Energy and exergy analysis of photovoltaic/thermal integrated with a solar greenhouse

In this paper, an attempt has been made to validate the thermal model with experimental results of a typical day August, 25, 2006 for clear weather condition of New Delhi. An energy and exergy analysis for the prediction of performance of a photovoltaic/thermal (PV/T) collector integrated with a greenhouse at I.I.T, Delhi, India has been carried out. The analysis is based on quasi-steady state condition. Experiments have been conducted extensively during period from June 2006 to May 2007, for annual performance. Numerical computation has been carried out for a typical day only for validation. It is observed that the theoretical value of solar cell, tedlar back surface and greenhouse room air temperatures is approximately equivalent to the experimental values. The predicted and measured values of solar cell, tedlar back surface and greenhouse air temperatures have been verified in terms of root mean square of percent deviation (7.05–17.58%) as well as correlation coefficient (0.95–0.97) and both exhibit fair agreement. Exergy analysis calculations of the PV/T integrated greenhouse system show an exergy efficiency level of approximately 4%.     

Green synthesis of copper sulfide (CuS) nanostructures for heterojunction diode applications

Copper sulfide (CuS) rod shaped nanostructures with an average length 8 to 10 nm are synthesized through green chemical route using biodegradable starch as a capping agent under a nitrogen environment. Owing to the presence of a large number of glucose units linked by glycosidic bonds, starch can cap copper sulfide (CuS) nanoparticles. The preparation of CuS under nitrogen atmosphere produces fine quality CuS nanostructures by minimizing oxidation. XRD pattern reveals pure hexagonal covellite type CuS nanostructure with prime diffraction planes along (101), (102), (103), (006), (008), and (110) directions. The lattice parameters estimated as a?=?3.790 Å and c?=?16.51 Å. HRTEM studies show a well distribution of CuS nanorods. It shows prominent d-value of 0.28 nm corresponding to (103) hexagonal plane of CuS. The optical absorption extended up to 364 nm which is fairly blue shifted over bulk owing to the quantum confinement brought by starch. The photoluminescence emission is observed at 525 nm. The I–V measurements in planar geometry exhibit the linearity that reveals the ohmic behavior of carrier transport in CuS nanostructures. CuS nanostructures have been successfully used as effective p-type layer to fabricate sandwiched heterojunction devices with zinc chalcogenides (ZnO/ZnS and ZnS/ZnO) core/shell nanocomposites. The p-CuS/n-(zinc chalcogenides) heterojunction devices show good diode characteristics with an increase of ideality factor that may be attributed to surface defects and inhomogeneity in the barrier height. The photodetector also exhibits promising characteristics in terms of responsivity and quantum efficiency which are significant corresponding to material properties.

     

Prediction and optimization of nanoclusters-based thermal conductivity of nanofluids: Application of Box–Behnken design (BBD)

The existing models to predict the thermal conductivity of nanofluids are based on single particle diameter, whereas, in actual solutions, nanoparticles mostly exist in a cluster form. Experiments are carried out to observe the effects of various surfactants on stability, nanocluster formation, and thermal conductivity of Al₂O₃–H₂O nanofluid, which is found to be improved considerably with SDS surfactant. The prolonged sonication was not adequate to break the clusters of Al₂O₃ nanoparticles, into an average size of less than 163 nm, indicating the tendency of Al₂O₃ nanoparticles to remain in the form of clusters instead of individual nanoparticles of primary size of 20 nm. Response surface methodology has been employed to design and optimize the experimental strategy by taking volumetric concentration, temperature, and surfactant amount as the contributing factors. The developed model has been validated against the experimental data and the existing models with an accuracy level of ± 8% in the former case. Analysis reveals about the formation of nanoclusters and enhancement in thermal conductivity. The results confirmed that the model can predict thermal conductivity enhancement with an accuracy level of R square value of the order of 0.9766.     

Inorganic-Based Printed Thermoelectric Materials and Devices

One of the simplest ways to generate electric power from waste heat is thermoelectric (TE) energy conversion. So far, most of the research on thermoelectrics has focused on inorganic bulk TE materials and their device applications. However, high production costs per power output and limited shape conformity hinder applications of state-of-the-art thermoelectric devices (TEDs). In recent years, printed thermoelectrics has emerged as an exciting pathway for their potential in the production of low-cost shape-conformable TEDs. Although several inorganic bulk TE materials with high performance are successfully developed, achieving high performance in inorganic-based printed TE materials is still a challenge. Nevertheless, significant progress has been made in printed thermoelectrics in recent years. In this review article, it is started with an introduction signifying the importance of printed thermoelectrics followed by a discussion of theoretical concepts of thermoelectricity, from fundamental transport phenomena to device efficiency. Afterward, the general process of inorganic TE ink formulation is summarized, and the current development of the inorganic and hybrid inks with the mention of their TE properties and their influencing factors is elaborated. In the end, TEDs with different architecture and geometries are highlighted by documenting their performance and fabrication techniques.     

Facile synthesis of asymmetric patchy Janus Ag/Cu particles and study of their antifungal activity

Asymmetric patchy Ag/Cu Janus nanoparticles (NPs) were synthesized via a “seed-mediated” approach. This is the first report of synthesis of nanometer sized metal-based Janus NPs without using complicated methods. Selective adsorption of the surfactant onto the seed NPs leads to the formation of Janus type structure. Subsequently the reduction potential of Ag⁺/Ag⁰ and Cu²⁺/Cu⁰ systems directs the formation of the “patch”. The patchy Janus NPs show significant antifungal activity towards a potent rice pathogen thus offering the prospect of future application in crop protection.     

