Control and monitoring networks often operate on AC/DC power systems. DC batteries and chargers are commonly used on industrial plants as auxiliary DC power systems for these control and monitoring networks. The energy demand and load profiles for these control networks differ from application to application. Proper design, sizing, and maintenance of the components that forms part of the DC control power system are therefore required. Throughout the load profile of a control and monitoring system there are various peak currents. The peak currents are classified as inrush and momentary loads. These inrush and momentary loads play a large role when calculating the required battery size for an application. This study investigates the feasibility of using supercapacitors in conjunction with batteries, in order to reduce the size of the required battery capacity. A reduction in the size of the required battery capacity not only influences the cost of the battery itself, but also influences the hydrogen emissions, the physical space requirements, and the required rectifiers and chargers. When calculating the required size batteries for an auxiliary power system, a defined load profile is required. Control and monitoring systems are used to control dynamic processes, which entails a continuous starting and stopping of equipment as the process demands. This starting and stopping of devices will cause fluctuations in the load profile. Ideally, data should be obtained from a live plant for the purpose of defining load profiles. Unfortunately, due to the economic risks involved, installing data logging equipment on a live industrial plant for the purpose of research, is not allowed. There are also no historical data available from which load profiles could be generated. In order to evaluate the influence of supercapacitors, complex load profiles are required. In this study, an alternative method of defining the load profile for a dynamic process is investigated. Load profiles for various applications are approximated using a probabilistic approach. The approximation methodology make use of plant operating philosophies as input to the Markov Chain Monte Carlo simulation theory. The required battery sizes for the approximated profiles are calculated using the IEEE recommended practice for sizing batteries. The approximated load profile, as well the calculated battery size are used for simulating the auxiliary power system. A supercapacitor is introduced into the circuit and the simulations are repeated. The introduction of the supercapacitor relieves the battery of the inrush and momentary loads of the load profile. The battery sizing calculations are repeated so as to test the influence of the supercapacitor on the required battery capacity. In order to investigate the full influence of adding a supercapacitor to the design, the impact on various factors are considered. In this study, these factors include the battery size, charger size, H2 extraction system, as well as maintenance requirements and the life of the battery. No major cost savings where evident from the results obtained. Primary reasons for this low cost saving are the fixed ranges in which battery sizes are available, as well as conservative battery data obtained from battery suppliers. It is believed that applications other than control and monitoring systems will show larger savings. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

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Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Auxiliary power units, which operate independently of the main engine, are promising alternatives for supplying trucks with electricity. Fuel cell-based auxiliary power units could offer high efficiencies and low noise. The hydrogen required for the fuel cell could be generated in an onboard fuel reformer using the existing truck fuel. The work presented in this thesis concerns hydrogen generation from transportation fuels by autothermal reforming focusing on the application of fuel cell auxiliary power units. Diesel and dimethyl ether have been the fuels of main focus. The work includes reactor design aspects, preparation and testing of reforming catalysts including characterization studies and evaluation of operating conditions. The thesis is a summary of five scientific papers. Major issues for succeeding with diesel reforming are fuel injection, reactant mixing and achieving fuel cell quality reformate. The results obtained in this work contribute to the continued research and development of diesel reforming catalysts and processes. A diesel reformer, designed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell has been evaluated for autothermal reforming of commercial diesel fuel. The operational results show the feasibility of the design to generate hydrogen-rich gases from complex diesel fuel mixtures and have, together with CFD calculations, been supportive in the development of a new improved reformer design. In addition to diesel, the reforming reactor design was shown to run satisfactorily with other hydrocarbon mixtures, such as gasoline and E85. Rh-based catalysts were used in the studies and exhibit high performance during diesel reforming without coke formation on