Collector Configurations Research Articles

Surface interactions and flotation behavior of calcite, dolomite and ankerite with alkyl hydroxamic acid bearing collector and sodium silicate

The surface interactions and adsorption mechanism of alkyl hydroxamic acid bearing collectors and sodium silicate depressant on common carbonatite gangue minerals, including calcite, dolomite and ankerite in flotation were investigated. For this purpose, firstly the flotation behaviors of these minerals in the presence of the collector and depressant were investigated via micro-flotation tests at pH 7–9.5. Meanwhile, the interaction nature of this collector and depressant with minerals was disclosed through FTIR and zeta potential measurements over the studied pH range. It was found that either floatability of minerals in the presence of collector or the affinity of minerals towards collector and depressant adsorption are in the order of ankerite >> calcite dolomite. The nature of collector-minerals’ interactions and also the collector’s adsorption mechanism were further studied via density functional theory (DFT) simulations to identify the likeliest collector configurations and adsorption pathways of collector and depressant on the mineral surfaces. It was concluded that ankerite has higher affinity towards alkyl hydroxamic acid collector and also sodium silicate as compared with calcite and dolomite. It was revealed that collector is going to interact with metal atoms on the minerals surfaces via covalent bonding through which bridged and monodentate binding configuration are more favorable. It was found that Fe atoms on the mineral surfaces are more involved in bond formation as compared with Ca and Mg. The DFT simulations also indicated that sodium silicate has more affinity towards ankerite which was confirmed via experimental observations. Besides, the surface interaction pathway of both SiO(OH)3− and Si(OH)4 as dominated silicate monomers in aqueous phase on the mineral surfaces were demonstrated. It was found SiO(OH)3− species enable either covalent or hydrogen bonding on the mineral surfaces, while Si(OH)4 species are likely to interact with minerals only through hydrogen bonding. Therefore, SiO(OH)3− species are corroborated to prompt more important depressant effects on froth flotation of carbonatite gangue minerals.

Comparison of heat sink and water type PV/T collector for polycrystalline photovoltaic panel cooling

Abstract Cylindrical pin fin heat sinks are not used to cool a panel, which we have done so in the present work and tested it's performance against a traditional single-channel PV/T collector. An older 20 Watt polycrystalline solar cell photovoltaic panel with a standard efficiency of 11.7% is elevated to a high temperature by indoor halogen light of intensity 1378.4 W m−2 in this study. The temperature of 81.7 ± 2.3 °C temperature at the front and 88.6 °C at the rear under at 0 m2 s−1 wind speeds are lowered using a cylindrical pin fin heat sink (fin density 1.22 fin cm−2). A channel of aspect ratios α* = 0.08 was attached to the rear of the panel as the collector configuration. Temperatures dropped to 58.4 °C with heat sink and 47.9° using the collector. The analysis suggests that heat flux of 667.2 W m−2 at the rear of the bare panel with no cooling is enhanced by 30 and 41.5% by the heat sink and PV/T collector by natural methods. We strongly urge exploration of using the cylindrical pin fin heat sinks to cool the panel under stagnant wind conditions.

Photovoltaic thermal hybrid solar collector and district heating configurations for a Central European multi-family house

In central European countries, district heating is a common and standard way to cover the residential heat demand. While the consumers are connected to the heat network and electricity grid, they are being increasingly encouraged to become prosumers by having own distributed renewable energy generation. At the same time, the energy performance requirements for new and renovated buildings are setting progressively higher energy efficiency standards. This tendency is effectively reducing the carbon footprint of the residential sector in Central Europe and will eventually lead to low and zero carbon buildings becoming the standard. One of the emerging technologies within this approach are Photovoltaic thermal hybrid solar collectors, which combine heat and power generation and are easy to integrate in buildings. In this study, the possibility to use such a system, supported by a heat pump, in a Central European multi-family house is addressed. Three configurations are considered; the building, the hybrid and district heating configuration. In the building configuration the heat from the solar collectors is used directly for domestic hot water and space heating and no use is made of excess heat. In the hybrid configuration, the direct heat consumption in the building is prioritized, while excess heat is exported to the district heating network. Finally, in the district heating configuration, the solar system operates as a micro-plant that supplies all produced heat to the district heating network. The study shows that the use of Photovoltaic thermal hybrid solar collectors in combination with district heating provides important benefits in terms of sustainability, energy security, carbon abatement and costs. Thereby, configurations that can export heat to the network have better energy efficiency and result more profitable.

