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Clean Energy Using Hydroelectric Generation from Rivers
Abstract
In today’s world, many countries, especially developing countries, are facing energy crisis, an increase in industrialization for development programs being the apparent reason. Fossil fuels being the most prominent source for the energy production are having an adverse effect on our environment. Also, with the rate, we are exploiting the energy resources; fossils fuels may be a principal source of energy that may see its end in the near future. If we continue to meet this demand using conventional methods like thermal power plants, environmental pollution is the most prominent aspect that we will have to continue to compromise. While pollution and climate change are the biggest challenges in the modern era, switching our attention to renewable energy sources to meet our energy demands can be the best feasible solution. Out of different renewable energy sources available, hydropower is the most readily available and clean sources of renewable energy worldwide. It can be considered as the leading source of renewable energy across the world. In this chapter, an attempt has been made to study the different ways to harness hydropower such as using static head, kinetic head, or any other disruptive technology. Environmental aspect of hydropower has also been studied. A review of different technologies such as hydrokinetic, vortex flow turbine, and water wheels have been carried out along with conventional hydropower. Thus, our effort has emphasized hydropower’s overall scenario as the most reliable renewable energy source with more emphasis on small hydropower. This book chapter aims to discuss the hydropower production scenario and its all-around aspects and efforts, which are made to develop it as the most significant factor for the sustainable future.KeywordsClean energyHydroelectric generationEnergyRiversHydrokineticHead
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Influenced by both marine and river flows, estuaries can present a high potential for hydrokinetic energy exploitation. In this study, the hydrokinetic energy production in the Douro estuary was evaluated through hydrodynamic numerical modelling. The model analysed the tide and river flow, reproduced the combined effects of these two factors on the main current velocity patterns, and identified the estuarine locations with the highest potential for energy exploitation. Given the river’s high variability caused by the precipitation patterns in the hydrographic basin area and the river’s torrential regime, several discharge scenarios were explored, combining spring and neap tides, and high and low river flows. The results revealed that the region with the highest potential is located in the upper part of the estuary, where the highest-velocity currents were achieved for mid-ebb tide conditions and strong river flows. It was also found that tides reinforce the hydrokinetic energy production during ebb tide, although they are not strong enough to produce high values of hydrokinetic energy, being the river flow the main forcing. This work demonstrates the relevance of choosing parametrized magnitudes that are not dependent on a specific equipment, as well as the importance of a proper characterization of the estuarine hydrodynamic patterns needed to optimize the hydrokinetic energy exploitation.
The paper describes the procedure for assessment of the fatigue life of steel penstocks in hydropower plants based on the theory of crack propagation. The authors pay particular attention to several issues that have a substantial impact on the fatigue strength evaluation of the analyzed structures, such as stresses distribution in the material of penstock shells (walls), variability of their amplitude and frequency, and forecast of future operation of the considered hydropower plants. The proposed procedure in combination with other relatively simple methods e.g. for determining the stress concentration factor (SCF) in the penstock shells with angular distortions basing on analytical model, gives the possibility of its easy use in engineering practice for comprehensive estimation of the fatigue life characteristic of such structures. The authors, basing on tests carried out on real objects, used the developed procedure for assessment of the fatigue life to determine the impact of the uncommon method of damping the water-hammer accompanying the transient states of the hydropower units on increasing the fatigue strength of the steel penstock structures. Results obtained may contribute to the extension of good engineering practices in the field of operation methods of hydroelectric power plants equipped with steel penstocks and procedures for the safe maintenance of this type of structures.
Small run-of-river hydropower may significantly contribute towards meeting global renewable energy targets. However, exploitation of river flows for energy production triggers environmental impacts and conflicts among stakeholders, thereby requiring optimal water resources allocation strategies. The variety of interests at stake demands instruments to quantitatively assess manifold effects of water management choices. In this work, analytic tools to guide design of run-of-river power plants when incommensurable objectives must be jointly maximized are presented. The approach is grounded on the concept of Paretian efficiency and applied to a hypothetical case study in Scotland, where energy production could compete with regionally relevant ecosystem services. We found that a multi-objective design complying with predefined environmental regulation entails significant economic losses without safeguarding ecological functions. Conversely, if the environmental flow is regarded as a decision variable subject to minimum lawful values, economically appealing and ecologically effective plant configurations emerge. Our findings suggest the existence of broadly valid alternative strategies for designing small run-of-river hydropower while preserving ecological functions, associated to small or large plant capacities. Local hydrologic conditions and target ecosystem services determine the most effective strategy for specific case studies. The analysis indicates that larger power plants are sometimes the most effective way to preserve ecosystems services through economically viable projects. Therefore, renewable energy policy should avoid incentive schemes that penalize a priori larger installations. The approach offers an objective basis to identify effective hydropower design, management and policies when additional ecosystems services are considered, thus supporting a sustainable intensification of run-of-river energy production.
