July 6, 2011
My work over the past month has been an experience unlike any other that I have encountered in my life. It has been very rewarding to collaborate with local people on tasks that will help improve their quality of life. My primary objective for the time that I am here in Bluefields, Nicaragua is to design and build a seventeen foot wind turbine prototype. Although blueEnergy has fabricated and installed several other 12 and 14 foot wind turbines, I feel privileged to have the responsibility of creating a new prototype that will be capable of harvesting more energy than its predecessors.
I already had a strong background in the aerodynamics of wind turbines from Berkeley coursework and integration of wind energy into the grid from university research. However, the wind turbines here are being installed in remote villages without an electrical grid, and efficiency is not nearly as much of a concern as reliability. Therefore, although my background has been beneficial, the obstacles faced in this environment require me to continue learning and applying engineering techniques that I have acquired in new ways.
The workshop that blueEnergy uses at the local university Inatec has been downsized and therefore a significant amount of time has been spent on reorganizing the workshop and building shelves, lofts, and installing lighting and plumbing systems so that work can be done effectively in a smaller area. During this reorganization process I assisted in some of this construction, and began studying the current designs of the wind turbines along with their failures and limitations. It was useful to help in the construction of the workshop as I built respect and familiarity with the shopworkers who have been crucial in helping me construct the seventeen foot turbine blades.
The first step in building the blades was to scale up the dimensions of the current blade designs and determine how many pieces of cedro macho wood were needed. I used Solidworks to make the virtual cuts into the wood and determine at what lengths I would need to cut each of the 2x4´s. The process of sawing and fitting the 2x4´s together was like somewhat of a jigsaw puzzle in that I tried to match the concavity of each piece of wood so that they sit flush against each other and do not create excessive strains on the epoxy resin that is used to hold them together.
After the wood pieces were matched together as best as possible, the epoxy resin was applied with brushes and clamped overnight to set. The result was a solid piece of wood that could now be planed down to the desired 2” thickness. From this thickness, the primary cuts along the length of the blade were made with a circular saw.
Next, the thickness of the back of the blade was tapered using a circular saw to cut to the desired thickness at each cross section. The remaining chunks were chipped away with a machete and sanded down with a grinder (This is where the privilege of having a band saw would have been useful). Carving the pitch on the front of the blade has been more of a challenge as the angle of the blade changes along the length of the blade. Dimensions were again scaled with Solidworks and traced onto the profile of the blade. A bench was made to allow for cutting of this section of the blade and the angle of the blade was adjusted using wedges of wood and calipers. This was a challenging process, as it is hard to make fine adjustments with wedges of wood, but the lack of precision can be made up for the subsequent grinding of the wood.
As of now, the backs of the three blades have been cut and grinded, and all but one of the blades has had the pitch carved. As soon as the last pitch has been carved, I will begin to carve the airfoil shape on the front of the blades. Additionally I have been designing a more robust way to assemble and dissemble the turbine blades to allow for easier transport and repair. Currently, the whole blade assembly is transported complete so that it remains balanced. However, the new seventeen foot assembly will be much heavier and challenging to transport and maintain if it cannot be disassembled. I will provide future updates on progress made in that area as well as the design of the rotor and stator molds that I will begin to work on shortly.
Although there are many challenges faced with the limitations of this environment including working with people who are illiterate, limited access to tools, and high humidity and rain, it has been a very rewarding experience. I have come to realize how much of a difference a few watts of power can make in the lives of people by giving access to refrigerated vaccines, having light for medical operations, and access to radio communication in community centers.
It was great to interact with the beneficiaries of this technology in Monkey Point where we worked on the repair of the refrigeration system charge controller and maintenance of the turbine. This experience makes me appreciate the facilities and privileges that I have grown up with and often taken for granted. I also realize that there is a great opportunity to introduce renewable energy into the developing world because there is no existing infrastructure to overcome. If a sustainable infrastructure can be implemented form the start, they are likely to have a much more successful future.