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  • 1.
    Ahlgren, Fredrik
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Waste heat recovery in a cruise vessel2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In three studies of a cruise ship the author has investigated waste heat recovery (WHR)from exhaust gases using an organic Rankine cycle (ORC), and also mapped the energyand exergy flows within the ship. Data were collected from the ship’s machinerysystem for a total extent of one year, and this data were used for simulations andenergy calculations. An off-design analysis was made and an ORC was simulated andoptimised with regards to the ship’s operating conditions. The ORC working fluid wasoptimised in terms for maximum electrical production in the off-design condition. Theoff-design analysis showed that the ship speed and power consumption was far fromits original design. The results indicate that there is a potential for significant savingsby using an organic Rankine cycle for waste heat recovery. The energy and exergyanalysis gave a better understanding of the energy flows and showed that the singlelargest exergy destruction occurs in the ship’s diesel engines.

  • 2.
    Ahlgren, Fredrik
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Mondejar, Maria E.
    Lund University.
    Genrup, Magnus
    Lund University.
    Thern, Magnus
    Lund University.
    Waste Heat Recovery in a Cruise Vessel in the Baltic Sea by Using an Organic Rankine Cycle: A Case Study2015In: ASME Turbo Expo 2015: Turbine Technical Conference and Exposition: Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration, Montreal, Quebec, Canada, June 15–19, 2015, ASME Press, 2015, Vol. 3, 43392-43416 p., V003T06A018Conference paper (Refereed)
    Abstract [en]

    Maritime transportation is a significant contributor to SOx, NOx and particle matter emissions, even though it has a quite low CO2 impact. New regulations are being enforced in special areas that limit the amount of emissions from the ships. This fact, together with the high fuel prices, is driving the marine industry towards the improvement of the energy efficiency of current ship engines and the reduction of their energy demand. Although more sophisticated and complex engine designs can improve significantly the efficiency of the energy systems in ships, waste heat recovery arises as the most influent technique for the reduction of the energy consumption. In this sense, it is estimated that around 50% of the total energy from the fuel consumed in a ship is wasted and rejected in fluid and exhaust gas streams. The primary heat sources for waste heat recovery are the engine exhaust and the engine coolant. In this work, we present a study on the integration of an organic Rankine cycle (ORC) in an existing ship, for the recovery of the main and auxiliary engines exhaust heat. Experimental data from the operating conditions of the engines on the M/S Birka Stockholm cruise ship were logged during a port-to-port cruise from Stockholm to Mariehamn over a period of time close to one month. The ship has four main engines Wärtsilä 5850 kW for propulsion, and four auxiliary engines 2760 kW used for electrical consumers. A number of six load conditions were identified depending on the vessel speed. The speed range from 12–14 knots was considered as the design condition, as it was present during more than 34% of the time. In this study, the average values of the engines exhaust temperatures and mass flow rates, for each load case, were used as inputs for a model of an ORC. The main parameters of the ORC, including working fluid and turbine configuration, were optimized based on the criteria of maximum net power output and compactness of the installation components. Results from the study showed that an ORC with internal regeneration using benzene would yield the greatest average net power output over the operating time. For this situation, the power production of the ORC would represent about 22% of the total electricity consumption on board. These data confirmed the ORC as a feasible and promising technology for the reduction of fuel consumption and CO2 emissions of existing ships.

  • 3.
    Ahlgren, Fredrik
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Mondejar, Maria E.
    Lund University.
    Genrup, Magnus
    Lund University.
    Thern, Marcus
    Lund University.
    Waste Heat Recovery in a Cruise Vessel in the Baltic Sea by Using an Organic Rankine Cycle: A Case Study2016In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, no 1, 011702Article in journal (Refereed)
    Abstract [en]

    Maritime transportation is a significant contributor to SOx,NOx, and particle matter (PM) emissions, and to a lesser extent, of CO2. Recently, new regulations are being enforced in special geographical areas to limit the amount of emissions from the ships. This fact, together with the high fuel prices, is driving the marine industry toward the improvement of the energy efficiency of ships. Although more sophisticated and complex engine designs can improve significantly of the energy systems on ships, waste heat recovery arises as the most effective technique for the reduction of the energy consump- tion. In this sense, it is estimated that around 50% of the total energy from the fuel con- sumed in a ship is wasted and rejected through liquid and gas streams. The primary heat sources for waste heat recovery are the engine exhaust and coolant. In this work, we present a study on the integration of an organic Rankine cycle (ORC) in an existing ship, for the recovery of the main and auxiliary engines (AE) exhaust heat. Experimental data from the engines on the cruise ship M/S Birka Stockholm were logged during a port-to- port cruise from Stockholm to Mariehamn, over a period of 4 weeks. The ship has four main engines (ME) W€artsil€ a 5850kW for propulsion, and four AE 2760kW which areused for electrical generation. Six engine load conditions were identified depending on the ship’s speed. The speed range from 12 to 14 kn was considered as the design condi- tion for the ORC, as it was present during more than 34% of the time. In this study, the average values of the engines exhaust temperatures and mass flow rates, for each load case, were used as inputs for a model of an ORC. The main parameters of the ORC, including working fluid and turbine configuration, were optimized based on the criteria of maximum net power output and compactness of the installation components. Results from the study showed that an ORC with internal regeneration using benzene as working fluid would yield the greatest average net power output over the operating time. For this situation, the power production of the ORC would represent about 22% of the total elec- tricity consumption on board. These data confirmed the ORC as a feasible and promisingtechnology for the reduction of fuel consumption and CO2 emissions of existing ships.

  • 4.
    Amanda, Holmkvist
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics, Byggteknik.
    Inverkan av torktemperatur vid vattenmättning av bruk och betong: Bestämmning av vattenmättnadsgrad och hydraulisk konduktivitet2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Today, there is uncertainty about how much the results differ when drying concrete

    at 20, 50 and 105 °C prior to saturation of concrete in order to determine the

    degree of saturation and hydraulic conductivity. Micro-cracks occur when concrete is

    dried at higher temperatures and causes increased hydraulic conductivity. Further, the

    concrete is believed not to be completely saturated if not all the physically bound

    water, so called free water, has been dried out prior to saturation.

    This thesis compares the effect of three different drying temperatures on the

    possibility to saturate concrete with water. The work was conducted at Vattenfall’s

    concrete laboratory in Älvkarleby. The three drying temperatures were +20 °C

    (room temperature), 50 °C and +105 °C. The objective was to determine if

    differences on the degree of saturation and hydraulic conductivity were non-existent

    or negligible. Vacuum saturation after drying at 105 °C is considered to be complete.

    The results after drying at 20 °C and 50 °C were compared to those after drying at

    105 °C. The results of the tests indicate that the concrete should be dried at +105°C

    prior to saturation with water. Then the risk of frost damage to concrete in hydro

    power structures can be assessed.

    How determination of the hydraulic conductivity is affected by the drying

    temperature gave more vague and dubious results. All specimens showed a maximum

    hydraulic conductivity after drying at 50 °C, not after 105 °C as expected. It was

    believed that the hydraulic conductivity theoretically would increase because of

    (more) micro-cracks when being dried at 105 °C. Results from the concrete with vct

    1.0 gave results that indicated that the specimens had been damaged by method 1. To

    sum up, the results of the tests indicate that further studies on the effects of drying

    temperatures should be made.

