Solar Insolation Conditions Research Articles

고집광 태양열 시뮬레이터의 광학 특성 평가

A solar thermal simulator is suitable for indoor experiments of solar receivers and reactors when solar insolation and weather conditions are not favorable. Moreover, due to the easy control of electric power input, the solar thermal simulator allows the adjustment of power input incident on solar receivers and reactors and thus the implementation of accurate experiments. We manufactured a solar simulator, which is comprised of three sets of a xenon lamp and an elliptical reflector. In order to serve as a test facility, optical characterization of the solar simulator via radiation heat flux measurement is a critical prerequisite. We applied the flux mapping method to measuring the heat flux distribution of the three lamps. We presented the measurement results in terms of the heat flux distribution, the peak heat flux, the power distribution, the maximum power, and the efficiency for electric power conversion into radiation power. Characterization results show that our solar simulator provides the peak heat flux of 3,019 kW/m, the maximum power of 16.9 kW, and the conversion efficiency of 45%, additionally with a 10% operation margin for output increase.

Experimental Performance of a Solar Thermoelectric Cogenerator Comprising Thermoelectric Modules and Parabolic Trough Concentrator without Evacuated Tube

A prototype practical solar-thermoelectric cogenerator composed of (1) a primary component of a pile of solar-selective absorber (SSA) slab, thermoelectric (TE) modules, and a depressed water flow tube (multichannel cooling heat sink, MCS), and (2) a parabolic trough concentrator with aperture area of 2 m A— 2 m and east–west focal axis was constructed. Its cogeneration performance under the best climatic and solar insolation conditions in Guangzhou, China was tested. For simplicity, the evacuated glass tube to cover the primary component was eliminated from the system. Six Bi2Te3 TE modules were arranged in series, directly bonded to the rear surface of the solar absorber slab. The hot-side temperature of the TE module reached up to 152°C. The experimentally obtained instantaneous results for the solar to electrical conversion efficiency, heat exchange coefficient of the MCS, and overall system efficiency under the best environmental and solar insolation conditions were about 1.14%, 56.1%, and 49.5%, respectively. To justify these values, an equivalent thermal network diagram based on a single-temperature-node heat transfer model representing the respective system components was used to analyze the thermal transfer and losses of the system. Finally, electrical power of 18 W was generated, with 2 L/min of hot water at 37°C being produced and stored in the insulated container.

Estimating Hourly Profiles of Insolation based on Weekly Weather Forecast

In this paper, the authors present a simple procedure of estimating weekly profiles of insolation for photovoltaic (PV) power generation output of a roof-top PV system. The model is based on the historical data of solar insolation and weather conditions. Weather conditions are classified into representative patterns such as sunny, cloudy, and rainy, and corresponding hourly profile of insolation is obtained as the most likely values under each weather condition. The system uses the text weather forecast and the probability of precipitation information as input to obtain the estimated weekly profile of insolation. From the results presented here it is shown that such a simple profile can be useful for rating the storage batteries and scheduling electric vehicle charging to better utilize the PV-generated electricity.

Comparative Analysis on the Performance of a Short String of Series-Connected and Parallel-Connected Photovoltaic Array Under Partial Shading

The output power from the photovoltaic (PV) array decreases and the array exhibit multiple peaks when it is subjected to partial shading (PS). The power loss in the PV array varies with the array configuration, physical location and the shading pattern. This paper compares the relative performance of a PV array consisting of a short string of three PV modules for two different configurations. The mismatch loss, shading loss, fill factor and the power loss due to the failure in tracking of the global maximum power point, of a series string with bypass diodes and short parallel string are analysed using MATLAB/Simulink model. The performance of the system is investigated for three different conditions of solar insolation for the same shading pattern. Results indicate that there is considerable power loss due to shading in a series string during PS than in a parallel string with same number of modules.

Fe speciation and Fe/Al ratio in the sediments of southeastern Arabian Sea as an indicator of climate change

Aluminium, titanium and iron are the major lithogeneous contributors to the marine sediment and their abundance varies strikingly with the intensity of monsoonal precipitation. Al and Ti concentrations in a sediment core (SK-129/GC-05) from southeastern Arabian Sea exhibit a very strong positive correlation ( r = 0.92, n = 140) suggesting their lithogenous association, whereas Ti and Fe does not correlate so strongly ( r = 0.44). This suggests that part of Fe is structurally unsupported, as is evident by the two-fold increased Fe/Al ratio (0.87 average) compared to upper continental crust (0.44). The presence of structurally unsupported Fe is confirmed by the sequential leaching of Fe which is associated with different fractions such as exchangeable (0.98%), carbonate (1.98%), Fe–Mn oxide (30.8%), organic carbon (4.7%) and biogenic opal (11.4%) which together constitutes nearly 50% of the bulk Fe content. There is a good correlation between time series Fe/Al and differential solar insolation, suggesting warmer and humid climatic conditions resulted in intense weathering of hinterland rocks, associated with increased monsoonal precipitation, which probably decoupled soluble Fe and transported it to the southeastern Arabian Sea.

