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Measurement System For Wave Energy Converter - Design And Implementation
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0001-6870-6729
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. Univ Southampton, Engn & Environm, Energy & Climate Change, Southampton, Hants, England..
2014 (English)In: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 9A: Ocean Renewable Energy, AMER SOC MECHANICAL ENGINEERS , 2014Conference paper, Published paper (Refereed)
Resource type
Text
Abstract [en]

A Wave Energy Converter (WEC) measurement system has been constructed and installed with the purpose to measure, log and evaluate the WEC's performance during operation at sea. The WEC is to be deployed at Uppsala University's wave power research site in Lysekil on the west coast of Sweden. In designing such a system the key research objectives has been (1) to study the risk of overheating due to high currents in the stator windings, (2) to evaluate how the WEC's outer structure withstands drag and bending forces from the buoy line and (3) to construct a detection system which indicates if water leaks into the generator. The measurement system was designed to collect data essential to study these key objectives. Transducers were used to measure: buoy line force, translator position, phase currents, bending and tensile strain on the generator hull, water level inside generator and the temperature at multiple places inside the generator. The measurement system has been installed and calibrated in the WEC. Furthermore, the design has been evaluated in lab experiments in order to verify the function and accuracy of the different measurements. This paper presents the underlying research objectives for developing the WEC generator measurement system, together with a description of the technical implementation.

Place, publisher, year, edition, pages
AMER SOC MECHANICAL ENGINEERS , 2014.
National Category
Energy Systems Ocean and River Engineering
Identifiers
URN: urn:nbn:se:uu:diva-272118ISI: 000363499000005ISBN: 978-0-7918-4553-0 (print)OAI: oai:DiVA.org:uu-272118DiVA: diva2:893061
Conference
33Rd International Conference On Ocean, Offshore And Arctic Engineering
Note

Första författaren har bytt efternamn till Ulvgård

Available from: 2016-01-12 Created: 2016-01-12 Last updated: 2017-09-28
In thesis
1. Cooling Strategies for Wave Power Conversion Systems
Open this publication in new window or tab >>Cooling Strategies for Wave Power Conversion Systems
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Division for Electricity of Uppsala University is developing a wave power concept. The energy of the ocean waves is harvested with wave energy converters, consisting of one buoy and one linear generator. The units are connected in a submerged substation. The mechanical design is kept as simple as possible to ensure reliability.

The submerged substation includes power electronics and different types of electrical power components. Due to the high cost of maintenance operations at sea, the reliability of electrical systems for offshore renewable energy is a major issue in the pursuit of making the electricity production economically viable. Therefore, proper thermal management is essential to avoid the components being damaged by excessive temperature increases.

The chosen cooling strategy is fully passive, and includes no fans. It has been applied in the second substation prototype with curved heatsinks mounted on the inner wall of the pressurized vessel. This strategy has been evaluated with a thermal model for the completed substation. First of all, 3D-CFD models were implemented for selected components of the electrical conversion system. The results from these submodels were used to build a lumped parameter model at the system level.

The comprehensive thermal study of the substation indicates that the rated power in the present configuration is around 170 kW. The critical components were identified. The transformers and the inverters are the limiting components for high DC-voltage and low DC-voltage respectively. The DC-voltage—an important parameter in the control strategy for the WEC—was shown to have the most significant effect on the temperature limitation.

As power diodes are the first step of conversion, they are subject to large power fluctuations. Therefore, we studied thermal cycling for these components. The results indicated that the junction undergoes repeated temperature cycles, where the amplitude increased with the square root of the absorbed power.

Finally, an array of generic heat sources was optimized. We designed an experimental setup to investigate conjugate natural convection on a vertical plate with flush-mounted heat sources. The influence of the heaters distribution was evaluated for different dissipated powers. Measurements were used for validation of a CFD model. We proposed optimal distributions for up to 36 heat sources. The cooling capacity was maximized while the used area was minimized.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1454
Keyword
Wave power, power conversion system, thermal management, power elctronics, passive cooling, natural convection.
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-306706 (URN)978-91-554-9759-0 (ISBN)
Public defence
2017-01-20, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Available from: 2016-12-21 Created: 2016-11-02 Last updated: 2016-12-28
2. Wave Energy Converters: An experimental approach to onshore testing, deployments and offshore monitoring
Open this publication in new window or tab >>Wave Energy Converters: An experimental approach to onshore testing, deployments and offshore monitoring
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The wave energy converter (WEC) concept developed at Uppsala University consists of a point absorbing buoy, directly connected to a permanent magnet linear generator. Since 2006, over a dozen full scale WECs have been deployed at the Lysekil Research Site, on the west coast of Sweden. Beyond the development of the WEC concept itself, the full scale approach enables, and requires, experimental and multidisciplinary research within several peripheral areas, such as instrumentation, offshore operations, and wave power infrastructure.

This thesis addresses technical challenges of testing, deploying and monitoring full scale WECs. It is divided accordingly into three topics: offshore measurement systems, onshore WEC testing and deployments. Each topic presents new or improved technical solutions to enable offshore wave power research.

For the offshore measurement systems, a new portable data acquisition unit was developed, together with a new sensor system to be installed inside the WEC. The developed system offers a cheap and flexible option for short term offshore measurement ventures, when or where site infrastructure is not available. The system has been developed and tested during both onshore and offshore experiments, with promising results.

On the topic of onshore WEC testing, the thesis presents an experimental approach for assessing the power take-off (PTO) damping of the WEC. In previous experimental studies, it has been measured via the generated electrical power, which neglects both mechanical losses and iron losses. Consequently, the full PTO force acting on the WEC has been underestimated. The thesis presents experimentally attained trends for the speed dependence of the PTO damping at different resistive loads, as measured from both generated electric power and from measurements of the buoy line force. A study was also performed on how the generator damping is affected by partial stator overlap, which varies with the translator position. In order to assess how the characterized damping behavior will affect the WEC operation at sea, two simulation case studies were performed.

Finally, the thesis presents a new WEC deployment method, which has been developed through several deployment trials. By using only a tugboat, a WEC unit is transported and deployed, together with its buoy, in less than half a day. The procedure has proven to be faster, cheaper and safer than the previously used methods.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 100 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1563
Keyword
wave power, ocean energy, linear generator, measurements, sensors, point absorber, offshore, PTO, force
National Category
Energy Engineering Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-329856 (URN)978-91-513-0077-1 (ISBN)
Public defence
2017-11-10, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2017-10-18 Created: 2017-09-21 Last updated: 2017-10-18

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Lindblad, LiselotteBaudoin, AntoineLeijon, Mats

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