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[en] The necessity of long term R and D programmes for gradual utilization of the new renewable energy resources in the brazilian energy power generation is analysed. An analysis about the energy influence in the development of the society in the world since their beginning is made considering further, the energy conservation and energy alternatives technological programmes that has been developed since the petroleum crises. From this point of view, is made an analysis about the brazilian conjuncture energetic evolution, taking into consideration the development programme adopted in the country, the actions in the traditional energy field and their consequence in the energy conservation and energy alternatives technological programmes. In this aspect is made an analysis about the technological brazilian experience concerning the energetics utilization of: sugar cane subproducts, vegetable oils, peat and wind energy. Finally, considering principally the environment problems and the necessity of development of the remote and rural areas, is proposed long term R and D programmes to permit the rational utilization of others energy resources available in this country. (author). 64 refs., 10 figs., 62 tabs
[en] Polarimetric Synthetic Aperture Radar Interferometry (Pol-InSAR) is an active radar remote sensing technique based on the coherent combination of both polarimetric and interferometric observables. The Pol-InSAR technique provided a step forward in quantitative forest parameter estimation. In the last decade, airborne SAR experiments evaluated the potential of Pol-InSAR techniques to estimate forest parameters (e.g., the forest height and biomass) with high accuracy over various local forest test sites. This dissertation addresses the actual status, potentials and limitations of Pol-InSAR inversion techniques for 3-D forest parameter estimations on a global scale using lower frequencies such as L- and P-band. The multi-baseline Pol-InSAR inversion technique is applied to optimize the performance with respect to the actual level of the vertical wave number and to mitigate the impact of temporal decorrelation on the Pol-InSAR forest parameter inversion. Temporal decorrelation is a critical issue for successful Pol-InSAR inversion in the case of repeat-pass Pol-InSAR data, as provided by conventional satellites or airborne SAR systems. Despite the limiting impact of temporal decorrelation in Pol-InSAR inversion, it remains a poorly understood factor in forest height inversion. Therefore, the main goal of this dissertation is to provide a quantitative estimation of the temporal decorrelation effects by using multi-baseline Pol-InSAR data. A new approach to quantify the different temporal decorrelation components is proposed and discussed. Temporal decorrelation coefficients are estimated for temporal baselines ranging from 10 minutes to 54 days and are converted to height inversion errors. In addition, the potential of Pol-InSAR forest parameter estimation techniques is addressed and projected onto future spaceborne system configurations and mission scenarios (Tandem-L and BIOMASS satellite missions at L- and P-band). The impact of the system parameters (e.g., bandwidth, NESZ, ambiguities) and the operation scenario (e.g., temporal decorrelation due to a repeat-pass orbit) is evaluated and discussed with respect to the retrieval of the forest parameters. The study is supported and validated by using repeat-pass Pol-InSAR data at L- and P-band acquired by DLR's E-SAR system over Remningstorp (BioSAR 2007, hemi-boreal forest), Krycklan (BioSAR 2008, boreal forest) and Traunstein (TempoSAR 2008 and 2009, temperate forest) test sites. The simulated spaceborne data sets generated during the BioSAR 2007 campaign are used to carry out the performance analysis.
