Operation Of Hydropower Plants Research Articles

Finding Multiple Optimal Solutions to Optimal Load Distribution Problem in Hydropower Plant

Optimal load distribution (OLD) among generator units of a hydropower plant is a vital task for hydropower generation scheduling and management. Traditional optimization methods for solving this problem focus on finding a single optimal solution. However, many practical constraints on hydropower plant operation are very difficult, if not impossible, to be modeled, and the optimal solution found by those models might be of limited practical uses. This motivates us to find multiple optimal solutions to the OLD problem, which can provide more flexible choices for decision-making. Based on a special dynamic programming model, we use a modified shortest path algorithm to produce multiple solutions to the problem. It is shown that multiple optimal solutions exist for the case study of China’s Geheyan hydropower plant, and they are valuable for assessing the stability of generator units, showing the potential of reducing occurrence times of units across vibration areas.

An overview of small hydropower development in Lesotho: Challenges and prospects

Abstract Lesotho’s energy balance is largely dominated by combustible renewable resources. However, the country is well endowed with hydropower resources for the development of both large and small-scale hydropower projects. There are several challenges that have to be addressed in order to reap the full benefits of this resource. Some of the main challenges are high capital investment costs on projects of this nature and heavy siltation of small reservoirs due to extensive soil erosion. Various studies countrywide have identified 22 sites, with a combined potential of more than 20 MW to be suitable for small hydropower development. Of these sites, 4 have been developed to operational from mid 1980’s to early 1990’s. The plants were designed as hybrid system with diesel generator sets. Three of those plants operate on a river run-off system. It has been a general practice that the plants run on diesel for most periods of the year, which render them more expensive to run. Currently, 2 of the plants are mothballed as a result of the costs and other operational problems frequently encountered. This paper gives an overview of the setbacks that inhibit the smooth operation of small hydropower plants in Lesotho.

Daily streamflow prediction by ANFIS modeling: Application to Lower Zamanti Karst Basin, Turkey

Prediction of daily streamflow in mountainous karst basins by means of deterministic models requires vast amount of data which is often not available. Such predictions are critical for the optimal operation of hydropower plants utilizing streamflow. The powerful prediction tool adaptive neuro-fuzzy interference system ANFIS was used for prediction of downstream flow in the Zamanti River Basin. Model input parameters are upstream flow, precipitation and retrospective downstream flow. Four different models constructed and the model results were assessed by using the determination coefficient and the root mean square error. Applied models produced reliable prediction values. Model results reveal an acceptable deviation from observations at stream flows exceeding the average. The prediction success of the applied ANFIS model appears to be promising for streamflow prediction in similar hydrogeological settings.

The Fuzzy Comprehensive Evaluation of Hydropower Plant Production and Operating Conditions Based on the BP Neural Network Improved

With the rapid economic growth, the resources and environment condition gradually tightens. We need to accelerate the development of hydropower resources. The electric power produced by the hydropower plants is a kind of green power energy. The quality analysis of hydropower production operation condition will become the focus of our researching. In paper we construct a reasonable set of evaluating indicator system of hydropower production operation and have used the BP neural network and fuzzy quality synthetic to analyze the production and operation condition of several hydropower plants. Help hydropower to summarize experience.

Comprehensive system analysis of a multipurpose run-of-river power plant with holistic qualitative assessment