Energy analysis of an improved concept of integrated PV panels in an office building in central Greece

During the last decade, steel constructions with glazed façades became popular for commercial buildings in Greece. Moreover, expensive metal, natural stone, marble, ceramic, granite as well as special glass is employed for aesthetic and energy efficiency reasons. This creates opportunities for the introduction of Photovoltaic (PV) modules in double façades. PV modules on south-facing building walls are better placed at a distance from the wall to allow heat rejection and avoid overheating and efficiency loss. Exploiting the rejected heat of the PV modules is also a challenge. In this paper, we examine an improved concept of incorporating PV modules to the south façades of an office building, exploiting both the electricity produced and the heat rejected by the module, to increase building energy efficiency. The PV modules are integrated to the building wall by means of a double façade, which employs intervening ducts for ventilation purposes. The ducts are heating outdoor air, which is employed to cover the ventilation needs of the building, as well as a part of the heating loads. Simulations for typical winter and summer weather and solar insolation conditions are carried out to investigate the building’s energy performance improvements.

Design, development and simulation of PC-based scheme for characterisation of solar photovoltaic modules

This paper presents design, simulation and experimental set up for characterisation of PV cells/modules in the laboratory. A PC-based data acquisition system and associated interface circuit is developed, simulated and used for loading PV module in the laboratory to completely scan its I-V characteristics under varying environmental conditions of solar insolation and temperature. The scheme makes use of hysteresis band controller as PC interface circuit and its linear response against control variable, is established mathematically. The proposed interface circuit is simulated under PSpice to ascertain linearity of response. The comprehensive simulation exercise under PSpice is evolved and described to establish underlying principle and to emulate PC-based control. A PC programme written in 'C' language acquires online data of PV module and stores it in a data file for analysis and plotting of the I-V characteristics.

Presence of Pathogens and Indicator Microbes at a Non-Point Source Subtropical Recreational Marine Beach

Swimming in ocean water, including ocean water at beaches not impacted by known point sources of pollution, is an increasing health concern. This study was an initial evaluation of the presence of indicator microbes and pathogens and the association among the indicator microbes, pathogens, and environmental conditions at a subtropical, recreational marine beach in south Florida impacted by non-point sources of pollution. Twelve water and eight sand samples were collected during four sampling events at high or low tide under elevated or reduced solar insolation conditions. The analyses performed included analyses of fecal indicator bacteria (FIB) (fecal coliforms, Escherichia coli, enterococci, and Clostridium perfringens), human-associated microbial source tracking (MST) markers (human polyomaviruses [HPyVs] and Enterococcus faecium esp gene), and pathogens (Vibrio vulnificus, Staphylococcus aureus, enterovirus, norovirus, hepatitis A virus, Cryptosporidium spp., and Giardia spp.). The enterococcus concentrations in water and sand determined by quantitative PCR were greater than the concentrations determined by membrane filtration measurement. The FIB concentrations in water were below the recreational water quality standards for three of the four sampling events, when pathogens and MST markers were also generally undetectable. The FIB levels exceeded regulatory guidelines during one event, and this was accompanied by detection of HPyVs and pathogens, including detection of the autochthonous bacterium V. vulnificus in sand and water, detection of the allochthonous protozoans Giardia spp. in water, and detection of Cryptosporidium spp. in sand samples. The elevated microbial levels were detected at high tide and under low-solar-insolation conditions. Additional sampling should be conducted to further explore the relationships between tidal and solar insolation conditions and between indicator microbes and pathogens in subtropical recreational marine waters impacted by non-point source pollution.

RESPONSE OF MELATONIN RECEPTOR MT1 IN SPLEEN OF A TROPICAL INDIAN RODENT, FUNAMBULUS PENNANTI, TO NATURAL SOLAR INSOLATION AND DIFFERENT PHOTOPERIODIC CONDITIONS

