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Wireless System for Tidal Effect Compensation in the Lysekil Research Site
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.
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2012 (English)In: Proceedings of the ASME 31st International Conference on Ocean, Offshore and Arctic Engineering, vol. 7, 2012, 293-298 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes, firstly, the rope adjustment device for wave energy converters (WECs) to minimize the tidal effect on the electricity production and, secondly, a wireless communication network between point absorbing WECs in the Lysekil Research Site and a computer station at the Department of Engineering Sciences at Uppsala University. The device is driven by a motor that activates when the main water level deviates from the average. The adjustment is achieved through a screw that moves upwards during low tides and downwards during high tides. For the purpose of testing the device in the research site, a wireless connection between the buoy in the sea and a computer on land will be designed. A sensor located close to the research site monitors the sea water level and, every time a significant variation is registered, it sends wirelessly a signal to the data logger that controls the power to the motor The position of the screw is observed by a second sensor and the measurements are retrieved back to Uppsala via GSM connection. The full scale device is tested in the lab and it is demonstrated to work properly, requiring less than 750 W to lift and lower different loads. Moreover, the wireless communication network is designed and once it will be built, it will allow to recall and store data, send information from one node of the system to another, monitor the proper functioning of the device and modify the control as desired.

Place, publisher, year, edition, pages
2012. 293-298 p.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-190207DOI: 10.1115/OMAE2012-83361ISI: 000324507000036ISBN: 978-0-7918-4494-6 (print)OAI: oai:DiVA.org:uu-190207DiVA: diva2:583144
Conference
31st International Conference on Ocean, Offshore and Arctic Engineering, July 1-6, 2012 Rio de Janeiro, Brazil
Available from: 2013-01-07 Created: 2013-01-07 Last updated: 2016-10-06Bibliographically approved
In thesis
1. Sea Level Compensation System for Wave Energy Converters
Open this publication in new window or tab >>Sea Level Compensation System for Wave Energy Converters
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The wave energy converter developed at Uppsala University consists of a linear generator at the seabed driven by the motion of a buoy on the water surface. The energy absorbed by the generator is negatively affected by variations of the mean sea level caused by tides, changes in barometric pressure, strong winds, and storm surges.

The work presented in this doctoral thesis aims to investigate the losses in energy absorption for the present generation wave energy converter due to the effect of sea level variations, mainly caused by tides. This goal is achieved through the modeling of the interaction between the waves and the point absorber. An estimation of the economic cost that these losses imply is also made. Moreover, solutions on how to reduce the negative effect of sea level variations are discussed. To this end, two compensation systems which adjust the length of the connection line between the floater and the generator are designed, and the first prototype is built and tested near the Lysekil research site.

The theoretical study assesses the energy loss at about 400 coastal points all over the world and for one generator design. The results highlight critical locations where the need for a compensation system appears compelling. The same hydro-mechanic model is applied to a specific site, the Wave Hub on the west coast of Cornwall, United Kingdom, where the energy loss is calculated to be about 53 %. The experimental work led to the construction of a buoy equipped with a screw jack together with its control, measurement and communication systems. The prototype, suitable for sea level variations of small range, is tested and its performance evaluated. A second prototype, suitable for high range variations, is also designed and is currently under construction.

One main conclusion is that including the compensation systems in the design of the wave energy converter will increase the competitiveness of the technology from an economic point of view by decreasing its cost per kWh. The need for a cost-effective wave energy converter with increased survivability emphasizes the importance of the presented research and its future development.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 71 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1386
Keyword
Ocean energy, Tides, Linear generator, Point absorber, Offshore experiment, Hydro-mechanic modeling, Power absorption, Control system, Communication system, Measurement system, Lysekil research site, Wave Hub.
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-295603 (URN)978-91-554-9613-5 (ISBN)
External cooperation:
Public defence
2016-09-09, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2016-08-19 Created: 2016-06-08 Last updated: 2016-08-25
2. Grid Connection of Permanent Magnet Generator Based Renewable Energy Systems
Open this publication in new window or tab >>Grid Connection of Permanent Magnet Generator Based Renewable Energy Systems
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Renewable energy is harnessed from continuously replenishing natural processes. Some commonly known are sunlight, water, wind, tides, geothermal heat and various forms of biomass. The focus on renewable energy has over the past few decades intensified greatly. This thesis contributes to the research on developing renewable energy technologies, within the wind power, wave power and marine current power projects at the division of Electricity, Uppsala University. In this thesis grid connection of permanent magnet generator based renewable energy sources is evaluated.

A tap transformer based grid connection system has been constructed and experimentally evaluated for a vertical axis wind turbine. Full range variable speed operation of the turbine is enabled by using the different step-up ratios of a tap transformer. This removes the need for a DC/DC step or an active rectifier on the generator side of the full frequency converter and thereby reduces system complexity. Experiments and simulations of the system for variable speed operation are done and efficiency and harmonic content are evaluated. 

The work presented in the thesis has also contributed to the design, construction and evaluation of a full-scale offshore marine substation for wave power intended to grid connect a farm of wave energy converters. The function of the marine substation has been experimentally tested and the substation is ready for deployment. Results from the system verification are presented. Special focus is on the transformer losses and transformer in-rush currents.

A control and grid connection system for a vertical axis marine current energy converter has been designed and constructed. The grid connection is done with a back-to-back 2L-3L system with a three level cascaded H-bridge converter grid side. The system has been tested in the laboratory and is ready to be installed at the experimental site. Results from the laboratory testing of the system are presented.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 79 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1436
Keyword
VAWT, H-rotor, Tap Transformer, Cascaded H-bridge Multi-Level, Renewable Energy, Wind power, Wave power, Marine Current Power
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-304659 (URN)978-91-554-9712-5 (ISBN)
Public defence
2016-11-25, Polhemsalen, 10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Projects
Wind PowerWave PowerMarine Currnet Power
Available from: 2016-11-03 Created: 2016-10-06 Last updated: 2016-11-16Bibliographically approved

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Castellucci, ValeriaWaters, RafaelApelfröjd, SenadLeijon, Mats

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