| 1. |
- Ayob, Mohd Nasir, et al.
(författare)
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A remotely controlled sea level compensation system for wave energy converters
- 2019
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 12:10
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Tidskriftsartikel (refereegranskat)abstract
- The working principle of the wave energy converter (WEC) developed at Uppsala University (UU) is based on a heaving point absorber with a linear generator. The generator is placed on the seafloor and is connected via a steel wire to a buoy floating on the surface of the sea. The generator produces optimal power when the translator's oscillations are centered with respect to the stator. However, due to the tides or other changes in sea level, the translator's oscillations may shift towards the upper or lower limit of the generator's stroke length, resulting in a limited stroke and a consequent reduction in power production. A compensator has been designed and developed in order to keep the generator's translator centered, thus compensating for sea level variations. This paper presents experimental tests of the compensator in a lab environment. The wire adjustments are based on online sea level data obtained from the Swedish Meteorological and Hydrological Institute (SMHI). The objective of the study was to evaluate and optimize the control and communication system of the device. As the device will be self-powered with solar and wave energy, the paper also includes estimations of the power consumption and a control strategy to minimize the energy requirements of the whole system. The application of the device in a location with high tides, such as Wave Hub, was analyzed based on offline tidal data. The results show that the compensator can minimize the negative effects of sea level variations on the power production at the WEC. Although the wave energy concept of UU is used in this study, the developed system is also applicable to other WECs for which the line length between seabed and surface needs to be adjusted.
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| 2. |
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| 3. |
- Ayob, Mohd Nasir, et al.
(författare)
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Small-Scale Renewable Energy Converters for Battery Charging
- 2018
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Ingår i: Journal of Marine Science and Engineering. - : MDPI. - 2077-1312. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, small-scale electricity generation in the buoy is needed to power a tidal compensating system designed to increase the performance of the WEC in areas with high tides. The two considered and modeled concepts are an oscillating water column (OWC) and a heaving point absorber. The results indicate that the OWC is too small for the task and does not produce enough energy. On the other hand, the results show that a hybrid system composed of a small heaving point absorber combined with a solar energy system would be able to provide a requested minimum power of around 37.7W on average year around. The WEC and solar panel complement each other, as the WEC produces enough energy by itself during wintertime (but not in the summer), while the solar panel produces enough energy in the summer (but not in the winter).
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| 4. |
- Ayob, Mohd Nasir, et al.
(författare)
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Tidal Effect Compensation System Design for High Range Sea Level Variations
- 2015
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Konferensbidrag (refereegranskat)abstract
- The working principle of the wave energy converter (WEC) from Uppsala University is a heaving point absorber with directly driven linear generator placed on the seabed. The heave motion of the buoy is transmitted to the generator via a steel cable. When tides occur, the sea level changes, and thus making the WEC works below optimal condition. This system is designed so that the WEC is able to work at sea level variation up to 8 meters. A compensation system is designed to continuously make the WEC work in its optimal condition even at different sea levels. We present a mechanical system and its control algorithm that monitor and control the length of the connecting line. The connecting line is consist of a steel wire and a steel chain connected together. The mechanical part of the system is the winch that retracts or releases the steel chain that connects the translator and the buoy at the water surface. The rotation of the winch is controlled by a motor with the help of microcontrollers and several sensors for accuracy and feedback. The result from simulation showed that the system works fine. The approach of compensating the wire length connecting the buoy and the translator allow more flexibility to WEC to work in the area with high sea level variation.
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| 5. |
- Ayob, Mohd Nasir, et al.
