abstract: Hydropower generation is one of the clean renewable energies which has received great attention in the power industry. Hydropower has been the leading source of renewable energy. It provides more than 86% of all electricity generated by renewable sources worldwide. Generally, the life span of a hydropower plant is considered as 30 to 50 years. Power plants over 30 years old usually conduct a feasibility study of rehabilitation on their entire facilities including infrastructure. By age 35, the forced outage rate increases by 10 percentage points compared to the previous year. Much longer outages occur in power plants older than 20 years. Consequently, the forced outage rate increases exponentially due to these longer outages. Although these long forced outages are not frequent, their impact is immense. If reasonable timing of rehabilitation is missed, an abrupt long-term outage could occur and additional unnecessary repairs and inefficiencies would follow. On the contrary, too early replacement might cause the waste of revenue. The hydropower plants of Korea Water Resources Corporation (hereafter K-water) are utilized for this study. Twenty-four K-water generators comprise the population for quantifying the reliability of each equipment. A facility in a hydropower plant is a repairable system because most failures can be fixed without replacing the entire facility. The fault data of each power plant are collected, within which only forced outage faults are considered as raw data for reliability analyses. The mean cumulative repair functions (MCF) of each facility are determined with the failure data tables, using Nelson's graph method. The power law model, a popular model for a repairable system, can also be obtained to represent representative equipment and system availability. The criterion-based analysis of HydroAmp is used to provide more accurate reliability of each power plant. Two case studies are presented to enhance the understanding of the availability of each power plant and represent economic evaluations for modernization. Also, equipment in a hydropower plant is categorized into two groups based on their reliability for determining modernization timing and their suitable replacement periods are obtained using simulation. / Dissertation/Thesis / M.S. Electrical Engineering 2011

Sedan 1970-talet har ålbeståndet minskat rejält och under de senaste decennierna har man försökt hitta en lösning på detta problem. En ökad naturlig rekrytering kan hjälpa ålarnas återhämtning. Varje år fastnar en stor mängd juvenila ålar vid vattenkraftverk. För att hjälpa ålarna ta sig förbi dessa kan man installera ramper, vilka hjälper ålarna att klättra förbi vattenkraftverken. Syftet med studien var att ta reda på vilken typ av substrat i ramper vid dessa vattenkraftverk som ålynglen föredrar. Studien utfördes utomhus i två odlingsbassänger där sex stycken ramper hade installerats. Den huvudsakliga studien bestod av ett selektionstest där ålynglen fick välja mellan tre olika substrat. Man antecknade också om det var några yngel som valde att stanna kvar, detta för att kunna testa om det fanns någon signifikant skillnad mellan importerade och vilda ålyngel när det gäller de yngel som inte valt någon av ramperna. Sammanlagt 500 yngel (vilda N=235, importerade N=265) var med i studien. Ålynglen placerades i nätkassar nedanför ramperna. Där hade de möjligheten att antingen välja ett av substraten och vandra uppför rampen, eller stanna kvar i bassängen. De tre substraten som testades var plastkätting, FishPass™ rigid brush mixed green (FishPass™) och Diadrain 25H (D-25). Resultatet blev att både de vilda och de importerade ålynglen föredrog FishPass™ och D-25 framför plastkätting. Det fanns ingen signifikant skillnad mellan FishPass™ och D-25. Man kom också fram till att signifikant fler vildfångade ålar än importerade valde att stanna kvar istället för att klättra upp för en ramp. Resultatet från den här studien säger att vi kan öka antalet juvenila ålar som tar sig förbi vattenkraftverk. Placerar man ut ramper klädda med antingen FishPass™ eller D-25 vid de vattenkraftverk där juvenila ålar har svårt att passera så kan man på så sätt hjälpa ålarnas naturliga rekrytering. / Since the 1970s, eel stocks have declined, and in the recent decades people have been trying to find a solution to this problem. An increased natural recruitment could help the eels to recover. Each year a large quantity of juvenile eels get stuck at hydroelectric plants. To help the eels pass by these plants, ramps can be installed, which help the eels to pass the dams. The purpose of the study was to find out what type of substrate in ramps at these hydropower plants that juvenile eels prefer. The study was conducted in two outdoor hatchery ponds where six ramps had been installed. The main study consisted of a selection test where juvenile eels had to choose between three different substrates. It was also recorded if there were some juveniles who chose to remain, in order to test if there was a significant difference between imported and wild eels when it comes to individuals that have not selected any of the ramps. A total of 500 juveniles (Wild N = 235, Imported N = 265) were included in the study. The juvenile eels were placed in net enclosures beneath the ramps, and had to choose one of the substrates and climb the ramp, or else remain in the net enclosure. The three substrates tested were plastic chain, Fish Pass ™ rigid brush mixed green (Fish Pass™) and Diadrain 25H (D-25). I found that both the wild and imported eels preferred Fish Pass™ and D-25 instead of the plastic chain. There was no significant difference between Fish Pass™ and D-25. It was also found that significantly more wild-caught than imported eels chose to stay in the enclosure instead of climbing up a ramp. The results from this study indicate that we can increase the number of juvenile eels that successfully pass by hydroelectric plants. If we place ramps covered with either Fish Pass™ or D-25 at the hydropower plants, we can help the eel’s natural recruitment.

