Variations In Incident Radiation Research Articles

Effect of different aluminium oxide based nanofluid concentrations on the efficiency of solar water desalination system

In this study, the effect of different concentration of the Aluminium oxide-based nanofluid on the performance of Solar Desalination system was discussed. The Aluminium Oxide was used in different concentrations 1%, 2% and 6% on weight basis. The flow rate was also varied and its effect on the system efficiency was discussed. The nanofluid was compared with the water and there was improvement occurred in the efficiency during variation of incident radiation. With an increase in the concentration of Aluminium oxide nanoparticles, improvement in the efficiency was attained. More efficiency was attained at 6% nanoparticles addition with compared to 1% and 2%. With an increase in mass flow rate of the fluid, the nanofluid also showed better performance in terms of improvement in the efficiency.

Effects of operational and environmental parameters on the performance of a solar photovoltaic-thermal collector

A steady, three-dimensional model considering all the layers of a solar photovoltaic-thermal collector with sheet and tube heat exchanger is developed. The model takes the solar heat loading as the thermal input to estimate the temperature distribution in the collector for variation in incident radiation, ambient temperature, wind velocity, flow rate and inlet water temperature. Based on the numerical results, the parameter that highly influences collector performance is the coolant mass flow rate. For the range of flow rates considered, a maximum efficiency of 93.01% is obtained for 44 LPH. Further, a techno-economic comparison of the photovoltaic-thermal system is made with a photovoltaic system and a flat plate thermal system. The increase in electrical efficiency of the photovoltaic-thermal system is only marginal to that of the photovoltaic system but the overall efficiency of the former is high. The annual cost of energy that the photovoltaic-thermal system can supply is found to be 0.13 USD/kWh from economic analysis.

Phenoseasonal subcanopy light dynamics and the effects of light on the physiological ecology of a common understory shrub, Lindera benzoin

The purpose of this work was to quantify the variation of subcanopy spatiotemporal light dynamics over the course of a year and to link it to the physiological ecology of the understory shrub, Lindera benzoin L. Blume (northern spicebush). Covering all seven phenoseasons of a deciduous forest, this work utilized a line quantum sensor to measure the variation in subcanopy light levels under all sky conditions at different times of the day. A total of 4,592 individual subcanopy measurements of photosynthetic photon flux density (PPFD, μmol m-2 s-1) were taken as 15-second spatially-integrated one-meter linear averages to better understand the dynamism of light exposure to L. benzoin. Both open (n = 2, one continuous and one instantaneous) and subcanopy location (n = 25) measurements of PPFD were taken on each sampling date in and near the forested plot (Maryland, USA). In addition, we explored the effect of four photointensity-photoperiod combinations on the growth of L. benzoin under controlled conditions to compare to field conditions. On average, understory PPFD was less than 2% of open PPFD during the leafed months and an average of 38.8% of open PPFD during leafless winter months, indicating that: (1) often overlooked woody surfaces intercept large amounts of light; and (2) spicebush within the plot receive limited light even in early spring before canopy leaf-out. Statistical results suggested phenoseason accounted for nearly three-quarters of the variation in incident radiation between the three plant canopy heights. Spicebush under controlled conditions exhibited the highest fitness levels at an intensity of 164.5 μmol m-2 s-1 for 12-hour duration. Similarly, spicebush growth in the field occurred at subcanopy locations receiving higher incidence of PPFD (i.e., >128 μmol m-2 s-1). Results suggest that the ecological niche for these plants is very specific in terms of light intensity.

