Abstract

This thesis is about Photovoltaic (PV) cells and its stresses in various directions by calculating the power generated using solar cells under different conditions to improve its efficiency. Our research studies found that using multi-junction cells with larger substrates can increase the efficiency to some extent which in practice is limited to 43 percent. The experiment was conducted using ten solar cells each with an area of 20.9?cm? ^2, where each cell gives 0.5 V and 0.4 A and a 1.25 ? resistor was used. The cells were connected in series. Once, the PV cells were fixed horizontally and the other time tested in tilted position under same outdoor condition. The purpose of testing PV cells was to investigate the efficiency under above mentioned conditions. The data collected from the readings was used in calculation, and we have obtained from the calculations that horizontally fixed cells gave 4.8 percent efficiency whereas tilted cells gave 6.6 percent efficiency. Hence, the ratio showed that fixed cells produced 37.5 percent more power compared to horizontally fixed cells. Our other experiment consisted of testing PV cells under different temperature conditions that was done using a freezer and an oven for temperature variation and a tungsten bulb was used as a light source. The purpose of performing this experiment was to investigate how the efficiency of PV cells is affected under extreme conditions. Part of our thesis was also including studies and analysis of produced energy by the solar panel installed on the roof of “BTH” building in Karlskrona, Sweden. The data consisted of energy produced from February up to August 2014. The investigation also included finding the highest produced energy during these months. We have found that the highest energy was generated on the 1st of July which was 12.86 kWh. Furthermore, we went deep into investigation of the 1st of July to know exactly which hour of that day the highest energy was produced. The data showed that the highest produced energy was at 12:19 and 13:19 which was 2.03 kWh. Ramzi: +46723231353, +966561993488 Zain Document type: Part of book or chapter of book

Abstract

Flexible and economic systems for electric operation of road vehicles is an area of interest for researchand development. This report applies such systems to the operation of city buses in Linköping. An LTHdeveloped software for simulations and economic optimizations of such systems is used and a few systemdesigns are presented. The tested systems differ in selection of bus lines and the type of chargingsystem: bus stop charger, high power bus stop charger and electric road. An attempt to a realistic costand performance estimate of the main components is presented. All buses are assumed to operatewith the same time table as today. Under some of the assumptions these systems are shown to becost competitive to diesel and gas buses in addition to being quieter and without local pollution. Thisresult is however uncertain due to the difficulty in predicting the cost of new technologies and due toother sources of error such as error in assumed energy consumption.

Abstract

The energy system is being transitioned to increase sustainability. This transition has been accelerated by the increased awareness about the adverse effects of the greenhouse gas (GHG) emissions into the atmosphere. The transition includes switching to electricity as the energy carrier in some sectors, e.g., transportation, increasing the contribution of renewable energy sources (RES) to the grid, and digitalizing the grid services. Electric vehicles (EVs) are promoted and subsidized in many countries among the sustainability initiatives. Consequently, the global sales of EVs rapidly increased in the recent years. Many EV owners might charge their EVs only at home, thereby increasing the residential load. The residential load might further increase due to the initiatives to electrify the heating/cooling sector. This thesis contributes to the knowledge about the operation of the future energy system by modeling the spatial charging load of private EVs in cities, and by proposing a forecasting model to predict the residential load. Both models can be used to evaluate the impacts of both technologies on the local electricity grid. In addition, demand response (DR) schemes can be proposed to reduce the adverse effects of both the charging load of EVs and the residential load. A case study of the EV model on the Herrljunga city grid showed that 100% EV penetration with 3.7 kW (charging rate of 14.8 km/h) chargers will not cause voltage violations in the grid. Winter load is responsible for 5% voltage drop at the weakest bus, and EVs add only 1% to this drop. In a Swedish city, charging EVs will require adding extra 1.43 kW/car to the grid capacity—assuming 22 kW (charging rate of 88 km/h) residential chargers. If the EV charging is not restricted to residential locations, an increase of 1.23 kW/car is expected. The proposed forecasting model is comparable in accuracy to previously developed models. As an advantage, the model produces a probability density function (PDF) describing the model’s certainty in the forecast. In contrast, many previous contributions provided only point forecasts.

