Thermal performance evaluation of a solar air heater with and without thermal energy storage

This communication presents the experimental study and performance analysis of a solar air heater with and without phase change material (PCM) viz. paraffin wax and hytherm oil. There are three different arrangements viz. without PCM, with PCM and with hytherm oil to study the comparative performance of this experimental system. Inlet, outlet temperatures and radiation with respect to time have been recorded and found that the output temperature in case with thermal energy storage (TES) is higher than that of without TES, besides, the outlet temperature with paraffin wax is slightly greater than that of with hytherm oil. Also there is no energy gain in the evening in case of without TES but in case of with TES there is a heat gain for around 4 h in the evening which gives the backup for hot air for around four more hours which is the main advantage of this systems with TES. Based on the data, the efficiency of the system has been calculated and it is noted that the efficiency in the case of heat storage is higher than that of without TES, besides the efficiency in the case of the paraffin wax is slightly higher than that of the hytherm oil case.     

Energy,exergy and economic investigation of passive and active inclined solar still: experimental study

Journal of Thermal Analysis and Calorimetry - High pressure die casting is one of the leading casting processes in the modern industry. In the case of high pressure die casting, the melt is in...     

Impact of orientation and water depth on productivity of single-basin dual-slope solar still with Al2O3 and CuO nanoparticles

Journal of Thermal Analysis and Calorimetry - The thermal performance of solar still can be enhanced by means of nanoparticles. The core aim of the present work is to identify the influence of...     

Synthesis and thermal energy storage properties of a calcium-based room temperature phase change material for energy storage

Journal of Thermal Analysis and Calorimetry - In order to obtain a low-cost, high latent heat and thermostable phase change material with a phase change temperature between 18 and...     

Sustainable potable water production from conventional solar still during the winter season at Algerian dry areas: energy and exergy analysis

Journal of Thermal Analysis and Calorimetry - The Algeria Sahara suffers from the scarcity of drinking water. Solar distillation is one of the simplest and generally inexpensive techniques to solve...     

Effect of solvent and additives on the open-circuit voltage of ZnO-based dye-sensitized solar cells: a combined theoretical and experimental study

We have investigated the role of electrolyte composition, in terms of solvent and additive, on the open-circuit voltage (V(oc)) of ZnO-based dye-sensitized solar cells (DSSCs) using a combined experimental and theoretical approach. Calculations based on density functional theory (DFT) have been performed in order to describe the geometries and adsorption energies of various adsorbed solvents (nitromethane, acetonitrile and dimethylformamide) and p-tert-butylpyridine (TBP) (modeled by methylpyridine) on the ZnO (100) surface using a periodic approach. The densities of states (DOS) have been calculated and the energy position of the conduction band edge (CBE) has been evaluated for the different molecules adsorbed. The effect of the electrolyte composition on the standard redox potential of the iodide/triiodide redox couple has been experimentally determined. These two data values (CBE and standard redox potential) allowed us to determine the dependence of V(oc) on the electrolyte composition. The variations determined using this method were in good agreement with the measured V(oc) for cells made of electrodeposited ZnO films sensitized using D149 (indoline) dye. As in the case of TiO(2)-based cells, a correlation of V(oc) with the donor number of the adsorbed species was found. The present study clearly points out that both the CBE energy and the redox potential variation are important for explaining the experimentally observed changes in the V(oc) of DSSCs.     

Understanding electrochemical performance of Ni(OH)2 films: a study contributions to energy storage

Journal of Solid State Electrochemistry - Nanostructured Ni(OH)2 was grown on the surface of a Ti plate via electrodeposition method. Analytical methods were employed to characterize the structure,...     

Thermodynamic and thermal energy storage properties of a new medium-temperature phase change material

Journal of Thermal Analysis and Calorimetry - Phase change materials (PCMs) that can store the heat energy obtained from intermittent solar irradiation are very important for solar energy...     

