| 1. |
- Cullinane, Kevin
(författare)
-
Targeting the Environmental Sustainability of European Shipping: The Need for Innovation in Policy and Technology
- 2014
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- At their Summit meeting in Gothenburg in June 2001, Europe’s heads of state and government reached agreement on a European strategy for sustainable development. The social and economic dimensions of the Lisbon strategy were complemented by an environmental dimension. Thus, the Gothenburg Summit represents a breakthrough for sustainable development in the European Union (EU). The University of Gothenburg and Chalmers University of Technology made a commitment to serve, through the joint Centre for Environment and Sustainability (GMV), as a hub for research and scientific follow up of the EU sustainable development strategy. In order to fulfill this commitment, the two universities have established a European Panel for Sustainable Development (EPSD), together with Lund University. In addition, individual members from other universities and research institutes contribute to the work of the Panel. The Centre for Environment and Sustainability (GMV) in Gothenburg is the lead organization in the EPSD. The first report produced by the Panel in 2004 was “From Here to Sustainability – Is the Lisbon/Gothenburg Agenda Delivering?” This was put forward as an independent contribution from academics to the mid-term review of the Lisbon strategy for growth, competitiveness and jobs. The second report “Make the Kok-report sustainable” was produced by the EPSD as a reflection on, and a response to, the mid-term review on the Lisbon strategy chaired by the former Prime Minister of the Netherlands, Wim Kok. The third report “Towards a Smart Growth Strategy for Sustainable Development” aimed to contribute to the re-launch of the EU sustainable development strategy. It contained a critical assessment of “A Platform for Action”, the proposal for an updated strategy put forward by the European Commission. The fourth report “TAKING CHILDREN SERIOUSLY – How the EU can Invest in Early Childhood Education for a Sustainable Future” presented research on children’s interest and ability to understand questions on the social, economic and environmental dimensions of sustainable development. The present report “Targeting the Environmental Sustainability of European Shipping: The Need for Innovation in Policy and Technology” has emerged from a background survey with the aim of mapping what is being done on sustainable shipping within the European Union. A wide scope of strategic EU policy sectors and documents, including existing directives, legislation and regulations on shipping were scrutinized to describe the actual knowledge framework. The background study defines areas where new research could contribute in closing knowledge gaps, and gives a compilation of directives and policy documents concerning sustainable shipping in a European perspective. Based on a definition of sustainable shipping that include all three pillars of sustainable development, the present report presents a holistic view and strategies for achieving a sustainable shipping industry. The report provides scientifically based knowledge of various aspects that affect sustainability at sea, such as particles, greenhouse gases, ship wrecks, ship recycling, and intermodality, as well as a comprehensive overview and updates on regulations. These various areas are presented as separate chapters and solid recommendations are presented on future actions (on EU and international level) to make the shipping industry in Europe a sustainable business. The main author of the report was Prof. Kevin Cullinane, Edinburgh Napier University, UK. The separate chapters in the report were written by Lars Barregård, University of Gothenburg, Erik Fridell, Hulda Winnes, IVL Swedish Environmental Research Institute (Particle emission from ships); Hannes Johnson 1 , Chalmers University of Technology (GHG Emissions and the Energy Efficiency Gap in Shipping); Peter Domini, Stena Metall (Ship Recycling: A Global Issue); Lars Barregård, University of Gothenburg (The Health Risks Associated with the Ship Breaking Industry); Ida-Maja Hassellöv, Chalmers University of Technology (Potentially Polluting Shipwrecks); Abhinayan Basu Bal, University of Gothenburg (Sustainable Intermodal Transport with Short Sea Shipping in the EU); A number of researchers and knowledgeable persons have constituted a reference group and further contributed to the report: Katarina Gårdfeldt, Maria Svane, Dan Strömberg, and Jonas Norrman, GMV, Gothenburg; Karin Andersson, Björn Södahl, Josefin Borg, and Oliver Lindqvist, Chalmers University of Technology; Lars Göran Malmberg, Johan Boman, Johan Woxenius, and Mattias Hallquist, University of Gothenburg, Christer Forsgren, Stena Metall; Anders Carlberg, Vgregion; Carl Carlsson, Swedish Shipowners Association, and Axel Wenblad, Former GD National Board of Fisheries. Dan Strömberg, and Maria Svane, University of Gothenburg, have been invaluable during the course of the project and as editors of the publication. The report has been endorsed by the EPSD. Bo Samuelsson Chairman of EPSD
|
|
| 2. |
- Thomas, Jean-Baptiste, et al.
