| 1. |
- Chatzigiannakou, Maria Angeliki, et al.
(författare)
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Numerical analysis of an Uppsala University WEC deployment by a barge for different sea states
- 2020
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 205
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Tidskriftsartikel (refereegranskat)abstract
- Wave energy converters (WECs) have been deployed onshore, nearshore, and offshore to convert ocean wave movement into electricity. The exploitation of renewable energy sources has restrictions; in the case of wave energy, high installation, maintenance, and decommissioning costs have limited their commercial use. Moreover, these offshore operations can be compromised by safety issues. This paper draws attention to offshore operation safety of a WEC developed by Uppsala University. Specifically, this paper investigates what sea states are suitable for the safe deployment of a WEC from a barge. This study follows recommendations in DNV-RP-H103 for analysis of offshore operations, namely lifting through the wave zone. ANSYS Aqwa is used to find hydrodynamic forces acting on a typical barge, using frequency domain analysis. Based on these hydrodynamic simulation results and methodology given in DNV-RP-H103, tables are created to show the sea states that would allow for the safe installation of a WEC using a typical barge. Considered sea states have significant wave heights varying between 0 m and 3 m and the wave zero crossing periods varying between 3 s and 13 s. The WEC submersions are considered between 0 m and 7 m, i.e. when the WEC is in the air until it is fully submerged. © 2020 Elsevier Ltd
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| 2. |
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| 3. |
- Parwal, Arvind, et al.
(författare)
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Grid impact and power quality assessment of wave energy parks: Different layouts and power penetrations using energy storage
- 2021
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Ingår i: JOURNAL OF ENGINEERING-JOE. - : Institution of Engineering and Technology (IET). - 2051-3305. ; 2021:8, s. 415-428
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Tidskriftsartikel (refereegranskat)abstract
- Power fluctuations induced by wave energy converters (WECs) may reflect negative impact on the power quality of the power grid. Assessing their impact is an important step to ensure the grid compliance level of the energy park. The IEC 61000-4-15 standard classifies the allowable disturbances in the grid. This study analysed and assessed the grid impact in terms of flicker, harmonic distortion and voltage variations. The assessments were performed without energy storage and compared when using the energy storage. A single WEC is emulated as an irregular power output of a real WEC using a combined model of power take-off in the Simulink model. Time series based on data obtained in earlier offshore experiments, conducted at the Lysekil research site in Sweden, is used to emulate a wave energy park (WEP) power in a land-based test rig in real-time power hardware-in-the-loop simulations. A total of three and ten WECs are emulated by introducing a time delay in the time series to investigate the grid impact in each layout. Flicker emissions, voltage variations, individual and total harmonics of the voltage at the connection point in each layout are studied and compared with the limits to be grid compliant for layouts of the WEP. In addition, voltage and current harmonics for the single WEC and individual harmonics in each phase of the voltage are measured and analysed to assess the compliance level of the WEP.
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| 4. |
- Parwal, Arvind, et al.
(författare)
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Virtual Synchronous Generator Based Current Synchronous Detection Scheme for a Virtual Inertia Emulation in SmartGrids
- 2019
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Ingår i: Energy and Power Engineering. - : Scientific Research Publishing. - 1949-243X .- 1947-3818. ; 11:3, s. 99-131
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Tidskriftsartikel (refereegranskat)abstract
- Renewable energy sources, such as photovoltaicwind turbines, and wave power converters, use power converters to connect to the grid which causes a loss in rotational inertia. The attempt to meet the increasing energy demand means that the interest for the integration of renewable energy sources in the existing power system is growing, but such integration poses challenges to the operating stability. Power converters play a major role in the evolution of power system towards SmartGrids, by regulating as virtual synchronous ge-nerators. The concept of virtual synchronous generators requires an energy storage system with power converters to emulate virtual inertia similar to the dynamics of traditional synchronous generators. In this paper, a dynamic droop control for the estimation of fundamental reference sources is imple-mented in the control loop of the converter, including active and reactive power components acting as a mechanical input to the virtual synchronous generator and the virtual excitation controller. An inertia coefficient and a droop coefficient are implemented in the control loop. The proposed con-troller uses a current synchronous detection scheme to emulate a virtual iner-tia from the virtual synchronous generators. In this study, a wave energy converter as the power source is used and a power management of virtual synchronous generators to control the frequency deviation and the terminal voltage is implemented. The dynamic control scheme based on a current synchronous detection scheme is presented in detail with a power manage-ment control. Finally, we carried out numerical simulations and verified the scheme through the experimental results in a microgrid structure.
