Pumped-storage Operation Research Articles

Simulation Models for Hydro-Electric Energy by Steady-Rate and Night-Shift-Pumped-Storage Operations

New operation simulation models for hydroelectric energy and its financial benefit over an N-year period in daily time steps by the steady-rate and the open-loop night-shift-pumped-storage rules are developed. These models are applied on 11 existing dams in Türkiye, which reflect a wide range of hydrologic and hydraulic peculiarities, for regulations between 90% through 40% and the outputs are compared. Regulation is the ratio of (outflow for energy generation, hm3/day) / (average inflow, hm3/day). The present worths of energy benefits and of pumping costs computed with a discount rate of 9.5% over a 35-year period yield that the night-shift pumped-storage operations are more profitable than the steady-rate rule. Finally, generalized regression equations for average annual produced energy and for present worth of net benefits by both operation rules against statistically significant explanatory variables are developed using the results of these 11 dams, which are all meaningful by relevant statistical criteria.

Dynamic analysis of variable-speed pumped storage plants for mitigating effects of excess wind power generation

The integration of hydropower and variable energy sources emerges as a functional method for handling power variability. Due to the advantage of adjustable power input of the pumped storage operation, variable-speed pumped storage plants (VSPSPs) have been proposed as a potential alternative to traditional fixed-speed pumped storage plants (FSPSPs) for dealing with the variable storage demand. The performance evaluation of VSPSPs in coping with changes in loads and variations in renewable energy sources during the energy storage process is crucial to ensure adequate flexibility and reliability of the grid. In this paper, the regulation performance assessment of VSPSP in mitigating wind power variations is presented based on IEEE 14-bus test system. The goal is to draw up the regulation reliability of the VSPSP under pumping mode for balancing the dynamic characteristics of wind power. Specifically, a numerical model of VSPSPs with doubly-fed induction machines is described and developed which is then validated by the measured data in the form of a case study. Moreover, by considering ten wind scenarios having differences in frequency, gradient, guts intensity, and standard deviation; simulations of VSPSP performing power regulation in the pump mode are conducted and the dynamic regulation effects are assessed. Finally, the power regulation quality comparison is provided between the power generation and storage modes to validate the regulation reliability of the VSPSP under the pumped storage operation. The regulation time delay (RTD) ratios of VSUs to FSUs are found in the range of 4.67–9.16%, demonstrating the rapidity of VSPSPs in the power regulation.

Combined effects of pumped-storage operation and climate change on thermal structure and water quality

The assessment of ecological impacts of pumped-storage (PS) hydropower plants on the two connected water bodies is usually based on present climatic conditions. However, significant changes in climate must be expected during their long concession periods. We, therefore, investigate the combined effects of climate change and PS operations on water temperature and quality, as well as extent and duration of stratification and ice cover, using a site in Switzerland. For this purpose, a coupled two-dimensional hydrodynamic and water quality model for the two connected water bodies is run with 150 years long synthetic stochastic meteorological forcing for both current and future climate conditions under two PS and two reference scenarios. The results show relevant synergistic and antagonistic effects of PS operations and climate change. For example, hypolimnion temperatures in September are projected to increase by < 0.6 °C in a near-natural reference scenario and by ~ 2.5 °C in an extended PS scenario. Ice cover, which occurs every year under near-natural conditions in the current climate, would almost completely vanish with extended PS operation in the future climate. Conversely, the expected negative impacts of climate change on hypolimnetic dissolved oxygen concentrations are partially counteracted by extended PS operations. We, therefore, recommend considering future climate conditions for the environmental impact assessment in the planning of new or the recommissioning of existing PS hydropower plants.

Effects of Lake–Reservoir Pumped-Storage Operations on Temperature and Water Quality

Pumped-storage (PS) hydropower plants are expected to make an important contribution to energy storage in the next decades with growing market shares of new renewable electricity. PS operations affect the water quality of the connected water bodies by exchanging water between them but also by deep water withdrawal from the upper water body. Here, we assess the importance of these two processes in the context of recommissioning a PS hydropower plant by simulating different scenarios with the numerical hydrodynamic and water quality model CE-QUAL-W2. For extended PS operations, the results show significant impacts of the water exchange between the two water bodies on the seasonal dynamics of temperatures, stratification, nutrients, and ice cover, especially in the smaller upper reservoir. Deep water withdrawal was shown to strongly decrease the strength of summer stratification in the upper reservoir, shortening its duration by ~1.5 months, consequently improving oxygen availability, and reducing the accumulation of nutrients in the hypolimnion. These findings highlight the importance of assessing the effects of different options for water withdrawal depths in the design of PS hydropower plants, as well as the relevance of defining a reference state when a PS facility is to be recommissioned.

