We present strong arguments and experimental findings for the definition of a photovoltaic module accelerated ageing procedure for high irradiance and desert conditions to create a Desert Label for ...the particular Atacama Desert climatic conditions. A special focus on high ultraviolet solar radiation dosage in combination with either damp heat, salt mist or aggressive thermal cycling are presented. Indoor experimental results, strengthened by outdoor monitoring of sister mini-modules at the Atacama Desert, allowed selecting the appropriate ageing tests while exploring the reliability and durability of a wide range of module configurations, including various typical encapsulants, high efficiency cell technologies and module designs, for industrial applications.
•Some heterojunction solar cells are sensitive to UV light.•Good correlations between indoor UV ageing and outdoor results are reported.•Much higher UV dose than the IEC61215 are required for PV modules dedicated to Desert conditions.•No synergy have been detected between UV and moisture from indoor and outdoor results.•Severity 3 salt mist test do not damage our PV modules.
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•We propose a procedure for indoor soiling studies by using spin coating technique.•Dust samples were collected from PV modules installed in the Atacama Desert.•Homogeneous dust ...deposition was obtained within 25 s using spin coating technique.•Physicochemical characteristics of material allowed understanding the cementation.•As dust amount increased, light attenuation in the UV range became more significant.
Soiling affects the economic profitability of solar photovoltaic plants, reducing productivity of the photovoltaic modules and increasing maintenance costs. Typically, studies on the soiling impact on photovoltaic technologies conducted outdoors require long exposure times. This paper deals with a new methodology for accelerated indoor test. Dust samples from the Atacama Desert are used to study physicochemical aspects of local soiling and its effects in the performance of solar cells. The new methodology is based on spin-coating to deposit homogeneous soiling layers on photovoltaic glass. This technique allows different soil mixtures to be deposited, resulting in the desired surface dust densities. X-ray diffraction and scanning electron microscopy of samples with artificially indoor and naturally outdoor deposited dust revealed similar behavior. In both, gypsum was the soluble material supporting the cementation process. The external quantum efficiency of the solar cell under different soiling conditions allowed to evaluate its effect on the photogenerated current density (Jph) for different spectral ranges. As expected from other studies, the influence of soiling is higher in the ultraviolet spectral range than at other wavelengths. It is observed that as the amount of deposited soil increases, the Jph losses are higher in the ultraviolet spectral range than in the visible or infrared. Because of the reduction in current density, efficiency is affected as the surface dust density increases. For instance, the efficiency decreased by 66.5% for 1.37 mg/cm2.
Purpose
Prophylactic placement of endovascular balloon occlusion catheters has grown to be part of the surgical plans to control intraoperative hemorrhage in cases of abnormal placentation. We ...performed a systematic literature review to investigate the safety and effectiveness of the use of REBOA during cesarean delivery in pregnant woman with morbidly adherent placenta.
Methods
A systematic review was performed. Relevant case reports and nonrandomized studies were identified by the literature search in MEDLINE. We included studies involving pregnant woman with diagnosis of abnormal placentation who underwent cesarean delivery with REBOA placed for hemorrhage control. MINORS’ criteria were used to evaluate the risk of bias of included studies. A formal meta-analysis was not performed.
Results
Eight studies were included in cumulative results. These studies included a total of 392 patients. Overall, REBOA was deployed in 336 patients. Six studies reported the use of REBOA as an adjunct for prophylactic hemorrhage control in pregnant woman with diagnosis of morbidly adherent placenta undergoing elective cesarean delivery. In two studies, REBOA was deployed in patients already in established hemorrhagic shock at the moment of cesarean delivery. REBOA was deployed primarily by interventional radiologists; however, one study reported a surgeon as the REBOA provider. The results from our qualitative synthesis indicate that the use of REBOA during cesarean delivery resulted in less blood loss with a low rate complications occurrence.
Conclusion
REBOA is a feasible, safe, and effective means of prophylactic and remedial hemorrhage control in pregnant women with abnormal placentation undergoing cesarean delivery.
Crystalline silicon solar cells are currently the leading technology in the photovoltaic market with no great expectable change in the shares. The scientific community works on the further ...development and improvements of state-of-the-art as well as new solar cell materials. This paper reports on a chemical methodology for selective etching to study the metallization step in monocrystalline silicon solar cells. The object of study is a complete processed silicon solar cell which was cleaved via laser beam on the back side and broken per hand to obtain stripes of the size 15.6×1 cm². In the following a sequence of etching chemical solutions to selectively remove the components of the front side silver contact was applied. Scanning electron microscopy was used to investigate contact interface after each etching step. The silver finger, the glass and the silver crystallites grown in silicon could be removed. It came out that the silver crystallites preferably grow at the pyramid tips and edges of the textured wafer. A characterization with Energy Dispersive X-Ray Spectrometry was performed to quantify the components of the silver contact after each chemical etching step. While the weight percentage of silver reduced by more than 90% after an aqua regia treatment, it increased by 13% after hydrofluoric acid. Silver was practically eliminated after a second aqua regia bath. Similarly, the content of glass was also determined. The approach serves for interface investigations in semiconductor technology where screen printing approaches are used for the metallization.
