Master's thesis. / Format: PDF. Bibl.

The energy requirements of our planet will continue to grow with increasing world population and the modernization of currently underdeveloped countries. This will force us to search for environmental friendly alternative energy resources. Solar energy by far provides the largest of all renewable energy resources with an average power of 120 000 TW irradiated from the sun which can be exploited through solar electricity, solar fuel, and biomass. Nanostructured materials have been the subject of extensive research as the building block for construction of solar energy conversion devices for the past decades. The nanostructured materials sometimes have peculiar electrical and optical properties that are often shape and size dependent and are not expected in the bulk phase. Recent research has focused on new strategies to control nanostructured morphologies and compositions of semiconductor materials to optimize their solar conversion efficiency. In this dissertation, we discuss the synthesis and characterizations of one dimensional nanostructured TiO₂ based materials and their solar energy conversion applications. We have developed a solvothermal synthesis method for growing densely packed, vertical, single crystalline TiO₂ rutile nanowire arrays with unprecedented small feature sizes of 5 nm and lengths up to 4.4 [mu]m. Because of TiO₂'s large band gap, the working spectrum of TiO₂ is limited to the ultra violet region with photons shorter than 420 nm. We demonstrate that the active spectrum of TiO₂ can be shifted to ~ 520 nm with incorporation of N via nitridation of TiO₂ nanowires in NH₃ flow. In addition, we demonstrate a synergistic effect involving hydrogenation and nitridation cotreatment of TiO₂ nanowires that further redshift the active spectrum of TiO₂ to 570 nm. The Ta and N co-incorporated TiO₂ nanowires were also prepared and showed significant enhancement in photoelectrochemical performance compared to mono-incorporation of Ta or N. This enhancement is due to fewer recombination centers from charge compensation effects and suppression of the formation of an amorphous layer on the nanowires during the nitridation process. Finally, we have developed hydrothermal synthesis of single crystalline TiO₂ nanoplatelet arrays on virtually all substrates and demonstrated their applications in water photo-oxidation and dye sensitized solar cells. / text

The sun is a vast source of renewable energy, which can potentially be used to satisfy the world's increasing energy demand. Yet many material challenges need to be overcome before solar energy conversion can be implemented on a larger scale. This dissertation focuses on materials used for solar energy conversion through photo-electrochemical (PEC) processes. It discusses methods for improving PEC materials, namely mixed metal oxide semiconductors, by nanostructuring, incorporation of additional elements, and application surface electrocatalysts. In this dissertation several material synthesis techniques are detailed. A high vacuum synthesis process known as reactive ballistic deposition (RBD) is used to synthesize nanostructured bismuth vanadate (BiVO₄), which is studied for PEC water oxidation. Additionally, ballistic deposition (BD) is used to incorporate Mo and W into nanostructured BiVO₄ to improve the PEC activity. An array dispenser and scanner system is used to incorporate metals into copper oxide (CuO) and copper bismuth oxide (CuBi₂O₄) and over 3,000 unique material compositions are tested for cathodic photoactivity. The system is also used to test 35 elements as single component metal oxides, mixed metal oxides, and dopants for titanium dioxide (TiO₂) for use in dye-sensitized solar cells (DSCs). Lastly, RBD is used to deposit tungsten semicarbide (W₂C) onto p-type silicon (p-type) substrates as an electrocatalyst for PEC proton reduction. In many cases, the synthesis techniques and new material combinations presented in this dissertation result in improved PEC performance. The materials are thoroughly assessed and characterized to gain insights into their nanostructure, chemical composition, light absorption, charge transport properties, catalytic activity, and stability. / text

M. Tech. Electrical Engineering. / Discusses the study objectives as follows: 1. Description of the extent of roll-out of SHW (Solar Water Heater) as a DSM (Demand Side Management) Programme in Botswana. 2. Identification of SWH implementation obstacles/barriers in Botswana. 3. Provision of a strategy for SWH data capture and verification in Botswana. 4. Evaluation of SWH performance through field measurements. 5. Prediction of SWH performance results using performance predictive simulation models. 6. Extrapolation/quantification of the impact of SWH. 7. Provision of energy management/planning/forecasting tool.

