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Measured performance of selective glazings

Description: Measurements of the net heat flow through four selective glazings in comparison with clear double glazing under late summer outdoor conditions are presented. The SHGC for each glazing is extracted from the data and shown to be angle-dependent. The method of extracting the angle-dependent SHGC from the data is checked by comparing the measured SHGC for the clear double glazing to the calculation of OW 4. 1, which is assumed to be correct. Good agreement between the two is found. The measured angle-dependent SHGC`s of the selective glazings are then used to test the OW 4.1 selective glazing calculation and good agreement is again found.
Date: July 1, 1995
Creator: Klems, J.H.; Yazdanian, M. & Kelley, G.O.
Partner: UNT Libraries Government Documents Department

High accuracy diffuse horizontal irradiance measurements without a shadowband

Description: The standard method for measuring diffuse horizontal irradiance uses a fixed shadowband to block direct solar radiation. This method requires a correction for the excess skylight blocked by the band, and this correction varies with sky conditions. Alternately, diffuse horizontal irradiance may be calculated from total horizontal and direct normal irradiance. This method is in error because of angular (cosine) response of the total horizontal pyranometer to direct beam irradiance. This paper describes an improved calculation of diffuse horizontal irradiance from total horizontal and direct normal irradiance using a predetermination of the angular response of the total horizontal pyranometer. We compare these diffuse horizontal irradiance calculations with measurements made with a shading-disk pyranometer that shields direct irradiance using a tracking disk. Results indicate significant improvement in most cases. Remaining disagreement most likely arises from undetected tracking errors and instrument leveling.
Date: December 31, 1995
Creator: Schlemmer, J.A & Michalsky, J.J.
Partner: UNT Libraries Government Documents Department

Estimating monthly means of daily totals of direct normal solar radiation and of total solar radiation on a south-facing, 45/sup 0/, tilted surface

Description: Direct Normal, DN, radiation data is presently available for only a few sites in the country while total horizontal, TH, radiation is available for many locations. If a mathematical function relating DN and TH were established, solar engineers could estimate DN for any site for which TH data is available. Total radiated energy on a tilted surface, TT, is also of interest to solar engineers. A recently completed report includes TT values for a surface tilted at 45/sup 0/ for 26 sites. A function relating TT and TH would permit one to estimate TT for sites where only TH data is available. Empirically derived functions relating DN and TH and TT and TH are presented.
Date: July 1, 1977
Creator: Boes, E.C. & Hall, I.J.
Partner: UNT Libraries Government Documents Department

[Global warming and the running average sunspot number]

Description: It has been reported in your pages that the Bush administration`s views and actions regarding how or whether to react to possible global warming due to greenhouse gases have been influenced by the so-called Marshall report. This unrefereed report, released by the George C. Marshall Institute, had as its principal conclusion the finding that the 0.5{degree} C global warming of the last century was mostly due to solar variability and, thus, the greenhouse warming of the 21st century can be expected to be a relatively small l{degree} C or so. The authors support this finding by comparing the 33-year running average sunspot number with the trend in annual average global temperature and noting the parallel between the two, especially during the 1940s--1960s when the temperature trend was downward. Subsequent letters to Science debated the merits of this and other conclusions contained in the report. I now present additional technical evidence which shows that, quite aside from the question of whether the data presented in the report support its conclusions, the actual figure on which the above conclusion is based is in error.
Date: May 1, 1994
Creator: Fernau, M. E.
Partner: UNT Libraries Government Documents Department

Ultrasensitive Searches for the Axion

Description: The axion, a hypothetical elementary particle arising from a compelling solution to the strong-CP problem, has eluded discovery for three decades. Experiments based on coherent axion-photon mixing in strong magnetic fields are just now reaching the sensitivity to detect it, either as the dark matter or as a component of the solar flux. Although of lower sensitivity, purely laboratory experiments hold potential for surprise.
Date: July 14, 2006
Creator: van Bibber, K A & Rosenberg, L J
Partner: UNT Libraries Government Documents Department