  • 5.
    Axelsson, Unnar
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Folkesson, John
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS. KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Underwater feature extraction and pillar mapping2015Report (Other academic)
    Abstract [en]

    A mechanicaly scanned imaging sonar, MSIS, pro-duces a 2D image of the range and bearing of return intensities.The pattern produced in this image depends on the envior-mental feature that caused it. These features are very usefulfor underwater navigation but the inverse mapping of sonarimage pattern to environmental feature can be ambiguous. Weinvestigate problems associated with using MSIS for navigation.In particular we show that support vector machines can be usedto classify the existance and types of feature in a sonar image.We develop a sonar processing pipleline that can be used fornavigation. This is tested on two sonar datasets collected fromROV’s. 1

  • 6.
    Ayotte, John
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control.
    Dynamic positioning of a semi-submersible, multi-turbine wind power platform2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a growing market for offshore wind power has created a niche for deep-water installations, offshore floating wind solutions have become more and more viable as a renewable energy source. This technology is currently in development and as with many new technologies, many traditional design methods are found lacking. In the multi-turbine platform design investigated, turbine units are placed closely together to conserve material use and reduce cost, however with such tightly spaced turbines; wake interaction poses a threat to the productivity and the lifespan of the installation. In order to fully capitalize on the substantial increase in available wind energy far at sea, it is important that these floating parks operate in an optimal way. The platform investigated in this report sports 3, 6MW turbines which must be positioned such that wake interference is minimized; the platform must always bear a windward heading. 

    Maneuvering ocean going vessels has been practiced using automated dynamic positioning systems in the gas and oil industry for over 50 years, often employing submerged thrusters as a source of propulsion. These systems are mostly diesel powered and require extra operational maintenance, which would otherwise increase the cost and complexity of a floating wind farm. In this paper, it is suggested that the wind turbines themselves may be used to provide the thrust needed to correct the platform heading, thus eliminating the practical need for submerged thrusters. By controlling the blade pitch of the wind turbines, a turning moment (torque) can be exerted on the platform to correct heading (yaw) relative wind direction. Using the Hexicon H3-18MW platform as a starting point; hydrodynamic, aerodynamic and electromechanical properties of the system are explored, modeled and attempts at model predictive control are made. Preliminary results show that it is possible to control the H3’s position (in yaw) relative the wind using this novel method.

  • 7.
    Baldi, Francesco
    et al.
    Chalmers University of Technology.
    Ahlgren, Fredrik
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Nguyen, Tuong-Van
    Technical University of Denmark, Denmark.
    Gabrielii, Cecilia
    Chalmers University of Technology.
    Andersson, Karin
    Chalmers University of Technology.
    Energy and exergy analysis of a cruise ship2015In: Proceedings of ECOS 2015 - the 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of  Energy Systems, Pau University , 2015Conference paper (Refereed)
    Abstract [en]

    The shipping sector is today facing numerous challenges. Fuel prices are expected to increase in the medium-long term, and a sharp turn in environmental regulations will require several companies to switch to more expensive distillate fuels. In this context, passenger ships represent a small but increasing share of the industry. The complexity of the energy system of a ship where the energy required by propulsion is no longer the trivial main contributor to the whole energy use thus makes this kind of ship of particular interest for the analysis of how energy is converted from its original form to its final use on board.To illustrate this, we performed an analysis of the energy and exergy flow rates of a cruise ship sailing in the Baltic Sea based on a combination of available measurements from ship operations and of mechanistic knowledge of the system. The energy analysis allows identifying propulsion as the main energy user (41% of the total) followed by heat (34%) and electric power (25%) generation; the exergy analysis allowed instead identifying the main inefficiencies of the system: exergy is primarily destroyed in all processes involving combustion (88% of the exergy destruction is generated in the Diesel engines and in the oil-fired boilers) and in the sea water cooler (5.4%); the main exergy losses happen instead in the exhaust gas, mostly from the main engines (67% of total losses) and particularly from those not equipped with heat recovery devices.The improved understanding which derives from the results of the energy and exergy analysis can be used as a guidance to identify where improvements of the systems should be directed.

  • 8.
    Baldi, Francesco
    et al.
    Chalmers University of Technology.
    Nguyen, Tuong-Van
    Technical University of Denmark.
    Ahlgren, Fredrik
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    The application of process integration to the optimisation of cruise ship energy systems: a case study2016In: ECOS 2016: 29th International Conference on Efficiency, Cost, Optimization, Simulation and Envirionmental Impact of Energy Systems. June 19-23 2016, 2016Conference paper (Refereed)
    Abstract [en]

    In recent years, the shipping industry has faced an increasing number of challenges in terms of fluctuating fuel prices, stricter environmental regulations, and concerns about global warming. In this situation, passenger volumes on cruise ships have increased from around 4 million to 13 million from 1990 to 2008 and keep growing today. A small cruise ship can emit about 85 tons of CO2 per day, and require around 27 tons of fuel per day. To keep up with market demand, while reducing their impact on the environment, cruise ships will need to improve their energy efficiency. Most previous research in marine technology relates to energy efficiency focused on propulsion, which for most ship types constitutes the largest energy demand. On cruise ships, however, auxiliary heat and electric power also have a significant importance. For this reason, we focus in this paper on the heat demand and its integration with available sources of waste heat on board. In this study, the principles of process integration are applied to the energy system of a cruise ship operating in the Baltic Sea. The heat sources (waste heat from the main and auxiliary engines in form of exhaust gas, cylinder cooling, charge air cooling, and lubricating oil cooling) and sinks (HVAC, hot water, fuel heating) are evaluated based on one year of operational data and used to generate four operating conditions that best represent ship operations. Applying the pinch analysis to the system revealed that the theoretical potential for heat integration on board could potentially allow the reduction of the external heat demand by between 35% and 85% depending on the investigated case. A technoeconomic optimisation allowed the identification of the most economically viable heat exchanger network designs: two in the “retrofit” scenario and one in the “design” scenario, with a reduction of 13-33%, 15-27% and 46-56% of the external heat demand, respectively. Given the high amount of heat being available after the process integration, we also analysed the potential for the installation of a steam turbine for the recovery of the energy available in the exhaust gas, which resulted in up to 900 kW of power being available for on board electric power demand.

  • 9.
    Baldi, Fransceco
    et al.
    Chalmers University of Technology.
    Ahlgren, Fredrik
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Melino, Francesco
    Universitá di Bologna, Italy.
    Gabrielii, Cecilia
    Chalmers University of Technology.
    Andersson, Karin
    Chalmers University of Technology.
    Optimal load allocation of complex ship power plants2016In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 124, 344-356 p.Article in journal (Refereed)
    Abstract [en]

    In a world with increased pressure on reducing fuel consumption and carbon dioxide emissions, thecruise industry is growing in size and impact. In this context, further effort is required for improvingthe energy efficiency of cruise ship energy systems.In this paper, we propose a generic method for modelling the power plant of an isolated system withmechanical, electric and thermal power demands and for the optimal load allocation of the different componentsthat are able to fulfil the demand.The optimisation problem is presented in the form of a mixed integer linear programming (MINLP)problem, where the number of engines and/or boilers running is represented by the integer variables,while their respective load is represented by the non-integer variables. The individual components aremodelled using a combination of first-principle models and polynomial regressions, thus making thesystem nonlinear.The proposed method is applied to the load-allocation problem of a cruise ship sailing in the Baltic Sea,and used to compare the existing power plant with a hybrid propulsion plant. The results show thebenefits brought by using the proposing method, which allow estimating the performance of the hybridsystem (for which the load allocation is a non-trivial problem) while also including the contribution ofthe heat demand. This allows showing that, based on a reference round voyage, up to 3% savings couldbe achieved by installing the proposed system, compared to the existing one, and that a NPV of11 kUSD could be achieved already 5 years after the installation of the system.