In some environmental situations, environmental effects caused by elevated metals resulting from past mining and smelting activities can be observed in nearby receiving water bodies several decades after mine and smelter closure. There is a growing need for managing the hazardous solid wastes such as mining wastes as well as for assessing water quality and for sustainable management of sediment quality. The work presented in this thesis examined the mobilization of metals from two metal sources: mining wastes from a mine site in Vietnam and sediments from a contaminated lake in Sweden in order to test the hypothesis that mobilization of metals will be increased, when the environmental conditions change by e.g. exposure of mining wastes to oxidative weathering, change of redox conditions at the water-sediment interface and resuspension of sediments. The results from this work under field and laboratory conditions have verified the hypothesis. The exposure of sulphidic mining wastes in oxidative weathering conditions may cause long-term production of ARD and the resultant long-term mobility of metals. The oxidation/resuspension of sediments is an important factor for the release of trace metals Zn, Cu and Cd into the solution and substantial amounts of particles and, hence, associated metals into overlying water. The concomitant changes in pH during oxidation/resuspension of sediment play a significant role in the metal release both to redox sensitive elements Fe and Mn and trace elements Zn, Cu and Cd. The concomitant change in DOC during oxidation/resuspension can also contribute to the increased mobility of study metals. The field study was coupled to intermittent operation of a hydropower plant. The mobility of the metals was higher under operation compared to non-operation and, thus, the potential impacts on dispersal of metal pollution to downstream aquatic environments. The sudden increase in water flow upon the hydropower plant upon shifts from inactive to active state could cause immediate release of particles and thus particulate metals in the overlying water. However, the magnitude and its integrated effects in fluxes of metals over the season call for further research. There is a need to further investigate the impacts of hydropower generation in a longer period of time and at a higher frequency of observations at the very start of the hydropower operation. The results from this multidisciplinary approach would give a basis for an optimal operation of the hydropower plant to minimize the metal pollution associated with the water flow. / <p>The series number is changed from 410 to 430 and the ISBN is changed from 978-91-85895-56-4 to 978-91-7393-926-3.</p>

The aim of this master’s thesis is the optimal design of swirl turbines for small water power plant. It is described a different possibilities of turbine‘s install for locality Vrchlabí. It presents a design of turbines and draft tubes. For the installation of turbines is computed theoretical production of annual electric energy. Furthermore it describes a design of supply channel and intake structure.

The development of hydroelectric power production and the damming of water courses that ensues causes a threat to the migration patterns of Atlantic salmon (Salmo salar), by altering their habitat and compromising river connectivity. Because the species’ survival heavily depends on the completion of their migration between rivers and oceans, the design of guidance structures that promote successful passages around dams is a critical goal. Physical structures have been used to steer downwards-migrating smolts through safe fishways but they have not always proven effective, both from an ecological and economical perspective. In this study, the potential of bubbles in guiding salmon trajectories around a hydropower dam was tested as an alternative to existing guiding systems. Here the hypotheses were: i) bubbles guide downstream-migrating smolts around dams; ii) the reaction of smolts to a bubble barrier is linked to their individual boldness; iii) bubbles have varying effects on different school sizes. The first and third hypotheses were tested in the field, by recording sonar footage at the entrance of a fishway, downstream of a bubble barrier. The second hypothesis was evaluated by conducting a scototaxis experiment and an assessment of the reaction of young salmon to bubbles in the laboratory. My analysis of the fish abundance data collected in the river confirmed the first and third hypotheses. In the field, the presence of a predator (Esox lucius) was revealed to be a more influential factor than bubbles in regulating the number of smolts steered towards the fishway, indicating that predators generated a larger anxiety-like response in smolts than bubbles. In the controlled laboratory setting, there was no significant correlation between anxiety-like behaviour and reaction to bubbles and the second hypothesis did not appear to be valid. Therefore, the cause of avoidance of the barrier remains unclear, but bubble barriers seem to be an efficient and cost-effective structure for guiding downstream-migrating salmon smolts.

Fragmentation of rivers due to the rapid expansion of hydropower plants is one of the major factors responsible for the decline in the Atlantic salmon (Salmo salar L.) in the Baltic Sea. Current methods to aid downstream migrating salmon smolt still struggle with effectively stopping the smolt from going through the hydropower turbines, by guiding them towards the available salmon ladders. A promising guiding method is using a barrier of bubbles which may serve as a non-intrusive alternative to conventional guiding structures. This study evaluated the risk of artificial selection caused using bubble barriers and compared the results with an earlier study.  The three hypotheses tested were: i) the salmon display a scototaxis behaviour related to their boldness, ii) temperature, and size of arena affect the scototaxis of the salmon, and iii) the salmons reaction to a bubble barrier is correlated to their boldness. The hypotheses were tested in a controlled laboratory setting by conducting three scototaxis tests and an experiment with several bubble barriers, where the reaction of salmon to bubbles could be assessed. There was significant positive correlation (r = 0,62 &amp; p = 0,012) between the boldness of an individual and the time it took to swim through the bubbles. Even though a significant difference in scototaxis as a result of lowered temperature were discovered, the difference was too small to have a noticeable effect on the overall results. A bubble barrier may therefore put artificial selection pressure on the salmon population.

