This master thesis studies the flexibility of Swedish power system. Because of the increase of fuel price and the environmental issues, renewable energy plays an increasingly important role. Sweden parliament has a planning frame of 30 TWh wind power energy per year in 2020. Wind power generation is largely dependent of wind speed. Since wind speed varies all the time and is hard to be predicted, the introduction of wind power will cause variation of power generation which needs to be balanced. Therefore, it is very important to study the regulation capacity of the power system in order to balance wind power. In Sweden, it is hydropower and thermal power that plays the role as balancing power. In earlier studies at Department of Electric Power Systems KTH, a model has been built to examine the flexibility of Swedish hydropower system. The aim of this thesis is to further develop this original model. In the improved model, the flexibility of thermal power in Sweden is included. Moreover, the improved model further considers the future value of stored water and the impact of delayed running water released from the upstream power plants at the end of simulated week. The whole model is a large short-time planning problem and the objective of this model is to maximize the profits. In this thesis, the profit is expressed as the future value of hydropower minus the generation cost of thermal unit. Besides, the profit also includes the income and the cost for the trading energy. The improved model is built as an optimization problem in GAMS. The time step is one hour and the time span of each simulation is one week. The load consumption and wind power production in each area are given as time series. The constraints considered in this model include the generation limitations, operational constraints of thermal power plants, hydrological coupling of hydropower plants, load balance in each bidding area and transmission capacity. Several case studies are performed in this thesis. Two models, both original model and improved model, will be tested. To find out how large the regulation capacity the Swedish power system has, four different expansion levels of wind power: 0 MW, 4000 MW, 8000 MW and 12000 MW are introduced. The information regarding hydropower is obtained from statistic data in 2009 and the wind power data for each week is coming from scaling the data in earlier studies. The operational constraints of thermal power plants are based on the statistics data from 2008 to 2012. The main finding from these case studies is that spillage will not increase when more wind power is introduced to the system but only increase when the export capacity is reached and the surplus power cannot be exported to other countries. Therefore, it can be concluded that the Swedish power system has good possibilities to balance large amounts of wind power. However, some simplifications and assumptions are made when the model is built, which will give rise to some inaccuracy to the result. Therefore, in the end of this thesis, some future studies are suggested to further improve this model. / I detta examensarbete studeras flexibiliteten i det svenska elsystemet. På grund av ökande bränslepriser och miljöproblem kommer betydelsen av förnybar energi att öka. Den svenska riksdagen har beslutat om ett planeringsmål på 30 TWh vindkraft till år 2020. Elproduktionen från vindkraft beror på vindhastigheten. Eftersom vindhastigheten varierar hela tiden och är svår att förutsäga, medför en ökning av vindkraften variationer i elproduktionen som måste balanseras. Därför är det mycket viktigt att studera elsystemets förmåga att balansera vindkraft. I Sverige sköts denna balansering av vattenkraft och termiska kraftverk. I tidigare studier vid Avdelningen för elektriska energisystem, KTH, har en modell utvecklats för att studera flexibiliteten i det svenska vattenkraftsystemet. Målsättningen med detta arbete är att vidareutveckla den ursprungliga modellen. I den förbättrade modellen inkluderas flexibiliteten i de svenska termiska kraftverken. Dessutom tar den förbättrade modellen hänsyn till värdet av sparat vatten och inverkan av vatten som rinner mellan två kraftverk i slutet av den simulerade veckan. Hela modellen är att stort kotttidsplaneringsproblem och målfunktionen i denna modell är att maximera vinsten. I det här arbetet uttrycks vinsten som värdet av sparat vatten minus produktionskostnaderna i de termiska kraftverken. Dessutom ingår inkomster och konstnader för elhandel. Den förbättrade modellen är uppbyggd som ett optimeringsproblem i GAMS. Tidssteget är en timme och varje simulering omfattar en vecka. Lasten och vindkraftproduktionen i varje område är givna som tidsserier. De bivillkor som ingår i denna modell är begränsningar i elproduktion, driftbegränsningar i termiska kraftverk, hydrologisk koppling mellan vattenkraftverk, lastbalans i varje område och transmissionsbegränsningar. Flera fallstudier genomförs. Två modeller, den ursprungliga och den förbättrade, testas. För att undersöka hur stor balanseringsförmåga det svenska elsystemet har undersöks fyra olika nivåer på vindkraftsutbyggnad: 0 MW, 4000 MW, 8000 MW och 12000 MW. Data för vattenkraften erhålls från statistik för 2009 och vindkraftsdata är skalade data från tidigare studier. Driftbegränsningarna i termiska kraftverk baseras på statistik från 2008 till 2012. Den viktigaste slutsatsen från dessa studier är att spillet inte ökar då mer vindkraft introduceras i systemet, såvida man inte når gränsen för exportkapaciteten och det inte är möjligt att exportera överskottsproduktion till andra länder. Därför kan man dra slutsatsen att det svenska elsystemet har en god förmåga att balansera stora volymer vindkraft. Modellen bygger dock på vissa förenklingar och antaganden, vilket medför en viss osäkerhet i resultaten. Därför föreslås i slutet av rapporten några framtida studier för att förbättra modellen ytterligare.

