Archimedean Screw Based Micro Hydro Power Plant (MHPP) Prototype with Turbine Elevation Angle Parameters

Electrical energy has a very important role in human life, but the electricity supply still needs to meet society’s needs fully. Many potential energy resources can be converted into electrical energy. One of the potential energy resources is the flow of water, which can be used for micro-hydro power plants in remote areas. This paper presents the results of an analysis of a prototype Micro Hydro Power Plant (MHPP) using a 3-blade turbine with a gearbox ratio of 2.8:1. The purpose of the analysis is to determine the greatest value of voltage, current, power, rpm, torque, and efficiency based on variations in the angle of the turbine tilt of 20°, 25°, 30°, and 35° at a water debit of 2.91 l/s and a generator in the form of BLDC 3 phase. The measurement results and data analysis found that the turbine tilt angle of 20° produced the greatest voltage, rpm, torque, and efficiency values. This is because the increase in the angle of inclination of the turbine results in an addition to the volume of the bucket so that the speed of the water flow in the turbine increases. As a result of the addition of this water flow, the turbine becomes heavier to rotate so that the efficiency value decreases.


Introduction
The community's need for electrical energy is very high and continues to increase yearly.In many countries, the electrical energy produced by power plants has been well managed, starting from the generation, distribution, and marketing of this energy to the public [1].In connection with the distribution of electrical energy, not all regions, especially in remote and most remote areas, get an electricity supply.Even though in some remote areas, several potential energy sources can be converted into electrical energy.One example of a potential source of electrical energy is the flow of a river that passes through this remote area.
For areas with such conditions, micro-hydropower plants can be a solution for electricity supply [2].There are various types of micro-hydroelectric power plants.Each of these types has advantages and disadvantages [3][4][5].One type of power plant is the Archimedes screw turbine power plant.Some of the advantages of the Archimedes screw turbine are that it can be used in rivers that are not too fast [6], does not damage the environment around the river [7], does not disturb the life of fish in the river [8], and so on.
Archimedes' screw turbine has been extensively researched and studied, theoretically [9] and experimentally [10].The results of this study indicate that the Archimedes screw turbine has a fairly good performance.Several analyzes and designs of Archimedes screw turbines have also been carried out to obtain better and optimal turbine performance [11,12].The advantages of the Archimedes screw turbine, which can be used in rivers that are not too heavy in remote areas, can also be combined with the use of solar energy to obtain an adequate energy supply [13].
Further research on the characteristics of the Archimedes screw turbine on various factors has also been carried out.As an example of research on the effect of the level of filling water (fluid) in the turbine on the characteristics and performance of the turbine [14], research on the effect of the flow of water (fluid) passing through the turbine on the characteristics and performance of the turbine [15], research on the effect of the slope and number of turbine blades on turbine characteristics and performance [16], and so on.This paper will discuss the results of making a micro-hydro power plant prototype and study the effect of the turbine elevation angle on the characteristics and performance of a micro-hydro power plant.The results of this study will complement the results of previous studies conducted by the authors and other researchers [17][18][19][20].Compared to previous studies, the novelty of this study is that a micro hydro power plant prototype has been made according to the conditions applied in the field (not laboratory conditions).Analysis of the characteristics of a micro hydro power plant includes mechanical characteristics and electrical characteristics.The studied mechanical characteristics are the amount of torque and rpm at various variations of the turbine elevation angle.The studied electrical characteristics are voltage and current to obtain generator power characteristics at various turbine elevation angles.

Tools and materials
The tools and materials used in the research are: 1. Water pump as a water supply 2. Multimeter as a measure of voltage, current, and electrical resistance 3. Tachometer as a rpm meter 4. Low rpm 3 phase BLDC generator 5. 3D printing as a turbine printer 6. Spring to measure torque value 7. Diodes and capacitors as a series rectifier 8. Resistors as the electrical load resistance 9. Ruler as a measure of the length of the falling water and the elevation angle of the turbine 10.Filaments (PLA) to make turbines and shafts 11.Reservoir tank above measures 61 cm x 43 cm x 15 cm 12.The reservoir tank below is a water reservoir from the turbine 13.Acrylic for making valves, gearboxes, and turbine casings 14.Thin aluminum for casing coating 15. 14 D pipe for making penstock

Microhydro power plant design
The prototype of the Archimedes screw turbine Micro Hydro Power Plant (MHPP) in this study is shown in Figure 1, and the dimensions of the prototype size are shown in Table 1.The block diagram, along with the names of the components making up the MHPP of the Archimedes screw turbine in Figure 1, is shown in Figure 2.

