Solar Energy Storage Applications Research Articles

Templated assembly of photoswitch Azobenzene (4-(4-nitrophenylazoyl)-phenol) by functionalization of multi-walled carbon nanotube for solar energy storage applications

In order to provide global energy applications, solar energy resources will desire remarkable advances in solar energy technologies. In this paper, the novel synthesis of the functionalization of Multi-wall Carbon Nanotube(MWCNT) with Azobenzene molecule (4-(4-nitrophenylazoyl)-phenol) by esterification method was approached. The covalent bond of carbonyl was revealed in FTIR Test (Fourier-Transform Infrared Spectroscopy). Templating Azobenzene molecules on the side wall of MWCNT increased the stored energy per Azobenzene molecule and created hybrid Solar Thermal Fuels (STF). The DSC Test (Differential Scanning Calorimetry) showed that Solar Thermal Fuels composed of a photoswitchable molecules indicates significantly increased energy storage capabilities over the generation of a nano-templated structure.

Experimental Investigation of Co–Cu, Mn–Co, and Mn–Cu Redox Materials Applied to Solar Thermochemical Energy Storage

Thermochemical energy storage (TCES) can be achieved via reversible redox reactions based on metal oxides for solar energy storage applications in solar power plants. As cobalt oxide (Co3O4/CoO) and manganese oxide (Mn2O3/Mn3O4) appear as attractive candidates for TCES, an experimental study has been conducted to evaluate the potential of mixed oxides from the Co–Cu–O, Mn–Co–O, and Mn–Cu–O systems. The addition of Cu to Co3O4 allows accessing promising materials with good cycling stability and high reaction enthalpy for TCES applications. As for the Mn–Co–O and Mn–Cu–O systems, the role of the hausmannite phase formation at low Co or Cu contents on the irreversibility of Mn-based mixed oxides is made evident, thus demonstrating the interest of the addition of a secondary metal oxide to the Mn-based material. For the Mn–Co–O system, low amounts of Mn should be favored, since both the oxygen storage capacity and the reaction enthalpy significantly increase with decreasing Mn contents, and the reversibility ...

Electrocatalytic water oxidation by a nickel oxide film derived from a molecular precursor

In this study, we fabricated a NiOx film by electrodeposition of an ethanediamine nickel complex precursor (pH = 11) on a fluorine-doped tin oxide substrate. The resulting film is robust and exhibits high catalytic activity for electrochemical water oxidation. Water oxidation is initiated with an overpotential of 375 mV (1 mA/cm2) and a steady current density of 8.5 mA/cm2 is maintained for at least 10 h at 1.3 V versus the normal hydrogen electrode. Kinetic analysis reveals that there is a 2e−/3H+ pre-equilibrium process before the chemical rate-determining step. The low-cost preparation, robustness, and longevity make this catalyst competitive for applications in solar energy conversion and storage.

Preparation of metal selenide nanocrystals with hot-injection method

Nanomaterials have received extensive and growing research interests due to their unique properties and potential applications in various fields. They have contributed immensely to modern materials science and technology during the last three decades. Among various types of functional nanomaterials, metal selenide nanocrystals have attracted considerable attention because of their special properties. These nanomaterials have been applied in a wide range, such as medicine, electronics, photonics, energy conversion and storage devices, etc. Interestingly, when metals are chemically combined with selenide in the form of nanocrystals, they exhibit semiconductor-like electronic properties. These metal selenide nanocrystals have attracted significant attention in recent years due to their potential applications in solar energy conversion and storage, which are the most important challenges to be addressed to meet the world’s rising demand for clean energy in the future. Hot-injection method is an effective method for the synthesis of metal selenide nanocrystals. The success of this approach lies in the use of non-ionic precursors in high-boiling organic solvents. This makes it possible to grow the nanocrystals relatively slowly at a high temperature, which yields defect-free, well-passivated nanocrystals. The anther important aspect of this method is the separation of the nucleation and growth stages. Due to this, a high degree of monodispersity can be achieved. The fundamental principle of hot-injection method with concrete steps has been introduced. This review surveys the recent progress of the preparation of metal selenide nanocrystals by hot-injection method in terms of binary metal selenide nanocrystals, ternary metal selenide nanocrystals, quaternary, and multinary metal selenide nanocrystals. For binary metal selenide nanocrystals, four important binary metal selenide nanocrystals including CdSe, ZnSe, PbSe, and Sb2Se3 nanocrystals are discussed. Then the achievement of synthesis for CuInSe2 and CuGaSe2 nanocrystals by hot-injection method and their application in photovoltaic field are systematically cataloged as well. And the progress in preparation for CuInGaSe2 and Cu2ZnSnSe4 nanocrystals by hot-injection method has been clarified clearly. Organoselenide chemicals are generally toxic and unstable. The replacement of phosphine containing compounds in the synthesis process of metal selenide nanocrystals via hot-injection method has received considerable attention in recent years. Many attempts have been made to replace trioctylphosphine (TOP) as a medium for delivering selenium in these reactions, but each alternative possesses has significant limitations. This review mainly emphasizes on the recent advances toward the development of methods to achieve “green Se precursor” with high activity and “facile green synthesis” of metal selenide nanocrystals involved in various approaches. Two kinds of different schemes for synthesis and utilization “green Se precursor” are described. Finally, technical challenges and future trends are presented for synthesis of high quality metal selenide nanocrystals, in terms of composition-tunable and structure-controllable multinary metal selenide nanocrystals, green synthesis, industrial production and large-scale application.

