Analysis and optimisation of screw turbine for very low head micro hydro applications
Creators: name: ERINOFIARDI, Erinofiardi
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401703
subject: Energy generation, conversion and storage (excl. chemical and electrical)

description: Ever-increasing energy demand and population have stressed conventional energy resources over the last few decades. Particularly in Indonesia, there is a huge energy crisis. However, there is also plenty of unexploited micro-hydro power generation potential. The main reason for the limited utilization of micro-hydro potential in remote areas of Indonesia is either the lack of access to, or the cost of required technology. In this research, screw turbines have been studied to establish their suitability for use in the remote areas of Indonesia. <br><br>
Screw turbines are among the most eco-friendly hydropower technologies for micro-hydro applications due to their simple design, suitability for low head applications, and low impact on aquatic life. They are famous for isolated power supply systems, especially small islands. The proposed application has been focused on scattered islands in Indonesia. These Islands have enormous unutilized low head hydro potential however they currently depend on fossil fuel sources for their energy requirements. Based on personal observation and experience of the scenario, a conceptual picture for switching the current energy load of isolated islands has been drawn. Financially, small energy requirements can be fulfilled with limited investment, ensuring minimal operational &amp; maintenance costs. Enabling the effective utilisation of these renewable micro-hydro resources would provide energy security for the region and open the door for further economic reforms.<br><br>
Analytical modelling in this study was focused on identifying a suitable method for theoretical analysis of the performance of the turbine. The resulting tool can be a strong support in estimating turbine performance along with the sizing of associated civil structures. Unlike other hydro turbines, screw turbines need not be tailor-made, however this also means that off the shelf turbines might not have performance data for the required operational range. In such cases, the empirical and analytical relations developed in this study will aid in predicting the actual performance based on available performance data. The tool can evaluate the effects of water level, speed, and the number of blades on the performance of the turbine. <br><br>
An experimental study was performed on 3D printed screw turbine models with one, two, and three blades. During the experiment, axial leakage phenomena were very noticeable, hence a novel design with lips along the edge of the blade was proposed. The experimental study involved evaluating the effect of water level and load on flow, speed, and power transmissions in three different turbines. Electrical step resistors were used as load and corresponding mechanical torques were measured.<br><br>
The proposed analytical model has good agreement with experiments at low-speed operation. This study will aid in the estimation of turbine size and performance. The screw turbine has a significant advantage when operated at low speed in cases where waterways support multiple industries or uses due to the low to zero impact on aquatic life, hence the considered model can be used as an effective tool for turbine design and sizing. The operational characteristics of the screw turbine are dependent on rotational speed, number of blades, and fill factor (turbine flow level). It has been found that the turbine has greater efficiency while operating at higher speed, three blades, and a fill factor of 1. Practically, it is undesirable and unsafe to operate these kinds of turbines at high speed. However, the benefit from increasing the size of the turbine while maintaining a lower speed, as well as the flow on benefits in terms of minimal environmental impact can outweigh the reduced efficiency. Replacement of existing fossil fuel-dependent energy sources with micro-hydro ensures sustainability, economic energy, and environmental acceptability.