Weak solar events

Soft X-ray solar bursts were investigated in the framework of the Interball—Tail Probe project by using an RF-15I-2 X-ray photometer. When studying microflares over the period from September to December 1995, weak bursts with intensities of less than 10^?8 W/m² were detected. All these data are confirmed by observations performed in the framework of the GOES project. The characteristics of solar microflares were determined, and the physical mechanism of weak solar events was considered. The distribution of microflares over their intensities was obtained. It is found that the distribution of solar flares over released energies do not obey a power law, and a lower limit is revealed in this distribution. This result is confirmed by the data obtained in the framework of the RHESSI project. Correlation between the daily average values of the maximum intensities of X-ray bursts of different classes of microflares and the daily average values of the thermal background of the solar corona is revealed.     

Hybrid solar cells

Historically, conventional solar cells were built from inorganic materials such as silicon. Although the efficiency of such conventional solar cells is high, very expensive materials and energy intensive processing techniques are required.Hybrid and photoelectrochemical (dye sensitized) solar cells have been the cheap alternatives for conventional silicon solar cells. A hybrid solar cell consists of a combination of both organic and inorganic materials therefore, combines the unique properties of inorganic semiconductors with the film forming properties of the conjugated polymers. Organic materials are inexpensive, easily processable and their functionality can be tailored by molecular design and chemical synthesis. On the other hand, inorganic semiconductors can be manufactured as nanoparticles and inorganic semiconductor nanoparticles offer the advantage of having high absorption coefficients and size tunability. By varying the size of the nanoparticles the bandgap can be tuned therefore the absorption range can be tailored.In this short review, we will focus on the concepts of organic/inorganic “hybrid” solar cells.     

A two-stage solar photobioreactor for cultivation of microalgae based on solar concentrators

A novel two-stage experimental photobioreactor (PBR) with a total volume of 450 L and based uniquely on solar concentrators—linear Fresnel lenses—has been constructed and tested. Daily courses of irradiance, and also its distribution inside cultivation tubes, were studied in two unit types. The supra-high irradiance units in the ‘roof’ achieved a maximum summer value above 6 mmol photon m⁻² s⁻¹, while irradiance in the vertical-facade units was lower than ‘ambient’. In model cultivations, cultures of the cyanobacterium Arthrospira platensis were cultivated at much higher solar irradiances than those usually recorded outdoors in summer, indicating that this organism is resilient to high-irradiance (photoinhibition). Starting from a biomass density of 0.5 g L⁻¹ at optimum temperature, the cultures grew exponentially. A two-stage cultivation process of the green microalga Haematococcus pluvialis was investigated with respect to correlations between photochemical activities and astaxanthin production. The culture was first grown in low-irradiance units, and then exposed to supra-high irradiance when the rate of astaxanthin production was 30–50% higher than in the culture exposed to ‘ambient’ irradiance. Within 4 days, the astaxanthin content reached 3% of dry weight, whereas under ambient irradiance the astaxanthin content was 25% lower.     

Carbon nanotube solar cells

We present proof-of-concept all-carbon solar cells. They are made of a photoactive side of predominantly semiconducting nanotubes for photoconversion and a counter electrode made of a natural mixture of carbon nanotubes or graphite, connected by a liquid electrolyte through a redox reaction. The cells do not require rare source materials such as In or Pt, nor high-grade semiconductor processing equipment, do not rely on dye for photoconversion and therefore do not bleach, and are easy to fabricate using a spray-paint technique. We observe that cells with a lower concentration of carbon nanotubes on the active semiconducting electrode perform better than cells with a higher concentration of nanotubes. This effect is contrary to the expectation that a larger number of nanotubes would lead to more photoconversion and therefore more power generation. We attribute this to the presence of metallic nanotubes that provide a short for photo-excited electrons, bypassing the load. We demonstrate optimization strategies that improve cell efficiency by orders of magnitude. Once it is possible to make semiconducting-only carbon nanotube films, that may provide the greatest efficiency improvement.     

Estimation of solar radiation environment

This paper derives a model,from a review of published literature and U.S. Army technical reports, for calculating the total heat imposed per unit surface area by direct sunlight. Factors considered include solar zenith angle, water vapor and dust content of the air and terrestrial elevation. Unlike the usual meteorological measurement of total hemispheric radiation, calculated values are obtained for direct solar intensity and also diffuse sky radiation, thus allowing separation of the solar radiation impinging on horizontal surfaces from that on vertical or perpendicular surfaces. Representative calculated values for 9 major climatic regions of the world agree with the limited comparable measured values available.

