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Offshore deployments of marine energy converters
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.ORCID iD: 0000-0002-0289-5157
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The depletion warning of non-renewable resources, such as gas, coal and oil, and the imminent effects of climate change turned the attention to clean and fossil fuel-free generated electricity. University research groups worldwide are studying solar, wind, geothermal, biomass and ocean energy harvesting. The focus of this thesis is the wave and marine current energy researched at the division of Electricity at Uppsala University (UU). 

The main drawbacks that hinder the commercialization of marine energy converter devices is a high installation, operation, maintenance and decommissioning cost. Furthermore, these processes are highly weather dependent and thus, can be time consuming beyond planning. In this thesis, an evaluation of the cost, time and safety efficiency of the devices’ offshore deployment (both wave and marine current), and a comparative evaluation regarding the safety in the use of divers and remotely operated vehicles (ROVs) are conducted. Moreover, a risk analysis study for a common deployment barge while installing an UU wave energy converter (WEC) is presented with the aim to investigate the failure of the crane hoisting system.

The UU wave energy project have been initiated in 2001, and since then 14 WECs of various designs have been developed and deployed offshore, at the Lysekil research site (LRS), on the Swedish west coast and in Åland, Finland. The UU device is a point absorber with a linear generator power take off. It is secured on the seabed by a concrete gravity foundation. The absorbed wave energy is transmitted to shore through the marine substation (MS) where all the generators are interconnected. In 2008 an UU spin-off company, Seabased AB (SAB), was established and so far has developed and installed several WECs and two MSs, after the UU devices main principle. SAB deployments were conducted in Sotenäs, Sweden, at the Maren test site (MTS) in Norway; and in Ada Foah, Ghana. The active participation and the thorough study of the above deployments led to a cost, time and safety evaluation of the methods followed. Four main methods were identified and the most suitable one can be chosen depending on the deployment type, for example, for single or mass device deployment.

The first UU full scale marine current energy converter (MCEC) was constructed in 2007 at the Ångström Laboratory and deployed at Söderfors, in the river Dalälven in March 2013. The UU turbine is of a vertical axis type and is connected to a directly driven permanent magnet synchronous generator of a low-speed. With this deployment as an example, four MCEC installation methods were proposed and evaluated in terms of cost and time efficiency.

A comparative study on the use of divers and ROVs for the deployment and maintenance of WECs at the LRS has been carried out, showing the potential time and costs saved when using ROVs instead of divers in underwater operations. The main restrictions when using divers and ROVs were presented. Most importantly, the modelling introduced is generalized for most types of wave energy technologies, since it does not depend on the structure size or type.

Finally, a table of safe launch operation of a WEC is presented. In this table the safe, restrictive and prohibitive sea states are found for a single WEC deployment, using a barge and a crane placed on it. The table can be utilized as a guidance for offshore operations safety and can be extended for a variety of device types and vessels.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. , p. 79
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1792
Keywords [en]
offshore deployments, risk assessment, wave energy converter installation, marine current energy converter installation, economic efficiency, time efficiency, offshore operations, point absorber, hydrodynamic analysis, slack sling criterion, hoisting system failure.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-380861ISBN: 978-91-513-0623-0 (print)OAI: oai:DiVA.org:uu-380861DiVA, id: diva2:1301347
Public defence
2019-05-17, Häggsalen, 10132, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2019-04-24 Created: 2019-04-01 Last updated: 2019-06-17
List of papers
1. Offshore Deployments of Wave Energy Converters by Seabased Industry AB
Open this publication in new window or tab >>Offshore Deployments of Wave Energy Converters by Seabased Industry AB
2017 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 5, no 2, article id 15Article in journal (Refereed) Published
Abstract [en]

Since 2008, Seabased Industry AB (SIAB) has manufactured and deployed several units of wave energy converters (WECs) of different design. The WECs are linear generators with point absorber buoy systems that are placed on the seabed, mounted on a gravitation concrete foundation. These deployments have taken place in different areas, using different deployment vessels. Offshore deployments of WECs and underwater substations have so far been complicated procedures, that were both expensive and time-consuming. The focus of this paper is to discuss these deployments in terms of economy and time efficiency, as well as safety. Because seven vessels have been used to facilitate the deployments, an evaluation on the above basis is carried out for them. The main conclusions and certain solutions are presented for the various problems encountered during these deployments and the vessel choice is discussed. It is found that the offshore deployment process can be optimized in terms of cost, time efficiency and safety with a careful vessel choice, use of the latest available technologies and detailed planning and organizing.

Keywords
offshore deployment; wave energy converter; specialized vessel; underwater substation
National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-318633 (URN)10.3390/jmse5020015 (DOI)000423689700001 ()
Available from: 2017-03-27 Created: 2017-03-27 Last updated: 2019-04-01Bibliographically approved
2. Offshore Deployments of Wave Energy Converters by Uppsala University
Open this publication in new window or tab >>Offshore Deployments of Wave Energy Converters by Uppsala University
2017 (English)In: Article in journal (Refereed) Submitted
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-329835 (URN)
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2019-04-01
3. Marine Current Energy Converters deployments modelling
Open this publication in new window or tab >>Marine Current Energy Converters deployments modelling
(English)In: Article in journal (Other academic) Submitted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-380858 (URN)
Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-04-01
4. Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
Open this publication in new window or tab >>Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
Show others...
2018 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 6, no 2, article id 39Article in journal (Refereed) Published
Abstract [en]

