We are currently looking for research students to work on a collaborative effort between RAEL and NGO in Nicaragua called blueEnergy. We will be helping to redesign a wind turbine which they produce and sell to remote villages along the Caribbean coast near Bluefields.
We need motivated students to explore the following problems. If you are interested, you may contact Dan Prull at prull at berkeley.edu
Blade Materials
The current blades for the blueEnergy wind turbines are made from wood. There are a number of
limitations that come with hand-carving wooden blades. Due to logging restrictions on the coast,
purchasing knot free wood that is of a high quality is often difficult. Hand-carving individual blades is
very labor intensive and it is virtually impossible to create blades which are identical. Deviations of
only a few percent in the thickness of a blade can drastically change its aerodynamic characteristics.
The inherent imbalance between the three wooden blades of turbine thus causes unequal loading,
fatigue and in some cases turbine failure. In addition, even with sealants, the wooden blades are
susceptible to degradation from sun, water and particulate damage. Switching to fiberglass blades
created from molds will reduce construction time, lead to greater equivalence per blade and allow for
increases in structural strength and lifetime. Two mechanical engineering undergraduates are currently working on the engineering designs for the fiberglass blades as part of a class project. We need interested research students to help fabricate and refine these designs. These fiberglass blades can then be field tested and refined as their performance is compared to that of the standard wooden rotor.
Blade Design
The evolution of blade design for maximum energy capture has improved significantly during the last
2 decades, with extensive research done at several national labs to develop a series of airfoils
appropriate for large scale wind turbines. Unlike airplane wings, turbine blades
typically operate at lower Reynolds-numbers and have differing relative air velocities along their
chord length. The current design of the blade being utilized by blueEnergy was chosen due to its
simplicity of shape which makes it appropriate for hand carving out of wood. However, it is based
on a 1930s airfoil designed for airplanes, with lift/drag ratios inferior to those from modern airfoils
shapes designed explicitly for wind turbines.
Testing done in Nicaragua in 2006 revealed that blueEnergy’s machines are operating at about 20-
25% efficiency over a variety of wind speeds, whereas optimally designed small wind turbines can
perform at close to 40% efficiency. Using finite element analysis and computational fluid dynamics
algorithms, researchers have had success increasing relative blade efficiencies from 20-100% above
more simple airfoil shapes for these small wind turbines. There is also the need to determine what capacity of turbine would be most appropriate for mini-grid installation, and that can still be locally fabricated. We need researchers with some aerodynamics knowledge/interest to help redesign a more appropriate rotor for these machines.
Generator Modification
In 2006, blueEnergy began building a new larger 1kW-rated turbine design. Unlike the smaller
turbines that they had been installing, the 1kW versions have had several failures due to overheating
of the stator coils in the permanent magnet generator. There are a number of viable solutions that
can address this issue, including changing the geometry of the magnets and coils or moving from a 3
to 5-phase generator. This design change would effectively reduce the power flowing through the
stator wires. This is a high-priority task to ensure the reliability of the machines. Unfortunately,
blueEnergy does not currently have any staff experts in motor design or the operating budget to
contract a design solution. We need students with a good grasp of E&M to help find the issues with the current generator design and help redesign a new generator. We have a wind turbine generator test unit in the lab that can be used to compare designs.
Lab Setup
We will be field testing the blueEnergy turbine design(s) at our lab facility at the Richmond Field Station. The turbine and 85’ tower will have various sensors attached to monitor voltage, current, active and reactive power, temperature, wind conditions (speed, direction, shear), and pressure. These sensors all need to be mounted to the tower, and wired through to the DAQ interface in the lab. We currently have a mechanical engineering undergraduate student designing the data acquisition algorithm in LabView. We need students to help attach sensors, weld cross-arms, run cabling and finish the DAQ setup. We also need student(s) to help modify our wind turbine generator test stand to accept more generator sizes. This work would involve designing and ordering unistrut pieces and assembling the unit.