(författare)
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Wave energy potential and 1-50 TWh scenarios for the Nordic synchronous grid
- 2017
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 101, s. 462-466
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Tidskriftsartikel (refereegranskat)abstract
- This study estimates the wave energy potential along the coasts of the Nordic countries with the Nordicsynchronous grid as a chosen boundary. A model for wave farm allocation was developed and applied to achieve annual energy production targets of 1 TWh, 3 TWh, 10 TWh and 50 TWh. The study is based on 10 years of data, from 2005 to 2014, from the European Center for Medium-Range Weather Forecasts. Data from a total of 728 coordinate points along the Nordic countries, with a 0.125° x 0.125° spatial resolution, were considered. An algorithm was developed to generate the scenarios, to estimate the installed capacity of wave farms at different locations along the coasts, and to measure the physical space required by the farms. This analysis of the four energy target scenarios resulted in a required installed capacity of 337 MW, 1.02 GW, 3.42 GW and 17.09 GW, covering a stretch of the total coast of 0.4, 1.2, 3.8 and 18.9% respectively. The total annual wave energy resource for the Nordic countries is determined at 590 TWh, most of which is available along the Norwegian coast.
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| 6. |
- Castellucci, Valeria, et al.
(författare)
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Algorithm for the Calculation of the Translator Position in Permanent Magnet Linear Generators
- 2014
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 6:6, s. 063102-
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Tidskriftsartikel (refereegranskat)abstract
- A permanent magnet linear generator for direct drive wave energy converters is a suitable power take-off system for ocean wave energy extraction, especially when coupled with a point absorbing buoy via a connection line. The performance of the linear generator is affected by the excursion of the translator along the stator. The optimal stroke is achieved when the midpoint of the oscillations coincides with the center of the stator. However, sea level changes due to, e.g., tides will shift these oscillations. This paper proposes a model able to detect the position of the translator from the generator output voltage. The algorithm will be integrated in the control system of a mechanical device that adjusts the length of the connection line in order to center the average position of the translator with the center of the stator. Thereby, the output power from the wave energy converter increases, and the mechanical stresses on the hull of the generator decrease. The results obtained by the model show good agreement with the experimental results from two linear generators, L2 and L3, deployed in the Lysekil wave energy research site, Sweden. The theoretical results differ from the experimental results by −4 mm for L2 and 21 mm for L3 with a standard deviation of 27 mm and 31 mm, respectively.
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| 7. |
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| 8. |
- Castellucci, Valeria, et al.
(författare)
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Impact of Tidal Level Variations on the Wave Energy Absorption at Wave Hub
- 2016
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 9:10
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Tidskriftsartikel (refereegranskat)abstract
- The energy absorption of the wave energy converters (WEC) characterized by a limited stroke length - like the point absorbers developed at Uppsala University-depends on the sea level variation at the deployment site. In coastal areas characterized by high tidal ranges, the daily energy production of the generators is not optimal. The study presented in this paper quantifies the effects of the changing sea level at the Wave Hub test site, located at the south-west coast of England. This area is strongly affected by tides: the tidal height calculated as the difference between the Mean High Water Spring and the Mean Low Water Spring in 2014 was about 6.6 m. The results are obtained from a hydro-mechanic model that analyzes the behaviour of the point absorber at the Wave Hub, taking into account the sea state occurrence scatter diagram and the tidal time series at the site. It turns out that the impact of the tide decreases the energy absorption by 53%. For this reason, the need for a tidal compensation system to be included in the design of the WEC becomes compelling. The economic advantages are evaluated for different scenarios: the economic analysis proposed within the paper allows an educated guess to be made on the profits. The alternative of extending the stroke length of the WEC is investigated, and the gain in energy absorption is estimated.
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| 9. |
- Castellucci, Valeria, et al.