Electron localization in rod-shaped triicosahedral gold nanocluster

Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. Little is known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. Here, we reported the observation of exciton localization in triicosahedral Au37 nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S1 electronic state, electrons in Au37 undergo ∼100-ps localization from the two vertexes of three icosahedrons to one vertex, forming a long-lived S1* state. Such phenomenon is not observed in Au25 (dimer) and Au13 (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm-1 observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au37 in the excited state induced by the strong coherent vibrations. The observed electron localization phenomenon provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.

Synthesis and Characterization of α-MnO2/Graphene Nanocomposites for Applications to in High Performance Super Capacitors

In recent years, supercapacitors have attracted a lot of attention due to their applications in portable electronic devices such as mobile phones, laptops, digital camera and also for power applications in hybrid electric vehicles, engine start, and solar energy storage, etc. [1-3]. Transition metal oxides and carbon materials are widely being used in supercapacitors. Among transition metal oxides, MnO2 has been one of the most studied electrode materials because of its cost effectiveness, natural abundance and environmental compatibility. In spite of its various advantages, MnO2 in its pure state is not very useful for supercapacitor applications because of its poor electrical conductivity and electrochemical dissolution upon cycling. On the other hand, graphene has drawn considerable interest because of its ultrahigh surface area (up to 2630 m2/g), and excellent conductivity. Up to now, composites of graphene and MnO2 have been used to improve their capacitance. We have synthesized hetero-structured - nanorods using the low temperature hydrothermal technique [4]. Finally -/graphene nanocomposite was synthesized by sonochemical co-precipitation method as reported earlier [5]. Graphene oxide power, suspended in sulfuric acid solution (1mg/ml), and manganese sulfate (dissolved in sulfuric acid) were mixed together and potassium permanganate solution was added to this solution drop by drop. After 2 hours -/graphene nanocomposite was filtered using centrifuge, washed with DI water and ethanol and dried. The phase structure of - nanorods and -/graphene nanocomposites were studied using powder X-ray diffraction (XRD). The results of physical, thermal and electrochemical characterization of -/graphene nanocomposite will be presented during 231st Electrochemical Society Meeting.

Structural, electronic and optical properties of CsPbX3 (X=Cl, Br, I) for energy storage and hybrid solar cell applications

Abstract Organic-Inorganic perovskites CsPbX3 (X = Cl, Br, I) are investigated for their potential ability and use as solar cells and energy storage materials, using density function theory, generalized gradient approximation and modified Becke-Johnson (TB-mBJ) exchange potential. Structural analysis shows that the lattice constant and unit cell volume varies when CsPbX3 (X = Cl, Br, I) change from cubic phase to tetragonal and orthorhombic structures. The electronic properties show that CsPbCl3, CsPbBr3 and CsPbI3 all are semiconductor in with bandgap between 0.79 eV and 2.54 eV. It is also observed that the bandgap changes when the structure changes. Optical properties show that these materials have a good absorption ability of photons due to their narrow bandgaps. The real e1(ω) and imaginary e2(ω) parts of their dielectric functions show that CsPbCl3, CsPbBr3 and CsPbI3 also possess a great ability of retaining the energy it absorbs. These properties make them very suitable for solar cells and energy storage applications. These materials also behave as superluminescent material at high photon energy.