  • 10.
    Bengtsson, Mattias
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Andersen, Kristian
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Hur dokumenteras blackout ombord på fartyg?: En studie av haverirapporter där blackout var en del av händelseförloppet2014Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    On board vessels it is not desirable to have a power failure, a so-called blackout. The thesis

    has investigated to what extent it is feasible to perform comparative and preventive studies

    with the accident reports from European flag states as a basis. This in order to investigate

    recurring shortcomings, of the vessels or in the work on board that has caused the blackout. In

    addition the possibility to categorize the cases was investigated. The categories were technical

    errors, operational errors and organization errors. Roughly half of the cases show that a single

    category of fault could not be identified due to a combination of faults leading to the blackout.

    However there are recurring cases with almost identical scenarios. For example unsatisfactory

    insulation caused fires due to leaking fuel hitting the hot surfaces.

    The survey shows that there is a lack of symmetry regarding the language used, structure,

    scope and form of publication. It also showed faults in the search engines of the databases.

  • 11.
    Bävermalm, Joakim
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    Antifoulingfärger: Beväxning och ytråhetens inverkan på fartygsekonomin2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Med anledning av dagens höga bunkerpriser är det relevant att undersöka vad man kan göra för att minska bunkerförbrukningen ombord. En viktig del vad gäller bunkerbesparingar är att hålla skrovets kondition i gott skick. Här har ett klokt val av antifoulingfärg en stor betydelse, med en bra antifoulingfärg minskar beväxningen av organismer på skrovet. Detta i sin tur leder till ett minskat motstånd, vilket gynnar fartygsekonomin.

    På marknaden finns flertalet antifoulingfärger tillgängliga, men vilken effekt på ytråheten har respektive färg, och hur påverkar ytråhet i form av beväxning fartyget ekonomiskt? Utöver de rent ekonomiska aspekterna ville jag ta reda på om det finns något miljövänligare alternativ, samt hur det står sig gentemot de biocidbaserade antifoulingfärgerna.

    För att svara på detta har en mängd data studerats från bland annat produktdatablad, fartygskonstruktionsböcker, tidsjournaler och hemsidor. Jag konstaterade att det finns mycket pengar att spara på rätt val av antifouling. Något som förvånade mig var att färgtillverkarens miljövänligaste alternativ också var den effektivaste antifoulingen.

  • 12.
    Carpman, Nicole
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Marine Current Resource Assessment: Measurements and Characterization2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    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.

  • 13.
    Carpman, Nicole
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Measurements of tidal current velocities in the Folda fjord, Norway, with the use of a vessel mounted ADCP2014In: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 8A: Ocean Engineering, 2014Conference paper (Refereed)
    Abstract [en]

    Measurements of tidal current water velocities is an important first step in evaluating the potential for a tidal site to be used as a renewable energy resource. For this reason, on site measurements are performed at the inlet of a fjord situated at the coast of Norway. The site has an average width of 580 m and adepth of 10-15 m which is narrow and shallow enough to give rise to water velocities that can be of use for energy conversion. With the use of an Acoustic Doppler Current Profiler (ADCP) cross-section measurements are conducted along four transects. The measurements covered flood and ebb currents around one tide and the data give a first approximation of the magnitude and distribution of the flow field. Depth averaged mean current velocities are calculated along the transects for horizontal bins with sizes in the order of 50 x 50 m. Maximum mean velocity for the flood currents were 1.31 m/s and 1.46 m/s for the ebb currents. The measurements show that even a small amount of data can give an indication of the potential and characteristics ofthe site.

  • 14.
    Carpman, Nicole
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Thomas, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Tidal current phasing along the coast of Norway2016Conference paper (Refereed)
    Abstract [en]

    Tidal currents provide an intermittent source of renewable energy. A high degree of intermittency is unfavorable in the existing power system. However, by aggregating tidal power from sites with variable tidal phase a more firm power outpu tmay be achieved. In this paper, the tidal current phasing between 114 potential tidal energy sites along the Norwegian coast is investigated. Time series of tidal currents are generated with a model that considers the variation in current strength due to the variability in the semi-diurnal tidal cycle (spring to neap, flood to ebb, first to second daily tide etc.). From these, available kinetic energy in the natural flow is calculated. A constant conversion rate is then applied to give the power output at each site. Three scenarios, with varying number of sites and energy extraction, are investigated. The variability in each scenario is quantified on different time scales by filtering the aggregated power and calculate standard deviation and step change. It is found that the variability can be lowered by choosing sites with an advantageous time lag and limit the power output from the most energetic sites. As expected, smoothing is most distinct on short time scales.

  • 15. Chen, WenChuang
    et al.
    Dolguntseva, Irina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Savin, Andrej
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Zhang, YongLiang
    Li, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Svensson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Numerical modelling of a point-absorbing wave energy converter in irregular and extreme waves2017In: Applied Ocean Research, ISSN 0141-1187, E-ISSN 1879-1549, Vol. 63, 90-105 p.Article in journal (Refereed)
    Abstract [en]

    Based on the Navier-Stokes (RANS) equations, a three-dimensional (3-D) mathematical model for the hydrodynamics and structural dynamics of a floating point-absorbing wave energy converter (WEC) with a stroke control system in irregular and extreme waves is presented. The model is validated by a comparison of the numerical results with the wave tank experiment results of other researchers. The validated model is then utilized to examine the effect of wave height on structure displacements and connection rope tension. In the examined cases, the differences in WEC’s performance exhibited by an inviscid fluid and a viscous fluid can be neglected. Our results also reveal that the differences in behavior predicted by boundary element method (BEM) and the RANS-based method can be significant and vary considerably, depending on wave height.

  • 16.
    Dahlin, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Gustavsson, Richard
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Brandskyddet i Göteborgs Hamn AB:s Energihamn: Ett projektarbete i fallstudieform för Göteborgs Hamn AB, som undersöker vilka förväntningar personal vid rederier och fartygsbefäl har på brandskyddet i Energihamnen, en hamnanläggning i Göteborgs Hamn AB.2014Independent thesis Basic level (university diploma), 180 HE creditsStudent thesis
    Abstract [en]

    This thesis is part of a major project that the Port of Gothenburg has embarked upon, and is produced as a result of a project directive. The purpose of that project is to renew its current fire protection in Energihamnen (the Energy Port) but also meet future requirements. The purpose of the present study is to examine what expectations shipping companies and ship´s officers, which regularly arrive to the Energy Port, have on the Port of Gothenburg’s fire prevention systems and fire emergency plans. Further investigated are the requirements that form the basis for the fire protection equipment onboard tankers that regularly arrive in the Energy Port. To obtain answers from the above mentioned purpose, interviews were conducted with three ship owners and five ship officers, and this was combined with a literature summary which consists of the regulatory framework that places specific requirements and recommendations for the fire prevention equipment that will be on board tankers. The interviews were conducted to include the shipping industry's expectations of the Port of Gothenburg’s emergency procedures during cargo operations. The result shows that the majority of respondents expected that the Port of Gothenburg should have firefighting equipment on their docks that can extinguish fires onboard the ship’s deck. They also expected that the port's emergency response plans should be well rehearsed and should also quickly come into force during an emergency.

  • 17.
    Engström, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hydrodynamic Modelling for a Point Absorbing Wave Energy Converter2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Surface gravity waves in the world’s oceans contain a renewable source of free power on the order of terawatts that has to this date not been commercially utilized. The division of Electricity at Uppsala University is developing a technology to harvest this energy. The technology is a point absorber type wave energy converter based on a direct-driven linear generator placed on the sea bed connected via a line to a buoy on the surface.