[en] WIND POWER experiences a tremendous development of its installed capacities in Europe. Though, the intermittence of wind generation causes difficulties in the management of power systems. Also, in the context of the deregulation of electricity markets, wind energy is penalized by its intermittent nature. It is recognized today that the forecasting of wind power for horizons up to 2/3-day ahead eases the integration of wind generation. Wind power forecasts are traditionally provided in the form of point predictions, which correspond to the most-likely power production for a given horizon. That sole information is not sufficient for developing optimal management or trading strategies. Therefore, we investigate on possible ways for estimating the uncertainty of wind power forecasts. The characteristics of the prediction uncertainty are described by a thorough study of the performance of some of the state-of-the-art approaches, and by underlining the influence of some variables e.g. level of predicted power on distributions of prediction errors. Then, a generic method for the estimation of prediction intervals is introduced. This statistical method is non-parametric and utilizes fuzzy logic concepts for integrating expertise on the prediction uncertainty characteristics. By estimating several prediction intervals at once, one obtains predictive distributions of wind power output. The proposed method is evaluated in terms of its reliability, sharpness and resolution. In parallel, we explore the potential use of ensemble predictions for skill forecasting. Wind power ensemble forecasts are obtained either by converting meteorological ensembles (from ECMWF and NCEP) to power or by applying a poor man's temporal approach. A proposal for the definition of prediction risk indices is given, reflecting the disagreement between ensemble members over a set of successive look-ahead times. Such prediction risk indices may comprise a more comprehensive signal on the expected level of uncertainty in an operational environment. A probabilistic relation between classes of risk indices and the level of forecast error is shown. In a final part, the trading application is considered for demonstrating the value of uncertainty estimation when predicting wind generation. It is explained how to integrate that uncertainty information in a decision-making process accounting for the sensitivity of end-users to regulation costs. The benefits of having a probabilistic view of wind power forecasting are clearly shown. (author)
[en] The thesis deals with aspects of the competitiveness of bioenergy. The central aim is to develop a number of concepts that enables an extended analysis. The thesis is composed of four studies. In study 1 and 2 the emphasis is put on two institutional frameworks within the forest company, i.e. the framework around the forest fuel operations and the framework around the industrial timber operations. Depending on which of the two institutional frameworks that makes up the basis for the understanding of forest fuel operations, the forest fuel operations will be given different roles and different priorities. Different goals and the process of integrating the forest fuel operations into the forest company will therefore be carried out with different means, different feelings and different resources. Study 3 examines the conceptions that the actors of the energy system uphold. The study presents the concept of logic, which is an institutionalised conception of the competitiveness of bioenergy. Logics can be seen as the dominating conceptions within the energy system and are decisive in determining the factors and parameters that state the competitiveness of different forms of energy. Study 4 argues that the strategical work concerning the competitiveness of bioenergy in the long-run to a great extent is about understanding, shaping and utilising the conceptions that affect the bioenergy system. The study problematises strategies that are used to develop bioenergy by introducing the uncertainty of the future into the analysis. The uncertainty of the future is captured in different scenarios
[en] The problem addressed by this study is that the amount of federal funds allocated in higher education for conducting basic research in space, solar, and nuclear sciences appear to be declining relative to government and industry. To test this hypothesis, data were obtained from the National Science Foundation on the amounts of federal funds provided for research and development from fiscal years 1955 to 1985. The NSF data were organized into tables, presented, and analyzed to help determine what changes had occurred in the amounts of federal funds allocated to higher education, government, and industry for basic research in space, solar, and nuclear sciences for fiscal years 1967 to 1985. The study provided six recommendations to augment declining federal funds for basic research. (1) Expand participation in applied research, (2) Develop and expand consortia arrangements with other academic institutions of higher education. (3) Pursue other funding sources such as alumni, private foundations, industry, and state and local government. (4) Develop and expand joint research with national and industrial laboratories. (5) Expand participation in interdisciplinary and multidisciplinary research to develop technological solutions to local, regional, and national problems. (6) Develop and expand programs of reciprocal internships, and sabbaticals with industrial and national laboratories