Band Structure Engineering of Transition-Metal-Based Layered Double Hydroxides toward Photocatalytic Oxygen Evolution from Water: A Theoretical–Experimental Combination Study

Considerable attention has been focused on layered double hydroxides (LDHs) for their applications in solar energy storage and conversion recently, but the in-depth investigation on the semiconducting properties of LDHs is limited. Herein, the electronic properties (band structure, density of states (DOS), surface energy, and band edge placement) of 14 kinds of MIInMIII/IV–A–LDHs (MII = Mg, Co, Ni, Cu, Zn; MIII = Cr, Fe; MIV = Ti; n = 2, 3, 4; A = Cl–, NO3–, CO32–) which contain transition-metal cations as well as their thermodynamic reaction mechanism toward the oxygen evolution reaction (OER) were studied using a density functional theory plus U (DFT + U) method. The calculation results indicate that the (003) plane is the most preferably exposed surface, and all these calculated LDHs are visible light responsive. The OER driving force and overpotential for these LDHs were obtained via their band edge placement and thermodynamic mechanism, and the results show that 10 of the calculated 12 LDHs (Ni2Ti–Cl...

A new composite sorbent based on SrBr2 and silica gel for solar energy storage application with high energy storage density and stability

The excellent matching between the sorption and desorption temperatures of hexahydrated SrBr2 and those required for solar heat storage for building applications, the high heat of reaction (67.5kJ/mol of water) coupled with the gain/loss of 5mol of water per mole of salt make this salt an appealing sorbent for solar thermal energy storage applications coupled to space heating. Due to the morphological instability of this salt, it is necessary to incorporate it in a porous matrix as a composite sorbent. A new composite material for thermochemical energy storage applications was developed. It consists of a mesoporous silica gel impregnated by strontium bromide with salt content equal to 58wt.%. The structure and the sorption properties of the composite were characterized by SEM-EDX, temperature dependent XRD, XRF, and N2 sorption measurements. The salt is homogeneously distributed inside the pores of the silica gel. Water sorption isotherms were measured between 20°C and 80°C, which enabled us to understand the sorption mechanism. A mathematical model was developed and used to fit the experimental data in order to predict the sorption behavior of the composite at different conditions (influence of temperature and pressure conditions on the cycle loading lift and energy storage density). The interest of using such a composite for thermal energy storage application is then discussed (thermal energy produced by solar collector and used for space heating). A high cycle loading lift of 0.22g/g is obtained corresponding to an energy storage capacity of 230Wh/kg and an energy storage density of 203kWh/m3 of packed bed composite (between 30°C and 80°C at 12.5mbar) is reported, with an excellent stability over 14 sorption/desorption cycles. The sorption kinetics of this composite is enhanced compared to pure salt. Test on a laboratory scale open type reactor gives a maximum specific thermal power of 200W/kg and a mean specific thermal power of 92W/kg at 30°C and 12.5mbar for an extent of reaction of 0.68.

Diffusion of dilute gas in arrays of randomly distributed, vertically aligned, high-aspect-ratio cylinders.

In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires) as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i) the gas diffusion coefficient inside such arrays, (ii) the time between collisions of molecules with the nanocylinder walls (mean time of flight), (iii) the surface impingement rate, and (iv) the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport. It can be specifically shown that the gas diffusion coefficient inside such arrays is inversely proportional to the areal density of cylinders and their mean diameter. An example calculation of a diffusion coefficient is delivered for a system of titanium isopropoxide molecules diffusing between vertically aligned carbon nanotubes. Our findings are important for the correct modelling and optimisation of gas-based deposition techniques, such as atomic layer deposition or chemical vapour deposition, frequently used for surface functionalisation of high-aspect-ratio nanocylinder arrays in solar cells and energy storage applications. Furthermore, gas sensing devices with high-aspect-ratio nanocylinder arrays and the growth of vertically aligned carbon nanotubes need the fundamental understanding and precise modelling of gas transport to optimise such processes.