(författare)
-
A comparative environmental life cycle assessment of hatchery, cultivation, and preservation of the kelp Saccharina latissima
- 2021
-
Ingår i: Ices Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 78:1, s. 451-467
-
Tidskriftsartikel (refereegranskat)abstract
- Seaweed cultivation and processing industries could contribute to sustainable blue growth and the European bioeconomy. This article contributes a case study evaluation of environmental sustainability of preserved brown seaweed Saccharina latissima by means of environmental life cycle assessment of a pilot facility in Sweden. The study accounts for nutrient bioremediation and carbon capture and includes two alternative hatchery processes, a 2-ha longline cultivation, and four alternative preservation methods (hang-drying outdoors, heated air-cabinet drying, ensiling, and freezing). The study found that as a result of carbon capture and nitrogen and phosphorus uptake (bioremediation) by seaweed, more CO2 and PO4 equivalents are (temporarily) absorbed than emitted by the supply chain. The extent of emissions is most affected by preservation methods undertaken. Impact profiles of the supply chain show that the greatest impact shares result from freezing and air-cabinet drying, both the two most energy-intensive processes, followed by the cultivation infrastructure, highlighting strategic optimization opportunities. Hatchery processes, harvesting, and the low-energy ensilage and hang-drying outdoors were found to have relatively small impact shares. These findings presage the environmentally friendliness of seaweed-based products by documenting their potential to mitigate eutrophication and climate change, even when taking a life cycle perspective.
|
|
| 3. |
- Hörteborn, Axel, 1986, et al.
(författare)
-
Economic incentives and technological limitations govern environmental impact of LNG feeder vessels
- 2023
-
Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 429
-
Tidskriftsartikel (refereegranskat)abstract
- In the transition to sustainable shipping, Liquified Natural Gas (LNG), is proposed to play a role, reducing emissions of sulphur and nitrogen oxides, and particulate matter. However, LNG is a fossil fuel and there is an ongoing discussion regarding the extent of methane slip from ships operating on LNG, challenging the assumptions of LNG as a sustainable solution. Here we show another aspect to consider in the environmental assessment of shipping; LNG feeder vessels may spend as much as 25% of their time at sea just running the ship to ensure the pressure in the tanks are not exceeded, i.e., run time not directly attributed to the shipment of gas from one port or ship, to another. In other words, the economic incentives are currently allowing for roughly 32% increase of the ships’ operational emissions and discharges and increased navigational risks. Most coastal areas are heavily affected by anthropogenic activities and e.g., in the Baltic Sea there is consensus among the HELCOM member states that the input of nutrient and hazardous substances must be reduced. Even if the LNG feeder vessels are currently few, the possibility to reduce their environmental impact by 32% should be an attractive opportunity for future policy measures and investigation of technological solutions of the problem.
|
|
| 4. |
- Shahroozi, Zahra, 1992-
(författare)
-
Survivability control using data-driven approaches and reliability analysis for wave energy converters
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wave energy, with five times the energy density of wind and ten times the power density of solar, offers a compelling carbon-free electricity solution. Despite its advantages, ongoing debates surround the reliability and economic feasibility of wave energy converters (WECs). To address these challenges, this doctoral thesis is divided into four integral parts, focusing on optimizing the prediction horizon for power maximization, analyzing extreme waves' impact on system dynamics, ensuring reliability, and enhancing survivability in WECs.Part I emphasizes the critical importance of the prediction horizon for maximal power absorption in wave energy conversion. Using generic body shapes and modes, it explores the effect of dissipative losses, noise, filtering, amplitude constraints, and real-world wave parameters on the prediction horizon. Findings suggest achieving optimal power output may be possible with a relatively short prediction horizon, challenging traditional assumptions.Part II shifts focus to WEC system dynamics, analyzing extreme load scenarios. Based on a 1:30 scaled wave tank experiment, it establishes a robust experimental foundation, extending into numerical assessment of the WEC. Results underscore the importance of damping to alleviate peak forces. Investigating various wave representations highlights conservative characteristics of irregular waves, crucial for WEC design in extreme sea conditions.Part III explores the computational intricacies of environmental design load cases and fatigue analyses for critical mechanical components of the WEC. The analysis is conducted for hourly sea state damage and equivalent two-million-cycle loads. Finally, a comparison of safety factors between the ultimate limit state and fatigue limit state unfolds, illustrating the predominant influence of the ultimate limit state on point-absorber WEC design.Part IV, centers on elevating survivability strategies for WECs in extreme wave conditions. Three distinct controller system approaches leverage neural networks to predict and minimize the line force. Distinct variations emerge in each approach, spanning from rapid detection of optimal damping to integrating advanced neural network architectures into the control system with feedback. The incorporation of a controller system, refined through experimental data, showcases decreases in the line force, providing a practical mechanism for real-time force alleviation.This thesis aims to contribute uniquely to the goal of advancing wave energy conversion technology through extensive exploration.
