Sharp VAWT

A more close up look at the small Sharp VAWT with details on pivot and wing construction.

A small Sharp VAWT. The diameter is 600 mm and the height is 400 mm. The wings have a 40 mm chord and are made from balsa wood.

Some video of the completed Sharp VAWT. It worked well with lots of starting torque and good speed. In a modest wind, it was spinning fast enough to make me wait for the wind to die down before attempting to stop it. However, a number of weaknesses in the design make it apparent that it would tear itself apart. The windmill has since been disassembled to address those issues.

Two of the four wings have been covered in fiberglass and epoxy, balanced, and mounted on the turbine. It turns easily in a light breeze. The next step is to finish up the other two wings.

A look at the construction of a new Sharp style VAWT with a single arm going out to the wings and a streamlined pivot. This one is 4.0 square meters in area making it larger than the previous one that was billed as the largest Sharp VAWT. There is still some work to be done on the wings, but it already shows signs of having good torque.

A brief look at the redesigned wing for a Sharp VAWT. There was an issue with mounting the foam core on the spar. This video demonstrates how I increased the opening slightly to allow for easier mounting of the spar.

Trying out using a couple small bungee cords as stops to cushion the wing as it hits the limits of its travel.

The Sharp style vertical axis wind turbine is shown generating a small amount of power in a very light breeze using a couple pulleys, a round belt, and a small stepper motor. It was able to light an LED even though the wind was around 1 m/s. It demonstrates the idea of using a large turbine and a small generator to get more consistent power from light wind. It isn't much, but it is available much of the time. The advantage of using the Sharp VAWT is that it has good low end torque to turn the generator without the need for all the material needed to build a Savonius VAWT of similar proportions in order to get high torque.

A clip of the VAWT in a little stronger breeze. I think it would be kinder to the pole if it had a couple more wings.

A short clip of the Sharp style VAWT in a gentle breeze. It looks like the pole is getting a workout. I'm not sure if it is a matter of balancing the turbine or adding a wing or two so the frequency of the pulses quickly moves above the natural frequency of the pole.

Construction details for the Sharp style VAWT along with footage of it spinning in a light breeze. I have a number of ideas for making it better, but it does illustrate the concept of the Sharp VAWT as well as demonstrate it working.

A brief video about how the pole to hold the new VAWT was installed.

A video showing the wings being covered in fabric. I chose fabric instead of glass cloth for a little extra weight and integrated color.

The wing construction for a larger Sharp VAWT than in a previous video. The goal is a NACA0018 airfoil with a 200 mm chord that is 1.0 m long. I cut two smaller lengths because it was more manageable and then epoxy the smaller lengths together. Note, there were some fumes; this should be done in a well ventilated area. Later, I plan to cut them to length and cover them in fiberglass for strength and to meet a mass target of 200 to 250 grams.

A somewhat simplified mathematical model of a Sharp VAWT to look at the relationship between the mass of the wing and counterweight and VAWT performance. Adding mass increases torque and therefore power. However, too much mass will lead to stalling. One thing that should be investigated is the effect on natural frequency of the pivot to ensure it is higher than the rotational speed of the turbine.

A small Sharp style VAWT sailing in the wind. The wings are NACA0018, 60mm chord and 310mm long. The Sharp VAWT allows the wings to pivot about a point even with the leading edge of the wing and about 1/4 chord inboard. It also has counter weights to balance the wing at the desired pitch angle. When starting up, the wings pivot to the stops and provide good starting torque. At high speeds, the wings do not move as much acting somewhat like a fixed wing VAWT. However, they still pivot a little and help prevent stall.