Electromagnetic energy harvester for harvesting acoustic energy

This paper reports a suspended coil, electromagnetic acoustic energy harvester (AEH) for extracting acoustical energy. The developed AEH comprises Helmholtz resonator (HR), a wound coil bonded to a flexible membrane and a permanent magnet placed in a magnet holder. The harvester’s performance is analyzed under different sound pressure levels (SPLs) both in laboratory and in real environment. In laboratory, when connected to 50 Ω load resistance and subjected to an SPL of 100 dB, the AEH generated a peak load voltage of 198.7 mV at the resonant frequency of 319 Hz. When working under the optimum load resistance, the AEH generated an optimum load power of 789.65 µW. In real environment, the developed AEH produced a maximum voltage of 25 mV when exposed to the acoustic noise of a motorcycle and generated an optimum voltage of 60 mV when it is placed in the surroundings of a domestic electrical generator.     

可再生能源应用在绿色建筑评价中的作用

可再生能源的建筑应用是降低建筑物对化石能源消耗的重要手段,也是绿色建筑评价中的“节能与能源利用”板块的重要组成部分.可再生能源为建筑减少对化石能源的消耗如何量化,在绿色建筑的评定中能够带来多少收益,一直以来是业内关注的问题.本文从中外建筑节能标准中对可再生能源应用的能耗折减方法出发,结合我国绿色建筑评价体系中可再生能源应用的得分点,探讨可再生能源应用在绿色建筑评价中的作用.     

Marine energy

Marine energy is renewable and carbon free and has the potential to make a significant contribution to energy supplies in the future. In the UK, tidal power barrages and wave energy could make the largest contribution, and tidal stream energy could make a smaller but still a useful contribution. This paper provides an overview of the current status and prospects for electrical generation from marine energy. It concludes that a realistic potential contribution to UK electricity supplies is approximately 80 TWh per year but that many years of development and investment will be required if this potential is to be realized.     

Hydrogen energy

The problem of anthropogenically driven climate change and its inextricable link to our global society's present and future energy needs are arguably the greatest challenge facing our planet. Hydrogen is now widely regarded as one key element of a potential energy solution for the twenty-first century, capable of assisting in issues of environmental emissions, sustainability and energy security. Hydrogen has the potential to provide for energy in transportation, distributed heat and power generation and energy storage systems with little or no impact on the environment, both locally and globally. However, any transition from a carbon-based (fossil fuel) energy system to a hydrogen-based economy involves significant scientific, technological and socio-economic barriers. This brief report aims to outline the basis of the growing worldwide interest in hydrogen energy and examines some of the important issues relating to the future development of hydrogen as an energy vector.     

Wind energy

From its rebirth in the early 1980s, the rate of development of wind energy has been dramatic. Today, other than hydropower, it is the most important of the renewable sources of power. The UK Government and the EU Commission have adopted targets for renewable energy generation of 10 and 12% of consumption, respectively. Much of this, by necessity, must be met by wind energy. The US Department of Energy has set a goal of 6% of electricity supply from wind energy by 2020. For this potential to be fully realized, several aspects, related to public acceptance, and technical issues, related to the expected increase in penetration on the electricity network and the current drive towards larger wind turbines, need to be resolved. Nevertheless, these challenges will be met and wind energy will, very likely, become increasingly important over the next two decades. An overview of the technology is presented.     

Contribution of bending energy losses to the apparent tear energy

When a strip is torn, energy is expended both in tearing it and in propagating a bend along each torn section. Estimates are given of the contribution of bending energy losses to the apparent tear energy. Experiments with highly-dissipative semi-crystalline polymers, torn with controlled amounts of bending, are then described. The bending energy losses ranged from 5 to 70 percent of the total tear energy, depending upon the degree of bending imposed, the thickness of the strip, and the extent to which it had been partly cut through before tearing. These results were in satisfactory agreement with approximate theoretical estimates. When the torn strips were allowed to take up naturally bent configurations under the action of the tearing force, then the contribution of bending energy losses to the apparent tear energy became rather independent of the strip dimensions and depended principally upon the dissipative nature of the material, represented by the fraction H of deformation energy that is not recovered. A general relationship is proposed between the apparent (G _c) and true (G _c) tear energies in this case: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaGqaciaa-Deada% qhaaWcbaGaa83yaaqaaiaa-DcaaaGccqGH9aqpcaWFhbWaaSbaaSqa% aiaa-ngaaeqaaOGaai4laiaacIcacaaIXaGaeyOeI0Iaa8hsaGqaai% aa+Lcaaaa!415E!\[G_c^' = G_c /(1 - H)\]. Values of H for the materials examined ranged from 30 to 70 percent. Thus, bending energy losses are expected to increase the tear energy by a factor of 1.4 × to 3.3 × for unconstrained tearing of these semi-crystalline polymers. Somewhat smaller increases were actually observed, ranging from 1.1× to 2×.

