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Dynamic stability of an electricity generation system based on renewable energy
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Energy Storage)ORCID iD: 0000-0002-4350-5194
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Energy Storage)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Wave Power)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Marine Current Power)
Show others and affiliations
2011 (English)In: Proceedings of CIRED 2011 - the 21st International Conference and Exhibition on Electricity Distribution, CIRED - Congrès International des Réseaux Electriques de Distribution, 2011, 0940- p.Conference paper, Published paper (Refereed)
Abstract [en]

Renewable energy must be stored in order to make itreliable. Flywheels are capable of storing high amounts ofenergy and can also be used as power buffers, due to theirhigh power densities. This paper investigates a way tosmooth the power output from renewable energy converters(wave, wind and marine current) by adding a doublewoundflywheel energy storage to the system. Simulationsshow that a ramp-controlled flywheel energy storage woulddrastically smooth the short time power from a wave energyconverter but not be that appropriate for longer termenergy storage. The power quality enhancement producedby the addition of the flywheel to the system is alsosimulated and discussed.

Place, publisher, year, edition, pages
CIRED - Congrès International des Réseaux Electriques de Distribution, 2011. 0940- p.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-157071OAI: oai:DiVA.org:uu-157071DiVA: diva2:434402
Conference
CIRED 2011 - 21st International Conference and Exhibition on Electricity Distribution, June 6-9, Frankfurt am Main, Germany
Available from: 2011-08-15 Created: 2011-08-15 Last updated: 2016-04-19
In thesis
1. System Perspectives on Hydro-Kinetic Energy Conversion
Open this publication in new window or tab >>System Perspectives on Hydro-Kinetic Energy Conversion
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Free-flowing water currents such as tides and unregulated water courses could contribute to world electricity production given the emergence of robust technical solutions for extracting the energy. At Uppsala University, a concept for converting the energy in water currents to electricity using a vertical axis turbine with fixed blade-pitch and a direct-drive permanent magnet generator is studied.

Technological equipment for extracting energy from water currents can be studied at desktop to some extent, but physical realizations, first in a laboratory setting, and later in a natural aquatic setting, are necessary. For this reason, a laboratory generator has been constructed and evaluated, and an experimental setup comprising turbine, generator and control system has been constructed. The turbine and generator are to be deployed in the Dalälven River in Söderfors, and operated from an on-land control station. The author has worked with constructing and evaluating the low-speed laboratory generator, participated in the design and construction of the Söderfors generator, and designed and constructed the control system for Söderfors.

The generator design incorporates a low rotational speed, permanent magnets, and many poles, in order to adapt the generator to the nature of water currents. Simulations and experimental data for the laboratory prototype have been compared and show that the simulation tool used is adequate for design studies of this type of generator. The generator has also been shown to be able to operate with the intended turbine design and range of water velocities. The control system to be used in Söderfors has been tested in a laboratory environment. Simulations of the control system show that it should be able to operate the turbine and generator at the desired rotational speeds in water velocities up to about 1.8 m/s. Simulations of the system have also shown that maximizing system power output may not correspond with maximizing turbine power.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 976
Keyword
tidal energy, permanent magnet, direct-drive, in-stream power converter, load control, vertical axis turbine, renewable energy, engineering science
National Category
Energy Systems Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-181555 (URN)978-91-554-8479-8 (ISBN)
Public defence
2012-11-09, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2012-10-18 Created: 2012-09-26 Last updated: 2013-01-23Bibliographically approved
2. Flywheel in an all-electric propulsion system
Open this publication in new window or tab >>Flywheel in an all-electric propulsion system
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Energy storage is a crucial condition for both transportation purposes and for the use of electricity. Flywheels can be used as actual energy storage but also as power handling device. Their high power capacity compared to other means of storing electric energy makes them very convenient for smoothing power transients. These occur frequently in vehicles but also in the electric grid. In both these areas there is a lot to gain by reducing the power transients and irregularities.

The research conducted at Uppsala university and described in this thesis is focused on an all-electric propulsion system based on an electric flywheel with double stator windings. The flywheel is inserted in between the main energy storage (assumed to be a battery) and the traction motor in an electric vehicle. This system has been evaluated by simulations in a Matlab model, comparing two otherwise identical drivelines, one with and one without a flywheel.

The flywheel is shown to have several advantages for an all-electric propulsion system for a vehicle. The maximum power from the battery decreases more than ten times as the flywheel absorbs and supplies all the high power fluxes occuring at acceleration and braking. The battery delivers a low and almost constant power to the flywheel. The amount of batteries needed decreases whereas the battery lifetime and efficiency increases. Another benefit the flywheel configuration brings is a higher energy efficiency and hence less need for cooling.

The model has also been used to evaluate the flywheel functionality for an electric grid application. The power from renewable intermittent energy sources such as wave, wind and current power can be smoothened by the flywheel, making these energy sources more efficient and thereby competitive with a remaining high power quality in the electric grid.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2011. 50 p.
Series
Licentiate Thesis, Division of Electricity, Department of Engineering Sciences, ISSN 0349-8352
Keyword
Flywheel, electric vehicle, hybrid vehicle, power management, energy storage
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-222030 (URN)
Presentation
2011-06-10, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2014-04-09 Created: 2014-04-07 Last updated: 2014-04-09Bibliographically approved

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