<p>Using <i>ab initio</i> electronic structure calculations based on density functional theory the crystal, electronic and magnetic structures of selected materials have been investigated. The materials which are the subjects of these investigations can be divided into two groups. Parts of the investigations have concerned actinides and rare earths, heavy elements with an <i>f</i>-shell electronic configuration. Here the effects of delocalization on EuCo₂P₂ have been studied as well as the effect of including relativistic interactions when calculating the properties of thorium. For EuCo₂P₂ it was found that at a low pressure the valence state of Eu changes from divalent to trivalent with associated effects on the crystal structure and magnetic state.</p><p>The other group of materials investigated are the metal-hydrogen and metal- lithium systems. Both of these have an important technological application in the form of batteries. Here the emphasis of the investigations has been the fundamental understanding of the mechanism of hydrogenation, and a novel theory explaining the driving force behind hydrogenation is suggested. Vanadium hydride, VH_x, has been examined in detail and the reason for the anomalous non-isotropic expansion is explained. A scheme to make vanadium magnetic is also proposed. </p><p>Finally a method based on electron-hole coupled Green's functions has been used to facilitate the comparison between calculated electronic structures and X-ray absorption spectra. In connection to this a novel theory of charge transfer in the X-ray absorption process applied to transition metal oxides and lithium intercalated transition metal oxides is presented.</p>

Using ab initio electronic structure calculations based on density functional theory the crystal, electronic and magnetic structures of selected materials have been investigated. The materials which are the subjects of these investigations can be divided into two groups. Parts of the investigations have concerned actinides and rare earths, heavy elements with an f-shell electronic configuration. Here the effects of delocalization on EuCo2P2 have been studied as well as the effect of including relativistic interactions when calculating the properties of thorium. For EuCo2P2 it was found that at a low pressure the valence state of Eu changes from divalent to trivalent with associated effects on the crystal structure and magnetic state. The other group of materials investigated are the metal-hydrogen and metal- lithium systems. Both of these have an important technological application in the form of batteries. Here the emphasis of the investigations has been the fundamental understanding of the mechanism of hydrogenation, and a novel theory explaining the driving force behind hydrogenation is suggested. Vanadium hydride, VHx, has been examined in detail and the reason for the anomalous non-isotropic expansion is explained. A scheme to make vanadium magnetic is also proposed. Finally a method based on electron-hole coupled Green's functions has been used to facilitate the comparison between calculated electronic structures and X-ray absorption spectra. In connection to this a novel theory of charge transfer in the X-ray absorption process applied to transition metal oxides and lithium intercalated transition metal oxides is presented.

The domestic sector will play an important role in the decarbonisation and decentralisation of the energy sector in the future. Installation numbers of building-integrated small-scale energy systems such as photovoltaics (PV), wind turbines and micro-combined heat and power (CHP) have significantly increased. However, the power output of PV and wind turbines is inherently linked to weather conditions; thus, the injected power into the public grid can be highly intermittent. With the increasing share of renewable energy at all voltage levels challenges arise in terms of power stability and quality. To overcome the volatility of such energy sources, storage technologies can be applied to temporarily decouple power generation from power consumption. Two emerging storage technologies which can be applied at residential level are hydrogen systems and vanadium-redox-flow-batteries (VRFB). In addition, the building-integrated energy sources and storage system can be combined to form a hybrid renewable energy system (HRES) to manage the energy flow more efficiently. The main focus of this thesis is to investigate the dynamic performance of two emerging energy storage technologies, a hydrogen loop composed of alkaline electrolyser, gas storage and proton exchange membrane (PEM) fuel cell, and a VRFB. In addition, the application of building-integrated HRES at customer level to increase the self-consumption of the onsite generated electricity and to lower the grid interaction of the building has been analysed. The first part deals with the development of a research test-bed known as the Hybrid Renewable Energy Park (HREP). The HREP is a residential-scale distributed energy system that comprises photovoltaic, wind turbine, CHP, lead acid batteries, PEM fuel cell, alkaline electrolyser and VRFB. In addition, it is equipped with programmable electronic loads to emulate different energy consumption patterns and a charging point for electric vehicles. Because of its modular structure different combinations of energy systems can be investigated and it can be easily extended. A unified communication channel based on the local operating network (LON) has been established to coordinate and control the HREP. Information from the energy systems is gathered with a temporal resolution of one second. Integration issues encountered during the integration process have been addressed. The second part presents an experimental methodology to assess the steady state and dynamic performance of the electrolyser, the fuel cell and the VRFB. Operational constrains such as minimum input/output power or start-up times were extracted from the experiments. The response of the energy systems to single and multiple dynamic events was analysed, too. The results show that there