Low Water Head Research Articles

Design and Development of a Smart Vortex Turbine

The growing demand for clean energy has led many engineers and scientists to find a way to effectively generate and distribute electricity without any carbon footprints. One of the most prominent and widely known methods of generating electricity is Hydropower. One of the leading researches in harvesting energy from low-head water sources is through a gravitational vortex turbine. Gravitational vortex turbine is special type of micro-hydro turbine that relies on the rotational energy of a water vortex. This research delves into techniques required to increase the efficiency of vortex turbines. This project bolsters an extensive design methodology used to finalize a system of smart vortex turbine. It includes a section on CAD modelling and governing equations followed by an ANSYS simulation to predict and study the vortex generated in main tank. The main goal of this project is to achieve a water tight sealing to ensure that generator does not gets damaged. In addition, reducing mechanical losses due to vibrations by using a smaller shaft is one of the set targets of this project. Our mission is prove that electricity can be generated in off the grid communities with low-head water sources by using 3D printing as Pakistan does not have the modern expensive fabrication techniques to manufacture complex geometries. There is a need to look for a cost effective, efficient and green manufacturing method.

Numerical and experimental investigation of 3D unsteady flow fields of a low head axial flow turbine under different blade number

Low-head axial flow turbines (LHAFT) are important turbomachines suitable for converting low-head water (potential energy) into mechanical (kinetic) or electrical energy. The performance characteristics of this kind of turbine are an essential aspect of its design and operational life cycle. Nevertheless, pressure fluctuations within the turbine affect its operational reliability. Hence its fluctuation characteristics cannot be overlooked due to its influence on vibration, noise, and severity of performance. It is essential to investigate the zones associated with high unsteadiness and turbulence. Furthermore, blade number and variation in flow rate are other important, influential factors on the level of pressure fluctuations. Given the above, numerical and experimental investigation of pressure fluctuation intensities within the flow channels of the LHAFT model under different blade numbers was carried out in this study. The results posit that the pulsating pressure coefficient decreases gradually from the inflow to the guide vane but increases at the runner, then falls as the flow progresses in the outlet pipe. At the runner, the flow experienced the most irregular flow patterns in the turbine. All three runner cases were operated with nine guide vanes, but after one complete revolution, blade numbers z = 2, 3, and 4 revealed regular pressure fluctuations, respectively, in the stationary part (guide vane, inlet and outlet pipes). Regardless of the case study, nine (9) regular peaks and valleys of pressure pulses matching the number of vanes on the static vane were recorded in the runner flow passage. The flow interaction between the static vane and runner is responsible for the pressure fluctuation, which influences the turbine’s vibration and noise. The obtained results would be an essential reference to noise and vibration analytical studies in turbines to optimize them for improved operational reliability.

Development of the Dethridge Wheel Blade Shape for Hydropower Generation in Irrigation Canals in Indonesia

Consumption of electrical energy continues to increase along with population growth. As a result, various sources of electrical energy are utilised to meet these needs, especially in areas that have not been reached by the national electricity network. In countries with hilly geography and irrigation canals, pico hydro energy is often considered an alternative. One of the tools used to convert water flow energy into electrical energy is the Dethridge wheel. The Dethridge wheel is a simple waterwheel that is easy to manufacture and suitable for irrigation canals with very low water head heights. This study aims to increase the performance of the Dethridge wheel by changing the shape of the wheel blades and examine the effect of the variation of water flow rate in the channel. Experimental and numerical methods were used to investigate the potential of the developed wheel. The Dethridge wheel and its development were tested using an artificial irrigation canal with flow rates of 20, 30, 60, 90 and 120 m3/h. Furthermore, a three-dimensional numerical model of the Dethridge wheel was simulated using Ansys Fluent 18.2 software. The highest efficiency of the experimental Dethridge wheel, 55.6%, was achieved when the flow rate was 30 m3/h. The developed Dethridge wheel efficiency increased to 71.72%. These results are also in agreement with the simulated model.