the catalyst surface. An interesting finding is that the addition of Mn to Rh catalysts appears to improve activity during diesel reforming. Therefore, Mn could be considered to be used to decrease the noble metal loading, and thereby the cost, of diesel reforming catalysts. Dimethyl ether is a potential diesel fuel alternative and has lately been considered as hydrogen carrier for fuel cells in truck auxiliary power units. The studies related to dimethyl ether have been focused on the evaluation of Pd-based catalysts and the influence of operating parameters for autothermal reforming. PdZn-based catalysts were found to be very promising for DME reforming, generating product gases with high selectivity to hydrogen and carbon dioxide. The high product selectivity is correlated to PdZn interactions, leading to decreased activity of decomposition reactions. Auxiliary power systems fueled with DME could, therefore, make possible fuel processors with very low complexity compared to diesel-fueled systems. The work presented in this thesis has enhanced our understanding of diesel and DME reforming and will serve as basis for future studies. / QC 20100804

<p>Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute.</p><p>The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations.</p><p>In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kW_e polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I.</p><p>In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature.</p>

Transformatorstationer i det svenska elnätet innehar en vital funktion för att försörjningen av elenergi från producent till konsument skall fungera. Stationerna finns på olika spännings-nivåer – men de har alla en sak gemensamt: Behov av att lokalkraftsförsörjningen skall fungera enligt angivna krav. Försörjningen av en stations lokalkraftanläggning kan ske på flera olika sätt. I rapporten belyses alternativen stationstransformator, externt abonnemang, ok-lindning och ABB:s SSVT (Station Service Voltage Transformer). De olika lösningarna karaktäriseras av olika tekniska och ekonomiska aspekter och tillhörande för- respektive nackdelar. Studien utvärderar de fyra olika lokalkraftslösningarna ur ett helhetsperspektiv. Först redogörs för den bakomliggande grundläggande teorin kring lokalkraft och elkraftsekonomi. Därefter jämförs de tekniska och ekonomiska skiljaktigheterna gentemot varandra för respektive given transformatorstationstyp; fördelnings-, region- och stamstation. Vattenfall eftersöker de teknisk-ekonomiskt bästa lokalkraftsalternativen för deras transformatorstationer och rapporten skall fungera som underlag. Ur rapporten kan följande resultat och slutsatser erhållas: • Fördelningsstation: Stationstransformator och ok-lindning rekommenderas då de erbjuder teknisk funktionalitet till ett ekonomiskt försvarbart och likvärdigt pris. • Regionstation: Primärt rekommenderas alternativet ok-lindning. • Stamstation: Likväl som på de andra stationerna rekommenderas ok-lindning för försörjning av lokalkraft. Sammanfattningsvis erbjuder alla fyra alternativ de tekniska krav som finns för lokalkraftsförsörjning, men att en avvägning av vilken lösning som lämpar sig bäst för respektive transformatorstation bör utföras från fall till fall. / Substations in the Swedish electric power network have a vital function regarding the supply of electric energy from producer to consumer. The substations are represented on different voltage levels in the network – but they all have one thing in common: The need for auxiliary power to function as intended. There are different options for the supply of substations auxiliary feed. In the thesis the following alternatives are described holistic: local transformer, external power subscription, auxiliary winding on ordinary transformer, and a new (for the Swedish market) alternative from ABB called SSVT (Station Service Voltage Transformer). The distinct solutions are characterized with different technical and economic aspects and associated pros and cons. The study evaluates the four different auxiliary power solutions from a holistic view. First, the underlying essential theory about auxiliary power and electrical power economy is explained. Afterwards, the technical and economical differences are visualized for each of the solutions, and in comparison to each other for each defined substation type; distribution, region and national substation. The company Vattenfall strives for the best technical-economical alternatives for their different types of substations and the report intends to act as a supportive document. From the report, the following results and conclusions can be obtained: • Distribution substation: Local transformer and auxiliary winding is recommended due the technical functionality relative to its equivalent economic aspects. • Region substation: Primarily, the auxiliary winding alternative is recommended, mostly because of the cost-effectiveness. There are fewer alternatives in this type of substation. • National substation: The auxiliary winding is recommended as local power solution. To sum up, all of the four alternatives fill the technical requirements, but consideration for which solution for which substation type must be done on a case to case basis.