(författare)
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Influence of Sea State and Tidal Height on Wave Power Absorption
- 2017
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Ingår i: IEEE Journal of Oceanic Engineering. - 0364-9059 .- 1558-1691. ; 42:3, s. 566-573
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Tidskriftsartikel (refereegranskat)abstract
- The wave energy converter developed at Uppsala University (Uppsala, Sweden) consists of a linear generator placed on the seabed and driven by the motion of a buoy on the water surface. The buoy is connected to the moving part of the linear generator, the translator, which is made of ferrite magnets. The translator moves vertically inducing voltage in the windings of a fixed component, the so-called stator. The energy conversion of the linear generator is affected by the sea state and by variations of mean sea level. The sea state influences the speed and the stroke length of the translator, while the variation of tidal level shifts the average position of the translator with respect to the center of the stator. The aim of this study is to evaluate the energy absorption of the wave energy converter at different locations around the world. This goal is achieved by developing a hydromechanic model which analyses the optimum generator damping factor for different wave climates and the power absorbed by the generator, given a fixed geometry of the buoy and a fixed stroke length of the translator. Economic considerations regarding the optimization of the damping factor are included within the paper. The results suggest a nominal damping factor and show the power absorption losses at various locations, each of them characterized by a different wave climate and tidal range. The power losses reach up to 67% and in many locations a tidal compensation system, included in the design of the wave energy converter, is strongly motivated.
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| 10. |
- Castellucci, Valeria, et al.
(författare)
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Nearshore Tests of the Tidal Compensation System for Point-Absorbing Wave Energy Converters
- 2015
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:4, s. 3272-3291
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Tidskriftsartikel (refereegranskat)abstract
- The power production of the linear generator wave energy converter developed at Uppsala University is affected by variations of mean sea level. The reason is that these variations change the distance between the point absorber located on the surface and the linear generator located on the seabed. This shifts the average position of the translator with respect to the center of the stator, thereby reducing the generator output power. A device mounted on the point absorber that compensates for tides of small range by regulating the length of the connection line between the buoy at the surface and the linear generator has been constructed and tested. This paper describes the electro-mechanical, measurement, communication and control systems installed on the buoy and shows the results obtained before its connection to the generator. The adjustment of the line was achieved through a linear actuator, which shortens the line during low tides and vice versa. The motor that drives the mechanical device was activated remotely via SMS. The measurement system that was mounted on the buoy consisted of current and voltage sensors, accelerometers, strain gauges and inductive and laser sensors. The data collected were transferred via Internet to a Dropbox server. As described within the paper, after the calibration of the sensors, the buoy was assembled and tested in the waters of Lysekil harbor, a few kilometers from the Uppsala University research site. Moreover, the performance of the sensors, the motion of the mechanical device, the power consumption, the current control strategy and the communication system are discussed.
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| 11. |
- Castellucci, Valeria, et al.
(författare)
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Potential of Load Shifting in a Parking Garage with Electric Vehicle Chargers, Local Energy Production and Storage
- 2022
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Ingår i: World Electric Vehicle Journal. - : MDPI. - 2032-6653. ; 13:9
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Tidskriftsartikel (refereegranskat)abstract
- The electrification of the transport sector is of crucial importance for a successful transition to a fossil-free society. However, the electricity grid constitutes a bottleneck. This article provides a case study based on a real-world parking garage with a smart grid infrastructure, called Dansmästaren. The analysis shows how renewable energy sources, energy storage technologies, and smart charging of electric vehicles can smooth out the load curve of the parking garage and relieve the electric grid during peak hours. Dansmästaren is located in Uppsala, Sweden, and equipped with 60 charging points for electric vehicles, a PV system, and a battery storage system. The study utilizes an energy flow model to show the potential of a realistically dimensioned smart energy system, that can benefit the parking facility in itself and the local distribution grid in a city, Uppsala, with grid capacity challenges. The results suggest that the parking garage demand on the local grid can be significantly lowered by smarter control of its relatively small battery energy storage. Moreover, further smart control strategies can decrease demand up to 60% during high load hours while still guaranteeing fully charged vehicles at departure in near future scenarios. The study also shows that peak shaving strategies can lower the maximum peaks by up to 79%. A better understanding of the potential of public infrastructures for electric vehicle charging helps to increase knowledge on how they can contribute to more sustainable cities and a fossil-free society.
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| 12. |
- Castellucci, Valeria
(författare)
-
Sea Level Compensation System for Wave Energy Converters
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 13. |
- Castellucci, Valeria, et al.
