Henry Kurniadi

JSWTA 0001Explanation of

Simple Load Model for VAWT

• Japanese small wind turbine standard for design and structural safety.

• Use in complement with IEC 61400-2.• Specialized for ClassNK’s Japanese

certification scheme.

JSWTA 0001

Coordinates and Axis System• Definition of

coordinate and axis system in Vertical Axis Wind Turbine system.

• During normal operation, a range of fluctuating loads will affect the turbine system.

• Unlike in HAWT, the fatigue loading does not consider the effects of changing rotor rotational speed.

Load Case A: Fatigue during Operation

Load Case A: Fatigue during OperationBlade (B)• The loading fluctuates between maximum

and minimum values, based on experimental result as a function of TSR (λ).

∆𝐹 𝑥𝐵=12𝜌 𝐴𝑝𝑟𝑜𝑗 ,𝐵 (1.5𝑉 𝑑𝑒𝑠𝑖𝑔𝑛 )2 (8.5 λ𝑑𝑒𝑠𝑖𝑔𝑛−3.2 )

Load Case A: Fatigue during OperationSupport Connector (S)• The force acting on the blade handled by the support

connector. The force acting on each support connector could be written as the radial force on the blade divided evenly by the number of connectors (S) for each blade.

• The torsional moment generated from rotor design torque, which divided evenly by each connector on each blade.

Load Case A: Fatigue during OperationShaft (shaft)• The torsional moment of the rotor shaft is equal to

the rotor design torque.• Rotor thrust generated during operation is a

function of design wind speed.• Bending moment of the rotor shaft determined by

the thrust and the distance of the main bearing to the rotor center. (2 is the multiplying factor)

• This is a maximum thrust applied to the shaft during normal operation regime.

• Similar assumption with HAWT.

Load Case D: Maximum Thrust

Load Case D: Maximum ThrustShaft (shaft)• The thrust load consist of aerodynamic

coefficient and dynamic pressure.• Bending moment of the rotor shaft

determined by the thrust and the distance of the main bearing to the rotor center.

• This load case represents the maximum operation condition.

• Similar assumption with HAWT with load case definition dominated by the maximum rotational speed.

Load Case E: Maximum Rotation Speed

Load Case E: Maximum Rotation SpeedBlade (B)• The load to each blade purely centrifugal

force.

𝐹 𝑥𝐵=𝑚𝐵𝜔𝑛 ,𝑚𝑎𝑥2 𝑅

Load Case E: Maximum Rotation SpeedSupport Connector (S)• The force acting on the blade handled by

the support connector. The force acting on each support connector could be written as the radial force on the blade divided evenly by the number of connectors (S) for each blade.

Load Case E: Maximum Rotation SpeedShaft (shaft)• The loading to rotor shaft is a bending

moment. It is assumed that there is an eccentricity in the rotor shaft.

• This load case represent the short circuit condition.

• Similar assumption with HAWT.

Load Case F: Shorted Connection

Load Case F: Shorted ConnectionShaft (shaft)• The torsional moment to the rotor shaft

due to generator short circuit. It is a function of the rotor design torque.

Load Case F: Shorted ConnectionSupport Connector (S)• The torsional moment to support connector

calculated from rotor torsional moment, which divided evenly by each connector on each blade.

𝑀 𝑥𝑆=𝑀 𝑧− h𝑠 𝑎𝑓𝑡

(𝑆𝐵 )

• This represents the braking action of the turbine system.

• Similar assumption with HAWT.

Load Case G: Braking

Load Case G: BrakingShaft (shaft)• The torsional moment applied to the rotor

shaft during braking assumed to be the sum of the brake torque and the rotor design torque.

Load Case G: BrakingSupport Connector (S)• Similar to previous Load Case, the torsional

moment to support connector calculated from rotor torsional moment, which divided evenly by each connector on each blade.

𝑀 𝑥𝑆=𝑀 𝑧− h𝑠 𝑎𝑓𝑡

(𝑆𝐵 )

• In this load case, the turbine is not working and exposed to extreme wind condition.

• Similar assumption with HAWT.

Load Case H: Extreme Wind

Load Case H: Extreme WindBlade (B)• The blade is in standby situation. • The force applied directly from the wind in X-

direction.• The aerodynamic loading applied to the blade

consist of lift and drag and located in Y-direction.• All loads are function of the blade projection area.

Load Case H: Extreme WindSupport Connector (S)• The force acting on the blade handled by the

support connector. The force acting on each support connector could be written as the applied force on the blade divided evenly by the number of connectors (S) for each blade.

• The bending moment applied in each support connector is a function of the connector length.

Load Case H: Extreme WindShaft (shaft)• Wind load to rotor generated by the drag acting

on the blade.• Largest bending moment applied to the first

bearing.• The torsional moment to the rotor shaft caused

by rotational force applied to the blade.