Research flowchart
Broadly speaking, the stages in the research can be described in the flowchart in Figure 3.In this study, measurements of the mechanical characteristics and electrical characteristics of the Archimedes screw turbine generator were carried out at various turbine elevation angle variations.The parameters always kept constant in this study are the height of the waterfall and the flowing water discharge.The parameters that are made as variables are the turbine's angle of inclination and the electric load's resistance.Variations in the angle of inclination of the turbine used are 20 0 , 25 0 , 30 0 , and 35 0 .Variations of electrical load resistance used are 0.98 kΩ, 2.14 kΩ, 3.2 kΩ, 4.6 kΩ, and 5.52 kΩ.

Torque Measurement
Measurement of torque in this study was carried out with a spring.The spring is used as the object for breaking the turbine.The spring used has a fairly large constant value.In this study, the spring constant value was 337.21 N/m.The change in the spring's length due to the turbine rotation's braking is used to obtain the torque value.

RPM measurement
Turbine rpm measurement is done with a tachometer.The tachometer has a light-sensitive sensor with a rotating element.The part of the rotor to be measured is marked with a different color.When the rotor rotates, the tachometer sensor is turned on, and the rotation value will be read digitally on the tachometer.

Measurement of Voltage and Current
Measurement of the voltage and current value generated from a 3-phase low rpm BLDC generator is based on the conversion of AC to DC.The output of the low rpm 3-phase BLDC generator is AC, which is then aligned with a converter in the form of diodes and capacitors to produce DC voltage and electric current.Voltage and electric current measurements use a digital multimeter at this DC voltage and current.Measurements were made with variations in the angle of inclination of the turbine and electrical load resistance.

Calculation of Electric Power
After obtaining the voltage and current data, the value of the electric power generated by the generator can be calculated.Electric power is calculated by multiplying the voltage and electric current.The electric power data generated by the generator is obtained from current and voltage data with five variations of electrical load resistance.

Measurement Result Data
The results of measuring the mechanical characteristics of the turbine generator, namely the turbine torque at several variations of the turbine tilt angle, are shown in Table 2, and the turbine rpm at several variations of the turbine tilt angle are shown in Table 3. Data from the measurement results describe the turbine generator's electrical characteristics.That is, the magnitude of the generator voltage at several variations of the turbine tilt angle is shown in Table 4, and the magnitude of the generator current at several variations of the turbine tilt angle is shown in Table 5.
Table 4 From the measurement results of the generator voltage and current, generator power can be calculated.The results of calculating the generator power at several variations of the turbine tilt angle are shown in Table 6.