(författare)
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Sea level variability in the Swedish Exclusive Economic Zone and adjacent seawaters : influence on a point absorbing wave energy converter
- 2019
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Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 15, s. 1517-1529
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Tidskriftsartikel (refereegranskat)abstract
- Low-frequency sea level variability can be a critical factor for several wave energy converter (WEC) systems, for instance, linear systems with a limited stroke length. Consequently, when investigating suitable areas for deployment of those WEC systems, sea level variability should be taken into account. In order to facilitate wave energy developers finding the most suitable areas for wave energy park installations, this paper describes a study that gives them additional information by exploring the annual and monthly variability of the sea level in the Baltic Sea and adjacent seawaters, with a focus on the Swedish Exclusive Economic Zone. Overall, 10 years of reanalysis data from the Copernicus project have been used to conduct this investigation. The results are presented by means of maps showing the maximum range and the standard deviation of the sea level with a horizontal spatial resolution of about 1 km. A case study illustrates how the results can be used by the WEC developers to limit the energy absorption loss of their devices due to sea level variation. Depending on the WEC technology one wants to examine, the results lead to different conclusions. For the Uppsala point absorber L12 and the sea state considered in the case study, the most suitable sites where to deploy WEC parks from a sea level variation viewpoint are found in the Gotland basins and in the Bothnian Sea, where the energy loss due to sea level variations is negligible.
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| 14. |
- Castellucci, Valeria, et al.
(författare)
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Tidal effect compensation system for point absorbing wave energy converters
- 2013
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 51, s. 247-254
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies show that there is a correlation between water level and energy absorption values for the studied wave energy converters: the absorption decreases when the water levels deviate from average. The situation appears during tides when the water level changes significantly. The main objective of the paper is to present a first attempt to increase the energy absorption during tides by designing and realizing a small-scale model of a point absorber equipped with a device that is able to adjust the length of the rope connected to the generator. The adjustment is achieved by a screw that moves upwards in the presence of low tides and downwards in the presence of high tides. Numerical results as well as experimental tests suggest that the solution adopted to minimize the tidal effect on the power generation shows potential for further development.
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| 15. |
- Castellucci, Valeria, et al.
(författare)
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Wireless System for Tidal Effect Compensation in the Lysekil Research Site
- 2012
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Ingår i: Proceedings of the ASME 31st International Conference on Ocean, Offshore and Arctic Engineering, vol. 7. - 9780791844946 ; , s. 293-298
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 16. |
- Ekergård, Boel, et al.
(författare)
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Axial Force Damper in a Linear Wave Energy Converter
- 2013
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Ingår i: Development and Applications of Oceanic Engineering (DAOE). - 2325-3762. ; 2:2, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study on the axial force damper in a wave energy converter. The converter itself consists of a linear generator placed on the ocean floor connected to a buoy at the ocean surface. As the development of the complete system goes forward, the economical perspective becomes more and more important. In order to ensure an economically viable alternative to the electric energy conversion, the costs associated with the use of materials have to be reduced while the survivability of the wave power unit has to be prolonged. The study presented in this paper increases the knowledge on axial forces and illustrates the damping system required to prevent the failure of the hull which houses the generator. The results are aimed to be utilized in the future design of wave energy converters and influence the choice of materials, the total costs and prolong the survivability of the wave energy converters in harsh wave climates.
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| 17. |
- Flygare, Carl, et al.
(författare)
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Correlation as a method to assess electricity users' contributions to grid peak loads : A case study
- 2024
-
Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 288
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Tidskriftsartikel (refereegranskat)abstract
- Flexibility has increasingly gained attention within the field of electrification and energy transition where a common objective is to reduce the electricity consumption peaks. However, flexibility can increase the risk of grid congestion depending on where and when and it is used, thus an overall system perspective needs to be considered to ensure an effective energy transition. This paper presents a framework to assess electricity users' contributions to grid load peaks by splitting electricity consumption data into subsets based on time and temperature. The data in each subset is separately correlated with the grid load using three correlation measures to assess how the user's consumption changes at the same time as typical grid peak loads occur. The framework is implemented on four different types of business activities at Uppsala municipality in Sweden, which is a large public entity, to explore their behaviors and assess their grid peak load contributions. The results of this study conclude that all four activities generally contribute to the grid peak loads, but that differences exist. These differences are not visible without splitting the data, and not doing so can lead to unrepresentative conclusions. The presented framework can identify activities that contribute the most to unfavorable grid peaks, providing a tool for decision-makers to enable an accelerated energy transition.
