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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

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

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

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 1, 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

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

High-flux solar photon processes: Opportunities for applications

Description: The overall goal of this study was to identify new high-flux solar photon (HFSP) processes that show promise of being feasible and in the national interest. Electric power generation and hazardous waste destruction were excluded from this study at sponsor request. Our overall conclusion is that there is promise for new applications of concentrated solar photons, especially in certain aspects of materials processing and premium materials synthesis. Evaluation of the full potential of these and other possible applications, including opportunities for commercialization, requires further research and testing. 100 refs.
Date: June 1, 1992
Creator: Steinfeld, J I; Coy, S L; Herzog, H; Shorter, J A; Schlamp, M; Tester, J W et al.
Partner: UNT Libraries Government Documents Department

Measurements of isotope effects in the photoionization of N2 and implications for Titan's atmosphere

Description: Isotope effects in the non-dissociative photoionization of molecular nitrogen (N2 + h nu -> N2+ + e-) may play a role in determining the relative abundances of isotopic species containing nitrogen in interstellar clouds and planetary atmospheres but have not been previously measured. Measurements of the photoionization efficiency spectra of 14N2, 15N14N, and 15N2 from 15.5 to 18.9 eV (65.6-80.0 nm) using the Advanced Light Source at Lawrence Berkeley National Laboratory show large differences in peak energies and intensities, with the ratio of the energy-dependent photoionization cross-sections, sigma(14N2)/sigma(15N14N), ranging from 0.4 to 3.5. Convolving the cross-sections with the solar flux and integrating over the energies measured, the ratios of photoionization rate coefficients are J(15N14N)/J(14N2)=1.00+-0.02 and J(15N2)/J(14N2)=1.00+-0.02, suggesting that isotopic fractionation between N2 and N2+ should be small under such conditions. In contrast, in a one-dimensional model of Titan's atmosphere, isotopic self-shielding of 14N2 leads to values of J(15N14N)/J(14N2) as large as ~;;1.17, larger than under optically thin conditions but still much smaller than values as high as ~;;29 predicted for N2 photodissociation. Since modeled photodissociation isotope effects overpredict the HC15N/HC14N ratio in Titan's atmosphere, and since both N atoms and N2+ ions may ultimately lead to the formation of HCN, estimates of the potential of including N2 photoionization to contribute to a more quantitative explanation of 15N/14N for HCN in Titan's atmosphere are explored.
Date: December 30, 2010
Creator: Croteau, Philip; Randazzo, John B.; Kostko, Oleg; Ahmed, Musahid; Liang, Mao-Chang; Yung, Yuk L. et al.
Partner: UNT Libraries Government Documents Department

Innovative solar thermochemical water splitting.

Description: Sandia National Laboratories (SNL) is evaluating the potential of an innovative approach for splitting water into hydrogen and oxygen using two-step thermochemical cycles. Thermochemical cycles are heat engines that utilize high-temperature heat to produce chemical work. Like their mechanical work-producing counterparts, their efficiency depends on operating temperature and on the irreversibility of their internal processes. With this in mind, we have invented innovative design concepts for two-step solar-driven thermochemical heat engines based on iron oxide and iron oxide mixed with other metal oxides (ferrites). The design concepts utilize two sets of moving beds of ferrite reactant material in close proximity and moving in opposite directions to overcome a major impediment to achieving high efficiency--thermal recuperation between solids in efficient counter-current arrangements. They also provide inherent separation of the product hydrogen and oxygen and are an excellent match with high-concentration solar flux. However, they also impose unique requirements on the ferrite reactants and materials of construction as well as an understanding of the chemical and cycle thermodynamics. In this report the Counter-Rotating-Ring Receiver/Reactor/Recuperator (CR5) solar thermochemical heat engine and its basic operating principals are described. Preliminary thermal efficiency estimates are presented and discussed. Our ferrite reactant material development activities, thermodynamic studies, test results, and prototype hardware development are also presented.
Date: February 1, 2008
Creator: Hogan, Roy E. Jr.; Siegel, Nathan P.; Evans, Lindsey R.; Moss, Timothy A.; Stuecker, John Nicholas (Robocasting Enterprises, Albuquerque, NM); Diver, Richard B., Jr. et al.
Partner: UNT Libraries Government Documents Department

