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SODAR and LIDAR - RSD

LIDAR and SODAR Remote Sensing Devices

In recent years, Remote Sensing Devices (RSD), such as LiDAR or SODAR, have gained more and more reliability, positive response and acceptance from the wind community; mainly driven by the fact that hardware costs were dropping, and the data accuracy and device reliability have improved significantly.

It has been shown that RSD measurement uncertainties, compared to measurements with First Class Cup Anemometers, in some cases (non-complex terrain), were even lower than the uncertainty of the Cup Anemometer measurements. However, in such cases it is not possible to determine at a first glance “which device is measuring more accurate”, since the values are lower than the uncertainties of the measurement devices themselves, and hence diminish in the uncertainty budget.

Nevertheless, extreme precaution must be taken in complex terrain, as the uncertainties are significantly higher for RSD. If RSD technologies are used, it should be done in parallel to a reference measurement mast installed.

ProfEC Ventus offers A-Z performance of different RSD-supported measurement campaigns, tailor made to the needs, means and expectations of our Clients. The measurement data are processed and evaluated in accordance to our accredited services, yielding in a bankable measurement report with accredited conclusions drawn.

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Remote sensing device (RSD) - LIDAR Wind Measurement Technology & SODAR Wind Measurement Technology

Meteorological as well as atmospheric research and investigation historically often depend on the ability to accumulate precise data on the characteristics and the development of wind flow in a specific geographically restricted area over extended periods of time. Research and investigation hence are the most common applications for wind resource measurement hardware and assessment technologies and practices.

More recently such technology has been applied to wind energy. Wind energy knowadays is the most common source of renewable electricity generation globally. To further develop wind projects and while warranting spatial efficiency, it is often important to accumulate and evaluate data on the local and regional characteristics of wind and atmospheric fluid dynamics.

Needs for different analyses

Different innovative technologies have been developed to serve analytic needs, and different products have emerged to fill different niches. Wind measurement technology in the past decades can roughly be divided into two categories.

First, there are metal equipment and lattice masts, which are costly to set up and may require construction permits. But they are very rugged, stable and insensitive. These are mainly used to assess the viability of high value and long-term investments; such as wind parks. Second, there is relatively light and inexpensive plastic equipment and (telescopic) tubular masts, used for shorter-term undertakings, and which have not traditionally been able to compete in precision and durability.

Remote Sensing Devices (RSD)

More recently within the last 10 years a newer technology category has been evolving quickly: Remote Sensing Devices or simply RSD. They are used to assess the wind flow vectors horizontally and vertically, at different highs above ground level. And they are often portable, relatively light devices, best suited for inaccessible terrain and used to accomplish, within a shorter-term assessment, a longer-term wind mast measurement campaign. They are usually designated for assessment in projects whose duration may vary between three and twelve months, but rarely exceeding one-year measurement term.

Due to technological innovation, portable Remote Sensing Devices (RSD) have significantly increased effectiveness and precision, and are increasingly capable of sophisticated, modern wind feature analyses. At the same time, these devices have become increasingly cost-effective and more widely available. Due to this technology learning curve, the portable Remote Sensing Devices (RSD) are becoming more widely accepted and can be applied to an increasing array of uses, in many situations being accepted by banks, investors and project developers as eligible, precise wind measurement device. At the latest since the RSD are addressed in relevant IEC norms (mainly to be mentioned 61400-12-1 Ed.2 2017 and the upcoming 61400-50-3), RSD technology is becoming a commercially viable alternative for met mast technology in many situations.

LIDAR Wind Measurement & SODAR Wind Measurement

Remote Sensing Devices (RSD) are further divided into two device categories based on their functioning: LIDAR wind measurement and SODAR wind measurement. Both devices operate on similar logic, as they are based on detecting movements caused by the air flow, i.e. wind. But they also have significant technical differences that set them apart.

LIDAR, short of Light Detection and Ranging, is a remote sensing device that measures wind vectors based on laser beams that are scattered by the particles in the wind. LIDAR wind measurement technology is also widely used in other fields of technology, such as robotics.
On the other hand SODAR, the abbreviation of Sonic Detecting and Ranging measures wind vectors based on sound waves. SODAR wind measurement devices measure wind features with the Doppler effect, by assessing how particles in the wind disperse sonar waves in the air.

In both cases the functioning is similar to radar (radio detection and ranging), as it detects the time it takes rays of light (LIDAR) or waves of sound (SODAR) to travel there and back, in order to measure distances, velocities, and hence dimensional vectors.

LIDAR
SODAR