In urban areas with limited space, deep borehole heat exchangers (DBHE) are coupled with ground source heat pump systems (GSHPS) to extract geothermal energy for building heating purposes. They can exploit more heat than common shallow systems. In this thesis, the open source software OpenGeoSys (OGS) has been utilized to analyse the long-term behavior and temperature evolution in and around single and multiple DBHEs. Moreover, an analysis to reduce the computation time has been applied. This way, the simulation time could be shortened by almost 75% by adjusting the tolerance of the non-linear solver and using an automatic time stepping in a first step. With larger element sizes, which still provide a sufficient result precision, the required duration could be shortened to less than 2% compared to the first method. Especially between the top and the bottom a layer size of 100 m is sufficient. The thickness around the top and bottom, however, should be small to avoid numerical inaccuracies. In the first years of operation most of the energy is extracted by the lower parts of the DBHE. Throughout the years, the contribution along the depth becomes more homogeneous and more soil is influenced. In summer, the top approximately 900 m are not contributing to the heat extraction but instead losing heat to the soil because of a low energy demand, which leads to high inflow temperatures. Considering the results of the in- and outflow temperature evolution, a single DBHE should be preferred over multiple systems. Nonetheless, those can multiply the extractable heat in a certain area and could be more economical.:List of Figures . . . v List of Tables . . . vii 1 Introduction . . . 1 2 Theoretical Background . . . 4 2.1 BHE equations . . . 5 2.2 Thermal Resistance . . . 6 2.3 Exchange Area . . . 10 2.4 Coefficient of Performance . . . 10 2.5 OpenGeoSys Pipe Network Feature . . . 12 3 Modeling Scenarios . . . 14 3.1 Model Setups . . . 15 3.2 Model Verification . . . 16 3.3 Model Environment . . . 20 3.4 Initial and Boundary Conditions . . . 22 3.5 Investigation on Computation Time Influences . . . 24 4 Results and Discussion . . . 30 4.1 In- and Outflow Temperature Evolution . . . 30 4.2 Energy Distribution . . . 34 4.3 Soil Heat Flux . . . 40 4.3.1 Winter in 2nd year . . . 41 4.3.2 Summer in 2nd year . . . 44 4.3.3 Winter in 30th year . . . 47 4.3.4 Summer in 30th year . . . 49 4.4 DBHE Heat Flux . . . 51 4.5 Soil Heat Flux in the Multiple DBHE Case . . . 55 4.5.1 Line Setup . . . 56 4.5.2 Square Setup . . . 61 4.6 Numerical Inaccuracies . . . 65 5 Conclusion . . . 68

Gotland is a pilot area for Sweden to achieve carbon neutrality, which means that achieve a 100% sustainable energy supply is significant for Gotland energy development. Gotland has good sunshine conditions and solar radiation, but the development of solar energy is relatively slow. In order to prove that Visby, the largest city in Gotland, has good solar energy potential, this paper aims to investigate the PV potential for non-residential buildings in Visby by modelling the installation of roof solar panels on representative non- residential buildings (Visby Galleria, surrounding buildings in Stenhuggarvägen) through quantitative research methods. From the final result of the modelling, the solar energy potential per square meter of Visby's non-residential buildings is 121kWh, and the total solar electricity generation potential is 708 GWh. The research results show that Visby's non-residential buildings have high solar power potential, and it can be used as one of the methods to achieve a 100% sustainable energy supply.

This report is a theoretical analysis of high inertia flywheels. Four different flywheel shapes are studied and essential parameters for designing flywheels with optimal energy storage capabilities are discussed. This was done by compiling theoretical findings and presenting these in a way relevant for energy storage applications. Aligning the systems principal axis parallel to the earth’s axis of rotation creates even loads upon the bearings, maximizing lifespan. A flywheel with large outer radius and a thin rim allows for maximum energy storage.

Sustainability has become an emphasised universal topic in recent years, especially just after the turn of the second millennium. Leaders from a wide range of disciplines and geographic locations have congregated to discuss their very real energy concerns and the potential solutions available to address them. Various notable conferences have been held from the World Summit on Sustainable Development in Johannesburg, South Africa in August 2002 to the more recent annual World Future Energy Summit held in Abu Dhabi, United Arab Emirates in January 2013. South Africa and Brazil form part of the BRICS group of nations which is characterised by emerging and rapidly-growing economies. South Africa and Brazil both are favoured by sustainable energy environments with an abundance of sustainable energy resources. Both countries also have various tax incentives that are aimed at encouraging the production and use of sustainable energy. Despite these facts, a large disparity still exists between South Africa and Brazil pertaining to their sustainable energy usage as a percentage of their total primary energy usage. South Africa’s sustainable energy usage is extremely small compared to that of Brazil, and therefore this study aims to determine improvements for South Africa. Brazil’s tax related policies and legislation are instructive in this regard. The benefits of sustainable energy as opposed to energy generated from fossil fuels are evident from an analysis of their economic, environmental and social impacts. Tax incentives can take on various forms and although not the only factor, they would appear to be an important consideration in encouraging investments in sustainable energy. Numerous barriers are identified that directly affect both the ability and desirability of the production and use of sustainable energy. Some of the more significant barriers include high initial capital costs, regulatory frameworks and intellectual rights, the long term nature and payback period of sustainable energy projects and the availability of alternative fossil fuels. Tax incentives are one of the measures that, if appropriately used, could significantly reduce many sustainable energy related barriers. The study concludes that South Africa can learn from Brazil and implement improvements to its tax incentives and related policies and legislation. This would assist in addressing some of its key sustainable energy related barriers. Possible improvements noted include regulatory policies in which South Africa could consider implementing a sustainable energy obligation and mandate; improved certainty regarding South Africa’s research and development incentives; and improved benefits resulting from the research and development incentives. / Dissertation (MCom)--University of Pretoria, 2013. / am2014 / Taxation / unrestricted

