I Sverige finns i dagsläget närmare 10 000 dammar i våra vattendrag. Dammar som har varit en viktig del i den svenska historien men som nu utgör ett hot mot att uppsatta miljömål nås. Dammarna fragmenterar effektivt vattendragen då de utgör vandringshinder för fisk och andra vattenlevande organismer.  På senare tid har problemen som dessa dammar skapat blivit högre prioriterat av myndigheter och beslutsfattare. För att uppnå EU:s miljökvalitetsnormer krävs åtgärder vid i stort sett samtliga av Sveriges dammar. Vid vissa av dessa får naturen kompromissa och fiskvägar av olika slag tas i anspråk. Total utrivning av dammar är i Sverige fortfarande en ovanlig åtgärd men som börjar få spridning. Utrivning har visat sig vara det mest ekonomiska alternativet samtidigt som det bästa för miljön då det återställer inte bara konnektiviteten utan även vattendragets naturliga geomorfologiska processer och flödesdynamik.  I denna studie har konsekvenserna av en avsänkning av Dragby kvarndamm i Björklingeån undersökts. Studien har genomförts genom att sammanväga data från biotopkartering, elfiske samt en hydraulisk modellering i HEC-RAS. Den hydrauliska modelleringen visade hur flödesförhållanden och fallhöjd kommer fördela sig vid en potentiell avsänkning av Dragby kvarndamm. Tillsammans med övriga undersökningar kunde en sammanvävd bild av konsekvenserna av en avsänkning formas. Vid en avsänkning kommer vattenytan sänkas med 1-1,7 m och inga nya strömsträckor kommer att bildas. Trots detta tyder elfisket och biotopkarteringen på att en avsänkning kommer att gynna arter som till exempel lake. En avsänkning kan därav bidra till ökad ekologisk status i Björklingeån. / Sweden is a country revolved around different types of water. With a coastline stretching around a big part of the country. The Baltic Sea which is fed with so much fresh water that it classifies as a brackish sea. The fresh water from Sweden originates from almost 100 000 lakes and nearly 30 000 rivers and streams. However, these different waterways are heavily impacted by approximately 10 000 artificial dams. Dams that for example block fish from migrating to their spawning grounds.  In the last couple of years, the problems revolving around dams have been put higher up on the agenda of politicians and authorities. Significant efforts need to be made to be able to reach the goals of the European Water Framework Directive. Those efforts include building different kinds of fish passage solutions around dams, but also removing dams that no longer have a purpose. Dam removal is often the most cost-effective solution and at the same time the one with most ecological benefits.    In this study, the consequences of a removal of the Dragby mill dam have been investigated. The study have been done by collecting and combining data from habitat assessment, electrofishing and hydraulic modeling in HEC-RAS. The hydraulic modelling showed that the water level upstream of the dam will decrease with approximately 1-1.5 m if the dam is removed.  Simulated water velocities indicate that no rapids and stream habitat suitable for trout will immerse if the dam is to be removed. Nonetheless, the combined information suggests that a dam removal would most likely benefit other species such as the threatened burbot. Therefore, a removal of Dragby mill dam could result in a ecological boost for river Björklingeån.

