In the wind field, the problem often encountered is that rain erosion damages the aerodynamic performance of the blade, and in the case of serious accumulation, it will lead to blade failure or even shutdown. The robotic repair, which has been developed, is said to not only restore the power output of the fan, but is also fast, economical and efficient, and the technicians involved in the repair can work safely in all but the worst weather conditions. Previously, technicians had to slide from the cabin to the blades and work with hazardous chemicals in a weather-dependent and costly environment.
Rain erosion is already a serious and worsening problem, especially now that long blades with tip speeds in excess of 380 km/h are common. Raindrops falling at this speed act like hail and destroy the blade leading edge airfoil over time.
Efficient frontier maintenance helps to extend the life of wind blades, which accounts for about 25% to 30% of the total wind turbine construction cost.
A repair robot developed by Rope Robotics, a foreign company, claims to be able to restore up to 3% of energy output per blade in less than a day, at half the cost of a human. Its robot is currently being tested at sea. Nine Rope Robotics robots have been in commercial operation for a year and a half and have repaired more than 150 wind blades in the United States, Canada, South Africa and Europe.
At the heart of the system is a robot carrying a vision sensor that operates the repair tool using a flexible arm, and technicians can monitor the robot from any location, on-site or remotely.
Currently the robot has been field-validated at wind speeds up to 14 m/s, relative humidity up to 80%, and temperatures ranging from 0 to 40 degrees Celsius.
In the wind field, the 150-kg robot was first secured to ropes in the engine room and then hoisted to a damaged blade about 100 m above the ground, which had been secured vertically. The vacuum system enables the robot to be firmly attached to the motor while the motor can move on the blade. The robot examines the surface using its onboard high-resolution camera and laser scanner and sends the images to a remote operator who diagnoses the damage and initiates the repair process in real time.
The process of blade repair is to first sand the damaged area, applying appropriate velocities and forces to create a pattern that ensures surface roughness and geometry. This is followed by cleaning the surface using a brush and alcohol to remove dirt and oil. The patented metering tool is used to measure the LEP material, while the also patented lifting tool reconstructs the optimal aerodynamic blade profile to bring the material to predetermined standards.
Controlled remotely on a screen by a technician viewing live images, the robot performs each step with high accuracy and consistency, thus ensuring quality. All images are recorded and used as documentation, which is a global requirement for wind turbine maintenance.
