Showing papers on "Solar energy published in 1993"
TL;DR: In this article, the use of pyrite as an ultrathin (10-20 nm) layer sandwiched between large gap p-type and n-type materials in a p-i-n like structure is discussed.
547 citations
Journal Article•
TL;DR: The ideal cylindrical light collector is capable of accepting solar radiation over an average ∼8-hr day and concentrating it by a factor of ∼10 without diurnal tracking of the sun, not possible by conventional imaging techniques.
Abstract: A new principle for collecting and concentrating solar energy, the ideal cylindrical light collector, has been invented. This development has its origins in detecting Cherenkov radiation in high energy physics experiments. In its present form, the collector is a trough-like reflecting wall light channel of a specific shape which concentrates radiant energy by the maximum amount allowed by phase space conservation. The ideal cylindrical light collector is capable of accepting solar radiation over an average ∼8-hr day and concentrating it by a factor of ∼10 without diurnal tracking of the sun. This is not possible by conventional imaging techniques. The ideal collector is non-imaging and possesses an effective relative aperture (f-number) =0·5. This collector has a larger acceptance for diffuse light than concentrating collectors using imaging optics. In fact, the efficiency for collecting and concentrating isotropic radiation, in comparison with a flat plate collector, is just the reciprocal of the concentration factor.
490 citations
TL;DR: In this paper, the authors proposed a semi-empirical method to determine the optimum aperture size and operating temperature of a solar cavity-receiver for which its energy conversion efficiency is maximized.
242 citations
TL;DR: In this paper, a simple parameterization of the solar radiation budget at the surface and in the atmosphere is developed from 5 years of Earth Radiation Budget Experiment data and European Centre for Medium Range Weather Forecasts humidity data.
Abstract: As a result of recent satellite-based observation programs, knowledge of the radiation budget at the top of the atmosphere has improved substantially. In comparison, there has been little improvement in knowledge of the radiation budgets at the surface and in the atmosphere. Based on a simple parameterization, global climatologies of the solar radiation budget at the surface and in the atmosphere are developed from 5 years of Earth Radiation Budget Experiment data and European Centre for Medium Range Weather Forecasts humidity data. Both data sets have global coverage on 2.5° × 2.5° grids. Global distributions of the solar radiation budget at the surface give maximum seasonal values of the net solar radiation for the subtropical oceans of more than 300 W m−2. The maximum seasonal absorption in the atmosphere is about 120 W m −2. Shortwave cloud forcing at the surface and in the atmosphere is also derived. Clouds reduce the seasonally averaged surface net solar radiation by up to 175 W m−2, whereas they increase seasonal net solar radiation in the atmosphere by less than 15 W m−2. The globally and annually averaged net solar radiation budgets in the atmosphere and at surface are 83 and 157 W m−2, respectively. Expressed as percentages of the solar radiation incident at the top of the atmosphere, these values correspond to a globally and annually averaged absorption in the atmosphere and at the surface of 24.3% and 46.0%, respectively, and a planetary albedo of 29.7%.
166 citations
TL;DR: In this paper, the authors examined the major heat loss mechanisms associated with transpired solar collectors and proposed a simple computer model which predicts collector efficiency as a function of suction velocity, wind speed, ambient temperature, and radiation.
Abstract: Unglazed transpired solar collectors offer a potentially low cost, high-efficiency option for once-through applications such as preheating air for ventilation, crop drying, and desiccant regeneration. This paper examines the major heat loss mechanisms associated with this concept. Radiation heat loss is determined by considering losses to both the sky and the ground. Convective heat losses are obtained by integrating the product of the temperature and velocity profiles in the boundary layer at the downwind edge of the collector. This convective heat loss is then expressed in terms of the thermal equivalent length of irradiated absorber, and analysis shows that this loss can be very low for large collectors event under windy conditions. These results are incorporated into a simple computer model which predicts collector efficiency as a function of suction velocity, wind speed, ambient temperature, and radiation. Remaining research issues are discussed.
