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The concept of clean and renewable energy is currently a focus developed continuously. One of the abundant sources of clean and renewable energy is water. A water turbine is a mechanism to generate electrical energy by utilizing the water flow. Pico or nano hydro turbines produce electrical energy by taking advantage of the flow of water that rotates the shaft of the electric generator. This experimental study aims to analyze the effect of differences in the number of blades on a Horizontal axis drag-type Savonius turbine mounted of water flow in a vertical pipe. The variations of blades number used in the study are 3, 4, 6, 8, 10, and 12. The potential energy of the water is kept constant with a constant head of 2 meters. Four main parameters used as a benchmark for the performance of water turbines are rotor rotation, voltage, current and electrical power generated. The results showed that the rotor rotation, voltage, current, and generated electrical power decreased as the number of blades used increased. The water turbine of 3 blades produces the best performance compared to the other one. The magnitude of the rotor rotation, voltage, current, and electrical power generated is 846 rpm, 15.28 volts, 0.61 amperes, and 9.38 Watts, respectively.

Unstable flows in the runner of water turbines, such as reverse flow, vorticity and flow direction transition, are the main factors causing increased losses and decreased efficiency, and changing the geometry structure in the downstream of the runner is an important means of mitigating these instabilities. The different flow fields downstream of runners induced by different locking nut structures are numerically calculated and verified by experimental results. The flow states are evaluated in terms of characteristic quantities such as pressure gradient, swirling flow, reverse flow, and vorticity. The results show a non-negligible effect of the locking nut, which leads to a more uniform pressure distribution, increases the descending speed of the reverse flow rate, and reduces the volume and strength of the vortex. The small locking nut significantly weakens the pressure gradient, reduces the top reverse flow zone, and decreases the vortex volume at the blade flow passage outlet and the size of the downstream disturbance vortex. The extended lock nut reduces the growth rate of the vortex generation rate and the size of the partial vortex, but increases the range of the high-pressure zone, causing the bottom reverse flow and increasing the vortex. [ABSTRACT FROM AUTHOR]

The flow in the draft tube of the water turbine is affected by the upstream flow and the inherent structure accompanied by various undesirable characteristics, affecting the efficient and stable operation of the water turbine. Changing the flow structure downstream of the runner is an important measure to reduce hydraulic loss in the draft tube and improve stability. In this study, three downstream structures of the runner, namely, the non-locking nut, small locking nut, and extended locking nut are numerically calculated and verified using experimental results. The unstable flow characteristics of the draft tube are analyzed using variations in swirling flow, backflow, pressure gradient, and vortex strip. The results show the non-negligible effect of the locking nut, which significantly reduces the rotational momentum flux at the draft tube inlet, accelerates the decay rate of the swirling flow, and suppresses the generation of axial low pressure. The small locking nut significantly reduces the pressure gradient, shortens the backflow zone, and decreases the backflow velocity. The extended locking nut reduces the backflow zone in some sections and reduces the vortex zone of the straight section but prolongs the backflow zone and increases the backflow velocity. [ABSTRACT FROM AUTHOR]

Water Turbine Unit is the core equipment of water power generation. It is the most important research object in hydroelectric power. The analysis of daily monitoring data of Water Turbines can evaluate its running state and avoid the loss caused by failure. In this paper, A hybrid neural network architecture which CNN combines Transformer is proposed to evaluate the health state of water turbines based on multivariate long time series data. It has two core components: (i) dilated convolution applies to capture low-level and local semantic information, then the output of convolutional layers is divided into subseries-level patches by time, these patches are regarded as input tokens of Transformer layers; (ii) utilizing self-attention of Transformer to extract high-level and global semantic information. Patching design naturally has benefit as follow: (i) local semantic information is retained in Transformer input tokens and high-level semantic confirm to common sense of human understanding through low-level construction; (ii) the length of Transformer input sequence is greatly shorted and attention can be more concentrated compared with point-wise form. Meanwhile, the computation and memory usage reduces at the same time. The experimental result indicates that the hybrid architecture can achieves excellent performance in time series understanding. [ABSTRACT FROM AUTHOR]

