Fulcrum3D Sodar, a superior design

Technology

The Fulcrum3D Sodar measures wind speeds, direction, and inflow angle in 10m range bins from 40m to 200m, with optimal data capture in the range 50m to 150m which aligns with the operating range of modern wind turbines. Each range bin also provides a data quality assessment, and each 10 minute sample also provides other measurement statistics available on board.

The Fulcrum3D Sodar is unique in its design.

  • A compact-beam mini Sodar which uses mechanically fixed beam angles to maximise accuracy and reliability of results. The beam geometry is optimised for use in both flat and complex terrain where traditional Sodars lose accuracy due to the variable wind vectors over the sensed air volume.
  • The physically fixed beam angles eliminate errors introduced in electrically steered Sodars, where the steering frequency must be adjusted to take into account local temperature effects. In addition to eliminating temperature related errors, this minimises side lobes and therefore allows for a more compact system.
  • The Fulcrum3D Sodar design also allows multi-beam sampling where all three beams can be sampled simultaneously. This effectively triples the sampling rate and can significantly improve data accuracy and availability.
  • The Fulcrum3D Sodar is software defined and fully flexible – all the data analysis smarts are on the server-side rather than on-board the Sodar units, which means the operating algorithms and software upgrades can be remotely applied to ensure optimum results.
  • Auxiliary sensors can be added and operating frequency changed to allow multiple units to be co-located without interfering with each other.

The Fulcrum3D Sodar is a portable unit, mounted on a standard box trailer, and powered by its own low-maintenance solar / battery system.  It is supplied with on-board remote telemetry, meaning that it is a set-and-forget solution which reliably provides data to your desktop.

By covering the entire turbine area, Sodars have a significant advantage over traditional wind monitoring equipment using masts. Check out the other benefits here.

How it works

A Sodar works by sending out a sound pulse (beep) and listening to the returned sound signal as it’s scattered back towards the Sodar by atmospheric turbulence. You can listen to the sound pulse here – don’t forget to turn your speakers up! The principle is like radar where a radio wave is transmitted by the radar and radio-frequency echos are returned from objects like planes or ships. The 3 sound beams of the Fulcrum3D Sodar allows a 3 dimensional wind vector to be measured.

After the pulse is transmitted, the Sodar begins recording the returned sound signal and various filtering techniques are used to eliminate false data, background noise, errors introduced from rainfall and other factors.  The wind speed, direction, inflow angle, and height range are then calculated based on:

  • the time delay from when the beep was transmitted to when it was received, which indicates the sampling height (based on the speed of sound)
  • the change in frequency between the transmitted and received sound on each sound beam, which is caused by the wind vector along each beam axis (due to the Doppler effect)
  • the known angles of the 3 sound beams, together with the wind vector along each beam, which is interpreted to produce a 3D wind vector

This wind vector is then translated into wind speed, direction, and inflow angle in each height bin. More complex analysis allows the wind speed standard deviation and turbulence index to be calculated. The Fulcrum3D Sodar transmits a sound pulse approximately every 1.5 seconds, giving a large number of samples which are then analysed to generate 10 minute statistics.

How a sodar works

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