This study covered the design, implementation and performance evaluation of a crossflow turbine at various nozzle positions. The chosen blade material was analyzed using ANSYS for stress and deformation degree under the impact of hydraulic jets to ascertain its suitability while in operation. The shaft was analyzed under static and dynamic conditions using ANSYS in order to ensure a non-plastic deformation of the shaft at both conditions. The outcome of this analysis was employed in the harmonic response analysis of the runner shaft. Convergent tests were done for both the blade and runner shaft analysis. An experiment was designed for the evaluation of the crossflow turbine performance using optimal (custom) design tool of response surface methodology and 69 simulations/runs were obtained. The factors considered in the experimental design are: nozzle distance from the shaft, nozzle height and attack angle. The crossflow turbine was constructed using computed design values for all the machine's parts. The runner blades were positioned specifically at 28° outer blade angle and 90° inner blade angle. The turbine was tested under a water head and flow rate of 6.4m and 0.0042
m
3
/
s
respectively. The shaft power and efficiency were evaluated using their respective formula. The responses were optimized in order to get the optimum position of the nozzle that would give the best performance of the responses using the two factor interaction (2F1) mathematical models in coded factors, developed for each of the response. The results obtained, proved that low carbon steel material was suitable for the turbine blading and the shaft is safe at both static and dynamic conditions since the induced stresses and deformations never exceeded the permissible range. Also, each of these considered nozzle positions had a significant effect on the responses with the nozzle height and attack angle having a combined effect on the performance of the turbine. The best turbine performance was obtained at lower angle of attack, nozzle distance very close to the runner shaft and at a nozzle height that will actualize greater energy impartation to the upper and lower blade profiles. The developed mathematical models for each response has higher correlation value, suggesting that the models are suitable for predicting the responses at the considered factor levels. An optimal nozzle distance, height and attack angle of 102mm, 413mm and
5
°
respectively, were obtained. At this nozzle position, the alternator gave an output of 35watts and 6V. When two voltage transformers were employed, it gave 200Volts AC. The turbine can be commercialized on large scale for greater output power using the determined optimal nozzle positions.
A large share of future European hydropower projects will be run-of-the-river schemes. To understand the potential for RoR hydropower development and modernization of the technology as an opportunity for sustainable decentralization, we use the Q-methodology to compare public values about RoR hydropower in German, Portuguese and Swedish case studies. Four perspectives on the importance of RoR hydropower emerged from our analysis: (i) maintain regional control, (ii) fight climate change, (iii) promote citizen well-being and (iv) protect natural ecosystems. Strong preferences for regional control imply RoR should be managed as distributed generation rather than viewed as part of a centralized, national system like traditional large-scale reservoir hydropower. Based on the importance of citizen well-being and ecological measures, operators could adopt strategies such as river widening and the reconstruction of secondary channels, which help control floods, create recreational opportunities as well as enhance ecological habilitation and biodiversity. Additionally, policymakers could support rigorous monitoring programs to assess the ecological impact of RoR.
Despite huge Investment potential for Small hydro power sector (SHP), enthusiasm of investors is less to proceed further due to uncertainty associated with project cost. This paper creates tradeoff between insurance companies and investors. The risk class has achieved using risk index which derived from investment risks analysis. The methodology opted for risk index assessment using applied fuzzy logic approach. Finally for premium suggestion across 36 SHP Projects are analyzed and variable premium range is suggested. The paper provides support to investors for investment decision; insurance companies for variable insurance premiums policy and policymakers via identifying sensitive pain points.
The short-term hydro scheduling (STHS) problem aims at determining the optimal power generation schedules for either a single hydropower plant or an integrated system of cascaded watercourses during a time horizon from a single day to one week. Traditionally, an aggregated plant concept is usually adopted in the formulation of the STHS problem. The hydro-turbine generator units in a plant are aggregated as one equivalent unit. Nowadays, more and more hydro producers participate in both energy and capacity markets. It highlights the need for the precise calculation for energy conversion and available capacity of each unit. Formulating the STHS problem on individual units can accurately capture the physical and the operational characteristics of the unit. In this overview, a detailed classification of mathematical programming approaches to model and solve the unit-based STHS problem is presented. The various modeling techniques proposed in the publications since 2000 are categorized by their objectives and constraints. This provides a comprehensive comparison and discussion for each specific issue in the formulation of STHS. We anticipate this overview to be a starting point for finding more computationally solvable and effective methods to handle the challenges in the unit-based STHS problem.
Available: https://doi.org/10.1016/j.epsr.2019.106027
The paper reviews recent research and development activities in the field of hydropower technology. It covers emerging and advanced technologies to mitigate flow instabilities (active and passive approach) as well as emerging magneto-rheological control techniques. Recent research findings on flow instabilities are also presented , especially concerning fluid-structure interaction and transient operating conditions. As a great number of the existing large-scale hydroelectric facilities were constructed decades ago using technologies that are now considered obsolete, technologies to achieve the digitalisation of hydropower are also analysed. Advances in the electro-mechanical components and generator design are presented; their potential role to adapt hydropower to the current operating conditions is also highlighted. The text explores current efforts to advance hydropower operation, mainly in terms of European projects. It provides a detailed overview of the recent efforts to increase the operational range of hydraulic turbines in order to reach exceptional levels of flexibility, a topic of several recent research projects. Variable speed hydropower generation and its application in pumped storage power plants are presented in detail. Moreover, revolutionary concepts for hydroelectric energy storage are also presented with the analysis focusing on underwater hydro storage and hydropower's hybridisation with fast energy storage systems. Efforts to minimise hydropower's environmental footprint are also presented via the utilisation of small-scale and fish-friendly installations.
Vertical-axis water turbines (VAWT), the target of the present study, provide a higher area-based power density when used in arrays, and are a promising alternative to horizontal-axis hydro-kinetic turbines (HAWT). Nevertheless, they operate under highly dynamic conditions near or even beyond dynamic stall at their best-efficiency-point. The abrupt loss of lift and strong increase of drag associated with hydrofoil stall can produce cyclic loads and possible damage of turbomachines due to material fatigue.
The effect of flexible structures in a highly dynamic flow regime including separation and stall is here studied systematically in an experimental setup which permits observations of all regimes ranging from quasi-static state up to the occurrence of deep dynamic stall and beyond. The process is studied using a surrogate model consisting of an oscillating NACA0018 hydrofoil in a closed water channel, following a motion law comparable to the real angle of incidence of a Darrieus turbine blade along its rotation. The investigated parameters are the oscillation frequency and tip speed ratio, for one rigid as well as for three flexible hydrofoils of different stiffnesses. The coupling process is therefore investigated for multiple machine designs and working points. Lift and drag measurements have been carried out in a systematic manner.
Results show that at tip speed ratios for which highly dynamic flow regimes occur, flexible blades provide not only higher thrust, but also reduced normal forces and reduced peak-to-peak cyclic normal force variations. This reduction of stress loads would translate into significantly increased turbine lifetime. This supports the need for further investigations in order to identify optimal blade flexibility and check further turbine designs.