Abstract

This thesis deals with the interaction of batteries and power electronic converters in automotive applications. Even if the additional heating caused by (unwanted) alternating currents is disregarded, there has been a concern that alternating currents can be harmful for batteries. For that reason, alternating currents can be filtered using capacitors and/or by sophisticated hardware. In this work, the concern whether alternating currents are harmful to batteries is studied particular focus on large, lithium-ion cells for use in automotive applications.First, the harmonic content in the battery current of two, commercial hybrid-electric busses were measured and analysed. The most prominent harmonic had a peak magnitude higher than 10% of the maximum direct current level (160 A) arising at frequencies below 150 Hz. The maximum amplitude detected of a harmonic caused by the voltage source converter’s switching action was around 10 A and occurred at a frequency of 2 kHz. An experimental setup with alternating current capability for evaluating large lithium-ion cells has been designed and built. Twelve lithium-ion cells were cycled at a rate if 1 C during approximately 2000 cycles (corresponding to approximately one year). The cells were cycled with an superimposed alternating current of 1 Hz, 100 Hz, or 1 kHz while the rest of the cells were cycled with direct current (only), injected with alternating current (only), or no current at all (calendar aging). No negative effects caused by the alternating current was identified in terms of capacity fade and power fade for the tested lithium-ion cells. A comparison between sinusoidal current-ripple charging and conventional constant-current constant-voltage charging was also carried out. Three lithium-ion cells were cycled (ten times) with different ac currents superimposed during charge. The results were analyzed statistically and no significant improvements in terms of charging time or charging efficiency were observed in any of the charging tests using an superimposed ac current. The injection of alternating currents into batteries for heating purposes has also been studied and a control method for battery heating using an ac current was proposed. The proposed controller is applicable regardless of the LIB’s subsequent impedance nature (capacitive, inductive or resistive). Further, a design process for the generation of magnified alternating currents in dc-dc converters was presented. By matching the switching frequency with the frequency where the LCL filter and the battery resonate, the current flowing in the semiconductors and the switching frequency could be reduced. In a small experimental setup using a single lithium-ion cell, using an LCL-resonant circuit and a full bridges witch arrangement, magnifications of up to 15.7 were reached. This allowed for a loss reduction in the semiconductors of up to 75%, when compared to an equivalent dc-dc converter enabled to produce anon-magnified ac current.  "p"QC 20190517

Abstract

utomation in the mining industry has the potential to increase safety and productivity while improving working conditions. Ore transportation within the mine is a repetitive task which is well suited to be replaced by an autonomous mining vehicle operating around the clock. Scania, a world leader in sustainable transport solutions is investigating this new concept of vehicle. The autonomous operation is enabled by several technologies installed on the vehicle, including a communication system object of this thesis. Connectivity among vehicles is required in order to coordinate paths and exchange mission critical information. In this thesis, after identifying the challenges of wireless propagations in mines, the communication technology is chosen and possible antenna configurations and communication ranges are found. Through numerical link-budget simulations and subsequent range measurements, the potential communication range of this vehicle has been quantified. The results show the effectiveness of height diversity in extending the communication range. Lastly, the performance degradation caused by dust accumulated on the antennas is discussed. Automatiseringen i gruvindustrin har potentialen att öka säkerheten och produktiviteten samtidigt som den förbättrar arbetsvillkoren. Malmtransporten inne i gruvan är en repetitiv uppgift som passar bra att bli utbytt av en autonom gruvtransport som är i drift dygnet runt. Scania, en av de världsledande inom hållbara tranportlösningar, undersöker just nu denna typ av fordon. Den självstyrande driften aktiveras genom att ett flertal teknologier installeras på fordonet, inklusive ett kommunikationssystem som är ämne för denna avhandling. Anslutningen mellan fordonen är nödvändig för att kunna samordna banor och ge information i för uppdraget kritiska lägen. I denna avhandling, efter att ha identifierat svårigheterna med en trådlös utbredning i gruvor, är kommunikationsteknologin vald och möjliga antennkonfigurationer och kommunikationsräckvidder funna. Genom numeriska länkbudgetsimuleringar och efterföljande räckviddsmätningar, har det potentiella kommunikationsområdet för detta fordon kvantifierats. Resultaten visar effektiviteten av mångfald när det gäller höjd när man utvidgar kommunikationsområdet. Slutligen diskuteras prestandaförsämringen orsakad av damm som ackumulerats på antennerna.

