Seriously, how do LIDARs measure upward to 200m?

And how do the major players – Natural Power’s ZephIR and NRG Systems/Leosphere’s WINDCUBE v2 — measure up to each other?

Both LIDAR systems developed from the same communication technology and have fiber optic components (“fiber lasers”), but they have a fundamental difference between them: the ZephIR is a continuous wave (cw) wind LIDAR and the WINDCUBE v2 is a pulsed wind LIDAR, a sequence of single transmitted pulses.

So how do these things actually measure?

The ZephIR is a cw system with height discrimination achieved by varying focus.  Five different sensing heights can be chosen.  Each height is scanned for 3 seconds before the LIDAR re-focuses to the next height in the sequence.

The laser light is emitted through a constantly rotating prism giving a deflection of 30 degrees from the vertical and making one complete rotation per second.

The WINDCUBE is a pulsed LIDAR with a fixed focus. Like the ZephIR, it has a 30 degree prism to deflect the beam from the vertical, but here the prism does not rotate continuously. 

The prism instead holds still while the LIDAR sends a stream of pulses in a given direction, recording the backscatter in a number of range gates (fixed time delays) triggered by the end of each pulse. 

Once the WINDCUBE has sent the required number of pulses, the prism rotates to the next azimuth angle to be scanned, each separated by 90 degrees.  A full rotation takes approximately 6 seconds.

Does it matter?  YES

The temporal resolution with cw LIDAR can be one to two orders of magnitude larger than obtainable from a pulsed LIDAR because there is a continuous cycle of data. So, the cw LIDAR has optimal utilization of sampling time.

The pulsed LIDAR is limited by both the sampling time plus the time of flight of the pulse back and forth to the maximum measurement range.

HOWEVER, the pulsed LIDAR can measure in multiple range gates simultaneously, whereas the cw LIDAR measures from a single range at a time.

Viva la Difference!

So the ZephIR provides an elegant, continuous cycle of data and the data is limited to a single range at a time, set by its focus – with a limit of 5 heights that can be chosen. 

The WINDCUBE v2 does not have the same focusing capability, but provides data from multiple ranges – 10 simultaneous heights can be chosen.

Both LIDARs measure to a high degree of accuracy and purportedly with higher availability than ground-based remote sensing systems (think SODAR).

So the preferable system to use for wind assessment all depends on what you want to measure and how you want to measure it.

Jeananne really wanted this collection!

Coming back from WP2010 in Dallas, Greg and I decided to stop in Hot Springs, AR to heal our sore backs and knees.  We found The Battlefield: A Civil War Bookshoppe tucked into the beautiful lobby of the vintage Park Hotel. We found a private collection by a lifelong collector/historian D.R. Magee, including authentic Civil War memorabilia and art. See more photos and a restaurant review of Angel’s in the Park.

General Lee keeps an eye on the Yanks.

I lived on the Upper West Side of Mahattan for 15 years and went through a Ph.D. program at Columbia University, so like all New York liberal intellectuals I, of course, love books and guns — and this place had both!

(Then again, don’t all Southern places sell guns. Greg actually saw a sign one time for Guns And Wallpaper. Although, the sign we saw for Guns And Medical Supplies actually did make sense to us.)

A small glimpse of this amazingly varied collection of memorabilia

There was a display case with the largest handgun we had ever seen. It had two calibers: big and bigger! And the size of the bullets was absolutely huge. Not huge the way guys say something is huge, but honest and truly huge! At least a half inch across — 50 caliber. This gun was more of a handcanon than a handgun.

D.R. Magee, the owner of the collection, is a fascinating character as well. He is an avid Civil War historian which is still more of a current event in the South.

General Lee on proud display.

This guy will fascinate you with his knowledge of the Civil War. I am about as Southern as an Iowan winter — and Greg is a chickatarian who even rescues mice from the cat — so you can image how surprised we were to be mesmerized by Magee and his Civil War sanctum.

Finish off the day with the superb orange roughy at Angel’s in the Park in the Park Hotel lobby. They start you off with homemade bread with a delicious kalamata black olive/caper tapenade, which one reviewer referred to as tamponade. Yikes!

Check out the custom-made bookshelves and the rolling library ladder from New York.

Two 22 caliber rounds went into this NRG logger!

Funny Story Here are some shots of an older NRG Cellogger, no longer in common use,  that took a couple of rounds from a 22 caliber rifle. One round went through the plastic casing after traveling through the metal shelter box, but the second one was stopped by the metal lining inside the logger. A shotgun blast took out the solar panel, but the logger still kept working until the batteries finally failed for lack of solar power. So these loggers are tough. They can take a barrel of buckshot and keep on logging.  See more photos.

The first round went through the plastic casing; the second round was stopped by the metal lining inside the logger box.

We do not know if all loggers are as tough as the NRG loggers. Zephyr Services predominantly installs NRG Symphonie loggers, but Second Wind’s Nomad and Campbell Scientific have been installed by us as well.

All of these loggers have their individual virtues. Price, flexibility and the number of channels desired are just some of the factors that determine a client’s preference.

We also checked out Ammonit’s data logger at WP2010 in Dallas. The steel cabinet is designed to protect it against water and condensation damage as well as theft and vandalism. But the real question is: Can it take a bullet? With its steel casing, perhaps we will find out if it is the new Iron Man logger!

Zephyr Services had ringside seats at the American Wind Energy Association’s (AWEA) convention in Dallas this May to watch SODAR and LIDAR duking it out in the marketplace. Here’s the blow by blow account with a “punch/counterpunch” review of these elite systems.

Zephyr Services admires both these systems and would like to see them used more widely in the U.S. market.  Right now they are being used more widely in Europe than in America.  European bankers require a greater degree of precision and accuracy for bankable wind assessment data.

SODAR (Sonic detection and ranging) systems are used to measure remotely the vertical turbulence structure and the wind profile of the lower layer of the atmosphere.  Think radar, but with sound waves rather than radio waves.

SODAR’s KNOCKOUT PUNCH?  Price. At a base price of $30-40K, with the total package bringing it closer to $50-70K, this system is 4-5 times less expensive than LIDAR.

Triton

Second Wind’s Triton allows for easy access to the circuit boards forreplacement and does not require access to the software.  A panel with sensor lights and a single switch highlight this user-friendly system.

ASC's SoDAR

ASC’s 3000 and 4000 series SoDAR system allows access to the software, but keeps the circuit panels in a back compartment.  The idea there is that techs are more likely to muck up those circuit panels and it is desirable to keep them more isolated.

THE COUNTER PUNCH?  LIDAR claims greater precision and accuracy for data collection with its laser system.

LIDAR (Light Detection and Ranging) is a remote sensing system that collects data with pulsating lasers.

Natural Power’s ZephIR (we love the name, but no relation to Zephyr Services, Inc.) is an impressive system that has survived Canadian winters and Australian summers.

NRG’s WINDCUBE v2 was being high promoted by NRG’s sales representatives.  This system is impressive as well and also touts its desirability in complex terrain and remote locations.

LIDAR’s KNOCKOUT PUNCH?  The accuracy and precision of its data collection with its lasers.

THE COUNTER PUNCH?  SODAR takes exception to LIDAR’s claim of precision and accuracy and also considers their system more durable.

Both SODAR and LIDAR are working to demonstrate that their systems are cost effective, durable and low-maintenance.  Power supply also has to be considered since the traditional met towers do not require it.

Zephyr Services looks forward to both systems being used in the U.S. market.  So far, only our European-based clients have approached us about deploying these systems.

So — for the time being — the 60m met tower still reigns supreme.