Quantum and Thermal Conversion of Solar Energy to Useful Work

Description: This paper will summarize the results of a thermodynamic analysis of quantum; and thermal processes for converting sunlight into useful work. Quantum and; thermal processes acting alone as well as combined quantum-thermal processes will be discussed. Two types of combined processes have been analyzed, the thermally coupled process and the thermally decoupled process. These processes were addressed because there is a hope that a combined quantum-thermal conversion system will prove to be cheaper than either system acting separately. A first step in determining cost is to determine maximum system efficiency. The analysis also indicates the concept with the greatest potential so that further efforts can focus on it. Previous analyses of the thermodynamics of quantum and thermal conversion have been performed by Haught (Ref. 1), Bolton (Ref. 2), Ross (Ref. 3) , and others. This paper will review Haught's analysis and present the results of an extension of this analysis to a thermally decoupled combined quantum/thermal system performed at SERI. Only systems using unconcentrated solar flux will be considered in the present analysis.
Date: December 1, 1983
Creator: Johnson, D. H.
Partner: UNT Libraries Government Documents Department

Dry deposition of pan to grassland vegetation

Description: Peroxyacetyl nitrate or PAN (CH{sub 3}C(O)OONO{sub 2}) is formed in the lower troposphere via photochemical reactions involving nitrogen oxides (NO{sub x}) and non-methane hydrocarbons (NMHCs). PAN has a lifetime in the free troposphere of about three months and is removed by photolysis or reaction with OH. Dry deposition will decrease its lifetime, although the few measurements that have been made indicate that this process is slow. Measurements of the uptake of PAN by alfalfa in growth chambers indicated that the dry deposition velocity (downward flux divided by concentration at a specified height) was 0.75 cm s{sup {minus}1}. Garland and Penkett measured a dry deposition velocity of 0.25 cm s{sup {minus}1} for PAN to grass and soil in a return-flow wind tunnel. Shepson et al. (1992) analyzed trends of PAN and O{sub 3} concentrations in the stable nocturnal boundary layer over mixed deciduous/coniferous forests at night, when leaf stomata were closed, and concluded that the deposition velocity for PAN was at least 0.5 cm s{sup {minus}1}. We measured the dry deposition velocity of PAN to a grassland site in the midwestern United States with a modified Bowen ratio technique. Experiments were conducted on selected days during September, October, and November of 1990. An energy balance Bowen ratio station was used to observe the differences in air temperature and water vapor content between heights of 3.0 and 0.92 m and to evaluate the surface energy balance. Air samples collected at the same two heights in Teflon {reg_sign} bags were analyzed for PAN by a gas chromatographic technique. We present an example of the variations of PAN concentrations and gradients observed during the day and compare measurements of the dry deposition velocity to expectations based on the physicochemical properties of PAN.
Date: January 1, 1994
Creator: Doskey, P.V.; Wesely, M.L.; Cook, D.R. & Gao, W.
Partner: UNT Libraries Government Documents Department

A comparison between calculated and measured SHGC for complex fenestration systems

Description: Calorimetric measurements of dynamic net heat flow through a complex fenestration system consisting of a buff venetian blind inside clear double glazing are used to derive the direction-dependent beam SHGC (solar heat gain coefficient) of the fenestration. The data are compared with calculations according to a proposed general method for deriving complex fenestration system SHGC`s from bidirectional layer optical properties and generic calorimetric properties. Previously published optical data for the same venetian blind and generic inward-flowing fraction measurements are used in the calculation. Satisfactory agreement is found between SHGC measurements and calculation. Significant dependence on incident angle was found in the measured SHGC`s. Profile angle was not found to be a useful variable in characterizing the system performance. Predicted SHGC was found to be inherently dependent on two angles, although only the incident angle variations were observable under test conditions.
Date: September 1995
Creator: Klems, J. H.; Warner, J. L. & Kelley, G. O.
Partner: UNT Libraries Government Documents Department