The increasing interest in converting energy from renewable resources into electricity has led to an increase in research covering the field of marine current energy, mainly concerning tidal currents and in-stream tidal turbines. Tides have the advantage of being predictable decades ahead. However, the tidal resource is intermittent and experiences local variations that affect the power output from a conversion system. The variability is mainly due to four aspects: the tidal regime, the tidal cycle, bathymetry at the site and weather effects. Each potential site is unique, the velocity flow field at tidal sites is highly influenced by local bathymetry and turbulence. Hence, characterizing the resource requires careful investigations and providing high quality velocity data from measurement surveys is of great importance. In this thesis, measurements of flow velocities have been performed at three kinds of sites. A tidal site has been investigated for its resource potential in one of all of the numerous fjords in Norway. Measurements have been performed to map the spatial and temporal variability of the resource. Results show that currents in the order of 2 m/s are present in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus have potential for in-stream energy conversion. A model is proposed that predicts peak current speed from information on tidal range at the site. A corresponding model can be set up and implemented at other similar sites affected by tides, i.e. fjord inlets connecting the ocean to a fjord or a basin. A river site serves as an experimental site for a marine current energy converter that has been designed at Uppsala University and deployed in Dalälven, Söderfors. The flow rate at the site is regulated by an upstream hydrokinetic power plant nearby, making the site suitable for experiments on the performance of the vertical axis turbine in its natural environment. The turbine has been run in uniform flow and measurements have been performed to characterize the extent of the wake. An ocean current site was a target of investigation for its potential for providing utilizable renewable energy. A measurement campaign was conducted, mapping the flow both spatially and temporally. However, the site was shown to not be suitable for energy conversion using present technique. / Det ökande intresset för att producera elektricitet från förnybara energikällor har lett till en satsning på forskning inom området marin strömkraft, främst när det gäller tidvattenströmmar och tidvattenturbiner för fritt strömmande vatten. Tidvatten har fördelen att vara förutsägbar årtionden i förväg. Dock så är tidvattenresursen periodisk och varierar lokalt vilket påverkar effektuttaget från ett kraftverk. Variationerna beror till största delen på fyra aspekter: antal hög- och lågvatten per dag, tidvattencykeln, djupförhållanden på platsen (batymetri) och vädereffekter. Varje potentiell plats är unik, vattnets hastighetsfält påverkas i hög grad av lokal batymetri och turbulens. Därför krävs noggranna undersökningar för att karakterisera resursen. Att tillhandahålla hastighetsdata av hög kvalitet från mätningar är därför av stor betydelse. I denna avhandling har mätningar av flödeshastigheter utförts på tre typer av platser. En plats med tidvattenströmmar, belägen i en av alla fjordar längs Norges kust, har undersökts för sin resurspotential. Mätningar har utförts för att kartlägga resursens variation i både tid och rum. Resultaten visar att strömmar i storleksordningen 2 m/s återfinns i mitten av kanalen. Dessutom uppvisar flödet liten variation från huvudriktningen för både inkommande (flod) och utgående (ebb) flöden. Platsen har således potential för energiomvandling av fritt strömmande vatten. En modell föreslås som förutsäger strömmarnas maxhastighet från information om höjdskillnaden mellan ebb och flod och vice versa. En motsvarande modell kan ställas upp och användas på andra platser med liknande förhållanden som berörs av tidvatten, dvs. fjordinlopp som förbinder havet med en fjord eller en bassäng. En älv fungerar som en plats för experiment för ett marint strömkraftverk som har utvecklats vid Uppsala universitet och sjösatts i Dalälven, Söderfors. Flödeshastigheten på platsen regleras uppströms av ett närliggande vattenkraftverk, vilket gör platsen bra för att utföra experiment på prestandan av den vertikalaxlade turbinen i dess naturliga miljö. Turbinen har körts i jämnt flöde och mätningar har utförts för att karaktärisera vakens utbredning. En plats med havsströmmar var mål för en utredning av dess potential för att ge användbar förnybar energi. En mätningskampanj genomfördes för att kartlägga flödets variation både rumsligt och tidsmässigt. Emellertid visade sig platsen inte vara lämplig för energiomvandling utifrån användning av nuvarande teknik.

