The concentration ratio of the parabolic dish solar collector (PDSC) is considered to be one of the highest among the concentrated solar power technologies (CSPs); therefore, such system is capable of generating more heat rate. The present paper focuses on the integration of the PDSC with the combined cycle (gas cycle as the toping cycle and steam cycle as the bottoming cycle) along with the utilization of waste heat from the power cycle to drive the single effect lithium bromide/water absorption cycle. Molten salt is used as a heat transfer fluid in the solar collector. The engineering equation solver (EES) is employed for the mathematical modeling and simulation of the solar integrated system. The various operating parameters (beam radiation, inlet and ambient temperatures of heat transfer fluid, mass flow rate of heat transfer fluid, evaporator temperature, and generator temperature) are varied to analyze their influence on the performance parameters (power output, overall energetic and exergetic efficiencies, outlet temperature of the receiver, and as coefficient of performance (COP) and exergy efficiencies) of the integrated system. The results show that the overall energy and exergy efficiencies are observed to be 39.9% and 42.95% at ambient temperature of 27 °C and solar irradiance of 1000 W/m 2 . The outlet temperature of the receiver is noticed to decrease from 1008 K to 528 K for an increase in the mass flow rate from 0.01 to 0.05 kg/s. The efficiency rate of the power plant is 38%, whereas COP of single effect absorption system is 0.84, and it will decrease from 0.87 to 0.79. However, the evaporator load is decreased to approximately 9.7% by increasing the generator temperature from 47 °C to 107 °C.

This work aims at providing insight into developmental and operational experience of an innovative milk cooler which uses solar thermal energy for cooling of fresh milk by way of vapor absorption refrigeration system (VARS). The system uses CPC solar collector(s) producing medium temperature that is desired to provide required thermal energy to the generator of VARS. However, mismatch between the time of availability of solar energy and cooling period of milk raises a demand of integrating thermal storage to this system for use of thermal energy at appropriate times. The novelty of this work is the development of experimental setup and its operation as innovative design to meet the requirement and possible model for the industry to operate and grow using the suggested system. The design, while addressing the problem of grass root level people for generation of income, also helps in reducing the carbon footprint of milk industry, and in the world environment as a whole.

A building energy simulation study is carried out to analyze the performance of a triple-hybrid single-effect vapor absorption cooling system (VACS) operated by solar, natural gas, and auxiliary electricity-based cogeneration. A high capacity small office building subjected to different climatic conditions is considered. The system is designed to continuously maintain a specified building comfort level throughout the year under diverse environmental conditions. Simulations are done at different generator temperatures to investigate the performance in terms of total annual electric energy consumption, heating energy, and the coefficient of performance (COP). The performance of the present VACS is compared with the conventional compression-based system, which demonstrates the electric energy and cost saving potentials of the proposed VACS. Simulation outcomes are well-validated against benchmark data from national renewable energy laboratory and energy conservation building code. Interestingly, it is found that beyond a certain collector area, surplus energy savings can be acquired with the present triple-hybrid VACS as compared to the compression-based cooling. Results also show that COP of the simulated system is in line with experimental values available in the literature. Finally, recommendations are given to operate the complete system on solar and biomass resources, which provide encouraging opportunity for agriculture-based countries.

Radiation absorption is investigated in a particle curtain formed in a solar free-falling particle receiver. An Eulerian–Eulerian granular two-phase model is used to solve the two-dimensional mass and momentum equations by employing computational fluid dynamics (CFD) to find particle distribution in the curtain. The radiative transfer equation (RTE) is subsequently solved by the Monte Carlo (MC) ray-tracing technique to obtain the radiation intensity distribution in the particle curtain. The predicted opacity is validated with the experimental results reported in the literature for 280 and 697 μ m sintered bauxite particles. The particle curtain is found to absorb the solar radiation most efficiently at flowrates upper-bounded at approximately 20 kg s −1 m −1 . In comparison, 280 μ m particles have higher average absorptance than 697 μ m particles (due to higher radiation extinction characteristics) at similar particle flowrates. However, as the absorption of solar radiation becomes more efficient, nonuniform radiation absorption across the particle curtain and hydrodynamic instability in the receiver are more probable.