Renewable energies can play an important role to provide electricity to
rural communities .This work study the design optimization of a hybrid
hydro-wind , micro-power system in a rural area . Six case studies, including
the impact of hydro head, flow rate ,efficiency, and head loss for micro
hydropower with wind turbine hub height were implemented based on
HOMER software. The simulation results show the importance of using
HOMER to assist system designers for assigning the optimum design of
hybrid system components.
Nowadays, due to the need for clean energy and sustainable electricity production, hydropower plays a central role in satisfying the energy demand. Particularly, use of low head micro hydropower plants is spreading worldwide, due to their low payback periods and good environmental sustainability. Gravity water wheels are micro hydropower converters typically used in sites with heads less than 6 m and discharges of a few cubic meters per second. Although water wheels were scientifically investigated as far back as the eighteenth century, they were largely ignored throughout the twentieth century, and only in the last two decades has there been a renewed interest in their use among the scientific community. In this paper a review on gravity water wheels is presented, distinguishing between undershot, breastshot and overshot water wheels. Water wheels technology is discussed focusing on geometric and hydraulic design; data and engineering equations found in historic books of the nineteenth century are also presented. Water wheels' performance is described examining experimental results, and modern theoretical models for efficiency estimation are presented. Finally, results achieved through experiments and numerical simulations were discussed with the aim of optimizing the performance of gravity water wheels. The results showed that maximum efficiency of overshot and undershot water wheels was around 85%, while that of breastshot water wheels ranged from 75% to 80%, depending on inflow configuration. Maximum efficiency of modern water wheels can be maintained at such high values over a wider range of flow rates and hydraulic conditions with respect to older installations. Hence well designed water wheels can be considered as efficient and cost-effective micro hydropower converters.
Water wheels were the earliest hydraulic machines used in antiquity to convert water energy into mechanical one. Due to their simple installation, low maintenance costs, and thanks to the possibility to use local manpower and material for their construction, nowadays water wheels are again used as energy supply, especially in remote localities and emerging countries. In particular, stream water wheels are installed in flowing water where there are not head differences. The performance depends on the blockage ratio, so that they can be subdivided into three main categories: stream wheels in shallow subcritical flow, shallow supercritical flow and deep flow.
In this paper, experimental, theoretical and numerical data on stream water wheels were systematically collected from literature and analyzed. Guidelines for their design were discussed focusing especially on wheel dimensions, supporting structures, blades and speed. More light on their hydraulic behavior was shed, adopting the previous classification for a better explanation and understanding. Results showed that in shallow water an head difference can be generated by the wheel, increasing the power output. In deep flow, accurate hydrodynamic floating/supporting structures allow the hydrostatic force of water to be exploited in addition to the kinetic energy of the flow. As a consequence, power output can improve from 0.5 to more than 10 kW per meter width, so that stream wheels can represent an attractive energy supply in zero head sites.
A small-scale horizontal axis hydrokinetic turbine is designed, manufactured and studied both experimentally and numerically in this study. The turbine is expected to work in most of China's sea areas where the ocean current velocity is low and to supply electricity for remote islands. To improve the efficiency of the turbine at low flow velocities, a magnetic coupling is used for the non-contacting transmission of the rotor torque. A prototype is manufactured and tested in a towing tank. The experimental results show that the turbine is characterized by a cut-in velocity of 0.25 m/s and a maximum power coefficient of 0.33, proving the feasibility of using magnetic couplings to reduce the resistive torque in the transmission parts. Three dimensional Computational Fluid Dynamics (CFD) simulations, which are based on the Reynolds Averaged Navier–Stokes (RANS) equations, are then performed to evaluate the performance of the rotor both at transient and steady state.
Gravitational water vortex power plant is a green technology that generates electricity from alternative or renewable energy source. In the vortex power plant, water is introduced into a circular basin tangentially that creates a free vortex and energy is extracted from the free vortex by using a turbine. The main advantages of this type of power plant is the generation of electricity from ultra-low hydraulic pressure and it is also environmental friendly. Since the hydraulic head requirement is as low as 1m, this type of power plant can be installed at a river or a stream to generate electricity for few houses. It is a new and not well-developed technology to harvest electricity from low pressure water energy sources. There are limited literatures available on the design, fabrication and physical geometry of the vortex turbine and generator. Past researches focus on the optimization of turbine design, inlets, outlets and basin geometry. However, there are still insufficient literatures available for the technology to proceed beyond prototyping stage. The maximum efficiency obtained by the researchers are approximately 30% while the commercial companies claimed about 50% of efficiency with 500W to 20kW of power generated. Hence, the aim of this paper is to determine the gap in the vortex power plant technology development through past works and a set of research recommendations will be developed as efforts to accelerate the development of GWVPP.
The geometric data for a broken blade of a horizontal axis micro-hydrokinetic turbine were obtained by reverse engineering and, reconstructed model was validated by re-engineering process and experiment. A direct scanning procedure was applied in order to verify the blade profile and stagger angles. Two computation methods were used in order to validate technical data of the turbine. For the first was used the classical computation method and, for the second method, the principle of extraction the maximum power from the fluid flow was considered. Differences for stagger angles of the blades were found, and an increased hydraulic power of 7%, when using the second design method comparing to the initial data. After re-engineering, the new runner was manufactured by a rapid prototyping method and was tested for data validation. Experiments confirmed the theoretical results with a good precision. Increased hydraulic power by 5% was recorded.
Absract: In the present paper an attempt has been made to develop the correlations for the cost of different components of canal based small hydropower (SHP) schemes. The cost has been determined based on actual quantities of various items having prevailing rates. The developed correlations give the plant cost as the function of cost sensitive parameters for various layouts based on different type of turbines and generators. An attempt has also been made to evolve the optimum selection of layout based on installation cost, generation cost and benefit cost ratio at different load factors. It has been found that the power house layout having tubular turbine with propellor runner and induction genertor is optimum layout at high load factors i.e. 90 to 100%, while, layout having bulb turbine with Kaplan runner is optimum at low load factor (50%).
