1. LiDAR vs met mast, standalone LiDAR and hybrid campaigns
What is the difference between a wind LiDAR and a met mast?
A met mast measures wind with cup anemometers and vanes fixed on booms at set heights on a tower. A ground-based wind LiDAR is a laser remote-sensing device that measures wind speed and direction at up to 20 heights between about 40 m and 300 m, without any tower. Both technologies give a long, well-proven point measurement; LiDARs give a full rotor-height profile and can be moved across the site. Both are covered by IEC standards: IEC 61400-50-1 for masts and IEC 61400-50-2 for ground-based LiDAR.
Is LiDAR as accurate as a met mast?
A well-run met mast campaign typically reaches 1.5–2.0% measurement uncertainty on wind speed; a verified LiDAR reaches 1.5–4.0%, depending on terrain and verification. When a LiDAR is verified against an on-site mast, its verification uncertainty falls to about 0.2–0.3%, matching mast accuracy. In complex terrain the LiDAR needs a flow correction (e.g. CFD) to reach comparable accuracy.
What are the advantages of LiDAR for wind resource assessment?
- Measures directly at hub height and across the full rotor, up to 300 m, so no vertical extrapolation above a top boom.
- Deploys in days, typically with no construction permit, so the campaign starts months earlier.
- No work at height, which removes a major health-and-safety risk.
- Can be relocated to cover several turbine clusters during the campaign.
- Lower upfront cost than a hub-height mast, and reusable.
When is a met mast still the better choice?
A mast remains the reference where lenders or turbine suppliers need point turbulence intensity from cup anemometers, in complex terrain where MEASNET requires at least one mast, and on long-timeline projects where a permanent reference is valuable. Masts also keep recording in fog, heavy rain or very clean air, when LiDAR data availability can drop. The trade-offs are long permitting and erection lead times, higher CAPEX, and extrapolation above the top boom (usually ≤ 140 m).
What is a standalone LiDAR campaign?
A standalone campaign uses one or more LiDARs as the only on-site wind measurement, with no met mast. It is accepted as bankable in flat and simple terrain under FGW TR6 and MEASNET, provided the LiDAR is verified by an accredited body before and after the campaign. P99 recommends standalone LiDAR for early development, simple-terrain sites and repowering studies.
Can LiDAR be used in complex terrain?
Yes, with the right approach. In hilly or mountainous terrain the flow is not uniform across the LiDAR’s scanning cone, which causes a measurement bias. P99 screens every candidate position for terrain complexity. For bankable results in complex terrain we combine LiDARs with at least one reference mast.
What is a hybrid (combined) measurement campaign?
A hybrid campaign pairs a met mast with one or more LiDARs on the same site. The mast is the long-term reference and verifies the LiDARs on site; the LiDARs measure the full rotor height and can roam between turbine clusters. The result is validated vertical profiles, data availability typically above 95%, and the lowest overall uncertainty. It is P99’s standard recommendation for complex terrain and for lender-grade energy yield assessments at financial close.
How do you design a campaign for a large or complex wind farm?
We start with a site visit and terrain screening, then phase the equipment. In one P99 case study (complex terrain, turbines spread over more than 20 km, 4-year development timeline), a single LiDAR at the smoothest central location started measuring in year 1. A reference mast and a second reference LiDAR followed in year 2, and a second mast on the most complex ridge plus a roaming LiDAR in years 3–4. The client de-risked the site before committing to the full campaign budget.
2. Campaign duration and when to start
How long should a wind measurement campaign last?
At least 12 complete, consecutive months; 24 months or more is preferred for a lender-grade energy yield assessment. Twelve months captures one full seasonal cycle and is the minimum under MEASNET and FGW TR6. Each extra year reduces long-term correction uncertainty, and lenders generally accept it once it falls below about 2%, which a 24-month campaign typically achieves.
How does campaign duration affect uncertainty?
Long-term (historic climate) uncertainty falls roughly with the square root of the number of measured years. Going from 12 to 24 months cuts it by about 30%.
Can I get useful results before 12 months?
Yes. P99 provides interim assessments during the campaign, typically after 3 and 6 months, correlated against long-term reference data. They confirm whether the site is worth pursuing and support early layout and turbine decisions. They do not replace the 12-month minimum for a bankable energy yield assessment.
When should we start measuring on a new wind project?
As early as possible, ideally as soon as a site has passed desktop screening and land access is secured. Measurement is usually on the critical path to financial close: permits, grid connection and turbine selection all progress in parallel, but lenders will not close without at least 12 months of site data. Starting with a LiDAR avoids waiting months for a mast permit.
How long does it take to install a LiDAR vs a met mast?
A LiDAR with an autonomous power supply can be delivered and operating in a few days, and pre-verified units can shorten the start further. A tall met mast needs design, permitting and foundation or anchor work.
What is the minimum data availability required?
MEASNET requires at least 90% availability of filtered data from the primary sensor (with its backup) over 12 consecutive months, and at least 95% after gap-filling. That is why P99 uses redundant sensors, remote monitoring and autonomous hybrid power to keep availability high.
3. Bankability
What does “bankable wind data” mean?
Bankable data is wind data that an independent technical adviser and a lender accept as the basis for financing a project. It must be collected with calibrated, traceable instruments, following IEC and national guidelines, with documented installation, monitoring and quality control, and it must allow every source of uncertainty to be quantified. The goal is not just a good wind speed, but a defensible P50 and P90 energy yield.
Is LiDAR data bankable?
Yes. Ground-based LiDAR data is bankable in simple terrain as a standalone measurement under FGW TR6 and MEASNET, and in complex terrain when combined with flow correction and at least one reference mast. Lenders require the LiDAR to be classified by an accredited laboratory and verified before and after the campaign according to IEC 61400-50-2.
What are P50 and P90, and why do lenders care?
P50 is the annual energy production expected to be exceeded with 50% probability; P90 is the level exceeded with 90% probability. Lenders size debt on P90 (or P99 for stress cases), so lower uncertainty directly means more debt and better project economics. Using a normal approximation, P90 = P50 × (1 − 1.28 × total uncertainty). A well-run campaign on a good site gives total uncertainty of about 5–10%, and projects typically aim for a P90/P50 ratio of 85–90% or better.
What contributes to the uncertainty of an energy yield assessment?
IEC 61400-15-1:2025 groups uncertainty into categories that combine as a root-sum-of-squares:
| Component | Typical range | Reduced by |
| Site measurement | 1.5–2% mast; 1.5–4% LiDAR | Calibration, verification, good siting |
| Historic climate (long-term correction) | 1.0–3.5% | Longer campaigns, quality reference data |
| Vertical extrapolation | 0.5–1.5% | Measuring at hub height (LiDAR) |
| Spatial / horizontal extrapolation | 1–3% | More measurement points, roaming LiDAR |
| Future wind variability | 2–5% | Not reducible by campaign design |
| Plant performance and losses | 2–5% | Detailed wake and loss modelling |
Campaign design mainly acts on the first four rows, which is where a measurement consultant adds value.
Which standards and guidelines apply to wind measurements?
- IEC 61400-50-1 – wind measurement with met masts and nacelle instruments.
- IEC 61400-50-2 – ground-based remote sensing (LiDAR, SoDAR).
- IEC 61400-12-1 Ed. 2 – power performance measurements.
- IEC 61400-15-1:2025 – site energy yield assessment and uncertainty.
- MEASNET “Evaluation of site-specific wind conditions” v3 (2022) – minimum durations, heights and representativeness.
- FGW TR6 Rev. 12 – German technical guideline widely used by lenders.
- IEA Wind Recommended Practice 15 – ground-based remote sensing for resource assessment.
How high and how close to the turbines must the measurement be?
