Introduction: An Experimental Study of Electricity Generation Using a Horizontal Spiral Turbine

About: "Nothing is created, nothing is destroyed, but everything is transformed"

This study aimed to develop horizontal spiral turbines for generating electricity by designing spiral turbines using the Golden Ratio function. The study analyzed the impact of the diameter-length ratio and the number of the turbine’s blades (2 – 6 blades) on the torque of turbine. Then the prototype of the spiral turbine with a 0.6 meter diameter and 0.9 meter blade was designed to generate electricity with a water velocity of 1, 1.5 and 2 m/s in order to compare to the propeller turbine which had an identical diameter size. The results indicated that a 3-bladed spiral turbine with a 2/3 of diameter-length ratio of turbine had maximum torque at 1 m/s of water velocity. The spiral turbine produced an optimal efficiency of 48% which was 15% higher than that of the propeller turbine.

Step 1: Introduction

Hydro energy is a potentially clean and friendly environment energy resource. Energy from water circulates with maximum energy compared to other kinds of energy resource circulation. The amount of energy can be controlled by adjusting the level of Head and flow rate which can be managed by calculation and assignable design principle. Currently in many countries, the development of hydro power plants by constructing dams is not so simple due to the high cost of investment, the impact to the ecosystem, community opposition and many constraints.

Transforming the kinetic energy of the hydro power is one of the alternative energy technologies; hence, there are concepts of using the energy of the hydro power such as canals, rivers, ocean and the flow of irrigation canals. By having suitable water supply management and technology, generating energy is possible from these alternative resources which are high potential energy resources. Due to the mentioned circumstance, there was a trend of utilizing hydro energy from small water resources or streams by developing a turbine for simple implementation at irrigation canals for electricity generation. However, the canal flow rate and slope are low. Hence, designing a turbine which is appropriate for slow velocity or very low Head is needed.

The research mentioned that hydro energy was the best alternative energy resource that could be transformed into electricity, and it was able to be more developed and has a more effective design when the focus is on increasing the output of the turbine by the least force. The number of researchers who are interested in turbine designs for irrigation canals therefore increased, and many kinds of research focused on designing and developing turbines into various patterns to catch energy from water flow to generate the most electricity.

This kind of turbine is also safe for marine animals, and it blends well with the original ecosystem. Having a small radius creates little traction force. The water receiving area and the well-connected blades were suitable for low velocity, so this type of turbine was stronger and more suitable than the others which had a small sized water receiving area. However, there is very little research which is related to the horizontal spiral turbine. Therefore, this study experimented with generating energy from a spiral turbine and comparing that to the ordinary propeller turbine, and this study analyzed the optimal number of turbine blades for electricity generation from low velocity

Step 2: Horizontal Spiral Turbine

Designing Spiral Turbine Using Golden Ratio

The spiral turbine was designed to whirl around the core using the Golden Ratio function which is a general
natural Mathematical serial number. With this, the width of the blades was expanded at a ratio of 1.68 (the blade in every semi-circle of turning the axle or to 180 degrees.) The ratio to the shape of the turbine was the number of blades. When it turns one full round around the axle or 360 degrees with a stable length, the number of blades is assigned a pitch. If the number of blades increased then the pitch that was assigned decreased. On the other hand, when the number of blades were less then the pitch distance increased. Hence, at the same length of the turbine and the optimal number of blades, the best production power was possible. The spiral blade turbine of the Golden ratio function feature is shown in figure above.

Turbine Torque and Efficiency

Turbine torque ( t ) can be calculated from this equation : t = wr
By w is the speed of turbine rotation and r is the length of the blade from the center point of the turbine, ( Pt ) is the maximum power that the turbine can intercept and is able to be calculated from the following formula: Pt = 0.5926 * (1/2)d AV^3 .

When d and V are density and water velocity, A is the cross sectional area and invariant 0.5926 is the coefficient variation of maximum power (Cpmax) or Betz Coefficient. So efficiency of the turbine (K ) can be calculated by K = P/ Pt , where P is the actual turbine output.