|
|
| 5. |
|
|
| 6. |
- Svensson, Olle, 1967-
(författare)
-
Experimental results from the Lysekil Wave Power Research Site
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 7. |
- Nikopoulou, Zoi, 1975, et al.
(författare)
-
The role of a cap-and-trade market in reducing NOx and SOx emissions: Prospects and benefits for ships within the Northern European ECA
- 2013
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment. - : SAGE Publications. - 1475-0902 .- 2041-3084. ; 227:2, May 2013, s. 136-154
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a financial evaluation of alternative approaches to the abatement of NOx and SOx emissions from ships operating within the emission control area (ECA) of Northern Europe. The objective of this article is to assess the financial viability of a range of alternative technologies and fuel types, by accounting for revenue that might be generated from emissions trading within a cap-and-trade market for NOx and SOx emissions. Using a sample of real ships that operate within the ECA, NOx and SOx emissions for each alternative are estimated, and the revenue generated within a cap-and-trade system is calculated under a given set of assumptions. The results suggest that distillates are not an economic solution to meeting regulatory requirements. Conservative estimates of revenue generated within any prospective cap-and-trade system suggest that seawater scrubbers and Humid Air Motor (HAM) and Selective Catalytic Reduction (SCR) systems would all constitute financially attractive abatement options, while the use of liquefied natural gas (LNG) is the most financially attractive alternative. A cap-and-trade system is found to be highly efficacious in providing a relatively inexpensive source of finance for investments in improved environmental performance, as well as incentivizing such improvements, thereby removing any requirement for public sector support.
|
|
| 8. |
- Tillig, Fabian, 1984, et al.
(författare)
-
Design, operation and analysis of wind-assisted cargo ships
- 2020
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 211:1, s. 1-23
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents a novel approach to analytically capture aero- and hydrodynamic interaction effects on wind-assisted ships. Low aspect ratio wing theory is applied and modified to be used for the prediction of lift and drag forces of hulls sailing at drift angles. Aerodynamic interaction effects are captured by analytically solving the Navier-Stokes equation for incompressible, potential flow. The developed methods are implemented to a 4 degrees-of-freedom performance prediction model called “ShipCLEAN”, including a newly developed method for rpm control of Flettner rotors on a ship to maximize fuel savings. The accuracy of the model is proven by model- and full-scale verification. To present the variability of the model, two case study ships, a tanker and a RoRo, are equipped with a total of 11 different arrangements of Flettner rotors. The fuel savings and payback times are assessed using realistic weather from ships traveling on a Pacific Ocean route (tanker) and Baltic Sea route (RoRo). The results verify the importance of using a 4 degrees-of-freedom ship performance model, aero- and hydrodynamic interaction and the importance of controlling the rpm of each rotor individually. Fuel savings of 30% are achieved for the tanker, and 14% are achieved for the RoRo.
|
|
| 9. |
- Petersson, Jesper, 1974, et al.