Multi-Objective Optimization of Back-to-Back Starting for Pumped Storage Plants under Low Water Head Conditions Based on the Refined Model

Pumped storage plants (PSP) must switch frequently between various working conditions. Moreover, PSPs can fall easily into an S-shaped zone under low water head conditions, especially during back-to-back starting (BTBS), which reduces the stability and safety of unit operation. In this paper, a nonlinear PSP model for BTBS is established by combining an electrical subsystem with a refined hydraulic-mechanical subsystem. The influences of the hydraulic, mechanical, and electrical factors on the BTBS process are investigated quantitatively. Choosing the speed overshoot and speed stable time as the optimization objectives, and considering a variety of constraints, the multi-objective particle swarm optimization (MOPSO) algorithm is introduced to study and optimize two typical startup strategies. The results show that: (1) The parameters of a hydraulic-mechanical-electrical system have a significant impact on BTBS process, and the most unfavorable working condition corresponds to the lowest water head; (2) In the control schemes, a novel constant excitation voltage strategy is proposed based on the multi-objective optimization scheme. Compared with the constant excitation current strategy or single-objective, the optimization strategy proposed can considerably improve the speed overshoot and the speed stable time by at least 68.27% and 3.22% under the worst working conditions. (3) It is further verified that the problem of trapping in the S-shaped region under various working conditions may be avoided by the obtained optimal control scheme. The results give prominence to the effectiveness of the proposed optimization strategy for maintaining the safety and stabilization of PSP operation.

Design and performance of very low head water turbines using a surface vorticity model algorithm

This study explores the numerical optimization of water turbine runner profile performance using a surface vorticity model algorithm. The turbine is designed on a laboratory scale and operates at a net head of 0.09 m, 400 rpm, and a water flow rate of 0.003 m3/s. The initial design of the turbine runner was optimized to minimize losses in the hydrofoil. The optimization algorithm is coded in MATLAB software to obtain the optimal stagger angle that will be used in the water turbine design. Furthermore, design validation was performed using computational fluid dynamics analysis ANSYS CFX to determine the water turbine performance. The settings used in ANSYS CFX include the reference pressure of 1 atm, turbulence model shear stress transport, and inlet boundary conditions using total pressure and static pressure outlet boundary conditions. The computational fluid dynamics analysis reveals that by optimizing the design, the efficiency of the water turbine increases by approximately 2.6%. The surface vorticity model algorithm can be applied to optimize the design of the water turbine runner.

An Experimental Investigation of Overshot Waterwheel in Very Low Head Water Resources for Pico Hydro

Waterwheels are considered a low-cost and simple alternative method for rural electrification and this paper aims to investigate the performance of a non-complex geometrical design of overshot waterwheel in a pico hydro system. The waterwheel and the hydro system have been assessed at very low water heads condition at 1.5 m water and 5 L/s flow rate using a water test rig. According to the experimental results, the proposed waterwheel manages to achieve significant rotational speed, mechanical torque, and efficiency. The rotational speed has produced more than 130 rpm with mechanical torque reaching up to 1.2 Nm. Analytically, the turbine with four bottles per blade has an efficiency of 32 %. This is higher than the efficiency of three bottles per blade at 24 %. The results have also indicated that the overall performance of overshot water wheels with four bottles blade is higher than the three bottles per blade. Furthermore, certain specific values of water head and flow rate have been found out to be able to obtain the optimum efficiency. At the same time, the values of water head and water flow rate have been also found to be proportional with the value of the mechanical torque produced. Finally, the ability of the proposed system to produce a considerable output for power generation has showed that it is potentially viable to be used at the actual field.

Stability analysis of expansion and efficiency improvement of bulb tubular turbine

Many bulb tubular turbines were put into operation earlier. The construction of upper and lower cascade power stations leads to the decrease of generating head. Unit efficiency decline can not reach the design output. Large quantities of water were abandoned from the power station. Taking the expansion and efficiency improvement of water turbine generator unit in Bailongtan Hydropower Station as an example. The stability and efficiency improvement before and after expansion are compared and analyzed. The transformation not only solves the problem of high vibration of low waterhead and failure to reach the designed output, but also increases the flow and output of the unit, reduces abandoned water of the power station, improves the utilization rate of hydraulic resources, improves the stability of the unit and ensures the safe operation of the power plant. The result of unit transformation is good. It can be used as a reference for the transformation of similar tubular units.