Unstable flows in the runner of water turbines, such as reverse flow, vorticity and flow direction transition, are the main factors causing increased losses and decreased efficiency, and changing the geometry structure in the downstream of the runner is an important means of mitigating these instabilities. The different flow fields downstream of runners induced by different locking nut structures are numerically calculated and verified by experimental results. The flow states are evaluated in terms of characteristic quantities such as pressure gradient, swirling flow, reverse flow, and vorticity. The results show a non-negligible effect of the locking nut, which leads to a more uniform pressure distribution, increases the descending speed of the reverse flow rate, and reduces the volume and strength of the vortex. The small locking nut significantly weakens the pressure gradient, reduces the top reverse flow zone, and decreases the vortex volume at the blade flow passage outlet and the size of the downstream disturbance vortex. The extended lock nut reduces the growth rate of the vortex generation rate and the size of the partial vortex, but increases the range of the high-pressure zone, causing the bottom reverse flow and increasing the vortex.

The flow in the draft tube of the water turbine is affected by the upstream flow and the inherent structure accompanied by various undesirable characteristics, affecting the efficient and stable operation of the water turbine. Changing the flow structure downstream of the runner is an important measure to reduce hydraulic loss in the draft tube and improve stability. In this study, three downstream structures of the runner, namely, the non-locking nut, small locking nut, and extended locking nut are numerically calculated and verified using experimental results. The unstable flow characteristics of the draft tube are analyzed using variations in swirling flow, backflow, pressure gradient, and vortex strip. The results show the non-negligible effect of the locking nut, which significantly reduces the rotational momentum flux at the draft tube inlet, accelerates the decay rate of the swirling flow, and suppresses the generation of axial low pressure. The small locking nut significantly reduces the pressure gradient, shortens the backflow zone, and decreases the backflow velocity. The extended locking nut reduces the backflow zone in some sections and reduces the vortex zone of the straight section but prolongs the backflow zone and increases the backflow velocity.

One way to meet the needs of fish seeds in the general public is to cultivate fish species. UPT BBI (Balai Benih Ikan) Tlogowaru, is one of the fish seed cultivation sites located on Tajinan Tlogowaru, Kedungkandang sub-district, Malang City. Fish seeds include koi fish seeds. In the pool using water from the river. To maintain the water of the koi fish hatchery, the condition of color turbidity is monitored as the level of turbidity of the water visible from above the waters of the koi fish hatchery, and a water flow sensor is processed by esp32. The water flows through the gravity pipe which will turn the turbine. With the rotation, the generator will produce power which is used to activate the telemonitoring device. The water then enters the filtration and will be channeled to the koi fish hatchery. The results of this study have an average pH value of 6.8 - 7.2 and a TDS of 257-282 ppm after water filtration with the turbine speed value being influenced by water flow and turbine rotation speed and the average power consumption generated for system performance of 8.265 w/h using a MiFi network with QoS parameters measured are delay and packet loss in the low category. And the use of the website makes it easier for users to monitor fish seed ponds

Hydroelectricity power source as one of the reliable and renewable energy. In India around 12% of electricity production contributed by hydropower. Due to rapid increase in urbanization, global warming and oil crisis increases. For this need advanced renewable energy extraction technique to meet the global demand. Nowadays at transportation sector electrical vehicles enter to market more and more. To meet the power demand open canals water turbine provides a major contribution locally. Open canals water turbine not require high civil structural work, it can be installed with small modification of existing infrastructure. This turbine installed in open canals and safer from any flood or storm damage condition. Thus, research aims at designing a hydrokinetic turbine applicable to zero head and low velocity flow water bodies such as canals. Open canals water turbine CFD simulation has been performed to predict the flow pattern of water. Additionally power was generated from the optimized design model in lab conditions (Ogee weir channel) wherein the flow velocity was less ranging from 0.02-0.05m/s and the turbine rotated within a range of 14-16 rpm. With further consideration in design and implementation gear box higher power can be achieved when implemented on a large canal’s or channels. [ABSTRACT FROM AUTHOR]