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| 18. |
- Flygare, Carl, 1988-, et al.
(författare)
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The potential impact of a mobility house on a congested distribution grid – a case study in Uppsala, Sweden
- 2022
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Ingår i: CIRED Porto Workshop 2022: E-mobility and power distribution systems. - London : IEEE.
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Konferensbidrag (refereegranskat)abstract
- The distribution grid in Uppsala, Sweden, has during the last years experienced an increasing number of hours with congestion, and as the city and number of EVs are growing new solutions are needed to not worsen this problem. Uppsala Municipality is planning a series of so-called “mobility houses” which will act as a hub for transportation while, at the same time, supporting the transition to a fossil-free energy system. Dansmästaren – the first mobility house in Uppsala – was built in 2020 and this paper describes its parking garage's main energy system parts, giving a brief introduction and analysis of each and their potential effect on Dansmästaren's grid impact. Dansmästaren has the potential to control its load on the grid, but it is essential to collect more data and analyze when flexibility is of most importance. Future studies suggest analyzing Dansmästaren's systems in more detail and developing a more advanced energy management system.
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| 19. |
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| 20. |
- Giassi, Marianna, et al.
(författare)
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Economical layout optimization of wave energy parks clustered in electrical subsystems
- 2020
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Ingår i: Applied Ocean Research. - : Elsevier. - 0141-1187 .- 1879-1549. ; 101
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Tidskriftsartikel (refereegranskat)abstract
- To obtain a maximum power output and minimized capital and operational costs, the layout of wave energyparks needs to be optimally designed. An economical model for large-scale wave energy systems is built andmerged into an evolutionary optimization routine for arrays of point-absorbing energy converters. The modelincludes all the parameters that affect the total system revenue such as electrical cable lengths, distance fromgrid connection point, number of substations and hydrodynamic interaction among the devices, with the goal tofind the optimal layout which minimizes the levelized cost of electricity. Converters inside the park are groupedin clusters via a k-means clustering algorithm, which allows to minimize the intra-array cable length under theinput of real wave climates. The results show that the hydrodynamical interaction has a large impact on theoptimal design of wave energy parks, and that the length of the intra-array cable does not play a significant rolein the economical layout optimization routine for the studied wave energy park system.
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| 21. |
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| 22. |
- Hai, Ling, et al.
(författare)
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Force in the connection line for a wave energy converter : simulation and experimental setup
- 2014
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Ingår i: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 9A. - San Francisco, USA. - 9780791845530
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Konferensbidrag (refereegranskat)abstract
- In order to capture ocean wave energy and transform it into electric energy, Uppsala University has developed a point absorber wave energy converter (AVEC) for electricity production. For a better understanding of a torus shaped buoy's performance, this paper conducts a force analysis under linear conditions, to investigate the hydrodynamic characteristic and line force differences between the torus buoy that is going to be deployed, and two similar cylindrical buoys. The result reveals the line force fromthis torus buoy is roughly 5% larger than from cylindrical buoys for the most energy dense wave climate in Lysekil test site, and negative added mass phenomena won't have a significant impact for the line force. To measure the line force, a force measurement system has been designed. A detailed description is given on the design of the 500 kN force measurement system, and the major differences compared with former force measurement systems. Onshore test result has also been presented. With the force measurement experiment, hydrodynamic analysis for torus buoy can be validated when the system performs linearly, and extreme force for storm weather can be monitored to provide information for future WEC structure's mechanical design.