Effective interaction energy of water dimer at room temperature: an experimental and theoretical study

Buffer-gas pressure broadening for the nu(1)+nu(3) band of H(2)O at 1.34-1.44 mum for a variety of buffer gases was investigated at room temperature using continuous-wave cavity ring-down spectroscopy. The effective interaction energy of water dimer under room temperature conditions was evaluated from the pressure broadening coefficients for rare gases using Permenter-Seaver's relation. Monte Carlo simulations were performed using ab initio molecular orbital calculations to evaluate the interaction energies for the water dimer at 300 K. In this theoretical calculation, the orientations of the two water molecules were statistically treated.     

Preparation and characterization of a novel form-stable phase change material for thermal energy storage

Journal of Thermal Analysis and Calorimetry - A series of novel polymeric form-stable phase change materials (FSPCMs) composed of poly(trimethylolpropane trimethacrylate-stearyl methacrylate) (PTS)...     

Solid-state graphene-based supercapacitor with high-density energy storage using ionic liquid gel electrolyte: electrochemical properties and performance in storing solar electricity

Journal of Solid State Electrochemistry - The electrochemical properties and high-density energy storage performance of graphene nano-platelet-based solid-state electrical double-layer...     

Effect of the inclination angles on thermal energy storage in a quadrantal cavity

A free-base tetra sodium meso-tetra (p-sulphonatophenyl) porphyrin (TPPS₄) and its corresponding metalloporphyrins (MTPPS₄), where M?=?Co, Ni and Zn were synthesized and characterized by UV?Cvisible spectroscopy, infra red spectroscopy and ¹H nmr spectroscopy. Thermal studies of these porphyrins were conducted in synthetic air from room temperature to 800?°C. The residues of MTPPS₄ were qualitatively analyzed which showed the presence of corresponding metal oxides and Na₂SO₄. Further, the above porphyrins were subjected to TG-EGA-MS analysis in argon atmosphere to study the evolved gases/species during the thermal events. This information is useful to know the ring opening sequence of these porphyrins at corresponding temperatures.     

Effect of a coadsorbent on the performance of dye-sensitized TiO2 solar cells: shielding versus band-edge movement

The mechanism by which the adsorbent chenodeoxycholate, cografted with a sensitizer onto TiO2 nanocrystals, alters the open-circuit photovoltage and short-circuit current of dye-sensitized solar cells was investigated. The influence of tetrabutylammonium chenodeoxycholate on dye loading was studied under a variety of conditions in which the TiO2 films were exposed to the sensitizing dye and coadsorbent. Photocurrent--voltage measurements combined with desorption studies revealed that adding chenodeoxycholate reduces the dye loading by as much as 60% while having a relatively small effect on the short-circuit photocurrent. Calculations along with measurements showed that even at low loading, enough dye is present to absorb a significant fraction of the incident light in the visible spectrum. In concurrence with the observations of others, we find evidence for weakly and strongly adsorbed forms of the dye resulting from either different binding conformations or aggregates. The most strongly adsorbed dyes are less susceptible to displacement by chenodeoxycholate than those that are weakly adsorbed. While having no observable effect on dye coverage, multiple exposures of a TiO2 film to a dye solution substantially increased the fraction of strongly adsorbed dye as judged by the resistance of the adsorbed dye to displacement by chenodeoxycholate. Measurements of the open-circuit voltage as a function of the photocharge density, determined by infrared transmittance, showed that chenodeoxycholate not only shifts the conduction band edge to negative potentials, but also significantly increases the rate of recombination. The net effect of adding chenodeoxycholate is, however, to improve the photovoltage.     

Entropic and electrostatic effects on the folding free energy of a surface-attached biomolecule: an experimental and theoretical study

Surface-tethered biomolecules play key roles in many biological processes and biotechnologies. However, while the physical consequences of such surface attachment have seen significant theoretical study, to date this issue has seen relatively little experimental investigation. In response we present here a quantitative experimental and theoretical study of the extent to which attachment to a charged-but otherwise apparently inert-surface alters the folding free energy of a simple biomolecule. Specifically, we have measured the folding free energy of a DNA stem loop both in solution and when site-specifically attached to a negatively charged, hydroxylalkane-coated gold surface. We find that whereas surface attachment is destabilizing at low ionic strength, it becomes stabilizing at ionic strengths above ~130 mM. This behavior presumably reflects two competing mechanisms: excluded volume effects, which stabilize the folded conformation by reducing the entropy of the unfolded state, and electrostatics, which, at lower ionic strengths, destabilizes the more compact folded state via repulsion from the negatively charged surface. To test this hypothesis, we have employed existing theories of the electrostatics of surface-bound polyelectrolytes and the entropy of surface-bound polymers to model both effects. Despite lacking any fitted parameters, these theoretical models quantitatively fit our experimental results, suggesting that, for this system, current knowledge of both surface electrostatics and excluded volume effects is reasonably complete and accurate.     