Supply-demand-based optimization (SDO) is a swarm-based optimizer. However, it suffers from several drawbacks, such as lack of solution diversity and low convergence accuracy and search efficiency. To overcome them, an effective supply-demand-based optimization (ESDO) is proposed in this study. First, an enhanced fitness-distance balance (EFDB) and the Levy flight are introduced into the original version to avoid premature convergence and improve solution diversity; second, a mutation mechanism is integrated into the algorithm to improve search efficiency; finally, an adaptive local search strategy (ALS) is incorporated into the algorithm to enhance the convergence accuracy. The effect of the proposed method is verified based on the comparison of ESDO with several well-regarded algorithms using 23 benchmark functions. In addition, the ESDO algorithm is applied to tune the parameters of the fractional-order proportional integral derivative (FOPID) controller of the water turbine governor system. The comparative results reveal that ESDO is competitive and superior for solving real-world problems. [ABSTRACT FROM AUTHOR]

Hydrokinetic power contributes to energy security by a sustainable and predictable power source, and its decentralized nature fosters economic development in local communities. Unlike large-scale hydropower projects, hydrokinetic power has lower environmental impacts, promoting technological innovation and supporting the transition to cleaner energy systems. Furthermore, it pledges to guarantee electricity in isolated regions where traditional power systems are not suited, enhancing energy accessibility. This study presents a method that combines the Soil and Water Assessment Tool (SWAT) with the Hydrologic Engineering Center's River Analysis System (HEC-RAS) to forecast the hydrokinetic power capacity of a basin. The research site chosen is the Çoruh River, a transboundary river basin with unavailable publicly accessible flow data. This method approximates the flow data utilizing the SWAT model, which relies on hydrological factors. Following the prediction of the flow data in the basin, the HECRAS model simulates the river's hydraulic conditions to estimate hydrokinetic energy potential. This integrated methodology provides a framework for optimizing hydrokinetic resources in diverse settings, guiding resource management, and sustainable energy planning. This study calculated theoretical hydrokinetic energy potential by considering flow velocity values. Results of the study indicated that the average flow velocity in the Çoruh basin reaches its maximum value of 0.99 m/s in spring and its minimum value of 0.69 m/s in summer, respectively. Based on the seasonal analysis of the integrated approach, the highest maximum theoretical hydrokinetic power density in the basin reaches 26 kW/m2 during the spring and in sub-basins 5, 7, and 8. The average theoretical hydrokinetic power density is calculated as 0.28 kW/m2. Finally, the study presents several potential locations along the Çoruh River through GIS mapping, where small-scale hydrokinetic turbines could be installed as a viable option. • This study investigates the potential and future possibilities of hydrokinetic energy in a transboundary river basin, Çoruh Basin. • When flow data is publicly unavailable in transboundary rivers, hydrokinetic energy potential can be assessed using hydrological and hydraulic models. • Through an integrated approach utilizing both SWAT and HEC-RAS models, hydrokinetic power potential is estimated, and ideal locations of hydrokinetic turbines are determined. • The maximum and average theoretical hydrokinetic power density calculated were 25.33 kW/m2 and 0.28 kW/m2 respectively. • The hydrokinetic potential of the Çoruh river has been estimated using the SWAT model, predicting daily flow values with an R2 value of 75%. [ABSTRACT FROM AUTHOR]

The present work aims to obtain a ranking of hydro generating units using the analytic hierarchy process (AHP) method, based on the maintenance indicators of the Santo Antônio Hydroelectric Plant (SAHP). The purpose of the generated classification is to provide subsidies to assist maintenance planning, determining the most critical turbines for performing preventive maintenance, in order to increase the availability of equipment, in addition to reducing the probabilities of forced shutdowns for corrective maintenance, impacting factors the plant's availability factor. Thus, the main contribution of this work is the application of AHP to classify the SAHP generating units, using parameters and actual historical data from the plant and hydraulic turbines. [ABSTRACT FROM AUTHOR]