    The work in this thesis is focused mainly on the energy transport of ocean waves and on increasing the transfer of energy from the waves to the generator and load. Potential linear wave theory is used to describe the ocean waves and to derive the hydrodynamic forces that are exerted on the buoy. Expressions for the energy transport in polychromatic waves travelling over waters of finite depth are derived and extracted from measured time series of wave elevation collected at the Lysekil test site. The results are compared to existing solutions that uses the simpler deep water approximation. A Two-Body system wave energy converter model tuned to resonance in Swedish west coast sea states is developed based on the Lysekil project concept. The first indicative results are derived by using a linear resistive load. The concept is further extended by a coupled hydrodynamic and electromagnetic model with two more realistic non-linear load conditions.

    Results show that the use of the deep water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. Around the resonance frequency, a Two-Body System gives a power capture ratio of up to 80 percent. For more energetic sea states the power capture ratio decreases rapidly, indicating a smoother power output. The currents in the generator when using the Two-Body system is shown to be more evenly distributed compared to the conventional system, indicating a better utilization of the electrical equipment. Although the resonant nature of the system makes it sensitive to the shape of the wave spectrum, results indicate a threefold increase in annual power production compared to the conventional system.

  • 18.
    Farshori, Armaan Hussain
    et al.
    Halmstad University, School of Business, Engineering and Science.
    De Pablo Escribano, David
    Halmstad University, School of Business, Engineering and Science.
    Viability of a New Fender in Market and a New Fender Design Proposal for Small Vessels.2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This dissertation has been carried out for AB Halmstads Gummifabrik (HGF) during the spring of 2016. The purpose of this thesis has been to do a market research on the company’s fender and to give a fender design proposal for small vessels. The expectation in the future is that the design proposal may be implemented into an actual product by the company, and released in the market. The project began with a meeting at HGF with Zaheer, where he gave us an overview and details about the project as well as an explanation of how the project needs to be developed. The project was performed mainly by following the David Ullman’s Methodology. Criteria’s were set together with Zaheer to carry out the research, different ports in different countries from all of the Europe were shortlisted and contacted, especially covering the Scandinavian area. The company’s fender covered a huge range of vessels existing in the European region, but there was gap which existed with the private or small vessels (i.e. Yachts, motorboats, etc.) which were due to the reason that the company’s fender only covered the industrial mid-sized vessels (i.e. Cargos, Tankers, etc.) To fill up the gap a fender design had to be proposed which in turn had to have compatibility with the smaller vessels. Product development was carried out with concept generation and other functionalities. When a concept was finalized a 3D CAD model was made with the help of Unigraphics NX software and 2D drawings were made for future references. The result was a fender design which was simulated and analysed successfully for a range of small vessel berthing using the Altair´s Inspire software.

  • 19.
    Francisco, Francisco
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Sundberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Sonar for Environmental Monitoring: Understanding the Functionality of Active Acoustics as a Method for Monitoring Marine Renewable Energy Devices2015Conference paper (Refereed)
    Abstract [en]

    Active acoustics monitoring (AAM) systems can play an important role in the inspection and survey of the subsea environment around marine renewable energy devices, especially in murky and deep waters. Alternative methods comprising a multifunctional platform based on multibeam (MBS) and Dualbeam (DBS) sonar systems are being developed. The aim is to monitor the environmental impacts during installation, operation and maintenance of wave energy converters, marine current turbines, subsea substations and other offshore renewable energy technologies. At this initial phase, one of the specific objective is to understand the functionality of AAM systems. Field tests were done using the MBS and DBS systems. A platform is being tested at the Lysekil Wave Power Project test site and at the Söderfors Marine Current Project test site. Preliminary results show that the MBS produces better acoustic images when the platform is steady, and when in slow-moving waters such as in harbours and shallow rivers. At near field, the MBS is able to track targets < 20 cm such as fish swimming close to hard structures. The DBS can detect isolated targets at far field. Target dimensions estimated using the sonar match the real dimensions of the same´targets.

  • 20.
    Friis Møller, Eva
    et al.
    National Environmental Research Institute,.
    Andersen Borg, Christian Marc
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Jonasdottir, Sigrun H.
    National Institute of Aquatic Resources.
    Satapoomin, Suree
    Phuket Marine Biological Center.
    Jaspers, Cornelia
    National Institute of Aquatic Resources.
    Nielsen, Torkel Gissel
    National Institute of Aquatic Resources.
    Production and fate of copepod fecal pellets acrossthe Southern Indian Ocean2011In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 158, no 3, 677-688 p.Article in journal (Refereed)
    Abstract [en]

    The vertical distribution of copepods, fecal pellets and the fecal pellet production of copepods were measured at seven stations across the Southern Indian Ocean from productive areas off South Africa to oligotrophic waters off Northern Australia during October/November 2006. We quantified export of copepod fecal pellet from surface waters and how much was retained. Furthermore, the potential impact of Oncaea spp. and harpacticoid copepods on fecal pellets degradation was evaluated and found to be regional substantial. The highest copepod abundance and fecal pellet production was found in the western nutrient-rich stations close to South Africa and the lowest at the central oligotrophic stations. The in situ copepod fecal pellet production varied between 1 and 1,000 mu g C m(-3) day(-1). At all stations, the retention of fecal pellets in the upper 400 m of the water column was more than 99% and the vertical export of fecal pellets was low (< 0.02 mg m(-2) day(-1)).

  • 21. Garme, K.
    et al.
    Burstrom, Lage
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
    Kuttenkeuler, J.
    Measures of vibration exposure for a high-speed craft crew2011In: Journal of Engineering for the Maritime Environment (Part M), ISSN 1475-0902, Vol. 225, no 4, 338-349 p.Article in journal (Refereed)
    Abstract [en]

    The paper compares measurement-based measures for human vibration exposure. Data were collected during sea trials on a 10 m, 50 kn coastguard craft equipped with a three-axial accelerometer at the coxswain seat and with vertically mounted gauges measuring the acceleration of the cockpit floor. The ISO 2631-1:1997 measures of vibration (namely the root-mean-square (r.m.s.) value of the whole-body vibration (determined from the frequency-weighted acceleration signal), the maximum transient vibration value (MTVV), and the vibration dose value), the ISO 2631-5:2004 measure (namely the daily equivalent static compression dose Sed), and also statistically based measures to evaluate the acceleration magnitude are compared and discussed with respect to their ability to identify the mitigating effect of the suspension seat and how the different measures rank the severity of the high-speed craft (HSC) ride. The paper concludes that the r.m.s. value and the MTVV are unsuitable for evaluation of the conditions aboard while the other investigated measures show potential in this respect. Further the approach of ISO 2631-5:2004 taking both the short-term and the long-term perspectives on the human exposure to vibration is concluded to be the most mature method well suited to evaluation of HSC conditions.

  • 22.
    Garme, Karl
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Rosén, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Stenius, Ivan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Kuttenkeuler, Jakob
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Rough water performance of lightweight high-speed craft2014In: Journal of Engineering for the Maritime Environment (Part M), ISSN 1475-0902, Vol. 228, no 3, 293-301 p.Article in journal (Refereed)
    Abstract [en]

    Previous studies have shown how the use of composite materials and application of sophisticated design methods can give significantly lighter high-speed craft structures than what is normally achieved for traditional aluminium designs. A reduction in structural mass and a corresponding reduction in displacement improve the craft calm water performance but can be unfavourable regarding the rough water performance. Here, the rough water performance of two versions of a fast patrol vessel, one in aluminium and the other in carbon fibre sandwich, is studied with simplified semi-empirical methods and more advanced non-linear time domain simulations. In speeds up to 30 knots, the rough water performance of the two craft versions is found to be practically equal. At higher speeds, the lighter composite craft experiences higher vertical accelerations than the heavier aluminium craft, which implies less operational availability. Using trim ballast tanks, the rough water performance of the lighter craft is improved, and it is shown that the acceleration levels can be reduced and even lowered relative to the heavier aluminium craft. This means that the calm water advantages of a lighter composite vessel can be utilized with the same ride comfort and operational availability as for a heavier aluminium vessel.

