scholarly journals Long-term changes of Daugava River ice phenology under the impact of the cascade of hydro power plants

2016 ◽  
Vol 70 (2) ◽  
pp. 71-77
Author(s):  
Elga Apsîte ◽  
Didzis Elferts ◽  
Inese Latkovska
Keyword(s):  
Power Plants ◽  
Ice Cover ◽  
River Ice ◽  
Hydro Power ◽  
Long Term Changes ◽  
Break Up ◽  
Hydro Power Plants ◽  
The Impact ◽  
Ice Phenology

Abstract This paper presents the results of the study of long-term changes of Daugava River ice phenology, i.e. the freeze-up date, the break-up date, and the duration of ice cover from 1919/1920 to 2011/2012, under the impact of the cascade of hydro power plants. The long-term changes of ice phenology were determined by global climate warming at the turn of the 20th and the 21st centuries and anthropogenic activities after the year 1939. The Mann-Kendall test showed that the ice freeze-up date has a positive trend, while the ice break-up date and the duration of ice cover had negative trends. The changes were statistically significant. Data series covering twenty years before and after construction of the hydro power plants were used for assessing the impact of each hydro power plant on changes of Daugava River ice phenology parameters. The study results showed that the duration of ice cover was significantly longer in water reservoirs, i.e. the freeze-up date was earlier and the break-up date was later. Downstream of dams duration of ice cover was shorter with later freeze-up dates and earlier break-up dates. The impact of hydro power plants on ice phenology parameters gradually decreased with distance down from the dams.

scholarly journals Hydro Power Plants in the Interconnected Power System of Siberia: Trends and Problems

2020 ◽  
Vol 209 ◽  
pp. 05019
Author(s):  
V.M. Nikitin ◽  
E.N. Malinovskaya
Keyword(s):  
Power System ◽  
Power Plants ◽  
Current System ◽  
Strong Dependence ◽  
Hydro Power ◽  
Interconnected Power System ◽  
Design Values ◽  
Hydro Power Plants ◽  
Efficiency And Reliability

The paper discusses the trends, features, and current problems of the operation of hydro power plants in the interconnected power system (IPS) of Siberia. The main feature of the IPS of Siberia is a high proportion of hydro power plants and, as a result, a strong dependence of power generation on the natural fluctuations of water inflows into reservoirs. The problems affecting the power system efficiency arise when the inflows deviate from normal and close-to-normal values. The study indicates the need to improve the current system of managing and planning the operation of hydro power plants. The important factor that can increase the efficiency and reliability of the power system operation is bringing the permissible ranges of variations in reservoir levels in compliance with the design values. Planning the long-term power balances and increasing their validity should involve predictive scenarios of water inflows into reservoirs.

Long-term changes in lake ice cover in Finland*

2006 ◽  
Vol 37 (4-5) ◽  
pp. 347-363 ◽  
Author(s):  
Johanna Korhonen
Keyword(s):  
Time Series ◽  
19Th Century ◽  
Ice Cover ◽  
Ice Thickness ◽  
Lake Ice ◽  
Early 19Th Century ◽  
Long Term Changes ◽  
Break Up ◽  
Thickness Measurements

The freeze-up and break-up records of almost ninety lakes, and ice thickness of about thirty lakes, were analysed in order to identify long-term changes in the ice regime in Finland. The longest time series of break-up and freeze-up of ice in lakes are available from the early 19th century, while the earliest ice thickness measurements started in the 1910s. The analysis showed that there is a significant change towards earlier ice break-up in Finland except in the very north from the late 19th century to the present time. There is also a significant trend towards later freeze-up and thus also towards a shorter ice cover duration for the longest time series. However, for most lakes, for which data are not available prior to 1900, there are no significant trends. The ice thickness seems to have increased over the last 40 years, although there are significant trends only in half of the investigated lakes and significant decrease in the maximum ice thickness was found in four lakes in southern Finland. The increased ice thickness is most likely due to heavy snow on the ice and production of snow ice.

scholarly journals Computational Fluid Dynamic Predictions on Effects of Screw Number on Performance of Single Blade Archimedes Screw Turbine

2018 ◽  
Vol 67 ◽  
pp. 04027
Author(s):  
Muhammad Ilham Maulana ◽  
Ahmad Syuhada ◽  
Fiqih Almas
Keyword(s):  
Computational Fluid Dynamic ◽  
Power Plants ◽  
Fluid Dynamic ◽  
Turbine Blades ◽  
Small Scale ◽  
Maximum Pressure ◽  
Hydro Power ◽  
Hydro Power Plants ◽  
Computational Fluid Dynamic Software ◽  
The Impact

One of the alternative solutions to reduce the impact of electricity crisis in Aceh and other isolated areas in Indonesia is by the construction of small-scale hydro power plants that can work efficiently on the heads lower than 10 meters. One suitable type of turbine applied to the head below 10 meters is the Archimedes screw turbine. Due to the lack of information about the application of low head power plants, resulting in applications of this type of turbine is still less in Indonesia. This paper examined the appropriate turbine model. Before experimental turbine testing, turbines were designed theoretically first and then analyzed numerically. The flow velocity and pressure patterns within the turbine were analyzed using ANSYS CFD (Computational Fluid Dynamic) software under design conditions for 7, 9 and 11 screw numbers for single blade turbine. Based on the results of pressure analysis, speed and turbulent kinetic energy, it found that turbine performance using 11 blades is better among the three turbines. However, the highest average speed was obtained on the turbine using 7 screws, which maximum pressure obtained on a turbine 7 screws of 1406 Pa, on 9 screws on plane 1301 Pa and at 11 screws of 1175 Pa. Based on the results of the analysis, it showed that the smaller the distance between the channel and turbine blades, the results were more efficient due to the absence of wasted streams. Therefore, the flow pressure in the inlet position all directly leaded to the tip off the blade to produce a momentum.