Hydropower is an important renewable energy resource worldwide. However, its development is accompanied with environmental and social drawbacks. Issues of degradation of the environment and climate change can negatively impact hydropower generation. A sustainable hydropower project is possible, but needs proper planning and careful system design to manage the challenges. Well-planned hydropower projects can contribute to supply sustainable energy. An up-to-date knowledge is necessary for energy planners, investors, and other stakeholders to make informed decisions concerning hydropower projects. This is basically a review paper. Apart from using expert knowledge, the authors have also consulted extensively from journals, conference papers, reports, and some documents to get secondary information on the subject. The paper has reviewed the world energy scenario and how hydropower fits in as the solution to the global sustainable energy challenge. Issues of hydropower resource availability, technology, environment and climate change have been also discussed. Hydropower is sensitive to the state of environment, and climate change. With global climate change, though globally the potential is stated to slightly increase, some countries will experience a decrease in potential with increased risks. Adaptation measures are required to sustainably generate hydropower. These are also discussed in the paper.
Tidal current generation uses a generator to produce energy, changing the kinetic energy of current into a turning force by setting a water turbine in the tidal current. Therefore, it is considered to be very advantageous to use a water turbine that can always revolve in a fixed direction without any influence from tidal current directions. Water turbines with these characteristics are known as Darrieus water turbines. In this paper we investigated the new type of concept of water-current turbine, called Achard turbine. Two-dimensional numerical modelling of the unsteady flow through the blades of the Achard turbine, is performed using Fluent 6.3 software.
This study presents the results of a life cycle assessment of energy usage and greenhouse gas (GHG) emissions from electricity generation by small hydroelectric projects for understanding the characteristics of these systems from the perspective of global warming. Two types of hydropower schemes, viz. canal-based and dam-toe schemes, have been analyzed. The energy pay-back time for canal-based scheme is found in the range of 1.18–1.31 years. The corresponding values for dam-toe are 0.44–1.12 years. Similarly, GHG emissions (gCO2eq/kWhe) from canal-based and dam-toe schemes are in the range of 32.23–35.35 and 11.91–31.2 respectively. Using the economic input–output based life cycle assessment approach, energy pay-back timeand GHG emission have been quantified.
The problem of silt erosion is prevalent in hydropower plants of the Himalayan region. In the present study, a measurement methodology is undertaken to investigate the erosion damages of the Francis turbine components of unit-2 of Bhilangana-III Hydro Electric Plant. For the operation of 6993.12 hours, a total sediment load of 29291 MT was passed through the turbine. Around 90% of suspended silt particles were less than 300 μm size, with a modified shape factor of 0.75. The maximum overall weight loss is found as 29 kg for the tungsten carbide coated runner. The initial clearance gap of the guide vanes was increased from 0.04-0.55 mm to 0.65 mm and 0.69 mm at leading and trailing edges, respectively. In the runner, the average thickness loss at the blade trailing edge was found as 3 mm, 1.25 mm, and 1.56 mm from shroud to hub for three different templates as per IEC-62364. The maximum erosion depth of 13 mm is measured for the curved part of the runner. The ripple pattern of erosion is observed to be responsible for the material loss from the runner. The observed erosion-prone zones of turbine components are further investigated through CFD analysis at the best efficiency point.
Savonius turbine is a prominent drag based turbine used for harnessing wind or water power. It can be customized for run-off river stream locations having ultra-low head (<1 m) and low water velocities, for the turbine is self-starting and requires low starting torque. However, considering its low efficiency, an improved blade design of the turbine is needed to enhance its performance. If a Savonius turbine can generate power by utilizing lift force in addition to drag force then its performance can be improved; however any changes in its design need to be experimentally verified. In this paper, the performance of a combined lift and drag based modified Savonius water turbine is investigated in an open flow water channel at different water velocities between 0.3 m/s and 0.5 m/s, which are commonly found in a perennial river. The semi-circular blade design is modified by combining straight (drag profile) and airfoil (lift profile) blades. Detailed measurements show that maximum coefficient of power (0.268) is higher than some of the recently modified designs of Savonius water turbine. Further, correlation equations for power curves of the improved design for river stream application are also developed. The present work delineates the significance of modified Savonius turbine for efficient and cleaner production of water power.
Small Hydropower (SHP) plants interrupt river continuity, fish migration, and change downstream flow regime during operation. This study quantifies the ecological impacts of Small Hydropower (SHP) plants by using environmental monitoring data, site surveys and documented evidence based on an integrated approach. The ecological criteria are taken from the internationally recognized Swiss Water Protection Act and EU Water Framework Directive as follows: (i) environmental flow, (ii) hydropeaking, (iii) fish protection and fish passage, and (iv) sediment management. For a case study, Çataloluk SHP plant’s, which has been in operation in the Ceyhan River Basin in Turkey, ecological impact has been assessed. The ecological impact scorecard of the facility reveals that there are significant gaps relative to basic good practice for hydropeaking, downstream fish passage, and sediment management. The following mitigation measures are proposed: enhancement of the environmental flow, construction of a retention basin for hydropeaking, installation of fish-friendly fine screens at the water intake, installation of brush blocks and substrate in the pools of vertical slot fish pass, and the usage of hydro-suction technology for sustainable sediment management.
