Wind Turbine
I worked as a shop intern for a designer/builder who volunteered a lot of his time toward providing power for underserved communities in Vieques, Puerto Rico, where power is a scarcity. He had done a lot of work sourcing and wiring solar panels for people in Vieques, with their main issue being that battery power is expensive. Therefore, we hoped to create a low-cost wind turbine that they could construct using primarily junk and bamboo found on the island that would diversify their electricity, allowing them to maintain a smaller amount of battery storage. The summer I worked for him, we designed and prototyped a vertical axis wind turbine using sails. We prototyped the turbine, tower, and alternator, keeping our cost of materials under a couple hundred dollars.
Tower
To construct the tower, we fabricated c-channels out of 1" boards, mimicking the properties of bamboo, the material that we imagined the tower would eventually be constructed out of. We strengthened a basic A-frame with diagonal channels, and raised and lowered the tower with the help of an attached gin-pole and winch driven by a drill. We hoped that this system would allow the turbine to be quickly lowered by only one person in the event of a storm. The tower was then held in place with home-welded anchors, pounded into the ground with sledge hammers.
Alternator
To construct the alternator, we initially took apart a couple old brushed car alternators, assuming that the people in Vieques would have access to junk car parts. We replaced the core with a permanent magnet core so that it would need no energy to function, but discovered through testing that this produced considerable cogging due to the external iron frame of the alternator. The alternator we ended up using was self-coiled, with each coil being held in place by epoxy.
Turbine
To design the turbine itself, we enlisted the help of a wind engineer and avid sailor who had dreamed of a sail-powered vertical axis wind turbine his entire career. Using sails allowed the turbine to start with wind flow as opposed to requiring power to start and for each blade to provide power for more of its rotation than a fixed blade, due to its ability to tack throughout its rotation. Additionally, the vertical axis better met the demands of the strong but frequently-shifting winds of Vieques. We would test the turbine by strapping it to a cargo bike or the top of a car, where we could control the speed of the "wind".