Artículo Científico / Scientific Paper https://doi.org/10.17163/ings.n29.2023.09 pISSN: 1390-650X / eISSN: 1390-860X DESIGN OF A MICRO-HYDRAULIC GENERATION SYSTEM BASED ON AN ARCHIMEDES SCREW DIEÑO DE UN SISTEMA DE GENERACIÓN MICROHIDRÁULICA BASADO EN UN TORNILLO DE ARQUÍMEDES
 Alan Cuenca Sánchez 1, * ,Willian Farinango Galeano 1, Joan Murillo Zambrano 1.

 1,*Escuela de Formación de Tecnólogos, Escuela Politécnica Nacional, Ecuador. Corresponding author ✉: alan.cuenca@epn.edu.ec.   Suggested citation: Cuenca Sánchez, A.; Farinango Galeano, W. and Murillo Zambrano, J. “Design of a micro-hydraulic generation system based on an Archimedes screw,” Ingenius, Revista de Ciencia y Tecnología, N.◦ 29, pp. 98-107, 2023, doi: https://doi.org/10.17163/ings.n29.2023.09.

 Table 2. Inertia of the turbine as a function of the percentage of the contact area [21]   3.1.3.  Theoretical torque and power   Figure 1 shows the horizontal thrust force exerted by the water (FX), the tangential force exerted by the water (FZ), the thrust force in the direction of the X plane (FR), the force exerted by the water on the housing (Fy), the vertical force (W) and (α) the angle external to the helix [21].   Figure 1. Forces that act on an Archimedes screw [21]   If the relationship between the XZ plane is considered, the relationship given by equation (2) may be obtained.     Where the tangential force (Fz) together with the inertia of the blade (YC), describe the torque generated at the moment of contact of the water with the screw, thus obtaining equation (3).     Equation (4) may be obtained analyzing the tangential force (FZ); this equation describes the torque of the screw considering the effects of the water, the height, the contact area and the angles. Where T is the torque of the turbine in (Nm), ρ is the water density in (kg/m3), LT is the total length of the turbine in (m), whose value is assumed based on technical criteria of design, materials, manufacturing feasibility and versatility, Θ is the inclination angle of the turbine in (°) and h is the height of the hydraulic head; LT, Θ and h are shown in Figure 2.   Figure 2. Dimensions considered for the turbine   On the other hand, the theoretical mechanical power of an Archimedes screw may be also expressed as shown in equation (5).     Where T is the torque obtained from equation (4), and ω is the angular speed in (rad/s) given by equation (6).     Substitution of equations (4) and (6) in equation (5) yields equation (7), which describes not only standard variables as in equation (1), but is also makes emphasis on the contact area, inertia, angles and lengths.     In order to obtain the angle α, it is considered that the efficiency should be assumed in this case due to various factors such as friction, weight of the turbine, the environment, etc. Hence, equation (8) gives the efficiency of a turbine.     Where η is the efficiency of a turbine and Ptheoretical_max is the maximum mechanical power that can be reached by the turbine in (W). Simplifying equation (7) and substituting the result in both variables of equation (8) yields equation (9), where it