Hydrokinetic turbines are electromechanical devices, which convert the kinetic energy of freely flowing water into electricity without accumulating water. Turbine blades are generated by optimally combining one or more types of blade sections. The performance of blade sections is quite important directly affecting the power coefficient of the rotor. Since hydrokinetic technology is relatively a new branch of renewable energy, blade sections optimized for wind turbines or aviation applications had hitherto been used. However, hydrodynamics of water should be better considered during design processes. The main scope of this study is to optimize blade sections specifically for stall regulated hydrokinetic turbines considering high hydrodynamic forces, cavitation, leading-edge contamination, and ideal stall behavior. Differential Evolution Algorithm (DEA) was employed for the optimization process. Five different primary hydrofoil families were optimized and they have been scaled for various regions along the blade. Lift, drag, transition, and pressure coefficient performances of optimized sections have been analyzed and discussed with mostly used NACA, RISØ, and NREL sections. The optimized hydrofoils are found to deliver quite successful performance for hydrokinetic turbines based on design objectives, constraints , and comparing to the most preferred sections.
With the exploitation of most of the conventional hydropower sites, novel and innovative technologies are being developed to harness the hydropower. In this era, hydrokinetic technologies have emerged as the promising solutions to tap the vast hydrokinetic energy available in riverine system. Various studies on the hydrokinetic technology are being carried out. The main issue regarding the hydrokinetic energy is the assessment of hydrokinetic potential of the vast network of rivers and canals. Under the present paper, a methodology is presented to assess the hydrokinetic potential of eastern Yamuna main canal. Based on the analysis, it has been observed that eastern Yamuna canal has the maximum potential of 26.48 MW. Further, for maximum flow velocity, 904 arrays are required with two units per array to tap the hydrokinetic potential of Yamuna canal. The requirement of array increases with the reduction in flow velocity.
The present work is carried out to study the performance of a Savonius rotor for small-scale hydropower generation. It has been observed that some of the irrigation channels available in the rural areas are having enough bed slope to generate kinetic energy, which can be harnessed through a Savonius rotor. An in-house fabricated scale-down model of the Savonius rotor is tested at an inclination of the re-circulating indoor multipurpose tilting flume at 0°, 0.5°, 1.0°, 1.5° and 2.0° to determine performance under controlled conditions. It is observed that at the tip speed ratio of 0.92 and channel inclination of 0.5° compared to 0° inclination, the coefficient of power and coefficient of torque improved to 40% and 10%, respectively. Furthermore, it is found that the torque and power developed by the turbine are maximum at a bed slope of 2.0° owing to the maximum available energy.
Savonius hydrokinetic turbine is considered as an environmentally friendly and cost effective turbine to extract hydrokinetic potential available in flowing streams. However, this turbine has not been fully explored, as the solution for the main problem of low efficiency of Savonius turbine is still being investigated around the globe. In order to study the effect of number of stages, this study aims to analyze the performance of modified Savonius hydrokinetic turbine having twisted blade under different values of number of stages. A commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-ε turbulence model has been used for the numerical analysis. Pressure and velocity distribution found around the rotor have also been analyzed and discussed. Based on the present investigation, the maximum power coefficient value of 0.44 is obtained for double stage turbine corresponding to tip speed ratio (TSR) value of 0.9 at Reynolds number of 37.53×104. Using numerical data obtained, correlation has been developed for power coefficient as a function of number of stages Reynolds number and tip speed ratio.
Utilization of hydro-power as a renewable energy source is now of prime importance in the world. Hydropower energy is available in abundance as a renewable source. For run-of river, low head reaction type Kaplan turbines mostly used. In this paper, a parametric study has been conducted on a complex geometry of Kaplan blade through static and dynamic computational analysis by varying the blade profile at different angles in the CAD model. Blade geometry surface and design were developed in Creo using the coordinate point system on the blade.
Further blade profiles were analyzed to check and compare the output results. Results show that by changing the blade profile geometry, CAD models can be improved using the computational techniques. Consequences obtained were validated with the experimental/operational data and then four different blade profiles were developed. Research consequences showed improvement in the power output of the turbine.
The energy sector is undergoing substantial transition with the integration of variable renewable energy sources, such as wind and solar energy. These sources come with hourly, daily, seasonal and yearly variations; raising the need for short and long-term energy storage technologies to guarantee the smooth and secure supply of electricity. This paper critically reviews the existing types of pumped-hydro storage plants, highlighting the advantages and disadvantages of each configuration. We propose some innovative arrangements for pumped-hydro storage, which increases the possibility to find suitable locations for building large-scale reservoirs for long-term energy and water storage. Some of the proposed arrangements are compared in a case study for the upper Zambezi water basin, which has considerable water storage limitations due to its flat topography and arid climate. Results demonstrate that the proposed combined short and long-term cycles pumped-storage arrangement could be a viable solution for energy storage and reduce the cost for water storage to near zero.
Hydrokinetic energy conversion systems are emerging as a viable solution for harnessing kinetic energy. However, the typical deployment location is highly space-constrained due to both the nature and the other uses of the river. Therefore, a modified conversion device to overcome these constraints is necessary. The research objective of this work was to evaluate and enhance the performance of multiple coaxial horizontal axis hydrokinetic turbines (HAHkTs) mounted on a single shaft. The hydrodynamic performance of different configurations of single- and multi- HAHkTs with blades made of carbon fiber polymer composites was evaluated in a water tunnel. Increasing the number of rotors of the turbine system from one to two enhanced efficiency by approximately 75% and lowered the operational tip speed ratio. The third rotor also enhanced the efficiency, but the improvement was less (about 32%) due to the slower flow passing this rotor. A duct reducer was also incorporated, and its effect was studied. Finally, the wake behavior and its effect on the multi-turbine system operation were examined by using a particle image velocimetry system. From the structure aspect, composite materials have the appropriate properties that suit the water turbine blades. The composite blades were manufactured using the out-of-autoclave process.
