This dissertation deals with impedance measurements of lead-acid accumulator. Main aim was to study recent problems of impedance measurements of lead-acid accumulator and most importantly to extend difference method and also to interpret its results. The original DC difference method was developed earlier at our Power Sources Laboratory of Department of Electrical and Electronic Technology. The DC difference method and also the new AC difference method are both non-destructive, which means that experimental data can be obtained in situ. New method provides more accurate set of information because of its wide frequency range nature. Electrodes of lead-acid accumulator were analysed with special attention to collector / active mass double layer and to active mass itself. Various states and operation regimes were investigated. Obtained data contributed to better understanding of involved degradation mechanisms. Main aim of other experiment was to observe and interpret corrosion rates of electrode collector composed of various lead alloys. Last but not least charge and discharge regimes e.g. 100% deep of discharge regime, partial state of charge (PSoC) regime and pulse charge regime were analysed. BioLogic VSP was the device used for almost all experimental measurements. It takes a lot of effort to optimise VSP operation regime. Best operation regime of VSP for the difference method was suggested too.

Master´s thesis is focusing on zero energy building with technical equipment. The building was built in 70. decade of last century. It has been using for sport and cultular events until these days. Restaurant was connected to sport hall. First part is focusing on zero energy building and technical equipment, their using, combination and optimal connecting in systém. Second part solving how many fotovoltaic panels must be in the system to reching economic advantage. In third part is solving how to connecting fotovoltaic panels to the system.

The transportation sector consumes around 70% of all petroleum in the US. In recent years, there have been improvements in the efficiency of the vehicles, and hybrid techniques that have been used to improve efficiency for conventional combustion vehicles. Hydraulic systems have been used as an alternative to conventional electric regenerative systems with good results. It has been proven that hydraulic systems can improve energy consumption in conventional combustion vehicles and in refuse collection vehicles. The control strategy has a large impact on the performance of the system and studies have shown the control strategy selection should be optimized and selected based on application. The performance of a hydraulic accumulator was compared with the performance of a set of ultracapacitors with the same energy storage capacity. The energy efficiency for the ultracapacitor was around 79% and the energy efficiency of the hydraulic accumulator was 87.7%. The power/mass ratio in the set of ultracapacitors was 2.21 kW/kg and 2.69 kW/kg in the hydraulic accumulator. The cost/power ratio is 217 US$/kW in the ultracapacitors and 75 US$/kW in the hydraulic accumulator. Based on these results, the hydraulic accumulator was selected as the energy storage device for the system. A testbench was designed, modeled, implemented to test the energy storage system in different conditions of operation. The experimental results of the testbench show how system can be actively controlled for different operating conditions. The operating conditions in the system can be adjusted by changing the number of rheostats connected to the electric generator. Different variables in the system were measured such as the angular shaft speed in the hydraulic pump, the torque and speed in the hydraulic motor, the pressure in the system, the flow rate, and the current and voltage in the electric generator. The control algorithm was successfully implemented, the results for the pressure in the system and the angular speed in the electric generator show how the control system can follow a desired reference value. Two different controllers were implemented: one controller for the pressure in the system, and one controller for the speed.

I denna rapport utreds hur systemdesignen av lågspänningsfördelningen för järnvägen kan kostnadseffektiviseras. I dagsläget har det utarbetats en norm kring systemdesignen som tenderar att efterbildas från år till år vilket har medfört brist på innovation inom området. Syftet med arbetet var att designa två typstationer med signalställverken M11 respektive M95, där placering samt nominell storlek av UPS:er skulle fastställas för att tillhandahålla en kostnadseffektiv lösning. Dessutom skulle kablage dimensioneras för typstationerna samt se över möjligheten att ersätta UPS:er med likriktarsystem. Stationerna baserades på två redan existerande driftplatser, Fagersta C (M11) och Skänninge (M95). Slutligen skulle olika energilagringsalternativ för UPS-system jämföras för att tillhandahålla det lämpligaste alternativet. Genom simuleringar och beräkningar i bland annat datorprogrammet El-Vis har lågspänningsfördelningen dimensionerats för typstationerna. Arbetet visar på att ett distribuerat UPS-system är att föredra ur ett ekonomiskt perspektiv gentemot ett centraliserat UPS-system. Vidare har det konstaterats att likriktarsystemet Rectiverter kan ersätta UPS:er samt att ackumulatorer är det mest passande energilagringsalternativet. / This report identifies how the system design of low voltage power distribution of the railway can be more cost effective. In the current situation there is a norm on the system design that tends to be replicated each year. This has brought a lack of innovation in the field. The purpose of the thesis was to come up with two model stations with the interlocking system M11 respectively M95, where the positioning and nominal size of the UPS:s would be determined to provide a cost effective solution. Furthermore, the cable dimensioning of the model stations was computed as well as the possibility of replacing UPS-systems with rectifier-systems. The model stations were based on two already existing operating sites, Fagersta C (M11) and Skänninge (M95). Lastly, different energy storage alternatives for UPS-systems were compared to acquire the most appropriate choice. Through simulations and calculations in, inter alia, the computer program El-Vis, the low voltage power distribution was dimensioned for the model stations. The thesis shows that a distributed UPS-system is preferred in an economical point of view compared to a centralized UPS-system. Furthermore, the thesis establishes that the rectifier system Rectiverter can replace UPS:s. It also states that accumulators are the most suitable alternative for energy storage.