[en] The following question is addressed: can nuclear power and wind power (a form of solar energy) systems yield enough energy to replicate themselves out of their own energy and leave a residual of net energy in order to provide society with its needs and wants. Evidence is provided showing that there is a proportionality between the real monetary cost and energy inputs. The life-cycle, economic cost of the energy-transformation entity is the basis for calculating the amount of energy needed, as inputs, to sustain energy transformation. This study is unique as follows: others were based on preliminary cost and performance estimates. This study takes advantage of updated cost and performance data. Second, most prior studies did not include the energy cost of labor, government, and financial services, transmission and distribution, and overhead in arriving at energy inputs. This study includes all economic costs as a basis for calculating energy-input estimates. Both static (single-entity analysis) and dynamic (total systems over time) analyses were done and the procedures are shown in detail. It was found that the net-energy yield will be very small and most likely negative. System costs must be substantially lowered or efficiencies materially improved before these systems can become sources of enough net energy to drive the United States economic system at even the present level of economic output
[en] The research work is dealing with variable speed wind turbines modelling and control design, in order to achieve the objectives of maximizing the extracted energy from the wind, below the rated power area in the one hand and in the other hand regulating the electric power production, above the rated power area, while reducing mechanical transient loads. For this purpose, we have studied various control strategies from linear to nonlinear based. some of the controllers that we have developed, herein appear for the first time in the relevant domain, the remaining others are an adaptation of well know controllers to the adopted wind turbine models. as matter of fact, we have derived two wind turbine models as well as a wind speed estimator. Indeed, the estimator allows obtaining the effective wind speed which cannot be measured, since the wind profile around the rotor is variable in time and space. As results, it has been shown that single input control by means of pitch angle or generator control cannot succeed to simultaneously drive the electric power output regulation and the rotor speed reference tracking. So then, our idea is to combine nonlinear dynamic state feedback torque control and pitch linear based control which turns out to be the best strategy. In addition, the validation of the controllers performance, using a high turbulence wind speed profile, has been performed through wind turbine simulators provided by nrel (national renewable energy laboratory, golden, co), has confirmed the theoretical results and has led to quite satisfactory conclusions in terms of energy capture optimization, power regulation and disturbances strong rejection as well. (author)
[en] A permanent balance between consumption and generation is essential for a stable supply of electricity. In order to ensure this balance, all relevant load data have to be announced for the following day. Consequently, a day-ahead forecast of the wind power generation is required, which also forms the basis for the sale of the wind power at the wholesale market. The main subject of the study is the short-term power supply, which compensates errors in wind power forecasting for balancing the wind power forecast errors at short notice. These forecast errors effects the revenues and the expenses by selling and buying power in the day-ahead, intraday and balance energy market. These price effects resulting from the forecast errors are derived from an empirical analysis. In a scenario for the year 2020 the potential of conventional power plants to supply power at short notice is evaluated from a technical and economic point of view by a time series analysis and a unit commitment simulation.
[en] The study develops an algorithm for valuating static substratum - biofilm systems used in biogas reactors. This valuation method permits coupling the service value of static substratum - biofilm systems as derived from individual quality factors with the costs of the substratum. Beyond this the cost-related value thus obtained is of principle value for comparing different variants. (orig.)
[de]In der vorliegenden Arbeit wird ein Algorithmus zur Bewertung statischer Traegermaterial - Biofilm - Systeme, die in Biogasreaktoren angeordnet sind, entwickelt. Mit Hilfe dieser Bewertungsmethode ist es moeglich, den aus einer Summe von Eigenschaftswertfaktoren bestehenden Gebrauchswert statischer Traegermaterial - Biofilm - Systeme mit den Kosten des Traegermaterials zu kopplen. Der damit erhaltene kostenbezogene Gebrauchswertfaktor kann darueberhinaus auch allgemein fuer Variantenvergleiche genutzt werden. (orig.)
[en] Solar energy is one of the promising resources of renewable energy. It is of particular interest due to the energy shortage and environment pollution problems. Water heating by solar energy for domestic use is one of the most successful and feasible applications of solar energy. The thermosyphon SDHWS and the loop type thermosyphon systems are widely used for domestic hot water system. The loop type thermosyphon is a circulation device for transferring the heat produced at the evaporator area to the condenser area in the loop by a working fluid. The system has the advantage of high heat transfer rate. A phase change of the working fluid occurs at the evaporator section and the vapor is transported to the condenser by the density gradient. The loop type thermosyphon collector can be made of smaller area and has higher efficiency than the present thermosyphon SDHWS. In this study, the operating characteristics of various working fluids being used have been identified. The working fluids employed in the study were ethanol, water and a binary mixture of ethanol and water. The volume of working fluid used in this study were 30%, 40%, 50%, 60% and 70% of evaporator volume. An increased heat was applied with the increased volume of working fluid. It is observed that, in the thermosyphon with low volume of working fluid, such as 30% or 40%, the fluid was dried out. The average efficiency of the loop type thermosyphon was 46% with high solar irradiation and 43% with low irradiation. The flow pattern and mechanism of the heat transfer were identified through this study. Flow patterns of the binary mixture working fluid were also investigated, and the patterns were recorded in the camera. The system parameters were calculated using the thermal performance data. Modelling of the system was carried out using PSTAR method and TRNSYS program