Genotypic Variation in the Response of Rice (Oryza sativa L.) to Increased Atmospheric Carbon Dioxide and its Physiological Basis

AbstractIncreasing atmospheric carbon dioxide concentration (Ca) is one aspect of global change that will have a significant impact on the productivity of agricultural crops. Crop yields have been shown to increase with increasing Ca. The magnitude of yield response to increased Ca could vary depending on genotypic and environmental factors. The objective of this study was to determine the genotypic variation of yield response and its physiological basis in rice (Oryza sativa L.) through an initial varietal screening using 16 genotypes. The genotypes were grown under two concentrations of Ca, i.e. 370 ± 28 (ambient) and 570 ± 42 (elevated) μmol mol−1, in open top chambers under lowland field conditions at the Rice Research and Development Institute in Sri Lanka (7°50′N, 80°50′E) from May to August 2001 (yala season) and from November 2001 to March 2002 (maha). Ca within chambers was maintained around target concentrations by a computer‐based real‐time data acquisition and control system. There was significant variation between genotypes in the response of yield to elevated Ca, with absolute increases up to 530 g m−2 in yala and 347 g m−2 in maha. In relative terms, percentage yield increases from ambient to elevated Ca ranged from 4 % to 175 % in yala and from 3 % to 64 % in maha. Genotypic variation in yield showed significant positive correlations with light‐saturated net photosynthetic rate of the flag leaf during the grain‐filling stage. This indicated that increased assimilate supply and its genotypic variation contributed to the observed genotypic variation in yield response to elevated Ca. Furthermore, the capacity to develop a larger reproductive sink through increased panicle number per m2 and increased number of grains per panicle contributed to greater yield at elevated Ca. There was a significant genotype × season interaction with genotypes responding differentially to increased Ca in the two seasons. This was mainly due to inter‐seasonal variation in incident radiation during the grain‐filling stage. Our results demonstrate the significant genotypic variation that exists within the rice germplasm, in the response to increased Ca of yield and its correlated physiological parameters. A subset of genotypes from screening trials such as the present study can be used for more in‐depth analysis of the influence of elevated Ca on processes responsible for yield determination in rice and for molecular studies to elucidate the genetic basis of the response to increased Ca. This could pave the way for breeding genotypes which are more productive in a future high CO2 environment, provided that genotypes with greater flexibility in their physiology are selected to counter the genotype × environmental interaction.

Two-dimensional radiative transfer in a finite scattering planar medium

The source function, radiative flux, and intensity at the boundaries are calculated for a two-dimensional, scattering, finite medium subjected to collimated radiation. The scattering phase function is composed of a spike in the forward direction super-imposed on an isotropic background. Exact radiative transfer theory is used to formulate the problem and Ambarzumian's method is used to obtain results. Using the principle of superposition, the results for any step variation in incident radiation are expressed in terms of universal functions for the semi-infinite step case. Two-dimensional effects are most pronounced at large optical thicknesses and albedos.

The Distribution of Solar Radiation within a Deciduous Forest

Solar radiation was measured within and above an east Tennessee deciduous forest over a 2—yr period. Diurnal patterns of within—forest radiation follow the temporal variation in incident radiation but become more irregular with depth in the forest because of the highly variable penetration of beam radiation in space and in time. Seasonally, radiation in the forest increases substantially from winter to its annual maximum in early spring as solar elevations increase. Although solar elevations continue to rise each day until the summer solstice, amounts of total radiation and its beam component drop sharply in the forest with the advent of leaf expansion. Diffuse radiation in the forest continues to increase slowly following the onset of leaf expansion but reverses as the forest approaches a fully leafed state. Following the summer solstice, forest structure remains essentially static until abscission while solar elevations decrease. In summer and early autumn, total radiation and both its beam and diffuse components decrease slowly in the forest to their annual minimum in autumn. With leaf abscission and subsequent fall, radiation increases slightly in the forest but soon declines again as solar elevations approach their annual minimum of the winter solstice.

Measurement of the reflectances for solar radiation of the coats of live animals

1. A substitution method is described for measuring, with a microsolarimeter, reflectances for solar radiation of the coats of comparatively large live animals. The measurements were made in 8 positions round the trunk. From these measurements a mean reflectance, weighted for variations in incident radiation, was calculated. 2. Reflectance measured on Jersey heifers, water buffalo calves and adult Merino sheep had a standard deviation from the mean for pairs of estimates varying from 0·01 to 0·04 according to the position on the trunk. The standard deviation for the weighted mean reflectance was 0·01. 3. It is shown that on an animal of uniform colour the reflectance is greater for positions receiving radiation reflected by the ground than for those receiving direct solar and sky radiation.