Theoretical model and its experimental verification on nonlinear flow through a rough fracture of silty mudstone under low water head

An important method to study the seepage characteristics of rock fractures is using nonlinear flow models. However, existing nonlinear flow models are unable to describe the flow law of water-soil particles mixture through the rough fractures of soft rock because the rheological properties of the fluid are rarely considered. In this study, a novel nonlinear flow model (WST model) for water-soil particles mixture through rough fracture of silty mudstone under low water head was proposed based on local viscous pressure drops and local pressure drops. To verify the accuracy of the model, saturated seepage experiments were carried out on five silty mudstone samples with a rough fracture under low water head. The results demonstrate that compared with the MT model (a nonlinear flow model for fluid flowing though rough rock fracture at a low velocity), the WST model is preferable to fit experimental data, showing better precision in describing nonlinear flow through rough fracture of silty mudstone under low water head conditions. Furthermore, the WST model is particularly applicable when the average height of the surface of all fracture units relative to the datum plane is less than 0.62 mm and the Reynolds number is less than 620. In addition, the disordered movement of soil particles under the combined action of inertia and water head is the main reason for the nonlinear flow of water–solid particles mixture in the silty mudstone fracture.

Multi-scale oscillation characteristics and stability analysis of pumped-storage unit under primary frequency regulation condition with low water head grid-connected

This paper aims to study the multi-scale oscillation characteristics and stability of pumped storage unit(PSU) under primary frequency regulation(PFR) condition with low water head grid-connected. Firstly, a novel nonlinear mathematical model of pumped storage unit governing system(PSUGS) considering the nonlinear characteristics of diversion tunnel is established, and the nonlinear state equations under power control mode is deduced. On this basis, the bifurcation characteristics and dynamic response process of PSUGS system with coupled first-order, third-order and fifth-order synchronous generator are studied respectively, and the effects of different order synchronous generator on the nonlinear PSUGS system are compared. In addition, the transient characteristics of the nonlinear PSUGS system considering the fifth order synchronous generator under different water heads are studied. Finally, the sensitivity of the regulation system parameters of PSU under PFR with low water head is analyzed, and the effects of hydraulic, mechanical and electrical factors on the multi-scale oscillation characteristics and stability of the nonlinear PSUGS system are revealed. The results show that the stability of PSU considering the first-order synchronous generator is less than that considering the third-order and fifth-order synchronous generator. The stability of PSU considering the third-order synchronous generator is close to that considering the fifth-order synchronous generator. In the operation of PSU, the lower the water head, the smaller the stability of the system. Under PFR condition, the nonlinear PSUGS system meets the supercritical Hopf bifurcation. During PFR oscillation of the unit, the high-frequency wavelet is excited by the generator excitation system and is sensitive to the q-axis parameters of the generator. The low-frequency wavelet is mainly excited by the power grid and mapped with the water hammer effect in the dynamic process. The research results of this paper provide a theoretical basis for the stability analysis and optimal regulation of PSU under PFR condition with low water head.

Design of three-stage start-up optimal strategy based on fuzzy fractional-order proportion integration differentiation controller of pumped storage unit under low water head