The project “key enabling technologies for clean production” (KET4CP), which is supported by the European Commission, has the aim to connect small and medium-sized enterprises (SME) and Technology Centres (TC) for cleaner, greener and more efficient production. Within this context, SMEs and TCs across Europe work together to establish an open-innovation network and to raise awareness in productivity and environmental performance. This article presents how an open European network of TCs opens its innovation process to support SMEs to become cleaner, greener and more efficient. Furthermore, this article shows how the TCs and SMEs become a part of the open-eco-innovation platform in clean production and how successful the open-eco-innovation process of different European countries is. We revealed that a pan-European open innovation process for eco-innovations with TCs for key enabling technologies (KET TCs) and Enterprise Europe Network partners (EEN) is a successful approach for SMEs that want to produce and develop cleaner products. An application example is mentioned, in which TCs from different European countries have contributed to developing a product of a SME for energy harvesting. The SME, together with the TCs, developed a generator that is installed in city-level water supply pipes and so, it is outstanding in its application. This innovative application is also described in this article.

In the paper the theoretical basis of pumped-storage power plant operation is presented. Working conditions of hydraulic machines in these kinds of objects are described and examples are given. The Czech research results as well as German theoretical analyses on the topic of water energy storage in underground mines are characterized. The conditions for building pumped-storage power plant in Polish underground coal mines, including liquidated ones, are determined. Analysis of parallel operation of multistage centrifugal pumps, dedicated to the mine drainage system, manufactured and operated commonly in Poland is presented. The main dimensions calculations of two multistage centrifugal pumps (power of 10 MW and 25 MW), dedicated for selected parameters, are presented. [ABSTRACT FROM AUTHOR]

The present paper describes the performance of a micro undershot water wheel for the power generation in a snow drainageway with the Froude number of 2 to 3. In order to optimize the installation conditions of the undershot water wheel and its arc blade, the effects of blade inlet angle β and the submerged blade height hc on the performance of the undershot micro water wheel has been investigated by field test at Shiramine district in Ishikawa Prefecture. Furthermore, two-dimensional computational fluid dynamics (CFD) has been performed using ANSYS Fluent to be shown clearly the flow of inside and outside of the undershot water wheel and its power. The water wheel has a diameter of D = 600 mm and a width of W = 410 mm. In the snow drainageway, the Froude number is Fr = 2.15 to 2.42. The CFD result of the change of the maximum power coefficient CPmax with the blade inlet angle of β agrees with the experimental one qualitatively. In the case of the submerged blade height hc/D = 0.10, the blade inlet angle β has little influence on the power coefficient CP. In the case of hc/D = 0.20 and 0.29, the peak value of the maximum power coefficient is CPmax = 0.37 and 0.27 at β = 18° and 24°, respectively. The relation between the flow in the water wheel and the generation of torque has been clarified by CFD. The negative torque generates at the rotation angle of water wheel θ = 0 ~ 40° because the separated flow from the tip of blade collides against the back of the blade. The positive torque generates at θ = 45 ~ 110° to apply the drag force by the main flow. The positive torque also generates by the water flow passing through the blades for θ = 135 ~ 210°.

Purpose: In Southeast Asia, the renewable energy produced from hydropower systems has significant potential. Therefore, adequate development is needed to prevent future energy-related crises. This study, therefore, aims to determine the variations effects in geometry and the geometrical factors on turbine performance. Design/methodology/approach: The developed aspects are selected to determine the blade shape, its number and multistage requirements. The study was conducted in 3D simulation, with Ansys software used to calculate a series of computational fluid dynamic problems. The aspect ratio applied in this study utilized the ratio of the overall diameter of the rotor height (D / H), which is 1. Findings: The results showed that the highest Cp-max value, number of blades and stages were 0.2, two and three, respectively. Furthermore, these attributes combined to improve the performance of hydroturbines. Research limitations/implications: The research was fully conducted using numerical simulation, which requires sustainable research in the form of laboratory experiments. Also, pioneer experiments were conducted using benchmarking to ensure the results obtained are reliable. Practical implications: Hydropower is one of the best renewable energy sources in Indonesia with a large potential in the archipelago and tropical countries due to rivers and various water sources. The current generated is a useful reference for Savonius design. Originality/value: The originality of this study is to examine the three aspects of the geometry of the rotor, such as the number and shape of blades, as well as the stages in the same boundary conditions. Therefore, the comparison of the effects of changes in geometry on turbine performance is more acceptable and complete compared to the pioneer works, which focused on a parameter. This research combines several aspects to determine the effect of rivers and various water sources on the hydroturbine. [ABSTRACT FROM AUTHOR]