Recently it has become more common in the construction of large dams to reuse diversion tunnels as flood discharge tunnels in the final structure. These tunnels handle large flows with the characteristics of open channel flow. When such large hydrological forces act upon a structure there are several problems to be expected. One of these is the occurrence of cavitation, which could have potential hazardous erosion as a consequence. Cavitation is the formation and collapse of bubbles that create a shockwave strong enough to erode the underlying material. The Baihetan dam is one of the largest hydro power projects in China at present. It has three discharge tunnels that all run the risk of developing cavitation damages. By modelling one of the tunnels using Computational Fluid Dynamics (CFD) it is possible to investigate where in the tunnel structure cavitation is likely to occur. This degree project assesses the risk of cavitation erosion in the Baihetan tunnel using the static pressure distribution, the velocity distribution and modern cavitation theory. Several modifications of the tunnel – including alterations in the gradient and construction parameters – are simulated in order to investigate if changes in the design can mitigate the cavitation problem. None of the analysed modifications completely eliminate the problem and aeration is recommended to counteract the problem. This study indicates where cavitation might be a problem in the Baihetan tunnel and can be used as a basis for further research.

In these days environmental issues are critical. Environmental concerns mainly rise from energy productions. Fortunately Ethiopia is trying to use renewable energy sources as a means for electrical power production and it is a great start for a long, tiresome green energy journey. The basic job to be done in green energy sectors is to maximize the capacity of renewable technologies to fulfil the best efficiency.  Intermittent nature of the energy production and their inefficiency to meet peak load demands are the basic problems in renewable energy sectors.   Ethiopia’s electrical power production is mainly dependent on hydropower; according to latest data from EEPCO hydro covers 88% of the total production. There are two major nature of this power plant; since the working medium is water it is mainly dependent on the nature of the seasons and secondly it rarely meets peak load demands. After the erection of the power plant the energy production is not time dependent; it can produce power continuously; but the consumption is time dependent which is defined as peak hours and off-peak hours. There is excess load in time of off-peak hours and scarcity in peak hours. So this work can help to maximize the capacity of the water for production by using technological advancements to produce lot of energy in almost full capacity throughout the year to full fill the need of our country. Tana Beles hydropower plant is the largest hydropower plant which starts to work in May, 2010 with an investment cost of $500 million and capacity of 460 MW. The project is planted in Amhara region using the water source of Lake Tana. To make this large and very necessary renewable energy resource sustainable using energy storage system will be vital. This study will figure out a pumped storage system for the hydropower plant for additional power production and for the sustainability of the water resource.    Pumped storage system is the only viable, large-scale resource that is being broadly utilized today for storing energy, and it offers the best option available for harnessing off-peak generation from renewable sources. The contributions of pumped storage hydro to our nation’s transmission grid by providing stability services, storage capacity needs, and expanding the green job market are considerable today.   The high energy demand of the pump will be considered to be covered using the excess electrical power production during night or weekends and if the resource is available using wind solar PV hybrid systems.   The author will try to assess the technology not only for other mini hydro power plants but also for irrigation and other purposes merely in Amhara region, Ethiopia. The feasibility of the system will be considered technically and economically for the hydropower plant.