When the pumped storage unit (PSU) operates in the low water heads, it is easy to enter the ‘S’ characteristic area, which leads to the chaotic phenomenon of the hydraulic transient of the PSU and makes the adjustment and control of the PSU under the no-load start-up condition extremely difficult. In this paper, a strategy of integrating three-stage guide vane opening law and fuzzy fractional-order proportion integration differentiation (PID) controller is proposed for the low water head start-up condition of PSU. Firstly, based on the mathematical model of pumped storage unit regulation system (PSURS), the mapping relationship between water head, no-load guide vane opening, the frequency switch point of the controller, and the number of rotational speed fluctuations is analyzed. Then a three-stage start-up optimal strategy based on a fuzzy fractional-order PID controller is proposed. On this basis, the multi-objective optimization method of control parameters for the three-stage start-up strategy is proposed by introducing the rotational speed overshoot and integrated time and absolute error (ITAE) index. Furthermore, to achieve efficient tuning of the high-dimensional control parameters for the multi-objective optimization method, a multi-objective grey wolf algorithm is proposed by introducing quantum space theory. Finally, numerical experiments are carried out to compare the start-up transition process under the three-stage start-up optimal strategy and conventional standard mode. The results indicate that compared with the conventional method, the proposed method has significant advantages in improving the dynamic stability and control quality of the low water head start-up of the PSU. The fluctuation times of the rotational speed of the PSU optimized and regulated by the novel method is 0 times, the regulation time is reduced by 34 s at most compared with the conventional method, and the steady-state error is only 0.003.

Design of type-2 fuzzy fractional-order proportional-integral-derivative controller and multi-objective parameter optimization under load reduction condition of the pumped storage unit

Pumped storage unit (PSU) is an effective regulation tool of the smart power grid system. The inherent “S” characteristics caused by the reversible design of the pump-turbine will make the PSU run into a state of instability, resulting in severe hydraulic fluctuation, unit speed, and frequency oscillation. PSU load reduction is an operation condition often encountered in the process of peak load regulation and frequency regulation. The operation stability of this condition is very important to the safety of the power station and power grid. Firstly, a mathematical model suitable for the numerical calculation of all working conditions transition process in the power generation direction of pumped storage unit regulating system (PSURS) is established. Further, the load reduction condition under typical water heads is selected. Through numerical calculation and analysis, it is found that when the PSU operates in the low water head-small load area and encounters load reduction to no-load, the PSURS is easy to fall into an unstable state. Therefore, an interval type-2 fuzzy fractional-order proportional-integral-derivative (PID) controller is proposed for the load reduction condition of the PSU under low water head and small load operation. And a multi-objective joint optimization strategy is proposed for tuning controller parameters. The experimental results show that the interval type-2 fuzzy fractional-order PID controller after parameters optimization has better control performance than traditional controllers. Compared with the PID control method, the double objective optimal result index is reduced by 0.025 and 47.98 respectively, the rotational speed regulation time of the PSU is reduced by 20.27 s, the maximum water hammer pressure is reduced by 9.2 m. The novel method effectively solves the instability problem of PSU under low water head load reduction conditions.

Optimization of Reaction Typed Water Turbine in Very Low Head Water Resources for Pico Hydro

The purpose of this research is to investigate the dominant parameters that influence the optimum performance of reaction typed turbine at very low water head. The concepts of conservation of mass, momentum and energy are utilised to explore performance characteristics using a graphical technique. Parametric analysis of the governing equation and experimental results were performed to show that the turbine diameter and nozzle exit area has a dynamic response to mass flow rate, angular speed, output power and efficiency. Depending on the nozzle diameter of (0.01 m, 0.006 m, and 0.008 m) and turbine pipe size with (diameter of 0.025 m and 0.015 m), six versions of prototype turbine Z-blade turbine were produced. All the turbines have been tested at 100 kPa static water pressures and below. According to a variety of experimental data for all types of turbines, the turbine diameter and nozzle exit area have a substantial impact on turbine performance, especially at high water heads. Despite differences in turbine length and nozzle exit area, more than 90 % of the pattern curves for rotational speed, water flow rate, and mechanical power were identical. Overall, the Z-blade turbine Type B outperforms, resulting in higher turbine efficiency at low head and low flow water condition.