Solar-to-thermal energy conversion technologies are an important and increasingly promising segment of our renewable energy technology future. Today, concentrated solar power (CSP) plants provide a method to efficiently store and distribute solar energy. Current industrial solar-to-thermal energy technologies employ selective solar absorber coatings to collect solar radiation, which suffer from low solar-to-thermal efficiencies at high temperatures due to increased thermal emission from selective absorbers. Solar absorbing nanofluids (a heat transfer fluid (HTF) seeded with nanoparticles), which can be volumetrically heated, are one method to improve solar-to-thermal energy conversion at high temperatures. To date, radiative analyses of nanofluids via the radiative transfer equation (RTE) have been conducted for low temperature applications and for flow conditions and geometries that are not representative of the technologies used in the field. In this work, we present the first comprehensive analysis of nanofluids for CSP plants in a parabolic trough configuration. This geometry was chosen because parabolic troughs are the most prevalent CSP technologies. We demonstrate that the solar-to-thermal energy conversion efficiency can be optimized by tuning the nanoparticle volume fraction, the temperature of the nanofluid, and the incident solar concentration. Moreover, we demonstrate that direct solar absorption receivers have a unique advantage over current surface-based solar coatings at large tube diameters. This is because of a nanofluid's tunability, which allows for high solar-to-thermal efficiencies across all tube diameters enabling small pressure drops to pump the HTF at large tube diameters.

The solar photovoltaic thermal system (PVT) facilitates conversion of incoming solar radiations into heat and electricity simultaneously. The beam split photovoltaic thermal system (BSPVT) is one of the PVT systems. In this system, the incoming solar beam is splitted and used separately for PV and thermal system. The feasibility of water, silicone oil, and coconut oil as spectrum filter for C–Si solar photovoltaic system is reported in the literature recently. However, the changes in the optical behavior of the liquids due to extended exposure to sunlight (aging effect) had not been considered in most of the previous studies. The current study includes the methodology for the selection of liquids for BSPVT systems, estimation of external quantum efficiency (EQE) of a solar cell using liquids, and the aging effect on the liquid spectrum filters. The spectral response of the solar cell is analyzed using BENTHAM, (PVE 300) for 300–1100 nm. In this study, it has been observed that the aging of silicone oil reduces the electrical performance of the solar cell. On the other hand, the aged coconut oil improves the electrical performance of the solar cell as compared to the fresh coconut oil spectrum filter.

Natural dye extract of the saffron petal, purified by solid-phase extraction (SPE) technique, has been studied as a novel sensitizing dye to fabricate TiO 2 nanoparticles-based dye-sensitized solar cells (DSSC). The extract was characterized using ultraviolet–visible (UV–Vis) and Fourier transform infrared (FTIR) spectroscopies to confirm the presence of anthocyanins in saffron petals. The typical current–voltage and the incident photon to current efficiency (IPCE) curves were also provided for the fabricated cell. The saffron petal extract exhibited an open-circuit voltage (Voc) of 0.397 V, short circuit current density (Jsc) of 2.32 mA/cm 2 , fill factor (FF) of 0.71, and conversion efficiency of 0.66%, which are fairly good in comparison with the other similar natural dye-sensitized solar cells. These are mainly due to the improved charge transfer between the dye extract of saffron petal and the TiO 2 anode surface. Considering these results, it can be concluded that the use of saffron petal dye as a sensitizer in DSSC is a promising method for providing clean energy from performance, environmental friendliness, and cost points of view.