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Zusammenfassung Diese Arbeit beschreibt mittels eines Rückblicks auf die veröffentlichte Literatur und die Technischen Berichte der U.S. Army ein Modell für die Berechnung der totalen Wärmemenge, die einer Oberflächeneinheit durch die direkte Sonnenstrahlung zugeführt wird. Die betrachteten Faktoren schliessen den Einfallswinkel, den Wasserdampf, den Staubgehalt der Luft sowie die Höhenlage ein.Im Gegensatz zur üblichen meteorologischen Messung der totalen hemisphärischen Strahlung erhält man so berechnete Werte für die direkte Strahlungsintensität und auch für die diffuse Himmelstrahlung, so dass damit die Strahlung auf horizontale Flächen von der auf vertikale oder geneigte Flächen getrennt werden kann. Repräsentative berechnete Werte für 6 Hauptklimagebiete der Erde stimmen mit den wenigen vergleichbaren Werten überein, die verfügbar sind.

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Resume Dans le présent mémoire, on décrit un modèle permettant de calculer la quantité totale de chaleur reçue par une surface unité par suite du rayonnement solaire direct. Pour ce faire, on a passé en revue les travaux publiés en la matiére et les rapports techniques de l'armée des Etats-Unis. Les éléments considérés sont:l'angle d'incidence, la vapeur d'eau, la teneur en poussières de l'atmosphère et l'altitude. Au contraire des mesures météologiques usuelles indiquant le rayonnement total reçu par un hémisphère on obtient ici des valeurs calculées pour l'intensité du rayonnement direct ainsi que pour le rayonnement diffus. On peut ainsi distinguer le rayonnement tombant sur une surface horizontale de celui atteignant une surface verticale ou ayant une inclinaison quelconque. Des valeurs représentatives calculées pour 6 zones climatiques de la terre correspondent bien aux quelques valeurs comparatives dont on dispose.

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Dr.Roller was a Senior Postdoctoral Visiting Research Associate of the National Academy of Sciences-National Research Council on leave of absence from the Department of Agricultural Engineering, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio.     

Thermal self-focusing during solar flares

By solving a nonlinear equation for a heat source with a power proportional to Т ^β (β > 1), it is shown that heat localization in the transverse cross section of a magnetic tube with a classical thermal conductivity occurs in the blowup regime in the form of microstructures—temperature background cells bounded by hot walls with a spatial scale of <100 m. The reduction in the integral X-ray emissivity observed on board of spacecrafts in the early stage of the flare is attributed to thermal self-focusing, i.e., a decrease in the factor of filling of the flare volume with hot plasma due to the narrowing of the hot walls of the microstructure.     

Hemolysis and the solar spectrum

Summary The curves of Fig. 1 show that the spectral distribution of efficiency of radiation in decreasing the stability of red blood corpuscles corresponds very closely to the spectral distribution of the power of oxyhemoglobin to absorb radiation. This correspondence clearly indicates that it is a chemical change in the hemoglobin which is responsible for the decrease of resistance of the corpuscles and hemolysis produced by light. In other words, hemolysis is not due to some change in the membrane of the red corpuscle, which is colorless, but to a chemical change in the hemoglobin; that is, in one of the components of the principal compounds constituting the protoplasm of erythrocytes (4). With 1 Text-figure     

Environmental impact of thin-film GaInP/GaAs and multicrystalline silicon solar modules produced with solar electricity