Conformal Electroplating of Azobenzene-Based Solar Thermal Fuels onto Large-Area and Fiber Geometries.

There is tremendous growth in fields where small functional molecules and colloidal nanomaterials are integrated into thin films for solid-state device applications. Many of these materials are synthesized in solution and there often exists a significant barrier to transition them into the solid state in an efficient manner. Here, we develop a methodology employing an electrodepositable copolymer consisting of small functional molecules for applications in solar energy harvesting and storage. We employ azobenzene solar thermal fuel polymers and functionalize them to enable deposition from low concentration solutions in methanol, resulting in uniform and large-area thin films. This approach enables conformal deposition on a variety of conducting substrates that can be either flat or structured depending on the application. Our approach further enables control over film growth via electrodepsition conditions and results in highly uniform films of hundreds of nanometers to microns in thickness. We demonstrate that this method enables superior retention of solar thermal fuel properties, with energy densities of ∼90 J/g, chargeability in the solid state, and exceptional materials utilization compared to other solid-state processing approaches. This novel approach is applicable to systems such as photon upconversion, photovoltaics, photosensing, light emission, and beyond, where small functional molecules enable solid-state applications.

ChemInform Abstract: The Application of Graphene and Its Derivatives to Energy Conversion, Storage, and Environmental and Biosensing Devices

AbstractReview: [329 refs.

The Application of Graphene and Its Derivatives to Energy Conversion, Storage, and Environmental and Biosensing Devices.

Graphene (GR) and its derivatives are promising materials on the horizon of nanotechnology and material science and have attracted a tremendous amount of research interest in recent years. The unique atom-thick 2D structure with sp(2) hybridization and large specific surface area, high thermal conductivity, superior electron mobility, and chemical stability have made GR and its derivatives extremely attractive components for composite materials for solar energy conversion, energy storage, environmental purification, and biosensor applications. This review gives a brief introduction of GR's unique structure, band structure engineering, physical and chemical properties, and recent energy-related progress of GR-based materials in the fields of energy conversion (e.g., photocatalysis, photoelectrochemical water splitting, CO2 reduction, dye-sensitized and organic solar cells, and photosensitizers in photovoltaic devices) and energy storage (batteries, fuel cells, and supercapacitors). The vast coverage of advancements in environmental applications of GR-based materials for photocatalytic degradation of organic pollutants, gas sensing, and removal of heavy-metal ions is presented. Additionally, the use of graphene composites in the biosensing field is discussed. We conclude the review with remarks on the challenges, prospects, and further development of GR-based materials in the exciting fields of energy, environment, and bioscience.

Experimental assessment of oxygen exchange capacity and thermochemical redox cycle behavior of Ba and Sr series perovskites for solar energy storage

Thermochemical redox processes involving novel oxygen ion conducting materials with perovskites structure are studied to evaluate their application potential for solar energy storage in concentrated solar power plants. A series of Ba and Sr containing perovskites was synthesized via modified Pechini method and their crystal structure was characterized by XRD. The thermochemical reduction–oxidation steps of the redox cycle and oxygen exchange capacity of the perovskites were investigated by thermogravimetric (TG) analysis. The results revealed that Co-based perovskites are the most promising candidates for solar thermochemical energy storage application. The O2 release/absorption of Co-based perovskites is completed in a reversible way when reaching a given temperature. BaCoO3 reduction occurs promptly when the temperature reaches 900°C in Ar atmosphere (pO2=10−6atm), and the oxidation proceeds completely as soon as the gas is switched from Ar to 20% O2 at 600°C. In these conditions, the amount of monatomic oxygen released/captured reaches 0.47/0.49mol per mol BaCoO3. Part substitution in A-site improves the O2 exchange capacity of Ba0.5Sr0.5FeO3−δ but not Ba0.5Sr0.5CoO3−δ, while part substitution in B-site improves the O2 exchange capacity of SrCo0.8Fe0.2O3−δ and SrCo0.2Fe0.8O3−δ. Part substitution together in A-site and B-site of perovskites does not improve the O2 exchange capacity of Ba0.5Sr0.5Co0.8Fe0.2O3−δ and Ba0.5Sr0.5Co0.2Fe0.8O3−δ. The Fe-based perovskites generally exhibit continuous non-stoichiometry changes according to the temperature change suggesting continuous topotactic evolution, while the non-stoichiometry of Mn-based systems is almost not changed at the considered temperatures. Ba containing systems (BaCoO3, BaFeO3 and Ba0.5Sr0.5CoO3) show the largest oxygen release ability under inert (pO2=10−6atm) or oxidizing atmosphere (pO2=0.2atm) up to 1050°C, while only BaCoO3 can be fully re-oxidized at 600°C in a 20% O2 atmosphere, with an energy storage capacity of 292J/g.

