The Use of Finite Element Modeling to Increase Efficiency of Low Environmental Impact Hydropower

In low environmental impact hydropower, fluvial energy is converted into rotational energy of a turbine by placing the turbine directly into a river without the creation of a dam. The central problem of low-impact hydropower is its low efficiency, meaning that only a small fraction of fluvial energy is converted into rotational energy. Most approaches to improving efficiency have involved reducing frictional losses and forcing more of the water to come into contact with the turbine. However, the major source of inefficiency follows from conservation of mass. As the turbine extracts energy from the water, it reduces the stream velocity. Therefore, the water downstream from the turbine must become significantly deeper, which causes the water to flow back upstream toward the turbine. The objective of this study is to use finite element modeling to determine the improvements in efficiency that would result from the following innovative features for preventing backflow:

- The water exiting the turbine will be forced to rise up a step, which will drive the flow into the supercritical state in which pressure energy will be converted into kinetic energy that will accelerate the water away from the turbine.

- Some of the turbine energy or other source of energy will be used to drive the low-energy water downstream and away from the turbine.

- In contrast to the usual open-paddle design, the turbine will be enclosed and the low-energy water will be forced to exit through a vertical tube.

Results will be reported at the meeting.