Flow field in a reservoir subject to pumped-storage operation – in situ measurement and numerical modeling

In pumped-storage reservoirs, turbulent kinetic energy input from plant operation can be considerably high. Flow velocities were measured by Acoustic Doppler Current Profilers near the intake/outlet structure to describe flow patterns induced by pumped-storage operation in an Alpine reservoir. Recorded data allowed reproducing 1D and 2D velocity profiles along the water column. The comparison between the main frequencies of the velocity signal and the discharge series from the plant reveals correlation between recorded flow patterns and pumped-storage operation. Numerical modeling enhanced the understanding of flow patterns developing near the intake/outlet structure. Both results reveal that water withdrawal by pumping only marginally affects flow patterns in front of the intake, whereas water injected during turbine mode leads to backflow areas and large-scale recirculation cells. Numerical modeling further revealed that steady flow patterns are developing only after some 2.5 h of continuous turbine operation.

Economic analysis of Indian pumped storage schemes

Pumped-hydro energy storage schemes (PHES) are developed for improving the net efficiency of the base load thermal power plants. These schemes are operated only at times of peak demand and during major power plant outages. In India, the first pumped storage plant was commissioned during 1985 and till today eleven plants with on aggregate installed capacity of 4804MW have been in operation. However all these plants up to the year 2003 have generated energy less than the projected figures. The major reason for less output from the PHES in India, than that envisaged in the planning stage is deficit of off-peak power availability for pumping operation in almost all the regional power grids except north-eastern grid. But gradual increase in efficiency has been realized from PHES operation after introduction of the availability based tariff (ABT) in 2003. Further, the increase in peak power demand, requirement of spinning reserve, increased generation from renewable energy sources have singly and combinedly triggered the necessity for installation of more pumped storage schemes in the country. Under these circumstances, this analysis addresses the economics of pumped storage schemes in India with special reference to Kadamparai PHES. Various costs involved in pumped storage operation are analyzed in the Indian context. The case study reveals considerable techno-economic benefits obtained by more operational hours of the PHES in the state grid after 2003. The analysis and results would be useful for investors and researchers to understand the economics of Indian pumped storage schemes.

Continuous Long-Term Observation of Suspended Sediment Transport between Two Pumped-Storage Reservoirs

Transport of suspended sediment between the two reservoirs of a pumped-storage plant in Switzerland was monitored over an 8-month period. A turbidity probe was installed on the upstream end of the pressure shaft, in which real-time monitoring was ensured by automatic data acquisition and remote control. The suspended sediment concentration in the reservoirs varies considerably over the course of a year, with low particle loads in the winter, when the reservoirs are covered by ice and the catchment area is entirely covered by snow. In late spring, when snowmelt starts, the suspended sediment concentration increases and remains high until summer. The short-term evolution of the suspended sediment concentration was found to be correlated to the pumped-storage sequences, especially when the reservoir levels are low. Higher concentrations during pumping mode were observed for low levels in the lower reservoir, and low levels in the upper reservoir corresponded to higher sediment concentrations in turbine mode. Concentration ratios between pumping and turbine mode between 0.93 and 1.16 were observed. Periods with higher particle load were observed more frequently during pumping mode. Nevertheless, the suspended sediment balance due to pumped-storage operations is equilibrated, which indicates a high degree of correlation between the transported sediment volume and hydropower operation. Connecting the applied monitoring system in an existing plant control and management system would allow the plant operator to detect increased suspended sediment loads in the pressure shaft and to adapt the operation mode to actively manage reservoir sedimentation or to estimate and predict the long-term sediment balance.

Commercial Impact and Optimum Capacity Determination of Pumped Storage Hydro Plant for a Practical Power System

Abstract This paper attempts to study the commercial impact of pumped storage hydro plant on the operation of a stressed power system. The paper further attempts to compute the optimum capacity of the pumped storage scheme that can be provided on commercial basis for a practical power system. Unlike the analysis of commercial aspects of pumped storage scheme attempted in several papers, this paper is presented from the point of view of power system management of a practical system considering the impact of the scheme on the economic operation of the system. A realistic case study is presented as the many factors that influence the pumped storage operation vary widely from one system to another. The suitability of pumped storage for the particular generation mix of a system is well explored in the paper. To substantiate the economic impact of pumped storage on the system, the problem is formulated as a short-term hydrothermal scheduling problem involving power purchase which optimizes the quantum of power to be scheduled and the duration of operation. The optimization model is formulated using an algebraic modeling language, AMPL, which is then solved using the advanced MILP solver CPLEX.