The perception of climate change as an emergency has provided the primary impetus to a transition from conventional fossil-based energy sources to renewables. The use of renewable energy sources is essential to sustainable development, since it is the only way that quality of life can remain high while greenhouse gas emissions are cut. Still, at the time of writing, renewables contribute a small part of the total primary energy use worldwide. Much research has gone into understanding barriers to the full-scale adoption of renewable energy sources. Still, many of the tools used have focused primarily on optimal paths, which are useful in the long-term but problematic in non-equilibrium markets. In the shorter term, behavior is thought to be more governed by existing institutions and commitments until those frameworks can be changed. This means that understanding people's attitudes towards renewables is key towards understanding how adoption will take place and how best to incentivize such action. Particularly, decisions are made by investors, who serve as intermediaries between what customers/public want and the existing institutions (what is possible). Understanding their responses to the current state of affairs as well as perturbations in the form of policy changes is important in order to effect change or make sure that policies will work as intended. <br> <br> First, the shifting demand landscape is considered, specifically in Indiana cities. Heating is shrinking as a driver of primary energy use over time due to climate change, while transport increases relatively. Electricity demand continues to increase, and the potential for electrification of transport can add to this potential. This led to a focus on the electricity sector for further work. Noticing that adoption lags public support led to a comparison of levelized cost of electricity and net present value metrics for 18 dominant technologies in two power markets in the US. Capacity markets and solar renewable energy credits lead to differences between cost and net present value in PJM, making natural gas the most attractive technology there. Noting the difference in electricity price between the two markets also provides a caution regarding the employment of carbon pricing in PJM, since that is an additional cost to the consumer who is already paying twice to fossil based generation in that region, once for energy provision and once for reliability. <br> <br> Individual technologies represent only part of the question, however, since generation capacity is added to bolster existing supplies. In order to study the portfolio, historical risk is considered along with levelized costs to identify optimal portfolios in CAISO and PJM. Then electricity is treated as a social good, and a sustainability profile was built for each technology balancing current equity and risks to future generations. This allowed quantification and identification of barriers to market acceptance of renewables, but it also led to a recognition of where useful metrics are still lacking. For example the use of land provides an important barrier to the adoption of renewables, and is a potent potential barrier for future acceptance. It is not well understood, however, which led to a critical review of existing technologies. <br> <br> The work in this dissertation provides one of the first mixed methods attempts to assess energy demand for cities including the end use of cooling. It provides a simple model that demonstrates the importance of capacity markets in determining the profitability of different energy technologies. It provides a guide to the emerging issue of land use by energy systems, a key consideration for the study of the food-energy-water nexus. It is the first use of portfolio optimization for sustainability studies. This is an important methodological tool since it allows a comprehensive sustainability analysis while providing a sense of the difference between immediate and future risks. The tool also allows users to diagnose which technologies are incentivized and which are deterred by market factors, as well as the strength of the deterrence. This is helpful for policy makers in understanding how incentives should be structured.

The Swedish mining and minerals sector is one of the most prominent greenhouse gas emitters in the country. At the same time, it also provides Sweden and other nations with vast amounts of important metals and minerals, which are not easily replaced. However, in light of the increasing urgency to reduce global greenhouse gas concentrations, it is imperative that the combustion of fossil fuels is decreased. This quantitative case study uses a document review and interviews to investigate the prerequisites and technical potential for decarbonising the Dannemora iron ore mine in eastern Sweden. Furthermore, a comparative life cycle inventory based on methods from the Greenhouse Gas Protocol is performed in order to calculate potential savings of both energy and greenhouse gases from exchanging conventional underground mining equipment with more sustainable alternatives. Results show that emissions from underground activities in the Dannemora mine could potentially be reduced by up to 90 %, and energy consumption by up to 64 %. It was however also shown that no viable emission-free explosives currently exist that could safely replace conventional alternatives. Further research needs to be conducted in order to investigate the effects of Scope 3 emissions from the production of battery electric mining vehicles, as this would have an effect on overall GHG and energy savings.

