The consequences of over-reliance on fossil fuels for energy supply, namely climate change and security of supply, are pushing for the use of local, renewable energy sources which are usually variable in nature, prompting the need for energy storage. Today, there is a trend towards distributed energy storage, justified by the distributed nature of renewable energy sources and the important share of energy consumption in buildings. Important information on such small scale energy storage installations, however, is still missing and the results of the existing literature vary widely. To account for these research gaps, a thorough characterisation of energy storage technologies is performed, together with the dimensioning and optimisation of such installations in buildings, as well as some aspects of their impact on the grid.It is found that storage is still far from grid parity and expensive when compared to other solutions, although necessary for a high share of renewables. Also, energy storage is subject to important economies of scale and technical limitations that counter the reasoning for a distributed approach. There is an important lack of practical information on several energy storage technologies, and many studies on distributed storage use downsized values from large-scale installations that do not correctly depict smaller installations, leading to biased results. Nevertheless, today, lithium-ion batteries seem to be the most appropriate electrical energy storage technology for buildings, being well adapted to short term storage. On the other hand, a very high share of renewables will push for long term storage, itself a challenge given the high cost brought by a low utilisation factor. A high share of distributed generation also impacts the grid, a problem which most final consumers have no economic incentive to mitigate. Storage by itself, without a sound control strategy, does not help as it tends to increase the load variability while the peak load remains the same. Specific control algorithms could change that but incentives must be present, namely through the adaptation of current grid tariffs that do not correctly allocate existing costs. These findings are essential in the future planning of energy systems as well as in energy policy. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

abstract: Polycrystalline CdS/CdTe solar cells continue to dominate the thin-film photovoltaics industry with an achieved record efficiency of over 22% demonstrated by First Solar, yet monocrystalline CdTe devices have received considerably less attention over the years. Monocrystalline CdTe double-heterostructure solar cells show great promise with respect to addressing the problem of low Voc with the passing of the 1 V benchmark. Rapid progress has been made in driving the efficiency in these devices ever closer to the record presently held by polycrystalline thin-films. This achievement is primarily due to the utilization of a remote p-n heterojunction in which the heavily doped contact materials, which are so problematic in terms of increasing non-radiative recombination inside the absorber, are moved outside of the CdTe double heterostructure with two MgyCd1-yTe barrier layers to provide confinement and passivation at the CdTe surfaces. Using this design, the pursuit and demonstration of efficiencies beyond 20% in CdTe solar cells is reported through the study and optimization of the structure barriers, contacts layers, and optical design. Further development of a wider bandgap MgxCd1-xTe solar cell based on the same design is included with the intention of applying this knowledge to the development of a tandem solar cell constructed on a silicon subcell. The exploration of different hole-contact materials—ZnTe, CuZnS, and a-Si:H—and their optimization is presented throughout the work. Devices utilizing a-Si:H hole contacts exhibit open-circuit voltages of up to 1.11 V, a maximum total-area efficiency of 18.5% measured under AM1.5G, and an active-area efficiency of 20.3% for CdTe absorber based devices. The achievement of voltages beyond 1.1V while still maintaining relatively high fill factors with no rollover, either before or after open-circuit, is a promising indicator that this approach can result in devices surpassing the 22% record set by polycrystalline designs. MgxCd1-xTe absorber based devices have been demonstrated with open-circuit voltages of up to 1.176 V and a maximum active-area efficiency of 11.2%. A discussion of the various loss mechanisms present within these devices, both optical and electrical, concludes with the presentation of a series of potential design changes meant to address these issues. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