Performance Analysis of a Low Head Water Vortex Turbine

A small hydropower plant is an environment-friendly renewable energy technology. The run-of-river type gravitational water vortex turbine can be designed to produce electricity at sites with low water heads. In this study, an experimental investigation was undertaken on this type of turbine with a water tank and a runner which is connected to a shaft. At the end of the shaft, a rope brake was attached to measure the output power, torque and overall efficiency of the vortex turbine by varying flow rates. The designed vortex turbine can achieve an overall efficiency of . The experimental results were validated with available data in the literature and theories associated with the turbine. The results also showed that the flow rate plays a vital role in generating power, torque as well as overall efficiency. The project was completed using local resources and technologies. Moreover, as water is used as the input power, this project is eco-friendly which has no adverse effect on the environment.

Investigating barotrauma in juvenile salmon passing through a very low head turbine using response surface methodology

Although hydropower is a clean source of energy, in some cases, it can jeopardize the life of some species of riverine fish. Very Low Head (VLH) water turbine is an innovative design that aims at reducing the adverse effects of such hydroelectric facilities. In this research, two methodologies are integrated to investigate barotrauma in juvenile salmons passing through this particular turbine. First, to quantify barotrauma, we implement a method known as BioPA (Biological Performance Assessment) by combining the results of some laboratory experiments on juvenile Chinook salmon moving through a simulated turbine passage with the Computational Fluid Dynamics (CFD) simulation of the flow field in this environment. In the second part, we added surrogate-based modeling as a tool, which enabled us to study the effects of two geometrical parameters on the environmental performance of the VLH turbine with low computational costs. The results indicate a significant dependency between the installation angle of the VLH turbine and the severity of the barotrauma of this particular fish. In addition, further investigations suggest that the region near the middle of blades is the safest for fish in the case of decompression.

A Machine Learning-Based Model Predictive Control Method for Pumped Storage Systems

Integrated systems required for renewable energy use are under development. These systems impose more stringent control requirements. It is quite challenging to control a pumped storage system (PSS), which is a key component of such power systems. Because of the S-characteristic area of the PSS pump turbine, traditional proportional-integral-derivative (PID) control induces considerable speed oscillation under medium and low water heads. PSSs are difficult to model because of their nonlinear characteristics. Therefore, we propose a machine learning (ML)-based model predictive control (MPC) method. The ML algorithm is based on Koopman theory and experimental data that includes PSS state variables, and is used to establish linear relationships between the variables in high-dimensional space. Subsequently, a simple, accurate mathematical PSS model is obtained. This mathematical model is used via the MPC method to obtain the predicted control quantity value quickly and accurately. The feasibility and effectiveness of this method are simulated and tested under various operating conditions. The results demonstrate that the proposed MPC method is feasible. The MPC method can reduce the speed oscillation amplitude and improve the system response speed more effectively than PID control.

A Three-Dimensional CFD Study of NACA 0018 Darrieus Hydrokinetic Turbine through Unsteady RANS Simulations

For low-head water sources, hydrokinetic turbines are potential technologies that can offer viable renewable energy options to extract energy in the rivers and water channels. In this paper, three-dimensional unsteady simulations were carried out on a straight-bladed Darrieus hydrokinetic turbine with NACA 0018 airfoil to analyse the flow physics in vortex separation at an operating tip speed ratio of 1.7 with turbine solidity of 0.224. The vortex separation or flow separation, and flow reattachment have been studied concerning the instantaneous power coefficients of the turbine at different azimuthal positions. It was observed that the steady decline in turbine power coefficient occurs from the azimuthal angle of 90° as vortex separation begins. A dip into the negative region was found 60° later. The re-entering into the positive power coefficient region is attributed to flow reattachment between 180° and 210°.

Research of Turbine Efficiency Test by Current-Meter Method in Circular Pipe

For absolute discharge and efficiency measurement of turbine with medium and low water head, the current-meter method has high precision, good reliability, and wide application range. For rectangle flow channel, it is easy to lift down a gate frame with current meters to measure the flow velocity, but for circular pipe, due to the high stress, possible deformation, and strict safety requirement, the design, installation, and implementation of the support bracket is the key to the measurement by current-meter method. In this paper, we made the research of key technology for current-meter method in circular pipe. By building a numerical model for circular pressure pipe and flow measuring bracket, we analysed the influence of meters arrangement, the force and deformation of support pole with CFD, and fluid-solid coupling method, Finally, an optimized reinforcement bracket is proposed, with combined smooth and stress calculation, the measuring bracket is verified it can withstand the flow stress and has good safety characteristics, which can provide a reference for other similar turbine efficiency tests.

