There is currently a growing trend towards renewable energy sources, which are characterised by a guaranteed power supply and low failure rate. Hydropower plants (small or large) are an example of ...such a source. They supply a total of 16% of the world’s electricity. The advantages of a small hydropower plant include the relatively simple construction process and the lack of need for upstream water storage. SHPs are one of the most cost-effective and environmentally friendly energy technologies, which is why they are steadily increasing in popularity. One of the important components of SHPs are the trash racks in the inlet channels. Their main purpose is to catch debris and other elements carried downstream and to prevent these pollutants from reaching the turbine units. They can also protect migrating ichthyofauna such as larger fish. If trash racks are installed in the inlet channel, hydraulic losses are to be expected due to the reduction in the flow cross-section through the racks (bars) themselves and through the accumulation of debris and various types of trash on these racks. Energy losses on the trash racks affect the financial aspect of SHP investments. This paper presents the results of laboratory tests on trash racks for SHPs by taking into account the different shapes of the bars used, their number and spacing, and the angles of the trash racks to estimate the hydraulic losses on the trash racks. The measured values of hydraulic losses Δh on the trash racks varied according to the type of trash racks, the density of the bars in the cross-section, and the angle of the trash racks from the horizontal, reaching the highest values on the trash racks with angle bars (AB). They were almost eight times greater than those recorded on cylindrical-bar (CB) trash racks, although they involved different angles. It was shown that the discrepancy in the magnitude of losses on trash racks can be large, even for the same type of trash racks. It depends significantly on the design (shape and bar spacing) of the trash racks and the way the trash racks are installed. Depending on the inclination angle, the increase in energy losses reached 70% for angle bars, 60% for flat-bar trash racks, and almost 40% for cylindrical bars. The values of energy loss as well as the loss coefficient β varied non-linearly for the different bar types depending on the angle of inclination of the gratings, and the degree of this non-linearity depended on the type of bars and the blockage ratio of the section. The presented research results can be useful both during the design and the operation of an SHP.
Deposition of debris on the screens of hydroelectric power plants translates into measurable economic losses. Occurring plant debris, although it is an organic material, is characterised by different ...forms and structure. It is often leaves, branches, and grasses in lowland areas, while in mountainous regions, broken boughs and trees can be expected. On the trash racks of power plants, debris may be deposited in different forms, shapes, and places. This work aims to determine the impact of the degree of submergence of debris on the values of the force acting on the racks. This paper analyzes the influence of the rectangular shape of the debris deposited on the trash racks and its degree of submergence and weight on the obtained values of the force acting on the racks as a result of water pressure, which directly affects the hydraulic losses and productivity of hydroelectric power plants. Our research confirms the negative influence of the deposited plant debris on the value of forces recorded on the gratings. The increase in the recorded force, and thus the resistance on the grating, is obviously dependent on the degree of obstruction of the debris by the grating obtained by changing the degree of debris immersion and its weight. In the case of changing the degree of submergence, the increase in force recorded on the gratings varied during the experiment from about 25% recorded for the fully submerged debris compared to that of the partially submerged debris for the mass of 100 g; in comparison, an increase of about 31% was recorded for that of the mass of 200 g. However, comparing the values of the forces recorded on the obstructed grids to that of the forces recorded on the clean grids, the increase ranged from about 15–53%.