Although current trends in global warming are of great concern, energy demand is still increasing, resulting in increasing pollutant emissions. To address this issue, we need reliable renewable energy sources, lowered pollutant emissions, and efficient and profitable processes for energy conversion. We also need to improve the use of the energy, produced by existing infrastructure. Consequently, the work presented in this thesis aims at investigating current scientific and technological challenges in energy conversion through biomass gasification and the alternative use of fossil fuels, such as diesel, in the generation of cleaner electricity through auxiliary power units in the transport sector. Production of chemicals, syngas, and renewable fuels is highly dependent on the development and innovation of catalytic processes within these applications. This thesis focuses on the development and optimization of catalytic technologies in these areas. One of the limitations in the commercialization of the biomass gasification technology is the effective catalytic conversion of tars, formed during gasification. Biomass contains high amounts of alkali impurities, which pass on to the producer gas. Therefore, a new material with alkali tolerance is needed. In the scope of this thesis, a new catalyst support, KxWO3 – ZrO2 with high alkali resistance was developed. The dynamic capability of KxWO3 – ZrO2 to store alkali metals in the crystal structure, enhances the capture of alkali metals "in situ". Alkali metals are also important electronic promoters for the active phase, which usually increases the catalysts activity and selectivity for certain products. Experimental results show that conversion of 1-methylnaphathalene over Ni/KxWO3 – ZrO2 increases in the presence of 2 ppm of gas-phase K (Paper I). This support is considered to contribute to the electronic equilibrium within the metal/support interface, when certain amounts of alkali metals are present. The potential use of this support can be extended to applications in which alkali "storage-release" properties are required, i.e. processes with high alkali content in the process flow, to enhance catalyst lifetime and regeneration. In addition, fundamental studies to understand the adsorption geometry of naphthalene with increasing temperature were performed in a single crystal of Ni(111) by STM analyses. Chapter 9 presents preliminary studies on the adsorption geometry of the molecule, as well as DFT calculations of the adsorption energy. In relation to the use of clean energy for transport applications, hydrogen generation through ATR for FC-APUs is presented in Papers II to V. Two promoted RhPt bimetallic catalysts were selected in a previous bench scale study, supported on La2O3:CeO2/d – Al2O3 and MgO : Y2O3/CeO2 – ZrO2. Catalyst evaluation was performed in a fullscale reformer under real operating conditions. Results showed increased catalyst activity after the second monolithic catalyst due to the effect of steam reforming, WGS reaction, and higher catalyst reducibility of the RhxOy species in the CeO2 – ZrO2 mixed oxide, as a result of the improved redox properties. The influence of sulfur and coke formation on diesel reforming was assessed after 40 h on stream. Sulfur poisoning was evaluated for the intrinsic activity related to the total Rh and Pt area observed after exposure to sulfur. Sulfur concentration in the aged catalyst washcoat was observed to decrease in the axial direction of the reformer. Estimations of the amount of sulfur adsorbed were found to be below the theoretical equilibrated coverage on Rh and Pt, thus showing a partial deactivation due to sulfur poisoning. / <p>QC 20150213</p>

The current Auxiliary Power Unit (APU) contributes a lot to the greenhouse effect in terms of emissions, and in the form of noise and also is very heavy. The need for more electricity has increased in aircrafts and therefore major aircraft suppliers like Boeing and Airbus want to switch to more electric aircraft (MEA) which is lighter and has less environmental impacts. The purpose of this work is to investigate the possibilities of replacing today's traditional APU with fuel cells. In this work presents six different common fuel cell types which used commercially in various areas in the market. We have also analyzed and investigated the most suitable fuel cell types and have chosen to apply the SOFC-GT Hybrid Systems. We have investigated and compared both systems with pros and cons. We have used different methods in this work including the FOI3-method and Safran &amp; Honeywell for calculations of emissions for all systems. Finally, we have analyzed and investigated the emissions, noise and weight for both systems. / Nuvarande Auxiliary Power Unit (APU) bidrar mycket negativt till växthuseffekten i form av emissionsutsläpp och även i form av buller och är dessutom mycket tunga. Behovet av mer elektricitet ökar i flygplan och därför vill stora flygplanstillverkare såsom Boeing och Airbus övergå till more electric aircraft (MEA) vilket är lättare och har mindre miljöpåverkan. Syftet med detta arbete är att undersöka möjligheterna av att ersätta dagens traditionella APU mot bränsleceller. I detta arbete presenteras sex olika bränslecellstyper som finns på marknaden och används kommersiellt inom olika områden. Vi har analyserat och undersökt de lämpligaste bränslecellstyper för applicering och därefter har vi valt att implementera SOFC- GT Hybridsystemen. Vi har undersökt och jämfört båda systemens för- och nackdelar. Metodmässigt används bland annat FOI3-Metoden och Safran &amp; Honeywell för beräkningar av utsläpp av emissioner för samtliga system. Slutligen har vi analyserat och undersökt skillnader i utsläpp av emissioner, buller och vikt för båda systemen.

