On the pulse
Tanya Weaver talks to SgurrEnergy’s product development
manager about the company’s next generation Lidar technology
Lidar (light detection and ranging) is a mature remote sensing technology that has been used in a wide variety of applications, from physics and astronomy to military and law enforcement and, more recently, wind power applications. Compared to fixed anemometry masts, which have historically been used to study wind patterns and monitor energy yields, this laser-based measurement technique performs measurements in a more flexible and economical way. A laser beam is emitted from the device and the Doppler shift of the light back scattered by microscopic airborne particulates carried by the wind is measured. This indicates the wind velocity in the line of sight. Combining these measurements in multiple directions gives the wind velocity vector.
Experience
SgurrEnergy, an independent multi-disciplinary engineering consultancy specialising in renewable energy, recently introduced its next generation Lidar technology - Galion. Having been an early adopter of the technology, SgurrEnergy used its experience to create a ‘wish list’ of features it wanted to bring to market in its own Lidar device. “This ‘wish list’ combined with SgurrEnergy’s significant expertise in the wind power market meant that we were uniquely positioned to spec this new product. We sought to alleviate the limitations found with existing Lidar models,” comments Graham McKinlay, SgurrEnergy’s product development manager. “Our joint venture partner was able to provide the best technology for this purpose based on proven technology used for atmospheric science research.”
Compact
As McKinlay argues, the Galion offers a host of benefits over current Lidar devices on the market - not least of all its compactness measuring just 86cm x 90cm x 66cm. “The optimum wind power lidar device must be compact, highly portable, light, silent, discrete, reliable and robust in addition to all its advanced scientific and technological core features. Galion is the result of all these features,” he comments. “It’s self levelling feature is particularly useful for rapid deployment. Currently, no other lidar on the market has this feature.” Other features include an all-sky scanning capability allowing multiple wind turbine locations to be surveyed from a single deployment site as well as a beam steering capability with pulsed laser technology.
This steerable beam is one of the most significant advantages of the Galion. Many wind farm sites are on complex upland terrain where wind flow is not uniform in its volume and many previous beam scan regimes have resulted in measurement ambiguities and bias. “The steerable beam allows the measurement of the wind at multiple potential turbine locations from a single deployment. This reduces the need for modelling as real data can be captured and used and so reduces uncertainty,” explains McKinlay. “The full steerable beam also allows scan geometries that are more suitable for complex terrain. This is ideal for wind farm development locations. Galion has an unrivalled combination of range and resolution.”
Distance
Another principal advantage of Galion is the fact that SgurrEnergy decided to use a pulsed laser as opposed to a continuous wave. “Continuous wave lidar signal is prone to contamination if the strength of the return signal varies with distance to a greater extent than the sensitivity of the device, for example, as a result of clouds or low mist,” says McKinlay. Although, both pulsed and continuous wave Doppler lidar have been developed in parallel over the past 40 years the practical continuous wave systems are limited to ranges of less than 100m whereas pulsed devices can operate to ranges of many kilometres. “Pulsed Doppler devices achieve range resolution by combining a pulsed transmitter with a time-of-flight measurement. The range resolution is constant with range and non uniform atmospheric backscatter does not cause any problems,” he comments.
Operation
Galion can easily be deployed by two people without the need for specialist equipment or extensive training. Once connected to the power supply, it starts collecting data instantly. All data is captured and stored on the system’s onboard computer, with the operator having access to both real time and historical data. “Hundreds of gigabytes are installed and so the memory effectively imposes no restriction on operation,” comments McKinlay. “All data can be accessed remotely via a secure internet connection by GSM or satellite.”
Galion is currently undergoing a series of independent tests at reputable European centres including Riso, the National Laboratory for Sustainable Energy at the Technical University of Denmark. The results of these tests, which are expected to be completed in March 2009, will be published and in addition made available on SgurrEnergy’s website. From then, Galion will exclusively be available from SgurrEnergy for sale and hire.
Currently, there is a strong demand for Lidar products and, according to McKinlay, there has been a lot of interest in Galion since its launch. “Interest shown in the product since launch allows us to be confident in its success,” he comments. “Galion represents the next generation of Lidar technology and overcomes the final hurdles with utilising Lidar for wind resource assessment. It is a pioneering piece of technology that will bring many benefits to the wind power industry.”
www.sgurrenergy.com
SgurrEnergy will be exhibiting at EWEC in March 2009 and Galion will be on display on stand 1007 for all visitors to take a look at.
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