共查询到20条相似文献,搜索用时 31 毫秒
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Feulner G 《Annalen der Physik》2011,523(11):946-950
An analysis of ground-based observations of solar irradiance was recently published in this journal, reporting an apparent increase of solar irradiance on the ground of the order of 1% between solar minima and maxima [1]. Since the corresponding variations in total solar irradiance on top of the atmosphere are accurately determined from satellite observations to be of the order of 0.1% only [2], the one order of magnitude stronger effect in the terrestrial insolation data was interpreted as evidence for cosmic-ray induced aerosol formation in the atmosphere. In my opinion, however, this result does not reflect reality. Using the energy budget of Earth's surface, I show that changes of ground-based insolation with the solar cycle of the order of 1% between solar minima and maxima would result in large surface air temperature variations which are inconsistent with the instrumental record. It would appear that the strong variations of terrestrial irradiance found by [1] are due to the uncorrected effects of volcanic or local aerosols and seasonal variations. Taking these effects into account, I find a variation of terrestrial insolation with solar activity which is of the same order as the one measured from space, bringing the surface energy budget into agreement with the solar signal detected in temperature data. 相似文献
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L. Schnatbaum 《The European physical journal. Special topics》2009,176(1):127-140
The solar thermal power plant technology, the opportunities it presents and the developments in the market are outlined. The
focus is on the technology of parabolic trough power plants, a proven technology for solar power generation on a large scale.
In a parabolic trough power plant, trough-shaped mirrors concentrate the solar irradiation onto a pipe in the focal line of
the collector. The thermal energy thus generated is used for electricity generation in a steam turbine. Parabolic trough plants
can be combined with thermal storage and fossil or biomass fired heat exchangers to generate electricity even when the sun
is not shining. Solar Millennium AG in Erlangen has developed the first power plant of this kind in Europe. After two years
of construction the plant started operation in Southern Spain in 2008. This one and its sister projects are important steps
leading the way for the whole market. The paper also covers the technological challenges, the key components used and the
research and development activities concerning this technology. Solar thermal power plants are ideal for covering peak and
medium loads in power grids. In hybrid operation they can also cover baseload. The Solar Chimney power plant, another striking
technology for the conversion of solar into electric energy, is described briefly. The paper concludes with a look at the
future – the import of solar energy from the deserts of North Africa to central Europe. 相似文献
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Yu. P. Rylov 《Technical Physics》2003,48(11):1480-1485
The cheapening of solar energy reception and concentration is of primary importance for its effective use. Conventional preformed parabolic reflectors are too bulky and heavy for the shape of their surface to be maintained by load-bearing frameworks. The fabrication of elastically deformed thin-film or thin-sheet reflectors is considered in terms of the classical elasticity theory. It is shown that the solar energy concentration ratio achievable in receivers made by this technology is comparable to that in present-day collectors used in solar power plants; however, collectors made by the new technology may be much cheaper. 相似文献
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Solar energy conversion with fluorescent collectors 总被引:1,自引:0,他引:1
A new principle for solar energy conversion is proposed and evaluated theoretically. Collection and concentration of direct
and diffuse radiation is possible by the use of a stack of transparent sheets of material doped with fluorescent dyes. High
efficiency of light collection can be achieved by light guiding and special design of collectors. The optical path length
in a triangular collector is computed.
In combination with solar cells this type of collector offers the advantage of separating the various fractions of light and
converting them with solar cells with different bandgaps. Theoretical conversion efficiency under optimum conditions is 32%
for a system with four semiconductors.
Thermal energy conversion offers several advantages over conventional collectors: High temperature and efficiency even under
weak illumination, separation of heat transport and radiation collection, low thermal mass. Thermal efficiency is computed
to be between 42% and 60%. Very attractive appear hybrid systems for generation of thermal and electric energy. An estimate
of the economics of electricity generation shows that due to the concentration costs can be much lower than possible today.
With the use of only silicon cells the breakeven point of $0.5/W is almost reached.
Practical difficulties to be solved are: Synthesis of dyes with stringent requirements, identification of plastic materials
with high transparency and development of solar cells with higher bandgaps. 相似文献
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对Al2O3-合成油纳米流体在槽式太阳能集热管内的传热特性进行流体动力学数值模拟,重点考察纳米流体导热系数模型的影响。通过与管内Nusselt数半经验模型的预测结果对比,表明使用考虑布朗运动的纳米流体导热系数模型可较好地预测集热管内传热特性。研究表明纳米颗粒与流体基液的相对运动具有促进集热管内传热的作用。最后,定量研究纳米颗粒添加量对提高基础流体平均传热系数的影响,显示纳米流体在太阳能集热器中具有巨大应用潜力。 相似文献
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In this paper the performances of inhomogeneous dielectric slabs as solar light collectors for both illumination and solar energy applications are analysed. 相似文献
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Summary We have analysed distributions of variable density that can be applied on the surface of solar concentrators with curvature
determined by gravity so as to obtain maximum theoretical concentration along a present focal axis. A simple method to obtain
in practice distributions of variable density is proposed and, consequently, an analysis is carried out of improvements in
the factor of concentration and of the energy gathered by the collector in respect of solar concentrators with curvature determined
only by gravity.