are temporal limits for each energy system, which affect its response to a sudden load change or the ability to follow a load profile. Obstacles arise in terms of temporal delays mainly caused by the distributed communication system and should be considered when operating or simulating a HRES at system level. The third part shows how improved system models of each component can be developed using the findings from the experiments. System models presented in the literature have the shortcoming that operational aspects are not adequately addressed. For example, it is commonly assumed that energy systems at system level can respond to load variations almost instantaneously. Thus, component models were developed in an integrated manner to combine theoretical and operational aspects. A generic model layout was defined containing several subsystems, which enables an easy implementation into an overall simulation model in MATLAB®/Simulink®. Experimental methods were explained to extract the new parameters of the semi-empirical models and discrete operational aspects were modelled using Stateflow®, a graphical tool to formulate statechart diagrams. All system models were validated using measured data from the experimental analysis. The results show a low mean-absolute-percentage-error (<3%). Furthermore, an advanced energy management strategy has been developed to coordinate and to control the energy systems by combining three mechanisms; statechart diagrams, double exponential smoothing and frequency decoupling. The last part deals with the evaluation, operation and control of HRES in the light of the improved system models and the energy management strategy. Various simulated case studies were defined to assess a building-integrated HRES on an annual basis. Results show that the overall performance of the hydrogen loop can be improved by limiting the operational window and by reducing the dynamic operation. The capability to capture the waste heat from the electrolyser to supply hot water to the residence as a means of increasing the overall system efficiency was also determined. Finally, the energy management strategy was demonstrated by real-time experiments with the HREP and the dynamic performance of the combined operation has been evaluated. The presented results of the detailed experimental study to characterise the hydrogen loop and the VRFB as well as the developed system models revealed valuable information about their dynamic operation at system level. These findings have relevance to the future application and for simulation studies of building-integrated HRES. There are still integration aspects which need to be addressed in the future to overcome the proprietary problem of the control systems. The innovations in the HREP provide an advanced platform for future investigations such as electric-vehicles as decentralised mobile storage and the development of more advanced control approaches.

Worldwide interest in renewable energy systems has increased dramatically, due to environmental concerns like climate change and other factors. Wind power is a major source of sustainable energy, and can be harvested using both horizontal and vertical axis wind turbines. This thesis presents studies of a vertical axis wind turbine performance for applications in urban areas. Numerical simulations with FLUENT software are presented to predict the fluid flow through a novel Zephyr vertical axis wind turbine(VAWT). Simulations of air flow through the turbine rotor were performed to analyze the performance characteristics of the device. Major blade geometries were examined. A multiple reference frame (MRF) model capability of FLUENT was used to express the dimensionless form of power output of the wind turbine as a function of the wind freestream velocity and the rotor's rotational speed. The simulation results exhibit close agreement with a stream-tube momentum model. / UOIT

Vätgas producerad från förnybar el har en stor potential att minska utsläppen från flera olika branscher. Detta genom att införa nya innovativa ändamål och även genom storskalig ersättning av vätgas som idagproduceras med fossila bränslen. Men för en storskalig förändring behöver kostnaden för förnybar vätgasproduktionsjunka. Förutom den generella teknikutveckling och storskalighetsfördelar finns det effektivasätt att bättre nyttja existerade teknik för att sänka kostnaden för vätgas mot slutkund. Exempel på detär försäljning av spillvärme från systemet till lokala fjärrvärmesystem samt nyttjandet av vätgassystemetför att agera på balansmarknader. Denna studie undersökte hur ett vätgassystem innehållandes elektrolysörer, lager, kompressor och gasturbinerkan utformaras och driftas för att på ett effektivt sätt agera på marknader för el och vätgas. Det gjordes genom att studera hur en anläggning kopplat till vindkraftsproduktion genom ett Power purchaseagreement (PPA) kan utformas och driftas för att tillgodose ett industriellt vätgasbehov. Stort fokus ladespå hur ett sådant system kunde nyttjas för att agera på balansmarknader genom att sälja stödtjänsteroch hur erbjudandet av stödtjänster påverkade resten av vätgassystemet. Fallstudien som genomfördes utgick från ett potentiellt vätgassystem i Helsingborg med två stora industriellakunder som ville skifta från nyttjandet av vätgas producerad genom ångreforming till vätgasproducerad genom elektrolys med förnybar el. Då mycket fokus i studien var på balansmarknader ochflexibilitet ansågs PEM-elektrolsyören var den bäst lämpade. Vidare valdes komprimerad vätgaslagringoch ett antal alternativ för vätgasturbiner. Då produktionen var kopplad till en intermittent energikällagjordes bedömningen att systemet skulle vara assisterat med möjligheten att handla el på dagenföre- ochintradagsmarknaden. Om all eltillförsel skulle ske från vindkraften hade lagret behövt vara orimligt stortför att säkerställa förmågan att klara leveranskrav under perioder med låg elproduktion. För att analyseradet valda systemet modellerades ett vätgassystem i Energy Optima 3, en programvara som nyttjar linjärprogrammering för totaloptimering av