I denna rapport utreds problem med spänningsfall i hjälpkraften på olika sträckor i Sverige. Hjälpkraften förser el, tele och signalsystemen med ström. Spänningsnivån kan vara 22 kV trefas eller 11 kV tre eller tvåfassystem. Rapportens utgångspunkt är STRI’s utredning om hjälpkraft där en schablonmetod har framställts. Den metoden har jämförts med simuleringsresultat ur µPAS. De sträckor som rapporten omfattar är trefas med den nominella spänningen 11 kV, 50 Hz. Sträckorna har modellerats och simulerats i µPAS. Vidare har enkla analytiska metoder används, där hela lasten antogs ligga  i slutet på linjen. Resultaten från den analytiska modellen har sedan jämförts med de simulerade. Utifrån detta har två alternativa lösningar tagits fram: att höja den nominala spänningen till 22 kV eller ändra placeringen på inmatningspunkterna vid långmatning. För ett indikativt resultat kunde schablonmetoden användas, för en mer precis undersökning var  µPAS ett bättre alternativ. Slutsatsen är att alla undersökta och normalmatade sträckor för 11 kV klarar spänningskraven på ± 10 % av nominalspänning. Problem uppkommer vid långmatning och då 11 kV inte upprätthålls från omformarstation. / This report will investigate troubles with voltage drop in the auxiliary power system on different routes in the Swedish railway. The auxiliary power system provides the electrical, telecom and signalling systems with power. The voltage level can be 22 kV three phase or 11 kV three or two phase. The report is based on an investigation from STRI where a standardised approach has been developed. The routes included in the report are three phase and has the rated voltage of 11 kV, 50 Hz. The routes have been modulated and simulated in µPAS. To verify the results from the simulations calculations have been made separately. From the results two alternative solutions has been presented. Raise the voltage to 22 kV or change the position of the feeder for long feed. The aim was to lower the voltage drop for each of the solutions. For a quick control the standardised approach can be used. To get more accurate values µPAS is the better alternative.   One conclusion was that all examined routes with 11 kV and are normal fed fulfil the demands of ± 10 % of rated voltage. Issues appear when a route is long fed and if the voltage from a frequency converter drops below 11 kV.