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| 23. |
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| 24. |
- Hong, Yue, et al.
(författare)
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Linear generator-based wave energy converter model with experimental verification and three loading strategies
- 2016
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Ingår i: IET Renewable Power Generation. - : Institution of Engineering and Technology (IET). - 1752-1416 .- 1752-1424. ; 10:3, s. 349-359
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Tidskriftsartikel (refereegranskat)abstract
- Within the Lysekil wave energy research project at the Swedish west coast, more than ten Wave Energy Converters (WECs) prototypes have been developed and installed in an ocean based test site. Since 2006 various experiments have been conducted and the generated electricity was delivered to shore at a nearby island. While experiments are essential for the development of wave energy converters, theoretical studies and simulations are an important complement – not only in the search for advanced designs with higher efficiency, but also for improving the economic viability of the studied concepts. In this paper a WEC model is presented. The model consists of three subsystems: i) the hydrodynamic source, ii) the linear generator model, and iii) the electrical conversion system. After the validation with the experimental results at the research site, the generator model is connected to three passive load strategies – linear resistive load, passive rectification and resonance circuit. The paper focuses on analysing the operation of the model coupled with three load cases. The results prove that the WEC model correctly simulates the linear generator developed in the Lysekil Project. Moreover, the comparison among different load cases is made and discussed. The results gives an indication of the efficiency of energy production as well as the force ripples and resulting mechanical loads on the wave energy converters.
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| 25. |
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| 26. |
- Leijon, Jennifer, 1990-, et al.
(författare)
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An Analysis of Vehicle-to-Grid in Sweden Using MATLAB/Simulink
- 2024
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Ingår i: World Electric Vehicle Journal. - : MDPI. - 2032-6653. ; 15:4, s. 153-153
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Tidskriftsartikel (refereegranskat)abstract
- With more electric vehicles introduced in society, there is a need for the further implementation of charging infrastructure. Innovation in electromobility may result in new charging and discharging strategies, including concepts such as smart charging and vehicle-to-grid. This article provides an overview of vehicle charging and discharging innovations with a cable connection. A MATLAB/Simulink model is developed to show the difference between an electric vehicle with and without the vehicle-to-grid capabilities for electricity grid prices estimated for Sweden for three different electric vehicle user profiles and four different electric vehicle models. The result includes the state-of-charge values and price estimations for the different vehicles charged with or without a bidirectional power flow to and from the electric grid. The results show that there is a greater difference in state-of-charge values over the day investigated for the electric vehicles with vehicle-to-grid capabilities than for vehicles without vehicle-to-grid capabilities. The results indicate potential economic revenues from using vehicle-to-grid if there is a significant variation in electricity prices during different hours. Therefore, the vehicle owner can potentially receive money from selling electricity to the grid while also supporting the electric grid. The study provides insights into utilizing vehicle-to-grid in society and taking steps towards its implementation.
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| 27. |
- Leijon, Jennifer, 1990-, et al.
(författare)
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Analysis of charging and discharging of electric vehicles
- 2023
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Konferensbidrag (refereegranskat)abstract
- With more electric vehicles introduced in society, there is a need for further implementation of charging infrastructure. Innovation in electromobility may result in new charging and discharging strategies, including novel concepts such as smart charging, vehicle-to-grid and vehicle-to-everything. Access to charging infrastructure and novel ideas on charging or discharging may contribute to driving the transition towards e-mobility. This article aims to provide an overview of vehicle charging and discharging innovations with a cable connection, including an example of a MATLAB/Simulink model of vehicle-to-grid dynamics.
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| 28. |
- Martins Mattos, Marina, et al.
