BLADE-INTEGRATED OVERSPEED CONTROL
[ Overview ] Results
Overview
Team: L. Staudt; N. McMahon*; P. Rogers; R. Byrne; P. MacArtain.
Organisation: Centre for Renewable Energy at Dundalk IT.
Background
Rotor overspeed prevention is a critical design issue. Overspeed leads to the generation of increasingly large aerodynamic forces and induced vibration. Excessively large forces can cause structural failures; in extreme circumstances, overspeed can lead to the complete structural disintegration of a system. Such failures are expensive and dangerous. In order to avoid this possibility, emergency overspeed protection is essential. While electrical braking can slow and stop rotation, failures have demonstrated that, for true reliability and safety, another layer of protection is required. There are three broad strategies for avoiding overspeed, namely: (i) aerodynamic braking; (ii) controlling blade pitch; (iii) furling, i.e. turning the rotor out of the wind. There are advantages and disadvantages to each, but the most common solution for small turbines is to furl the rotor.
In general, pitch control systems are relatively expensive and complicated and are cost-effective only for larger (~>100kW ) turbines. Furling systems are difficult to scale up beyond ~10kW turbines.
Project Aims
The aim of the First Rotor project has been to develop a commercially viable blade-integrated overspeed control system for small (up to ~100kW) fixed-pitch turbines. The project was initiated in 2008 and is still open.
Tasks Completed to Date
Theoretical analyses and experimental tests of blade configurations were conducted throughout 2009, culminating in a series of about 20 field tests through summer and autumn. All testing was carried out on a 10 m test stand at a remote test site close to Slane in Co. Meath.
This work identified several promising configurations.
Detailed plans were drawn up for a 3 kW test wind turbine to be located on-campus at DkIT. Its intended purpose was to provide a real test-platform for the prototype overspeed device. Some of the components were made on-site at DkIT; others were fabricated at a local precision engineering workshop.
In December 2009, the test turbine was assembled and erected in DkIT.
 
Work continued during 2010 to refine candidate configurations.
Results
An overview of the results from the project was presented in April 2010 (see also below). This work is pending publication.
The project is still open.
Funding
From 2008 until 2010, the primary funding source for First Rotor was Enterprise Ireland.
Publicity
Interim results from the project were presented at the International Small Wind Conference in Glasgow in April 2010.
Niall McMahon, July 2011.
*As a note, the position of the authors is not of particular importance. Larry Staudt was the leader of the group; he thought of the main idea. The other team members contributed in unique ways; all worked hard. Larry and I co-presented at ISWC 2010. For academic publications arising from this work, I am the corresponding author.
Acknowledgements
Additional graphics provided by the Science Picture Company.
All images © 2011.
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