(författare)
-
Defend, Retreat and Attack: Urban Waters and Valuation Practices
- 2022
-
Ingår i: Water Alternatives. - : Water Alternatives Association. - 1965-0175. ; 15:1, s. 175-192
-
Tidskriftsartikel (refereegranskat)abstract
- This paper explores the river landscapes and concomitant values resulting from tensions between flood management and visions of a River City. The aim is to contribute to an understanding of the management of urban waters as valuation practices. We regard valuation practices as co-constitutive of current and future river landscapes. Sweden’s second-largest city, Gothenburg, is located next to the sea, and the Göta River, Sweden’s largest water system, runs through it. Our empirical focus is on how this city approaches increasing risks of flooding. We explore three approaches that have been formulated in relation to flood management: defend, retreat and attack. We ask how these approaches are applied in the management of Göta River flooding and in the city’s vision of a future Gothenburg that embraces the river as a genuinely positive aspect of urban life. We present the case as a journey that takes us upstream from the river’s sea inlet port and through Gothenburg. During our kilometre by kilometre journey, the river’s appearance shifts. The varied river landscape mirrors the diversity in how its waters are valuated, both historically and in present times. The perception of urban waters is shaped by practices of valuation. These valuations are generative. They connect the value of water to other entities, actors, plans, activities and buildings, and they are thus key to the river landscapes that will eventually be realised. By way of conclusion, we identify a number of governance challenges that are particularly relevant to urban rivers.
|
|
| 10. |
- Andersson, Karin, 1952, et al.
(författare)
-
Shipping and the Environment - Improving Environmental Performance in Marine Transportation
- 2016
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- This book focuses on the interaction between shipping and the natural environment and how shipping can strive to become more sustainable. Readers are guided in marine environmental awareness, environmental regulations and abatement technologies to assist in decisions on strategy, policy and investments. You will get familiar with possible paths to improve environmental performance and, in the long term, to a sustainable shipping sector, based on an understanding of the sources and mechanisms of common impacts. You will also gain knowledge on emissions anddischarges from ships, prevention measures, environmental regulations, and methods and tools for environmental assessment. In addition, the book includes a chapter on thebackground to regulating pollution from ships. It is intended as a source of information for professionals connected to maritime activities as well as policy makers and interested public. It is also intended as a textbook in higher education academic programmes.
|
|
| 11. |
- Thies, Fabian, 1984, et al.
(författare)
-
Wind-assisted, electric, and pure wind propulsion - the path towards zero-emission RoRo ships
- 2023
-
Ingår i: Ships and Offshore Structures. - : Informa UK Limited. - 1754-212X .- 1744-5302. ; 18:8, s. 1229-1236
-
Tidskriftsartikel (refereegranskat)abstract
- Electrical and wind propulsion, together with energy stored in batteries and renewable energies harnessed onboard, can lead the way towards zero-emission ships. This study compares wind propulsion solutions and battery storage possibilities for a RoRo ship operating in the Baltic Sea. The ship energy systems simulation model ShipCLEAN is used to predict the performance of the zero-emission ship in real-life operating conditions. The study showcases how ships can be transferred from a conventional, diesel-powered to a zero-emission ship. For the zero-emission ship, all energy needed for auxiliaries and propulsion is taken from renewable sources onboard or from batteries. Challenges and opportunities, as well as necessary adaptions of the route and logistics, are discussed. Results of the study present which wind propulsion technology is the most suitable for the example RoRo ship, and how the installation of suitably sized battery packs for zero-emission operation affects the cargo capacity of the ship.
|
|
| 12. |
- Ishfaq, A., et al.
(författare)
-
Multifunctional design, feasibility and requirements for structural power composites in future electric air taxis
- 2023
-
Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 57:4, s. 817-827
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the viability of implementing multifunctional structural power composites in a four-seater air taxi, the CityAirbus. For a given specific energy of the power source, the cruise endurance can be approximately doubled by using structural power composites as opposed to conventional batteries. Replacing all the eligible composite mass and batteries with structural power composites can reduce the CityAirbus weight by 25%. To achieve the current design performance, the minimum required elastic modulus, strength, specific energy and power for the structural power composite are 54 GPa, 203 MPa, 74 Wh/kg and 376 W/kg, respectively: current state-of-the-art structural power composites are now approaching this level of performance. Hence, structural power composites are considered feasible for adoption in the urban air mobility sector and have the potential to improve endurance and facilitate commercialization. This paper also discusses several key challenges that must be addressed to realize the adoption of structural power composites in future electric air taxis.
|
|
| 13. |
- Lang, Xiao, 1992, et al.