Energy is essential for economic development in Africa. The current electrification figures show that countries in sub-Saharan Africa are facing major challenges in reaching positive economic growth and supplying basic energy services to rural communities. Sustainable energy technologies are available and can be used to great effect in Africa to alleviate this problem. Sustainable energy technologies can contribute to job creation and economic development. The implementation of renewable energy technologies in sub-Saharan Africa to date however has not always been successful due to both technical and non-technical factors. Prior to this study a comprehensive framework of factors to select renewable energy technologies did not exist. The purpose of this research was to develop such a framework and to validate it by means of empirical research. Triangulation of methodologies was used to determine the framework of factors. The analysis of the literature investigated renewable energy technologies and their application, the challenges in renewable energy technologies for implementation in Africa and the selection methods in the fields of project, portfolio, programme and technology management. This was followed by a focus group with three experts in which thirty eight factors that need to be taken into account during the selection of renewable energy technologies in Africa were identified. The factors identified by the focus group were confirmed and the eleven most applicable factors were selected during a two-round Delphi study. Finally case studies on the implementation of renewable energy technologies were undertaken in three countries. These case studies confirmed the eleven factors identified during the Delphi study and identified a further two factors which needed to be added to the framework. The final framework proposed in this study consists of thirteen factors that need to be considered before deciding on the technology appropriate for a specific implementation. For the implementation of the technology to succeed, it must be ensured that the technology can be maintained and supported on site over the life cycle of the technology, and that sufficient skills and resources exist to implement and maintain the technology. Sites for implementation of the technology must be selected in places where local champions exist to continue supporting the technology after the implementing agency has left, the community has the will to adopt the technology in the long term, sites are available for implementing pilot sites and sufficient sites with the correct characteristics are available for long term implementation. The technology must also contribute to economic development by creating jobs or improving the economic situation of households, and financing must be made available to ensure large scale adoption. Local businesses which aid with implementation need to have business management and technical skills as well as the financial capacity to implement the technology. Government support of the implementation of the technology is essential and the environmental benefits of the technology must be clear from the outset. This report presents a framework that includes both the criteria and measures to be used for the selection of renewable energy technologies in Africa. Further work is required to implement these criteria and measures in a selection methodology. / Thesis (PhD)--University of Pretoria, 2011. / Graduate School of Technology Management (GSTM) / unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第19087号 / エネ博第311号 / 新制||エネ||64(附属図書館) / 32038 / 京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻 / (主査)教授 手塚 哲央, 教授 宇根﨑 博信, 准教授 MCLELLAN Benjamin / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

この論文では従来電力系統から自立的に利用出来る太陽エネルギー及び燃料電池コジェネレーションシステムの徹底的な解析が述べられている。開発した水素マイクログリッドの燃料依存を最小化にする数理モデルを利用し日本社会でのさまざまなシナリオのシミュレーションが行なわれた。こういうシステムの実現性が従来水素燃料供給方法の審査及び日本の中型離島の事例研究で評価された。経済的な分析によって石油の価格が高い遠隔な地域では水素マイクログリッドは競争力があると分かった。 / This thesis presents a thorough analysis on energy supply systems using solar energy and fuel cell cogeneration systems that can operate reliably and independently from the main power grid. A mathematical model to maximize fuel independence for hydrogen micro-grids is developed and simulated for various scenarios in Japanese communities. The viability of implementing such systems is assessed with a review of available hydrogen supply channels, and a study case for a remote Japanese island of medium size. An economic analysis of this study suggests that hydrogen micro-grids are economically competitive for energy supply in remote areas where oil prices are high. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

<p>Wireless LAN (WLAN) mesh networks are now being used to deploy Wi-Fi coverage in a wide variety of outdoor applications. In these types of networks, conventional WLAN mesh nodes must be operated using continuous electrical power connections. This requirement may often be very expensive, especially when the network includes expansive outdoor wireless coverage areas. An alternative is to operate some of the WLAN mesh nodes using an energy sustainable source such as solar or wind power. This eliminates the need for a fixed power connection, making the node truly tether-less and allowing for more flexibility in node positioning. The cost of the battery and the solar panel or wind turbine can be a significant fraction of the total node cost, therefore the resource allocation must be performed optimally.</p><p>In this thesis we investigate this problem. First, we present geographic provisioning results for solar and wind powered WLAN mesh nodes. The results suggest that in certain geographic locations a hybrid wind/solar powered WLAN mesh node is the optimum minimum cost configuration. The results also provide strong motivation for introducing power saving to the IEEE 802.11 standard. We then consider the problem of cost-optimal node placement in a hybrid network containing traditional and energy sustainable nodes. Our results show that there is a significant improvement in cost that can be obtained using the proposed methodology. Finally, we consider the problem of energy management in these networks. A control algorithm is proposed that uses access to publicly available meteorological databases. We show that the proposed algorithm minimizes node outage and performs favorably compared to the analytic performance bounds. Overall, the work in this thesis develops analytical and simulation models which investigate the key aspects pertaining to resource allocation in energy sustainable WLAN mesh networks.</p> / Thesis / Doctor of Philosophy (PhD)