After 40 months continuous operation ZephIR demonstrates long-term performance stability of continuous wave lidar with no requirement for re-calibration
A ZephIR continuous wave (CW) lidar has completed 40 months of continuous operation during which time no maintenance or servicing has been conducted on the ZephIR.
(WK-intern) – A 91m IEC compliant mast at the UK’s Remote Sensing Test Site (Pershore, UK) was used to compare pre and post deployment validations from the ZephIR which demonstrated that there was also no need for re-calibration on ‘return-to-base’.
Analysis of the results concluded that any changes in accuracy over the period are insignificant and much less than 1%; well within the industry IEC standard requirement for accuracy which is of the order of 1.5% to 2.0% depending on wind speed for a first class, calibrated, well-mounted cup anemometer.
The advantages of Remote Sensing Devices (RSDs) include their ease of installation and suitability for multiple campaigns, or longer-term finance-grade assessments for Energy Yield Analysis (EYA) contributing to Annual Energy Production (AEP) calculations. A drift in performance would require recalibration which would be a disadvantage to the operator in terms of inconvenience, cost and time.
ZephIR does not require re-calibration and this latest deployment demonstrates the system’s performance stability over time. As per IEA Wind recommendations for ground-based vertically profiling remote sensing for wind resource assessment, a periodic verification or validation for RSDs should be performed after every two years or more frequently if specified by the manufacturer. Following initial deployment in September 2010 the ZephIR in this case continuously acquired wind profile data until February 2014. Due to operational constraints associated with the specific deployment, it was not possible to recover the device for inspection and service within the recommended service interval.
On return to the UK’s Remote Sensing Test Site, the results comparing the lidar and met mast 10-minute speed values showed an impressive level of consistency, with any differences much smaller than 1%. This includes the possible contributions from differing atmospheric conditions during the two test periods, which took place at different times of the year. In addition, during this period, the mast was re-instrumented in accordance with IEC guidelines.
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Figure 1: Pre-deployment (LEFT) and post-deployment (RIGHT) verifications of ZephIR against an IEC met mast following 40 months continuous operation
This conclusion is consistent with the expectation from an analysis of the stability of the main factors that contribute towards the overall system calibration – the uncompromised long-term performance of ZephIR lidars is a consequence of their robust Continuous Wave design based on proven telecomms components. Alternative lidar designs typically demand a ‘back-to-base’ service interval of just 12 months, which may impact any commercial deployment.
ZephIR is provided, as standard, with a 24 month warranty during which time a service is not required.
A full copy of the technical paper relating to the pre and post deployment verifications is available here:
Ian Locker, Managing Director of ZephIR Lidar commented on the report: “For any technology in any market once core performance and accuracy has been suitably demonstrated as it has with ZephIR the next challenge is to ensure its appropriateness for the commercial world. The through-life costs, the service life, the long-term performance…. These are all essential factors in determining how valuable the technology will ultimately be to a client. In the field of wind energy where sites are remote, hard to access at the best of times and costly to mobilise to, a 12 month warranty or requirement for annual back-to-base servicing just isn’t appropriate. Following 40 month’s continuous ZephIR operation we are proud to demonstrate to our clients that there is no change in performance, there is no need for back-to-base services annually, and a 24 month service life and therefore finance-grade EYA campaign is a reality. Continuous Wave lidar technology is the key – robust, simple design with a few moving parts well over-specified for their time in the field as clearly demonstrated in this latest successful ZephIR campaign.”