Technological Innovations and Advances in Hydropower Engineering

It has been more than 140 years since water was used to generate electricity. Especially since the 1970s, with the advancement of science and technology, new technologies, new processes, and new materials have been widely used in hydropower construction. Engineering equipment and technology, as well as cascade development, have become increasingly mature, making possible the construction of many high dams and large reservoirs in the world. However, with the passage of time, hydropower infrastructure such as reservoirs, dams, and power stations built in large numbers in the past are aging. This, coupled with singular use of hydropower, limits the development of hydropower in the future. This book reports the achievements in hydropower construction and the efforts of sustainable hydropower development made by various countries around the globe. These existing innovative studies and applications stimulate new ideas for the renewal of hydropower infrastructure and the further improvement of hydropower development and utilization efficiency

Transient safety assessment and risk mitigation of a hydroelectric generation system

Transient safety assessment of hydroelectric generation systems is a major challenge for engineers specialized in hydropower stations around the world. This includes two key scientific issues: the dynamic risk quantification in a multi-factors coupling process, and the identification of elements with highest contribution to system stability. This paper presents a novel and efficient dynamic safety assessment methodology for hydroelectric generation systems (HGSs). Based on a comprehensive fuzzy-entropy evaluation method, the dynamic safety level of the system is estimated by means of probability values, and the influence rate of assessment indices on the HGS risk profile is also obtained. Moreover, a number of risk mitigation and maintenance amendment strategies are discussed to reduce the losses in operation and maintenance (O&M) costs at hydropower stations. The methodology is implemented and validated using an existing hydropower station experiencing a start-up transient process, results of which are shown to be beneficial to operators and risk managers. It is recommended that the presented methodology is applicable not only to the HGS’s start-up process but is also promisingly useful for largely fluctuating transient processes of other engineering facilities

The Very Low Head Turbine for hydropower generation in existing hydraulic infrastructures: State of the art and future challenges

The Very Low Head turbine (VLHT) is an axial flow turbine developed for heads below 4.5 m and flow rates up to 30 m3/s. In this work, the state of the art, the technological advancements and the scientific gaps were discussed and generalized, with a special focus on design, ecological behavior, costs, performance at different flows, heads and rotational speeds. The flow field and the hydraulic behavior under different configurations (e.g. in presence of cavitation and with an upstream obstacle) were described, with the aim of deriving engineering suggestions. Results of ecological tests were generalized (fish survival rate is more than 90%) by using the blade strike model, proposing an expeditious method for a preliminary appraisal of the ecological impact on downstream migrating fish. Despite the hundreds of installations worldwide, especially in existing barriers, some scientific gaps need to be better addressed yet, e.g., the influence of the number of blades and axis inclination on the efficiency, the influence of flow, head and rotational speed on the flow field and a quantification of the head losses through the trash rack above the runner

Modeling and Optimal Operation of Hydraulic, Wind and Photovoltaic Power Generation Systems

The transition to 100% renewable energy in the future is one of the most important ways of achieving "carbon peaking and carbon neutrality" and of reducing the adverse effects of climate change. In this process, the safe, stable and economical operation of renewable energy generation systems, represented by hydro-, wind and solar power, is particularly important, and has naturally become a key concern for researchers and engineers. Therefore, this book focuses on the fundamental and applied research on the modeling, control, monitoring and diagnosis of renewable energy generation systems, especially hydropower energy systems, and aims to provide some theoretical reference for researchers, power generation departments or government agencies

Analysis of a 115MW, 3 shaft, helium Brayton cycle

This research theme is originated from a development project that is going on in South Africa, for the design and construction of a closed cycle gas turbine plant using gas-cooled reactor as the heat source to generate 115 MW of electricity. South African Power utility company, Eskom, promotes this developmental work through its subsidiary called PBMR (Pebble Bed Modular Reactor). Some of the attractive features of this plant are the inherent and passive safety features, modular geometry, small evacuation area, small infrastructure requirements for the installation and running of the plant, small construction time, quick starting and stopping and also low operational cost. This exercise is looking at the operational aspects of a closed cycle gas turbine, the finding of which will have a direct input towards the successful development and commissioning of the plant. A thorough understanding of the fluid dynamics in this three-shaft system and its transient performance analysis were the two main objectives of this research work. A computer programme called GTSI, developed by a previous Cranfield University research student, has been used in this as a base programme for the performance analysis. Some modifications were done on this programme to improve its control abilities. The areas covered in the performance analysis are Start-up, Shutdown and Load ramping. A detailed literature survey has been conducted to learn from the helium Turbo machinery experiences, though it is very limited. A critical analysis on the design philosophy of the PBMR is also carried out as part of this research work. The performance analysis has shown the advantage, disadvantage and impact of various power modulation methods suggested for the PBMR. It has tracked the effect of the operations of the various valves included in the PBMR design. The start-up using a hot gas injection has been analysed in detail and a successful start region has been mapped. A start-up procedure is also written based on this. The analysis on the normal and emergency load rejection using various power modulation devices has been done and it stress the importance of more control facilities during full load rejection due to generator faults. A computational fluid dynamics (CFD) analysis, using commercial software, has been carried out on some geometry of the PBMR design to find out whether its flow characteristic will have any serious impact on the performance on the cycle during the load control of the plant. The analysis has demonstrated that there will not be much impact on the performance, during load control using pressure level changes, from this geometry. However, some locations in the geometry have been identified as areas where the flow is experiencing comparatively high pressure losses. Recommendations, which include modification in the physical design, were made to improve this. The CFD analysis has extended to a cascade to compare the flow behaviour of Air and Helium with an objective of using air, being inexpensive, to test the helium flow characteristic in a test rig to simulate the behavioural pattern of helium in the PBMR pressure vessel. The specification of a hypothetical test rig and the necessary scaling parameters has been derived from this exercise. This will be useful for designing test rigs during the developmental and operational stage of the PBMR project