Using ARM Data to Evaluate Satellite Surface Solar Flux Retrievals

Description: The accurate, long-term radiometric data collected by Atmospheric Radiation Measurement (ARM) has become essential to the evaluation of surface radiation budget data from satellites. Since the spatial and temporal characteristics of data from these two sources are very different, the comparisons are typically made for long-term average values. While such studies provide a general indication of the quality of satellite flux products, more detailed analysis is required to understand specific retrieval algorithm weaknesses. Here we show how data from the ARM shortwave flux analysis (SFA) value added product (VAP) are being used to assess solar fluxes in the Global Energy and Water Cycle Experiment (GEWEX) Surface Radiation Budget (SRB), release 2.5.
Date: March 18, 2005
Creator: Hinkelman, L. M.; Stackhouse, P. W.; Young, D. F.; Long, C. N. & Rutan, D.
Partner: UNT Libraries Government Documents Department

Photodegradation effects in materials exposed to high flux solar and solar simulated radiation

Description: This report contains study results about photodegradation effects in materials exposed to high flux solar and solar simulated radiation. The studies show that high flux photoirradiation of materials can result in significant changes in the stability of materials. Photodesorption and photo-enhanced oxidation were determined to be the major mechanisms. These mechanisms were shown to affect, in extremely adverse ways, the expected thermal stability of solar relevant materials, especially stainless steels, (It is expected that related high temperature alloy steels will be similarly affected.) An analytical expression was generated to predict the flux behavior of the steels using {number_sign}304 as a prototypical stainless steel system.
Date: April 1, 1992
Creator: Ignatiev, A.
Partner: UNT Libraries Government Documents Department

Comparison of predicted optical performance with measured results for dish concentrators

Description: Several optical design tools have been developed at the National Renewable Energy Laboratory (NREL) during the past two years. These have been used extensively both in-house and by industry to analyze dish concentrator systems and to optimize performance of such designs. The first program, OPTDSH, models single-element dish concentrators. The second code, ODMF, allows multifacet dish arrays to be modeled. The accuracy of performance simulations by these programs has been established by comparing predicted results with measured on-sun data. ODMF evolved from NREL`s High-Flux Solar Furnace (HFSF) design tool, SOLFUR, and in fact is a special case of SOLFUR in which the primary facet array is ``on sun.`` Consequently, confirmation of the accuracy of SOLFUR would verify the results from ODMF as well. Furthermore, because OPTDSH can be viewed as a single-facet case of ODMF, determination of the precision of SOLFUR/ODMF would also substantiate OPTDSH. Thus, the approach to verifying the correctness of all three codes was to compare flux patterns as predicted by SOLFUR with those actually measured at NREL`s HFSF. Measured vs. calculated data have been compared on the basis of flux distribution (in terms of contour plots) and peak flux for both single-facet and multiple-facet cases. Agreement in measured vs. predicted peak flux values has been obtained within the uncertainty associated with the measurement/calibration process. Excellent agreement has also been demonstrated by comparing contour maps of measured vs. computed flux levels. 7 refs.
Date: April 1, 1991
Creator: Jorgensen, G.
Partner: UNT Libraries Government Documents Department

ARAMS/FRAMES JOINT FREQUENCY DATA (JFD) GENERATOR

Description: An ARAMS/FRAMES utility entitled ''Joint Frequency Data (JFD) Generator'' provides the capability of creating joint frequency tables. The resultant JFD tables contain summaries of the frequency of occurrence of meteorological dispersion, wind speed, and wind direction that are required as input in climatological air dispersion models. The JFD Generator computations are made by an updated version of the EPA STAR (STAbility ARray) program. Surface observations are combined with computed seasonally and diurnally varying solar flux rates to estimate the ambient atmospheric dispersion rates, represented as a stability category. The wind speeds and directions are obtained directly from the hourly surface observation data. The product is a file in a format that can be directly read by an air dispersion model. The JFD Generator can input hourly meteorological surface observation data in CD-144, Samson, and SCRAM data formats. An enhanced joint frequency table file that can be read directly by the ARAMS/FRAMES interface is produced. The output file has a format can be used by the MEPAS air dispersion program or can be modified for input to other models requiring joint frequency input.
Date: October 4, 2006
Creator: Droppo, James G. & Pelton, Mitch A.
Partner: UNT Libraries Government Documents Department