Study on hydraulic transient process of K hydropower station with low head, large flow and complex long tail water system

K hydropower station is a hydraulic engineering with the main task of power generation, which is also a typical hydropower station with low head, large discharge and long tail water conveyance system. The hydraulic characteristics of these-type hydropower stations are of high water inertia, large amplitude of surge chamber water level fluctuation and poor stability of units. Therefore, due to the control requirements of the stability, the area of the horizontal section of the surge chamber is usually large, which leads to the long period of water level fluctuation of the surge chamber and the relatively long time of unit output oscillation in the transition process, and the regulating quality of the unit is often difficult to meet the control requirements due to the large inertia time constant of the water flow in the water conveyance system and the unique characteristic curve of unit. It is important to design appropriately to ensure the safe and stable operation of the hydropower station. In this paper, it is shown the process of hydraulic design of these-type stations. According to the design of K hydropower station, the simple surge chamber and restricted orifice surge chamber are compared in terms of hydraulic characteristics including the head loss of steady operation, the water level fluctuation of transition process and the stability of operation. Based on the optimized restricted orifice surge chamber, the overall calculation and analysis of the hydraulic transition process and the stability analysis of K hydropower station are carried out, it is concluded that the unit stability quality of the K power station is fine and the maximum pressure of pipe is in control, which provide strong support for the safe and stable operation of K station. The comprehensive and thorough analysis in this paper can provide reference for the design of the similar projects.

Analysis of Performance of Permanent Magnet Generator Fluks Axial 1 Phasa with Variation Load

With the potential of low water head energy and relatively small water discharge then it takes a low round generator to be applied to the potential of existing energy. The development of Permanent Magnet Generator (PMG), being an alternative considering the pole construction of the rotor is relatively simple compared to conventional generators, so it is technically required a more number of rotor poles in the effort to lower the speed The nominal dial generator. The purpose of this research is to analyze the 1-phase axial generator performance with varied resistive loads and inductive loads. This research has 4 stages of research: 1). Study literature. 2). Carried out testing tools. 3). Measurement of data retrieval. 4). Data analysis. From this research obtained results from the tools and measurements of the data retrieval of the performance of axial generator 1 phase with inductive and resistive load Vaiasi. Load mounted 15 watts, voltage 35.10, current 0.80, RPM 2550 when load 75 Waat, Voltage 11.50, current 1.54, RPM 2220. From these results can be concluded axial generator 1 phase currents also get bigger but voltage and rpm decreases.

Archimedes Screw Turbines: A Sustainable Development Solution for Green and Renewable Energy Generation—A Review of Potential and Design Procedures

Archimedes Screws Turbines (ASTs) are a new form of small hydroelectric powerplant that can be applied even in low head sites. ASTs offer a clean and renewable source of energy and are safer for wildlife and especially fish than other hydro generation options. As with other energy solutions, ASTs are not a global solution for all situations. However, in terms of sustainable development, ASTs can offer many economic, social, and environmental advantages that make them an important option for providing sustainable hydropower development. Archimedes screws can operate in low water heads (less than about 5 m) and a range of flow rates with practical efficiencies of 60% to 80% and can generate up to 355 kW of power. ASTs increase the number of suitable sites where it is possible to develop sustainable hydropower, including in undeveloped, hard to access regions and small communities. At many low head sites, ASTs may be more cost-effective, with lower installation and operating costs than alternative hydropower systems. An AST may also reduce the disturbance of natural sedimentation and erosion processes and have smaller impacts on fish and other fauna. ASTs can often be retrofit to existing unpowered dams or weirs, providing new hydropower capacity for very little marginal environmental impact. This review outlines the characteristics of ASTs, then discusses and analyzes how they could benefit the sustainability of hydropower development.