(författare)
-
A semi-empirical model for ship speed loss prediction at head sea and its validation by full-scale measurements
- 2020
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 209
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a semi-empirical model to estimate a ship’s speed loss at head sea. In the model, the formulas to estimate a ship’s added resistance due to waves have been further developed to better consider the ship hull forms, in addition to other main particulars. Based on the model experimental tests of 11 ships in regular head waves, the new formulas have more flexible forms and can better fit the test results than other similar models. In addition, this model proposes a significant wave height based correction factor multiplied to the conventional integration to compute wave resistance in irregular waves. This factor is supposed to consider the impact of coupled ship motions in high waves on a ship’s added resistance due to waves. The model is validated by the full-scale measurement from two vessels, a PCTC and a chemical tanker. The encountered weather conditions along the sailing routes are extracted from the reanalysis metocean data. The results indicate that the proposed model can provide quite accurate predictions of ship speed loss in head sea operations.
|
|
| 14. |
|
|
| 15. |
- Andersson, Karin, 1952
(författare)
-
The shipping industry and the climate
- 2022
-
Ingår i: Sustainable Energy Systems on Ships: Novel Technologies for Low Carbon Shipping. - 9780128244715 ; , s. 3-25
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- As by 2020, the past six years, including 2020, are likely to be the six warmest years on record and the global mean temperature was 1.2°C above the preindustrial level [1]. International agreements, the Kyoto Protocol (1997) and the Paris agreement (2016), has set the aim to keep a global temperature rise during this century well below 2°C above pre-industrial levels. The anthropogenic inflow of GHGs to the atmosphere from the shipping industry was estimated by the IMO to totally around 2.5–3% of the global emissions in 2018 (or 1076 million tonnes). This is an increase by 9.6% since the previous study in 2014. The IMO projects the future emissions to increase from 1000 Mt CO2 in 2018 to 1000 to 1500 Mt CO2 in 2050 in a “Business as Usual”, BAU, scenario. Two years after the Paris agreement, the IMO adopted a vision, followed by a plan for implementation, in which a global goal of 50% reduction in GHG emissions from shipping by 2050 compared to 2008, and a total phase-out “within this century” is stated. Action from the IMO has started with a data collection system for fuel oil consumption. Ships of >5000 gross tonnage are required to collect consumption data fuel oil use and data on transport work. The European Union has started work on emission decrease with demands on Monitoring, Reporting and Verification of CO2 emissions from large ships (>5000 tonnes) using EU ports. Also here further measures are expected. At present here are many different initiatives, internationally, from countries as well as from shipping companies and shipowners to find ways towards “zero carbon shipping”. The different regulations and incentives introduced will help on the way, but still there is a need for more strict regulations or stronger incentives. The present initiatives give a large potential to make shipping and sea transport an important player also in a carbon neutral, sustainable society.
|
|
| 16. |
- Remouit, Flore, 1988-
(författare)
-
Automation of underwater operations on wave energy converters using remotely operated vehicles
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the last fifteen years, the Division of Electricity at Uppsala University has been developing a wave energy converter (WEC) concept. The concept is based on a point-absorbing buoy with a directly driven linear generator placed on the seabed. Several units are connected to a marine substation, whose role is to collect and smooth the power absorbed from the waves and then bring it to the shore through one single cable.A big challenge in the project is to reduce the costs related to the deployment and maintenance of the WECs and substation. Currently, those operations are performed by divers, which is costly and entail considerable risks. A possibility is to replace divers with automated solutions using small robots called remotely operated vehicles (ROVs). This PhD thesis proposes and analyses a method for deployment and maintenance of underwater devices with no use of diving operations.Existing ROVs need additional modules and equipment in order to carry out operations with the required force and precision. Typical missions are inspection, shackles or slings removal, valve closing, and cable connection. The latter demands especially high precision in the positioning: 5 mm in distance and 5◦ in heading angle. In addition, this operation involves forces up to 200 N. This combination power-precision is not reached by existing ROVs. This PhD thesis presents a positioning system for underwater robot to enable autonomous positioning of the vehicle before cable connection.The positioning system is composed of two green lasers and a monocular camera, and is based on image processing. Experimental results from laboratory testing show that the mean absolute error in distance measurement is as low as 6 mm at 0.7 m from the target, whereas the heading is minimized to 2◦. The computational time for the image processing is 13.6 ms per image, meaning the possibility of a 30 Hz measurement system. Used together with a closed-loop path-following unit, this positioning system can support autonomous docking. This PhD thesis presents the model of an autopilot and results from docking simulations, showing the performance of the positioning system used in closed-loop.
|
|
| 17. |
- Shahroozi, Zahra, et al.