Alpine rivers have been channelized by significant river training works in the past two centuries and are now disconnected from their natural environment. In addition, their flow regime is often affected by hydropower plant operation. Also the risk of flood damages is increasing continuously due to urbanization requiring additional flood protection measures. Nevertheless, such trained rivers still have high potential for renewable energy production. Furthermore, there is often a need for biotope restoration and creation of leisure infrastructures. New hydraulic schemes on such rivers have a chance to obtain public acceptance only if they are designed as multipurpose projects, which can alone ensure high synergies between different goals. Multipurpose projects are complex systems and have to be assessed with an appropriate global approach. Based on a network thinking approach, this article presents a global qualitative system analysis specially adapted for a typical multipurpose run-of-river power plant for the six project themes involved: (1) hydraulic scheme and river flow regime, (2) energy, (3) economy, (4) leisure activities, (5) groundwater and (6) ecology. The qualitative network thinking method developed by Gomez and Probst for business strategies is, for the first time, applied and enhanced for the assessment of such a multipurpose hydraulic scheme. Each theme, i.e. purpose of the project, is analysed separately, followed by a comprehensive study of the six themes combined together. Based on a network representation of the global system, three groups of factors are distinguished describing the sizes, the operations and the goals of the project. The size factors characterize the main geometrical aspects of the hydraulic structures, which can define the best layout of the project. The operation factors allow the optimization of the management of the reservoir. Finally, the objective factors characterize the synergies obtained by the multipurpose project. The developed methodology is illustrated with a case study of a multipurpose hydroelectric run-of-river power plant.

Assessment of the economic impact of environmental constraints on short-term hydropower plant operation

Environmental constraints imposed on hydropower plant operation are usually given in the form of minimum environmental flows and, in some cases, in the form of maximum and minimum rates of change of flows, or ramping rates. Environmental constraints reduce the amount of water available to produce electricity and limit the contribution of peak hydropower plants to adapting the power supply to the demand and to providing certain ancillary services to the electrical grid, such as spinning reserve or load-frequency control. The objective of this paper is to assess the economic impact of environmental constraints on short-term hydropower plant operation. For that purpose, a revenue-driven daily optimization model based on mixed integer linear programming is used. The model considers the head variation and its influence on the units’ efficiency, as well as the option of starting-up or shutting-down the plant at any hour of the day, should it be advantageous, while releasing the environmental flow through the bottom outlets. In order to illustrate the applicability of the methodology, it is applied in a real hydropower plant under different operating conditions and environmental constraints.

Incorporating Penalty Function to Reduce Spill in Stochastic Dynamic Programming Based Reservoir Operation of Hydropower Plants

AbstractThis paper proposes a framework that includes a penalty function incorporated stochastic dynamic programming (SDP) model in order to derive the operation policy of the reservoir of a hydropower plant, with an aim to reduce the amount of spill during operation of the reservoir. SDP models with various inflow process assumptions (independent and Markov‐I) are developed and executed in order to derive the reservoir operation policies for the case study of a storage type hydropower plant located in Japan. The policy thus determined consists of target storage levels (end‐of‐period storage levels) for each combination of the beginning‐of‐period storage levels and the inflow states of the current period. A penalty function is incorporated in the classical SDP model with objective function that maximizes annual energy generation through operation of the reservoir. Due to the inclusion of the penalty function, operation policy of the reservoir changes in a way that ensures reduced spill. Simulations are carried out to identify reservoir storage guide curves based on the derived operation policies. Reservoir storage guide curves for different values of the coefficient of penalty function α are plotted for a study horizon of 64 years, and the corresponding average annual spill values are compared. It is observed that, with increasing values of α, the average annual spill decreases; however, the simulated average annual energy value is marginally reduced. The average annual energy generation can be checked vis‐à‐vis the average annual spill reduction, and the optimal value of α can be identified based on the cost functions associated with energy and spill. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Experimental investigation of vortex control with an axial jet in the draft tube of a model pump-turbine

