Since the goal was to utilize recycled materials, they gathered almost everything from the physics shop at their school. The exceptions were two 3D printed caps/lugs and the bits of sheet metal used for the rotor blades.
According to the diagram that you can find attached to the original post mark the locations of the holes.
In order to connect the PVC pipe to the axle rod tightly, they needed to print two plug-like pieces. The pieces fit like a cap on the top and the bottom of the pipe and had holes for the axle rod.
The design can be significantly improved. It can be made lighter, more stable and with less moving parts.
Additionally, they could change the design so they would not need to use the 3D printer since it is a rare and expensive technology. Finally, they would like to store the electricity in a battery, instead of powering the bulb immediately.
115mm Pvc Pipe
Plastic Injection Molding, Wholesale Plastic Injection Molding - Hong Cheng Long,https://www.xmhclsl.com/