Over the last decades, the frequency on the Nordic electrical power grid has deteriorated. Therefore, new stricter requirements are developed for the hydropower delivering regulating active power on the Frequency Containment Reserve market (FCR). This thesis aims to investigate the possibility of modeling two double-regulated hydropower plants, referred to as Unit 1 and 2, to evaluate their compliance with the new FCR-requirements.  By modeling the hydropower plants, the first goal was to find a model structure that captures the essential dynamics of the systems. A second goal was to evaluate whether the two units currently fulfill the new FCR-requirements, and investigate how the turbine governors’ settings could be optimized to fulfill the new requirements. Data obtained from FCR-tests was used in MATLAB to evaluate the two stations’ dynamic stability and performance requirements. Through system identification in MATLAB, grey-box modeling was used to create linear and non-linear turbine and waterways models for Unit 1 and Unit 2. The non-linear turbine and waterways models were implemented in Simulink, together with corresponding turbine governors, to find optimal parameter settings to fulfill the FCR-requirements.  The evaluation of the new FCR-requirements shows that none of the two units fulfills the dynamic stability requirement. However, Unit 1 fulfills the performance requirement. The results imply that double-regulated turbines will most likely have difficulties fulfilling the new requirements, which will cause major consequences in improving the frequency regulation quality. The results from the grey-box modeling present that the linear models are not validated with the step response data, due to not capturing the system dynamics when compared with provided data from the units. On the other hand, the non-linear models are validated with step response data as the model captures the system dynamics more accurately. However, the non- linear Simulink models cannot capture the dynamics of the hydropower systems for sinusoidal signals with varying frequencies which are used in the new FCR-requirement test. Consequently, the thesis has no result of the optimal parameter setting of the turbine governors to fulfill the new FCR-requirements. In conclusion, the grey-box models, with the level of detail presented in this thesis, are inadequate in capturing the system’s dynamics to evaluate the new FCR-requirements. Thus, the thesis contributes to filling a knowledge gap within the area of modeling for frequency regulation.

The 34 silos at Jarlaberg today contain crude oil but after the lease of land expires at 2036 are refurbished and remade to hold 2 500 000 m3 of water from Stockholm archipelago. Sharing the industrial plot of the reworked silos are 13 buildings with 2000 households between them. At the shores of the rocky hills is a new landmark with two swirling metal structures reflecting daylight and the shining light from the structure bellow. The building contains two hydro turbines, with the glass roofs and metal vortexes above, a landmark to be seen from both the built plateaus above and the opposite side shores as a celebration of the renewable energy progress of 2030-2050.  The project started as a look at industrial architecture and its relation to city spaces. Specifically the implementation of a stored capacity hydropower solution if placed close to major city centers which demanding more, renewable energy. At first the ambition was to integrate a series of turbines to the new Slussen water outlet from Mälaren to Saltsjön but after further readings the theme of letting the industries society’s development  is dependent upon be a part in planning the cities expansion. To join a industrial function to a housing plan would make a large impact on the urban space in-between the two. To both make a bond but also show the story of the production of energy the project provides. The sides of the silos have been fitted with a series of stepped gradients for seating and to access the top of the water reservoirs. The bottom of the gradients connect to the urban spaces such as parks and squares. Providing both a sun step for seating and meeting spaces close to areas of activity.