Solar radiation flux and insolation data for southern Idaho

Description: Weather data pertinent to the development of solar energy heating in the Northern Intermountain region were desired for the purpose of assessing the usefulness and potential economics of utilizing solar energy in the region. The data reported herein are for several southern Idaho stations and for Salt Lake City, and are considered to be representative of the area from the eastern slopes of the Cascades to the western slopes of the northern Rockies. While existing data are not highly accurate and are derived from widely separated stations, approximate estimates may be made for the solar flux in the area. Methods for acquiring more detailed data in specific locations are described in this report. (auth)
Date: November 1, 1975
Creator: Buchenauer, C.J.
Partner: UNT Libraries Government Documents Department

High-flux solar photon processes

Description: This study was commissioned by the National Renewable Energy Laboratory (NREL) for the purpose of identifying high-flux photoprocesses that would lead to beneficial national and commercial applications. The specific focus on high-flux photoprocesses is based on the recent development by NREL of solar concentrator technology capable of delivering record flux levels. We examined photolytic and photocatalytic chemical processes as well as photothermal processes in the search for processes where concentrated solar flux would offer a unique advantage. 37 refs.
Date: June 1, 1992
Creator: Lorents, D C; Narang, S; Huestis, D C; Mooney, J L; Mill, T; Song, H K et al.
Partner: UNT Libraries Government Documents Department

Application of the adjoint method in atmospheric radiative transfer calculations

Description: The transfer of solar radiation through a standard mid-latitude summer atmosphere including different amounts of aerosols (from clear to hazy) has been computed. The discrete-ordinates (S/sub N/) method, which has been developed to a high degree of computational efficiency and accuracy primarily for nuclear radiation shielding applications, is employed in a forward as well as adjoint mode. In the adjoint mode the result of a transfer calculation is an importance function (adjoint intensity) which allows the calculation of transmitted fluxes, or other radiative responses, for any arbitrary source distribution. The theory of the adjoint method is outlined in detail and physical interpretations are developed for the adjoint intensity. If, for example, the downward directed solar flux at ground level, F/sub lambda/ (z = 0), is desired for N different solar zenith angles, a regular (forward) radiative transfer calculation must be repeated for each solar zenith angle. In contrast, only 1 adjoint transfer calculation gives F/sub lambda/ (z = 0) for all solar zenith angles in a hazy aerosol atmosphere, for 1 wavelength interval, in 2.3 seconds on a CDC-7600 computer. A total of 155 altitude zones were employed between 0 and 70 km, and the convergence criterion for the ratio of fluxes from successive iterations was set at 2 x 10/sup -3/. Our results demonstrate not only the applicability of the highly efficient modern S/sub N/ codes, but indicate also conceptual and computational advantages when the adjoint formulation of the radiative transfer equation is used.
Date: January 1, 1979
Creator: Gerstl, S.A.W.
Partner: UNT Libraries Government Documents Department

Measurement of Circumsolar Radiation. Status Report

Description: The major accomplishments of this project include the design, construction, and deployment of four complete circumsolar telescope systems. The telescopes have been maintained and data have been collected from a total of nine sites over the past two years. The data upon reaching LBL have been compiled, validated and analyzed for dissemination to DOE and other users. LBL has been collaborating with other national laboratories to quantify the impact of circumsolar radiation on specific solar collector designs. Requests for data from a wide variety of solar users have been fulfilled.
Date: September 1978
Creator: Grether, D. F.; Hunt, A.; Evans, D. & Wahlig, M.
Partner: UNT Libraries Government Documents Department

Trends in ozone and temperature structure: comparison of theory and measurements

Description: Comparison of model calculated trends in ozone and temperature due to inferred variations in trace gas concentrations and solar flux, is made with available analyses of observations. In general, the calculated trends in total ozone and the vertical ozone distribution agree well with the measured trends. However, there are too many remaining theoretical and sampling uncertainties to establish causality. Although qualitatively in agreement, the observed temperature decrease in the upper stratosphere is significantly larger than that calculated. Theoretical results suggest a significant influence on stratospheric ozone from solar flux variations, but observational evidence is at best inconclusive. Overall, the trend comparisons tend to be consistent with the hypothesis that several different anthropogenic influences are affecting the present global atmosphere. 7 references, 3 figures, 2 tables.
Date: August 1, 1984
Creator: Wuebbles, D.J.
Partner: UNT Libraries Government Documents Department

