M.Sc Thesis

M.Sc StudentGandelman Roman
SubjectModelling, optimization and monitoring of small wind
turbine for low cut in velocities
DepartmentDepartment of Aerospace Engineering
Supervisor PROFESSOR EMERITUS Yeshayahou Levy
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


The current work is an attempt to resolve one of the major disadvantages of small Wind Turbines (WT) in urban environment, their low return on investment. This can be accomplished by increasing WT efficiency in low wind velocity regime and decreasing the overall system cost.  Achieving those goals requires solving several problems.

1.      Long time of idle blades in the low wind velocity regime.

2.      Low WT power efficiency in the low wind velocity regime.

3.      Expensive control and power system.

Long periods in which the blades are idle and low power efficiency were solved by designing new blades with high torque and efficiency at the low wind velocity regime. The blades increase in performance was achieved by optimization of the blades geometry and their numbers through numerical iterative process based on two steps; a pattern Search (PS) algorithm and the Sequential Quadratic Programming (SQP) method. Optimizing by PS and then SQP with respect to a cost function that takes into account high torque and power efficiency, lead to modified blades geometry with superior efficiency and reduction of 50% in the “cut in” velocity with respect to commercial WT blades.

Acquiring the aerodynamic performance of the proposed blade geometries was based on the implementation of the blade element momentum theory (BEM) in MATLAB and verification of the results in the QBLADE software.

The expensive original MPPT control system was replaced by a relative low cost method for keeping optimal RPM in fast changing wind velocity. The new control system was developed, integrated and tested within the commercial Bergey XL1 Small WT.
The design of the new control system was based on fast & controlled switching of the WT electrical load by a solid state relay (SSR). Loading and unloading the Turbine Alternator affects the WT resistive torque and therefore can be used as a control mechanism for fast RPM adjustment in high changing winds. The theoretical basis of the frequency and the duty cycle of the switching was developed and a control algorithm was implemented using the LabVIEW software platform. A National Instrument (NI) digital output unit controlled the SSR by implementing the LabVIEW control commands. A system incorporating self-assembled and commercial sensors was developed and tested for the controller feedback loop.
The control system was tested in two phases. First in a controlled environment, using a self-assembled WT hybrid emulator, in constant and varying wind velocities. The second test phase was done in real environment, while the Bergey WT was installed on the roof of the Turbo and jet Engine laboratory at the Technion, under real wind velocities. Both tests resulted in good tracking performance of the MPPT controller.

It was demonstrated that while using the modified blades and control system, the wing energy harvesting capability of the WT system was improved by about 25%.