In many occupations, exposure to hand-transmitted vibration (HTV) over a prolonged period causes various disorders involving the vascular, neural and musculoskeletal systems, collectively known as the hand-arm vibration syndrome (HAVS). It is a complex and potentially disabling chronic disorder of the upper extremities, especially of the hands. Numbness, tingling, reduced tactile discrimination, and impaired manipulative dexterity are often reported by workers exposed to HTV. The precise pathophysiological mechanism responsible for vascular injuries in HAVS has not yet been fully clarified; it seems to be multifactorial and highly complex. Interaction of neural signals, hormones, mediators and changes in the blood vessel itself appear to contribute to the development of such vascular injuries. This study aims to assess the risk of the hand-transmitted vibration exposure during pneumatic impact wrench operation in a rock drill repair and maintenance workshop at a South African platinum mine. A total of 8 workers working on a day to day basis with impact wrenches were available for this study. For each of the workers a control (not exposed to vibration) was selected on the basis of gender, ethnic group, smoking habits, age and body mass index (BMI). Grip force, dexterity and hand-eye co-ordination were tested on the workers and control group before and after work. Finger systolic blood pressure (FSBP) was also measured after cold provocation of the worker and control groups. Results have shown astatistically significant difference between the two groups with respect coordination, dexterity and FSBP after cold provocation. Vibration measurements shows three workers had values above the suggested ELV of 5 m/s² for an eight hour A (8) workday. With regards to dexterity, workers were capable to manipulate small objects better with their dominant right (vibration exposed) hand after work than before work. In contrast, it seems that the number of pegs correctly inserted by the controls is not uniformly affected by their 8 hour workday. The worker group showed a greater grip force than that of the control group, both before and after work.There was a statistically significant difference between the control and worker group with respect to the number of mistakes during the mirror trace and the time to complete this test only for the right hand. The difference in FSBP after cold provocation between the control and worker group observed is of medium importance when compared with effect sizes, however, there was no statistical significant difference. In this study, it was very difficult to make valid conclusions due to the limitations of a small sample size. A longitudinal study should be conducted preferably using newly appointed workers with no prior exposure to vibration and a sufficient control group to eliminate the effect other confounding variables such as general working conditions. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013.

In many occupations, exposure to hand-transmitted vibration (HTV) over a prolonged period causes various disorders involving the vascular, neural and musculoskeletal systems, collectively known as the hand-arm vibration syndrome (HAVS). It is a complex and potentially disabling chronic disorder of the upper extremities, especially of the hands. Numbness, tingling, reduced tactile discrimination, and impaired manipulative dexterity are often reported by workers exposed to HTV. The precise pathophysiological mechanism responsible for vascular injuries in HAVS has not yet been fully clarified; it seems to be multifactorial and highly complex. Interaction of neural signals, hormones, mediators and changes in the blood vessel itself appear to contribute to the development of such vascular injuries. This study aims to assess the risk of the hand-transmitted vibration exposure during pneumatic impact wrench operation in a rock drill repair and maintenance workshop at a South African platinum mine. A total of 8 workers working on a day to day basis with impact wrenches were available for this study. For each of the workers a control (not exposed to vibration) was selected on the basis of gender, ethnic group, smoking habits, age and body mass index (BMI). Grip force, dexterity and hand-eye co-ordination were tested on the workers and control group before and after work. Finger systolic blood pressure (FSBP) was also measured after cold provocation of the worker and control groups. Results have shown astatistically significant difference between the two groups with respect coordination, dexterity and FSBP after cold provocation. Vibration measurements shows three workers had values above the suggested ELV of 5 m/s² for an eight hour A (8) workday. With regards to dexterity, workers were capable to manipulate small objects better with their dominant right (vibration exposed) hand after work than before work. In contrast, it seems that the number of pegs correctly inserted by the controls is not uniformly affected by their 8 hour workday. The worker group showed a greater grip force than that of the control group, both before and after work.There was a statistically significant difference between the control and worker group with respect to the number of mistakes during the mirror trace and the time to complete this test only for the right hand. The difference in FSBP after cold provocation between the control and worker group observed is of medium importance when compared with effect sizes, however, there was no statistical significant difference. In this study, it was very difficult to make valid conclusions due to the limitations of a small sample size. A longitudinal study should be conducted preferably using newly appointed workers with no prior exposure to vibration and a sufficient control group to eliminate the effect other confounding variables such as general working conditions. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013.

