villages in Indonesia, deemed as remote areas, still did not have access to the national grid electricity. To resolve this issue, the use of independent power plants is an appropriate solution. The use of a pico-scale Turgo turbine, which is an independent power plant, is recommended in Indonesia due to its mini-, micro-, and pico-scale water energy potential of 19 GW. As the Turgo turbine is intended for use in remote areas, the use of local materials, e.g., coconut shells, is proposed as the bucket material. From static compressive strength tests revealed that the maximum pressure points a coconut shell proportional to the water pressure with a potential power of 3300 W. The size of a coconut shell spoon, which is not uniform, can be overcome by its curvature angle. The curvature angle represents the relative angle of the incoming and outgoing jets, while this is a represents of the depth and length of the spoon. Thus, to ensure the performance of the Turgo turbine under maximum conditions, the curvature angle of the coconut shell spoon is ~90°. Moreover, the total efficiency of the turbine is 34.94%, with a possibility of reaching higher values.

The geography of Indonesia renders it difficult to connect many areas to the national electricity grid. To overcome these problems, people need to be able to generate their own electricity. Pico hydro has been proven to be a cost-effective solution for electrification. The Turgo turbine is known for its reliability and strength, and it can perform efficiently with a range of flows. The Turgo's blade consists of an inlet and outlet trail with a curve that joins them. The curve in this study will be made from a simple circle arc to improve manufacturability. Three blades were designed using a basic calculation derived from the velocity triangles, with each blade having a different circle radius. The Computational Fluid Dynamics (CFD) method is used to determine the stream flow through the blade at a level of detail that cannot be obtained using other methods. The boundary conditions used in the study include 2.7 meters of head and a 21 l/s flow rate, a steady-state homogenous multiphase, and the turbulent models used SST k-ω. The result shows that the Turgo turbine with a 60 mm arc radius generated 477.7 Watts and has an efficiency of 85.97%, the highest when compared to the other two blades that used 50 mm and 55 mm arc radii, respectively.

The computational fluid dynamics (CFD) method is a method often used in predicting the performance and flow field of turbine because it is cheap and fast. The accuracy of CFD method is influenced by several aspects: boundary conditions, discretization of space and time method, and the use of turbulence models. For turbulence model, there is no clarity of the most accurate model, especially in the pico hydro type propeller. Therefore, this study compared three turbulent models based on Reynolds Average Navier-Stokes (RANS) two equations to predicts the performance of a pico hydro propeller turbine: standard k-ε, Group Normalization (RNG) k-ε, and Shear Stress Transport (SST) k-ω. This study used a three-dimensional simulation method, transient, and six-degree of freedom features. The Grid Convergency index (GCI) and Time-step Independence Index (TCI) were used to verify the simulation results. From the results, the CFD results were similar to the experiment results (valid). Furthermore, there was different prediction of performance due to differences in the turbulence model but not too high. Based on this, for prediction of performance pico hydro propeller turbine, the standard k-ε turbulence model was recommended for use. However, for study flow field, RNG k-ε and SST k-ω were recommended because they were not over-predicted in the dissipation rate calculation.

The nozzle in a crossflow turbine is important because it accelerates the flow of the inlet and directs it to the runner at an angle relative to entrance angle (β1), which is used to obtain the maximum efficiency value. The β1 value must match the angle of the runner's outer blade considering the transfer of water from stationary to the rotating coordinates. To obtain the desired β1 value, the design of the nozzle is essential. In this study, 6-DoF simulations were conducted to find the best nozzle geometry. The incoming flow angles (λ) of the nozzle ranged from 50° to 90°. A study without a proper nozzle design was also conducted to compare the results. The results showed that a nozzle geometry of λ = 50° yielded the highest efficiency (60.6%). This study shows that the design of the nozzle in a crossflow turbine significantly affects its performance.

No abstract

In recent developments in the area of thermofluid technologies, active flow control has emerged as an interesting topic of research. One of the latest methods, which will be discussed in this paper, is the application of a plasma actuator. Plasma actuation is achieved by conducting a high-voltage electric current through an actuator device. Our research was specifically conducted to discover its effect on the reduction of the drag coefficient, with Ahmed Body the experimental object put inside a suction-flow wind tunnel with varying inputs of flow velocity. The plasma actuator device was run with an A.C. power supply and installed in three different placement configurations on the aerodynamic model to determine which most optimally affected the aerodynamic drag, while the drag coefficients were acquired via the use of a load cell installed as the harness for the aerodynamic model inside the tunnel. The results of the experiments include that the optimal configuration of the actuator placement was on the leading edge, the optimal wind flow velocity of the experiment, which was essential for the actuation to be observed, was at 1.7 m/s, and the resulting drag reduction percentage, as a result of induced flow, was 22% of the initial drag coefficient.

Breastshot waterwheel are considered as one of solutions for electrification in remote areas in Indonesia. Since it has low investment and maintenance costs, as well as an uncomplicated manufacturing process. Analytically, the optimum performance of this turbine occurs at the ratio of tangential velocity of wheel with the upstream velocity of water is 0.25-0.35 and numerically simulated the best efficiency is 62%. However, there is no experimental study for 16 blades of breastshot waterwheel in pico scale in actual river condition. The experiment is carried out in actual conditions with a discharge of 0.09708 m 3 /s and head 0.26 m. Based on results, the highest mechanical efficiency occurs at the ratio of tangential velocity of wheel with the upstream velocity of water is 0.83, while for electrical efficiency it was found at the 0.95. for U / C compared to the reference, the results are quite far from optimal and for efficiency the result is slightly lower at 45%.

No abstract