Furthermore, the component HT ht is calculated from the experimentally measured value of the radius of the turbine, measured value of the radius of nozzle, and the midpoint of the nozzle to the turbine wall. This component HT ht is also very influential to allow the ZBT to rotate without interference by the jet of water coming from the other nozzle. Here, the component HT ht is determined from the measured value of mass flow rate and measured value of exit nozzle area. [Extracted from the article]

For decades, Darrieus turbines have shown their advantage over other turbines for providing hydropower. Most studies tend to be conducted with the turbine in its vertical axis configuration, while few have examined the horizontal axis configuration. In this paper, we undertake a computational fluid dynamics (CFD) analysis that investigates blade profile alternatives to improve the efficiency of a horizontal axis Darrieus turbine under more natural flow conditions. An inlet boundary layer profile and a confined domain are imposed to represent river conditions. Four blade profiles are tested under various tip-speed ratios using a three-bladed turbine. The developed model is based on an unsteady k-ω shear stress transport (SST) turbulence closure associated with a very-fine-grid mesh. The model methods are first validated against open-channel experimental results published in the literature and show less than 13% discrepancy. The S1046 blade profile is shown to improve the power coefficient Cp by 14% compared to the NACA0018 blade profile. The S809 blade profile exhibits the lowest performance in the dynamic stall and transition regions. For high tip-speed ratios, the FXLV152 profile produces the highest local efficiency power coefficient. The influence of the blade number is also quantified. The four- and two-bladed S1046 configurations achieve the highest power coefficients in the low and high tip-speed ratio regions, respectively. [ABSTRACT FROM AUTHOR]

Undershot cross-flow water turbines are characterized by their being easily applicable to open channels with various widths and depths by changing their blade width and/or the outer diameter of the runner. On the other hand, as this water turbine operates in a free-surface flow field, it is expected that when the flow rate changes, the flow field around the runner including the water depth changes dramatically, and that the turbine performance also changes. Thus, the objective of this study is to elucidate the effect of flow rate on the performance and flow field of an undershot cross-flow water turbine. By changing the flow rate, we conduct experiments and free surface flow analysis on the water turbine, as well as torque component analysis. The result showed that, among the torques in the respective flow regions, that torque resulting from the second stage cross-flow was dominant. Furthermore, it was found that among the respective dynamic components of the torque, the most dominant component was the gravitational component for low flow rates and the angular momentum component for medium-to-high flow rates. We expect these results to contribute to the establishment of higher performance design guidelines, such as optimum shapes for the flow rates. • The undershot cross-flow water turbine is applicable to open channels of various widths and depths. • The effect of flow rate on the performance of the present water turbine were elucidated. • The flow field was elucidated at different flow rates. • The breakdown of the torque into its flow rons and dynamic components were elucidated. [ABSTRACT FROM AUTHOR]

The paper presents an approach to calculate the static pressure rise upstream of a valve in a pressure penstock of a hydropower plant (HPP), i.e. a valve upstream of a turbine, during an emergency closure of the flow. The calculated value of the pressure rise is applied for the design of the appropriate time of the valve emergency closure in the HPP penstock and for the sizing of the various parts of the HPP (structural and mechanical). The basic theoretical background of the problem, calculation relations, the range of validity of the used calculation relations are explained and then the procedure applied to the solution of a specific task from practice is explained.