With America’s recent needs for creating jobs, mitigating greenhouse gas emissions, and becoming "energy independent" from foreign nations, the large-scale deployment of solar energy projects has been proclaimed a solution for rapidly generating "clean" energy. Federal agencies have been mandated by law to expedite the siting of utility-scale solar energy projects (USSEPs) on public lands. In particular, the Bureau of Land Management (BLM) has focused on USSEP development by creating a national solar energy program as well as state-specific programs for encouraging USSEP development, and has thus far approved two USSEPs in Arizona. Although operational USSEPs do not emit greenhouse gases, they are not completely benign to the environment. USSEPs incur negative impacts on soils, vegetation, air quality, and other natural and cultural resources. Because USSEPs have the potential to mitigate climate change, yet incur other negative environmental impacts, the reaction of citizen stakeholders such as environmental advocates to public lands USSEP development has been mixed. Environmental advocate groups have both encouraged BLM to build USSEPs, and filed lawsuits discouraging project development. In light of the ability of environmental advocates to influence USSEP development, this study explored the complex opinions of members of environmental organizations, conservation groups, watershed initiatives, and solar industry professionals regarding USSEP development on Arizona public lands. Through a review of relevant literature, a content analysis of BLM environmental review documents, and the distribution and statistical analysis of an opinion survey, the study provides insight into the implications of the current BLM Arizona siting process and specific, up-to-date stakeholder perspectives. The results indicate that while BLM Arizona siting policies do attempt to address environmental concerns, significant concerns about the current USSEP siting process remain, and that environmental advocates' support for public lands USSEPs is lower than their support for renewable energy development in general. Stakeholders reported having low levels of three items: knowledge of current solar technologies, understanding of the current federal USSEP siting process, and confidence that the government will appropriately site solar energy projects. Addressing those items may alleviate tensions between stakeholders and public lands decision-makers, resulting in faster and more environmentally responsible USSEP siting.

Beim Übersetzen von Fachtexten oder Dolmetschen von Fachkonferenzen ist die für das jeweilige Themengebiet verwendete Terminologie von zentraler Bedeutung. In einer Zeit des rasanten technologischen Fortschritts ist es manchmal nicht einfach, immer an die Fachliteratur zu gelangen, die den neuesten Stand der Technik wiedergibt, und dann auch noch adäquate Benennungen in verschiedenen Sprachen zu finden. Gerade im Bereich der erneuerbaren Energien, deren Anteil an der Energiebereitstellung in Deutschland und Europa in den letzten Jahren stetig gewachsen ist (vgl. BMU 1 2010:5) und die die Grundlage der zukünftigen Energieversorgung bilden sollen, gibt es fortlaufend technische Neu- und Weiterentwicklungen auf den verschiedenen Feldern, zu denen neben Wasserkraft, Windenergie, Biomasse, Geothermie, Gezeitenkraft und Photovoltaik auch die Solarthermie, die Umwandlung von Sonnenenergie in Wärme, zählt. Da im Alltag eines Übersetzers oder Dolmetschers meist die Zeit für eine ausgiebige Recherche mit anschließender Dokumentation der Ergebnisse fehlt, kann eine Terminologiearbeit zum entsprechenden Fachgebiet ein gutes Hilfsmittel darstellen. Daher ist das Ziel dieser Arbeit, das Thema Solarthermie fachlich und terminologisch so aufzubereiten, dass es Übersetzern, Dolmetschern, aber auch anderen Interessierten den nötigen Überblick über das Fachgebiet verschafft, auf sprachliche Besonderheiten aufmerksam macht und gleichzeitig als Nachschlagewerk dienen kann. Darüber hinaus kann es als Beitrag zu einer ausbaufähigen Terminologiedatenbank dienen, die nötig sein wird, um der raschen Weiterentwicklung der Technologien in diesem Bereich Rechnung zu tragen. Gerade die Solarthermie ist ein Teilbereich der erneuerbaren Energien, dem auf dem Gebiet der wirtschaftlichen Kooperation und Entwicklungszusammenarbeit mit dem arabischen Raum in Zukunft eine größere Bedeutung zukommen soll. Beispielsweise stellt die Weltbank zusammen mit anderen Investoren 5,5 Mrd. Dollar für den Bau von thermischen Solarkraftwerken in fünf arabischen Ländern, namentlich Algerien, Ägypten, Jordanien, Marokko und Tunesien, zur Verfügung (BETTZIECHE 2009:63, WELTBANK 1 2009). Außerdem sieht die Desertec-Initiative vor, dass bis zum Jahr 2050 15 bis 20 % des europäischen Strombedarfs durch solarthermische Kraftwerke in Nordafrika und dem Nahen Osten gedeckt werden sollen (vgl. DESERTEC). Die vorliegende Arbeit beschäftigt sich aber nicht nur mit der solarthermischen Stromerzeugung, sondern dem gesamten Spektrum der Solarthermie, das daneben auch noch Warmwasserbereitstellung, Raumheizung, solare Kühlung und Prozesswärmeerzeugung umfasst. Auch für diese Anwendungsbereiche gibt es im sonnenreichen arabischen Raum sehr gute Potenziale, was eine Auseinandersetzung mit der arabischen Terminologie dieses Fachgebiets sehr interessant macht.