Recognized as a source of clean and renewable energy, small hydropower plays an important role in providing electricity, reducing poverty, optimizing energy structure, and reducing carbon emissions. In this study, taking the countries along the Belt and Road as the study areas, an index system is developed in order to calculate and analyze the small hydropower sustainability of existing small hydropower in related countries. Based on the categories of ecology and environment, society, economy, and politics, there are 16 indices employing the analytic hierarchy process (AHP) and fuzzy comprehensive evaluation model for calculation. Key regions for China's small hydropower to participate in the Belt and Road Strategy are indicated. It is concluded that the relationship between protection and development of small hydropower is not coordinated well in the key regions. Economic, social, and political factors are main restrictions for the development of small hydropower. Secondary indices, which should be focused on, are also put forward. Based on our results, some policy suggestions are proposed from the new development mode, investment and financing, green development ideas and evaluation index system. These suggestions could be used to promote the sustainable utilization and green development of small hydropower in related countries along the Belt and Road.
Gravitational water vortex turbine (GWVT) is one of the emerging micro-hydro power plants because it requires less expertise, low head and reduced setup space for installation. A detailed performance evaluation of the GWVT based on turbine performance curves is yet to be explored. With the help of mathematical expressions along with the experimentation, the present study presents different performance parameters (PPs) such as; rotational speed, torque, brake power and mechanical efficiency of single-stage GWVT under various flow and design conditions. The effect of vortex height, runner position, percentage submergence of blades, notch angle, blades aspect ratio, blades curvature, blades inclination, hub diameter, straight and conical edged blades on the PPs has been investigated. The analytical and experimental results are in a good agreement with the both qualitatively and quantitatively. The experimental results show that the vortex height and a good vortex shape with fully developed air core are the major parameters in deciding the performance of GWVT. Better performance of GWVT can be achieved at middle of the rotational speed range i.e. between the minimum and maximum load conditions with minimum possible notch angle and hub diameter, using inclined blades of zero curvature fixed near the bottom of the basin.
Micro-hydropower has been highlighted as a potential technology suitable for installation in irrigation networks to reduce system overpressures and to reduce the net energy consumption of the irrigation process. However, the full impact of this technology on a large regional scale is unknown. Artificial Neural Networks and regression models were used in this research to predict the energy recovery potential for micro-hydropower in on-demand pressurised irrigation networks across a large spatial scale. Predictors of energy recovery potential across spatial unit areas included: Irrigated land surface area, irrigation crop water requirements, rainfall, evapotranspiration, and mean topographical slope. The model was used to predict the energy recovery potential across the 164,000 ha of the Spanish provinces of Seville and Cordoba in the absence of hydraulic models. A total of 21.05 GWh was identified as the energy potential which could have been recovered using micro-hydropower during the 2018 irrigation season. This amount of energy would have potentially reduced the energy consumption of the irrigation process in this region by approximately 12.8%. A reduction in energy consumption in the agriculture sector of this magnitude could have significant impacts on food production and climate change. The main novelty of this paper lies in the assessment of micro hydropower resources in operating irrigation networks on a large geographical scale, in areas where no information is available. It provides an approximation of the existing potential using computational methods.
A Savonius turbine is a vertical axis hydrokinetic turbine (VAHT) utilizes in low-speed channels and rivers. In comparison with the other hydrokinetic turbines, the Savonius turbine is simple in construction and installation, and involves less installation cost; however, these turbines have low torque and power coefficients in comparison with other hydrokinetic turbines. The idea of this paper is utilizing a simple barrier to deviate the fluid flow from the reversing bucket of the Savonius turbine to enhance its generated power. In order to investigate the most appropriate length of the barrier, numerical modeling has been performed by applying computational fluid dynamics (CFD). The continuity, Reynolds Averaged Navier-Stokes – RANS equations and the SST transition turbulence model are numerically solved. The validation of the numerical simulation is assessed based on the experimental data of Sandia laboratories, and the results indicated good agreement with experimental data. Thereupon, the model is utilized for optimizing the length of the barrier in various cases. The power coefficient of different cases is compared with the obstacle-less conventional Savonius turbine. The results of this analysis reveal that utilizing a barrier in its optimum length increases the maximum generated power by about 18 percent.
Power generation utilizing the kinetic energy of river flow, tidal, and ocean currents have encouraged the use of Darrieus turbines. However, the low power coefficient, poor self-starting characteristics, and lack of structural analysis have limited their usage. This study, as such, investigates the effect of a ducted augmented system on a Straight Blade Darrieus Hydrokinetic Turbine (SBDHT) to analyze performance, fluid loads, and stress-induced. A one-way Fluid-Structure Interaction (FSI) analysis followed the transfer of fluid forces to the structural module. Real-time hydraulic load and stress were computed and compared for ducted and non-ducted turbines. Computational Fluid Dynamic (CFD) analysis was performed to solve Reynolds Average Navier Stokes (RANS) equations, while turbulences were modeled using k−ω Shear Stress Transport (SST) model. CFD simulation revealed that, for the range of free stream velocity values, the duct augmentation system showed an increase in power production by 112% as compared to non-ducted turbines. The results also reveal that the ducted turbine will experience two-times the hydraulic loads in contrast to non-ducted turbines. Further, induced stress estimation revealed that 178.5 MPa and 94.68 MPa stresses were induced on the ducted and non-ducted turbine, respectively. The stress analysis result showed that maximum stresses occur within the turbine arms and at the joint between shaft and arms. It is, therefore, concluded that the ducted turbine approximately generates double power; however, it also experiences nearly twice stresses compared to the non-ducted turbine, which shall although increase the material cost of the turbine. This study, therefore, recommends that the duct augmentation system should be preferred choice while carefully designing such a system.