Hydraulic piston accumulators play a major role especially within the field of stationary hydraulics. The calculation of the amount of hydraulic energy which can be stored in such an accumulator is crucial when it comes to a precise system design. The knowledge of the temperature and pressure within the accumulator is required in order to calculate the amount of energy to be stored. The state of the art solution to estimate the state of change of such an accumulator is the implementation of a costly measurement system within the accumulator which tracks the position of the piston. The goal of this paper is to develop and to analyse a time efficient simulation approach for the gaseous phase within a piston accumulator depending on the accumulator’s load cycle. Temperature, pressure, density and velocity profiles inside of the gaseous phase are calculated transiently in order to achieve that goal. The simulation model is derived in one dimensional environment to save computational effort. Having derived a valid model of the gaseous phase it will be possible in future works to replace the expensive position measurement system by pressure and temperature transducers and then use the model to calculate the position of the piston and therefore estimate the state of change.

Various academic studies show that in the use of common ICE Off-road Vehicles only about 10-15% of the available power at fuel level is actually transformed into useful energy for the actuators. Particularly the Directional Control Valves are responsible for the dissipation of about 35-40% of the hydraulic energy available at the pump level. The machine electrification trend makes it even more urgent to optimize the hydraulic system to ensure greater performance and higher battery autonomy. Traditional Directional Control Valves design solutions neglect important opportunities for reducing losses and improve internal regeneration. Especially, energy recovery is rarely applied and in any case by means of important superstructures which considerably increase the costs of the system. This paper presents an innovative Directional Control Valve layout, based on the Downstream Compensation approach that, in a simple and cost-effective design, allows to recover a considerable amount of energy from both the inertial loads and the simultaneous use of multiple actuators at different pressure level. The proposed layout performance and efficiency are studied through lumped element simulation and laboratory experimental tests.

This paper addresses the necessity of a correct hydraulic accumulator pre-charge pressure for the optimum performance and in some cases even the essential function of the corresponding hydraulic application. In this context HYDAC has developed a smart product for predictive monitoring of the pre-charge pressure without any need to do a measurement on the gas side of the accumulator – the p0-Guard. The paper gives an overview on the conventional way of checking the pre-charge pressure, the function of the monitoring device and points out the benefits of a predictive monitoring of the accumulator precharge pressure. The benefits are clearly depicted by an analytical view as well as on practical example.

