When comparing small wind turbines, the yaw system tells you how the machine changes its orientation as wind direction changes. Electric yaw uses a motor to turn the nacelle. Passive yaw uses aerodynamic forces to orient the turbine. For a buyer, the useful comparison is how each proposed system operates, what equipment it requires and what evidence supports its suitability for the project.
A specification that simply says “automatic yaw” leaves several questions unanswered. Before comparing prices, ask each supplier to describe the mechanism and the operating sequence for the exact model being quoted.
What is the difference between electric and passive yaw?
In a motor-driven yaw arrangement, a drive turns the nacelle to change the direction the rotor faces. The U.S. Department of Energy describes this role in its guide to wind turbine components.
Passive yaw can take different forms. A tail can use wind force to orient an upwind turbine, while a downwind turbine can use its aerodynamic arrangement to align itself. Both types are represented among the turbines at the National Laboratory of the Rockies’ distributed wind research facilities. A tail is therefore one example of passive yaw, rather than a feature shared by every passive-yaw design.
1. Ask what starts a change in direction
For an electric-yaw proposal, request a description of the direction measurement, the controller’s decision process and the drive that carries out the movement. Ask how the system distinguishes a sustained change in wind direction from a brief fluctuation, and whether the relevant settings are fixed or adjustable.
For a passive-yaw proposal, ask which components produce alignment and how the manufacturer describes their response to changing wind direction. A drawing showing the yaw axis, rotor and tail or downwind arrangement is more useful here than a broad claim about “wind tracking.”
2. Review normal operation and stopping together
Request a sequence covering start-up, generation, a commanded stop and loss of the normal electrical supply. For an electric-yaw system, identify the source of power for the yaw drive and controls, and ask what happens when that supply is unavailable.
For either design, ask how yaw behaviour relates to the turbine’s other protection functions. Specify the role of each mechanism separately: changing nacelle direction, limiting rotor speed and stopping the rotor should each have a clear explanation in the equipment documentation.
3. Compare the service work you would actually arrange
Ask for the maintenance schedule associated with the quoted configuration. Relevant questions include:
- Which yaw components require inspection, lubrication or adjustment?
- How are those components reached, and what access equipment is needed?
- Which replacement parts should be held locally?
- What records or diagnostic information help a technician investigate a fault?
Use these answers to build a practical service plan for your site. Count the required visits, skills and equipment rather than assuming the yaw label alone determines maintenance cost.
4. Keep the performance comparison specific
If a quotation claims an energy advantage from its yaw design, ask for the basis of that comparison. Identify the turbine models, rotor sizes, control configurations, wind conditions and measurement boundaries involved. Check whether the evidence describes the equipment offered in the quotation.
For example, a record from an earlier machine with a different yaw drive can be useful background, but it does not establish the performance of the current configuration. Ask the supplier to connect each performance claim to the relevant test report or operating record.
Review a MARSTON electric-yaw configuration
The current MARSTON FD14-50 kW wind turbine configuration uses an electric motor to drive its yaw mechanism. A useful project discussion starts with the proposed site, available wind information, electrical connection and equipment scope, then works through the operating and service questions above.
To compare a proposal or prepare a specification, send MARSTON your project requirements. Include the turbine model under consideration and the documents you need for your engineering review.