Results 21 - 30 of 24251
Results 21 - 30 of 24251. Search took: 0.035 seconds
|Sort by: date | relevance|
[en] To enlighten the debate on future energy policy, UFE has carried out a study of three generation scenarios, looking ahead to 2030: a '70% nuclear' generation scenario (under which the lifetime of the existing nuclear fleet is extended from 40 to 60 years and renewables are developed in line with the Grenelle plan); a '50% nuclear' generation scenario (under which the share of nuclear technology in the energy mix is reduced to 50%); and finally a '20% nuclear generation' scenario (under which all existing nuclear facilities are shut down upon reaching the end of a 40 year working lifetime). A cross-analysis was carried out between these generation scenarios and a range of scenarios for possible future developments in electricity consumption, incorporating various hypothetical projections for demand side management. The results of the study provide a clearer picture of the possible 'policy' choices, based on climate, social, economic and financial criteria, each of which requires weighting against the others in a consistent manner. The following key points raised by the study summarize the main considerations that future governments will need to take into account
[en] Large electricity systems require flexibility to both balance consumption and production, and to manage flows on the grid. Renewable energies increase the need for flexibility in both areas. New technologies such as batteries can address those needs, often in competition with other solutions and at times enjoying a particular advantage due to their speed and ease of location. This article provides an overview of flexibility in the electricity system, and an in-depth analysis of the flexibility required for forecast balancing. (authors)
[en] Photovoltaic effect or phenomenon is the creation of a voltage and corresponding current in a material upon exposure to light energy following the principle that for every excitation there must be a response. The exposition of a solar cell to incident optical radiation excites the dislodgement of electrons hence the creation of holes and subsequent migration of opposite charges. The amount of voltage that can be generated is a function of the intensity of incident optical radiation and the position of the solar cell to such radiation. Measurements of illumination intensity from halogen and tungsten lamps by a digital lux meter and open circuit voltage, short circuit current as output parameters by volt- amp meter LCD display embedded in the solar power device was carried out. The evaluation of fill factor, maximum power and conversion efficiency as other output parameters in relation to illumination from the sources of light at varying angle and distance were carried out in this study also. The variation of the internal resistance of the cell with light intensity was also investigated. The maximum output voltage and current were realized at angle zero degree when the light ray falls at normal to the cell surface. The two 10 Watts halogen lamp gave the highest illumination intensity of 116lx while the 40 Watt and 60 Watt tungsten lamp placed at 10 cm from the solar cell indicated an intensity of 70lx and 25lx each. The results showed the strongly direct dependency of these parameters on illumination intensity and their inverse dependence on the tilt angle and distance of the illumination source. The internal resistance decreases with increasing intensity while the evaluated fill factor, maximum power and efficiency remain fairly constant but at an average value 0.53, 122mW and 55% respectively. (author)
[en] Energy is only a utility, it should not lead to feelings or dreams; it is only a question of choosing the most efficient means of heating, cooking, moving, machining, etc., while preserving a pleasant environment. Whether by one means or another, this in itself is of no importance to the citizen. However, if we look at statements and positions, this rationality is often absent; orders of magnitude, availability in space and time, are often forgotten. We move from the pilot experiment to the upheaval of society, forgetting the stages that can be dead ends. We confuse objectives and means by getting enthusiastic about attractive but unrealistic ideas
[fr]L'energie n'est qu'une utilite, elle ne devrait entrainer ni sentiment ni reve; il s'agit seulement de choisir les moyens les plus efficaces pour se chauffer, cuisiner, se deplacer, usiner, etc., tout en preservant un environnement agreable. Que ce soit par une voie ou par une autre, cela n'a pas d'importance en soi pour le citoyen. Pourtant, si l'on regarde les declarations et prises de position, cette rationalite est souvent absente; les ordres de grandeur, les disponibilites dans l'espace et dans le temps, sont souvent oublies. On passe de l'experience pilote au bouleversement de la societe en oubliant les etapes qui peuvent etre des impasses. On confond objectifs et moyens en s'enthousiasmant sur des idees seduisantes mais irrealistes
[en] The influence of real operating conditions of the solar modules (solar radiation intensity, ambient temperature, wind speed) on their output performances is analyzed. An analytical expression is proposed, allowing to approximate the temperature of the solar modules. An algorithm for assessing the operating power of solar modules based on their data sheet information has been developed. The MatLab-Simulink simulation has shown that the identification of ambient and solar module temperatures leads to errors of up to 20 percent in estimating the operating power of solar modules
[en] The use of renewable energy sources at global level continues growing at a rapid pace, yet in the frame of a strong decrease of the oil price. Regarding to electric generation, renewable sources represented about 59% of new power installed in 2014, with a market ruled by hydro, wind and photovoltaic solar energies. To the end of 2015, the renewable energy capacity was enough to feed about the 23.7% of the global electric demand, being the main contributions hydro (16.6%), wind (3.7%), bioenergy (2.0%) and photovoltaic (1.2%). In Argentina, even though since 16 years ago there has been various programs to boost their use, the growth of the new renewables, mainly wind and solar, has been very slow. The electricity power mix has a strong dependence on thermal generation based on fossil fuels, whit a relative share over 60% since 2011 to date. At the same time, the share of wind and photovoltaic energies has been very small, representing just the 0.44% of power generation at 2015. Here, an overview at global, regional, and national level of the photovoltaic solar energy development as power generation source is presented. Particularly, the photovoltaic market, the incidence of the photovoltaic technology in the power mix, and aspects concerning to electricity tariff and legal and technical regulations at the local level are analyzed, with special emphasis on distributed generation. (author)
