Logo: to the web site of Uppsala University

uu.sePublications from Uppsala University
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
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
Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Show others and affiliations
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.

Place, publisher, year, edition, pages
2018. Vol. 6, no 2, article id 39
National Category
Marine Engineering
Identifiers
URN: urn:nbn:se:uu:diva-348816DOI: 10.3390/jmse6020039ISI: 000436558500011OAI: oai:DiVA.org:uu-348816DiVA, id: diva2:1198525
Funder
StandUpEU, FP7, Seventh Framework Programme, 607656Swedish Energy AgencyAvailable from: 2018-04-17 Created: 2018-04-17 Last updated: 2022-02-02Bibliographically approved
In thesis
1. Automation of underwater operations on wave energy converters using remotely operated vehicles
Open this publication in new window or tab >>Automation of underwater operations on wave energy converters using remotely operated vehicles
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 74
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1695
Keywords
Remotely Operated Vehicles, wave energy, WEC deployment, cable connection, optical positioning system, autonomous underwater docking
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Marine Engineering Ocean and River Engineering Energy Systems
Identifiers
urn:nbn:se:uu:diva-356565 (URN)978-91-513-0388-8 (ISBN)
Public defence
2018-09-21, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-08-22 Created: 2018-08-01 Last updated: 2018-08-28
2. Offshore deployments of marine energy converters
Open this publication in new window or tab >>Offshore deployments of marine energy converters
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
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:nbn:se:uu:diva-380861 (URN)978-91-513-0623-0 (ISBN)
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: 2020-05-15
3. Environmental Effects from Wave Power: Artificial Reefs and Incidental No-take Zones
Open this publication in new window or tab >>Environmental Effects from Wave Power: Artificial Reefs and Incidental No-take Zones
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Marine renewable technologies have rapidly been developing over the past decade. Wave power is one of the renewable sources and has the potential securing the renewable electricity production. However, all renewable energy extraction affects the environment in some way and for a true sustainable energy generation, environmental effects need to be investigated. Beside uncertain effects from the technologies to habitats or organisms e.g., collision risks, electromagnetic fields, noise, past studies have also shown benefits on diversity, size and abundance of species around marine renewable technologies as a result of habitat creation by the devices and fishery exclusion in designated offshore park areas.

This thesis deals with environmental effects from heaving point-absorber wave energy converters developed at Uppsala University and deployed on the Swedish west coast at the Lysekil research site and the Sotenäs Project wave power park over a period of four years. The scope was the investigation of artificial reef effects from wave power foundations on local mobile, mega and macrofauna during visual inspections using scuba diving on the first hand. On the second hand, the effects from the incidental no-take zone on decapods and two sea pen species were investigated applying cage fishing and ROV seabed surveys. A third focus was on environmental monitoring around MRE sites and monitoring of MRE installations, both in an experimental and theoretical approach.

In the Lysekil research site, the results highlight that abundance and diversity can be enhanced locally around wave power foundations compared to control areas. The abundance and size of decapods were not significantly different within the wave power park and up to a distance of 360 m outside of it. In the Sotenäs Project wave power park a positive effect on Nephrops norvegicus size and burrow density but not on abundance was found on a scale of up to 1230 m. Sea pen abundance was enhanced inside the wave power park. However, interannual variation was strong.

In conclusion, wave power foundations can influence abundance and diversity of marine organisms around foundations on a very local scale (meters). With the methods in this study, the investigations did not reveal strong effects on the abundance and size of decapods on a larger scale up to 1230 m away from foundations as a result of the no-take zone. However, a focus should be put on a further development of environmental monitoring routines around MRE sites and their evaluation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2022. p. 62
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2115
Keywords
Marine renewable energy, Wave power, Environmental monitoring, Artificial reef, No-take zone, Decapods, Nephrops norvegicus, ROV, Cage fishing
National Category
Ecology Natural Sciences Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:uu:diva-466694 (URN)978-91-513-1403-7 (ISBN)
Public defence
2022-03-24, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2022-03-01 Created: 2022-02-02 Last updated: 2022-03-15

Open Access in DiVA

fulltext(4460 kB)347 downloads
File information
File name FULLTEXT01.pdfFile size 4460 kBChecksum SHA-512
1de230b5671fad62c4763d3673451d053ff5c1a2499d372996c9842336085cefdd4cffc75940740b83146ab15a70fd0c3f724f0b95fe6d81769a800a10e00bea
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Authority records

Remouit, FloreChatzigiannakou, Maria-AngelikiBender, AnkeTemiz, IrinaSundberg, JanEngström, Jens

Search in DiVA

By author/editor
Remouit, FloreChatzigiannakou, Maria-AngelikiBender, AnkeTemiz, IrinaSundberg, JanEngström, Jens
By organisation
Electricity
In the same journal
Journal of Marine Science and Engineering
Marine Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 347 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 346 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
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