The operation of hydropower plants, especially of pump-storage plants, changes since the deregulation of the energy market. They are increasingly operating at off-design conditions in order to follow the demand in the electrical grid. Therefore the ability of hydropower plants handling the operation in a wide range of off-design conditions has become more important. In this context one problem is the vortex rope in the draft tube, especially for Francis turbines and pump-turbines running in part load. An experimental investigation in mitigation of the vortex rope phenomenon by injecting water axially in the centre of the draft tube on a pump-turbine model was carried out. Also the mitigation by additionally injected air in the centre of the draft tube was analysed. The results of the experimental investigation are focused on the reduction of the pressure fluctuations in the draft tube. In this paper two different part-load operating points were investigated. One of these operating points is a high part load operating point where a vortex rope exists. The other one is a low part load operating point, where the pressure fluctuation is not caused by a vortex rope. The results of the investigation show, that the injection of stabilizing water can mitigate the pressure fluctuation caused by a vortex rope. But the investigation of operating points where the pressure fluctuation is not caused by a vortex rope shows, that there is no significant reduction in the pressure fluctuation by this method. In these operating points the method of injecting additionally air reduces the pressure fluctuation better.

The comparative analysis of model and prototype test results of Bulb turbine

This paper presents the problem of the hydropower plant oblique water inflow and its influence on the turbines operation. Oblique water inflow on the low head hydropower plant with bulb turbines influences turbine characteristics. The characteristics change occurs due to swirl incidence in the turbine inlet which spreads to the guide vanes inlet. Downstream, the flow conditions change is caused in the turbine runner in relation to the flow conditions without swirl inflow. Special attention is paid to the phenomenon of swirl flow incidence in the turbine conduit. With the aim of presenting and analyzing the oblique water inflow consequences on the hydropower plant operation, the existing turbine model tests results, performed in the laboratories, and the in situ prototype testing results have been used.

Hydropeaking indicators for characterization of the Upper-Rhone River in Switzerland

River channelization and the construction of high-head storage schemes have been the basis of agricultural and socio-economic development in many alpine regions. One example is the Upper-Rhone River in Switzerland. The Upper-Rhone’s morphology changed considerably between 1863 and 1960 as a result of two major channelizations and, from 1950 on, the construction of a large number of high-head storage hydropower schemes in the catchment. These modifications have brought large benefits to the local population, at the cost, however, of substantial disturbances in aquatic and terrestrial ecosystems in and along the river. A primary factor behind these disturbances is the alteration of the natural flow regime, namely hydropeaking due to the operation of the high-head storage hydropower plants. For sustainable river-restoration projects on regulated rivers, scientists and engineers now widely accept the necessity of integrated management of the river. Different aspects such as river morphology, sediment management, water quality, temperature, and the naturally variable flow regime should be considered simultaneously. Mitigation of non-natural, sub-daily flow fluctuations due to hydropeaking is a crucial step in restoring natural flow regimes, but is especially challenging due to the economic constraints such mitigation places upon hydropower plants. With the goal of addressing this challenge, this paper proposes three indicators to describe the flow regime of rivers in alpine catchments with and without high-head storage hydropower plants. The indicators quantify: (1) the seasonal distribution and transfer of water, (2) sub-daily flow fluctuations, and (3) the intensity and frequency of flow changes. Indicators are evaluated in a case study of the Upper-Rhone River for pre- and post-impact situations, and the benefit of a multipurpose project reducing hydropeaking on hydrologic conditions is quantified. Furthermore, the paper explores the possibility of using these indicators to link aquatic and terrestrial ecosystem well being to their hydrology.

WATER PARAMETERS EVOLUTION IN A HYDROELECTRIC SITE

This study presents the impact of the cascade arrangement of the hydropower plants of reversible bulb turbines (HPP) belonging to Lower Olt River, in south of Romania, on water quality. A comparative analysis of the water quality is performed for period of ten years of continuous operation of the hydro electrical site. The water physical-chemical parameters are considered and important issues over the water quality are studied: the support of aquatic environment, the hydro turbines impact, the pollutants storage, the water hardness influence over turbines and the environmental impact of hydropower plants operation.