[es]El uso de las fuentes renovables de energía a nivel mundial continúa creciendo a ritmo acelerado, aún en un contexto de fuerte descenso de los precios del petróleo. En lo referente a la generación eléctrica, las fuentes renovables representaron alrededor del 59% de la nueva potencia instalada en 2014, con un mercado dominado por las energías hidroeléctrica, eólica y solar fotovoltaica. A finales del 2015, la capacidad de energía renovable era suficiente para abastecer aproximadamente el 23,7% de la electricidad mundial, siendo sus principales contribuciones la energía hidráulica (16,6%), la eólica (3,7%), la bioenergía (2,0%) y la solar fotovoltaica (1,2%). En la Argentina, si bien hubo diversos programas que incentivaron su uso en los últimos 16 años, el avance de las nuevas energías renovables, principalmente eólica y solar, ha sido sumamente lento. La matriz eléctrica tiene una fuerte dependencia con la generación térmica basada en combustibles fósiles, cuya contribución relativa es superior al 60% desde 2011 a la fecha. Al mismo tiempo, la participación de las energías eólica y fotovoltaica ha sido muy reducida, representando sólo el 0,44% de la generación eléctrica del año 2015. Se presentará un panorama a nivel global, regional y nacional del desarrollo de la energía solar fotovoltaica como fuente de generación eléctrica. En particular, se analizarán el mercado fotovoltaico, la incidencia de la tecnología fotovoltaica en la matriz energética, y aspectos concernientes a la tarifa y al desarrollo de las regulaciones técnicas y legales en el ámbito local, con especial énfasis en la generación distribuida. (author)
[en] Lorentz gauge theory of gravity was recently introduced. We study the homogeneous and isotropic universe of this theory. It is shown that some time after the matter in the universe is diluted enough, at , the decelerating expansion shifts spontaneously to an accelerating one without a dark energy. We discuss that Lorentz gauge theory puts no constraint on the total energy content of the universe at present time and therefore the magnitude of vacuum energy predicted by field theory is not contradictory anymore. It is demonstrated that in this theory the limit on the number of relativistic particles in the universe is much looser than in GR. An inflationary mechanism is discussed as well. We show that the theory, unlike GR, does not require the slow-roll or similar conditions to drive the inflation at the beginning of the universe. (paper)
[en] Highlights: • Relative importance of the determinants of FDI in wind and solar energy are clarified. • Expert opinions are analyzed using analytical hierarchy process. • Renewable policies hold strong influence when compared to traditional determinants. • Renewable policies need to be designed to reduce exchange rate volatility risk. • Creating one-stop agency is recommended for efficient administrative procedure. - Abstract: The importance of foreign direct investment (FDI) for the development of renewable energy in developing countries has been increasingly recognized. Numerous countries have created various measures to attract FDI in the renewable energy sector. This paper uses the analytical hierarch process to clarify the relative significance of the determinants in the location decisions of foreign wind and solar energy investors. A total of 18 determinants that are categorized into the macroeconomic environment, institutional environment, natural conditions, and renewable energy policy categories are used for the analysis. The results show that adding to the traditional determinants of FDI, including the macroeconomic environment, the institutional environment, and natural conditions, renewable energy support policies have the same or stronger influence as location determinants of FDI. The paper also points out that some of the traditional determinants, such as exchange rate volatility, access to land, and an efficient and transparent administrative procedure, are also very important as determinants of FDI in wind and solar energy. Policy implications focus on the determinants of FDI in wind and solar energy. The relative significance of the determinants clarified through this study offers criteria for prioritizing policies and actions for policy makers.
[en] This study aims at improving the potential of penetration of solar energy (natural light and thermal contributions) in buildings in winter, by improving their exposure and by limiting masks created by buildings. Applied to the case of a development site (the Bron Terraillon ZAC), this approach aims at the improvement of the initial urban composition, and at being a source of inspiration for development proposals. The urban composition master plan, initial data, and hypotheses are first presented. After some general guidelines, a solar analysis of the master plan is reported, and a discussion of the use of vegetation is discussed. Then, the potential solar production is assessed (solar resource of the location, photovoltaic solar installation on roof, facade, or greenhouse, thermal solar installation)
[en] Highlights: • A solar-driven Kalina cycle is investigated by advanced exergoeconomic analysis. • The highest exergy efficiencies are related to the separator and turbine with the values. • Rotary machinery have more than 83% avoidable share of exergy destruction rate. - Abstract: A Kalina cycle driven by solar energy resource is evaluated by conventional exergy and exergoeconomic analysis methods. Because conventional exergy analyses isn’t able to give information about costs of the irreversibilities and investment, advanced exergy is investigated. Based on the conventional exergy analyses, the most exergy destruction occurs in a heater with a value of 94.44 kW. Also the highest exergy efficiencies are related to the separator and turbine with the values of 99.67% and 89.81%, respectively. Advanced exergy analyses demonstrates absorber (1.3 $/h) and one of the pumps (0.009 $/h) have the highest and lowest exergy destruction cost rate, respectively. Also the results show turbine (85.88%) and separator (1.105%) have the highest and lowest exergoeconomic factor, respectively. Finally, in order to determine optimum point of the inlet temperatures and pressure ratio of the pumps and turbine (rotary machines), a parametric study is applied at different stages.