A study completed within the Finalized Energy Project of C.N.R. 相似文献
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Preliminary analysis of surface radiation measurements recorded at the Nansen ice sheet (Antarctica)
Summary An experiment on radiation and surface energy balance was conducted during the 9th Italian expedition in Antarctica at the
Nansen ice sheet, a glacier situated close to the Italian base at Terra Nova Bay, to correlate surface balances to the formation
and development of katabatic winds. Measurements were taken by radiometers covering the whole spectra of solar and terrestrial
emissions and by fast sensors of atmospheric wind velocity and humidity for the application of the eddy correlation technique.
A preliminary analysis of the radiotive energy balance during the Antarctic summer in clear-sky conditions is reported and
discussed. The findings show the very low available energy (mean about 1 W/m2), in terms of net radiation, for the physical processes such as sensible- and latent-heat fluxes. Long-wave radiation balance
was applied to estimate the reliability of the Swinbank's parametrization, relative to general conditions of the atmosphere. 相似文献
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随着人类社会的飞速发展,能源紧缺、环境污染问题日益严重。当下,开发新能源、发展新能源技术已成为全球各国首要能源策略。作为一种清洁能源,太阳能蕴藏着巨大能量,太阳能利用和相关技术在世界范围内也引起了广泛关注。基于纳米流体的太阳能直接吸收式集热装置能够耦合光伏与光热技术,有利于提高太阳能综合利用的效率。由于纳米流体辐射理论对于开发新的光伏热实验平台具有重要的作用,而纳米流体辐射特性研究仍处于起步阶段,所以对于纳米流体辐射规律及机理的研究具有重要的意义。首先综述了纳米流体辐射特性的研究现状,并对纳米流体的辐射特性进行了理论研究,进而采用瑞利散射模型和Mie(米氏)模型对纳米流体最重要的辐射特性之一的透射率进行了理论分析;而后运用实验进行对比验证,分析不同理论模型与实验数据间的吻合性。结果表明:Mie模型比瑞利散射模型更加准确,在光伏热实验平台开发利用中具有更好的适用性。该研究旨在利用纳米颗粒改变流体对太阳能的辐射特性,探索一种实际设计时纳米流体辐射特性简易高效的计算准则,并得到影响纳米流体辐射特性的重要因素之一的体积分数的变化规律,从而提高太阳能直接吸收式集热装置的太阳能利用率。纳米流体辐射特性理论的分析与研究,有利于促进纳米技术在太阳能领域的应用,提高太阳能的综合利用效率。 相似文献
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The optical shape of the heater's surface of solar energy concentrating collectors is here examined. Multi reflection effect,
through a macrocavity analysis is introduced. The optical design of the cavity is accomplished and the cavity effect determined.
Thermotechnical analysis of the system, in order to determine the optimal conditions for the heat transfer and for the maximization
of the energy radiative balance, is introduced. 相似文献
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太阳能槽式系统反射镜玻璃厚度对聚光特性的影响 总被引:1,自引:0,他引:1
针对太阳能槽式系统反射镜玻璃厚度对聚光特性的影响进行了理论、模拟和实验研究。研究结果表明,平行光下反射镜玻璃越厚,入射光线距光轴距离越远,ΔX、ΔY越大。对焦距为1200 mm,反射镜玻璃折射率为1.6的槽式系统进行了理论计算,玻璃厚度为1 mm的反射镜,当距光轴距离为200 mm和2000 mm时,ΔX为0.03 mm和1.69 mm,ΔY为0.19 mm和0.31 mm;当距光轴距离仍为2000 mm时,玻璃厚度为5 mm的反射镜,ΔX为8.41 mm,ΔY为1.55 mm。通过TracePro模拟以及实际实验测量,结果与理论计算相符。 相似文献
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In this letter,we present a lattice Boltzmann simulation for complex flow in a solar wall system which includes porous media flow and heat transfer,specifically for solar energy utilization through an unglazed transpired solar air collector(UTC).Besides the lattice Boltzmann equation(LBE) for time evolution of particle distribution function for fluid field,we introduce an analogy,LBE for time evolution of distribution function for temperature.Both temperature fields of fluid(air) and solid(porous media) are modeled.We study the effects of fan velocity,solar radiation intensity,porosity,etc.on the thermal performance of the UTC.In general,our simulation results are in good agreement with what in literature.With the current system setting,both fan velocity and solar radiation intensity have significant effect on the thermal performance of the UTC.However,it is shown that the porosity has negligible effect on the heat collector indicating the current system setting might not be realistic.Further examinations of thermal performance in different UTC systems are ongoing.The results are expected to present in near future. 相似文献