As we have said a number of times, the vagaries of the wind are proving to be quite the hurdle. The forecast called for wind this last Saturday, so we prepared in advance and I had a number of people “on call” to help set up the test turbine and take some data when the wind arrived. However, the wind didn’t get here until Sunday and everyone was busy after having cleared their Saturday schedules. End result: no testing. This is why we desperately need a wind tunnel, so we are no longer at the mercy of the wind.

The good news is that we are in ongoing talks with the folks at NASA’s Ames Research Center at Moffett Field near Mountain View. They have a number of wind tunnels of varying size (up to 80’x120’) and have expressed interest in allowing us to test our turbine in their tunnels. This is a fantastic development and we are currently in the process of writing our formal test proposal. Hopefully they agree to help us out! The only downside to the testing option at NASA is that we won’t have access, if we are granted access, until June. That means we have to either spend the next three months continuing to chase the wind or commit to building our own “rough-and-ready” wind tunnel for some preliminary tests.

The turbine, in its current form, is a test prototype. We have attached a variety of digital meters to the turbine to allow us to calculate how much wind energy the turbine is capturing and converting into rotational mechanical energy (this information will be used to help design the generator which will produce the electricity). The equation for power in a rotating system is very simple: Power = Torque x Speed.

1) Friction Collar; 2) Optical Tachometer; 3) Torque Arm; 4) Force Gauge

The photo above shows our test set-up. To measure speed (in rpm) we use an optical tachometer (2). To measure torque we machined a plastic collar (1) that fits around the end of the turbine shaft and is attached to a long aluminum bar (3). At a specific distance down the length of the bar we have attached a force gauge (4). The collar can be loosened and tightened to decrease or increase the amount of drag (in the form of friction) caused by the collar on the turbine. This resistive force is transferred along the aluminum bar to the force gauge. The resulting arrangement is that the forge gauge measures how much resistance (torque) the turbine is overcoming to spin. We also have a hot-wire anemometer included in the set-up (not shown) that measures the velocity of the wind. As a result of measuring torque, speed, and wind velocity, we can now calculate how much power is generated by the turbine at a specific wind speed. All of these devices are connected to a Data Acquisition System (DAQ) written in LabView and running on a laptop computer.