A novel multi-tank thermal energy storage (TES) was evaluated experimentally and numerically. The multi-tank storage is based on the interconnection of standard hot water storage tanks by a single charge flow loop. Each tank is charged through a thermosyphon loop and natural convection heat exchanger (NCHE). Both series- and parallel-connected configurations were investigated and results show that high degrees of stratification can occur. To predict the performance of the series- and parallel-connected multi-tank TES, a numerical model was developed and implemented in the TRNSYS simulation environment. Laboratory tests were also conducted to measure the unit’s performance under charge conditions representative of combinations of clear and overcast days. The effects of rising and falling charge loop temperatures and power levels on storage temperatures and heat transfer rates were studied and indicated that sequential stratification was achieved in the series-connected storage. Under certain conditions, reverse flow through the thermosyphon loops was identified, leading to destratification and carry-over of heat to the downstream storage tanks. Consequently, a new model was developed and showed to model reverse thermosyphon operation. A subsequent analysis showed that these effects could be minimized by careful system design. To quantify the relative benefits of the sequentially stratified TES, values of exergy stored versus time were determined and compared against fully stratified and fully mixed storages. Results show that the series configuration closely matches the exergy level attained by a perfectly stratified storage. Finally, annual simulations conducted for a typical multi-family installation showed that the multi-tank storage performed at a level comparable to a single, fully stratified, storage. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2009-06-24 00:13:01.142

In the last fifty years, Nunavut has developed a deep dependence on diesel for virtually all of its energy needs, including electricity. This dependence has created a number of economic, environmental and health related challenges in the territory, with an estimated 20% of the territory’s annual budget being spent on energy, thereby limiting the Government of Nunavut’s ability to address other essential infrastructure and societal needs, such as education, nutrition and health care and housing. One solution to address this diesel dependency is the use of renewable energy technologies (RETs), such as wind, solar and hydropower. As such, this thesis explores energy alternatives in Nunavut, and through RETScreen renewable energy simulations, found that solar power and wind power are technically viable options for Nunavut communities and a potentially successful means to offset diesel-generated electricity in Nunavut. However, through this analysis it was also discovered that accurate data or renewable resources are often unavailable for most Nunavut communities. Moreover, through qualitative open-ended interviews, the perspectives of Nunavut residents with regards to developing RETs in Nunavut were explored, and it was found that respondents generally supported the use of renewable energy in their communities, while acknowledging that there still remains a knowledge gap among residents regarding renewable energy, stemming from a lack of communication between the communities, government and the utility company. In addition, the perceived challenges, opportunities and gaps that exist with regards to renewable energy policy and program development were discussed with government policy-makers through further interviews, and it was discovered that often government departments work largely independently of each other rather than collaboratively, creating gaps and oversights in renewable energy policy in Nunavut. Combined, the results of this thesis were used to develop a number of recommended policy actions that could be undertaken by the territorial and federal government to support a shift towards renewable energy in order to develop a sustainable and self-sufficient energy plan in Nunavut. They include: gathering accurate renewable resource data in Nunavut; increasing community consultations on the subject of renewable energy; building strong partnerships with universities, colleges and industry; developing a knowledge sharing network; and finally increasing accessibility to renewable energy programs and policies in Nunavut. / Thesis (Master, Environmental Studies) -- Queen's University, 2011-09-29 23:47:11.775

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Large percentages of the South African population have no access to grid power and are located at distances that make provision for such facility uneconomical. Also traditional fuels are under pressure. Most areas in South Africa receive 300 days of sunshine per year. The proposed solar system addresses the needs of such communities. A solar thermal energy storage system utilizing phase change material has been proposed that can overcome the time mismatch between solar availability and demand. The system consists of two types of thermal heat storage. The latent heat storage used Phase Change Materials (PCM) which melts at a sufficiently high temperature for cooking a variety of food types. By choosing a suitable PCM to take advantage of the latent heat absorbed during phase changes. Heat losses from both the latent heat storage and condenser are captured in the surrounding sensible heat store. The objective of this project to develop a prototype modules which together as a system could provide the essential domestic power requirements of the target groups. This includes power for cooking, hot water and in addition a limited electrical power supply for the system itself as well as for other minor loads. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.