The estimation of daily solar radiation is needed in many studies related to solar power plant placements. To optimize photovoltaic (PV) systems, their placement must be as efficient as possible in ...terms of the prevailing meteorological conditions. There are situations where radiation data are not available, as in the case of desert areas, suitable for the operation of PV systems. In this work, daily global solar radiation has been estimated in desert areas using Artificial Neural Networks (ANN), where the inputs used are daily minimum and maximum temperatures and extraterrestrial radiation. The ANN model is validated with data from deserts in Chile, Israel, Saudi Arabia, South Africa and Australia. The results show that the average Relative Root-Mean-Square Deviation (RRMSD) value is 13%, the average Relative Mean Bias Difference (RMBE) value is less than 4% and the average correlation coefficient (r) value is about 0.8.
•Daily global solar radiation has been estimated in desert areas.•Extreme daily temperatures were used as input of ANN for solar radiation estimation.•The best solar radiation estimation was in Chile with an RMSD of about 8%.•Radiation estimations in world's deserts presented an average RMSD value of 13%.
In this work we characterize height-selective emitters. The concept of a height-selective emitter is similar to the classical selective emitter but applied on a much smaller scale. Concretely, we ...masked textured wafers by a spin coating oxide. Scanning electron microscopy (SEM) analysis revealed that only the valleys between the tips of the pyramids are covered by the oxide while the tips are open. Thus, subsequent phosphorus diffusion leads to a highly doped emitter on the tips of the pyramids, and a lowly doped emitter at the sides and valleys in between. This was demonstrated by SEM measurements on cross section prepared samples. Further characterization consisted of IV, spectral response, and contact resistivity measurements as well as the determination of the silver crystallites’ distribution, both on height-selective and standard emitter cells with different emitter sheet resistances. In contrast to homogeneous emitter cells, height-selective emitter cells, although exhibiting a high macroscopical sheet resistance, could still be well contacted by standard silver pastes. Just a few silver crystallites at the tips of the pyramids allowed a good contact. Up to 110Ω/sq fill factors higher than 77.5% could be achieved. The last part of the characterization consisted of carrier lifetime measurements on standard and height-selective emitter samples with symmetric structures to determine the implied open circuit voltage, emitter saturation current density and effective lifetime to identify limiting factors such as emitter, front, and back surface recombination. These measurements demonstrated that height-selective emitters benefit from a lower recombination in the emitter allowing a higher open circuit voltage.
Chile is committed to the development of non-conventional renewable energies, so to create the necessary incentives, several laws has been issued. One of the most recent actions was the Net billing ...law, which seeks to promote the integration of renewable technologies in the distribution segment. Because Chile has chosen not to use subsidies, only cost-efficient technologies are incorporated in the market. The net billing law has not shown much impact so far, therefore further incentive mechanisms are under discussion. This paper reports on the integration scheme for residential photovoltaic generation within net billing and net metering context. Different options of photovoltaic plants are analyzed: a) self-consumption, b) self-consumption and feeding into the grid, c) self-consumption and storage. Discrimination of the best options has been determined based on the economic benefits of each alternative, which are determined by performing calculation of Net Actual Value (VAN). Growth rates for each of sizing options have been also determined and compared with the price of energy for the residential segment (BT1) in order to find the optimal choice. The results obtained show that for the existing market conditions in Chile and the net billing scheme the size of the photovoltaic plant in northern Chile should be about 1 kW. Furthermore, the option of using storage is not yet economically feasible.
Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients.The cornerstones in the management of ...complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance.The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria.An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs.
In order to confirm the existence of a height-selective emitter, we compared local doping profiles of such emitters with profiles of a standard homogeneous emitter. The concept of a height-selective ...emitter is based on the classical selective emitter but in a smaller scale. The pyramid tips are highly doped. The sides and valleys are lowly doped. The comparison of the doping profiles was addressed by using a high-spatial-resolution analysis method: scanning spreading resistance microscopy. The measurement was performed on fully produced cells with a height-selective emitter and a standard homogeneous emitter, both with random pyramid textured surfaces. We prepared samples from these cells and investigated the cross sections. A representative pyramid of each type of emitter was selected. We found that for height-selective emitters the surface concentration can strongly vary depending on the measured position of the selected pyramid. The tip of the pyramid is heavily doped, while the bottom is lowly doped. For standard cells with a homogeneous emitter, the doping profiles do not differ dramatically as for the sample with a height-selective emitter. We calculated the local sheet resistance by using the measured local emitter profiles and a doping-dependent mobility model for phosphorus-doped silicon.
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