We analyzed the effect of natural solar insolation and artificial photoperiodic conditions on melatonin MT1 receptor expression of a tropical rodent, Funambulus pennanti. Melatonin mediates reproductive and circadian responses and regulates the production of a large number of cytokines, including interleukin-2 (IL-2), via modulation of MT1 receptor expression. Maximum pineal activity, resulting in high melatonin level, low melatonin receptor expression, and increased splenic mass, was noted in the winter months, while an opposite effect was noted during the summer months. Further, constant light exposure mimicked an “enhanced summer”-like condition with significant hyposplenia, and an opposite effect was observed with constant dark exposure with significant splenomegaly in F. pennanti. In the annual study, a slight increase in melatonin level was noted during the monsoon period, when the duration of photoperiod was the same but the amount of solar insolation and direct radiation decreased. The present study found that not only the duration of natural sunlight (i.e., photoperiod) but the intensity of sunlight expressed by solar insolation affects the circulatory level of melatonin and melatonin receptor expression in this wild tropical rodent. An increase in the circulatory level of melatonin induced a decrease in its receptor subtype MT1 expression in splenic cells, both at the transcriptional and translational levels, thus reflecting autoregulatory down-regulation of melatonin receptors. Therefore, in our animal model, F. pennanti melatonin may be suggested as a molecular messenger of photoperiodic signals (duration and intensity) directly acting via MT1 receptor regulation to adapt the immune system of animals residing in the tropical zone. (Author correspondence: chaldar2001@yahoo.com)

The impact of coniferous forest temperature on incoming longwave radiation to melting snow

AbstractMeasurements were conducted in coniferous forests of differing density, insolation and latitude to test whether air temperatures are suitable surrogates for canopy temperature in estimating sub‐canopy longwave irradiance to snow. Air temperature generally was a good representation of canopy radiative temperature under conditions of low insolation. However during high insolation, needle and branch temperatures were well estimated by air temperature only in relatively dense canopies and exceeded air temperatures elsewhere. Tree trunks exceeded air temperatures in all canopies during high insolation, with the relatively hottest trunks associated with direct interception of sunlight, sparse canopy cover and dead trees. The exitance of longwave radiation from these relatively warm canopies exceeded that calculated assuming canopy temperature was equal to air temperature. This enhancement was strongly related to the extinction of shortwave radiation by the canopy. Estimates of sub‐canopy longwave irradiance using either two‐energy source or two thermal regime approaches to evaluate the contribution of canopy longwave exitance performed better than did estimates that used only air temperature and sky view. However, there was little evidence that such corrections are necessary under cloudy or low solar insolation conditions. The longwave enhancement effect due to shortwave extinction was important to sub‐canopy longwave irradiance to snow during clear, sunlit conditions. Longwave enhancement increased with increasing solar elevation angle and decreasing air temperature. Its relative importance to longwave irradiance to snow was insensitive to canopy density. As errors from ignoring enhanced longwave contributions from the canopy accumulate over the winter season, it is important for snow energy balance computations to include the enhancement in order to better calculate snow internal energy and therefore the timing and magnitude of snowmelt and sublimation. Copyright © 2009 John Wiley & Sons, Ltd.

Hydrogen production characteristics of a bioethanol solar reforming system with solar insolation fluctuations

Abstract The development of a bioethanol steam reforming system (FBSR) is considered as a means of distributing energy using PEM fuel cells. Small-scale solar collectors (collection areas on the order of several m 2 ) are installed in a house as a method for applying the FBSR. However, the temperature distribution of a reforming catalyst fluctuates under conditions of unstable solar insolation. Therefore, heat transfer analysis applied in reforming the catalyst layer of the reactor and the temperature distribution and transient response characteristics of the gas composition of the process were investigated. As a case study, meteorological data for representative days in March and August in Sapporo, Japan were recorded, and the hydrogen production speed, power generation output and amount of electricity purchased were analyzed. The results showed that although fluctuations in solar insolation affected the efficiency of the FBSR, the average efficiency of each representative day exceeded 40%. By installing two solar collectors, each with a collection area of 1 m 2 , 21–25% of the average power demand of an individual house can be supplied.

Autocatalytic water vapor production as a source of large mixing ratios within the middle to upper mesosphere

Different measurements have shown that large water vapor mixing ratios occur in the upper mesosphere in high‐latitude summer just under conditions of strongest solar insolation where photolysis should effectively reduce its value. The analysis of this finding by means of a high‐resolution one‐dimensional model supplies evidence that water vapor is autocatalytically formed below a crossover height of about 65 km and destroyed by photolysis above this altitude. We found three catalytic cycles of water vapor formation from the molecular hydrogen reservoir. Hydrogen radicals, resulting for the most part from water vapor by photolysis and oxidation by O(1D), act as catalysts. A great number of the hydrogen radicals return to water vapor, particularly under the condition of small atomic hydrogen concentration decreasing strongly with decreasing height. In the upper domain under the condition of large atomic hydrogen concentrations the formation of molecular hydrogen will be favored. Favorable conditions for large water vapor mixing ratios at high altitudes are given by an accelerated upward vertical wind. Below the crossover level the vertical wind should be weak so that H2 and CH4 have sufficient time to oxidize into H2O, a very slow process. Above this level, however, the vertical wind should be strong in order to lift the air, enriched with H2O, as quickly as possible to greater heights before the dissociation has an effective impact on the H2O distribution. Such accelerated upward vertical winds are typical of the mesosphere under certain seasonally latitudinal conditions. Calculations by means of our three‐dimensional model COMMA‐IAP yield seasonal‐latitudinal patterns and variations approximately comparable with those of the HALOE observations. In the paper we discuss the chemical background and the interplay between dynamics and chemistry in more detail.