Discussion
The spring constant used for measuring torque is 337.21N/m, and the radius of the turbine shaft is 0.06 m. Figure 4(a) presents a torque vs. turbine tilt angle graph from Table 2.There are fluctuations in the value of the turbine torque in that angle range.The fluctuating hydrodynamic forces of water cause this.The greater the height of the falling water (head), the greater the hydrostatic force.At an angle of 30°, the torque value increases due to the water discharge in the bucket between the helices, which is not constant.The torque value is higher when the water pressure in the bucket is higher.3. The greater the turbine tilt angle, the less the turbine rotation (rpm).This is due to the volume of the bucket between the helices.The more volume of water buckets between the helix, the greater the turbine's rotational speed.The greater the angle used in this research, the larger the bucket volume, which can sink the turbine.This causes the turbine to spin hard so that the rotation decreases.At an angle of 20°, the bucket volume reaches the optimal value because the water hits the active side of the turbine so that the turbine can rotate quickly.4. The graph shows that the voltage value decreases as the turbine tilt angle increases in this study.This is closely related to the decrease in the rpm value as the turbine tilt angle increases.Figure 5(b) presents a graph of current vs. turbine tilt angle from Table 5 on various variations of electrical load resistance.The graph shows that the current value decreases with the greater value of the electrical load resistance.This is to Ohm's law that the electric current will decrease if the electrical resistance increases.
Table 6 presents the results of calculating the electric power of the generator.As seen in the table, it can be seen that the resistance of the electrical load affects the amount of electric power produced by the generator.The smaller the value of the resistance of the electric load, the greater the electric power generated by the generator.The graph of electric power for variations in the angle of inclination of the turbine in Table 6 is presented in Figure 6. Figure 6 shows that the electric power decreases with increasing resistance to the electric load.In the range of variations in the angle of inclination of the turbine used in this study, the greatest torque, rpm, voltage, and current values were obtained at an angle of 20°.Specifically for electric power, the largest value occurs at an angle of 30°.Increasing the angle of inclination of the turbine causes an increase in the volume of the bucket so that the speed of the water flow in the turbine increases.As a result of increasing the bucket volume, the turbine becomes heavier to rotate.According to theory, the volume of the water bucket between the max helices is half the casing.If it exceeds this volume limit, the turbine will experience a rotation anomaly [9,12].
Previous studies using variations of the same turbine tilt angle, namely 20°, 25°, 30°, and 35° in a turbine with a shaft length of 15 cm, number of blades 2, and water discharge of 2.64 l/s obtained different results.In the previous study, the most significant torque, rpm, voltage, electric current, and electric power values occurred at an angle of 30°.Whereas in this study, a turbine with a shaft length of 30 cm, three blades were used, and a water discharge of 2.91 l/s [19].Changes in turbine design from previous studies were able to provide significant results.This is to the results of Muller's research and Rorres' research, which showed that increasing the number of blades can increase the torque, rpm, torque, power, and efficiency of micro-hydro generators [9,12].In general, the more the number of blades, the more power is generated.However, increasing the number of blades cannot be done continuously because there are limitations on the dimensions of the generator used.Rorres has formulated the optimal design of a micro hydro power plant [12].Further research needs to be carried out regarding this optimal design to find various design parameters for micro hydropower plants with Archimedean screws to obtain the most optimal electric power.

Conclusion
The measurement results and data analysis found that the turbine tilt angle of 20° produced the greatest voltage, rpm, torque, and efficiency values.This is because the increase in the angle of inclination of the turbine results in an addition to the volume of the bucket so that the speed of the water flow in the turbine increases.As a result of the addition of this water flow, the turbine becomes heavier to rotate so that the efficiency value decreases.
Further research needs to be carried out to test the prototype of this micro-hydro power plant in various real conditions in extra-varied river flows.

Figure 3 .
Figure 3. Flowchart for measuring the MHPP characteristics of an Archimedes screw turbine.

Figure 4 .
Graphs of (a) torque and (b) rpm vs turbine tilt angle.

Figure 4 (
Figure 4(b) presents a graph of the rpm value vs. turbine tilt angle from Table3.The greater the turbine tilt angle, the less the turbine rotation (rpm).This is due to the volume of the bucket between the helices.The more volume of water buckets between the helix, the greater the turbine's rotational speed.The greater the angle used in this research, the larger the bucket volume, which can sink the turbine.This causes the turbine to spin hard so that the rotation decreases.At an angle of 20°, the bucket volume reaches the optimal value because the water hits the active side of the turbine so that the turbine can rotate quickly.

Figure 5 .
Graph of (a) voltage and (b) amperage vs turbine tilt angle

Figure 5 (
Figure 5(a) presents a graph of the voltage vs. turbine tilt angle from Table4.The graph shows that the voltage value decreases as the turbine tilt angle increases in this study.This is closely related to the decrease in the rpm value as the turbine tilt angle increases.Figure5(b) presents a graph of current vs. turbine tilt angle from Table5on various variations of electrical load resistance.The graph shows that the current value decreases with the greater value of the electrical load resistance.This is to Ohm's law that the electric current will decrease if the electrical resistance increases.Table6presents the results of calculating the electric power of the generator.As seen in the table, it can be seen that the resistance of the electrical load affects the amount of electric power produced by the generator.The smaller the value of the resistance of the electric load, the greater the electric power generated by the generator.The graph of electric power for variations in the angle of inclination of the turbine in Table6is presented in Figure6.Figure6shows that the electric power decreases with increasing resistance to the electric load.

Table 1 .
Dimensions of the Archimedes screw turbine MHPP prototype.

Table 5 .
Current measurement results.

Table 6 .
Electric power from the generator.