Background, aim, and scope  The environmental burden of photovoltaic (PV) solar modules is currently largely determined by the cumulative input of fossil energy used for module production. However, with an increased focus on limiting the emission of CO₂ coming from fossil fuels, it is expected that renewable resources, including photovoltaics, may well become more important in producing electricity. A comparison of the environmental impacts of PV modules in case their life cycle is based on the use of PV electricity in contrast to conventional electricity can elucidate potential environmental drawbacks in an early stage of development of a solar-based economy. The goal of this paper is to show for ten impact categories the environmental consequences of replacing fossil electricity with solar electricity into the life cycle of two types of PV modules. Materials and methods  Using life cycle assessment (LCA), we evaluated the environmental impacts of two types of PV modules: a thin-film GaInP/GaAs tandem module and a multicrystalline silicon (multi-Si) module. For each of the modules, the total amount of fossil electricity required in the life cycle of the module was substituted with electricity that is generated by a corresponding PV module. The environmental impacts of the modules on the midpoint level were compared with those of the same modules in case their life cycle is based on the use of conventional electricity. The environmental impacts were assessed for Western European circumstances with an annual solar irradiation of 1000 kWh/m². For the GaInP/GaAs module, the environmental impacts of individual production steps were also analysed. Results  Environmental burdens decreased when PV electricity was applied in the life cycle of the two PV modules. The impact score reductions of the GaInP/GaAs module were up to a factor of 4.9 (global warming). The impact score reductions found for the multi-Si module were up to a factor of 2.5 (abiotic depletion and global warming). Reductions of the toxicity scores of both module types were smaller or negligible. This is caused by a decreased use of fossil fuels, on the one hand, and an increased consumption of materials for the production of the additional solar modules used for generating the required PV electricity on the other. Overall, the impact scores of the GaInP/GaAs module were reduced more than the corresponding scores of the multi-Si module. The contribution analysis of the GaInP/GaAs module production steps indicated that for global warming, the cell growth process is dominant for supply with conventional electricity, while for the solar scenario, the frame becomes dominant. Regarding freshwater aquatic ecotoxicity scores associated with the life cycle of the GaInP/GaAs module, the cell growth process is dominant for supply with conventional electricity, while the reactor system for the cell growth with the associated gas scrubbing system is dominant for the solar scenario. Discussion  There are uncertainties regarding the calculated environmental impact scores. This paper describes uncertainties associated with the used economic allocation method, and uncertainties because of missing life cycle inventory data. For the GaInP/GaAs module, it was found that the global warming impact scores range from −66% to +41%, and the freshwater aquatic ecotoxicity scores (for an infinite time horizon) range from −40% to +300% compared to the default estimates. For both impact categories, the choices associated with the allocation of gallium, with the electricity mix, with the conversion efficiency of the commercially produced GaInP/GaAs cells, and with the yield of the cell growth process are most influential. For freshwater aquatic ecotoxicity, the uncertainty concerning the lifetime of the reactor system for the GaInP/GaAs cell growth process and the gas scrubbing system is particularly relevant. Conclusions  Use of PV electricity instead of fossil electricity significantly reduces the environmental burdens of the GaInP/GaAs and the multi-Si module. The reductions of the toxicity scores, however, are smaller or negligible. Toxicity impacts of the GaInP/GaAs cells can be reduced by improvement of the yield of the cell growth process, a reduced energy demand in the cell growth process, reduction of the amount of stainless steel in the cell growth reactor system and the gas scrubbing system, and a longer lifetime of these systems. Recommendations and perspectives  Because the greenhouse gas emissions associated with the production of fossil-fuel-based electricity have an important share in global warming on a world-wide scale, switching to a more extensive use of solar power is helpful to comply with the present international legislation on the area of global warming reduction. As reductions in toxicity impact scores are smaller or negligible when fossil electricity is replaced by PV electricity, it is desirable to give specific attention to the processes which dominantly contribute to these impact categories. Furthermore, in this study, a shift in ranking of several environmental impacts of the modules has been found when PV electricity is used instead of fossil electricity. The results of a comparative LCA can thus be dependent of the electricity mix used in the life cycles of the assessed products. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Acid-base solar biobattery exploiting water plants

A biobattery of a new type in which pH difference between two media serves as a source of free energy is described. The ability of some algae and other water plants to change markedly the pH of their surroundings according to the light conditions can be used to maintain two solutions at widely differing pH values. Electrical energy may be obtained from this source as a by-product to biomass production.     

Utility-scale solar impacts to volant wildlife

To reduce carbon emissions from fossil fuel combustion, United States government agencies, including those in California, initiated aggressive programs to hasten development of utility-scale solar energy. Much of California's early development of solar energy occurred in deserts and annual grasslands, much of it on public land. Measurement of solar energy's impacts to wildlife has been limited to mortality caused by features of solar facilities, and has yet to include impacts from habitat loss and energy transmission. To estimate species-specific bird and bat fatality rates and statewide mortality, I reviewed reports of fatality monitoring from 1982 to 2018 at 14 projects, which varied in duration, level of sampling, search interval, search method, and carcass detection trials. Because most monitors performed carcass detection trials using species of birds whose members were larger than birds and bats found as fatalities, I bridged the monitors' onsite trial results to offsite trial results based on the same methods but which also measured detection probabilities across the full range of body sizes of species represented by fatalities. This bridge preserved the project site's effects on detection probabilities while more fully adjusting for the effects of body size. My fatality estimates consistently exceeded those reported. Projected to California's installed capacity of 1,948.8 MW of solar thermal and 12,220 MW of photovoltaic (PV) panels in 2020 (14,168.8 MW total), reported estimates would support an annual statewide fatality estimate of 37,546 birds and 207 bats, whereas I estimated fatalities of 267,732 birds and 11,418 bats. Fatalities/MW/year averaged 11.61 birds and 0.06 bats at PV projects and 64.61 birds and 5.49 bats at solar thermal projects. Fatalities/km/year averaged 113.16 birds and zero bats at generation tie-ins, and 14.44 birds and 2.56 bats along perimeter fences. Bird fatality rates averaged 3 times higher at PV projects searched by foot rather than car. They were usually biased low by insufficient monitoring duration and by the 22% of fatalities that monitors could not identify to species. I estimated that construction grading for solar projects removed habitat that otherwise would have supported nearly 300,000 birds/year. I recommend that utility-scale solar energy development be slowed to improve project decision-making, impacts assessment, fatality monitoring, mitigation efficacy, and oversight.     