Hydropower is a fundamental pillar in the Swedish energy system and accounts for a large part of the Swedish electricity production. The regulation power is also essential for balancing the grid load.  Fortum is one of the leading energy companies within hydropower and Klarälven is a river with high importance, where Fortum owns and operates nine powerplants. These power plants constitute a barrier for the wild salmonids in Klarälven, which need to migrate upstream to reach their spawning area. Since the 1930s, the spawning salmonids have been trapped and transported upstream by lorry. After the spawning period, the smolts and kelts, i.e. the juvenile and spawned salmonids, have to migrate downstream. Due to the lack of fishways, they are forced to pass the eight remaining power plants. This, together with predation, entails a high mortality rate. Two independently performed studies indicates on survival rates of 16 % and 30 %. To stabilize the wild salmonid population, the downstream survival must increase, and a proposed solution is to implement a downstream trap-and-transport solution. This trap implementation could be a step towards the environmental adaptation of hydropower and a part of the action plan proposed in June 2016, during the Agreement on Swedish energy policy. To find the most cost-beneficial environmental measure, a socio-economic assessment method can be used. A Cost-Benefit Analysis (CBA) is a commonly used socio-economic method, which evaluates the benefits and costs during the entire project lifetime. Energiforsk has, within the project FRAM-KLIV, developed a CBA tool that aims to simplify the socio-economic evaluation. The purpose of this thesis was to investigate whether the CBA tool can be used in future permit processes to prioritize between different project proposals to find the most beneficial environmental improvements. In order to evaluate the tool, it was to be applied on the trap-and-transport project in Edsforsen to evaluate the possibility of a socio-economic profitability. Also, the concepts and theory behind CBA was to be analysed and the suitability of translating environmental consequences into monetary values was to be evaluated. In the analysis of Edsforsen, 13 scenarios were developed. The first scenario served as a basis for the other scenarios, which were created as a sensitivity analysis. The result of the CBA showed a large socio-economic benefit and the most important parameter was identified as people’s willingness to pay for an increase of the wild salmonid stock in Klarälven. In the CBA, this parameter had a high uncertainty, as it was based on a survey performed for another project in another part of Sweden. It was found that in order for the socio-economic result to be positive, all households in Sweden must be willing to pay at least 35 SEK. As a complement to the CBA result, an evaluation regarding the marginal cost per fish was performed and an interval of 50-580 SEK per smolt was obtained. However, the calculations were based on several uncertainties and the interval should therefore be interpreted as a guideline rather than a precise result. It was concluded that in situations when a socio-economic analysis is required, and when it is possible to express consequences in monetary values, the method of CBA is appropriate. It is also a suitable methodology for evaluations of large projects, as it provides a comprehensible overview of the costs and the benefits. Despite the criticism directed towards CBA regarding uncertainties and its anthropogenic perspective, it could be concluded that using CBA as a socio-economic assessment method provides a perspicuous and quantitative result. Thus, the usage of CBA in prioritization processes of different environmental measures can be highly useful. Energiforsk’s CBA tool provides a framework with guidelines that can be highly useful and accelerate the analysis process. However, the performance of the tool version used in this thesis was not fully satisfactory due to a few malfunctions. The tool is still under development and it is likely that these errors will be adjusted in future versions. If the malfunctions in the tool would be adjusted, it could become useful for authorities, companies and other actors that wants to evaluate hydropower related environmental measures or when prioritizing between different project proposals to find the most beneficial environmental improvements in future permit processes.

No description available.

The energy produced by the flow of water is known as hydropower. It is an easily accessible and available source of energy in large quantity in the form of, rivers, lakes, streams and runoffs around the world. Hydropower is dependent upon hydrological cycle hence; this beneficial characteristic of hydropower makes it a renewable source of energy. Hydropower is free from poisonous emission; therefore, it is considered as a safer and pollution free source of energy. It is usually used to develop electricity from generators. These generators are connected to the hydro turbines by means of shaft. The electricity produced from hydropower is stable and steady because of its higher capacity, thus it can be a suitable source to work as base-load and used to balance the power fluctuations caused by varying loads. The hydropower can also be accommodated with different sources such as solar and wind system. This way of power sharing needs quick regulation as the deviation in the power grid changes rapidly. To fulfil this power demand with higher stability prompted to the development of modern turbines with more efficient, reliable and robust design.   To achieve the above target, it is of prime importance to improve efficiency of hydro turbine. Nevertheless, many methods are in practice for improvement for efficiency of the turbine; though one of the prime elements which influence the turbine efficiency is surface roughness. The effect of surface roughness differs for different turbine components like stay vanes, guide vanes, runner, draft tube and spiral casing.   The main purpose of this thesis is to examine the effect of surface roughness for hydro turbine step-up efficiency. It is based on reduced scale model to prototype conversion method. For this purpose, IEC_62097 has provided an excel sheet as an attachment for calculation. There has been always a need to perform model test, since performing test on the prototype itself is very accurate, and calculations too, do not yield reliable results. Therefore, the model to prototype conversion method is considered a better solution.   A sensitivity analysis is conducted on a Kaplan turbine situated at the Granfors power station located along the Skellefteå river about 30 km from the city of Skellefteå. The results obtained after applying the latest step-up expressions are described and presented. These outcomes have shown significant positive impact on the hydro turbine efficiency improvement, which are presented in graphs.   The most significant variations of step-up efficiency against surface roughness were observed in the runner part of the turbine. This specific characteristic makes it evident that more focus and test should be conducted on this part to improve efficiency.