Abstract

Network technologies are continuously advancing and attracting ever-growing interests from the industry and society. Network users expect better experience and performance every day. Consequently, network operators need to improve the quality of their services. One way to achieve this goal entails over-provisioning the network resources, which is not economically efficient as it imposes unnecessary costs. Another way is to employ Traffic Engineering (TE) solutions to optimally utilize the current underlying resources by managing traffic distribution in the network. In this thesis, we consider packet-switched Networks (PSN), which allows messages to be split across multiple packets as in today’s Internet. Traffic engineering in PSN is a well-known topic yet current solutions fail to make efficient utilization of the network resources. The goal of the TE process is to compute a traffic distribution in the network that optimizes a given objective function while satisfying the network capacity constraints (e.g., do not overflow the link capacity with an excessive amount of traffic). A critical aspect of TE tools is the ability to capture the impact of routing a certain amount of traffic through a certain link, also referred as the link criticality function. Today’s TE tools rely on simplistic link criticality functions that are inaccurate in capturing the network-wide performance of the computed traffic distribution. A good link criticality function allows the TE tools to distribute the traffic in a way that it achieves close-to-optimal network performance, e.g., in terms of packet loss and possibly packet latencies. In this thesis, we embark upon the study of link criticality functions and introduce four different criticality functions called: 1) LeakyCap, 2) LeakyReLU, 3) SoftCap, and 4) Softplus. We compare and evaluate these four functions with the traditional link criticality function defined by Fortz and Thorup, which aims at capturing the performance degradation of a link given its utilization. To assess the proposed link criticality functions, we designed 57 network scenarios and showed how the link criticality functions affect network performance in terms of packet loss. We used different topologies and considered both constant and bursty types of traffic. Based on our results, the most reliable and effective link criticality function for determining traffic distribution rates is Softplus. Softplus outperformed Fortz function in 79% of experiments and was comparable in the remaining 21% of the cases. Nätverksteknik är ett område under snabb utveckling som röner ett stort och växande intresse från såväl industri som samhälle. Användare av nätverkskommunikation förväntar sig ständigt ökande prestanda och därför behöver nätverksoperatörerna förbättra sina tjänster i motsvarande grad. Ett sätt att möta användarnas ökade krav är att överdimensionera nätverksresurserna, vilket dock leder till onödigt höga kostnader. Ett annat sätt är att använda sig av trafikstyrninglösningar med målet att utnyttjade tillgängliga resurserna så bra som möjligt. I denna avhandling undersöker vi paketswitchade nätverk (PSN) i vilka meddelanden kan delas upp i multipla paket, vilket är den rådande paradigmen för dagens Internet. Ä ven om trafikstyrning (TS) för PSN är ett välkänt ämne så finns det utrymme för förbättringar relativt de lösningar som är kända idag. Målet för TS-processen är att beräkna en trafikfördelning i nätverket som optimerar en given målfunktion, samtidigt som nätverkets kapacitetsbegränsningar inte överskrids. En kritisk aspekt hos TS-verktygen är förmågan att fånga påverkan av att sända en viss mängd trafik genom en specifik länk, vilket vi kallar länkkritikalitetsfunktionen. Dagens TS verktyg använder sig av förenklade länkkritikalitetsfunktioner som inte väl nog beskriver trafikfördelningens påverkan på hela nätverkets prestanda. En bra länkkritikalitetsfunktion möjliggör för TS-verktygen att fördela trafiken på ett sätt som närmar sig optimal nätverksprestanda, till exempel beskrivet som låg paketförlust och låg paketlatens. I denna avhandling undersöker vi länkkritikalitetsfunktioner och föreslår fyra olika funktioner som vi kallar 1) LeakyCap, 2) LeakyReLU, 3) SoftCap, och 4) Softplus. Vi jämför och utvärderar dessa fyra funktioner och inkluderar även klassiska länkkritikalitetsfunktioner som Fortz och Thorup, vilka avser fånga prestandadegraderingen av en länk över graden av utnyttjande.Vi har undersökt 57 olika nätverksscenarier för att bestämma hur de olika länk kritikalitets funktionerna påverkar nätverksprestanda i form av paketförlust. Olika topologier har använts och vi har studerat såväl konstant som stötvis flödande trafik. Enligt våra resultat är Softplus den mest tillförlitliga och effektiva länkkritikalitetsfunktionen för att fördela trafiken i ett nätverk. Softplus presterade bättre än Fortz i 79% av våra tester, och var jämförbar i övriga 21%.