Darrieus horizontal axis hydrokinetic turbines (DHAHT) have shown their ability to provide hydro-power in shallow rivers. Investigation of DHAHT performance and interactions with the free surface are of great importance and are investigated numerically in the present work using a multiphase CFD solver. The free surface is modeled using the volume of fluid (VOF) method associated with an unsteady k − ω SST turbulence closure. Fully developed boundary layer conditions are imposed at the inlet. Two submergence configurations are considered by varying the water level: partially submerged (configuration 1) and fully submerged (configuration 2). The flow solver has been carefully validated against experimental data available in the literature for a three-blade vertical axis Darrieus wind turbine and a dam break experiment. Total immersion of the DHAHT leads to an improvement in the power coefficient C P by 36.8 % compared to configuration 1. For high tip-speed ratios, the Froude number downstream the DHAHT is observed to increase. The momentum extracted by the DHAHT from the flow is also quantified. The submerged DHAHT extracts the most momentum at high tip-speed ratios. The novelty of this study is to show how DHAHT performance is influenced (diminished) when the dynamics of the free surface is included in the numerical model. • Free surface modeling decreases the power coefficient by 42.4% compared with single-phase modeling. • Partially submerged turbine produces 63.2% of power compared with fully submerged. • Deformation of the free surface changes near blade vortex characteristics. • Momentum loss increases when the turbine is fully submerged. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of fatigue on the cavitation erosion was examined for a martensitic stainless steel used in the manufacture of the blades for the bulb turbines of the “Iron Gates II” Power Plant turbines. For the cavitation tests, two kinds of specimens were manufactured: from the original material (which was not subjected to fatigue) and samples of materials that were subjected to fatigue cycles with different amplitudes (from 170 to 255 MPa). It was observed that fatigue increases the tendency of cavitation erosion and thus, seems like a cumulative damage. The analysis of the cavitation erosion was done considering simultaneously the mass loss of the time dependence, the surface roughness and the modifications to the microstructure of the specimens. For the material previously subjected to fatigue cycles, the final mass loss (after 150 minutes of cavitation exposure) increases approximately by 30% and the depth of penetration by 25%. In the microstructural analyses, numerous cracks at grain boundaries were observed. Finally, a mathematical model for the dependence of mass losses with the applied stress was developed.

The effect of fatigue on the cavitation erosion was examined for a martensitic stainless steel used in the manufacture of the blades for the bulb turbines of the "Iron Gates II" Power Plant turbines. For the cavitation tests, two kinds of specimens were manufactured: from the original material (which was not subjected to fatigue) and samples of materials that were subjected to fatigue cycles with different amplitudes (from 170 to 255 MPa). It was observed that fatigue increases the tendency of cavitation erosion and thus, seems like a cumulative damage. The analysis of the cavitation erosion was done considering simultaneously the mass loss of the time dependence, the surface roughness and the modifications to the microstructure of the specimens. For the material previously subjected to fatigue cycles, the final mass loss (after 150 minutes of cavitation exposure) increases approximately by 30% and the depth of penetration by 25%. In the microstructural analyses, numerous cracks at grain boundaries were observed. Finally, a mathematical model for the dependence of mass losses with the applied stress was developed. [ABSTRACT FROM AUTHOR]

Copyright of Energy Policy Journal / Polityka Energetyczna is the property of Mineral & Energy Economy Research Institute of the Polish Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The supercritical water hydrolysis (SCWH) of biomass (P = 250 bara & T = 400 °C) allows directly obtaining sugars, which are high value products in the chemical industry, in reaction times lower than 0.2 s. The process is characterized by the high selectivity values which can be obtained controlling the reaction time. Reaction kinetics show that glucose degradation is only retarded at temperatures below 250 °C. Therefore, in the SCWH process, degradation control is achieved expanding the hydrolysis stream in a valve which instantaneously cools down the products. Although the selectivity values obtained are greater than 96%, the pressure is wasted on the valve expansion decreasing the global energetic efficiency of the process. In this paper a desuperheater designed in CFD which mixes the hydrolysis product with pressurized cooling water is presented. The temperature of the hydrolysis stream decreases below 250 °C in cooling times lower than 20 ms maintaining the selectivity value over 93%. Furthermore, the pressure remains at 250 bara increasing the global energetic efficiency of the process. [ABSTRACT FROM AUTHOR]

