Alternative energy production is an important part of our future energy resources. Every effort to optimize efficiency is needed to meet the goal set by the president during the 2011 State of the Union Address of nationally consuming 80% clean energy by 2035.
I researched the mechanics of many water turbines and I identified that many types of turbines aren’t designed for use completely submersed in a water stream. These types of turbines require the use of a dam or placement of the turbine on the top of the water, which is costly or highly dependent on changes in the height of the water respectively. Almost every design that I found used a fin that did not change shape or position as it rotated around a wheel. I wondered if a dynamic (not static) fin could increase the efficiency and allow a turbine to operate completely submersed under water without a dam. This would decrease the resource cost (and length of time needed for a turbine to pay for itself) and would increase the range of water depth that a turbine could harvest energy.
I brainstormed that a plane-shaped fin perpendicular to the flow of water (a sail) would have a large drag which could absorb a significant amount of the energy in the stream. Also, the same plane, when turned to be parallel to the flow of water, would theoretically have no drag. I analyzed multiple methods of attaching the plane to turn a wheel which could minimize the drag of the plane while moving it against the current, but maximizing the drag of the plane while it moves with the current. I proposed and analyzed a geared design which would turn the plane-shaped fins proportionally to the rotation of the entire turbine and I mathematically derived a surprising gear ratio that theoretically delivers the optimum efficiency.
To test this design, I built a scale model out of household supplies. I also built a control model using a traditional fixed fin design of the same size. I tested these turbines at the University of Minnesota, St. Anthony Falls Laboratory (SAFL) using their 20 inch flume. I measured the power produced by each turbine using a motor attached to the turbine above the water. I used the following experimental variables:
Independent Variables: Turbine Design and Method for Energy Harvesting
- Control group: Traditional Fixed Fin Water Wheel
- Experimental group: Fully Submersible Geared Water Turbine
Dependent Variable: Power = Voltage2/Resistance
Constants:
- Size of turbine
- Motor used to measure power
- Flume
- Flume Speed
Based on the comparative data collected, I concluded that the new alternative water turbine would provide a viable option for increased energy collection and could expand the opportunities for extracting hydroelectric power.
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