The trend of offshore wind power is bigger and bigger wind turbines. Turbines are now becoming so big that existing installation vessels no longer are feasible and new bigger installation vessels are needed. Ship owners hesitate to order new vessels worried that the rapid turbine growth will continue and make also the new vessels obsolete in a few years. This can create a bottleneck in the offshore wind market.   This thesis assignment attempts to develop a telescopic tower as an alternative way of installing offshore wind turbines. A telescopic tower can decrease overall height and COG during marine installation, giving opportunity to install the largest wind turbines also with existing vessel fleet.   The method for developing the telescopic tower is to first find the main problems and functions of the concept. A design basis based on a 12 MW reference wind turbine is developed. Based on this reference turbine different solutions to the main problems and functions are developed by creative thinking, literature research, modelling, calculations and analysis. A cost/benefit analysis is performed to investigate if there is any economic potential in the developed solution. To complete the study other installation methods and telescopic tower concepts are investigated for benchmark comparison.   The telescopic tower will have two sections. Shoulders are welded to the inner wall of the lower tower. The upper tower fit inside the lower tower and a telescopic mechanism is installed below to lift the assembly as the mechanism climb the shoulders of the lower tower. The telescopic mechanism works much like a pin and hole mechanism used for jack-up rigs. The pins engage/disengage with the shoulders by the movement of linear actuators. The vertical climbing motion is provided by hydraulic cylinders. The power source is an HPU placed on the wind turbine external platform.   To connect the upper and lower tower permanently a friction connection with long slotted holes is used. This connection is developed for assembly of onshore towers in an EU-sponsored project called Histwin. The walls of the lower and the upper tower overlap at the connection and are pressed together by pretensioned bolts to create a friction surface that hold the loads from the upper tower.   The conclusion is that the telescopic tower is technically feasible and can be installed by the existing installation vessel fleet. The economic feasibility is dependent on the specific project characteristics, but there are scenarios where the telescopic tower can have great economical upside.

I Sverige finns cirka 2000 vattenkraftverk men endast 10 procent har någon form av omlöp eller annan lösning (Risinger, 2012). Nya, strängare regler håller nu på att införas. Sedan 2014 finns en gemensam strategi från Energimyndigheten och Havs- och vattenmyndigheten för åtgärder i svensk vattenkraft (Risinger, 2014). En godkänd fiskväg är ett av kraven.Särskilt den småskaliga vattenkraften (energitillförsel under 10 MWh enligt Risinger (2012)) drabbas. Deras intäkter står många gånger i proportion till energiproduktionen och därmed saknas ofta de ekonomiska förutsättningarna för en fiskväg. Vidare kommer en del av vattnet, och därmed potentiella inkomster, att gå förlorade. Den här undersökningen syftar till att utröna vad ett omlöp får för konsekvenser i form av effektförluster. Det är naturligtvis omöjligt att komma fram till ett universellt svar. Istället mäts förlusterna hos ett specifikt mindre verk som redan har ett omlöp: Åby vattenkraftverk som ägs och drivs av Växjö kommun. Metoden som används är traversering i kombination med hydroskopisk flygel. Sedan tidigare finns beräknade värden från kommunen för flödet i omlöpet. Dessa jämförs med undersökningens uppmätta värden. Undersökningen visar att vid normalt vattenstånd (165,13 MÖH) flödar 167 ± 10 l/s vatten genom omlöpet. Detta är ett 70 l/s större flöde i jämförelse med kommunens beräknade värde. Förklaringar till den skillnaden ges av mätfel då djupet mättes och att inloppet hade byggts om mellan kommunens beräkningar och utförda mätningar. Även den formel som användes då de beräknade värdena togs fram föreslås som en tänkbar felkälla. 167 ± 10 l/s innebär ett bortfall om 4,2 ± 0,3 kW potentiell effekt. / There are around 2000 hydropower plants in Sweden, but only 10 percent of them has a bio channel, fishway or equivalent solution (Risinger 2012). New, more strict rules are now about to be introduced. Since 2014 there is a mutual strategy from the two Swedish authorities ”Energimyndigheten” and ”Havs- och vattenmyndigheten”, which demands multiple actions from Swedish hydropower. (Risinger, 2014). An approved fishway is one of these.The small-scale hydropower plants (plants who produce less than 10 MWh according to Risinger (2012)) are especially affected from this. Their income is proportional to their production and therefore they’ll usually lack the economical ability to build a fishway. Furthermore, a part of the streaming water (which otherwise would equal income) will get lost. This study aims to decide the loss of effect a fishway causes. Of course, it is impossible to derive a universal answer. Instead the losses are measured at a specific smaller plant that already has a fishway: Åby hydropower plant that is owned and operated by Växjö municipality. Method being used is traversing in combination with a turbine flow meter. There are already calculated flows made by the municipality. These values will be compared with the measured values. The study shows that at a normal water level (165,13 m.a.sl) 167 ± 10 l/s of water is streaming through the fishway. This is a 70 l/s bigger flow in comparison with the municipality’s calculations. An explanation to this difference is given by measurement errors when the depth was measured, that the intake had been modified between when the calculations was being made and when the study’s measurements took place. Also, the formula being used for the calculated values is proposed as a possible source of error. 167 ± 10 l/s will result in a loss of 4,2 ± 0,3 kW potential effect.