Optimal Generation Planning for a Thermal System with Pumped-Storage Based on Analytical Production Costing Model

This paper presents a new algorithm for the optimal long-range generation planning for a thermal system with pumped-storage plants. The algorithm is based upon the analytical production costing model developed under the assumption of Gaussian probabilistic distribution of random load fluctuations and plant outages. The optimization problem consists of the master problem to determine the annual investment, and the pumped-storage subproblem to determine the optimal pumped-storage operation. The master problem is formulated as a Hamiltonian minimization problem, and the pumped-storage subproblem is solved using the concept of peak-shaving operation on the original load curve.

The limnology of Suviana—Brasimone man-made lakes: Influence of pumped storage operations on physical, chemical and biological characteristics

The limnology of Suviana—Brasimone man-made lakes: Influence of pumped storage operations on physical, chemical and biological characteristics

A Global Optimization Method for Scheduling Thermal Generation, Hydro Generation, and Economy Purchases

A key operating question facing the control staff at South Carolina Electric and Gas Company (SCE&G) is: "How should thermal generation be coordinated with pumped-storage operation and economy purchases to minimize the total system production costs?" To answer this complex question, SCE&G dispatchers are currently using a unit commitment program which can perform global optimization. The purpose of this paper is to describe the global optimization method, report computational experiences, and present a case study to illustrate practical applications.

ZOOPLANKTON COMMUNITIES OF A NEW PUMPED STORAGE RESERVOIR1

ABSTRACT: Zooplankton colonization was followed for 16 months in Lake Oconee, Georgia, a new pumped storage reservoir. Data were interpreted to identify differences among stations and seasons, as a function of the reservoir's early stage of development and of pumped storage operations. Colonization was rapid, and the zooplankton community was characterized by a high species diversity; approximately 40 rotifer species and 14 cladoceran genera were recorded. Zooplankton density varied along an environmental gradient from riverine to lentic conditions. Rotifer abundance varied from 104‐106 individuals/m3, with maxima in the summers Copepod and cladoceran densities ranged from 103 to nearly 105 individuals/m3; maxima for stations other than the dam were observed in the summer and early fall, but high values at the dam station occurred throughout winter 1980. When pumped storage operations began in December 1979, zooplankton densities increased at the dam station. Pumpback decreased the intensity of the environmental gradient from riverine to lentic conditions, and led to a more similar zooplankton community structure throughout the reservoir.

Effects of pumped storage operations on rotifer populations

Effects of pumped storage operations on rotifer populations

Pumpspeicherwerke und Hechtbrut—ein Modellversuch

The effects of periodic, simulated water level fluctuations on northern pike fry produced by pumped-storage operations were examined. Daily fluctuations of 10 cm caused a significant increase in the daily mortality rate. Waves reduced the detrimental effect of water level lfuctuations, at least during the adhesive phase of fry.

Predicting Quality Effects of Pumped Storage

Pumped storage operation (PSO) affects the water quality and in turn the resident biota. A predictive technique was adapted from a recently developed ecologic model to calculate the environmental changes and to evaluate the alternatives of PSO that might enhance a normal ecological succession, forestalling adverse environmental problems. The model, in an application to Smith Mountain Reservoir, Virginia, predicted accurately for an entire year the distributions of daily temperature, dissolved oxygen and other quality constituents that were measured and reported in the literature. PSO, under simulated conditions, was found to improve water quality by deepening the epilimnion. A prolonged pumping schedule at a reduced rate, however, was a better alternative because it would provide a more stable ecosystem without substantially altering the thermal stratification. Thermal stratification is necessary to regulate energy loss, and thus control evaporation and to ensure a varied environment suitable for hosting a diverse and stable biota.

Optimal Pumped Storage Operation with Interconnected Power Systems

This paper deals with the problem of obtaining the optimal scheduling of a pumped storage hydroelectric plant in combination with, several interconnected power systems. A special case of interest is the scheduling of pumped storage when the plant is jointly owned by several electric utilities. A mnathematical model is developed in order to determine the power flows between the different power systems and the pumped storage plant as well as the water flows inside the plant.

Advantages of Inclined-Axis Hydroelectric Units

The Corps of Engineers selected a relatively new type of low-head hydroelectric unit for installation at three multi-purpose projects now under construction. These units are known variously as inclined-axis, slant-axis and tube units. Unit blocks widths are 25% to 30% less with these units than with conventional vertical propeller units and therefore, a cost savings on the order of 10% to 15% can be realized. The units are similar in cost an in some other respects to bulb units but have the technical advantage of using conventionally designed generators operating outside the water passage. At two of the plants the units are planned for generation only while at the other plant they are to be reversible for pumped storage operation. The latter plant is part of the Kaysinger Bluff Project on the Osage River in Missouri. The other units are being installed at the Ozark and Webbers Falls Projects on the Arkansas River.