Utilization of river current for small scale electricity generation in Bangladesh

Abstract

The power crisis in Bangladesh and elsewhere in the Third World highlights the need for new technologies, which local communities can use to improve their lifestyle. Many arid , \ areas are characterized by having large rivers or canals flowing through them. Under this project a study has been performed to assess the potential of electrical energy from river currents at different locations of Bangladesh. In this context 23 sites of different rivers have been considered as test cases. After getting an idea about the river current velocity at different rivers in Bangladesh, this thesis describes the development of a new, simple, and relatively inexpensive technology, which if used in right circumstances, can generate power from the rivers. The water current turbine- just can be thought of as a wind turbine inserted into the river current- a model of which has been tried and tested for power generation. The technical details especially the aerodynamic design of the turbine rotor has been introduced in the thesis. The turbine model consisting of three NACA 4412 blades with average rotor radius of 221 mm has been tested for harnessing the kinetic energy from water. It should be mentioned here that no twist angle has been introduced in the blade. A chapter of this thesis devoted to analyze the performance of the model illustrates the working range of a water turbine in terms of tip speed ratio under certain river current velocity and the effect of pitch angle in power generation. It has been found that the turbine will run at tip speed ratios between 3.2 to 6 when the pitch angle is 5° and the river current velocity of 0.65 m/s. But this operating region squeezes if the pitch angle is reduced to 00. Also the peak value of the power coefficient (Cp) is 40% when the pitch angle is 5°, but when there is no pitch angle power coefficient reduces by 10%. If the turbine is operated at a very low river current velocity in that case there is a remarkable shifting of the operating range. At a river current velocity of 0.25 m/s, the turbine will run at tip speed ratios between 0.7 to 2. Hence, the conclusion is drawn that selection of the turbine rotor should be such that the rotor can rotate at a high speed as possible because the faster the loaded rotor turns the cheaper will be the transmission.