Forecasting analysis of runoff for reservoir regulation of dams and weirs in terms of hydro power plant operation

In order to meet the needs of Hydropower Plant (HPP) production new algorithms and software were developed for daily, seasonal, annual and long-term control of the runoff for the design of dam and weirs. This control is carried out for monitored periods from 20 to 50 years. The control depends on economic considerations, namely that the accepted probability of required water power is 90%, i.e. concerning the runoff and in this way for the useful volume of water dams. The research is accomplished by a design with the observations. First the hydrometric stations are selected at the available analogy with the building project and then the correlative connection is found assessed by general and true correlative coefficients. The transferring to the project of the observations for the average annual and average monthly water discharges is made with the coefficient of the analogy. The theoretical probability curves are chosen with a minimum dispersion. By the last curves the average monthly distributions are settled with probability from 2% to 90% by statistical method.During the investigated period of the regulation the volumes of discharge, overflow and shortage are calculated as and the determination for the accepted volume of the reservoir if the normative probability of the need is executed. As well the power output of the HPP and its participation in the coverage of the charge diagram on the peak load, under peak load, daily and nightly part are determined in separate observed or forecasting periods. The upper problems about the design and the operation of HPP, water output, reservoir volume and coverage of the charge diagram are solved by iterations. Practical examples are given for the runoff and for the time forecasting system.

Adjustable speed operation of a hydropower plant associated to an irrigation reservoir

This paper deals with the issue of adjustable speed operation (ASO) of hydropower plants. The main idea of this technique is to allow the turbine speed to change in accordance with hydraulic conditions, thus improving the overall unit efficiency. General technical aspects of ASO are further discussed with special emphasis on the energy and operational benefits that may potentially result from its application. In order to assess these benefits, annual operation of a hydropower plant associated to an irrigation reservoir has been simulated under different scenarios, with both adjustable and fixed speed. Turbine operating range proved to be wider with ASO. In addition, simulation results confirm that considerable energy gains are expected to be obtained.

Real-time sediment monitoring in hydropower plants

Sediments have posed great challenges in the operation of Run-of-River (RoR) hydropower plants mainly built on sediment-laden rivers. The relationship between characteristics of sediments and the features of a power plant is not well known. The knowledge and experience gained so far is not enough to deal with the challenges that exist in the operation of hydropower plants with respect to sediment handling. Therefore, the need for real-time sediment monitoring in RoR hydropower plants can hardly be exaggerated. In connection with the Optimum Sediment Handling research programme, the authors were involved in sediment measurement in two of the power plants in Nepal and one in India. The real-time sediment monitoring system that was developed at NTNU and the manual water sampling techniques were employed to monitor the sediment concentration just upstream of the turbine. The sediment monitoring system was calibrated up to the level of observed concentration during the measurement period. In this paper, the authors present the procedures, instrument setup and obtained results from the real-time sediment monitoring system that was employed in these power plants.

Short-term hydropower production planning by stochastic programming

Within the framework of multi-stage mixed-integer linear stochastic programming we develop a short-term production plan for a price-taking hydropower plant operating under uncertainty. Current production must comply with the day-ahead commitments of the previous day which makes short-term production planning a matter of spatial distribution among the reservoirs of the plant. Day-ahead market prices and reservoir inflows are, however, uncertain beyond the current operation day and water must be allocated among the reservoirs in order to strike a balance between current profits and expected future profits. A demonstration is presented with data from a Norwegian hydropower producer and the Nordic power market at Nord Pool.

Response of the riverine fish community to the construction and operation of a diversion hydropower plant in central Chile

AbstractChilean rivers have a large potential for hydropower development, and they also contain a unique native fish fauna with a high level of endemism. Several diversion hydropower plants have recently been constructed in Chile; however, the response of fish communities to these new hydropower plant designs is not well known.Responses of native and non‐native fish to the construction and operation of a new hydropower plant that diverts water from two rivers were quantified. The Laja River is highly regulated and manipulated with three older (40 yr) dam‐based hydropower plants and irrigation diversions located upstream from the new facility. In contrast, the Rucúe River has no other hydropower facilities and is comparatively undisturbed.Prior to construction, the Laja River had a fish community with lower species richness compared with the Rucúe River. The fish community structure in the Laja River was dramatically altered after the new hydropower facility began operation. On the other hand, in the Rucúe River, even though abundance of fish declined, there was less of a change in the total fish community structure. The fish community in the Rucúe River exhibited greater resistance to change compared with the Laja River.The species most affected were the introduced salmonids and an endangered native speciesPercilia irwini.Although diversion hydropower designs may have less impact than traditional dam‐based hydropower facilities, results of this study indicate that diversion hydropower structures can cause large changes in the fish community.Copyright © 2006 John Wiley & Sons, Ltd.