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Résumé Lorsque l'on déchire une bande, l'énergie est dépensée à la fois dans le déchirement et dans la propagation d'une flexion sur chacun des bords de la déchirure.On donne des estimations de la contribution des pertes d'énergie associées à ces flexions, à l'énergie apparente de déchirement. On décrit ensuite des expériences de déchirement de bandes en polymères semi-cristallins à haute dissipation, sous des conditions de flexion contrôlées. On a établi que la dissipation d'énergie associées à la flexion vaut de 5 à 70% de l'énergie totale de déchirement, selon le degré de flexion imposé, l'épaisseur de la bande, et la longueur de la coupe réalisée avant déchirure. Ces résultats ont été trouvés en accord satisfaisant avec les estimations théoriques. Lorsque les portions déchirées adoptent la configuration de flexion qui correspond à une situation naturelle sous l'effet des forces de déchirement, les pertes dues à l'énergie de flexion contribuent à l'énergie apparente de déchirement de manière relativement indépendante des dimensions de la bande, mais principalement dépendante de la nature dissipatoire du matériau, représentée par la fraction H de l'énergie de déformation non récupérée.Une relation générale est proposée dans ce cas entre l'énergie apparente (G _c) et réelle (G _c) de déchirement: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaGqaciaa-Deada% qhaaWcbaGaa83yaaqaaiaa-DcaaaGccqGH9aqpcaWFhbWaaSbaaSqa% aiaa-ngaaeqaaOGaai4laiaacIcacaaIXaGaeyOeI0Iaa8hsaGqaai% aa+Lcaaaa!415E!\[G_c^' = G_c /(1 - H)\]Les valeurs de H varieront de 0,3 à 0,7 selon les matériaux examinés. Dès lors, on s'attend à ce que les pertes par énergie de flexion accroissent l'énergie de déchirement d'un facteur 4,4× à 3,3× dans le cas d'un déchirement sans rétreint des polymères semi-cristallins étudiés.Dans la réalité, on a observé des accroissements un peu plus faibles, variant de 1,1× à 2×.

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Department of Aerospace Engineering and Mechanics, University of Minnesota     

Magnetostatic energy calculations

Magnetostatic self-energy can in principle be calculated by evaluating a certain sixfold integral, though this is not practical even for very simple cases. It is pointed out that some analytic transformation of this integral can facilitate computations, especially with an appropriate choice of Ritz models. A review of these is followed by a review of some of the methods that have been used for numerical evaluation of this energy term, in particular Brown's method of approaching the value by calculating rigorous upper and lower bounds.<>     

Biological solar energy

Through the process of photosynthesis, the energy of sunlight has been harnessed, not only to create the biomass on our planet today, but also the fossil fuels. The overall efficiency of biomass formation, however, is low and despite being a valuable source of energy, it cannot replace fossil fuels on a global scale and provide the huge amount of power needed to sustain the technological aspirations of the world population now and in the future. However, at the heart of the photosynthetic process is the highly efficient chemical reaction of water splitting, leading to the production of hydrogen equivalents and molecular oxygen. This reaction takes place in an enzyme known as photosystem II, and the recent determination of its structure has given strong hints of how nature uses solar energy to generate hydrogen and oxygen from water. This new information provides a blue print for scientists to seriously consider constructing catalysts that mimic the natural system and thus stimulate new technologies to address the energy/CO2 problem that humankind must solve. After all, there is no shortage of water for this non-polluting reaction and the energy content of sunlight falling on our planet well exceeds our needs.     

Green energy?

The UK gets nearly all its energy from the fossil fuels (coal, oil, gas etc.) and nuclear power, approximately 15% being consumed in the form of electricity. It is now well known that the burning of fossil fuels is accompanied by atmospheric pollution in the form of acid rain, ozone depletion and the greenhouse effect. Renewable energy sources, e.g. wind, solar, tidal, wave, hydroelectric and geothermal power do not at present contribute significantly to the UK energy supply and are also accompanied by adverse effects on the environment. The best hope for meeting future energy needs may lie in containing energy consumption, increased generation efficiency and an expanded nuclear power programme. The author discusses the problems of acid rain and the greenhouse effect and describes several forms of renewable energy: wind energy, solar energy, tidal power, wave power, hydroelectricity, biomass geothermal power and nuclear power     

Electric energy generator

This study reports an extremely cost-effective mechanism for converting wind energy into electric energy using piezoelectric bimorph actuators at small scale. The total dimensions of the electric energy generator are 5.08 x 11.6 x 7.7 cm3. The rectangular, box-shaped body of the overall structure is made using 3.2-mm thick plastic. Slits are made on two opposite faces of the box so that two columns and six rows of bimorph actuators can be inserted. Each row of bimorph actuators is separated from each other by a gap of 6 mm, and the two columns of bimorphs are separated from each other by a gap of 6.35 mm. In between the two columns, a cylindrical rod is inserted consisting of six rectangular hooks. The hooks are positioned in such a way that each of them just touches the two bimorphs on either side in a particular row. As the wind flows across the generator, it creates a rotary motion on the attached fan that is converted into vertical motion of the cylindrical rod using the cam-shaft mechanism. This vertical motion of the cylindrical rod creates oscillating stress on the bimorphs due to attached hooks. The bimorphs produce output voltage proportional to the applied oscillating stress through piezoelectric effect. The prototype fabricated in this study was found to generate 1.2 mW power at a wind speed of 12 mph across the load of 1.7 komega.     

Efficiency of pulse high-current generator energy transfer into plasma liner energy

The efficiency of capacitor-bank energy transfer from a high-current pulse generator into kinetic energy of a plasma liner has been analyzed. The analysis was performed using a model including the circuit equations and equations of the cylindrical shell motion. High efficiency of the energy transfer into kinetic energy of the liner is shown to be achieved only by a low-inductance generator. We considered an “ideal” liner load in which the load current is close to zero in the final of the shell compression. This load provides a high (up to 80%) efficiency of energy transfer and higher stability when compressing the liner.