energisystem. För att undersöka hur dem olika komponenternaskulle dimensioneras gjordes ett antal helårsoptimeringar med tidsupplösning om en timme för att se hursystemet presterade med olika kombinationer av storlek på elektrolysör, lager samt typ av gasturbin. Vid värdering av vilken konfiguration som var mest lämpad användes den utjämnade vätgaskostnaden.Den konfiguration som bedömdes vara mest lämpad för det studerade fallet var en PEM-elektrolysör på 55MW, ett komprimerat lager som motsvarade 12 timmars behov från kunderna och en gasturbin på 24 MW.Den konfigurationen kunde under den studerade tidsperioden producera vätgas till en utjämnad kostnadpå 4,7 EUR/kg. Allmänt kan sägas att studien visade att agerande på balansmarknaden gav stor intäkterför systemet och hade en betydande påverkan på systemets lönsamhet. Försäljning av spillvärme hade idet studerade fallet inte en lika kritiskt påverkan på systemet då intäkter var betydligt lägre. En viktigtinsikt från studien var att värdet av att agera på dem olika marknaderna ofta ställdes mot varandradå deltagande på balansmarknaden ibland innebar att elektrolysören inte kunde nyttja all kapacitet.Samtidigt innebar uppbunden kapacitet på balansmarknaden att flexibiliteten i systemet inte kundenyttjas för att agera på intradagsmarkanden och/eller hantering av prognosfel från vindkraftsproduktion. Studien visade allmänt att utformning och prissättning av PPA har en avgörande roll i ett vätgassystemsgångbarhet. I studien användes ett pay-as-produced-avtal, vilket resulterade i att elektrolysören vid vissatillfällen hade underskott på el (och el från intradagsmarknaden behövde köpas in för att kompensera)och vid vissa tillfällen var det överskott på el (och el behövde säljas vidare på dagenföre- eller intradagsmarknaden.)Vidare bedömdes försäljning av vätgas med långsiktiga kontrakt vara det mest lämpadealternativet då det säkrar intäkter för vätgas producenter och tillgången på vätgas till för industrierna. / Hydrogen produced from renewable electricity has significant potential to reduce emissions in variousindustries, both through new innovative applications and as a large-scale replacement for hydrogen currentlyproduced using fossil fuels as a feed stock. However, in order for large scale adaptation of renewablehydrogen the costs associated with it must decrease. In addition to technological advancements and economiesof scale, there are effective ways to better utilize existing technology to lower the cost of hydrogenfor end user. Examples include selling excess heat from the system to local district heating networks ifthe location of the electrolyzer allows for it, as well as utilizing the hydrogen system to participate inbalancing markets. This study investigated how hydrogen systems containing electrolyzers, storage, compressors, and gasturbines can be designed and operated to effectively participate in electricity and hydrogen markets. Itwas done by studying how a facility connected to wind power production through a Power PurchaseAgreement (PPA) can be designed and operated to meet an industrial hydrogen demand. A major focuswas placed on how such a system could be utilized to participate in balancing markets by providingancillary services and how offering these services affected the rest of the hydrogen system. The case study was focused on a potential hydrogen system in Helsingborg with two large industrialcustomers interested in transitioning from steam reforming hydrogen production to electrolysis using renewableelectricity. As the study heavily emphasized balancing markets and flexibility, a PEM electrolyzerwas chosen over other technologies. Additionally, compressed hydrogen storage and several options forhydrogen gas turbines were selected. Since the production was linked to an intermittent energy source,it was assessed that the system would need to be supported by trading electricity on the day-ahead andintraday markets. If all electricity supply were to come from wind power, the hydrogen storage wouldhave to be unreasonably large to ensure the ability to meet delivery requirements during periods of lowelectricity production. To analyze the selected system, a hydrogen system was modeled using EnergyOptima 3, a software that utilizes linear programming for total optimization of energy systems. Severalyear-long optimizations with 1-hour resolution were performed to examine how the system performedwith different combinations of electrolyzer and storage sizes, as well as types of gas turbines. When evaluating which configuration was most suitable, the levelized cost of hydrogen (LCOH) was used.The configuration deemed most suitable for the studied case consisted of a 55 MW PEM electrolyzer,compressed storage equivalent to 12 hours of customer demand, and a 24 MW gas turbine. This configurationcould produce hydrogen at a levelized cost of 4.7 EUR/kg during the studied period. Overall,the study demonstrated that participating in the balancing market generated significant revenue for thesystem and had a substantial impact on its profitability. The sale of waste heat had a less critical effecton the system in the studied case, as the revenues were considerably lower. An important insight fromthe study was that the value of participating in different markets was often weighed against each other,as participating in the balancing market some times meant that the electrolyzer could not utilize itsfull capacity, while having tied-up capacity in the balancing market limited the system’s flexibility toparticipate in the intraday market and/or manage forecast errors related to wind power production. The study generally showed that the design and pricing of Power Purchase Agreements (PPAs) plays acrucial role in the viability of a hydrogen system. In the study, a pay-as-produced design was used, whichresulted in both electricity deficits and surpluses at certain times. Furthermore, selling hydrogen throughlong-term contracts was deemed the most suitable option for large industrial producers, as it ensuresrevenue for hydrogen producers and a stable supply of hydrogen for the industries.