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| 5. |
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| 6. |
- Potapenko, Tatiana
(författare)
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Modelling of Ocean Wave Energy Conversion for Increased Power Absorption
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Earth is also called the blue planet, because more than 70 % of its surface is covered by water, mainly in oceans and seas. Wind blowing over the oceans is creating water waves, which can travel thousands of kilometers with just a small energy loss. Despite the abundant potential for the green energy market, wave energy is not yet exploited to the extent of wind and solar energies.There have been numerous attempts to convert wave energy into electricity. The wave energy converter, developed at Uppsala University, Sweden is of a point absorber type. The principal idea lies in utilizing a novel linear generator. The translator is a moving part inside the sub-merged linear generator and it is connected to a buoy, floating on the water surface. The buoy moves with the waves and the translator is dragged up and down relative to the stator. This reciprocal motion induces a voltage in the stator windings.The up-to-date stage of development for wave energy converters poses various issues. Still open challenges hold the technology away from commercial energy production. One of the main goals in wave energy research is to enhance the absorbed power for a single device, as well as for a wave power park of multiple wave energy converters. The power harvest can be increased in different ways, for example by optimizing the buoy, the generator or by implementing control on the operation of the device.This thesis focuses on studying wave energy converters in different wave climates by their power absorption. The main criteria influencing absorbed power are buoy size, weight on the system, damping force and available wave energy potential at the location of interest. The damping force can be computed by different approaches: constant optimal damping, resistive load (replicating passive control of currents in the stator windings) and RC-load (modeling a grid connected linear generator with an active rectification, such as phase angle compensation).Waves have a random nature. Therefore, the grid connection of the linear generator requires special solution. Power fluctuations of converted wave energy by the direct drive linear genera-tor may affect the integration into existing electrical grids. To study the connection of a single wave energy converter, as well as the wave park of three and ten devices, power hardware in the loop experiments have been carried out. The power quality analysis has been performed.Wave power has high potential and it can be integrated into the existing wind and solar energy production towards fully renewable microgrids. Yet, there is a chance of at least one quiet night during the year, when there are no wind and no waves. Estimation of frequency occurrence of absorbed power gives an insight into the regularity of such events. A case study in Hvide Sande, Denmark is presented. A mix of renewable energies (wind, solar and wave) is beneficial, as it gives a more stable energy supply with less variation in power production than when taken individually. Based on 30 years of historical data it is concluded, that the required battery size is sufficiently reduced for the renewable energy mix. The mix of wind, solar and wave has been shown to secure the lowest frequency of zero occurrences in power production and therefore is the most favorable choice for the future.
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| 7. |
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| 8. |
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| 9. |
- Potapenko, Tatiana, et al.
(författare)
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Renewable Energy Potential for Micro-Grid at Hvide Sande
- 2023
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Decarbonization of ports is a major goal to reduce their global carbon footprint. The port of Hvide Sande is located on the coast of the North Sea in Denmark and it has the potential to utilize various renewable energy sources. Wind and solar thermal parks are already installed there. Wave energy is an alternative to solar and wind energies and its advantage is the spatial concentration, predictability, and persistence. Heat to the town is provided by Hvide Sande Fjernvarme. In this work, it is investigated if the heat demand could be fully covered by renewable energies. Power profiles for each renewable energy resource were calculated using 30 years of re-analysis environmental data. Long, mid, and short term time series of power supply has been statistically and quantitatively examined. Considering the heat demand of Hvide Sande, the lowest frequency of zero occurrence in power generation can be ensured by the combination of wind, solar energy and wave. The article also estimated the capacity for Lithium-ion batteries. The optimal size of the battery is found by the bisection method. Finally, different combinations of renewable energy and demand as well as batteries are evaluated. The lowest zero occurrences in power production is met by the mix of three renewable energies. Also, the mix of three renewable energies significantly reduces the value of energy, required from the battery.
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| 10. |
- Potapenko, Tatiana
(författare)
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Wave energy converter: hydrodynamics and control
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Waves, just like wind and solar radiation, is a widely available renewable energy source. Waves are created when winds move across the sea surface. The estimated potential of wave energy is abundant, but the commercial harvesting technologies are still in their infancy. There are different wave energy converter designs, one of which is developed at Uppsala University and is based on a permanent magnet linear generator. A semi-submerged buoy on the water surface absorbs the energy of the wave and converts the mechanical energy into electricity with a direct drive linear generator.One of the main goals in wave energy research is to enhance the absorbed power for a single device and multiple devices in wave energy parks. The energy harvest can be increased in different ways: by optimizing the buoy, the generator, and/or by implementing control strategies. To assess the best optimization strategies numerical modeling is an inexpensive tool, aimed to predict the complex behavior of the system. This licentiate thesis focuses on the study of wave energy converters in irregular waves for testing sites, such as in Lysekil (Sweden) and Wave Hub (UK). The numerical model is used to analyze the wave energy conversion power performance. The hydrodynamic model involves radiation force approximation for a state-space model. It has been shown that a higher order of approximation can be achieved by vector fitting than by the transfer function fitting in the frequency domain, especially for the interaction of several bodies with the incident wave. Wave energy converter concepts are evaluated in terms of absorbed power for the resistive load connection, representing the passive control of the currents in the generator windings. Additionally, RC-load intends to model a grid-connected generator with active rectification, such that phase angle is compensated. Finally, a power-hardware-in-the-loop study of a grid-connected wave energy converter is presented. The current and voltage profiles of a grid-connected wave energy converter are shown with a suggestion on the implementation of RLC filter for power smoothing.
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