In this work, we have chosen the low cost natural dye extracted from Saraca asoca flowers to act as a sensitizer dye for TiO 2 -based dye-sensitized solar cell (DSSC). UV–visible spectroscopic studies of ethanolic extract of dyes have been done in order to understand light absorption behavior of dye. The natural dye extract covers appreciable spectrum of solar radiation, 400–500 nm with an absorption maximum at 450 nm that makes it suitable for use as a photosensitizer in DSSC application. The dye adsorbed onto the semiconductor facilitates electron transfer across the dye/semiconductor interface. FTIR spectra of extract revealed the presence of anchoring groups and coloring constituents. DSSC fabricated with TiO 2 and natural dye extract obtained from Saraca asoca flowers as sensitizer has shown open-circuit voltage ( V oc ) 516 mV, short-circuit current density ( J sc ) 0.29 mA/cm 2 , fill factor (FF) 0.65, incident photon-to-current conversion efficiency (IPCE) 43%, and conversion efficiency of 0.09%. This work briefly discusses the simple extraction technique of natural dye and its performance in DSSC.

A new symmetric nonimaging parametric trough collector (PmTC) for an evacuated circular receiver is proposed having an absorber diameter of 70 mm similar to the LS3/Eurotrough absorber one, and a circular secondary. The optical design method is explained and a sensitivity analysis is conducted with respect to the diameter of the secondary and to the acceptance angle. In the design process, transmission, absorption, and reflection losses are neglected. A secondary mirror radius of 145 mm and an acceptance angle of ±14 mrad were chosen as realistic values. For these values a concentrator geometry having 8.7 m gross aperture and 100% intercept factor for rays impinging on the primary within the referred acceptance angle is obtained producing a net concentration ratio relative to the thermodynamic ideal limit of 0.52 compared to 0.31 for traditional parabolic trough collectors. The new concentrator is composed of a primary discontinuous reflector with two symmetrical portions with parametric geometry, and a central parabolic portion located between the other two. The ensemble secondary receiver can be dressed up with the secondary concentrator manufactured by partially mirroring a diameter adapted glass tube—either internally or externally—or alternatively by means of a commercial evacuated receiver and an independent 145 mm radius arc of circumference external secondary reflector. Monte Carlo ray-tracing results show that only 15% of the rays undergo secondary reflection before arriving to the absorber and a sharp angle transmission curve. The new concentrator is proposed for application in solar thermal energy (STE) trough power plants.

The experimental method is extensively used to determine the temperature of a photovoltaic (PV) module at different hours of a day. In this method, the module temperature is measured using a temperature sensor mounted on the back of PV module. However, the experimental measurements have high cost and are not applicable everywhere. In this study, an optical–thermal model was used to predict all the PV module layer temperatures in two cases: tilted toward the south and fixed on a two-axis sun tracker. The impact of accurate consideration of the wind velocity and the ambient temperature on the PV module temperature was the main strength of the present simulation. This was carried out testing several correlations for prediction of convection heat transfer coefficient in the modeling process. The front and back layer temperatures as well as the silicon (Si) layer temperature of PV module were separately determined. To verify the results of the simulation, the temperatures of four PV modules measured in four different locations of the world, namely, China, Germany, Australia, and Brazil, were used. The results showed that the present study predicts the temperature of PV module more accurately compared to the previous studies. It was also shown that the average temperature errors between the measured and the predicted temperatures relative to the maximum module temperature were 2.19%, 2.3%, and 2.85%, for Australia, Brazil, and Germany, respectively.

Spherical sintered bauxite particles between 200 μm and 700 μm in diameter have been shown to be effective in the direct absorption and storage of concentrated solar energy. These particles are commercially available in large quantities and exhibit as-received solar weighted absorptance (αs) greater than 0.90, which gradually degrades with extended heating in air at 700 °C and above. The degradation mechanism is an oxidation reaction that can be reversed via thermal or chemical reduction, resulting in αs > 0.95 along with enhanced resistance to further degradation for some formulations. Certain metal oxide pigments, added to Al2O3:SiO2, have proven to achieve solar weighted absorptance levels similar to those of the commercially available particles and may be promising alternatives to currently available materials.

