Saturday, April 9, 2011
Last Tuesday the winds were gusting up to 35 miles per hour in Central Texas. I was excited because I had my data logger connected to our Engineers with a Mission wind turbine and I couldn't wait to see how much power we could generate in the high winds. The tower of the wind turbine was mounted on a large hinge, so that it could be lowered by pivoting for purposes of maintenance. The thought crossed my mind that we should lower it because of the high winds, but I decided not to in order to see how much power we could harvest. I also wanted to test the "self furling" mechanism which was designed to turn the blades out of the wind under high winds.
Late in the afternoon I got an email from someone at the World Hunger Relief farm saying "the turbine was down". I didn't know what that meant. It could mean anything as simple as the tail fell off, to the tower had collapsed. Unfortunately, it was the later. When I arrived, I could tell at a glance that it was bad.
The top half of the tower and the turbine itself were upside down in the dirt, hanging, like an almost-severed limb, by a tendon of guy wire cables.
The hand-carved wooden blades were shattered, the tail stalk was severely bent, and the box with the electronics in it had a crushed lid. Some of the steel parts were bent and the guy wires were laying all over the place.
The culprit, the weak link in our system, I think, were the turnbuckles in two of the guy wires. These are the parts I am holding in the picture above. They have female threads in each end that be used to tighten the cables. They seem to have come unscrewed from the threaded eyes to which they were connected. Or perhaps the threads themselves were pulled out by a strong gust of wind and a swaying tower. Once they failed, the weak point in the tower gave way and the turbine came crashing down. At least that's what I think happened.
We are all rather disappointed in this. It took three years to get everything built and erected, but only a month for it to fall down. It's a little embarrassing. And discouraging. But also, just a little bit funny.
I discussed it with the students and with the folks at World Hunger Relief, and we have decided not to rebuild it. Nonetheless, it was a good experience. I have no regrets (except, perhaps, getting some stronger turnbuckles.)
Labels: Engineers with a Mission
Saturday, April 2, 2011
We had a fire at the wind turbine! I was running some tests at the base of the tower; all the electricity made by the turbine was dumped into some large resistors, so it was essentially an electric heater. I had them sitting on a board, and apparently, they got so hot that they caught the 2x4 on fire. The fire was big enough to melt the insulation off my wires and even unsolder some of the connections!
These are the charred wires.
The 2x4 that burned.
More melty wires.
I took all the burned up parts back to the lab. Jono came with me and helped me cut off the old wires and unsolder the connections. He liked using the soldering iron. Then I taught him how to measure the electrical resistance of the components and he felt very important. Remarkably, all of the resistors still work fine, despite being immersed in flames! So Jono and I rebuilt the resistor bank and got some new insulated wires to reconnect it to the wind turbine.
Jono measures the resistance.
Our rebuilt (if slightly charred) resistor bank.