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L’objectif de ce travail a été de mettre en place un système original capable de produire et stocker l’énergie à partir de la lumière dans un dispositif unique. Pour ce faire, nous avons choisi d’adapter l’électrode photo-sensible d’une DSSC sur un système d’accumulateur électrochimique. La première partie de ce travail a été de mettre en place la technique de spectroscopie EIS-λ, basée sur la spectroscopie d’impédance électrochimique couplée à un balayage en longueur d’onde de la lumière incidente. L’objectif de cette mesure est d’identifier et de quantifier les différents mécanismes de transfert électroniques, photo-dépendant ou non, ayant lieu à la surface de l’électrode photo-sensible, ainsi que les processus de désactivation des états excités des sensibilisateurs. Nous nous sommes ensuite penchés sur la recherche des conditions optimales d’utilisation de deux coadsorbants — l’acide bismethoxyphenyl phosphinique ou BMPP et l’acide chenodesoxycholique ou CDCA — avec le sensibilisateur de référence N719. Nous avons également quantifié leurs activités shield et anti-π-stacking grâce à la technique EIS-λ. Nous avons ainsi réalisé une DSSC présentant un rendement de photo-conversion de 8,3% en utilisant le co-adsorbant BMPP dans un ratio [co-ads]/[S] = 1, contre 7,2% dans les conditions de référence — avec le coadsorbant CDCA utilisé dans un ratio [co-ads]/[S] = 10. Par la suite, nous avons imaginé et synthétisé trois complexes de ruthénium hydrophiles originaux dont nous avons testé le pouvoir de photo-conversion dans des DSSC à électrolyte 100% aqueux, en présence des co-adsorbants sélectionnés. Ces systèmes ont permis de dépasser le pouvoir de photo-conversion du sensibilisateur N719, dans l’eau, avec un rendement maximal obtenu de 1,31%. Enfin, nous avons sélectionné la meilleure combinaison sensibilisateur / co-adsorbant afin de réaliser une électrode photo-sensible que nous avons implémentée dans un système original d’accumulateur électrochimique à base d’électrolytes aqueux. Le système ainsi mis en place constitue aujourd’hui le premier dispositif fonctionnel d’accumulateur 100% aqueux photo-rechargeable à partir d’une électrode mésoporeuse photo-sensibilisée / The aim of this work was to imagine and to develop a new system able to produce and store energy from sunlight in a single device. For this purpose, the photo-sensitive electrode of a DSSC has been adapted to an electrochemical accumulator. The first part of this work was to develop a new spectroscopic technique, called EIS-λ and based on electrochemical impedance spectroscopy combined to incident light wavelength sweep. This technique has proved its capacity to identify and quantify the different mechanisms of electron transfer over the surface of the semiconducting material and their dependency to incident wavelength, together with the various deactivation processes of the excited state of the sensitizer. Then, we investigated the best conditions to use two different co-adsorbents — namely bis-methoxyphenylphosphinic acid, or BMPP, and chenodesoxycholic acid, or CDCA — with the reference sensitizer N719. The shield and anti-π-stacking activities of the two coadsorbents has been characterized using EIS-λ technique. DSSC with a photo-conversion yield of 8,3% has been prepared in the lab using BMPP in a ratio [co-ads]/[S] = 1 while reference conditions – namely with CDCA in a ratio [co-ads]/[S] = 10 — only gave 7,2%. Besides, we have designed and synthesized three original hydrophilic ruthenium complexes, then tested their photo-conversion properties in DSSC with 100% aqueous electrolytes. Such systems, with the selected co-adsorbents, allowed 1,31% photo-conversion yield to be obtained, which is two times larger than the efficiency exhibited by N719 in the same electrolyte conditions. Finally the best combination sensitizer / co-adsorbent has been selected to achieve a photo-sensitive electrode which has been implemented in an original electrochemical accumulator with aqueous electrolytes. This system represents the first functional device of a 100% aqueous accumulator, which is photo-reloadable with a photosensitized mesoporous electrode

Low noise low division 2 GHz RF synthesizer integrated circuits (ICs) are conventionally implemented in some form of HBT process such as SiGe or GaAs. The research in this dissertation differs from convention, with the aim of implementing a synthesizer IC in a more convenient, low-cost Si-based CMOS process. A collection of techniques to push towards the noise and frequency limits of CMOS processes, and possibly other IC processes, is then one of the research outcomes. In a synthesizer low N-divider ratios are important, as high division ratios would amplify in-band phase noise. The design methods deployed as part of this research achieve low division ratios (4 ≤ N ≤ 33) and a high phase comparison frequency (>100 MHz). The synthesizer IC employs a first-order fractional-N topology to achieve increased frequency tuning resolution. The primary N-divider was implemented utilising current mode logic (CML) and the fractional accumulator utilising conventional CMOS. Both a conventional CMOS phase frequency detector (PFD) and a CML PFD were implemented for benchmarking purposes. A custom-built 4.4 GHz synthesizer circuit employing the IC was used to validate the research. In the 4.4 GHz synthesizer circuit, the prototype IC achieved a measured in-band phase noise plateau of L( f ) = -113 dBc/Hz at a 100 kHz frequency offset, which equates to a figure of merit (FOM) of -225 dBc/Hz. The FOM compares well with existing, but expensive, SiGe and GaAs HBT processes. Total IC power dissipation was 710 mW, which is considerably less than commercially available GaAs designs. The complete synthesizer IC was implemented in Austriamicrosystems‟ (AMS) 0.35 μm CMOS process and occupies an area of 3.15 x 2.18 mm2. / Dissertation (MEng)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted