Offshore floating wind turbines represent the future of wind energy. However, significant challenges must be overcome before these systems can be widely used. Because of the dynamics of offshore floating wind turbines—surge, sway, heave, roll, pitch, and yaw—and the resulting interactions between the rotor and generated wake, the aerodynamic analysis methods and design codes that have found wide use throughout the wind energy industry may be inadequate. Application of these techniques to offshore floating wind turbine aerodynamics may result in off-optimal designs, effectively handicapping these next-generation systems, thereby minimizing their full potential. This dissertation will demonstrate that the aerodynamics of offshore floating wind turbines are sufficiently different from conventional offshore and onshore wind turbines, warranting the use of higher fidelity analysis approaches. It will outline the development and validation of a free vortex wake code, the Wake Induced Dynamics Simulator, or WInDS, which uses a more physically realistic Lagrangian approach to modeling complex rotor-wake interactions. Finally, results from WInDS simulations of various offshore floating wind turbines under different load conditions will be presented. The simulation results indicate that offshore floating wind turbine aerodynamics are more complex than conventional offshore or onshore wind turbines and require higher fidelity analysis approaches to model adequately. Additionally, platform pitching modes appear to drive the most aerodynamically-significant motions, followed by yawing modes. Momentum balance approaches are shown to be unable to accurately model these dynamic systems, and the associated dynamic inflow methods respond to velocity changes at the rotor incorrectly. Future offshore floating wind turbine designs should strive to either minimize platform motions or be complementarily optimized, via higher fidelity aerodynamic analysis techniques, to account for them. It is believed that this dissertation is the first in-depth study of offshore floating wind turbine aerodynamics and the applicability of various analysis methods.^

Placing smaller cells in a heterogeneous cellular network can be beneficial in terms of energy because better capacities can be obtained for a given energy constraint. These type of deployments not only highlight the need for appropriate metrics to evaluate how well energy is being spent, but also raise important issues that need to be taken into account when analysing the overall use of energy. In this work, handoff strategies, bandwidth allocation, and path loss models in different scenarios, illustrate how energy can be consumed in a more efficient way when cell size is decreased. A handoff strategy based on per-energy capacity is studied in order to give priority to a more energy efficient handoff option. Energy can also be spent more adequately if the transmit power is adjusted as a function of interference. As a result, users can experience higher capacities while spending less energy, depending whether they handoff or not, increasing the overall performance of the network in terms of energy efficiency.

0 / SPK / specialcollections@tulane.edu

Decarbonizing the electricity system (i.e. eliminating generation from fossil fuels and replacing it with non-emitting sources) is widely considered a necessary step to limiting anthropogenic emissions and minimizing the impacts of climate change. Selecting which non-emitting generators should replace existing fossil fuel sources, and when to build them, is critical to the success of this transition. The optimal pathway to decarbonisation is highly region-specific. It is impacted by both factors such as availability of renewable resources, existing generation resources, and government policy. This dissertation presents a techno-economic model that is used to assess the decarbonisation of the combined British Columbia and Alberta electricity system. It is found that high levels of decarbonisation are possible through a combination of new wind generation, particularly in Alberta, and increased trade between Alberta, British Columbia, and the United States. Following on this finding, the variability related to high penetrations of renewable generation is introduced to the model and its impact is assessed. These results indicate that variability will be an important constraint in planning decarbonized energy systems. Finally, the representation of British Columbia’s existing hydroelectric resources is expanded to determine the ability to buffer variable renewable generation with these resources. This study finds that, while existing hydroelectric resources can support much of the variability in a highly renewable energy system, additional technologies and/or policies are needed to reach a fully zero-carbon system. The findings in this thesis show that British Columbia and Alberta, with an expanded interconnection between the provinces, can reach high penetrations of variable renewable energy. The majority of this generation consists of wind energy in Alberta, which is abundant and low-cost compared to other generation options. While comparatively little generation is added in British Columbia, the existing hydroelectric resources in the province provide significant flexibility to support the variability of this wind generation. / Graduate