  • 23.
    Grönvall, Erik
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Rydmarker, Carl
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    En studie kring rapportering av near-misses.2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 24. Gulbinskas, Saulius
    et al.
    Mileriene, Rosita
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Suzdalev, Sergej
    Blažauskas, Nerijus
    Cumulative impacts of the coastal and marine activities: case study of Lithuania and South Eastern Baltic region2011In: Integrated Coastal Zone Management: Proceedings of the 2nd International Symposium of Integrated Coastal Zone Management, 2011Conference paper (Refereed)
  • 25.
    Göransson, Malin
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Olsson, Madeleine
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Rekryteringsprocess av maskinbefäl: en kvantitativ studie om hur tjänsterna ombord tillsätts2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med det här arbetet var att kartlägga rekryteringsprocessen i svenska rederier och bemanningsbolag av maskinbefäl. För att ta reda på detta skickades det ut ett antal enkäter till personalrekryterarna i respektive rederi/bemanningsbolag. Studien är en kvantitativ undersökning för att få in ett så stort underlag som möjligt och därefter kunna få fram ett trovärdigt resultat. Resultatet blev att rekryteringsprocessen har påverkats av utflaggningen av fartygen och då framför allt för juniorbefälen. Det som personalrekryterarna ansåg som mest betydelsefullt vid nyrekrytering av maskinbefäl är rekommendationer från redan anställda i rederiet/bemanningsbolaget och fullständig sjöingenjörsexamen. Arbetsförmedlingens tjänster användes i mindre grad på grund av det dåliga urvalet och inte heller available position-sidan på rederiernas/bemanningsbolagens hemsida vid rekrytering av nya maskinbefäl.

  • 26.
    Göteman, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Engström, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eriksson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hann, Martyn
    Ransley, Edward
    Greaves, Deborah
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wave loads on a point-absorbing wave energy device in extreme waves2015In: Journal of Ocean and Wind Energy, ISSN 2310-3604, Vol. 2, no 3, 176-181 p.Article in journal (Refereed)
  • 27.
    Göteman, Malin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Engström, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eriksson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fast modeling of large wave energy farms using interaction distance cut-off2015In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, no 12, 13741-13757 p.Article in journal (Refereed)
    Abstract [en]

    In many wave energy concepts, power output in the MW range requires the simultaneous operation of many wave energy converters. In particular, this is true for small point-absorbers, where a wave energy farm may contain several hundred devices. The total performance of the farm is affected by the hydrodynamic interactions between the individual devices, and reliable tools that can model full farms are needed to study power output and find optimal design parameters. This paper presents a novel method to model the hydrodynamic interactions and power output of very large wave energy farms. The method is based on analytical multiple scattering theory and uses time series of irregular wave amplitudes to compute the instantaneous power of each device. An interaction distance cut-off is introduced to improve the computational cost with acceptable accuracy. As an application of the method, wave energy farms with over 100 devices are studied in the MW range using one month of wave data measured at an off-shore site.

  • 28.
    Hillberg, Torbjörn
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Holmberg, Emil
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Metanol som marint bränsle: Alkohol som en lösning, inte ett problem2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Since the start of industrialization humans have affected the climate balance by burning fossil fuels. Exhaust gas emissions caused by the international shipping cannot be attributed to any particular nation because of its global and complex business. The International Maritime Organisation has therefore undertaken the responsibility to reduce the environmental impact of shipping. The introduction of new environmental goals has resulted in stricter global and national regulations that force the shipping industry to make significant adjustments in a short period of time. As a solution to meet future requirements for exhaust gas emissions several alternative fuels have been discussed. Operating vessels on methanol results in low exhaust gas emissions and is therefore considered to have the potential to become a sustainable fuel for the shipping industry. The aim of this study was to investigate what shipping companies, machine manufacturers and classification societies considers about methanol as an alternative fuel. Initially, a literature study was implemented which formed the basis of the interview questions. The result shows that methanol is considered to have great potential compared with other alternative fuels. Since methanol can be produced from excess energy and transportation can be done with existing infrastructure methanol is considered both environmentally friendly and economically viable. Nevertheless, the highly fluctuating methanol price can causes shipping companies to hesitate in the financing of developments that is necessary for the realization of methanol operation on board vessels.

  • 29.
    Hjälte, Robert
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Nordstrand, John
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    -BLB- M/S Calmare Nyckel: Ballast-, Läns- & Brandsystemet på M/S Calmare Nyckel2015Independent thesis Basic level (professional degree), 180 HE creditsStudent thesis
    Abstract [en]

    This report is produced to document the existing installation regarding the ballast, bilge and fire system aboard the vessel M/S Calmare Nyckel. According to the specifications of the assignment a proposal regarding improvements will also be presented. The suggestions are mainly based on data from a supplier of valve components and the demands put up by the classification society. The improvements are considered with reduced risk and increased safety in mind. The main differences in the new proposals are the separation of the bilge system from the other two systems, that the most vital functions can be remote-controlled by pneumatics and that all components are marked according to industry standard.

  • 30.
    Jansson, Johan
    et al.
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz). Basque Center for Applied Mathematics, Spain.
    Nava, V.
    Sanchez, M.
    Aguirre, G.
    De Abreu, Rodrigo Vilela
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Hoffman, Johan
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz). Basque Center for Applied Mathematics, Spain.
    Villate, J. L.
    Adaptive simulation of unsteady flow past the submerged part of a floating wind turbine platform2015In: MARINE 2015 - Computational Methods in Marine Engineering VI, International Center for Numerical Methods in Engineering (CIMNE), 2015, 35-46 p.Conference paper (Refereed)
    Abstract [en]

    Offshore floating platforms for wind turbines represent challenging concepts for designers trying to combine an optimal compromise between cost effectiveness and performance. Modelling of the hydrodynamic behaviour of the structure is still the subject of wide debate in the technical communities. The assessment of the hydrodynamics of the support structure is not an easy task as the floaters consist of an assembly of columns, braces and pontoons, commonly also with heave plates: Each of these components corresponds to a different hydrodynamic model and it further interacts with the other elements. This results in very complex non-linear modeling, which makes it necessary to resort to computational fluid dynamics (CFD) methods for the evaluation of the combined hydrodynamics. In the framework of the collaboration between the Basque Centre for Applied Mathematics (BCAM) and Tecnalia R&I, the interaction of the sea flow with a semisubmersible floating offshore wind platform have been calculated by using the open source solver Unicorn in the FEniCS-HPC framework when subject to a steady inflow. The prototype of the platform consists in a semi-submersible 4-columns column stabilized platform - NAUTILUS Floating Solutions concept-; columns are connected by a rigid ring pontoon provided with heave damping plates at the bottom. The novelty of the approach in FEniCS-HPC hinges upon an implicit formulation for the turbulence, a cheap free slip model of the boundary layer and goal-oriented mesh adaptivity [8, 6, 9, 20, 1]. We find that the results are consistent with experimental results for cylinders at high Reynolds number.