149 citations
Patent•
05 Nov 1993TL;DR: In this paper, a hybrid combined cycle power plant including a solar central receiver for receiving solar radiation and converting it to thermal energy was proposed, which includes a molten salt heat transfer medium for transferring the thermal energy to an air heater.
Abstract: A hybrid combined cycle power plant including a solar central receiver for receiving solar radiation and converting it to thermal energy. The power plant includes a molten salt heat transfer medium for transferring the thermal energy to an air heater. The air heater uses the thermal energy to preheat the air from the compressor of the gas cycle. The exhaust gases from the gas cycle are directed to a steam turbine for additional energy production.
112 citations
01 Sep 1993
110 citations
TL;DR: The best known methods of estimating the solar irradiance at the earth's surface using geostationary satellite data are reviewed in this article, where the models may be classified into statistical and physical models, depending on the approach used to treat the interaction between solar radiation and atmosphere.
108 citations
TL;DR: In this paper, it was shown that the worst of these problems is photochemical destruction of the fullerenes in the light from the arc, and solar furnaces can mitigate this problem both by avoiding the intense ultraviolet radiation associated with arcs and by preventing clustering of the carbon vapor until it passes into a relatively dark cluster formation and annealing zone.
Abstract: Fullerenes have been produced efficiently by direct vaporization of carbon in focused sunlight. Large-scale solar furnace implementations of this simple process may be uniquely capable of producing fullerenes and doped fullerenes in large amounts while avoiding the yield-limiting problems encountered with carbon arcs or plasmas. Evidence is presented that the worst of these problems is photochemical destruction of the fullerenes in the light from the arc. Solar furnaces can mitigate this problem both by avoiding the intense ultraviolet radiation associated with arcs and by preventing clustering of the carbon vapor until it passes into a relatively dark cluster formation and annealing zone. 21 refs., 4 figs.
101 citations
01 Oct 1993
TL;DR: In this article, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system and the properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation.
Abstract: A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient. A preceding paper outlined the method and provided the physical derivation of the calculation. In this second of a series of related papers the detailed development of the matrix layer calculation is presented.
95 citations
Journal Article•
TL;DR: A general survey of solar radiation measurement, the techniques and instrumentation is presented in this article, where the importance of determining the total and spectral irradiance of the Sun is examined in the context of the energy crisis and utilization of solar energy.
Abstract: A general survey is presented of solar radiation measurement, the techniques and instrumentation. The importance of determining the total and spectral irradiance of the Sun is examined in the context of the energy crisis and utilization of solar energy. The survey includes the extraterrestrial solar fluxes, their possible variations, problems relating to energy received by collecting surfaces on the ground, major types of instrumentation and the radiation scales to which the measurements are referred. The type of insolation data available from the National Weather Service of NOAA and from other sources is reviewed. Alternate techniques of deriving insolation data with high space time resolution are discussed with reference to solar energy conversion requirements. Energy received on the ground can be computed from known values of the extraterrestrial solar spectrum and of the spectral absorption parameters of the atmosphere. Another technique is based on measurements made by meteorological satellites of the cloud-cover and of the solar energy reflected and scattered back to space by the Earth-atmosphere system.
TL;DR: In this paper, the performance of a solar chemical heat pipe was studied using CO2 reforming of methane as the vehicle for storage and transport of solar energy, which was run under variable insolation conditions, including partly cloudy days.
TL;DR: In this article, models for the evaluation of total diffuse and specular reflectance and transmittance components for scattering samples measured on an integrating sphere are presented, and it is demonstrated that for typical solar energy surfaces serious errors can be the result of incorrect interpretation of the detector signals.
TL;DR: In this article, a novel interface circuit between solar cells and a commercial AC source using Van Allen's multivibrator is presented, where the AC source is used as a backup for solar cells, and the source and load power flow is automatically balanced by the circuit itself without any external phase control.