För att uppskatta influensområdet till följd av skyddsinfiltartion finns ett antal analytiska modeller att tillämpa. Dessa modeller tar hänsyn till parametrar så som hydraulisk konduktivitet och magasinkoefficient, men de följer också med en rad antaganden som i praktiken inte kan uppfyllas. En alternativ tillvägagång för att bestämma influensområdet är därför med hjälp av numeriska modeller, som i större grad kan göras platsspecifika. Numeriska modeller är till följd av detta mer tidskrävande och behöver mer indata. I denna studie undersöktes vilken metod som är bäst lämpad för att bestämma skyddsinfiltrationens influensområden för en fallstudie i Bromstens industriområde, belägen cirka 15 km nordväst om Stockholm centrum. Två numeriska modeller med varierande underlag av platsspecifika data utvecklades över områdets geologi och grundvattenmagasin för att kunna simulera grundvattennivåer med och utan infiltration. Utöver detta beräknades influensområdet med fyra analytiska modeller. Modellerna testades sedan utifrån olika scenarion, där såväl dataupplösning som den platsspecifika kännedomen över området stegvis ökades. Platsspecifika data tillkom till följd av geotekniska undersökningar och hydrogeologiska tester. Studien ämnar även att besvara vilken data som är av störst vikt för att bestämma influensområdet med de analytiska respektive numeriska modellerna samt vilka skillnader som uppstår mellan analytiskt beräknade influensområden och numeriskt simulerade influensområden. Resultaten visar att de numeriska modellerna i huvudsak är känsligast med avseende på den hydrauliska konduktiviteten, samt att den enklare numeriska modellen är känslig för magasinkoefficienten, något som indikerar att denna modell inte uppnår jämvikt i enlighet med vad som observerats i fält. Utöver detta stod det klart att vattenavgivningstalet inte hade någon nämnvärd inverkan på resultaten. Bland de analytiska modellerna råder den största känsligheten i magasinkoefficienten, följt av konduktiviteten. För Sichardts formel, som inte tar hänsyn till magasinkoefficienten var konduktiviteten den känsligaste parametern. Akvifärens mäktighet, vilken reviderades mellan scenario 2 och 3, hade ingen betydande inverkan på de analytiska modellerna. Vidare visade infiltrationstestet på stora skillnader i skyddsinfiltrationens influensområde med avseende på de olika modellerna och dataunderlaget. Den minsta avvikelsen mätt i residualer observerades för den komplexa numeriska modellen under scenario 4, vilket motsvarar det scenario då dataunderlaget var som störst. Trots att detta scenario tillsammans med modell anses vara det dyraste fallet, anses detta vara det bästa och samtidigt mest tillförlitligt metoden för att uppskatta skyddsinfiltrationens influensområde. / To evaluate the area of influence due to artificial infiltration several analytical models are available. Some of the parameters taken into account by these models are the hydraulic conductivity and storage coefficient, but with these models some assumptions, which in reality cannot be fulfilled, are made. An alternative approach to evaluate the area of influence is therefore with numerical models, which in a greater extent account for the site-specific conditions. Due to this, numerical models are more time consuming and require more input data. This project aims to investigate the most effective approaches to evaluate the area of influence due to artificial infiltration for a case study in Bromsten, located 15 kilometers northwest of Stockholm. Two numerical models, with different background data due to the extent of site knowledge, were developed to represent the site's geological settings and groundwater properties to simulate the groundwaterlevels with and without infiltration. Moreover the area of influence were calculated with four analytical models. All of the models were then applied on four different scenarios, in which the data resolution and the site knowledge increased. Site-specific data was added as a result of geological surveys and hydrogeological tests. The study also aims to answer which data is most important in order to determine the area of influence with analytical and numerical models and what differences there are between the analytical solutions compared with the numerical solutions. Among the methods investigated, constructing a more complex model with data from scenario 