This study deals with the three-dimensional unsteady numerical simulation of the flow around a cross-flow vertical-axis water turbine (CFWT) of the Darrieus type. The influence of turbine design on its hydrodynamic characteristics and performance is investigated by means of a time-accurate Reynolds Averaged Navier Stokes (RANS) commercial solver. The flow unsteadiness is described using a transient rotor-stator model in connection with a sliding interface. A classical Darrieus straight blade turbine, based on the NACA0025 airfoil, has been modified adding winglets (symmetric and asymmetric designs) to the blades' tips with the objective of reducing the strength of the detached trailing vortices. The turbulent features of the flow have been modelled by using different turbulence models (k-ε Renormalization Group, standard Shear Stress Transport, transition Shear Stress Transport and Reynolds Stress Model). As a result, the predicted hydrodynamic performance of the turbine including winglets increases, independently of the employed turbulence model, being the improvement higher when a symmetric winglet design is considered. Moreover, visualization of skin friction lines pattern and their connection with vorticity isosurfaces, illustrating the flow detachment in the three blade configurations, has been carried out. Finally, a short discussion about the intermittency behavior along a turbine revolution is presented. [ABSTRACT FROM AUTHOR]

Present day, the environmental issues and the insufficiency of energy supply are of major concerns around the world. In view of this, numerous utilities have interchanged their production sources and path ways to green and renewable energy. The hydropower (HP) is the world's largest and the most efficient sustainable way to produce electricity or power. Nowadays, HP is employed for converting 90% of the energy of moving water into electricity/power. This can be comparable to the fossil fuels (FFs) based power plants, which are maximum only 60% efficient. The high expenditure and adverse environmental concerns that associated with the use of large HP plants have helped to focus the attention on small or Pico-scale HP plants, which reduce these affects considerably. Pico hydropower (PHP) offers an efficient, reliable and cost effective of alternative power sources. In addition, the demand for PHP in the market shows that PHP is the best and low-priced choice for rural or remote area electrification in developing nations. Nevertheless, the PHP technology is still considered as a brand-new in Malaysia. In this paper, the basic theories or concept of PHP were described for better understanding and recognition on this type of electricity or power production system. Furthermore, present status and projected future of PHP in Malaysia, inclusive of current installed capacity and potential of PHP energy resources are discussed. Besides that, the paper presents the barriers that hinder the proliferation of PHP in the Malaysia, the great challenges and outlooks for future developments of the PHP in Malaysia. By and large, the objective is to provide essential strategic implications for Malaysia and other Southeast Asian countries. [ABSTRACT FROM AUTHOR]

Recently, small hydroelectric generators have gained attention as a further development in water turbine technology for ultra low head drops in open channels. The authors have evaluated the application of cross-flow water turbines in open channels as an undershot type after removing the casings and guide vanes to substantially simplify these water turbines. However, because undershot cross-flow water turbines are designed on the basis of cross-flow water turbine runners used in typical pipelines, it remains unclear whether the number of blades has an effect on the performance or flow fields. Thus, in this research, experiments and numerical analyses are employed to study the performance and flow fields of undershot cross-flow water turbines with varying number of blades. The findings show that the turbine output and torque are lower, the fluctuation is significantly higher, and the turbine efficiency is higher for runners with 8 blades as opposed to those with 24 blades. [ABSTRACT FROM AUTHOR]

Energy is a direct restriction to the working life of an underwater mooring platform (UMP). In this paper, a vertical axis water turbine (VAWT) is designed to supply energy for UMPs. The VAWT has several controlled blades, which can be opened or closed by inside plunger pumps. Two-dimensional transient numerical studies are presented to determine the operating performance and power output of the turbine under low ocean current velocity. A standard k-ε turbulence model is used to perform the transient simulations. The influence of structural parameters, including foil section profile, foil chord length and rotor diameter, on the turbine performance are investigated over a range of tip-speed-ratios (TSRs). It was found that turbine with three unit length NACA0015 foils generated a maximum averaged coefficient of power, 0.1, at TSR = 2.