During operations, river and tidal hydrokinetic turbines encounter changes in flow direction that decrease their performance. Evaluating hydrokinetic turbines in yaw conditions contributes to estimating turbine performance, power stability, and power delivered to the grid. Water tunnel tests using a 19.8 cm diameter horizontal axis model turbine in yaw operation show the performance reduction using three designs: no shroud, a convergent-divergent shroud, and a diffuser shroud. Experimental results obtained at three Reynolds numbers of 1.38 × 10⁵, 1.77 × 10⁵, and 2.17 × 10⁵ show that the output power decreases in off-axis flows for all designs investigated. The reduction is initially negligible up to a 10° yaw angle, but then increases with increasing the yaw angle. The convergent–divergent shroud experiences significantly less performance loss compared to the other two designs. The maximum performance loss of the convergent-divergent shroud design is 6% on average for the Reynolds numbers investigated. Based on the experimental results and in analogy to the linear momentum theory cosine cubed rule, we propose new cosine relations for shrouded turbines in yaw operations. Depending on the shroud's geometry, the maximum power of a shrouded turbine decreases either with the cosine or the cosine squared of the yaw angle.
Large-scale energy storage systems, such as underground pumped-storage hydropower (UPSH) plants, are required in the current energy transition to variable renewable energies to balance supply and demand of electricity. In this paper, a novel method to determinate the round trip energy efficiency in pumped storage hydropower plants with underground lower reservoir is presented. Two Francis pump-turbines with a power output of 124.9 and 214.7 MW (turbine) and a power input of 114.8 and 199.7 MW (pump), respectively, have been selected to investigate the overall operation of UPSH plants. Analytical models and two-phase 3D CFD numerical simulations have been carried out to evaluate the energy generated and consumed, considering a typical water mass of 450,000 t and a maximum gross pressure of 4.41 MPa. The results obtained in both analytical and numerical models show that unlike conventional pumped-storage hydropower plants, the round trip energy efficiency depends on the pressure inside the underground reservoir. The round trip energy efficiency could be reduced from 77.3% to 73.8% when the reservoir pressure reaches -100 kPa. In terms of energy balance, the energy generation decreases down to 3,639 MWh year-1 and the energy consumption increases up to 4,606 MWh year-1 compared to optimal conditions.
Sweden, a country with abundant hydro power, has expectations to include more wind power into its electrical system. Currently, in order to improve the frequency response requirements of its electrical system, the country is considering upgrading its hydro-governors. This effort is part of maintaining the system frequency and reaction within their limits following any disturbance events. To partially compensate for increased frequency fluctuations due to an increased share of renewables on its system, the frequency response of hydro-governors should be improved. This paper proposes an innovative network control system, through a supplementary control, for the improvement of the hydro-governor’s action. This supplementary control allows having more flexibility over the control action and improves the primary frequency control, and thereby the overall system frequency response. The proposed supplementary control, based on an evolutionary game theory strategy, uses remote measurements and a hierarchical dynamic adjustment of the control. Additionally, in order to guarantee an optimal response, a Simulated Annealing Algorithm (SAA) is combined with the supplementary control. This paper illustrates the analysis and design of the proposed methodology, and is tested on two power systems models: (i) an aggregated model that represents the frequency response of Sweden, Norway and Finland, and (ii) The Nordic 32 test system.
Darrieus turbine is used as a hydrokinetic turbine to extract energy from flowing fluid in river, canal or drainage systems. In the present investigation, the performance of a Darrieus turbine is enhanced using a blocking plate optimally located at the upstream side of the retarding vane. An experimental investigation is carried out to obtain a specific width and the location of the blocking plate which would enhance the coefficient of power of the turbine. Three blocking plates (75 mm width, 100 mm width and 170 mm width) are investigated for five different locations. The coefficient of power of a turbine without blocking plate is enhanced from 0.125 to 0.36 by using an optimized blocking plate width and location. An empirical correlation for coefficient of power is suggested in terms of Reynolds number, Froude number, width ratio and location ratio.
This paper developed a horizontal axis micro-hydrokinetic river turbine (HAMHRT) technology for local renewable energy applications. Firstly, a hydrofoil shape was selected, and the hydrodynamic and cavitation characteristics of the hydrofoils were analyzed, then the chord length and twist angle for different blade location were optimal, and finally a 2 m diameter with 3-bladed HAMHRT was designed. Then, the numerical computational model of a hydrodynamic analysis for the prototype HAMHRT was carried out to determine force distributions along the blade under normal and extreme operating conditions, including the non-designed conditions, different tip speed ratios as well as the different pitch angles. The rotor has a maximum efficiency of 25.2% at the river current speed of 0.8 m/s, pitch angle of 4° and TSR of 6. It is ensured that the rotor performance does not deteriorate in a relative large scope even if the current speed changes or if the TSR deviates from the design values. Finally, the unsteady behaviors of hydrodynamics of this HAMHRT were analyzed farther. From the output performance of this turbine, the designed rotor was found to have stable power output and good efficiency at current speeding conditions.
Corrosion of massive components used in hydropower plants causes considerable technical problems and economic losses. Due to the corrosive environment and strong dynamic loading, such components must meet high demands. Quality of the components is essentially influenced by quality of material—chemical composition, correct metallurgical processes and also good practice of subsequent forming and welding technology.
Aim of the analysis was to determine the failure cause of the massive casing of draft tube from turbine used in hydropower plant. The main part of this study was focused on detailed analysis of chemical composition and microstructural analysis of the failed component. Light microscopy and scanning electron microscopy techniques together with energy dispersive spectroscopy were used for assessment and detailed evaluation of present phases.
Detailed analysis determined corrosion attack to be intergranular corrosion. Furthermore influence of deviations in chemical composition and presence of a typical titanium nitrides on corrosion resistance of material were identified.
Savonius hydrokinetic turbine is one of the prominent vertical axis turbines for tapping hydro potential available in flowing streams in rivers or canals. In spite of their simple design, Savonius turbines have the problem of poor performance. This study aims to enhance the performance of turbine through modification in the blade shape. Under the present study, geometrical parameters namely blade arc angle and blade shape factor are considered to modify the blade shape of Savonius hydrokinetic turbine. A commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-ε turbulence model has been used for numerical analysis. Using CFD analysis, blade arc angle and blade shape factor are optimized on the basis of coefficient of power. Fluid flow distributions found around the rotor has also been analyzed and discussed. Based on the present investigation, the maximum power coefficient value of 0.426 is obtained for blade arc angle of 150° and blade shape factor of 0.6 corresponding to TSR value of 0.9 at flow velocity of 2 m/s.