Almost every project is accompanied by earthworks, very often involving various types of excavation, and the work of people in the excavations. One of the most important tasks in earthworks is to ...ensure that the walls of the excavation are protected against sliding and that people working in and around the excavation are safe. Very often, in addition to criteria relating to safety and stability of the excavation, economic considerations are also an important criterion. This issue arises as early as the design stage and is related to the choice of construction and materials of which the shoring is to be made in such a way as to be able to withstand the pressure of the soil, ground loads resulting from stored excavated material and the operation of working machinery. Ongoing monitoring of the excavations and their reinforcement is also very important. The paper describes the unique results of experimental field tests, the purpose of which was to analyse the values of deflections of steel support plates of temporary excavation carried out on the object in 1:1 scale. The course of the experiment is presented for excavation support plates with a total depth of 6 m. Direct tests of the deflection arrow were carried out using two techniques, traditionally with a patch, and with laser scanning. Field tests were carried out for the designed situation without backfill load as well as for backfill load of 3.84, 15.36, 26.88 and 38.4 kN·m−2, respectively, for two measurement stages. Stage-I of the study consisted in collecting the results for soil in intact condition, whereas Stage-II collected results for loosened soil. The research experiment was supported by numerical calculations performed using the finite difference method in variational approach. The measured maximum deflections ranged from 14.40 to 16 mm, and the calculated values were 14.95 and 14.99 mm. The comparison of calculation results and tests proved to be very consistent. The analysis of the values of deflections showed that backfill load does not have a significant effect on the deflection of the lower plate, but it does affect the deflection of the first plate up to a depth of 1.2 m. Based on the obtained results, it is recommended to assume the limit (maximum) deflection arrow for support plates of temporary excavations at least as wgr = L/130, where L is the span of the plate. The calculation of deflection values was based on deflection values obtained experimentally and numerically for two steel variants: S235JR and S355JR. The wgr indicator of the maximum deflection arrow proposed by the authors is not stipulated by the industry standards, but it can be very helpful for the designing of excavation reinforcement.
Small hydropower plants are one of the most important renewable energy sources that do not degrade and consume natural resource. The paper presents a case study of an already operating small ...hydropower plant (SHP) and a potential increase in its energy production by raising the damming level. Three variants were defined and subjected to detailed analysing. The analyses used the Fuzzy AHP methodology (FAHP), which allowed for identifying the variant that has the best chance of being implemented in the context of administrative, legal and social realities of the country where an SHP is located. The adopted solution will increase electricity production by 108.78 MWh annually, while reducing carbon dioxide emissions by 86000 kg CO2. The described methodology is of general use and can be applied in any country in the world.
•The FAHP method was used to select the optimal variant of increasing the SHP damming level.•The proposed variant A1 will enable increased "green" energy production, and provide the best chances for implementation.•Variant A1 will enable an increase in electricity production by about 110 MWh per year and reduce CO2 emissions by 86,000 kg.•The proposed methodology can also be easily used for analysis and optimisation of other SHP facilities.
One of the biggest threats to many lakes is their accelerated eutrophication resulting from anthropogenic pressure, agricultural intensification, and climate change. A very important element of ...surface water protection in environmentally conserved areas is the proper monitoring of water quality and detection of potential threats by examining the physicochemical properties of water and performing statistical analyses that enable possible exposure of unfavourable trends. The article presents the analyses of the results of measurements made in three lakes located in the Sierakowski Landscape Park. As part of the measurements, water quality indicators i.e., phosphorus, nitrogen, BOD5 and COD, were determined monthly for a year at the inflows and outflows of the studied lakes. The test results of selected water quality indicators were analysed using machine learning algorithms i.e., PCA and k-means. The conducted tests enabled statistical estimation of changes in water quality indicators in the reservoirs and evaluation of their correlation.
Trash racks are the first element mounted in inlet channels of hydraulic structures. Their primary task is to capture coarse pollutants flowing in the riverbed/river channel and protect water ...facilities downstream. With the use of these devices, it is possible to separate coarse suspended matter, branches carried with the current, floating plastic elements, etc., which undoubtedly contributes to a trouble-free flow through culverts or channels and prevents hydroelectric power plant turbines from failure. An important issue here is also to ensure the proper operation of trash racks, particularly in respect of hydraulic structures whose task is to convert water energy into electricity (hydropower plants). Proper operation of trash racks minimizes losses arising from obstructing the free flow of water through accumulated waste or, in the wintertime, through icing. Incorrect work in this area entails specific head losses, and consequently leads to economic harm. In the paper, the resistance values of trash racks were analyzed at small hydropower plants (SHPs) operating at low temperatures, determined under laboratory conditions, with the occurrence of frazil ice and ice. The results indicate that the added ice into the channel resulted in the formation of a cover in front of the trash racks with an average thickness of about 0.02 m. The accumulated ice increased the head losses up to 14%. The range of the ice cover depended on the weight added ice and reached 0.6 m in analyzed cases.