4, the scenario with the greatest data supply, resulted in the most reliable results and was therefore the best method and the method to choose for this case-study. Other results indicated that the numerical models first of all are sensitive to the conductivity and that the more simpel numerical model is sensitive to the storage coefficient as well. The last result shows that this model does not reach the steady state conditions as observed in field, which highlights the importance of goetechnical investigation for the numerical models. Moreover none of the numerical models were sensitive to the specific yield. Among the analytical models the storage coefficient was the most important followed by the conductivity. For one of the analytical models (Sichardts formula) the conductivity was the most sensitive parameter. The thickness of the aquifer had no significant impact on the analytical models.

In the pursuit of low-carbon, renewable energy sources one option with great potential in the UK is tidal energy. Specifically the proposed construction of the Swansea Bay Tidal Lagoon (SBTL) in South Wales has become one such discussed option. With a potential net annual output of 400 GWh and a 120-year lifetime the scheme represents a long-term and large-scale electricity production option. An assessment of carbon emissions and embodied energy (EE) of the lagoon’s life cycle was carried out. Total lifetime carbon emissions for the SBTL are in the region of 470,000 tCO2e and EE was found to be around 7,800 TJ. The assessment shows that the SBTL has significantly lower emissions per year than the existing National Grid mix and with emissions of around 0.01 kgCO2e/KWh is significantly lower than the UK emissions target of 0.07 kgCO2e/KWh. Energy payback of the SBTL was found to be in the region of 5.5 years. The use of dredged ballast infill sourced from within the area of the lagoon plays an important role in keeping emissions and energy use low; and is a key consideration when planning future tidal lagoon structures.

The main objective of wave energy converters (WECs) is to ensure reliable electricity production at a competitive cost. Two challenges to achieving this are ensuring an efficient energy conversion and offshore survivability.         This thesis work is structured in three different sections: Control and maximum power optimization, forces and dynamics analysis in extreme wave conditions, and statistical modeling of extreme loads in reliability analysis.        The need for prediction and future knowledge of waves and wave forces is essential due to the non-causality of the optimal velocity relation for wave energy converters. Using generic concepts and modes of motion, the sensitivity of the prediction horizon to various parameters encountered in a real system is elaborated. The results show that through a realistic assumption of the dissipative losses, only a few seconds to about half a wave cycle is sufficient to predict the required future knowledge for the aim of maximizing the power absorption.          The results of a 1:30 scaled wave tank experiment are used to assess the line force and dynamic behaviour of a WEC during extreme wave events. Within the comparison of different wave type representations, i.e. irregular, regular and focused waves, of the same sea state, the results show that not all the wave types deliver the same maximum line forces. As a strategy of mitigating the line forces during extreme wave events, changing the power take-off (PTO) damping may be employed. With consideration of the whole PTO range, the results indicate an optimum damping value for each sea state in which the smallest maximum line force is obtained. Although wave breaking slamming and end-stop spring compression lead to high peak line forces, it is possible that they level out due to the overtopping effect. Waves with a long wavelength result in large surge motion and consequently higher and more damaging forces.         On the investigation of reliability assessment of the wave energy converter systems, computing the return period of the extreme forces is crucial. Using force measurement force data gathered at the west coast of Sweden, the extreme forces are statistically modelled with the peak-over-threshold method. Then, the return level of the extreme forces over 20 years for the calm season of the year is computed.