(författare)
-
Considerations on prediction horizon and dissipative losses for wave energy converters
- 2021
-
Ingår i: IET Renewable Power Generation. - : Institution of Engineering and Technology. - 1752-1416 .- 1752-1424. ; 15:14, s. 3434-3458
-
Tidskriftsartikel (refereegranskat)abstract
- The non-causal optimal control law for wave energy converters leads to a requirement of predicting waves and wave forces over a future horizon. Using examples of generic body shapes and oscillation modes, we show through computations of the velocity reference trajectory how the length of prediction horizon required to reach the maximum power output depends on the level of dissipative losses in the conversion chain. The sensitivity to noise is discussed, and so is the use of filtering to improve performance when the available prediction horizon is short or predictions are inaccurate. Considerations are also made for amplitude constraints and other effects encountered in a real system. With realistic assumptions for the level of dissipative losses, results indicate that the prediction horizon needed to approach the maximum achievable power output for real systems ranges from only a few seconds up to about half a wave period, which is shorter than has generally been assumed earlier.
|
|
| 18. |
- Shahroozi, Zahra
(författare)
-
Prediction horizon requirement in control and extreme load analyses for survivability : Advancements to improve the performance of wave energy technologies
- 2021
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 19. |
- Walday, Mats, 1956, et al.
(författare)
-
SydVestlinken. Vurdering av traseer
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report we analyse the environmental impact of a proposed power cable laid through the marine national parks Ytre Hvaler and Kosterhavet. The report was commissioned by Statnett and Svenska kraftnät in connection with the project SydVestlinken. The report elucidates the potential environmental risks related to a realisation of the proposed cabel and how the project complies with national park regulations. Analyses are based on existing data and a review of technical and scientific literature. The analyses include estimates of uncertainty related to the degreevaluable species and habitats will be impacted. More targeted studies are needed to improve the precision in the impact assessment and ensure that the environment is sufficiently safeguarded.
|
|
| 20. |
- Lunde Hermansson, Anna, 1987, et al.
(författare)
-
Strong economic incentives of ship scrubbers promoting pollution
- 2024
-
Ingår i: Nature Sustainability. - Göteborg : IVL Svenska Miljöinstitutet. - 2398-9629. ; 7:6, s. 812-822
-
Tidskriftsartikel (refereegranskat)abstract
- In response to stricter regulations on ship air emissions, many shipowners have installed exhaust gas cleaning systems, known as scrubbers, allowing for use of cheap residual heavy fuel oil. Scrubbers produce large volumes of acidic and polluted water that is discharged to the sea. Due to environmental concerns, the use of scrubbers is being discussed within the International Maritime Organization. Real-world simulations of global scrubber-vessel activity, applying actual fuel costs and expenses related to scrubber operations, show that 51% of the global scrubber-fitted fleet reached economic break even by the end of 2022, with a surplus of €4.7 billion in 2019 euros. Within five years after installation, more than 95% of the ships with the most common scrubber systems reach break even. However, the marine ecotoxicity damage cost, from scrubber water discharge in the Baltic Sea Area 2014–2022, amounts to >€680 million in 2019 euros, showing that private economic interests come at the expense of marine environmental damage.
|
|
| 21. |
- Katsidoniotaki, Eirini, et al.