I januari 2017 kom Boverket ut med nya förslag om regleringar gällande Sveriges realisering av primärenergifaktorer för uppvärmning i byggnader. Det innebär att de tidigare kraven om specifik energianvändning ersätts med en energiprestandaindikator som uttrycker en byggnads primärenergianvändning. Användningen av primärenergifaktorer för reglering av uppvärmning i byggnader härstammar ifrån EU:s direktiv om energieffektiva byggnader (EPBD), där syftet är att styra nybyggnationer mot nära-nollenergibyggnader (NNE). Boverket föreslår att el bör tilldelas primärenergifaktorn 1,6 fram till 2021 och uppvärmning med fjärrvärme, olja, naturgas och biobränsle ska inledningsvis tilldelas faktorn 1,0. Förslaget har fått mycket kritik ifrån bland annat svenska energibolag, som menar att den svenska fjärrvärmen missgynnas, då den likställs med annan uppvärmning som exempelvis olja. Det framgår även i EPBD att medlemsländer får ta fram egna primärenergifaktorer som motsvarar lokala förutsättningar. Sammantaget har examensarbetet syftat till att beräkna och analysera primärenergifaktorer för svensk fjärrvärme. Inom arbetet genomfördes en litteraturstudie där rapporter, vetenskapliga artiklar och konsultrapporter inom ämnet primärenergifaktorer studerades. Dessutom undersöktes huruvida övriga länder inom EU beräknat nationella primärenergifaktorer för fjärrvärme och hur de gått tillväga. Det har konstaterats av författarna att det finns ett stort antal metoder, värderingar och synsätt att beakta vid framtagandet av primärenergifaktorer. Två olika beräkningsperspektiv har identifierats, bokförings- och konsekvensperspektivet. Utöver dessa perspektiv återfanns ett antal metoder för allokering mellan el och värme; I rapporten har energimetoden, alternativproduktionsmetoden samt exergimetoden studerats inom bokföringsperspektivet. För konsekvensperspektivet har systemutvidgning använts genom power bonus method, i vilken producerad el i kraftvärmeverk antas ersätta motsvarande mängd elproduktion på marknaden. Totalt studeras 10 olika kombinationer med varierande perspektiv, allokeringsmetoder och indata för beräkning av primärenergifaktorer. Författarna föreslår att bokföringsperspektivet och alternativproduktionsmetoden bör användas som ett första steg vid framtagandet av svenska primärenergifaktorer för fjärrvärme. Detta eftersom metoden är lätthanterlig och stödjs av flertalet aktörer, såsom Värmemarknadskommittén (VMK) och Swedish Standards Institute (SIS). De beräknade primärenergifaktorerna har delats upp i de 8 kategorierna nät med och utan avfall, med och utan elproduktion efter storlek samt ett nationellt värde. Primärenergifaktorer för ingående bränslen i fjärrvärmeproduktion har inhämtats från VMK och SIS. Författarna har valt att inte förespråka någon uppdelning framför en annan, utan anser snarare att en tydlig motivering bör ligga bakom de beslut som ska tas och att de beräknade faktorerna utgör beslutsunderlag i frågan. En viktig slutsats är dock att de beräknade faktorerna är betydligt mindre än den som presenterats av Boverket. Vidare anser författarna att tydligare riktlinjer behöver implementeras på EU-nivå för hur nationella och lokala primärenergifaktorer får tas fram och beräknas. / In January 2017, Boverket issued new proposals for regulations concerning Sweden's realization of primary energy factors for heating in buildings. The new proposal replaces the previous requirements for specific energy use with an energy performance indicator that expresses a building's primary energy use. The use of primary energy factors for the regulation of heating in buildings is derived from the EU's Energy Efficient Buildings Directive (EPBD), which aims guiding new buildings towards Near-Zero Energy Buildings (NZEB). Boverket proposes that electricity should be set to the primary energy factor 1.6 (until 2021) and heating by either district heating, oil, natural gas or biofuel should initially be assigned the factor 1.0. The proposal has received a lot of criticism from, among other players, Swedish energy companies, which argue that the Swedish district heating is given a disadvantage, as it valued the same as energy carriers such as oil. It is also apparent from the EPBD that member countries may develop their own primary energy factors that correspond to local conditions if they want to. All in all, above mentioned issues have led to this thesis’ aim, which is calculating and analyzing primary energy factors specifically for Swedish district heating. Within the thesis boundaries, a literature study was conducted in which reports, scientific articles and consultancy reports on the subject of primary energy factors were studied. In addition, it was investigated if other EU countries have calculated national primary energy factors for district heating and how they were implemented. It has been concluded by the authors that there are a large number of methods, values and approaches to be taken into account in the development of primary energy factors. Two different calculation perspectives have been identified, the accounting and consequence perspective. In addition to these perspectives, a number of methods were found for the allocation of electricity and heat; In the thesis, the energy method, the alternative production method and the exergy method have been studied in the accounting perspective. For the consequence perspective, system expansion has been utilized through the power bonus method, in which electricity produced in CHP plants is assumed to replace the corresponding electricity generation in the market. In total, 10 different combinations are studied with varying perspectives, allocation methods and input data for the calculation of primary energy factors. The authors suggest that the accounting perspective and alternative production method should be used as a first step in the development of Swedish factors for district heating. The method is easy to handle and supported by many actors, such as Värmemarknadskommittén (VMK) and the Swedish Standards Institute (SIS). The calculated primary energy factors have been divided into the following categories: waste in the fuel mix, a national factor, electricity generation and grid size. The authors have chosen not to advocate any calculated factor in front of another, but rather thinks that the upcoming decisions to be taken regarding primary energy factors should be well motivated. An important conclusion, however, is that the calculated factors are considerably smaller than those presented by Boverket. Furthermore, the authors argue that clearer guidelines need to be implemented at an EU level for how national and local primary energy factors can be developed and calculated.