Abstract: A novel interface circuit between solar cells and a commercial AC source using Van Allen's multivibrator is presented. In this circuit, the AC source is used as a backup for solar cells, and the source and load power flow is automatically balanced by the circuit itself without any external phase control. Based on the analysis of the characteristics of solar cells and Van Allen's multivibrator, the authors describe a new method of controlling the DC power from solar cells according to the current load conditions, and a simple and fast optimization method for deriving the maximum solar power is discussed. >
TL;DR: In this paper, the best known methods for calculating solar irradiance at the earth's surface using geostationary satellite data were evaluated and compared, and a summary of the assessments and comparisons carried out on the methods described was made.
TL;DR: In this paper, a 10kW solar furnace at the National Renewable Energy Laboratory (NREL) was used with a reaction chamber designed to deliver to a graphite pellet a solar flux of 1200 W/cm.
Abstract: Of the many methods available to produce fullerenes, one of the most exciting uses highly concentrated sunlight to vaporize the graphite. We have shown in recent experiments, as has the Rice University group, that this method can effectively produce these materials. The 10-kW solar furnace at the National Renewable Energy Laboratory (NREL) was used with a reaction chamber designed to deliver to a graphite pellet a solar flux of 1200 W/cm[sup 2]. Analysis of the resulting soot by mass spectrometry and HPLC has confirmed the existence of fullerenes. Although our results show great promise, a number of fundamental issues still need to be addressed. 5 refs., 4 figs.
TL;DR: In this article, thermal analysis and results of thermal performance tests of solar air heaters with V-corrugated absorber plates were reported. But the results of these tests were limited to three collector types: (a) flow over the absorber, (b) flow on both sides of the absorbers, and (c) flow under the absorbber.
TL;DR: In this article, a rigorous numerical simulation model for the prediction of the combined optical and thermofluid behavior of line-axis concentrating solar energy collectors combines two-dimensional steady-state finite element analysis of convective heat transfer and ray-trace techniques.
ENEA1
TL;DR: In this article, the design and performance of a solar fruit and vegetable dryer developed at Area Energetica, Dipartimento SIRE, Divisione Ingegneria Sperimentale of ENEA-C.R.E. Trisaia was described.
TL;DR: In this paper, an ejector refrigeration system that uses a conventional refrigerant (R-114) is introduced as a possible mechanism for providing solar-based air-conditioning.
TL;DR: In this paper, the authors proposed a compression enhanced ejector system in which mechanical energy is used to boost the pressure of the secondary stream into the ejector, such a boost improves the performance of the whole system.
Patent•
30 Nov 1993
TL;DR: In this article, a method for concentrating solar energy waveform energy is directed to a predetermined region of the atmosphere located a pre-established distance above a surface of the earth, and the directing of the energy is controlled so as to modulate an index of refraction of air in the predetermined region.
Abstract: In a method for concentrating solar energy waveform energy is directed to a predetermined region of the atmosphere located a pre-established distance above a surface of the earth. The directing of the energy is controlled so as to modulate an index of refraction of air in the predetermined region of the atmosphere to produce a predetermined refraction index pattern in the region. The distribution of solar radiation is modified as it passes through the atmospheric region to thereby concentrate the solar radiation at a predetermined location.
TL;DR: In this paper, a formalism describing the conversion of radiation energy into work can be constructed in terms of energy and entropy fluxes, which leads, among others, to the Landsberg efficiency, a formula expressing an upper bound to photothermal solar energy conversion.
Abstract: A formalism describing the conversion of radiation energy into work can be constructed in terms of energy and entropy fluxes. This leads, among others, to the Landsberg efficiency, a formula expressing an upper bound to photothermal solar energy conversion. The relationship between the above approach and the viewpoint of endoreversible thermodynamics is investigated. An extension to photovoltaic solar energy conversion is formulated. A generalization of the Landsberg formula, for a solar energy converter with arbitrary bandgap, is presented.
TL;DR: In this paper, solar energy conversion is described in the framework of endoreversible thermodynamics, i.e., a recently developed subset of irreversible thermodynamics and the authors deduce the photovoltaic, the photothermal and the photochemical solar energy converter, besides of a few other, non-solar devices.