  • 31.
    Juliusson, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    HYDRODYNAMIC OPTIMIZATION OF TWO-DIMENSIONAL MULTI-ELEMENT TRAWL-DOOR SHAPES USING LOCAL SURROGATE MODELS AND ANALYSIS OF CONTROLLABLE TRAWL-DOOR SHAPES2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The study is motivated by the quest to lower the fuel consumption of trawlers and reduce green house gas emissions. Conventional trawl-doors contribute to about one third of the trawlers fuel consumption. Design and optimization of trawl-doors using computational models is vital in minimizing the fuel consumption.The main objective of this work is to develope an optimization algorithm for the shape design of trawl-doors using computational uid dynamic (CFD) models. High-fidelity CFD models are computationally expensive and therefore, conventional optimization methods, which often require large number of evaluations are not feasible. The proposed method is iterative and uses local second order response surface approximation models of the high-fidelity CFD model, constructed in each iteration. The RSA are constructed locally and are regenerated at each iteration in new domain. We use a trust region mechanism to move the center of the search domain and to increase or decrease the size ofthe search domain. This reduces the number of evaluations. We propose novel shaped trawl-door shapes and investigate their performance. These shapes are similar to multi-element airfoils on aircraft i.e., airfoil shapes with slats and flaps. We apply the proposed optimization algorithm to the novel-shaped design of two-dimensional multi-element trawl-door shapes with several design variables controlling the slat and flap positions and alignment. The objective is to increase the hydrodynamic efficiency for a given lift constraint. The results are then compared to the performance of a typical trawl-door shape. The results indicate that a satisfactory design can be obtained at the cost of few iterations of the algorithm. We also investigate controllable trawl-doors where the flap angle can be varied, depending on the operational condition.

  • 32.
    Langhamer, Olivia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    The location of offshore wave power devices structures epifaunal assemblages2016In: International Journal of Marine Energy, ISSN 2214-1669, Vol. 16, 174-180 p.Article in journal (Refereed)
    Abstract [en]

    With large-scale development of offshore wave power conversion, artificial structures become more common in the open sea. To examine how wave power devices may be colonized by epifaunal organisms, 21 concrete foundations used for anchoring wave power generators were studied during two years, 2007 and 2008. The foundations were placed in two different clusters, located north and south within the Lysekil test site at the Swedish west coast. The degree to which early recruits covered the foundations and the succession of epibenthic communities were documented during two years. A succession in colonization over time was observed, with a higher degree of cover in the northern location. Furthermore, the northern location showed an increase in number of individuals, number of species and in Shannon-Wiener diversity in 2008. Dominant organisms on the foundations were the serpulid tubeworms (Pomatoceros triqueter) and barnacles (Balanus sp.). This comprehensive large-scale study about succession and colonization patterns on wave power foundations suggests that the location of wave energy devices affects colonization patterns. This gives indications on settlement patterns on already operating and planned offshore wave power parks further off the coasts.

  • 33.
    Leijon, Jennifer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Dolguntseva, Irina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ekergård, Boel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Boström, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Comparison of Damping Controls for a Wave Energy Converter with a Linear Generator Power Take-Off: a Case Study for the Lysekil and Wave Hub Test Sites2016Conference paper (Refereed)
  • 34.
    Lindberg, Marcus
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Johansson, Per
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Joélius, Mikael
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    LNG - Framtidens fartygsbränsle: Vad är det som hämmar utvecklingen av LNG-drift i Sverige?2015Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Shipping today faces stricter environmental requirements for pollution from vessels. Shipping companies have started to look for alternative fuel to achieve better environmental outcome. The Baltic Sea today is a major trading area for shipping . On 1 of January 2015 a new set of brand new and stricter regulation is getting implemented and these regulations are called SECA. Vessel running on LNG as an alternative fuel is today discussed extensively within the Swedish Maritime forum where emissions of NOx, sulfur and particles are less recipients than in heavy fuel oil (HFO). One of todays problems with a LNG distribution in Sweden are that the infrastructure is incomplete and outdated. This report has been built upon qualitative interviews with important actors within the Swedish maritime forum and also what impedes the development of the LNG’s infrastructure. The outcome of the interviews showed that the development has been slowed down because none within the Swedish martime forum have dared to take the first step. The ports does not want to develop terminals when there is no market demand and the shipping companies does not want to build vessel that runs on LNG when there is no market for distribution. Swedish governments involvement has been very weak, almost non-existing. There are also gaps in the Swedish regulations and restrictions of LNG cargo handling. This is aslo one of the factors that the development of LNG has been impeded. 

  • 35.
    Lindroth [formerly Tyrberg], Simon
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Buoy and Generator Interaction with Ocean Waves: Studies of a Wave Energy Conversion System2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    On March 13th, 2006, the Division of Electricity at Uppsala University deployed its first wave energy converter, L1, in the ocean southwest of Lysekil. L1 consisted of a buoy at the surface, connected through a line to a linear generator on the seabed. Since the deployment, continuous investigations of how L1 works in the waves have been conducted, and several additional wave energy converters have been deployed.

    This thesis is based on ten publications, which focus on different aspects of the interaction between wave, buoy, and generator. In order to evaluate different measurement systems, the motion of the buoy was measured optically and using accelerometers, and compared to measurements of the motion of the movable part of the generator - the translator. These measurements were found to correlate well. Simulations of buoy and translator motion were found to match the measured values.

    The variation of performance of L1 with changing water levels, wave heights, and spectral shapes was also investigated. Performance is here defined as the ratio of absorbed power to incoming power. It was found that the performance decreases for large wave heights. This is in accordance with the theoretical predictions, since the area for which the stator and the translator overlap decreases for large translator motions. Shifting water levels were predicted to have the same effect, but this could not be seen as clearly.

    The width of the wave energy spectrum has been proposed by some as a factor that also affects the performance of a wave energy converter, for a set wave height and period. Therefore the relation between performance and several different parameters for spectral width was investigated. It was found that some of the parameters were in fact correlated to performance, but that the correlation was not very strong.

    As a background on ocean measurements in wave energy, a thorough literature review was conducted. It turns out that the Lysekil project is one of quite few projects that have published descriptions of on-site wave energy measurements.

  • 36.
    Liwång, Hans
    Swedish National Defence College, Department of Military Studies, Military-Technology Division.
    Riskanalys inom fartygsskydd - en analysstrategi för bättre beslutsunderlag2015In: Tidskrift i sjöväsendet, ISSN 0040-6945, no 2, 151-168 p.Article in journal (Other academic)
    Abstract [sv]

    Sjöfartsskydd bedrivs idag både av militära styrkor och civila redare. Det är inte ofarligt, men nödvändigt och viktigt. Med fokus på säkerhetshot undersöker denna avhandling hur fartyg ska förbereda sig inför potentiellt farlig verksamhet, det vill säga hur man skapar ett lämpligt riskmedvetande i förhållande till fartygsskydd.

    Inom sjösäkerhet har regler, rekommendationer och metoder systematiskt utvecklats under många år. Inom sjöfartsskydd är däremot frågorna inte lika belysta och angreppssätten och erfarenheterna är ofta dolda bakom hemligstämplar. Det är rimligt att anta att riskanalysmetoder från andra områden kan användas även för sjöfartsskyddsanalyser, men inte utan att metoderna anpassas till områdets specifika behov. Därför leder den begränsade forskningen och dokumentationen inom området till ett kunskapsgap.

    För att reducera de identifierade utmaningarna inom sjöfartsskydd undersöks i avhandling hur en lämplig analysstrategi för fartygsskydd ser ut. För att öka den övergripande säkerheten för de analyserade verksamheterna ska metoden kunna stötta nödvändiga kompromisser mellan sjösäkerhet och fartygsskydd. Syftet är att utveckla en analysstrategi som är systematisk och som ger beslutsfattaren en lämplig bild av de aktuella riskerna. För att undersöka detta område behandlas i avhandlingen både hot mot militära fartyg och hotet mot civila fartyg från sjöröveri. Därför kan resultatet användas för att utveckla både militära doktriner och civila riktlinjer.