Physicochemical Characterization of Interaction of Ibuprofen by Solid-State Milling with Aluminum Hydroxide

This present study is a preliminary exploration of the affinity between a carboxylic model drug ibuprofen and aluminum hydroxide. Ibuprofen was comilled with aluminum hydroxide in different weight ratios in the solid state and was characterized by scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and in vitro dissolution studies. XRD and SEM studies indicated complete interaction of ibuprofen with aluminum hydroxide and complete amorphization of aluminum hydroxide–ibuprofen complexed salt as well, on comilling with aluminum hydroxide at 1:2 ratio. FTIR data showed the disappearance of acid carbonyl peak with the appearance and the corresponding increase in absorbance of new signal at 1,682 cm^?1 in the 1:1 and 1:2 ibuprofen–aluminum hydroxide-comilled powder. The accompanied increase in the absorbance of carboxylate peak in the ibuprofen–aluminum hydroxide physical mixture, and 1:0.1, 1:0.5, 1:1, and 1:2 (IBA_pm, and IB₁A_0.1, IB₁A_0.5, IB₁A₁, and IB₁A₂, respectively) comilled powder indicated an acid–base reaction between ibuprofen and aluminum hydroxide. On storage at 40°C and 75% relative humidity (RH) for 10 weeks, XRD study showed the absence of reversion to the crystalline state and FTIR data revealed continued increase of new signal at 1,682 cm^?1 relative to carboxylic acid peak and no reappearance of carboxylic acid peak. In vitro dissolution studies revealed that the percent release of ibuprofen from the aluminum hydroxide-comilled powder is in the following order: IB₁A₂ < IB₁A₁ < ibuprofen crystal < ibuprofen milled alone < IB₁A_0.1 < IB₁A_0.5. Aluminum metal cation might have interacted to form a complex through the carboxyl and carbonyl groups of ibuprofen. Improved dissolution of drug associated with IB₁A_0.1 and IB₁A_0.5 is because of the absence of a new signal at 1,682 cm^?1 and improved amorphization of the drug to some extent. Dissolution of drug affected in IB₁A₂ and IB₁A₁ may be because of the insoluble stable complex formation.     

Enhanced photovoltaic performance of a dye sensitized solar cell with Cu/N Co-doped TiO<Subscript>2</Subscript> nanoparticles

Pure and Copper/Nitrogen (Cu/N)-codoped TiO₂ photoanodes with various Cu concentrations are prepared via sol–gel route for the photoanode application in dye-sensitized solar cells (DSSCs). All the prepared samples are characterized by X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), UV–Vis spectroscopy (UV–VIS) and Electrochemical Impedance Spectroscopy (EIS). Addition of suitable amount of Cu and N content in TiO₂ can alter its optical and electrical properties by extending absorption in the visible region and band gap reduction. The results show that some of the Ti sites are replaced by Cu atoms while O sites are occupied by N atoms. Upon adequate addition of Cu/N could lead to smaller particle size, higher specific surface area, increased dye adsorption and retarded charge carrier recombination. A significant improvement in the power conversion efficiency is observed in case of optimized 0.3 mol% Cu/N-doped TiO₂ nanoparticles (NPs) based DSSC. This optimized 0.3 mol% Cu/N-doped photoanode accomplished a best power conversion efficiency of 11.70% with a short circuit current density of 23.41 mA cm^?2 which is 41% higher than that of the pure TiO₂ photoanode based DSSC (6.82%).     

Fabrication and characterization of carbon fiber reinforced clay/epoxy composite

In this study, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and flexural tests were performed on unfilled, 1, 2, 3, and 4 wt% clay filled SC-15 epoxy to identify the effect of clay weight fraction on thermal and mechanical properties of the epoxy matrix. The flexural results indicate that 2.0 wt% clay filled epoxy showed the highest improvement in flexural strength. DMA studies also revealed that 2.0 wt% system exhibit the highest storage modulus and T _g as compared to neat and other weight fraction. However, TGA results show that thermal stability of composite is insensitive to the clay content. Based on these results, the nanophased epoxy with 2 wt% clay was then utilized in a vacuum assisted resin transfer molding set up with carbon fabric to fabricate laminated composites. The effectiveness of clay addition on thermal and mechanical properties of composites has been evaluated by TGA, DMA, tensile, flexural, and fatigue test. 5 °C increase in glass transition temperature was found in nanocomposite, and the tensile and flexural strengths improved by 5.7 and 13.5 %, respectively as compared to the neat composite. The fatigue strength was also improved significantly. Based on the experimental result, a linear damage model combined with the Weibull distribution function has been established to describe static failure processing of neat and nanophased carbon/epoxy. The simulated stress–strain curves from the model are in good agreement with the test data. Simulated results show that damage processing of neat and nanophased carbon/epoxy described by bimodal Weibull distribution function.     

Measurement of 40k as an indicator of body potassium: implication for diabetes and other disease conditions

Potassium (K) content in 408 male workers of a rare earths processing plant was estimated using a shadow shield whole body counter. The average K content in the non-vegetarian and vegetarian group was found to be 1.5 g kg(-1) and 2.1 g kg(-1) respectively. The absorbed dose due to 40K is determined as 0.18 +/- 0.02 mGy. While the K content was found to be proportional to body build index, it is inversely proportional to slenderness. Body K was maximum in the middle aged group (35-45 y) and a minimum in younger and older persons. The correlation of potassium content with some disease patterns was also studied. Diabetes mellitus patients were observed to have low K content of 0.9 +/- 0.2 g kg(-1) and those who suffer from cardiovascular disorders were found to have high K content 2.7 +/- 0.3 g kg(-1). The studies showed that the depletion of body K content takes place a few years prior to the clinical detection of diabetes and it builds up a few years before the clinical detection of cardiovascular disorders. It is stressed that the medical information is preliminary as the number of subjects studied was not very large. Wider and in depth study by various groups can hopefully strengthen the observation.