Copper oxide (CuO) is a p-type semiconductor having a band gap energy of 1.5 eV, which is close to the ideal energy gap of 1.4 eV required for solar cells to allow good solar spectral absorption. The inherent electrical characteristics of CuO nanoparticles make them attractive candidates for improving the performance of polymer solar cells (PSCs) when incorporated in the active polymer layer. The incorporation of CuO nanoparticles in P3HT/PC70BM solar cells at the optimum concentration yields 40.7% improvement in power conversion efficiency (PCE). The CuO nanoparticles in the size range of 100–150 nm have an effective average band gap of 2.07 eV. In addition, the X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses show improvement in P3HT crystallinity, and surface analysis by atomic force microscope (AFM) shows an increase in surface roughness of the PSCs. The key factors namely photo-absorption, exciton diffusion, dissociation, charge transport, and charge collection inside the PSCs which affect the external quantum efficiency (EQE) and PCE of these cells are analyzed.

A conceptual design of the power system for a water–lithium bromide absorption system is presented in this work for a given cooling load. The proposed system utilizes both solar thermal and the photovoltaic (PV) generated electrical energy for its operation. The performance of the power system is analyzed over a complete year for a designed operation strategy. It is found that the proposed system can provide an annual-average surplus of 17.4 kWh of energy per day after meeting the in-house energy requirements. Finally, an economic analysis is performed to calculate the payback period of the system.

Effect of 1,8-diiodooctane on the performance of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) solar cells with glass/indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/P3HT: PCBM/Ca/Al structure was studied. The morphology and thickness of the active layer were investigated using atomic force microscopy (AFM). The UV-visible spectroscopy and X-ray diffraction (XRD) analysis were used to study the absorption behavior (of the solutions and coated layers) and crystallinity of the active layer, respectively. The results show that the existence of 1,8-diiodooctane reduced the open circuit voltage from 0.81 to 0.52 V and increased the short circuit current by about three folds; the fill factor (FF) and power conversion efficiency were increased from 36.0 to 54.1% and 0.47% to 1.54%, respectively. These changes can be attributed to the enhanced crystallinity of P3HT or the doping effect of 1,8-diiodooctane on P3HT chains. UV-visible analysis demonstrated that the addition of 1,8-diiodooctane to the solution did not change the absorption onset, whereas in the coated layers, the maximum absorption peak shifted to higher wavelengths. The XRD analyses demonstrated the enhancement of crystallinity of P3HT upon the introduction of 1,8-diiodooctane.

This study describes the development and characterization of novel high-temperature thermal storage media, based on inclusion of transition metal chlorides in the potassium–sodium chloride eutectic system, (K–Na)Cl (melting temperature of 657 °C, latent heat of 278 J/g). At the melting temperature of (K–Na)Cl, infrared (IR) radiation can play a major role in the overall heat transfer process—90% of spectral blackbody radiation falls in the range of 2–13 μ m. The authors propose inclusion of small amounts (less than 0.2 wt.%) of IR-active transition metal chlorides to increase radiative absorption and thereby enhance heat transfer rates. A new IR-reflectance apparatus was developed to allow for determination of the spectral absorption coefficient of the newly formulated phase-change materials (PCMs) in the molten state. The apparatus consisted of an alumina crucible coated at the bottom with a reflective (platinum) or absorptive (graphite) surface, a heated ceramic crucible-holder, and a combination of zinc sulfide (ZnS) and zinc selenide (ZnSe) windows for containment of the salt and allowance of inert purge gas flow. Using this apparatus, IR spectra were obtained for various transition metal chloride additives in (K–Na)Cl and improved IR activity, and radiative transfer properties were quantified. Further, thermophysical properties relevant to thermal energy storage (i.e., melting temperature and latent heat) are measured for the pure and additive-enhanced thermal storage media.

