Fish Friendly Hydro-Kinetic Turbines

Sep 9, 2017   //   by admin   //   Knowledge Base  //  No Comments

This paper is about understanding the nature of turbine which shall be used to generate electricity but is also keeping certain impacts into considerations.

Hydro-kinetic turbines are the turbines which utilizes the mechanisms of converting the kinectic energy of the flowing water hitting on its blades which then passes the energy into its rotor or shaft which is a rotating vortex through which energy is converted into electricity. The minimum requirement for turbines to be able to generate energy is water’s current and water depth.

Water depth is one of the essential criteria for the energy to be extracted from a site. This is because of the rotor diameter is dependent on adequate water level above the installed device. Hence hydro-kinetic devices are submerged in locations with relatively steady flow throughout the year. It is ensured that such locations are not prone to serious flood events, turbulence or low water level periods.

One of the major disadvantage that was observed due to hydro-kinetic turbines was the threat created to marine life especially the fishes. The turbines with 5 to 18 fast spinning blades, separated by gaps which could strike and/or injure the fish and the gaps could trap them was not only impacting the fish population but also disrupting the ecological balance while also affecting the livelihood option for people who are dependent upon the fishes.

Research: in order to combat this common problem faced by many countries, a lot of research had been initiated. But the research in this field was dual faceated ie, it was conducted to seek increase in the efficiency of the hydro-electric while also to decrease the negative impact on the fish population.

This also has been a growing concern for the legal or administrative bodies specific to their respective regions. This has been specifically because the need for the energy can not be reduced but also the marine life can not be compromised. Hence to ensure fish would migrate safely up and down the stream passing through the turbine- many organisations were asked to submit research proposals.

Fishes react in different ways to different flow fields- turbulence, accerlation, velocity, direction.

Gorlov Hydro-kinetic turbine: is one of the many researches with promising results. Using the conceptual understanding from Darrieus Design – Gorlov Helical Turbine that uses vertical axis wind turbine as well as hydro-power applications.
This design actually uses the foils parallel to the axis which produces a power cycle. These foils present a constant angle of attack without any issue of the direction of the flow of water. This serves multi purpose such as it allows the turbine to spin at lower flow of velocity.

Using this principle, two designs were well conceptualised, tried and developed over time.
First was the Voith’s Minimum Gap Runner (MGR) design that was deisgned from Siemens Voith Turbine. Based on the Kaplan turbine this was designed to have blades with much smaller gaps between the runner and the turbine walls. This prevents the fishes to get trapped or crushed by the runner.

This design was researched in several different locations and brought to conclusion that the mortality rate decreased and the efficiency of generation of electricity increased rapidly.

Secondly, Alden Research Lab developed another approach wherein the runner blades are attached to the rotating shrouds. There is no gap between the wall and the blade tips eliminating the low pressure that occur near the blade tips. This eradicates any chance of fish being caught.
The strikes that the fishes experience was an issue which has been catered by the use of 3 blades which are longer than the conventional sizes. This looks like a cockscrew and moves slowly allowing the fishes to pass smoothly without compensating on the energy production.

Since the above research designs have been providing substantially positive results, it is still at the pilot stage. The research needs to be replicated at large levels to observe the reliability of the results obtained from the designs above.

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