微生物太阳能燃料电池的研究进展

摘要:能源危机已经成为阻碍世界发展的主要问题之一,微生物燃料电池的出现为能源危机提供了新的解决途径。将植物和微藻等光合生物与微生物燃料电池整合为微生物太阳能燃料电池(MSCs),能够实现将太阳能转化为电能。微生物太阳能燃料电池不仅能够实现电能持续稳定的产生,而且在污水处理,生物柴油加工以及中间代谢物生产等方面具有广阔的应用前景。本文从光合生物在微生物燃料电池中的作用的角度出发,在参考大量文献的基础上对微生物太阳能电池进行较为全面的综述,并评述其中的优点及不足之处,最后对微生物燃料电池面临的挑战及研究需求做简要分析。旨在为未来微生物太阳能燃料电池的实际应用提供参考。     

Industrial microbiology of solar salt production

Solar salterns can be modeled as giant outdoor chemostats, much like a series of dams on a slow-moving river. Microorganisms and their products play an essential, but sometimes uncharacterized, role in salt production in these ponds, from seawater salinity up through NaCl saturation. They may physically affect the evaporation process and their by-products may chemically modify or bind with dissolved ions. Many solar salt facilities engage microbiologists to establish monitoring programs for analyses of nutrients, standing crop and associated biological variables in the ponds. Other solar salt companies engage microbiologists only when there are “crises” in the ponds that interfere with salt production. Journal of Industrial Microbiology & Biotechnology (2002) 28, 42–47 DOI: 10.1038/sj/jim/7000173 Received 20 May 2001/ Accepted in revised form 13 June 2001     

Periodic thermomagnetic structures in solar plasma

Stationary solutions in the form of small-scale periodic cells in a plane perpendicular to the magnetic field are obtained in the framework of two-fluid magnetohydrodynamics. The solutions are established as a result of the development of thermal instability and represent a superposition of standing temperature waves. In solving the problem, an expression is used for a generalized heat source (including heating and radiative cooling) that forms a temperature transition region between the chromosphere and corona.     

Chorioretinal temperature increases from solar observation

Chorioretinal temperature increases produced by solar observations are computed digitally. The spectral characteristics of solar radiation and the spectral transmittances of the atmosphere, atmospheric water vapor and ocular media are considered. Image spread is employed in all calculations. The calculations are executed for a variety of observation angles, and the effects of pupil diameter, fixed filters and optical instruments are predicted. Temperature increases are also computed for solar eclipse observations by the appropriate superposition of unobscured solar disk solutions.     

Sterilization of instruments in solar ovens

AIMS: The sterilization of instruments in rural health clinics in less developed countries is an increasing problem as chemical methods can no longer be recommended and fuel wood is becoming increasingly scarce. It seems obvious, therefore, to utilize solar energy for sterilization purposes. METHODS AND RESULTS: A solar oven was designed and manufactured using local materials and simple tools. It was tested by physical, chemical and microbiological methods and, after successful testing, installed in a rural clinic. The oven was able to generate temperatures above 180 degrees C. On days with direct sunlight the oven fulfilled the international recommendations for hot air sterilization. The chemical indicators, Browne's tubes type 3 and 5, also changed colour. It was difficult to reach the right value for the sterilization effect during months with a low sun position. A moveable oven, or two ovens, must be installed to solve this problem. CONCLUSIONS: The solar oven has proven to be a realistic method for the sterilization of instruments. SIGNIFICANCE AND IMPACT OF THE STUDY: The solar oven is easy to make and use. It saves fuel and can be used in most tropical areas.