Vissa vattenkraftverk drivs med korttidsreglering som möjliggör snabb anpassning av elproduktion, vilket sker genom hastiga förändringar i vattenflöde. Flera olika typer av organismer påverkas negativt av korttidsreglering, till exempel fiskar. En möjlig konsekvens är strandning, vilket innebär att fiskar hamnar i torrlagt substrat eller annat ogynnsamt habitat. Risken för strandning påverkas av flera faktorer. I denna studie undersöktes hur strandningsrisk hos öringyngel (Salmo trutta) påverkas av tillgång till skydd och ljusförhållande, där prediktionerna var att strandningsrisken skulle vara större vid tillgång till skydd och i mörker. Dessa två faktorer testades i en 2x2 design. Det fanns en tendens till en större andel strandade yngel vid tillgång till skydd (48 ± 8,2 %) jämfört med när det inte fanns skydd (35,7 ± 23,7 %) och en större andel strandade vid ljusa förhållanden (50,2 ± 16 %) än i mörker (33,4 ± 17,3 %). Påverkan av tillgång till skydd på strandningsrisk var inte annorlunda vid de olika ljusförhållandena. Utifrån dessa resultat är rekommendationen för att minska strandningsrisken hos öringyngel att flödesreglering genomförs i mörker och att bottenstrukturen beaktas, vilket måste göras i varje enskilt fall. / Some hydropower stations use hydropeaking to be able to swiftly adjust electricity production, which is done through rapid alterations in water flow. Several types of organisms are negatively affected by hydropeaking, including fishes. One possible consequence of hydropeaking is stranding, which occurs when fish are separated from the water body and end up in dewatered substrate. The risk of stranding is influenced by several factors. The aim of this study was to investigate how stranding risk in brown trout fry (Salmo trutta) is affected by shelter availability and light conditions. The predictions were that stranding risk would be higher in conditions with available shelters and in darkness. The two factors were tested in a 2x2-design. There was a tendency for stranding rate to be higher when shelters were available (48 ± 8.2 %) compared to when there were none (35.7 ± 23.7 %), and stranding rate was higher in light (50.2 ± 16 %) than in darkness (33.4 ± 17.3 %). The effect of shelter availability on stranding risk did not differ between the two light treatments. Based on these results, in order to reduce stranding risk in brown trout fry the recommendation is that flow regulation should be carried out in darkness and that the bottom structure should be considered, which must be done on a case-by-case basis.

By using the rotor dynamic capabilities of Simcenter Nastran Rotordynamics, an eigenvalue analysis of 3D-finite element models of the Jeffcott rotor and the overhung rotor were conducted and compared to the results with beam-based, lumped parameter models. The first two critical speeds of the Jeffcott rotor were estimated with variations of 3.9 and 6.4%. The first three critical speeds of the overhung rotor were estimated with 8.5, 6.7 and 6.5% variations, respectively. The Jeffcott rotor was also analysed with different element configurations: Solid elements, axisymmetric Fourier elements, beam/solids and all beam elements. The Fourier elements were the most appropriate option for axisymmetric rotors regarding computational time and accuracy. Tilting pad journal bearings were simulated and validated against data from Vattenfall's facilities in Älvkarleby, where a vertical rotor is connected to two four-pad tilting pad journal bearings. The bearing formulation was defined in a Fortran based subroutine, which acquires the rotor's speed and position to supply a bearing load vector in Simcenter Nastran's transient solver. The experimental rig was also modelled to include the rotor/stator interaction. The force and displacement orbits at the bearings were replicated adequately concerning experimental data, where a maximum deviation of 20.8% and 9.8% were observed for the forces in x and y-directions.  A 3D-finite element model and a beam based finite element model were compared for an actual hydropower unit, which aimed to investigate the mode extraction procedure and how high mass, elastic rotor components influence the system's dynamics. Consistent rotor modes were identified at frequencies within 15% deviation, where the maximum deviation occurred in the upper range frequency pairs. Convergence between the models was observed for the static, lower range frequencies when considering a rigid generator rotor in the 3D finite element model. The outcome is consistent with the model assumptions and underlines that the beam based model cannot capture specific contributions from elastic rotor components. 3D-finite element analysis is a viable option when considering non-axisymmetric and complex rotors. High mass, non-rigid components must be analysed  in this manner as their dynamic contributions may not be captured with other approaches. Intricate and non-rigid supporting structures are also suitable for 3D modelling to properly reflect the stator-rotor interaction. It is a delicate matter to pinpoint when these conditions occur, and modelling decisions must be therefore be substantiated by simulations and experimental validation.