(författare)
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Analysis of voltage control using V2G technology to support low voltage distribution networks
- 2024
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Ingår i: IET Generation, Transmission & Distribution. - : John Wiley & Sons. - 1751-8687 .- 1751-8695. ; 18:6, s. 1133-1157
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Tidskriftsartikel (refereegranskat)abstract
- The decarbonization of the power generation and transport sector encourage the analysis of connection of distributed energy resources (DER), such as electric vehicles (EVs), to the electrical system, as well as the evaluation of their impact on smart cities. A better understanding of the negative impacts on the power systems will lead to propose mitigation measures and eventually revolutionize the way distributed generation works. This paper aims at modelling and evaluating the impact of EVs on a real distribution network. The energy system chosen operates at 60 Hz, 34.5 kV (medium voltage) and 0.208 kV (low voltage) and it is simulated using PSCAD/EMTDC. To reproduce realistic user consumption profiles, dynamic load profiles based on EV owners behaviour have been simulated. The vehicle-to-grid (V2G) technology is modelled to mitigate the impacts of high penetration of EVs by supporting the network from undervoltage. The results show the importance of active management in modern power systems, especially considering the increase in DER penetration expected for the coming years. This work shows the benefits of implementing V2G technology while highlighting the challenges involved in a real case. This paper aims at modelling and evaluating the impact of EVs on a real distribution network. The V2G technology is modelled to mitigate the impacts of high penetration of EVs by supporting the network from undervoltage. This work shows the benefits of implementing V2G technology while highlighting the challenges involved in a real case.image
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| 29. |
- Mattos, Marina M., et al.
(författare)
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EV charging load forecast using LSTM : a case study at a multi-functional building in Uppsala, Sweden
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Energy-smart facilities contribute to a cleaner future by assisting the decarbonization of power generation and transportation. One example is the multi-functional building called Dansmästaren, which comprises a residential part, a commercial part and a parking garage and that is located in Uppsala, Sweden. This facility is a test bed for research on smart infrastructures for electric vehicle charging and has the flexibility to integrate different energy storage technologies, electricity generation units, database collection, and connectivity systems. Furthermore, Dansmästaren’s parking garage targets two distinct EV owner groups: public charger users and those with residential charging access. This work provides insights into charging behavior across these categories. This paper applies load forecast model using LSTM neural network to predict the parking garage’s load demand profile at Dansmästaren based on historical data. The performance of the LSTM network during testing and training is analyzed across various scenarios, using historical data from May 2021 to April 2023 collected at the parking garage. The hour-ahead load demand prediction achieves a mean absolute error (MAE) of 4.7. The results obtained in this study are valuable for implementing future smart charge strategies in real environment and for increasing knowledge about EV charging patterns.
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| 30. |
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| 31. |
- Olauson, Jon, et al.
(författare)
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Net load variability in Nordic countries with a highly or fully renewable power system
- 2016
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Ingår i: Nature Energy. - 2058-7546. ; 1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Increasing the share of intermittent renewable energy (IRE) resources such as solar, wind, wave and tidal energy in a power system poses a challenge in terms of increased net load variability. Fully renewable power systems have previously been analysed, but more systematic analyses are needed that explore the effect of different IRE mixes on system-wide variability across different timescales and the optimal combinations of IRE for reducing variability on a given timescale. Here we investigate these questions for the Nordic power system. We show that the optimal mix of IRE is dependent on the frequency band considered. Long-term (>4 months) and short-term (<2 days) fluctuations can be similar to today’s, even for a fully renewable system. However, fluctuations with periods in between will inevitably increase significantly. This study indicates that, from a variability point of view, a fossil- and nuclear-free Nordic power system is feasible if properly balanced by hydropower.
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| 32. |
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| 33. |
- Tibaldi, Martina, et al.