The demographic and urban expansion of the nineteenth century led to a significant reduction in water resources. One of the considered solutions to this problem was to retain water in reservoirs. ...Over the years it has been recognized that the construction of small reservoirs can bring greater benefits than large ones. Large reservoirs are not only associated with substantial economic costs, i.e. for the purchase of land, but they also do not sufficiently serve as the components of a flood protection system. They are also of minor importance in the production of so-called ''white energy” (Lehner et al., 2005) and may have a negative impact on the environment. The size and age of reservoirs as well as the type of water dams and their work regime affect the scale of changes in the natural fluvial environment (Robinson et al., 2003). Small reservoirs are a basic element of small water retention, in which water quality depends to a large extent on their location, the way their catchment areas are managed and the functions they perform (apart from typical retention reservoirs). The catchments used for agricultural purposes may be susceptible to accumulation of biogenic substances (nitrogen and phosphorus), and other pollution (Hejduk, 2010; Kanownik et al., 2013; Kasperek et al., 2013; Wiatkowski et al., 2013). The article initially tested the quality of the water in three reservoirs, different period of operation with use of selected indicators. For the purposes of research and this resultant publication, water quality was tested in three reservoirs differing in operating times. It was assumed that the study period covering autumn, spring and early summer was the period with the most visible changes in concentrations of pollutants. Samples taken from the reservoirs were analysed by determining in turn biological oxygen demand (BOD5), ammonia concentration (NH4), phosphate concentration (PO4) and total suspended solids. The use of indicators allowed for assessing the quality of water in these reservoirs and comparing it in terms of different periods of their operation.
Floodplain vegetation is characterized by its ability to resist deformation and destruction and to deform elastically and plastically under the influence of external mechanical forces. The force of ...water that presses on the plant induces stress and deformation in it, but once the force is removed, the elastic properties of the vegetation return it to its original state. It regains its original size, shape, and volume. In this paper, the deflection arrow was analysed based on the field tests conducted, and then the modulus of elasticity of natural shrub vegetation was determined. Measurements were made at different plant heights. Analysis was carried out at different growing periods to estimate the variation of plant elasticity with growth, development, and season. The results confirm the loss of flexibility during winter for all the shrubs analysed. Based on the measurements carried out, the elastic modulus E of the shoots was estimated. The average modulus of elasticity ranged from about 2100 to about 4000 MPa and showed high variability, reaching even µ = 50%, both within a given shrub and depending on the measurement season. The results presented here indicate a high natural variability of mechanical parameters even within the same plant.
The protection and use of historic buildings is a difficult and costly task. Most often, these objects are under conservatory protection and any interference in their structure requires appropriate ...consent. On the other hand, conducting construction works on historic buildings carries a high risk of their damage or even destruction. Therefore, proper prior diagnostics is an extremely important factor affecting the scope and manner of works to be conducted. The paper presents the use of 3D scanning to determine the deflection of the ceiling under the Column Hall of the historic Palace, the floor of which showed elasticity, recorded during changing service loads. After identifying the places with the greatest deflections, based on data from 3D laser scanning, test holes were made and wood samples from the ceiling were taken to perform moisture content and mycological tests. An endoscopic inspection camera was inserted into test holes, providing the basis for recognizing the structure of the ceiling, i.e. arrangement of layers as well as dimensions and spacing of ceiling beams. Strength calculations were made with the limit state method resulted in the determination of the maximum permissible service load on the ceiling. The presented course of action in diagnostics of the analysed historic building may be an example of a preliminary procedure to be taken before deciding on changes in the manner of use of historic buildings or the functionalities of their individual parts.
We apply the modified Brodutch and Modi method of constructing geometric measures of correlations to obtain analytical expressions for measurement-induced geometric classical and quantum correlations ...based on the trace distance for two-qubit
X
states. Moreover, we study continuity of the classical and quantum correlations for these states. In particular, we show that these correlations may not be continuous.
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