 can be observed that tan2 (α) is 1 in the numerator because the maximum angle α should be 45°.     From Figure 2 it is determined that the height is given by equation (10):     Considering equation (10) and substituting and simplifying equation (9) results in equation (11), which can be used to determine the value of the external angle (α):     The theoretical torque and power that may be obtained from an Archimedes screw turbine can be found using equations (4) and (7).   3.1.4. Dimensions and modeling   It was adapted an Archimedes screw with three threads and two revolutions along a plastic shaft with a length of 0.76 (m), according to the base design taken as reference. This piece was divided into two sections that may be coupled. Figure 3 shows the Archimedes screw; it does not have a solid filling and has a thickness of 0.003 (m) in its shaft and a thickness of 0.002 (m) in its helixes. In the lateral end it has a hole to attach the turbine with respect to a metallic shaft.   Figure 3. Archimedes screw hydraulic microturbine   A prototype of the existing microgeneration turbine was taken into account for the design of the microturbine. The corresponding geometrical specifications were adapted to the proposed design, and such features are specified in Table 3. Table 3. Features of the hydraulic microturbine   Measures to prevent friction in rotating parts include maintaining the bearings lubricated and protecting the metallic parts from rust, since in Archimedes screws it is of vital importance to avoid friction, especially in the helical helixes, because of efficiency issues [22]. A metallic structure, with the dimensions shown in Table 4, was designed to fix the bearings that bear the microturbine. This structure is the support of the water stream channel and the microturbine, and also holds the generator and the electronic circuit. Such structure is associated to auxiliary mounts that define the inclination and equilibrium of the surface on which the entire turbine-generator system will be deployed.   Table 4. Features of the hydraulic microturbine   Once the purpose of the base metallic structure has been defined, the plane of its final design is obtained (Figure 4).   Figure 4. Support base of the hydraulic screw   Figure 5 shows the 3D model of the microturbine. An insulated container is placed in the back of the metallic structure to hold the generator and the electronic circuit. In addition, it can be observed the auxiliary metallic structures to set the inclination of the hydraulic turbine, and even fix the hydraulic pump and the water storage tank for laboratory tests. Such structures may be removed for operation in a stream or creek.

 Figure 5. Rendered design of the microgeneration system   3.2.      Electric-electronic system   A water recirculation system was used for the laboratory tests, and thus a storage tank was arranged to receive and discharge the fluid by means of a 372.85 (W) hydraulic pump. A brushless DC motor (BLDC), whose main parts are shown in Figure 6, was used to produce electricity. This BLDC is operated as a generator without velocity multipliers, and is coupled to the back of Archimedes screw. This element adapts to the revolutions by means of a direct mechanical coupling provided by the turbine; in addition, the inclination of Archimedes screw and the flow rate that enters the turbine through the helixes have influence on the conversion from mechanical energy to electrical energy.   Figure 6. Permanent magnet synchronous motor [23]   It was designed the electronic circuit for the voltage rectifier circuit that will supply the loads. This circuit has stages for rectifying, filtering and linearizing the alternate voltage wave at the output of the generator. In addition, a step-up DC–DC booster converter (MT3608) was incorporated to regulate and amplify the filtered DC voltage waves. The electronic scheme is shown in Figure 7.   Figure 7. Electronic scheme of the full-wave AC-DC voltage rectifier   4.      Results and discussion   Taking into account all the parameters, features and requirements of the hydraulic microgeneration technology, a cost-effective and easy to replicate didactic system was built capable of using a water resource to generate up to 8 (W), supplying the demand of 6 (V) LED lighting loads. The system may be easily disassembled for its transportation from one place to another when it is required to observe its operation, either in the laboratory or outdoors. In addition, the system designed and built represents an innovative and efficient solution that may be improved for generating electricity from unconventional renewable sources The hydraulic screw was made through 3D printing (Figure 8) in fused deposition modeling (MDF), using polylactic acid filament in the entire structure of the hydraulic microturbine.   Figure 8. Metallic structure that supports the microgeneration system