Measuring Thermochemical Energy Storage Capacity with Redox Cycles of Doped-CaMnO3

Our team has explored redox cycles of doped CaMnO3-δ between air and low O2 partial pressures (~10-4 bar) for high-temperature thermochemical energy storage (TCES) applications. In this study, we have explored both A-site and B-site doped compositions using earth-abundant cations to identify perovskites for cost-effective TCES in concentrated solar and other high-temperature, thermal storage applications. Reduction of doped CaMnO3-δ above 800 °C in the low P O2 requires some amount of dopant to avoid irreversible decomposition of the perovskite structure observed for reduction of undoped CaMnO3-δ [1]. This study shows that small amounts (5%) of A-site or B-site dopant can stabilize the CaMnO3-δ perovskite structure during reduction at temperatures up to 1100 °C and P O2 = 10-4 bar. For selected, stable doped CaMnO3-δ compositions, total specific TCES (Δh tot) was defined by the sum of specific sensible energy (Δh sens) and chemical energy (Δh chem) captured during heating and reduction from air at a cool temperature (T C fixed at 500 °C in this study) to low P O2 at varying high temperatures ( T H). B-site doping with 5% Cr and A-site doping with 5% Sr provided thermodynamic limits of Δh tot over 720 kJ kg-1 and 790 kJ kg-1 respectively for T H = 1000 °C. These materials were also tested kientically to assess the rates at which energy storage is captured during reduction and released during oxidation as relevant for concentrated solar energy storage applications. The results indicate that the doped CaMnO3-δ and in particular A-site doped Ca0.95Sr0.05MnO3-δ have promise as a TCES storage media with Δh chem providing just under half of the total energy stored during the combined heating and reduction. For the perovskite redox cycles, the heat of oxide reduction -ΔH O can vary with non-stoichometry δ [2]. To find the integrated Δh chem, the functional dependence of ΔH O with δ must be detemined. Two methods have been undertaken to explore this functional dependence: 1) combined TGA-DSC calorimetry measurements with incremental changes in δ, and 2) point-defect model fitting to equilibrium δ vs. P O2 data from TGA measurements [3,4]. The DSC measurements showed that the magnitude of ΔH O decreases to a near constant value for δ > 0.1 as illustrated for Ca0.95Sr0.05MnO3-δ in Figure 1. Similar trends were observed for the other perovskite compositions. The alternative method for finding ΔH O as a function of δ by fitting the equilibrium δ vs. P O2 involved modeling the perovskite reduction with two reversible point-defect reactions -- oxide-ion vacancy formation and Mn cation disproportionation from 4+ to 3+ and 5+ states [4]. The model fits originally assumed that these two reactions had enthalpies independent of δ but the contribution of the disproportionation reaction increased with δ thereby causing the combined ΔH O to have a minor dependence on δ as also shown in Figure 1. The point defect modeling did not show the same trends for ΔH O vs. δ but provided very similar values at high δ > 0.1. The integration of ΔH O over a change in δ (i.e. Δδ as in Table 1) provides a basis for calculating the integrated Δh chem as a function of T H. Integrated Δh chem values for CaCr0.05Mn0.95O3-δ, Ca0.95Sr0.05MnO3-δ, and Ca0.9Sr0.1MnO3-δ are shown in Table 1 along with the total energy stored which includes Δh sens derived from integration of CP with respect to T over the redox cycle heating. The higher Δh chem and associated Δh tot for Ca0.95Sr0.05MnO3-δ stems from its increase reducibility without a loss in heat of reaction and makes it a more promising material for TCES applications in these temperature ranges.For thermal storage application, kinetic rates of TCES capture are important, particularly for concentrated solar applications where solar receiver residence times are limited. To explore kinetics, reduction and oxidation rates of porous perovskite particle beds were measured for fitting thermodynamically consistent kinetic models to the observed rates. Kinetic testing and model fitting for the Ca0.95Sr0.05MnO3-δ indicates that it achieves approximately 80% of its Δh chem thermodynamic limit in 60 s exposure of low P O2 gas for reduction at T H = 900 °C. On the other hand, at the same temperature reoxidation occurs rapidly and releases over 90% of the Δh chem limit in 30 s. The thermodynamic consistent model involving surface kinetics and ionic bulk diffusion in the perovskite particles for Ca0.95Sr0.05MnO3-δ and for CaCr0.05Mn0.95O3-δ provide a basis for designing reactors for redox cycles to be used in TCES for concentrated solar and other potential thermal energy storage applications.