(författare)
-
Response of Point-Absorbing Wave Energy Conversion System in 50-Years Return Period Extreme Focused Waves
- 2021
-
Ingår i: Journal of Marine Science and Engineering. - : MDPI. - 2077-1312. ; 9:3
-
Tidskriftsartikel (refereegranskat)abstract
- This work evaluates the survivability of a point-absorbing wave energy converter at sea states along and inside the 50-year environmental contour for a selected-site in North Sea, by utilizing CFD simulations. Focused wave groups based on NewWave theory are used to model the extreme waves. The numerical breaking waves have been previously predicted by the analytical breaking criterion, showing that the latter provides an accurate estimate for the breaking state. The forces on key components of the device and the system’s dynamics are studied and compared. Slamming loads are identified in the interaction with extreme waves, particularly with breaking waves, and compared with the analytical formulas for slamming estimation as suggested by industrial standards. Considering the extreme wave characteristics, the accompanied phenomena and the resulting WEC’s response, this work contributes to the identification of the design-waves given the environmental contour of the selected site. The top-left side of the contour is identified as the more critical area as it consists of steep and high waves inducing significant nonlinear phenomena, resulting in high loads.
|
|
| 22. |
- Andersson, Johnn, 1983
(författare)
-
Blå energi – en strategisk innovationsagenda för marin energi
- 2013
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Marine energy can meet global environmental and societal challenges by supplying renewable energy to the world’s coastal areas. Sweden has the opportunity to create a future export industry, creating jobs and driving sustainable development.The world’s oceans contain vast amounts of renewable energy that can be harnessed from its waves, tides and ocean currents – so called marine energy. If the great potential is fully ex- ploited, marine energy can help mitigate large amounts of carbon emissions, while improving the security of energy supply in many coastal regions.Many different technology concepts for harnessing marine energy are being developed around the world. Most are still undergoing basic concept development and small-scale testing, while others have reached full-scale demonstration deployments. Marine energy has large potential to become a competitive alternative to other energy sources.In its vision for 2050, the European Ocean Energy Association highlights the opportunity to meet 15 percent of the projected European electricity demand and create 300 000 jobs. They will exist in the countries that have the courage to invest in this emerging industry today, enabling domestic companies to become suppliers of products and services to the world market.Sweden has what it takes to become an exporter of turnkey power plants, sub-systems, components, services and knowledge. To succeed, investments that meet the industry’s challenges are required.In this innovation agenda, a broad group of stakeholders launch the Swedish industry vision “Swedish companies supply products and services that enable harnessing the full potential of marine energy”, highlight the need for public support and give recommendations to public actors responsible for promoting innovation and sustainable development.RECOMMENDATIONS• Adopt a politically endorsed national strategy, describing national objectives and a road map. The strategy should be managed by a public agency and be developed during 2014, building on this innovation agenda.• Support a national collaboration platform, promoting the development of the Swed- ish marine energy industry. It should be established immediately and build on the ongoing Swedish collaboration initiative Ocean Energy Centre.• Support concept specific development and demonstration that benefit technologies in different development stages. It should be granted continuously and aligned with a na- tional strategy.• Support generic research and development, based on the industry’s short and long term needs. It should be granted continuously, aligned with
|
|
| 23. |
- Parwal, Arvind, et al.
(författare)
-
Grid impact and power quality assessment of wave energy parks: Different layouts and power penetrations using energy storage
- 2021
-
Ingår i: JOURNAL OF ENGINEERING-JOE. - : Institution of Engineering and Technology (IET). - 2051-3305. ; 2021:8, s. 415-428
-
Tidskriftsartikel (refereegranskat)abstract
- Power fluctuations induced by wave energy converters (WECs) may reflect negative impact on the power quality of the power grid. Assessing their impact is an important step to ensure the grid compliance level of the energy park. The IEC 61000-4-15 standard classifies the allowable disturbances in the grid. This study analysed and assessed the grid impact in terms of flicker, harmonic distortion and voltage variations. The assessments were performed without energy storage and compared when using the energy storage. A single WEC is emulated as an irregular power output of a real WEC using a combined model of power take-off in the Simulink model. Time series based on data obtained in earlier offshore experiments, conducted at the Lysekil research site in Sweden, is used to emulate a wave energy park (WEP) power in a land-based test rig in real-time power hardware-in-the-loop simulations. A total of three and ten WECs are emulated by introducing a time delay in the time series to investigate the grid impact in each layout. Flicker emissions, voltage variations, individual and total harmonics of the voltage at the connection point in each layout are studied and compared with the limits to be grid compliant for layouts of the WEP. In addition, voltage and current harmonics for the single WEC and individual harmonics in each phase of the voltage are measured and analysed to assess the compliance level of the WEP.
|
|
| 24. |
- Shahroozi, Zahra, et al.