Many countries are advancing down the road of electricity privatization, deregulation, and competition as a solution to their growing electricity demand and other challenges posed by the monopolistic nature of the existing structure. Presently, Nigeria has a supply deficit of electricity as a result of the growing demand. This imbalance has negatively affected the economy of the country and the social-economic well-being of the population. Hence, there is an urgent need to reform the power sector for greater efficiency and better performance. The objectives of the reform are to meet the growing power demand by increasing the electric power generation and also by increasing competitiveness through the participation of more private sector entities. The renewable energy integration is one way of increasing the electricity generation in the country in order to cater for the growing demand adequately. Examples of the renewable energy that is available in the country include wind, geothermal, solar and hydro. They are considered to be environmentally friendly, replenishable and do not contribute to the climate change phenomena. The country presently generates the bulk of its electricity from both thermal (85%) and hydroelectric (15%) power plants. While electricity generation from the thermal power stations constitutes the largest share of greenhouse emission, this is mostly from burning coal and natural gas. The effect of this high proportion of greenhouse emission causes climate change which is referred to as a variation in the climate system statistical properties over a long period of time. It has been observed that many of the activities of human beings are contributory factors to the release of these greenhouse gases (GHG). But, as the traditional sources of energy continue to threaten the present and future existence on the planet earth, it is, therefore, imperative to increase the integration of the variable renewable energy sources in a sustainable and eco-friendly manner over a long period of time. The variability and the uncertainties of the renewable energy source's output, present a major challenge in the design of an efficient electricity market in a deregulated environment. The system deregulation and the use of renewable sources for the generation of electricity are major changes presently being experienced in power system. In a deregulated power system, the integration of renewable generation and its penetration affects both the physical and the economic operations. The main focus of this research is on the integration of wind energy into Nigerian power systems. Up till now, research on the availability of the wind energy and its economic impacts has been limited in Nigeria. Generally, the previous study of wind energy availability in Nigeria has been limited in scope. The wind energy assessment study has not been detailed enough to be able to ascertain the wind energy potential of the country. To cope with this shortcoming, a detailed statistical wind modeling and forecasting methodology have been used in this thesis to determine the amount of extractable wind energy in six selected locations in Nigeria using historical wind speed data for 30 years. The accuracy test of the statistical models was also carried using the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Chi-Square methods to determine the inherent error margin in the modeling and analysis. It is found that the error margin of the evaluations falls within the expected permissible tolerance range. For a more detailed wind assessment study of the Nigeria weather, the seasonal variation of the weather conditions as it affects the wind speed and availability during the two major seasons of dry and rainy was considered. A Self-Adaptive Differential Evolution (SADE) was used to solve the economic load dispatch problem that considers the valve-point effects and the transmission losses subject to many constraints. The results obtained were compared with those obtained using the "standard" Differential Evolution (DE), Genetic Algorithm (GA), and traditional Gradient Descent method. The results of the SADE obtained when compared with the GA, DE, and Gradient descent show the superiority of SADE over all the other methods. The research work shows that the wind energy is available in commercial quantity for generation of electricity in Nigeria. And, if tapped would help reduce the gap between the demand and supply of electricity in the country. It was also demonstrated that the wind energy integration into the power systems affects the generators total production cost.

No description available.

No description available.

This master’s thesis is a contribution to the cross-disciplinary research project SitCit that addresses the issue of urban sustainable development. It aims to investigate how Information and Communication Technology (ICT) can be used to reduce the energy use and increase the energy demand flexibility in Stockholm’s Södermalm district. This study uses a bottom-up approach to model how ICT can change the energy use. The basis of the approach is the human activities that cause demand for services, delivered by different appliances, which in turn use energy to provide these services. The human activities are represented by Human Activity Systems (HAS) and the different appliances by Energy Usage Systems (EUS). A method for defining an energy system with a bottom-up approach was developed and used to build a conceptual model. Relevant ICT solutions were thereafter identified and described both technically and how they interact with the HAS, the EUS and the surroundings to change the energy use by means of automation, information and persuasion. It was also assessed how and when planning and implementation of ICT can be achieved, and who are the involved actors. The findings were compiled into an integrated qualitative model which was split into two parts, one that illustrates the interrelatedness of the different components expressed in terms of information flows, and one that shows who are the actors involved in the strategies to implement the various ICT solutions. Weaknesses in the bottom-up approach were identified and changes were suggested. The HAS should be split into human activities and what can be denoted “human” since most information flows due to ICT are not with the actual activities. The human can communicate through and with ICT. He or she can decide the activities and how much of them should be carried out, and is also the most important actor when it comes to the implementation of ICT. Furthermore, it was found that the coupling of HAS and EUS is weak, and time-use data and actual measurements on the energy use is therefore needed as input to a quantitative model. This study explains and illustrates how different ICT solutions work and how they can be implemented to change the energy use in an urban area. Together with the improvements in the bottom-up approach, and the methodological discussion, it can be used as groundwork for a quantitative model, or as a tool for decision makers to create and implement a strategy for urban sustainable development.

In this report we discuss the use of k-ε RANS (Reynolds-averaged Navier-Stokes equations) turbulence model for wind turbine applications. This model has been implemented in the new wind turbine wake CFD code that is being developed at ECN. Simulations of the wind turbine test site EWTW are compared with measurements conducted between 2005 and 2009 and with FarmFlow, ECN's current wind turbine wake code. Based on the results the uncertainties in the current approach are highlighted and areas for possible improvement are discussed.