July 15, 2015 | by Evan Osler | Engineering + Technology, Wind Plant Optimization, Wind Resource Assessment

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This article first appeared on RenewableEnergyWorld.com.

Renewable NRG Systems has sold, serviced, and supported wind Lidars throughout the world since early 2009. Our Lidar customers are primarily engaged in the business of wind energy, and they utilize these exciting tools for a variety of purposes, including commercial wind resource assessment, power performance testing, turbine output optimization, and calibration of wind forecast and turbine wake models. Despite the maturation and widespread use of Lidars in the wind energy industry, we continue to hear common misconceptions related to the technology. This list contains the 10 most common myths about wind Lidar and the true story behind them.

1. The wind energy community has been slow to adopt Lidar technology.

False! Wind Lidars of all types (ground-based, nacelle-mounted, vertically profiling, 3D scanning, etc.) are as a general trend being adopted quite rapidly by the wind energy industry. Today more than 1,000 wind Lidars (i.e. Lidars that measure the wind) are being used globally for wind energy applications alone—a number that has roughly doubled in the past three years. We estimate that at least 80% of large wind farm developers and operators in North America are now utilizing wind Lidars in some capacity within their businesses. On an aggregate basis, the adoption has therefore been quite rapid, and this trend is expected to continue.

2. When it comes to wind energy applications and benefits, all remote sensing technologies are interchangeable.

False! There are a host of remote sensing products available to the wind energy industry today that serve a wide range of applications at a variety of price points. Lidar and Sodar are fundamentally different technologies, and industry acceptance of Lidar specifically seems more than ever to be weighted towards particular Lidar types and brands rather than to all such devices for sale with “Lidar” in their name. The lesson, as always, is to do your own research and consult unbiased, independent experts when considering the acquisition of a Lidar system for wind energy purposes.

3. Ground-based Lidars are not fully “bankable” for pre-construction wind resource assessments.

False! Certain ground-based Lidars are in fact fully “bankable” for this purpose, with independently assessed measurement uncertainties on par with those of industry standard, calibrated cup anemometry. As noted under Myth #2, it is important to assess the relative bankability of a specific Lidar system rather than assume that all systems are equivalent in this regard. Furthermore, bankable data can only be collected when the Lidar is used in a proper manner, following best practice guidelines. Just as a met tower with improper placement or configuration will provide low quality data, so will a Lidar sited or configured incorrectly.

4. Lidars are highly technical systems and therefore complicated to use.

False! While wind Lidars are highly technical systems as a general rule, most are actually quite easy to use and only a day or less of training is required to convert a new user into a highly competent one. This is not to say that all Lidars are easy to use; there are exceptions to every rule, and in this case, the exceptions are generally older vintage systems and newer systems that scan in three dimensions. 3D Scanning Lidars have unlocked amazing new potential in wind measurement but also require significant expertise on the hardware and data analysis side.

5. Ground-based Lidars consume a lot of power and therefore require bulky, fossil fuel-burning, off-grid power supplies with high maintenance and refueling costs.

It depends! Our primary ground-based Lidar, WINDCUBE v2, actually consumes very little power most of the time (45 W nominal), and it is relatively easy to power off-grid with PV panels and batteries alone. In very cold and/or cloudy environments, different solutions might be recommended including propane fuel cell power, which operates quietly and very efficiently. That said, our customers have deployed WINDCUBEs as far north as central Ontario on 100% PV solutions with good success. This is not to say that all ground-based Lidars have low power consumption and can be practically powered by PV. It is important to consider the potential power supply sizing and cost as part of the overall cost of ownership of a ground-based Lidar, as even small differences in power consumption can lead to large differences in power supply system design, service, or refueling intervals.

6. Lidars are fragile.

False! Commercial Lidars are not fragile devices, any more so than other ruggedized, high-end electronics designed to work outdoors. We advise our customers to treat their wind Lidars like expensive digital cameras—with proper care but without fear!

7. Nacelle-mounted Lidars are primarily used for turbine control.

False! The majority of nacelle Lidars installed today are not actually used to control the turbines they are installed on. We expect that major turbine OEMs will incorporate Lidar technology into future turbine designs to decrease fatigue loading and therefore drive large reductions in material costs. However, permanently installing Lidars on already operating turbines for control purposes may not deliver as much benefit. The primary benefits of retrofitted nacelle Lidars are realized within a short period of installation: accurate turbine performance assessment and static yaw misalignment detection and mitigation.

8. Ground-based Lidars are used to reduce the duration of a pre-construction wind resource assessment campaign and will replace met towers someday soon.

False! There is no evidence to suggest that the duration of a wind resource assessment campaign can be shortened by utilizing ground-based Lidar technology in addition to, or instead of, met towers. Lidars are deployed in concert with met towers as a means to reduce vertical (shear) and horizontal (topographic) measurement and energy estimation uncertainty. There is no evidence to suggest that Lidars will replace met towers any time soon either, because met towers still provide a highly economical, well-understood, and widely trusted measurement method with built-in redundancies, while Lidars are easy to relocate within projects and between projects. Both met towers and Lidars have unique advantages compared to one another that make them likely to serve as complements for years to come.

9. Lidars are not yet useful for power performance testing.

False! Some Lidars are very useful for power performance testing. Forthcoming revisions to the IEC 61400-12-1 standard on power performance testing will codify the use of remote sensors for this purpose for the first time, as a complement to short masts in simple terrain sites for calculation of rotor equivalent wind speed (REWS). That said, Lidars are already being used in many power performance tests, some of them contractually-based and others for operational assessment purposes only. Many savvy wind farm operators have discovered that operational power curve testing is a worthwhile and cheap investment compared to undertaking a formal IEC test, and it may yield similar if not more valuable results.

10. Lidars are just too expensive.

False! Lidar systems are available at a wide range of price points today. Generally speaking, there is a good correlation between Lidar price and level of performance and industry acceptance. Even the most expensive Lidars will provide a highly positive return-on-investment if they are used smartly, and the ROI will often be a lot quicker than for lower cost systems due to greater capabilities and higher industry acceptance. When the cost of purchasing tall met towers is considered along with the cost of relocating them multiple times, the purchase of a highly accurate and robust Lidar system (located either on the ground or a turbine nacelle) appears as a very sound investment by comparison. Plain and simple, Lidars allow the wind energy industry to understand, characterize and harness its own fuel source with more certainty and intelligence than ever before. Used properly, they also lessen the overall cost of wind farm development and operation.

evan osler
Evan Osler

Evan Osler was the senior technical lead for remote sensing products at NRG. He has more than a decade of experience in the wind energy industry in a variety of roles, with a primary focus on wind resource and energy assessment, remote sensing, and GIS. Evan holds a bachelor's degree in geography from Middlebury College.

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