(författare)
-
Investigation on the extreme peak mooring force distribution of a point absorber wave energy converter with and without a survivability control system
- 2023
-
Ingår i: Proceedings of the European Wave and Tidal Energy Conference (EWTEC). - : European Wave and Tidal Energy Conference. - 2706-6932 .- 2706-6940. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- To determine the optimal design of the wave energy converter (WEC) that can withstand extreme waveconditions, the short- and long-term extreme responses of the system need to be determined. This paper focuses on the extreme peak force distribution of the mooring force for a 1:30 scaled point absorber WEC. The basis of this analysis is the mooring force response obtained from a WEC-Sim model calibrated by wave tank experimental data. The extreme sea states have been chosen from a50-year environmental contour. Here, first, the long-term extreme response using the full sea state approach is obtained for three constant damping cases of the power take-off (PTO) system. Then, using a contour approach, the expected value of the extreme peak line (mooring) force distribution is computed for the sea states along an environmental contour. Further, for the most extremesea state, the extreme peak line force distribution is also computed where a survivability control system, based on a deep neural network (DNN), changes the PTO damping to minimize the peak mooring force in each zero up-crossing episode of surface elevation. The results show that in the absence of a control system, the zero PTO damping case is a conservative choice in the analysis of the long-term response and the design load. For the most extreme sea state along the environmental contour, the survivability control system slightly reduces the expected value of the extreme peak force distribution when compared with lower constant PTO damping configurations.
|
|
| 25. |
- Shahroozi, Zahra, et al.
(författare)
-
Neural network survivability approach of a wave energy converter considering uncertainties in the prediction of future knowledge
- 2024
-
Ingår i: Renewable energy. - : Elsevier. - 0960-1481 .- 1879-0682. ; 228
-
Tidskriftsartikel (refereegranskat)abstract
- To tune the wave energy converter (WEC) controller parameters such as damping to reduce the line force during extreme wave conditions, future knowledge of the line force is required.To achieve this, the incoming wave and system state should be predicted for a few seconds in the future. It is rather an arduous task to predict the future knowledge of waves and the system's dynamic when dealing with breaking and steep waves, and the system is subject to various nonlinear forces. The classical model-based control strategies often rely on linear assumptions to estimate the WEC dynamics for the sake of simplicity. Unlike the model-based, the data-driven approaches are free from modeling errors and the algorithms are trained over the true and noisy data to predict non-linear system behaviors.Using data-driven approaches, we are able to model nonlinear dynamics. However, new questions emerge on the accuracy of the future wave and system state predictions, and how this uncertainty propagates into the final prediction of the line force. As incorrect damping may lead to excessive line force and detrimental damage to the system, these are the knowledge gaps that need to be addressed.The main purpose of this paper is to answer these questions through a survivability strategy for wave energy converters by providing a realistic perspective on the implementation of the neural network approaches by accounting for the errors in the input data. For this purpose, a series of neural networks is designed that first predicts the surface elevation for 0.36 s ahead, i.e. corresponding to 2 s in the full-scale WEC. This future knowledge of the wave elevation is then used to predict the system state (i.e. power take-off (PTO) translator position) for the same prediction horizon based on the PTO damping. This information is then fed to a convolutional neural network (CNN) that predicts the peak line force 0.36 s ahead. Further, the sensitivity of the peak line force prediction to the uncertainties in the input data and the prediction horizon is analyzed. The neural network models are trained over the experimental data subjected to the extreme sea states for a point absorber wave energy converter. The results present a thorough analysis of the NN models’ performance.The results suggest that the accuracy of the surface elevation prediction has an insignificant independent effect on the peak force prediction model. However, these uncertainties reflect in the PTO translator position prediction, and the model is considerably sensitive to the accuracy of this prediction. This sensitivity nonetheless is less notable for higher PTO damping values. The prediction accuracy of the peak forces dropped by only about 7\% when the predicted input was used in the lower damping cases here, whereas, a larger drop was seen for the higher damping case.
|
|