In this work, we report the efficiency enhancement of a GaAs solar cell by using a luminescent down-shifting (LDS) layer consisting of (CdSe)ZnS quantum dots (QDs). The calculated conversion efficiency shows strong dependence on the luminescence quantum efficiency (LQE) and concentration of QDs in the LDS layer as well as the difference in external quantum efficiency (EQE) of the solar cell in the absorption and emission regions of the QD. Although the irradiance of the modified spectrum by the LDS layer was reduced with increases in QD concentration, the emission range of QDs in the spectrum was intensified. So the optimum parameters need to be calculated carefully. When we measured the GaAs solar cell with the LDS layer, it showed increased current density and consequently improved efficiency. The highest performance difference between the GaAs solar cell efficiencies with and without the LDS layer was over 2.8%, although a crystalline silicon solar cell below the LDS layer showed negative change in efficiency owing to its small EQE difference.

A detailed three-dimensional (3D) computational fluid dynamics (CFD) model of a direct absorption solar collector (DAC) is presented. Radiative transfer equation (RTE) is coupled with Navier–Stokes equations and solved numerically to predict the collector efficiency. The spectral properties of absorbing liquids are captured using a band-averaged absorption model. This numerical model is validated with experimental data for two different types of absorbing fluids viz., gray (graphite particles in water) and nongray (copper sulfate) fluids. The validated model is used for parametric studies to determine the right design choices for an improved collector. Impact of optical concentration ratio (CR), optical density of the fluid, mass flowrate, and thermal insulation on the collector efficiency were studied. Increase in collector efficiency of up to 28% is seen due to higher optical CRs, which is attributable to good absorption characteristics of the receiver and reduced area for losses. The collector efficiency does not improve with absorption coefficient of the fluid beyond a certain value for a given thickness of the fluid layer. The range of mass flow rates considered in the study was found to have no impact on collector efficiency. Thermal insulation is found to be very effective in minimizing the overall thermal losses and enhancing the collector efficiency. The numerical model presented here may be used to identify optimum CR, absorption coefficient of liquid for a direct absorption concentrating collector.

This paper reports the application of the Ru2+, Cu+, and Fe2+ complexes in form of RuL2(SCN)2, CuL2(SCN)2− for dye-sensitized solar cell (DSSC) development. The calculation results, given by quantum chemistry, demonstrated that the complex containing copper is more suitable than the one containing iron. The modification of Cu(I) complex by using various numbers of ligands enhanced photon absorption capacity as well as the absorption range. The addition of an organic ligand such as an electron attraction group to the benzene ring gave a better result as compared to the inorganic ones. Based on the analysis conducted, CuM2(SCN)2− is considered as potential material for N3 replacement.

A new multigeneration system based on an ocean thermal energy conversion (OTEC) system equipped with flat plate and PV/T solar collectors, a reverse osmosis (RO) desalination unit to produce fresh water, a single effect absorption chiller, and proton exchange membrane (PEM) electrolyzer is proposed and thermodynamically assessed. Both energy and exergy analyses are employed to determine the irreversibilities in each component and assess the system performance. A parametric study is performed to investigate the effects of varying design parameters and operating conditions on the system energy and exergy efficiencies. In addition, an economic assessment of the multigeneration system is performed, and the potential reduction in total cost rate when the system shifts from power generation to multigeneration are investigated.

A combined cooling, heating and power generation (CCHP) system is modeled and optimized. The heat demand in this plant can provide by prime mover, backup boiler, and solar panels. Both the genetic algorithm (GA) and particle swarm optimization (PSO) are used to find the maximum of actual annual benefit (AAB) as an objective function. The design parameters or decision variables are capacity of prime mover, their number as well as their partial load (PL), backup boiler and storage tank heating capacity, the number of solar panels, types of electrical and absorption chiller as well as the electric cooling ratio. Both genetic and PSO algorithms are converged with maximum 0.6% difference. As a result, a diesel engine with nominal power of 350 kW combined with 255 solar panels is selected in the optimum situation. In addition, the optimization results show that the advantage of absorption chiller than the electrical chiller due to the extra availability of heat by the prime mover at the warm season in residential area. Finally, the effect of electric cooling ratio, number of solar panels and solar panels investment cost on objective function are investigated and results are reported.