Scintillation Flow Measurements in the intake at Kootenay Canal Plant
  
  Results of Kootenay Canal flow comparison test using intake methods

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