A structural model for electricity prices with spikes: Measurement of spike risk and optimal policies for hydropower plant operation

This paper proposes a new model for electricity prices based on demand and supply, which we call a structural model. We show that the structural model can generate price spikes that fits the observed data better than those generated by other preceding models such as the jump diffusion model and the Box–Cox transformation model. We apply the structural model to obtain the optimal operation policy for a pumped-storage hydropower generator, and show that the structural model can provide more realistic optimal policies than the jump diffusion model.

Ecological consequences of hydropower development in Central America: impacts of small dams and water diversion on neotropical stream fish assemblages

AbstractSmall dams for hydropower have caused widespread alteration of Central American rivers, yet much of recent development has gone undocumented by scientists and conservationists. We examined the ecological effects of a small hydropower plant (Doña Julia Hydroelectric Center) on two low‐order streams (the Puerto Viejo River and Quebradon stream) draining a mountainous area of Costa Rica. Operation of the Doña Julia plant has dewatered these streams, reducing discharge to ∼10% of average annual flow. This study compared fish assemblage composition and aquatic habitat upstream and downstream of diversion dams on two streams and along a ∼4 km dewatered reach of the Puerto Viejo River in an attempt to evaluate current instream flow recommendations for regulated Costa Rican streams. Our results indicated that fish assemblages directly upstream and downstream of the dam on the third order Puerto Viejo River were dissimilar, suggesting that the small dam (< 15 m high) hindered movement of fishes. Along the ∼4 km dewatered reach of the Puerto Viejo River, species count increased with downstream distance from the dam. However, estimated species richness and overall fish abundance were not significantly correlated with downstream distance from the dam. Our results suggested that effects of stream dewatering may be most pronounced for a subset of species with more complex reproductive requirements, classified as equilibrium‐type species based on their life‐history. In the absence of changes to current operations, we expect that fish assemblages in the Puerto Viejo River will be increasingly dominated by opportunistic‐type, colonizing fish species. Operations of many other small hydropower plants in Costa Rica and other parts of Central America mirror those of Doña Julia; the methods and results of this study may be applicable to some of those projects. Copyright © 2006 John Wiley & Sons, Ltd.

A Structural Model for Electricity Prices with Spikes - Measurement of Jump Risk and Optimal Policies for Hydropower Plant Operation

This paper proposes a new, structural model for electricity prices. We show that unlike other electricity price models, such as the jump diffusion model and the Box-Cox transformation model, the structural model can directly and accurately incorporate the relationship between electricity demand and price spikes. We also illustrate the usefulness of the structural model for optimal power generation and risk management using the example of a pump-storage hydropower plant. The structural model can describe the probability of price spikes easily in terms of electricity demand, and provides more realistic optimal operation policies than the jump diffusion model.

Next Generation National-Wide Hydropower Integrated Scada System

Korea Water Resources Corporation (KOWACO), the only organization specialized in water resources management in Korea, is planning to establish a centralized control system for a related operation, in the central control room, of decision making as to water management and electric power generation.This plan is intended to convert the existing on-site operation system in each multi-purpose dam across the nation into a central operation system in the Corporation's head office, for which Generation Integrated Operating System (GIOS) will be established control center in the Corporation's head office and modernized nine (9) power stations, substations (RDAC). This article discusses realization of GIOS, especially real-time operation of hydropower plants and a specific architectural features for system communication.