Shape Optimization For Parabolic Troughs Working In Non-Ideal Conditions

AbstractThe aim to realize more efficient solar concentrators, improves the research on the best configuration for the mirror surfaces. The optical behavior of a parabolic trough collector is investigated depending on its particular shape outside the ideal conditions. A 2D ray-tracing model of the real systems was realised taking into account a reference value for the solar radiation and different misalignment errors between the light beams and the mirrors axis.The computational analysis shows the relationship among the collection performance and the main geometrical parameters; different boundary conditions bring to consider different optimal configurations for the concentrator shape. Generally for medium concentration levels (50-150x) and non-ideal settings the more efficient parabolas are not characterized by a rim angle equal to 90°, which is the theoretical best value.Among the studied cases, it is interesting to note that a possible working condition for the PT system corresponds to a light beam scattering of 0.5° and a tracking misalignment of 0.2°.With these constrains, imposing high optical performance requirements, a maximum concentration ratio near to 60 can be reached with rim angle values of about 114°

Technique for Outdoor Test on Concentrating Photovoltaic Cells

Outdoor experimentation of solar cells is essential to maximize their performance and to assess utilization requirements and limits. More generally tests with direct exposure to the sun are useful to understand the behavior of components and new materials for solar applications in real working conditions. Insolation and ambient factors are uncontrollable but can be monitored to know the environmental situation of the solar exposure experiment. A parallel characterization of the photocells can be performed in laboratory under controllable and reproducible conditions. A methodology to execute solar exposure tests is proposed and practically applied on photovoltaic cells for a solar cogeneration system. The cells are measured with concentrated solar light obtained utilizing a large Fresnel lens mounted on a sun tracker. Outdoor measurements monitor the effects of the exposure of two multijunction photovoltaic cells to focused sunlight. The main result is the continuous acquisition of the V-I (voltage-current) curve for the cells in different conditions of solar concentration and temperature of exercise to assess their behavior. The research investigates electrical power extracted, efficiency, temperatures reached, and possible damages of the photovoltaic cell

Impact of a multidisciplinary management team on clinical outcome in ICU patients affected by Gram-negative bloodstream infections: a pre-post quasi-experimental study

Background: Bloodstream infections (BSIs) by Gram-negative pathogens play a major role in intensive care patients, both in terms of prevalence and severity, especially if multi-drug resistant pathogens are involved. Early appropriate antibiotic therapy is therefore a cornerstone in the management of these patients, and growing evidence shows that implementation of a multidisciplinary team may improve patients' outcomes. Our aim was to evaluate the clinical and microbiological impact of the application of a multidisciplinary team on critically ill patients. Methods: Pre-post study enrolling critically ill patients with Gram negative bloodstream infection in intensive care unit. In the pre-intervention phase (from January until December 2018) patients were managed with infectious disease consultation on demand, in the post-intervention phase (from January until December 2022) patients were managed with a daily evaluation by a multidisciplinary team composed of intensivist, infectious disease physician, clinical pharmacologist and microbiologist. Results: Overall, 135 patients were enrolled during the study period, of them 67 (49.6%) in the pre-intervention phase and 68 (50.4%) in the post-intervention phase. Median age was 67 (58-75) years, sex male was 31.9%. Septic shock, the need for continuous renal replacement therapy and mechanical ventilation at BSI onset were similar in both groups, no difference of multidrug-resistant organisms (MDRO) prevalence was observed. In the post-phase, empirical administration of carbapenems decreased significantly (40.3% vs. 62.7%, p = 0.02) with an increase of appropriate empirical therapy (86.9% vs. 55.2%, p < 0.001) and a decrease of overall antibiotic treatment (12 vs. 16 days, p < 0.001). Despite no differences in delta SOFA and all-cause 30-day mortality, a significant decrease in microbiological failure (10.3% vs. 29.9%, p = 0.005) and a new-onset 30-day MDRO colonization (8.3% vs. 36.6%, p < 0.001) in the post-phase was reported. At multivariable analysis adjusted for main covariates, the institution of a multidisciplinary management team (MMT) was found to be protective both for new MDRO colonization [OR 0.17, 95%CI(0.05-0.67)] and microbiological failure [OR 0.37, 95%CI (0.14-0.98)]. Conclusions: The institution of a MMT allowed for an optimization of antimicrobial treatments, reflecting to a significant decrease in new MDRO colonization and microbiological failure among critically ill patients

Electroluminescence Test to Investigate the Humidity Effect on Solar Cells Operation

The electroluminescence test is an experiment typically used to verify the behavior of the photovoltaic cell and to qualitatively check its integrity. It works by operating the photovoltaic cell as a diode polarized directly: the cells that light up in a module indicate how many of them work. This test provides an estimate of the maximum performance of the entire photovoltaic module. A qualitative inspection was performed by electroluminescence tests on 48 modules of photovoltaic cells. They had already been installed on a small-size concentration solar plant before the test and some modules had reached a lower level of performance than expected. A first electroluminescence test was performed, which showed that only 61.5% of the photocells worked. Since there were visible signs of humidity within the various modules, some of the inoperative modules underwent a dehumidification treatment in a climatic chamber. A second electroluminescence test showed that the percentage of functioning cells had increased to 66.3% after the drying treatment