Energy from tidal streams is a reliable renewable energy source worth exploiting. With increasing concern over the potential effects of ocean energy utilization on marine environment and organisms, several previous experimental studies have been conducted focusing on fish behavior and their collision risk with hydrokinetic turbines for power generation. This study is aimed at exploring the behavior of marine animals around marine current turbines (MCTs) in the sea environment by conducting a laboratory experiment based on similarity laws for the turbine tip speed and maximum marine animal swimming speed. Three rotation frequencies (0, 5 and 20 rpm) with two releasing areas (upstream and downstream areas) were considered in our experiment. Results showed that fish survival rate was 100 % after 48 h, and only one fish came into contact with the turbine hub and was inactive in front of it when the MCT was in a stationary state during our preliminary test of swimming endurance. Although both the initial releasing area of fish and the rotation speed of MCT have significant effects on fish passage count rate (PCR) via a turbine, there is no interaction between these two factors. PCR was generally higher when fish were put into the tank in the downstream area, irrespective of the turbine rotation. And the returning behavior in the downstream area was more frequently found compared with that in the upstream area, which indicates that the location of MCTs should be considered at the downstream of a channel in practice to reduce the potential risk of fish injury. The ratio of fish passing from the outer side (±3) of the turbine was larger, and a clear U-shaped distribution could be observed. The entering behavior almost disappeared (less than 1.3 %) when MCT rotated with a frequency of 20 rpm. It indicates the design of the rotation frequency of MCT should be more than 20 rpm. However, higher tip speeds and darkness conditions are not considered in our experiment. Based on the laws of similarity proposed in this study, it becomes possible to compare the experimental results with real sea results, to allow explanation and discussion of fish behavior around MCTs, through the parameters of flow velocity, turbine tip speed, and maximum fish swimming speed.
Impact assessment of marine current turbines on fish behavior using an experimental approach based on the similarity law
Title: Impact assessment of marine current turbines on fish behavior using an experimental approach based on the similarity law
June 01, 2017
Journal: Journal of Marine Science and Technology
Zhang, J.; Kitazawa, D.; Taya, S.; Mizukami, Y. (2017). Impact assessment of marine current turbines on fish behavior using an experimental approach based on the similarity law. Journal of Marine Science and Technology, 22(2), 219-230.