A New Processing Method Combined with BP Neural Network for Francis Turbine Synthetic Characteristic Curve Research

A BP (backpropagation) neural network method is employed to solve the problems existing in the synthetic characteristic curve processing of hydroturbine at present that most studies are only concerned with data in the high efficiency and large guide vane opening area, which can hardly meet the research requirements of transition process especially in large fluctuation situation. The principle of the proposed method is to convert the nonlinear characteristics of turbine to torque and flow characteristics, which can be used for real-time simulation directly based on neural network. Results show that obtained sample data can be extended successfully to cover working areas wider under different operation conditions. Another major contribution of this paper is the resampling technique proposed in the paper to overcome the limitation to sample period simulation. In addition, a detailed analysis for improvements of iteration convergence of the pressure loop is proposed, leading to a better iterative convergence during the head pressure calculation. Actual applications verify that methods proposed in this paper have better simulation results which are closer to the field and provide a new perspective for hydroturbine synthetic characteristic curve fitting and modeling

CFD Modelling and Simulation of Water Turbines

The design and development of water turbines requires accurate methods for performance prediction. Numerical methods and modelling are becoming increasingly important tools to achieve better designs and more efficient turbines, reducing the time required in physical model testing. This book is focused on applying numerical simulations and models for water turbines to predict tool their performance. In this Special Issue, the different contributions of this book are classified into three state-of-the-art Topics: discussing the modelling of pump-turbines, the simulation of horizontal and vertical axis turbines for hydrokinetic applications and the modelling of hydropower plants. All the contributions to this book demonstrate the importance of the modelling and simulation of water turbines for hydropower energy. This new generation of models and simulations will play a major role in the global energy transition and energy crisis, and, of course, in the mitigation of climate change

An inverse design methodology for long last-stage steam turbine blades

The last stage of an axial steam turbine is characterized by transonic flow and high volume flow rates. The resulting turbine blades are very large in size and complex in shape. This poses great design challenges, which last-stage blades are infamous for amongst steam turbine designers. Additionally, two-phase flows of condensing steam are always the case, and accurate numerical predictions of performance become often arduous. Inverse design has been used for several years and with great success in a variety of turbomachinery applications. However, no specific inverse design strategy has been developed for large axial steam turbines, and last-stage blades in particular. The first requirement that comes to mind for a steam-turbine specific inverse method is the inclusion of two-phase e↵ects. However, several other problems arise when dealing with the geometries typical of the last stage. The aim of this project is to identify and analyse the problems and requirements, and then develop some specific solutions which will allow the creation of a dedicated inverse design procedure. The first part of the project deals with a traditional inverse method and the inclusion of two-phase effects. The problems are then highlighted and two attempts are made to create a methodology that would work for last-stage blades. After devising a new way of describing blade profiles, the first method is introduced, based on a transpiration model. The second method is circulation based, and works through the prescription of circumferentially averaged swirl velocity. Finally, a design strategy is suggested for the whole redesign of a last stage rotor

Optimization of small-scale axial turbine for distributed compressed air energy storage system

Small scale distributed compressed air energy storage (D-CAES) has been recognized as promising technology which can play major role in enhancing the use of renewable energy. Due to the transient behavior of the compressed air during the discharging phase, there are significant variations in air pressure, temperature and mass flow rate resulting in low turbine efficiency. This research aims to improve the expansion process of the small scale D-CAES system through optimization of a small scale axial turbine. A small scale axial air turbine has been developed using 1D Meanline approach and CFD simulation using ANSYS CFX 16.2. For improving the turbine efficiency, different optimization approaches like single and multi-operating point optimization have been performed. The turbine blade profiles for both stator and rotor have been optimized for minimum losses and maximum power output based on 3D CFD modelling and Multi Objective Genetic Algorithm (MOGA) optimization for single and multi-operating points. Using multi-operating point optimization, the maximum turbine efficiency of 82.767 % was achieved at the design point and this approach improved the overall efficiency of D-CAES system by 8.07% for a range of inlet mass flow rate indicating the potential of this optimization approach in turbine design development

Small-Scale Hydropower and Energy Recovery Interventions: Management, Optimization Processes and Hydraulic Machines Applications

Several topics in the small-scale hydropower sector are of great interest for pursuing the goal of a more sustainable relationship with the environment. The goal of this Special Issue entitled “Small-Scale Hydropower and Energy Recovery Interventions: Management, Optimization Processes and Hydraulic Machines Applications” was to collect the most important contributions from experts in this research field and to arouse interest in the scientific community towards a better understanding of what might be the main key aspects of the future hydropower sector. Indeed, the Guest Editors are confident that the Special Issue will have an important impact on the entire scientific community working in this research field that is currently facing important changes in paradigm to achieve the goal of net-zero emissions in both the energy and water sectors