<p dir="ltr">With climate change creating the need for renewable energy to replace fossil fuels, solar energy technologies are primed to dominate the energy sector. And while photovoltaics have improved significantly in recent decades, continued evolution of this technology requires research into new fabrication techniques and new materials. The solution processing of metal chalcogenide semiconductors offers an opportunity to fabricate photovoltaics in a low-cost and high-throughput way. However, for this methodology to make a commercial impact a variety of challenges around the fundamental chemistry and materials science need to be addressed. Furthermore, while solution processing has been applied heavily to the Cu(In,Ga)(S,Se)₂ family of materials, these techniques can also open doors for emerging materials like Cu₂ZnSnSe₄, Ag₂ZnSnSe₄, and the chalcogenide perovskites.</p><p dir="ltr">In solution processed Cu(In,Ga)(S,Se)₂ devices, researcher have generally started with a Cu(In,Ga)S₂ film that is then selenized to form the final Cu(In,Ga)(S,Se)₂ material. However, this process has been connected to the formation of a problematic “fine-grain” layer. To solve this issue, the molecular precursors from amine-thiol chemistry were modified to produce soluble molecules with metal selenium bonding. This enabled direct solution deposition of CuInSe₂ films that could be processed without forming a fine grain layer.</p><p dir="ltr">Reactive dissolution chemistry (or “alkahest” chemistry) is useful for solution processing because it can enable the direct use of metal or metal chalcogenide precursors, bypassing the potential impurities from metal salt precursors. However, the commonly used amine-thiol reactive solvent system is better suited to making metal sulfides than metal selenides because the thiol acts as a sulfur source. To address this limitation, a new alkahest based on alkylammonium polyselenide solutions was developed which could reactively dissolve a wide range of metals, metal chalcogenides, and metal oxides. This generalizable chemistry enabled the synthesis of a wide range of binary and multinary metal chalcogenides including Cu(In,Ga)Se₂, Cu₂ZnSnSe₄, and Ag₂ZnSnSe₄.</p><p dir="ltr">Emerging metal chalcogenide semiconductors composed of earth-abundant and non-toxic elements that can exhibit strong optoelectronic properties and high stability are a target of significant interest. Chalcogenide perovskites like BaZrS₃ and BaHfS₃ are an intriguing option to satisfy these requirements but have rarely been studied because of synthesis difficulties, historically being made by solid-state reactions or the sulfurization of oxides around 1000 °C. Here a solution-based approach that only requires moderate temperatures of 550-575 °C was developed utilizing a hybrid ink containing soluble metal thiolates and nanoparticulate metal hydrides.</p><p dir="ltr">The hybrid ink was an important proof of concept that chalcogenide perovskites could be synthesized at these moderate temperatures. However, it relies on complex and difficult to handle precursors. A simpler route would be to use air-stable precursors to make an oxide perovskite and subsequently sulfurize the material. However, this route has historically used excessively high temperatures. Therefore, a new sulfurization step was conceived based on thermodynamic arguments that includes both sulfur and hafnium sulfide as an oxygen sink. This redesigned sulfurization enabled the conversion of BaZrO₃ into BaZrS₃ at temperatures around 575 °C.</p><p dir="ltr">Finally, an energy systems and economic analysis was performed to consider how photovoltaics might be incorporated into agricultural lands. This work showed that when compared with traditional photovoltaics or a PV Aglectric concept, using corn for ethanol is an inefficient way to generate both food and energy from a given unit of land.</p>

No description available.