 Figure 9 shows the system built and operating in the laboratory, the demand (6V LED lights) is satisfactorily supplied using to the inlet flow of water that is recirculating through the system.   Figure 9. Metallic structure that supports the microgeneration system   En la Figura 10 se observa el sistema construido y funcionando en laboratorio, la demanda establecida (luces LED de 6 V) es abastecida correctamente gracias al flujo de agua de entrada que se encuentra recirculando por el sistema. Si bien el sistema de microgeneración cuenta con una bomba de agua para un circuito hidráulico que recircula el agua, esto sirve para emular el medio físico donde se instalaría dicho sistema y realizar las respectivas pruebas de funcionamiento en laboratorio. Para la adaptación y utilización del sistema en lugares externos al laboratorio no son necesarios estos componentes por lo cual se pueden desmontar fácilmente, ya que lo único que se necesita es la presencia de un riachuelo y la colocación del generador para el paso de agua (Figura 11).   Figure 10. Hydraulic microgeneration system As a constant flow rate (minimum) of 0.583 (l/s) enters the turbine, it rotates at a speed in the range from 18.85 to 20.94 (rad/s) with the corresponding coupling to the generator. As a flow rate (maximum) of 10 (l/s) enters the turbine, it rotates at a speed of approximately 220 (rad/s).     Figure 11. Microhydraulic generation system installed in a stream   Tests were carried out for different inlet flow rates, measuring the power generated to supply a particular load. Table 5 and Figure 12 show the power generated by the microturbine built in this work, as a function of the inlet flow rate. The power generated was established through operation tests, which show that as the inlet flow rate increases so does the power. With the minimum flow rate of 0.583 (l/s), a current of 0.4 (A) and a voltage of 6 (V) were obtained, which can be used to supply a LED light with these specifications, whereas the maximum flow rate enables supplying up to 3 LED lights. Although there are various systems to supply the power demand without connecting to the electric network, even obtaining higher levels of power, the microturbine built represents a very attractive alternative for school students to get involved in the area of microhydraulics. This type of technology is capable of recovering the energy from a great variety of small water jumps, and its installation and maintenance costs are very low compared to other renewable energies. The system presented in this work is feasible because it uses low-cost materials; in addition, the technical information presented in this paper constitutes a basis to build, replicate and repower a system, that can also adapt to different environments, indoors or outdoors. These results evidence that the objective of the microgeneration didactic system was fulfilled, which is to contribute to the development of students’ knowledge about renewable energies, by means of the supply of the demand of lighting loads from the kinetic energy of water. Figure 13 shows the training of students from the Escuela de Formación de Tecnólogos (ESFOT) of the Escuela Politécnica Nacional, in the operation of the system.

 Table 5. Values of power generated as a function of the inlet flow rate   Figure 12. Power generated by the microturbine vs. inlet flow rate   Figure 13. Students observing the operation of the microgeneration system in the laboratory   The installation of a rectifier was considered to supply the lighting load, in order to avoid the intermittency in the lamp used and to stabilize the power delivered by the generator. Consequently, based on the microturbine design specifications, there are losses due to different factors, such as the friction, resistance of the generator, weight, etc., which cause losses in the stage of transformation from mechanical to electrical energy. Nevertheless, hydrodynamic screws exhibit high efficiency regarding generation of electricity for larger operating ranges, reaching 90% with little disturbances in the flow rate; in addition, its efficiency increases according to the design volume. The system built is a contribution to the development of knowledge about microhydraulics, since the results obtained enable to verify that the module operates correctly and that it may be used for teaching activities in laboratory practices. In addition, it should be pointed out that the operation tests have been carried out with the system to recirculate the water (pumps, pipes and storage tank) in the ESFOT laboratory and in a stream in the locality of Guayllabamba, being able to satisfactorily supply lighting loads. Therefore, it is stated that the didactic microturbine implemented in this work may serve as a base to extend the system to real applications in areas isolated from the electric network, taking into account the demand that should be fulfilled. An aspect that should be considered is the energy storage system that would be used by the lighting load during dry seasons; however, a continuous and stable presence of the water resource has been considered for the present project, i.e., it is used the energy produced when the system is operated.   5.      Conclusions   Based on the values obtained and on the implementation of the microgeneration system, it is emphasized that the water flow is the resource used to produce movement, as it was verified in the tests carried out with a water flow rate of 0.583 (l/s), in which the screw moved at a considerable speed. However, a higher efficiency is obtained when the flow rate is increased, generating better torque and a power of up to 8 (W) to supply a larger number of loads connected. The microgeneration system based on an Archimedes screw enables to supply up to three LED lights of 6 (V) and 0.4 (A). Although it is a didactic system, it could be improved and its performance extended to supply a larger demand. The turbine was thoroughly calibrated and adjusted, so that there is no direct contact of the turbine with the metallic structure and also to guarantee that it is as centered as possible at the moment of starting operation. The dimensions of the general system were defined and mechanical design planes were made for the corresponding description.