Coil-Type Asymmetric Supercapacitor Electrical Cables.

Cable-shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable-shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable-shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil-type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical-electrochemical stability. The CASECs show excellent charge-discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm(-3)), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets.

Hybrid Molecule-Nanocrystal Photon Upconversion Across the Visible and Near-Infrared.

The ability to upconvert two low energy photons into one high energy photon has potential applications in solar energy, biological imaging, and data storage. In this Letter, CdSe and PbSe semiconductor nanocrystals are combined with molecular emitters (diphenylanthracene and rubrene) to upconvert photons in both the visible and the near-infrared spectral regions. Absorption of low energy photons by the nanocrystals is followed by energy transfer to the molecular triplet states, which then undergo triplet-triplet annihilation to create high energy singlet states that emit upconverted light. By using conjugated organic ligands on the CdSe nanocrystals to form an energy cascade, the upconversion process could be enhanced by up to 3 orders of magnitude. The use of different combinations of nanocrystals and emitters shows that this platform has great flexibility in the choice of both excitation and emission wavelengths.

Thermal Conductivity of Eutectic Nitrates and Nitrates/Expanded Graphite Composite as Phase Change Materials.

Nitrates and eutectic nitrate mixtures are considered as potential phase change materials (PCMs) for the middle-temperature-range solar energy storage applications. But the extensive utilization is restricted by the poor thermal conductivity and thermal stability. In the present study, sodium nitrate-potassium nitrate eutectic mixture was used as the base PCM, and expanded graphite (EG) was added to the mixture so as to improve the thermal conductivities. The elaboration method consists of a physically mixing of salt powders with or without EG, and the composite PCMs were cold-compressed to form shape-stabilized PCMs at room temperature. The thermal conductivities of the composite PCMs fabricated by cold-compression were investigated at different temperatures by the steady state method. The results showed that the addition of EG significantly enhanced the thermal conductivities. The thermal conductivities of pure nitrates and nitrates/EG composite PCMs in solid state showed the behavior of temperature dependant, and they slightly decreased with the increase of the temperature.

Photochemical Upconversion: The Primacy of Kinetics.

Incoherent photochemical upconversion is a process by which low-energy light can be converted into a higher-energy form with promising applications in solar energy conversion and storage, photocatalysis, biological imaging, and photochemical drug activation. Despite intensive research in recent years, there remains an underappreciation of the chemical kinetics that controls the efficiency of the upconversion process. Here, we provide a brief overview of research into photochemical upconversion and provide a tutorial to guide the design of efficient upconversion compositions. We further provide our perspective on where this area of research is heading and how very efficient systems will be developed.

Thermal performance enhancement of shell and tube Latent Heat Storage Unit using longitudinal fins

Latent Heat Storage Unit (LHSU) employing Phase Change Materials (PCMs) is an effective means of thermal energy storage for solar applications. The practical use of such energy storage unit is however limited by the low thermal conductivity of the available PCMs. Significant augmentation in the heat transfer rate of PCMs is possible by installation of longitudinal fins. The augmentation in heat transfer for a shell and tube type LHSU is estimated by carrying out experimental analysis with three longitudinal fins installed on the heat transfer fluid (HTF) tube. The heat transfer augmentation is established in terms of melting and solidification time for varying fluid inlet temperatures and flow rates of heat transfer fluid (HTF). Experimental results show that the heat transfer augmentation is more sensitive to increase in HTF inlet temperature as compared to increase in mass flow rate of HTF. Solidification time has been observed to reduce up to 43.6% by installation of three fins.