Durability of Polymeric Encapsulation Materials for Concentrating Photovoltaic Systems (Presentation)

Description: Many concentrating photovoltaic (CPV) systems use a polymeric encapsulant to couple and optical component and/or coverglass to the cell. In that location, the encapsulation improves the transmission of concentrated optical flux through interface(s), while protecting the cell from the environment. The durability of encapsulation materials, however, is not well established relative to the desired service life of 30 years. Therefore, we have initiated a screen test to identify the field-induced failure modes for a variety of popular PV encapsulation materials. An existing CPV module (with no PV cells present) was modified to accommodate encapsulation specimens. The module (where nominal concentration of solar flux is 500x for the domed-Fresnel design) has been mounted on a tracker in Golden, CO (elevation 1.79 km). Initial results are reported here for 18 months cumulative exposure, including the hottest and coldest months of the past year. Characteristics observed at intervals during that time include: visual appearance, direct and hemispherical transmittance, and mass. Degradation may be assessed from subsequent analysis (including yellowness index and cut-on frequency) relative to the ambient conditions present during field exposure. The fluorescence signature observed of all the silicone specimens is examined here, including possible factors of causation -- the platinum catalyst used in the addition cured materials as well as the primer used to promote adhesion to the quartz substrate and superstrate.
Date: March 1, 2012
Creator: Miller, D. C.; Muller, M.; Kempe, M. D.; Araki, K.; Kennedy, C. E. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department

Nanostructured Cobalt Oxide Clusters in Mesoporous Silica as Efficient Oxygen-Evolving Catalysts

Description: The development of integrated artificial photosynthetic systems for the direct conversion of carbon dioxide and water to fuel depends on the availability of efficient and robust catalysts for the chemical transformations. Catalysts need to exhibit turnover frequency (TOF) and density (hence size) commensurate with the solar flux at ground level (1000Wm2, airmass (AM) 1.5)[1]to avoid wasting of incidentsolar photons. For example, a catalyst with a TOF of 100 s1 requires a density of one catalytic site per square nanometer. Catalysts with lower rates or taking up a larger space will require a high-surface-area, nanostructured support that affords tens to hundreds of catalytic sites per square nanometer. Furthermore, catalysts need to operate close to the thermodynamic potential of the redox reaction so that amaximum fraction of the solar photon energy is converted to chemical energy. Stability considerations favor all-inorganic oxide materials, as does avoidance of harsh reaction conditions of pH value or temperature.
Date: January 1, 2009
Creator: Jiao, Feng & Frei, Heinz
Partner: UNT Libraries Government Documents Department

Solar mechanics thermal response capabilities.

Description: In many applications, the thermal response of structures exposed to solar heat loads is of interest. Solar mechanics governing equations were developed and integrated with the Calore thermal response code via user subroutines to provide this computational simulation capability. Solar heat loads are estimated based on the latitude and day of the year. Vector algebra is used to determine the solar loading on each face of a finite element model based on its orientation relative to the sun as the earth rotates. Atmospheric attenuation is accounted for as the optical path length varies from sunrise to sunset. Both direct and diffuse components of solar flux are calculated. In addition, shadowing of structures by other structures can be accounted for. User subroutines were also developed to provide convective and radiative boundary conditions for the diurnal variations in air temperature and effective sky temperature. These temperature boundary conditions are based on available local weather data and depend on latitude and day of the year, consistent with the solar mechanics formulation. These user subroutines, coupled with the Calore three-dimensional thermal response code, provide a complete package for addressing complex thermal problems involving solar heating. The governing equations are documented in sufficient detail to facilitate implementation into other heat transfer codes. Suggestions for improvements to the approach are offered.
Date: July 1, 2009
Creator: Dobranich, Dean D.
Partner: UNT Libraries Government Documents Department