Abstract

Over the past decades, congestion and emission problems has increased remarkablywhich escalates the demands on vehicles. The advancements withinthe eld of information and communication systems gives the opportunity todeal with the aforementioned problems. The concept of platooning shows tobe an attractive way of reducing both congestion and emissions by having ashort inter-vehicle spacing. The ndings in studies show that fuel reductionpotentials of 5-20 % are viable as a result of the lowered air drag by drivingin platoon. This thesis investigates the state of the art within the areaof intelligent transport systems (ITS) along with advanced driver assistancesystems (ADAS). Furthermore, the prosecuted work results in a proposedcontrol design for a longitudinal control in a platoon of vehicles. The platoonconsists of two homogeneous radio controlled vehicles (RCV) which aremodelled by taking advantage of system identication methods. The identi-ed plant models are implemented into a Simulink model where the controlsystem is developed. Moreover, the developed control system is implementedinto a real-time demonstrator for experimental evaluation. The results showsthat the modelled dynamics corresponds reasonably well with the real dynamicsof the system. The developed control system proves to work well andagree with the expectations of its performance obtained from simulations.The performance of the proposed controller has been evaluated by means ofsimulations and real experiments. The resulting control system consists ofPID controllers for both speed and spacing control. Under de senaste decennierna har mangden trakstockningar och problemmed utslapp okat - darmed aven kraven pa vara fordon. Samtidigt skaparframstegen inom informations- och kommunikationssystem mojligheter foratt hantera ovannamnda problem. Kolonnkorning, eller platooning har visatsig vara en eektiv metod for att minska saval trakstockningar som utslappsom en foljd av kortare avstand mellan fordon. Resultat fran studier visarhur en branslereduktion runt 5-20 % ar mojlig till foljd av det sankta luftmotstandet vid kolonnkorning. Avhandlingen undersoker teknikens standpunktinom intelligenta transportsystem (ITS) tillsammans med avancerade drivhjalpsystem(ADAS). Vidare resulterar arbetet i ett forslag till regleringsdesignfor en longitudinell kontroll i en kolonn av fordon. Kolonnen bestar av tvahomogena radiostyrda fordon (RCV) som modelleras genom att utnyttjametoder for systemidentiering. De identierade systemmodellerna implementerasi en Simulink-modell dar styrsystemet utvecklas. Dessutom implementerasdet utvecklade styrsystemet i en realtids-demonstration for experimentellutvardering. Resultaten visar att den modellerade dynamikenstammer bra overens med systemets verkliga dynamik. Det utvecklade styrsystemetvisar sig fungera bra och overensstammer med forvantningarna pa dessprestanda som erhallits genom simuleringar. Den foreslagna regulatorns prestandahar utvarderats med hjalp av simuleringar och verkliga experiment.Det resulterande styrsystemet bestar av PID regulatorer for bade hastighetsochavstandskontroll.

Abstract

Electric vehicles (EV) can be considered as energy storage with availability, energy and capacity constraints that can provide flexibility to the power system in the form of balancing products when aggregated. In this paper, we develop a two-stage stochastic optimization problem that maximizes the profit of a risk-averse EV aggregator for bids on the day ahead in both energy and Frequency Containment Reserve (FCR) markets. Unidirectional charging is examined, while we take into account uncertainty from prices and vehicle availability. Case studies are carried out in different Nordic bidding areas based on historical EV charging data. We identify a strong temporal alignment of EV availability and high FCR-N prices. Results show that consumption is shifted largely towards early hours of the morning. When compared to a reference cost of charging case, up to 50% of the cost of charging can be recovered in Norway, and 100% in Sweden. "p"QC 20190710. QC 20191203

Abstract

In this paper we present an overview of a vehicle-to-vehicle radio channel measurement campaign at 5.6GHz. The selected measurement scenarios are based on important safety-related applications. We explain why these scenarios are interesting from the aspect of radio propagation. Further we"br /" describe the power-delay profile and the Doppler spectral density of two situations especially suitable for collision avoidance applications: A traffic congestion situation where one car is overtaking another one, and a general line-of-sight obstruction between the transmitter and the receiver car. The evaluations show that in these situations the radio channel is highly influenced by the rich scattering environment. Most important scatterers are traffic signs, trucks, and bridges, whereas other cars do not significantly contribute to the multipath propagation.