Heteroatom effect at C7 of norbornadiene-Quadricyclane system for maximizing the solar energy storage: DFT calculations

An attempt is made to maximize the solar energy storage in norbornadiene (1)/quadricyclane (2) system, through exchanging of heteroatoms at C₇ of 1 and 2; calculating the corresponding energies at MP2/6-311++G(3df,2p)//B3LYP/6-311++G(3df,2p) and B3LYP/6-311++G** levels of theory. Free energy gaps between 1 _X and 2 _X, δG_(1x)-(2x), and solar energy storage is the most for 1 _Se, 1 _As and 1 _Al from group VIII, VII and III of the Table, respectively.     

Cooperative hydrogen-bonding effects in a water square: a single-crystal neutron and partial atomic charges and hardness analysis study

Four isomorphous complexes of formula [M(L)(4)(H(2)O)(2)]SO(4).2H(2)O (M = Co, 1a; Ni, 1b; Cu, 1c; Zn, 1d) have been isolated and characterized by single-crystal X-ray diffraction and neutron diffraction using the quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin as well as by thermogravimetric analysis. The structures contain a discrete, strongly hydrogen-bonded water tetramer which causes a significant distortion of the metal coordination sphere in each case. Partial atomic charges and hardness analysis (PACHA) calculations reveal that the shortest hydrogen bonds are not the strongest in this constrained, cyclic solid-state structure and show that the distortion at the metal center is caused by the drive to maintain the integrity of the water tetramer. The system undergoes a disorder-order transition on slow cooling that provides insight into the nature of communication between water squares.     

Effect of coadsorbent properties on the photovoltaic performance of dye-sensitized solar cells

Stearic acid as a coadsorbent, which has a low dipole moment and high solubility, retarded the rate of dye adsorption during the competitive anchoring process on the TiO(2) layer in dye-sensitized solar cells (DSCs), thereby increasing the content of strongly bound dye on the TiO(2) surface. This resulted in an approximately 25% improvement in both J(SC) and the power conversion efficiency of the DSCs, even for much lower dye coverage.     

Effect of sensitizer adsorption temperature on the performance of dye-sensitized solar cells

Employing a mesoscopic titania photoanode whose bilayer structure was judiciously selected to fit the optoelectronic characteristics of the Ru-based heteroleptic complex Na-cis-Ru(4,4'-(5-hexyltiophen-2-yl)-2,2'-bipyridine)(4-carboxylic-acid-4'-carboxylate-2,2'-bipyridine)(thiocyanate)(2), coded as C101, we investigated the effect of temperature for dye adsorption on the photovoltaic performance of dye-sensitized solar cells (DSCs). We found a significant efficiency enhancement upon lowering the temperature applied during the sensitizer uptake from solution. When the dye adsorption was performed at 4 °C, the photovoltaic performance parameters measured under standard reporting conditions (AM1.5 G sunlight at 1000 W/m(2) intensity and 25 °C), i.e., the open circuit voltage (V(oc)), the short circuit photocurrent density (J(sc)), the fill factor (FF), and consequently the power conversion efficiency (PCE), improved in comparison to cells stained at 20 and 60 °C. Results from electrochemical impedance spectroscopy (EIS) and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) show that the self-assembled layer of C101 formed at lower temperature impairs the back-electron transfer from the TiO(2) conduction band to the triiodide ions in the electrolyte more strongly than the film produced at 60 °C. Profiting from the favorable influence that the low-temperature dye uptake exerts on photovoltaic performance, we have realized DSCs showing a power conversion efficiency of 11.5%.