Der voranschreitende Ausbau von erneuerbaren Energien (EE) Technologien bringt eine zunehmend dezentralisierte Energieproduktion mit sich. Hieraus ergeben sich unterschiedliche regionalwirtschaftliche Effekte und Wertschöpfungspotenziale für den ländlichen und den urbanen Raum. Ziel dieser Studie ist die Quantifizierung der Wertschöpfung im Kontext von Solarstromerzeugung durch Photovoltaik (PV)-Anlagen. Hierzu wird eine allgemeine Methodik zur Bestimmung der direkten, indirekten und induzierten Wertschöpfungseffekte erstellt, die aktuelle Entwicklungen berücksichtigt und zunächst auf das Praxisbeispiel der Stadt Leipzig im Jahr 2019 angewandt. Die Ergebnisse können Kommunen bei der Frage unterstützen, ob und inwiefern es sich im Hinblick auf veränderte regulatorische Rahmenbedingungen auch in Zukunft lohnt, den PV-Ausbau vor Ort voranzutreiben und geeignete Ansatzpunkte hierfür zu identifizieren. Im Ergebnis zeigt sich, dass die Wertschöpfungseffekte für verschiedene Anlagengrößen variieren. Während kleinere Anlagen eine höhere Wertschöpfung pro Kilowattpeak (kWp) generieren, zeigen große Dach- und Freiflächenanlagen durch ihre Skalierung einen größeren Effekt auf die Wertschöpfung in absoluten Werten. Gleichzeitig fließt ein erheblicher Anteil der generierten Wertschöpfung aus der Standortkommune ab. Insgesamt beziffert sich die kommunal verbleibende Wertschöpfung aus dem PV-Betrieb in der Stadt Leipzig 2019 auf rund 4,5 Mio. Euro.

No description available.

A crucial challenge introduced by the decentralized installations of photovoltaic (PV) systems in the residential sector, is the mismatch between PV electricity generation and the load curve for energy consumption. To overcome this incompatibility between production and consumption, energy storage and demand response are seen as effective solutions. Smart meters and the installation of intelligent smart appliances in homes have paved the way for efficient energy consumption monitoring and active household load control in the residential sector.  The aim of the thesis work is to develop a dynamic energy management algorithm tailored to optimize the energy consumption pattern of controllable household assets to maximize PV selfconsumption. A rolling horizon algorithm based dynamic model was designed using mixedinteger linear programming (MILP) and later compared with the baseline model to understand the real-time operational benefits of the rolling horizon approach.  Analyzing device scheduling patterns based on the feed-in-tariff showed considerable differences in the scheduling approach for both optimization models. A comparative analysis was conducted to understand the system benefits offered by both optimization models under different feed-in-tariff structures. Higher self-consumption rates were achieved through annual scheduling approach, but it does not reflect the real-time operation of the systems in the household. A rolling horizon optimization reflects the real-time operation of the energy system and has a lower self-consumption rate due to a limited optimization horizon. The method indicates the significant potential of self-consumption specially in lieu of decreasing feed-in tariffs. / En viktig utmaning som de decentraliserade installationerna av solcellssystem i bostadssektorn innebär är att elproduktionen från solcellerna inte stämmer överens med belastningskurvan för energiförbrukningen. För att komma till rätta med denna oförenlighet mellan produktion och konsumtion ses energilagring och efterfrågeflexibilitet som effektiva lösningar. Smarta mätare och installation av intelligenta smarta apparater i hemmen har banat väg för effektiv övervakning av energiförbrukningen och aktiv styrning av hushållens belastning i bostadssektorn.  Syftet med avhandlingen är att utveckla en dynamisk energihanteringsalgoritm som är skräddarsydd för att optimera energiförbrukningsmönstret för kontrollerbara hushållstillgångar för att maximera självförbrukningen av solceller. En dynamisk modell baserad på en algoritm med rullande horisont utformades med hjälp av blandad linjär programmering (MILP) och jämfördes senare med basmodellen för att förstå de operativa realtidsfördelarna med metoden med rullande horisont. Analysen av schemaläggningsmönster för enheter baserat på inmatningstariffen visade att det fanns betydande skillnader i schemaläggningsmetoden för båda optimeringsmodellerna. En jämförande analys genomfördes för att förstå de systemfördelar som erbjuds av de båda optimeringsmodellerna under olika strukturer för inmatningstariffer. Högre självförbrukningsnivåer uppnåddes genom den årliga schemaläggningsmetoden, men den återspeglar inte realtidsdriften av systemen i hushållet. En optimering med rullande horisont återspeglar energisystemets drift i realtid och har en lägre självförbrukningsgrad på grund av en begränsad optimeringshorisont. Metoden visar på den betydande potentialen för självförbrukning speciellt i stället för minskande inmatningstariffer.