(författare)
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Exploring the Potential Demand-Side Flexibility of a Microgrid : A Case Study at a Multifunctional Building in Uppsala, Sweden
- 2024
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study investigates the potential implementation of a microgrid at Dansmästaren, a multifunctional building in Uppsala, Sweden, comprising a supermarket, residential apartments, and a parking garage. This paper analyzes the load profiles of the various components within Dansmästaren and the Uppsala grid to identify overlapping peak demand periods that increase overall facility power consumption and contribute to grid congestion. Focus is given to the three days with the highest peak loads; the worst day for Uppsala’s distribution grid, the highest peak for the entire building, and the highest peak for the parking garage, representing the most challenging scenarios for the microgrid. The study explores how integrating smart charging capabilities for electric vehicles in the parking garage can provide flexibility to shift loads and mitigate peak demands during these worst-case days. A flexibility index quantifies the extent to which the parking garage’s smart charging capabilities can support the building’s energy needs and reduce grid strain during peak demands. The study demonstrates a high potential for demand-side flexibility in Dansmästaren, as reflected by the Time Flexibility Index values of 0.77, 0.79, and 0.72. These results underscore the effectiveness of smart charging strategies in reducing peak loads and enhancing grid stability. The findings suggest that more advanced approaches could further improve building sustainability, especially in light of Sweden’s growing adoption of electric vehicles. This study encourages innovative urban solutions and provides a foundation for future research.
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| 34. |
- Wallberg, Alexander, 1991-, et al.
(författare)
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Negative correlation peak shaving control in a parking garage in Uppsala, Sweden
- 2024
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 375
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Tidskriftsartikel (refereegranskat)abstract
- As the global transition away from fossil fuels accelerates, energy systems across the globe face a significant challenge. Given the high energy consumption of electric vehicle chargers, effective control is imperative to prevent local grid overload and congestion. In Uppsala, Sweden, a newly built parking garage includes 30 electric vehicle chargers, 62 kW solar energy production, and a 60 kW/137 kWh battery energy storage system. This paper presents a control algorithm that uses a negative correlation scheme, adjusted to the local grid load, to effectively manage the battery energy storage. To improve the performance of the algorithm, a genetic optimization method is applied to find the best feasible daily load profile for the parking garage. The results indicate that peak load and energy consumption during grid high-load hours can be significantly reduced. This also results in an 9.5−12.8% reduction in electricity distribution fees at current prices as well as a peak load reduction of up to 50 %. Increasing the battery capacity and charging/discharging power in the scenarios analysed within the study will improve the algorithm’s ability to achieve a satisfactory negative correlation between the load demand of the facility and the local grid. The proposed control algorithm lowers the facility’s impact on the local grid during high-load peak hours by utilizing the battery energy storage system at the parking garage. Moreover, it decreases the distribution fees of the facility by lowering the load peaks and shifting the electricity consumption to the morning and night.
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| 35. |
- Wallberg, Alexander, 1991-, et al.
(författare)
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Peak Shaving for Electric Vehicle Charging Infrastructure : A Case Study in a Parking Garage in Uppsala, Sweden
- 2022
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Ingår i: World Electric Vehicle Journal. - : MDPI. - 2032-6653. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- The need for a more flexible usage of power is increasing due to the electrification of new sectors in society combined with larger amounts of integrated intermittent electricity production in the power system. Among other cities, Uppsala in Sweden is undergoing an accelerated transition of its vehicle fleet from fossil combustion engines to electrical vehicles. To meet the requirements of the transforming mobility infrastructure, Uppsala municipality has, in collaboration with Uppsala University, built a full-scale commercial electrical vehicle parking garage equipped with a battery storage and photovoltaic system. This paper presents the current hardware topology of the parking garage, a neural network for day-ahead predictions of the parking garage’s load profile, and a simulation model in MATLAB using rule-based peak shaving control. The created neural network was trained on data from 2021 and its performance was evaluated using data from 2022. The performance of the rule-based peak shaving control was evaluated using the predicted load demand and photovoltaic data collected for the parking garage. The aim of this paper is to test a prediction model and peak shaving strategy that could be implemented in practice on-site at the parking garage. The created neural network has a linear regression index of 0.61, which proved to yield a satisfying result when used in the rule-based peak shaving control with the parking garage’s 60 kW/137 kWh battery system. The peak shaving model was able to reduce the highest load demand peak of 117 kW by 38.6% using the forecast of a neural network.
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| 36. |
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