Ocean renewable technologies have been rapidly developing over the past years. However, current high installation, operation, maintenance, and decommissioning costs are hindering these offshore technologies to reach a commercialization stage. In this paper we focus on the use of divers and remotely-operated vehicles during the installation and monitoring phase of wave energy converters. Methods and results are based on the wave energy converter system developed by Uppsala University, and our experience in offshore deployments obtained during the past eleven years. The complexity of underwater operations, carried out by either divers or remotely-operated vehicles, is emphasized. Three methods for the deployment of wave energy converters are economically and technically analyzed and compared: one using divers alone, a fully-automated approach using remotely-operated vehicles, and an intermediate approach, involving both divers and underwater vehicles. The monitoring of wave energy converters by robots is also studied, both in terms of costs and technical challenges. The results show that choosing an autonomous deployment method is more advantageous than a diver-assisted method in terms of operational time, but that numerous factors prevent the wide application of robotized operations. Technical solutions are presented to enable the use of remotely-operated vehicles instead of divers in ocean renewable technology operations. Economically, it is more efficient to use divers than autonomous vehicles for the deployment of six or fewer wave energy converters. From seven devices, remotely-operated vehicles become advantageous.

National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-348816 (URN)10.3390/jmse6020039 (DOI)000436558500011 ()
Funder
StandUpEU, FP7, Seventh Framework Programme, 607656Swedish Energy Agency
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2019-04-01Bibliographically approved
5. Risk assessment of deployment of an Uppsala University wave energy converter from a barge in different sea states.
Open this publication in new window or tab >>Risk assessment of deployment of an Uppsala University wave energy converter from a barge in different sea states.
(English)In: Article in journal (Other academic) Submitted
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-380859 (URN)
Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-04-01
6. Offshore Deployment of Point Absorbing Wave Energy Converters with a Direct Driven Linear Generator Power Take-Off at the Lysekil Test Site
Open this publication in new window or tab >>Offshore Deployment of Point Absorbing Wave Energy Converters with a Direct Driven Linear Generator Power Take-Off at the Lysekil Test Site
2014 (English)In: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 9A: Ocean Renewable Energy, 2014Conference paper, Published paper (Refereed)
Abstract [en]

Within the year 2013, four linear generators with point absorber buoy systems were deployed in the Lysekil test site. Until now, deployments of these point absorbing wave energy converters have been expensive, time consuming, complicated and raised safety issues. In the present paper, we focus on the analysis and optimization of the offshore deployment process of wave energy converters with a linear generator power take-off which has been constructed by Uppsala University. To address the crucial issues regarding the deployment difficulties, case study of previous offshore deployments at the Lysekil test site are presented regarding such parameters as safety, cost and time efficiency. It was discovered that the deployment process can be improved significantly, mainly by using new technologies, e.g., new specialized deployment vessels, underwater robots for inspections and for connecting cables and an automatized pressurizing process. Addressing the main deployment difficulties and constrains leads us to discovery of methods that makes offshore deployments more cost-efficient and faster, in a safety context.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering Ocean and River Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-222445 (URN)10.1115/OMAE2014-23396 (DOI)000363499000023 ()978-0-7918-4553-0 (ISBN)
Conference
Proceedings of the 33rd International Conference on Ocean, Offshore and Arctic Engineering, ASME 2014
Available from: 2014-04-11 Created: 2014-04-10 Last updated: 2019-04-01Bibliographically approved
7. Offshore Deployment of Marine Substation in the Lysekil Research Site
Open this publication in new window or tab >>Offshore Deployment of Marine Substation in the Lysekil Research Site
2015 (English)Conference paper, Published paper (Refereed)
Keywords
energy conversion; marine substation; offshore deployment; offshore deployment optimization; renewable energy.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-248539 (URN)
Conference
25th International Ocean and Polar Engineering Conference, ISOPE 2015, June 21-26, 2015, Kona, Big Island, Hawaii
Available from: 2015-03-31 Created: 2015-03-31 Last updated: 2019-04-01
8. Wave Energy Research at Uppsala University and The Lysekil Research Site, Sweden: A Status Update
Open this publication in new window or tab >>Wave Energy Research at Uppsala University and The Lysekil Research Site, Sweden: A Status Update
Show others...
2015 (English)Conference paper, Published paper (Refereed)
Abstract [en]

This paper provides a summarized status update ofthe Lysekil wave power project. The Lysekil project is coordinatedby the Div. of Electricity, Uppsala University since 2002, with theobjective to develop full-scale wave power converters (WEC). Theconcept is based on a linear synchronous generator (anchored tothe seabed) driven by a heaving point absorber. This WEC has nogearbox or other mechanical or hydraulic conversion systems,resulting in a simpler and robust power plant. Since 2006, 12 suchWECs have been build and tested at the research site located atthe west coast of Sweden. The last update includes a new andextended project permit, deployment of a new marine substation,tests of several concepts of heaving buoys, grid connection,improved measuring station, improved modelling of wave powerfarms, implementation of remote operated vehicles forunderwater cable connection, and comprehensive environmentalmonitoring studies.

Keywords
Wave energy, point absorber, experiments, arrays, generators, ROVs
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-265218 (URN)
Conference
Proceedings of the 11th European Wave and Tidal Energy Conference. Nantes, France, September 2015
Available from: 2015-10-26 Created: 2015-10-26 Last updated: 2019-08-19Bibliographically approved
9. Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
Open this publication in new window or tab >>Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
Show others...
2018 (English)Conference paper, Published paper (Refereed)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:uu:diva-361208 (URN)
Conference
Fifth International Conference on Electric Power and Energy Conversion Systems (EPECS 2018), Kitakyushu, Japan : April 23-25, 2018
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2019-08-19Bibliographically approved
10. Grid Integration and a Power Quality Assessment of a Wave Energy Park.
Open this publication in new window or tab >>Grid Integration and a Power Quality Assessment of a Wave Energy Park.
Show others...
(English)In: Article in journal (Other academic) Submitted
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-380860 (URN)
Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-04-01

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Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
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Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf