Model guide

Vestas V136/4.2M

4.2 MW rated power, 136 metre rotor. The member of the Vestas 4 MW platform built for low-to-medium wind sites. It is not simply a scaled-up V126: the 17% larger swept area moves blade root loads, pitch bearing duty and transport logistics into a different class.

Why V136? The swept area argument

The energy a turbine produces rises with the cube of wind speed and linearly with swept area. On a weak-wind site you cannot change the speed, so area is the only lever you have. The 136 m rotor sweeps roughly 17% more than the V126, which lifts the capacity factor noticeably in a low wind regime.

The price is paid in the blade. At 66.7 m it is both longer and heavier than the V126's 61.5 m blade; root moment, pitch bearing load, tower-top bending moment and blade–tower clearance all change accordingly. On site that means a longer erection, harder transport, and more attention to vibration monitoring.

V126 vs V136

Specifications

Model-specific systems

Hybrid gearbox and oil management

• Layout: a planetary input stage feeding helical output stages — high torque capacity in a compact package.
• Oil volume: around 1000 L. The number alone means little; what matters is filter interval and the metal analysis trend.
• Temperature: nominal 45–65 °C, alarm typically above 80 °C, shutdown above 95 °C. A rise at the same wind speed over weeks is a more meaningful warning than any absolute figure.
• Field note: a larger oil volume means a larger radiator surface; at dusty and coastal sites radiator cleaning is among the highest-return jobs available.

Pitch — long blade, heavy load

• Independent pitch: each blade controlled separately, which is how load balancing and vibration suppression are achieved.
• Pitch bearing: root moment on a 66.7 m blade is high, so bearing lubrication and play monitoring are critical.
• Asymmetry: a few degrees is enough to produce rotor imbalance that returns as vibration — see Case 07 for the mechanism.

Blade and vibration

• Blade–tower clearance: deflection under load rises on a long, flexible blade, so clearance checks belong in the periodic list.
• Resonance bands: the wide speed range (5.2–15.6 rpm) is an advantage, but elevated tower and nacelle vibration in particular wind bands is a typical monitoring topic.
• 1P / 3P harmonics: reading the vibration spectrum together with rotor speed is the fastest way to separate an imbalance from a control problem.

Assembly stages (21–23 days)

1. Days 1–3: crane pad and ground bearing capacity checks, blade stand layout, safety briefing. On a large rotor the crane plan is the most critical part of the job.
2. Days 4–11: tower erection; the tall hub options (132–149 m) add a section, more flange bolts and more tensioning time.
3. Days 12–14: nacelle and hub. The lift window is very sensitive to wind limits and waiting is normal at this stage.
4. Days 15–19: blade installation, 66.7 m blades. Single-blade lifting methods loosen the wind limit somewhat. For root flange bolt tensioning see the bolt tension calculator.
5. Days 20–22: electrical and cooling — converter cabling, coolant fill and bleed, SCADA connection.
6. Day 23: commissioning — grid synchronisation, pitch calibration, yaw zeroing, performance test.

Maintenance schedule

What comes up most in the field

• Gearbox temperature trend: a slow climb is the earliest sign of low oil level or a fouling radiator. Real case: Case 02.
• Vibration from pitch asymmetry: a rise confined to a particular wind band is usually a calibration problem rather than a blade problem.
• Converter thermal management: air trapped in the liquid circuit or a fouled radiator shows up as power limiting.
• Transport and access damage: on a 66.7 m blade the most expensive damage happens on the road into site; pre-erection blade inspection deserves to be its own line item.
• Grid interaction: on a weak grid, harmonic and reactive power tuning is the main source of power quality complaints.