The discharge through a river hydropower plant must be controlled such that the water level at a pre-specified point close to the facility is kept within given bounds. The controllers used today have a somewhat demanding tuning and often create too much amplified, unnatural discharge variations resulting in unsatisfactory control performance.This will affect both surrounding nature and imposing problems for river navigation. This thesis will present a new type of controller called Override Selector feedback Control that adds an estimator for the water levels and water flows in the up- and downriver for each hydropower plant on top of the old controller. The objective of the state feedback control is to keep the total variation of the water levels and the waterflows as small as possible. After the linear, discrete time model of the power plant cascade in a river derived from the Saint Venant equations have been developed, the new concept is evaluated. Both the water level sloshing and the amplification of the discharges compared to the structure used today is damped with the new control structure. Other advantages of the proposed controller is that it will be cost efficient to implement because of the add-on approach. This is seen as a very important factor while the actual benefit that can be made by improving the water level control is very limited and thereby also the will to make extensive control investments. The control structure will be easily implemented as the estimators only need the same input data as used today.

This diploma thesis deals with a study of a small hydropower plant in Osík on the Desná river. Part of the work is the calculation of the produced energy and the estimation of the return on investment.

<p>Projekti malih hidroelektrana, kao čistih izvora energije, treba da<br />doprinesu ekonomskom razvoju i razvoju društva u cjelini kroz održiv<br />razvoj, tako da je procesu planiranja projekata malih hidroelektrana<br />potrebno pristupiti s posebnom pažnjom. Rezultati ovog istraživanja<br />su pokazali da efektivno i efikasno upravljanje procesom planiranja<br />malih hidroelektrana doprinosi ostvarenju strateških ciljeva<br />upravljanja energetskim sistemom.</p> / <p>The projects concerned with small hydropower plants, which are considered<br />as a clean energy source, are expected to contribute to the economic aspect<br />of sustainable development of society as a whole. Therefore, the planning<br />process of these projects calls for particular attention. The results of the<br />research reveal that effective and efficient management of the planning<br />process of small hydropower plants contributes to the realization of strategic<br />goals set within energy system management.</p>

<p>The passage efficiency of downstream migrating brown trout (Salmo trutta) smolts past two hydropower plants in the River Emån, southeastern Sweden, was evaluated by telemetry. From 26 April to 17 May 2005, 40 wild brown trout smolts were radio-tagged, and their positions were recorded daily until 14 June. Approximately 45% of the individuals passed both power plants, and 15% made it to the sea, some 28 km downstream of the power plants. About 20% of the individuals ceased migrating, residing in a lotic habitat. Mortality due to predation was 33%, and the predation rate was higher in the power plant dams than it was downstream of the power plants. Turbine-induced mortality was greater in the upper power plant (40%) than in the lower one (13%). Fish that chose the alternative routes, through the gates, swam past the upper dam faster than fish that swam through the turbines. The results confirm previous work in the river, namely that measures need to be taken to improve passage efficiency past the power plants, particularly passage of the upper power plant. Such measures are of crucial importance if the nature-like bypass channels at the power plants in Finsjö are going to have any long-term effects on the brown trout population.</p> / <p>Passageeffektiviteten för nedströms vandrande havsöringssmolt (Salmo trutta) förbi två vattenkraftverk i Emån, i sydöstra Sverige, utvärderades med telemetri. Från 26 april till och med 17 maj 2005 märktes 40 vilda havsöringssmolt med radiosändare och de positionsbestämdes dagligen till och med 14 juni. Ungefär 45% av individerna passerade båda kraftverken, och 15% klarade sig till havet, cirka 28 km nedströms kraftverken. Omkring 20% av individerna avbröt vandringen och stannade i ett lotiskt habitat. Mortalitet på grund av predation uppgick till 33%, och predationshastigheten var högre i kraftverksdammarna än nedströms kraftverken. Den turbininducerade mortaliteten var högre i det övre kraftverket (40%) än i det nedre (13%). Det gick fortare att passera den övre kraftverksdammen för fisk som valde de alternativa rutterna, genom dammluckorna, jämfört med att passera genom turbinerna. Dessa resultat bekräftar tidigare studier i ån, nämligen att åtgärder krävs för att förbättra passageeffektiviteten förbi kraftverken, i synnerhet passagen av det övre kraftverket. Sådana åtgärder är av avgörande betydelse om de naturlika fiskvägarna vid kraftverken i Finsjö ska få några långsiktiga effekter på havsöringspopulationen.</p>