It is anticipated that massive amounts of energy will be transferred long distances via High-Voltage Direct Current (HVDC) links in the future and the prospect of having meshed HVDC grids is envisioned, for example the European super grid. Such a power system would benefit greatly if HVDC circuit breakers could reliably clear faults within the HVDC network. Different ways to break large direct currents have been proposed throughout the years and one distinguished concept is based on generating an artificial zero-crossing of the current and pass it through a mechanical interrupter as it opens. This concept is implemented in the Voltage-Source Converter Assisted Resonant Current (VARC) circuit breakers developed at Scibreak which require auxiliary power from an off-line supply unit to energize their electronic equipment. This thesis continuous and builds on research previously carried out at Scibreak on a special Auxiliary Power Supply (APS) concept for 525 kV HVDC applications. In essence, it is a unique modularized high-frequency transformer whose power transfer and voltage withstand capabilities are the cornerstones of its design. The APS must supply an adequate amount of power to drive the VARC circuit breakers with preferably high efficiency while also fulfilling the considerable insulation demands of HVDC grids. A feasibility study of this APS concept was carried out by building a parametric 3D model in the Finite Element Analysis (FEA) software Ansys Maxwell which includes all parts that affect both its magnetic and electrical properties. The initial model reproduced experimental results from a magnetic APS prototype and was then used to explore a plethora of different geometries and materials with regards to its magnetic and dielectric designs. Specific design candidates were selected for more in-depth analysis and experimental work. All obtained results together with knowledge of commercially available materials show that the APS holds great promise to meet the necessary design criteria for its HVDC applications. Its dielectric design is well suited to continuously handle an operating voltage of 525 kV DC, meet the required impulse voltage levels of the grid and properly shield the magnetic structure. It is expected to have a long life time where the design criterion was always 30 years in this work. Moreover, its magnetic design is anticipated to supply a few kW of active power with efficiencies between 80 to 95 percent and manage a continuous operating time of 5 min. Both design aspects are interchangeable to a decent extent in order to cope with one another and produce a compromised design. / Det förväntas att enorma mängder energi kommer överföras långa sträckor med Högspänd Likström (HVDC) i framtiden och blivande HVDC-nät håller på att föreställas, till exempel det europeiska superelnätet. Ett sådant kraftsystem skulle ha stor nytta av HVDC-brytare som tillförlitligt kan bryta felströmmar inom HVDC-nätet. Olika sätt att bryta stora likströmmar har föreslagits med åren och ett distinkt koncept bygger på att generera en artificiell nollgenomgång av strömmen och föra den genom en mekanisk brytarkammare när den öppnas. Detta koncept är implementerat i de så kallade VARC-strömbrytarna som utvecklas hos Scibreak, vilka kräver hjälpmatning av effekt från en extern försörjningsenhet för att driva deras elektroniska utrustning. Denna avhandling fortsätter och bygger vidare på forskning som tidigare utförts hos Scibreak på ett speciellt Hjälpmatningskoncept (APS) för 525 kV HVDC-tillämpningar. I huvudsak är det en unik modulariserad högfrekvenstransformator vars kraftöverföring och spänningståligheter är huvudfokusen i dess design. Hjälpmatningen måste kunna leverera en tillräcklig mängd effekt för att driva VARC-brytarna med företrädesvis hög verkningsgrad, samtidigt som den ska uppfylla de betydande isolationskraven för HVDC-nät. En genomförbarhetsstudie av detta APS-koncept gjordes genom att bygga en parametrisk 3D modell i Finita Elementmetodsprogramvaran (FEM) Ansys Maxwell som inkluderar alla delar som påverkar både dess magnetiska och elektriska egenskaper. Den initiala modellen reproducerade experimentella resultat från en magnetisk APS-prototyp och användes sedan för att utforska en uppsjö av olika geometrier och material med avseende på dess magnetiska och dielektriska konstruktioner. Specifika designkandidater valdes ut för mer djupgående analys och experimentiellt arbete. Alla erhållna resultat tillsammans med kunskap om kommersiellt tillgängliga material visar att APS:n har stora möjligheter att uppfylla alla nödvändiga kriterier för sina HVDC-tillämpningar. Dess dielektriska design är väl lämpad för att kontinuerligt hantera en driftspänning på 525 kV DC, möta de erforderliga stötspänningståligheterna i nätet och ordentligt skydda den magnetiska strukturen. Den förväntas ha en lång livstid där designkriteriet alltid var 30 år i detta arbete. Dessutom förväntas dess magnetiska design leverera några kW aktiv effekt med verkningsgrader mellan 80 till 95 procent och klara en kontinuerlig drifttid på 5 min. Båda designaspekterna kan justeras i en någorlunda utsträckning för möta de krav som ställs från varandra och producera en kompromissad design.

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute. The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations. In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I. In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature. / QC 20101115