    Studien visar att hur fartygets verksamhet beskrivs i analysen är centralt för resultatet och därmed förståelsen av riskerna. Inte bara skyddslösningar i sig, utan även besättningens riskförståelse och hur det implementerade skyddet förstås måste inkluderas i analysen. Hur det implementerade skyddet förstås kommer också i stor utsträckning att påverka effektiviteten hos implementerade åtgärder. I avhandlingen konstateras också att om analysen görs utan att ta hänsyn till de osäkerheter som finns kan det innebära att resultatet är missvisande. Därför är den osäkerhetsanalys som är möjlig med ett kvantitativt angreppssätt nödvändig, speciellt om syftet är att identifiera robusta skyddsåtgärder.

  • 37.
    Mondejar, Maria E.
    et al.
    Lund University.
    Ahlgren, Fredrik
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Thern, Marcus
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Genrup, Magnus
    Lund University.
    Study of the on-route operation of a waste heat recoverysystem in a passenger vessel2015In: Clean, Efficient and Affordable Energy for a Sustainable Future / [ed] Yan, J; Shamim, T; Chou, SK; Li, H, Elsevier, 2015, Vol. 75, 1646-1653 p.Conference paper (Refereed)
    Abstract [en]

    Waste heat recovery systems for power generation are gaining interest among the marine transport sector as asolution to accomplish the upcoming more restrictive regulations on emissions and to reduce the total fuelconsumption. In this paper we evaluate how a waste heat recovery system based on a regenerative organic Rankinecycle (rORC) could improve the performance of a passenger vessel. The case study is based on the M/S BirkaStockholm cruise ship, which covers a daily route between Stockholm (Sweden) and Mariehamn (Finland).Experimental data on exhaust gas temperatures, fuel consumption and electricity demand on board were logged for aperiod of four weeks. Based on the optimal fluid and configuration obtained in a previous work, an off-design modelof a rORC working with benzene was used to estimate the power production at the different load conditions during aport-to-port trip of the vessel. The power generation curve of the rORC over time was compared to that of theelectricity demand of the ship. Results showed that the rORC could provide up to 16% of the total power demand.However, this value should be corrected if the auxiliary engines load is reduced as a consequence of the partialcoverage of the electricity demand by the ORC.

  • 38.
    Mondejar, Maria E.
    et al.
    Lund University.
    Ahlgren, Fredrik
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Thern, Marcus
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy. Lund University.
    Genrup, Magnus
    Lund University.
    Quasi-steady state simulation of an organic Rankine cycle for waste heat recovery in a passenger vessel2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 185, no Special Issue Part 2, 1324-1335 p.Article in journal (Refereed)
    Abstract [en]

    In this work we present the quasi-steady state simulation of a regenerative organic Rankine cycle (ORC)integrated in a passenger vessel, over a standard round trip. The study case is the M/S Birka Stockholmcruise ship, which covers a daily route between Stockholm (Sweden) and Mariehamn (Finland).Experimental data of the exhaust gas temperatures, engine loads, and electricity demand on board werelogged over a period of four weeks. These data where used as inputs for a simulation model of an ORC forwaste heat recovery of the exhaust gases. A quasi-steady state simulation was carried out on an offdesignmodel, based on optimized design conditions, to estimate the average net power production ofthe ship over a round trip. The maximum net power production of the ORC during the round trip wasestimated to supply approximately 22% of the total power demand on board. The results showed apotential for ORC as a solution for the maritime transport sector to accomplish the new and morerestrictive regulations on emissions, and to reduce the total fuel consumption.

  • 39.
    Mårelius, Nicklas
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    RTK-teknikens användningsområden2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study was to investigate whether RTK - technology (Real Time Kinematic) in the future may be used for piloting in Sweden, on board vessels with limited depth of water under the keel. The squat effect cured vessels when they passing over an area of shallow waters in a fairway or a channel. To reduce the squat effect it can be done to increase the speed or change the trim of the vessel. The study has been designed along a qualitative method, which is about one chooses to process and analyze their information by verbal analysis methods. This has been carried out by interviewing a number of selected pilots that are both familiar and less familiar with the technology. In this way, highlighted various aspects of the technology and whether there are other areas that pilots can use this equipment in their daily work. In the implementation of the essay was elected a systematic literature. It was conducted a global search to obtain information about where the accident occurred of the squat effect and which countries that have been tested this technology onboard. The result of the RTK-technology is that pilots and ship's officers have the opportunity to find out how the vessel is moving and when it is exposed of the squat effect. The RTK-technology are able to provide information how the vessel move with an accuracy of 3-4 centimeters at every stage and get a more exact speed even in sideways. It is also possible to obtain a three-dimensional image of the vessel. The results confirm that there is a need and an interest for further testing with the RTK-technology. The results also showed that the technology is useful for the pilots and how it can useful for them in their daily work.

  • 40.
    Nord, Mihai
    et al.
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    Dyhr, Johan
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    Risker med trackpilot: En riskanalys av Sjöfartshögskolans trackpilot i navigationssimulatorn2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Ombord på dagens moderna fartyg finns det oftast en autopilot med trackpilot - funktion. Den behöver information från många olika sensorer för att kunna framföra fartyget utefter en förprogrammerad rutt. Om en av sensorerna inte ger rätt information kan det hända att trackpiloten gör en felbedömning av t.ex. kurs att styra. Ombord på fartyg med DP - system finns det färdiga FMEA - dokument för användaren där man kan läsa vilken åtgärd som kan behövas för att bibehålla DP - klassen. Någon sådan manual har vi inte stött på ombord på vanliga fartyg. Därför ville vi undersöka riskerna med trackpilot och om en FMEA - riskanalys skulle kunna vara användbart för ett trackpilot - system. Vi utförde en FMEA - riskanalys för trackpilot -systemet som finns i Sjöfartshögskolans simulator. De slutsatser som vi kan dra är att, det med hjälp av, en FMEA - riskanalys ger användaren en god inblick i hur olika fel påverkar trackpilot:en.

  • 41.
    Orlowitz, Esben
    et al.
    University of Southern Denmark, Denmark.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Operational Modal Analysis for Dynamic Characterization of a Ro-Lo Ship2014In: Journal of Ship Research, ISSN 0022-4502, E-ISSN 1542-0604, Vol. 58, no 4, 216-224 p.Article in journal (Refereed)
    Abstract [en]

    The dynamic characteristics of ship structures are becoming more important as the flexibility of modern ships increases, for example, to predict reliable design life. This requires an accurate dynamic model of the structure, which, because of complex vibration environment and complex boundary conditions, can only be validated by measurements. In the present paper the use of operational modal analysis (OMA) for dynamic characterization of a ship structure based on experimental data, from a full-scale measurement of a 210-m long Ro-Lo ship during sea trial, is presented. The measurements contain three different data sets obtained under different operating conditions of the ship: 10 knots cruising speed, 18 knots cruising speed, and at anchor. Natural frequencies, modal damping ratios, and mode shapes have been successfully estimated for the first 10 global modes. Damping ratios for the current ship were found within the range 0.9%‐1.9% and natural frequencies were found to range from 0.8 to 4.1 Hz for the first 10 global modes of the ship at design speed (18 knots). The three different operating conditions showed, in addition, a speed dependency of the natural frequencies and damping ratios. The natural frequencies were found to be lower for the 18-knots condition compared with the two other conditions, most significantly for the vertical bending modes. Also, for the vertical bending modes, the damping ratios increased by 28%‐288% when the speed increased from 10 to 18 knots. Other modes were not found to have the same strong speed dependency.

  • 42.
    Parada Quinteros, Roberto Carlos
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy. Linneuniversitetet.
    Vajda, Robert Kristian Viktor
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy. Linneuniversitetet.
    Dimbarriär: En studie rörande vattenbaserat brandskydd2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    This study has been made to research the development in fire safety and fire fighting on seagoing vessels. In that the fire fighting team can be alleviated and assisted by a Water Mist Barriers help against the fire hazards.