Formation of gas-phase peroxides in a rural atmosphere: An interpretation of the recent SOS/SERON field results

Description: Hydrogen perioxide (H{sub 2}O{sub 2}) and certain organic peroxides such as hydroxymethyl-hydroperoxide (HMHP), are gas-phase oxidants present in the atmosphere at ppbv concentration levels. These oxidants play an important role in atmospheric chemistry. In addition, precipitation containing H{sub 2}O{sub 2} is toxic to trees, and it has also been suggested that organic peroxides formed presumably by ozone reactions with biogenic alkenes are responsible for leaf disorders. Recently, we have developed a nonenzymatic method or aqueous-phase H{sub 2}O{sub 2} measurement, using Fenton reagent and fluorescent hydroxy- benzoic acid. The new method, in conjunction with the well-known method of p-hydroxyphenylacetic acid and horseradish peroxidase for total peroxides, and together with an improved gas scrubber to mitigate sampling line problems, has been successfully deployed in recent SOS/SERON field measurements in rural Georgia. For the first time, continuously measured and speciated gas-phase peroxide data have become available, making it possible to examine some aspects of the ozone chemistry leading to the formation of these oxidants. It is observed that daily H{sub 2}O{sub 2} maximum frequently occurs at a different time than does HMHP, and that H{sub 2}O{sub 2} concentration, but not HMHP, tends to correlate with solar fluxes measured at the same location. These findings seem to indicate that the formation mechanisms for H{sub 2}O{sub 2} and organic peroxides are basically different. It is likely that H{sub 2}O{sub 2} is formed from radical-radical recombination, while HMHP is formed by ozone-alkene reactions. Since the gas-phase ozone-alkene reactions are usually too slow to account for the diurnal concentration variations observed for HMHP, heterogeneous processes involving ozone and alkenes are also a possibility.
Date: September 1, 1993
Creator: Lee, J. H.; Tang, I. N. & Weinstein-Lloyd, J. B.
Partner: UNT Libraries Government Documents Department

Radiative flux calculations at UV and visible wavelengths

Description: A radiative transfer model to calculate the short wavelength fluxes at altitudes between 0 and 80 km has been developed at LLNL. The wavelength range extends from 175--735 nm. This spectral range covers the UV-B wavelength region, 250--350 nm, with sufficient resolution to allow comparison of UV-B measurements with theoretical predictions. Validation studies for the model have been made for both UV-B ground radiation calculations and tropospheric solar radiative forcing calculations for various ozone distributions. These studies indicate that the model produces results which agree well with respect to existing UV calculations from other published models.
Date: October 1, 1993
Creator: Grossman, A. S.; Grant, K. E. & Wuebbles, D. J.
Partner: UNT Libraries Government Documents Department

Modification of flux profiles using a faceted concentrator

Description: The use of a faceted solar concentrator allows for some flexibility in aiming strategy and in the intensity of the resulting flux profile at the target. This can be an advantage when considering applications that do not necessarily require maximum concentration, particularly emerging, new applications in solar processed advanced materials. This paper will describe both an analysis of predicted flux profiles for several different aiming strategies using the SOLFUR computer code and experiments to characterize the actual flux profiles realized with a selected aiming strategy. The SOLFUR code models each of the furnace components explicitly. Aim points for each facet can be specified. Thus many strategies for adjusting aim points can be easily explored. One strategy calls for creating as uniform a flux over as large an area as possible. We explored this strategy analytically and experimentally. The experimental data consist of flux maps generated by a video imaging system calibrated against absolute flux measurements taken with circular foil calorimeters. Results from the analytical study and a comparison with the experimental data indicate that uniform profiles can be produced over fairly large areas.
Date: January 1, 1993
Creator: Lewandowski, A.; Scholl, K. & Bingham, C.
Partner: UNT Libraries Government Documents Department