Step 3: Equipments and Methodology

Equipments and Experiment in Laboratory level

Equipments in the controlled laboratory consisted of water gutters made from clear acrylic resins which
provide vision to observe water flow and velocity measurement as shown in Figure 2. The turbine was made from hard plastic with a 10 centimeter diameter and there were 5 types of blade strands as shown in Figure 3 : 2 bladestype, 3 blades-type, 4 blades-type, 5 blades-type, and 6 blades-type. In addition, the study tested the turbine with D/L = 1/2 and 2/3. Where L was the ratio of the length of the spindle, and D was the diameter of the widest diameter of the turbine. The study controlled the velocity of the water to be 0.5, 1, and 2 m/s, respectively. Then the speed of rotation was measured and this was used to find the torque of turbine. The experiment tested 5 types of spiral turbines by the order of blade numbers in order to find the ratio of width to the length of the turbine (D/L) and to find the optimal number of blades for the best prototype design of water turbines for electricity generation.

Step 4: Equipments and Methodology

Equipment and Turbine Prototype Testing in the Irrigation Canal

According to the laboratory observation, creating a prototype of water turbine for irrigation canal
experiments by applying the theory of dimensional similarity results in a relation equation of power and size such as the following:

( Pmodel / Pprototype ) = ( Dmodel / Dprototype )^2

Where Pmodel and Pprototype are Turbine output model and Turbine output prototype, Dmodeland Dprototype are Turbine diameter model and Turbine diameter prototype, respectively. From the above relationship, the size and ratio of the spiral turbine can be assigned for the test of 0.6 meters diameter with the length of 0.9 meters, and the study also created an ordinary propeller turbine for an efficiency comparison. In the electricity generation experiment system, there were spiral and propeller turbines as shown in Figure above. An electricity generator of 200 W was installed to the turbine structure with pulley conveyers reduction systems of 1:4. Two different types of turbines were put into the irrigation canal and were conducted to compare the efficiency of electricity generation and turbine efficiency.

Step 5: Result and Discussion

Turbine Torque

According to turbine testing on the gutter in the laboratory for the ratio of optimal turbine appearance, the
study found that the appropriate number of blades was 3 with maximum torque at water velocity of 2 m/s which is equivalent to 81.64 x 10-2 N.m. The ratio of the diameter to the length of the turbine (D/L) is 2/3. Torque increased when the velocity of the water increased from 0.5, 1, and 2m/s, respectively. The results are shown in Table.

Step 6: Result and Discussion

Turbine Efficiency

The experiment of electricity generation by prototype turbine with 3 blades (0.6 meters diameter, 0.9
meters length) having an optimal ratio according to the results from the laboratory was conducted to test electricity generation at water velocity of 1, 1.5 and 2 m/s, respectively. The 3 blades-type turbine contributed maximum generation of 40, 84.4, and 192 W. Total efficiency were 48%, 30%, and 28.77 %. In terms of the propeller turbine, maximum generations were 28, 68.8, and 204 W. Total efficiency were 33%, 24.7%, and 31%. Water velocity of 1, 1.5 and 2 m/s contributed results as shown in Table, and Figure demonstrates the efficiency of the spiral and propeller turbines. As a result, the spiral turbine had more efficiency than the propeller turbine when tested with a water velocity of 1 and 1.5 m/s.

Step 7: Conclusion

This study developed a horizontal spiral turbine which had the feature of spiral blades around a turning axle. The

turning axle was placed parallel to the direction of the water flow. The blades’ radius expansion was designed by applying the Golden Ratio function. The experiment analyzed the optimal ratio of the diameter of the turbine (D) to the length of the turbine (L) by developing 2 ratio models (D/L) of 1/2 and 2/3 to test with 2-6 stranded turning turbines with a stable number of blades. Results at different velocities in the laboratory showed that the optimal number of blades were 3 with the ratio of the turbine diameter to turbine length (D/L) of 2/3. After creating a prototype turbine to compare electric power and efficiency between the prototype and propeller turbines, at a water velocity of 1 m/s and 1.5 m/s the prototype had more electric power and efficiency of 45.5% and 21.46%, respectively. Horizontal spiral turbines were suitable for low speed of water. The shape of strands of the turbine are capable of generating energy from low water velocity; therefore, it is appropriate to utilize it with water resources or irrigation canals which have a water velocity of less than 2 m/s.