Experimental investigation of a box type solar cooker employing a non-tracking concentrator

The present work aims at development of a box type solar cooker utilizing non-tracking concentrator optics to enhance the solar energy availability in the box of the cooker for efficient cooking. A laboratory model of a box type solar cooker employing a non-tracking concentrator has been designed and fabricated, and its thermal performance has been investigated experimentally. The concentrator, consisting of two planar reflectors suitably positioned in an east-west configuration on an inclined framework, is mounted on the box of the cooker to reflect incident solar radiation on the base absorber of the cooker. The design angle of inclination of the framework is taken equal to the latitude of the location and it is adjusted seasonally. The thermal performance of the experimental solar cooker has also been compared with that of a conventional box type solar cooker whose dimensions and make are identical to the box used with the former and which was also tested simultaneously under similar solar insolation and ambient conditions. The experimental results obtained show that the concentrator solar cooker provides a stagnation temperature 15-22 °C higher than that of the conventional box type solar cooker using a booster mirror. It is also observed that the boiling point of water with the concentrator cooker is reached faster, by 50-55 min, than with the conventional box type cooker using a booster mirror. Thus, the solar cooker utilizing non-tracking reflectors provides increased heat collection and faster cooking compared to the conventional box type cooker. The results of the tests conducted have been analyzed and discussed.

Marine boundary layer peroxy radical chemistry during the AEROSOLS99 campaign: Measurements and analysis

During the AEROSOLS99 cruise over the Atlantic and Southern Indian Oceans, peroxy radicals (RO2* = HO2 + ΣRO2, where R is an organic group) were continuously measured. Regular diurnal variations were observed with maximum mixing ratios of 30 to 55 parts per trillion by volume around noon. The latitudinal distribution of RO2* over the ocean seems to remain uniform under similar conditions of solar insolation. The composition of the marine boundary layer reflects long‐range transport of air from the African continent. The influence of biomass burning over remote areas of the marine boundary layer is confirmed, although the atmosphere over the Southern Hemisphere was often pristine, with rapid destruction of ozone observed during the daylight hours. Observed RO2* concentrations are in reasonable agreement with box model calculations, but cannot account for the highest diurnal variations of ozone observed. Possible explanations include halogen chemistry and nocturnal entrainment of O3 from the layers above, but available data cannot readily determine their relative contributions.

Role of orbital forcing in east Asian monsoon climates during the last 350 kyr: Evidence from terrestrial and marine climate proxies from core RC14‐99

Proxy records of northeast Asian precipitation (marine pollen) and northwest Pacific sea surface temperatures (marine fauna) contain concentrations of variance (frequency peaks) coincident with those of orbital variations (eccentricity, obliquity, and precession). Time series of these monitors of various components of the east Asian monsoon system are coherent with changing solar insolation and climate boundary conditions (ice volume, snow cover, albedo) at 41‐ and 23‐kyr frequencies. Winter sea surface temperature (WSST) maxima are in phase with global ice volume minima at all three Milankovitch frequencies (100‐, 41‐, and 23‐kyr periods). WSST maxima are also linearly related to summer insolation at 30°N, lagging radiation maxima by ∼55° (∼3.5 kyr) across the precessional frequency band (23‐kyr period). Our east Asian monsoon rainfall indicator (% Cryptomeria) reaches highest values immediately following summer insolation maxima during periods of low ice volume (interglacials). Across the eccentricity frequency band (100‐kyr period), % Cryptomeria maxima are in phase with ice volume minima. At the higher frequency of orbital precession, monsoon rainfall lags both summer radiation maxima (∼125°; ∼8 kyr) and ice volume minima (∼60°; ∼3.8 kyr). Whereas much of the variation in northwest Pacific WSST can be attributed to summer radiation forcing and changes in global climate, mechanisms driving east Asian monsoon precipitation are more complex, involving other (possibly internal) factors.

Prospects and limitations of solar energy utilization in developing countries

Abstract The effects of prospective uses of direct solar energy for power production, saline-water distillation, refrigeration and air conditioning, water heating, crop drying, etc, on the prosperity of the developing countries are discussed. A “solar home” of the 21st Century fulfilling all its energy requirements from the sun is visualized. Finally the difficulties in the way of solar-energy utilization due to the economic limitations as compared with conventional fuels are analyzed and presented in detail. The results are presented in a graphical form for finding the solar collector area required for a specific application of solar energy under various conditions of solar insolation and solar machine efficiencies and to assess the economic feasibility of solar-energy utilization for different applications when the costs of fuel, solar collector, and machine fabrication materials are known.