In the quest for renewable energy sources, kinetic energy available in small water streams, river streams or human-made canals may provide new avenue which can be harnessed by using hydrokinetic turbines. Savonius hydrokinetic turbine is vertical axis turbine having drag based rotor and suitable for a lower flow velocity of the water stream. In order to enhance the efficiency of the turbine, this paper aims to analyze the performance of twisted blade Savonius hydrokinetic turbine. Using CFD analysis, an attempt has been made to optimize blade twist angle of Savonius hydrokinetic turbine. The simulation of a twisted Savonius hydrokinetic turbine having two blades has been carried out to investigate the performance. Commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-ε turbulence model has been used for numerical analysis. Fluid flow distributions around the rotor have been analyzed and discussed. It has been found that Savonius hydrokinetic turbine having a twist angle of 12.5° yields a maximum coefficient of power as 0.39 corresponding to a TSR value of 0.9 for a given water velocity of 2 m/s.
The energy flow rate per unit flow area of water flow is quite high compared to air flow. This is because of high density of water compared to that of air. Hence, hydrokinetic turbine has the potential to extract more power compared to wind turbine for the same size of a turbine. The Darrieus turbine is one of the best options which can be used as a hydrokinetic turbine due to its high coefficient of power. In present work, the experimental investigations are carried out to study the hydrodynamic performance of three bladed Darrieus turbine with NACA0015, NACA0018 and NACA4415 blades for different solidities. Maxwell’s velocity correction method is used to account for blockage effect. NACA0015 and NACA0018 provide highest coefficient of power of 0.15 at a solidity of around 0.382. Experiments are extended to evaluate performance for four bladed rotors with symmetric-NACA0018 and cambered-NACA4415 hydrofoils. Both the hydrofoils provide a coefficient of power of around 0.13 but at different solidities. The effect of spanwise and streamwise distance on performance of a Darrieus turbine is investigated for its use as hydrofarm. A minimum distance of 7D along the streamwise direction and 3D along the spanwise direction are essential in a hydrofarm using Darrieus turbines.
The transition to renewable energy technologies raises new and important governance questions. With small hydropower (SHP) expanding as part of renewable energy and climate mitigation strategies, this review assesses its impacts and identifies escalating policy issues. To provide a comprehensive literature review of small hydropower, we evaluated over 3600 articles and policy documents. This review identified four major concerns: (1) confusion in small hydropower definitions is convoluting scholarship and policy-making; (2) there is a lack of knowledge and acknowledgement of small hydropower’s social, environmental, and cumulative impacts; (3) small hydropower’s promotion as a climate mitigation strategy can negatively affect local communities, posing contradictions for climate change policy; and (4) institutional analysis is needed to facilitate renewable energy integration with existing environmental laws to ensure sustainable energy development. For readers interested in small hydropower, we clarify areas of confusion in definition and explain the corresponding impacts for distinct system designs. For a broader readership, we situate small hydropower implementation within international trends of renewable energy development – the contradictory impacts of climate change policy, emerging dynamics in energy finance, and reliance on market mechanisms. Our paper provides a timely contribution to scholarship on small hydropower and the transition to renewable energy.
Energy crisis and high emission of fossil fuels are major driving forces for developing renewable energy based technologies. In order to meet growing demand for energy, hydropower can be one of the sustainable alternatives. Further, the hydrokinetic turbine is considered as one of the most emerging technologies which harness energy from flowing water. In this paper, an attempt has been made to review hydrokinetic energy theory for energy conversion system from water currents analogous to wind power system. The most widespread classes of hydrokinetic turbines are discussed in detail with respect to their benefits, drawbacks and desirable conditions for applications. It has been found that in spite of some prevailing downsides of vertical axis turbine like of self-starting and lower efficiency, vertical axis turbines are appealing for many riverine applications. One of the prominent turbines of its kind is the Savonius hydrokinetic turbine that has the capacity to self-start at a very low fluid velocity in the river, canal etc. However, Savonius type hydrokinetic turbine inherently has poor efficiency. A number of experimental and numerical studies with a large number of physical designs and parameters have been carried out in the area of Savonius rotor to enhance its efficiency. Under this study, review of different parameters affecting the performance of Savonius hydrokinetic turbine has been carried out and presented in this paper which may be useful for future studies to improve the efficiency of such turbines.
The PR China has been very fast developing its energy sector in order to sustain its impressive economic growth. China's installed hydropower capacity is not only the highest in the world; it also shows a globally unique dimension in growth and dynamic. The southwestern province of Yunnan has one of the highest hydropower potentials within China. Its development makes the province one of the key suppliers of electric energy in China, supplying the economic and energy hungry load centers of coastal China but also Southeast Asia. In a decade Yunnan will have an installed hydropower capacity that exceeds that of Canada or the United States. The province is therefore often referred to as China's forthcoming (hydro-) powerhouse or as Asia's battery.
Turbine types suit specific ranges of head, flow rate and shaft speed and are categorised by specific speed. In the pico range, under 5kW, the requirements are often different to that of larger scale turbines and qualitative requirements become more influential. Pico hydro turbines can be applied beyond these conventional application domains, for example at reduced heads, by using non-traditional components such as low speed generators. This paper describes a method to select which turbine architecture is most appropriate for a low-head pico hydro specification using quantitative and qualitative analyses of 13 turbine system architectures found in literature. Quantitative and qualitative selection criteria are determined from the particular requirements of the end user. The individual scores from this analysis are weighted based on perceived relative importance of each of the criteria against the original specification and selects a turbine variant based on the total weighted score. This methodology is applied to an example of a remote site, low head and variable flow specification and used to select a propeller turbine variant or single-jet Turgo turbine for this specification.