Journal Article•
TL;DR: Several types of surface preparations, other than selective absorbers, can be utilized for economical collection and control of solar energy as discussed by the authors, which can be used for both solar thermal collectors and for window systems in buildings.
Abstract: Several types of coatings and surface preparations, other than selective absorbers, can be utilized for economical collection and control of solar energy. These films can be used for both solar thermal collectors and for window systems in buildings. Numerous non-selective, hot and cold mirror, and antireflective coatings are reviewed and tabulated. Detailed reflectance, emittance and thermal stability data are presented for these various coatings. Both moderately selective and non-selective absorbers consist of black paint, chemical conversion finishes, electroplated and anodized coatings. Both hot and cold mirror coatings are selective transmitters of energy. They are considered for applications where light and heat need to be separated and trapped. Antireflective films are evaluated for use on glass surfaces. The findings of this study reveal many different types of inexpensive and promising coatings for efficient utilization of solar energy.
TL;DR: In this paper, the authors describe a CIGS-based solar cell that demonstrates an open-circuit voltage approaching 700 mV and a total area conversion efficiency of 12.2%.
Abstract: An important development in polycrystalline Cu(In,Ga)Se2 (CIGS) thin‐film photovoltaic solar cells is the attainment of a high voltage device simultaneous with state‐of‐the‐art conversion efficiency. This letter describes a CIGS‐based solar cell that demonstrates an open‐circuit voltage (Voc) approaching 700 mV and a total‐area conversion efficiency of 12.2%. The high value of Voc was achieved by grading In/Ga through the absorber by a computer‐controlled physical vapor deposition (PVD) process that utilizes variable metal fluxes.
Proceedings Article•
02 Jun 1993
TL;DR: In this paper, a non-preemptive goal programming model for the optimal allocation of energy resources to various energy end uses is presented for bridging the energy supply and demand gap in India.
Abstract: The optimal allocation of energy resources to various energy end uses is an important strategy for bridging the energy supply and demand gap in India. It has been recognized that the allocation should be guided by multiple criteria. A multiobjective programming model for such an allocation process is presented in the paper. The normative model has been applied for the households sector of Madras city. The model is solved using non pre-emptive goal programming. Variations in the original model have been made to build alternative scenarios. The results of the original model and the alternative scenarios indicate that the use of solar thermal energy, natural gas, LPG, fuelwood, kerosene and lignite should be promoted for cooking, and the use of grid electricity and diesel, should be promoted for meeting water pumping demands. They favour the use of electricity generated from diesel for lighting, and the use of solar photovoltaics for meeting the electricity demands of household appliances. The results also indicate that grid electricity and electricity generated from fuelwood should be promoted to meet the demands of all the four household end uses, and point to the need for more research into solar photovoltaics, which may become competitive for meeting household demands in the future.
TL;DR: The potential of coupled solar stills as a mean for improving solar distillation yield is investigated in this article, where a model for a simple solar still assisted by an external solar collector is presented.
Book•
01 Jan 1993
TL;DR: In this paper, the authors provide a simple background to PV pumping technology and to help to identify the situations in which solar pumping should be considered and provide information dealing with the range of currently available equipment as well as the practical aspects of choosing a pumping system.
Abstract: Although the number of units in the field is still small, solar photovoltaic powered pumping systems offer many advantages over the more traditional technologies. Because there are few moving parts, maintenance is reduced to a minimum, and reliability is very high. Also, because the time of greatest water demand usually coincides with the maximum daily solar energy, the available pumping power is well matched to the demand. Solar pumping was first introduced into the field in the late nineteen-seventies, and since manufacturers have refined their products to give considerable increases in performance and reliability. The steady fall in prices of solar photovoltaic (PV) panels means that solar pumping is becoming economic for an increasingly wide range of applications. This guide is written for the potential user to give a simple background to PV pumping technology and to help to identify the situations in which solar pumping should be considered. The paper illustrates typical applications and reviews current technology in solar pumping. It also gives information dealing with the range of currently available equipment as well as the practical aspects of choosing a pumping system.