scholarly journals Development of Long-Term Forecast Energy Balances in the Power System of Siberia

2021 ◽  
Vol 289 ◽  
pp. 01008
Author(s):  
Elena Malinovskaya
Keyword(s):  
Power System ◽  
Power Plants ◽  
Strong Dependence ◽  
Energy System ◽  
Hydro Power ◽  
Interconnected Power System ◽  
Term Energy ◽  
Hydro Power Plants ◽  
Energy Balances

The article discusses the features of the development of long-term energy balances in the interconnected power system of Siberia (IPS). The main feature of the IPS of Siberia is a high proportion of hydro power plants and, as a result, a strong dependence of electricity generation on natural fluctuations in water inflow into reservoirs. In the power output of the HPPs of the Angara-Yenisei cascade, depending on the water availability conditions, the deviation from the long-term average values can be up to 30% or 31 ÷ 36 billion kWh per year. The development of long-term energy balances and an increase in the efficiency of the operation modes of the HPPs of the Angara-Yenisei cascade makes it possible to identify in advance possible risks in the operation of the water management system of the Angara-Yenisei basin and the unified energy system of Siberia, thereby ensuring a more balanced operation of the power system as a whole.

scholarly journals Analysis of ice phenology of lakes on the Tibetan Plateau from MODIS data

2012 ◽  
Vol 6 (3) ◽  
pp. 1739-1779
Author(s):  
J. Kropáček ◽  
F. Chen ◽  
S. Hoerz ◽  
V. Hochschild
Keyword(s):  
Tibetan Plateau ◽  
Ice Cover ◽  
Optical Data ◽  
Water Volume ◽  
The Tibetan Plateau ◽  
Large Lakes ◽  
Local Conditions ◽  
Break Up ◽  
The Impact ◽  
Ice Phenology

Abstract. Much attention has recently been paid to the impact of climate change at the Tibetan Plateau. This remote and harsh region includes a large system of endorheic (closed basin) lakes. Ice phenology i.e. the timing of freeze-up and break-up and the duration of the ice cover may provide valuable information about climate variations in this region. The ice phenology of 59 large lakes on the Tibetan Plateau was derived from Moderate Resolution Imaging Spectroradiometer (MODIS) 8-day composite data for the period from 2001 to 2010. Duration of the ice cover appears to have a high variability in the studied region due to both climate and local factors. Mean values for the duration of ice cover were calculated for four groups of lakes defined as distinct geographic regions. In each group several lakes showed anomalies in ice cover duration in the studied period. Possible reasons for such anomalous behavior are discussed. Furthermore, many lakes do not freeze up completely during some seasons. This was confirmed by inspection of high resolution optical data. Mild winter seasons, large water volume and/or high salinity are the most likely explanations. Trends in the ice cover duration derived by linear regression for all the studied lakes show a high variation in space. A correlation of ice phenology variables with parameters describing climatic and local conditions showed a high thermal dependency of the ice regime. It appears that the freeze onset and water clean of ice day appear to be more thermally determined than freeze-up and break-up dates in case of the studied lakes.

scholarly journals Effect of Symmetrically Switched Rectifier Topologies on the Frequency Regulation of Standalone Micro-Hydro Power Plants

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3201
Author(s):  
Henry Bory ◽  
Jose L. Martin ◽  
Iñigo Martinez de Alegria ◽  
Luis Vazquez
Keyword(s):  
Power Factor ◽  
Power Plants ◽  
Reactive Power ◽  
Alternating Current ◽  
Frequency Regulation ◽  
Hydro Power ◽  
Major Energy Source ◽  
Hydro Power Plants ◽  
Electronic Load ◽  
Ac Converters

Micro-hydro power plants (μHPPs) are a major energy source in grid-isolated zones because they do not require reservoirs and dams to be built. μHPPs operate in a standalone mode, but a continuously varying load generates voltage unbalances and frequency fluctuations which can cause long-term damage to plant components. One method of frequency regulation is the use of alternating current-alternating current (AC-AC) converters as an electronic load controller (ELC). The disadvantage of AC-AC converters is reactive power consumption with the associated decrease in both the power factor and the capacity of the alternator to deliver current. To avoid this disadvantage, we proposed two rectifier topologies combined with symmetrical switching. However, the performance of the frequency regulation loop with each topology remains unknown. Therefore, the objective of this work was to evaluate the performance of the frequency regulation loop when each topology, with a symmetrical switching form, was inserted. A MATLAB® model was implemented to simulate the frequency loop. The results from a μHPP case study in a small Cuban rural community called ‘Los Gallegos’ showed that the performance of the frequency regulation loop using the proposed topologies satisfied the standard frequency regulation and increased both the power factor and current delivery capabilities of the alternator.

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