    Fires are often caused by accidents or machine failures onboard vessels, in some of this cases there is enough time to act quickly and in other cases the crew is notified by the fire detecting system. In the scenarios where the fire has been given time to progress, or is caused to burn in a highly flammable substance, it becomes very difficult to gain control over the conflagration at any rapid pace. This decreases the time for the crew to assemble and prepare for a fire fighting action.

    It is for this kind of situations that a Water Mist Barrier can be used as a protection. Its purpose is to gain time for the crew to regroup and perform a decisive countermeasure. Quick advances towards the fire, hazard observation, placing of the Water Mist Barrier and then withdraw to regroup for new orders of action.

    Another fire hazardous scenario can transpire on a passenger cruise, where passengers need to be evacuated between hazardous areas that can be heated or filled with smoke. In such an occurrence the Water Mist Barriers water curtain would create a separation between the passenger and the hazard, which would block the radiation heat and create a path for the passengers to be evacuated by.

    The Water Mist Barrier should be a tool to ease the fire extinguishing work, its water curtain would provide with a shield and its main purpose is to improve the response time for a quick and planed fire hazard response on seagoing vessels.

  • 43.
    Pettersson, Daniel
    et al.
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    Wallerstein, Fanny
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    IMO:s barlastkonventions konsekvenser för sjöfarten inom Östersjön2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The task discussed the consequences within the ship’s operation (economical costs and technology) companies will be affected with when IMO’s Ballast Water Convention enters into force and ballast water has to be treated before entrance to the Baltic Sea. The purpose with the task was to find out which consequences companies will be forced with when IMO’s Ballast Water Convention enters into force. The result compares the difference between law and recommendation because HELCOM’s recommendations are based on IMO’s Ballast Water Convention’s laws. A qualitative method has been used, such as an open interview form, where four different companies were interviewed. The purpose with the interviews was to see if the companies followed HELCOM’s recommendations and which consequences it would lead to and would be necessary when the Ballast Water Convention enters into force. The results showed that the costs would be extensive when installation takes place and it will require technical arrangements. The task also shows that the purchase cost only makes a small part of the vessel’s investment and ballast water treatment systems are almost totally maintenance-free.

  • 44.
    Simon, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Assessment of Embodied Energy and Carbon Emissions of the Swansea Bay Tidal Lagoon from a Life Cycle Perspective2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    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.

  • 45.
    Skoglund, Lukas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems. Seaware AB, Stockholm, Sweden.
    Kuttenkeuler, Jakob
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Rosén, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Ovegard, Erik
    Seaware AB, Stockholm, Sweden..
    A comparative study of deterministic and ensemble weather forecasts for weather routing2015In: Journal of Marine Science and Technology, ISSN 0948-4280, E-ISSN 1437-8213, Vol. 20, no 3, 429-441 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents and discusses the results of a comparison between using deterministic and ensemble weather forecasts for weather routing. The study is based on comparisons between predicted and realised performance of routes suggested by a route optimization method and focuses on two important performance factors, namely, fuel consumption and late arrival. The study is purely qualitative since the simulations do not include re-routing of the vessel as new forecasts become available. To perform the study a multi-objective dynamic programming method is tailored to the problem and implemented to perform the route optimization and a ship performance model is used to calculate the additional fuel consumption due to wind and waves acting on the ship. The results show that route optimization using ensemble weather forecasts has the potential to reduce the risk of late arrival for voyages during periods of harsh weather.

  • 46.
    Strömstedt, Erland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Submerged Transmission in Wave Energy Converters: Full Scale In-Situ Experimental Measurements2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Different wave power technologies are in development around the world in different stages of prototype testing. So far only a few devices have been deployed offshore at full scale for extended periods of time. Little data is published about how these different devices perform.

    This thesis presents results from experiments with the full-scale offshore wave energy converters at the Lysekil research site on the Swedish west coast. The theories, experiments, measurements, performance evaluations and developments of the submerged transmission in the direct driven permanent magnet linear generator are in focus. The reciprocating submerged transmission fulfills the purpose of transmitting the absorbed mechanical wave energy through the capsule wall into the generator, while preventing the seawater from entering the capsule and reducing the life time of the converter.

    A measuring system with seven laser triangulation sensors has been developed to measure small relative displacements between piston rod and seal housing in the submerged transmission with excellent accuracy for the purpose of evaluating both functional behavior and successive wear in-situ. A method for calculating relative tilt angles, azimuth angles, differential tilt angles, and successive wear in the submerged transmission has been developed. Additional sensors systems have been installed in the converter enabling correlation and a thorough investigation into the operating conditions of the transmission and the converter. The thesis presents unique results from the measurements. A data acquisition system transmits the signals from the converter on the seabed to an onshore measuring station. Results are presented in time-, frequency- and the time-frequency domain.

    The results have given important information for further development of the submerged transmission, which is important to the survivability of the system. The thesis describes the status of research, and is a step that may influence future designs of wave energy devices for reaching survivability and a cost-effective renewable energy system.

  • 47.
    Svedin, Lina
    et al.
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    Johansson, Rebecca
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    Kumlin, Amanda
    Linnaeus University, Faculty of Science and Engineering, Kalmar Maritime Academy.
    Lathund Kranar: Undervisningsmaterial för delkurs TRI2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There is not adequate lesson basis for the course in maintenance technology, module TR I interms of lifting devices. This in combination with the accident reports which can be found inINSJÖ has led us to compile teaching materials in the form of images and text. To establish areal need exists, a qualitative study is conducted. Interviews with chief officers whopreviously studied at the 4-year Master Programme in Nautical Science in Kalmar under thecurrent curriculum was conducted by telephone. The results of these interviews showed that aneed existed and we could proceed with the compilation of teaching materials. The results ofthe examination and discussion with the teacher of the course gave an idea of which parts ofthe subject that would be delved into deeper in the crib. For the instructional materials weused mainly laws and regulations as evidence base. After consultation with the teacher wedecided that the crib will be complemented by a power point presentation which the teacherswill be able to use in the classroom.

  • 48.
    Svensson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Experimental results from the Lysekil Wave Power Research Site2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents how experimental results, from wave power research performed offshore at the Lysekil research site, were obtained. The data were used to verify theoretical models as well as evaluate the feasibility of wave power as a future sustainable energy source.

    The first experiments carried out at the research site was the measurement of the force in a line where one end was connected to a buoy with a diameter of 3 m and the other end to a set of springs with limited stroke length. The system is exposed to high peak forces compared to average forces. The maximum measured force in the line, when the buoy motion is limited by a stiff stopper rope is ten times the average force in that particular sea state.

    The experiment performed on the first wave energy converter tested at the Lysekil Research Site is described. The infrastructure of the site is presented where the central connection point is the measuring station. The key finding is that it is possible to transform the motions of ocean waves into electrical energy and distribute it to land.

    Many wave energy converters must be interconnected if large amounts of energy are to be harvested from the waves. The first submerged substation intended for aggregation of energy from wave power converters is described, with focus on the measurement and control system placed inside the substation. During this experiment period the generators were equipped with many different sensors; these measurements are explained in the thesis.

    The system that aggregates power from the studied wave energy converter is regularly exposed to peak power of up to 20 times the maximum average output from the converter.

    Vertical and horizontal movement of the buoy has been measured in different ways. The result is that the vertical displacement of the buoy can be measured with a simple accelerometer circuit but it is much more complicated to measure the horizontal displacement. A special method for measuring the horizontal displacement has been implemented by measuring the strain in the enclosure and the force in the line.

1 - 48 of 48
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