MEASNET requires the main measurement height to be at least two-thirds of the planned hub height, with a second level at least 20 m lower. Each turbine should be within about 10 km of a measurement in simple terrain and within 2 km in complex terrain. With modern hub heights of 150–180 m, this is where LiDAR, measuring directly at hub height, has a clear advantage over most masts.
Do lenders and development banks accept combined LiDAR and mast campaigns?
Yes. Combined campaigns are routinely used for projects financed by commercial banks and international finance institutions. Because the on-site mast verifies the LiDARs and fills their data gaps, combined campaigns typically achieve lower total uncertainty than mast-only campaigns.
4. Other frequently asked questions
How is a LiDAR powered at a remote, off-grid site?
With an autonomous hybrid power supply. P99’s containerised unit combines 940 Wp of solar PV, 8.48 kWh of usable battery storage and an EFOY PRO 2800 methanol fuel cell that starts automatically when solar input is low. The batteries alone run a LiDAR for about 130 hours; with the fuel cell the system operates year-round, including winter. For sunny sites we also supply a PV-only system with no fuel logistics. See our power supply products.
How do you protect equipment against theft and vandalism?
Our LiDAR stations can include a lockable container or trailer, CCTV surveillance, GPS tracking and motion detection, all monitored remotely. Site selection also considers access and visibility. In our experience, physical protection plus remote alerts is the most effective way to avoid data loss from interference.
How is data monitored during the campaign?
Data is transmitted daily and checked by P99 analysts for availability, sensor faults and plausibility. The power system is monitored in real time (Victron VRM), so faults are detected before they cause data loss. Clients receive regular status reports and interim resource assessments.
Does LiDAR work in winter, fog and icing conditions?
LiDAR has no moving parts to ice up, unlike cup anemometers, but it needs aerosols in the air to measure. Very clean air, dense fog or heavy precipitation can reduce data availability at the upper heights. Recent algorithm improvements recover much of this data. On sites prone to icing or low-aerosol conditions, a combined campaign with a heated-sensor mast gives the best availability.
What is LiDAR verification and why is it needed?
Verification is a side-by-side test of the LiDAR against a calibrated reference mast at an accredited test site, before and ideally after the campaign. It proves the device measures correctly and sets its measurement uncertainty. IEC 61400-50-2 and FGW TR6 require it for bankable use; without it, lenders apply large uncertainty penalties.
Can LiDAR measure turbulence intensity for turbine site suitability?
LiDAR measures turbulence over a volume, not at a point, so raw LiDAR turbulence intensity differs from cup-anemometer values. IEC 61400-15-1 requires it to be validated against cups or corrected with an accepted algorithm. Newer methods now reconstruct cup-equivalent turbulence and are increasingly accepted by turbine manufacturers.
Is LiDAR useful for repowering or operating wind farms?
Yes. A LiDAR measures wind directly at the new, higher hub height (often 40–80 m above the existing turbines) and records shear and veer across the future rotor. This removes much of the uncertainty of relying on SCADA data from the old turbines and supports a defensible energy yield for repowering or acquisition.
Do you also measure solar resource?
Yes. P99 designs and installs solar measurement stations and provides solar irradiation analysis and energy yield assessments for PV and hybrid wind-solar projects, including utility-scale PV plants in Bulgaria.
Which countries does P99 Energy work in?
P99 Energy is based in Sofia, Bulgaria, and runs measurement campaigns across Southeast Europe, including Bulgaria, Romania, Serbia, North Macedonia, Albania and Bosnia and Herzegovina. The team has worked on projects on five continents, including multi-GW green hydrogen programmes in Argentina, Mauritania, Morocco and Djibouti.
Do you sell, rent or operate LiDARs?
All three. P99 Energy is an authorised representative of the Vaisala WindCube and ZX Lidars. We supply equipment, run turnkey campaigns (design, installation, power, monitoring, maintenance and analysis), and provide energy yield assessments from the data. We are technology agnostic and select the device that fits the site. Contact us for a campaign proposal.