The effect of Joule heating to thermal performance of hybrid PVT collector during electricity generation

The aim of this paper is to discuss the performance of a hybrid photovoltaic and thermal (PVT) collector by focusing on the utilization of Joule heating as additional heat for improving thermal efficiency, when both thermal and electrical energies are generated (PVT-mode), by comparing with when only the thermal energy is generated (T-mode). During the maximum power point and the peak irradiation, the temperature differential in PV material was increased due to the rise in current flow. The Joule heating or internal heating also increased proportional to the square of electric current. The conducted heat also increases through the PV surface to the thermal absorber in the PVT collector. For that reason, the experiment was performed using higher irradiation with a bigger PVT collector at four different inlet water temperatures, i.e., 12, 15, 20, and 25 °C. The water flow rate was 6.7 × 10−5 m3/s (≈4 L/minute). The irradiation data was collected for an hour from 12:00 to 13:00 to keep a steady-state thermal performance and also to minimize the hysteresis effect. In the present PVT collector's system and configuration, the result showed that even a moderate wind speed below 1 m/s results in a non-negligible loss of the thermal efficiency. The thermal efficiency of PVT collector in PVT-mode is higher than T-mode at the lower range of first order thermal efficiency gradient, when the inlet water temperature is close to the ambient air temperature, or when the total irradiation is high. The behavior of the thermal efficiency of PVT-mode also seems to be appreciably influenced by other factors, such as the internal heating during the operation. During the higher irradiation periods, the Joule heating effect has the potential to improve the thermal efficiency of PVT-mode up to 13%. The internal heating in PV cell apparently affects both the effective absorption and heat loss coefficient. The practical relevance of Joule heating in a real-life PVT system is for low temperature applications, such as swimming pool heating, low temperature source heat pumps, and floor heating.

Design Optimization of a Sorption Integrated Sydney Type Vacuum Tube Collector

In order to reach the targets on emissions set by the European Commission, both new and existing buildings must reduce their fossil fuel inputs. Solar thermal cooling supplying on-site renewable heating and cooling could potentially contribute toward this goal. In this paper, a novel concept for solar thermal cooling providing efficient coproduction of cooling and heating based on sorption integrated vacuum tube collectors is proposed. A prototype collector has been constructed and tested in a solar laboratory based on a method developed specifically for sorption integrated collectors. From the test results, the key performance parameters have been determined and used to calibrate a mathematical model for trnsys environment. System simulation has been conducted to optimize the collector and sorption module configuration by performing a parametric study where different vacuum tube center–center (C–C) distances and sorption module designs are tested for a generic hotel in Ankara, Turkey. The parametric study showed that the heating and cooling output per year can be as high as 1000 kWh/m2 for solar fractions above 50%, and that the output per sorption module compared to the prototype can more than double with an optimized design. Furthermore, cooling conversion efficiencies defined as total cooling output per total solar insolation can be as high as 26% while simultaneously converting 35–40% of the incident solar energy into useful hot water.

View Factors to Grounds of Photovoltaic Collectors

Ground reflected radiation is one component of the global radiation on photovoltaic collectors in a solar field. This component depends on the view factor of the collector to ground, hence depends on the relative position of the collectors to each other. General analytical expressions and numerical values for the view factor to the ground were developed between flat-plate collectors positioned in a general configuration. Based on the general expression, the view factors to ground for particular collector configurations were derived. For deployment of photovoltaic collectors in multiple rows with common inclination angles, the view factor to ground is rather small, and hence, the reflected radiation from the ground on the collectors may be neglected compared to the direct beam and the diffuse components. However, in some cases the reflected radiation from the ground may constitute an appreciable amount as in snowy area. Bifacial photovoltaic (PV) panels can absorb solar radiation by both the front and the rear sides and are usually deployed vertically. In this case the reflected radiation from the ground on the panels may be appreciable depending on the ground albedo. The mathematical expressions of the different view factors may be used by the solar field designer to estimate the amount of reflected radiation from the ground reaching the collectors for different configurations of solar PV plants.

CFD (computational fluid dynamics) analysis of a solar-chimney power plant with inclined collector roof

This paper presents a computational fluid dynamics study on a solar-chimney power plant with an inclined collector roof. A three-dimensional model using the RNG (Re-Normalisation Group) k−ε turbulence closure is simulated. The discrete ordinates non-gray radiation model is used to implement the radiative-transfer equation. To simulate solar irradiation, the solar ray-tracing algorithm is employed. A parametric study is performed to illustrate the effect of the collector configuration on the performance of the Manzanares power plant. In this approach, the roof inclination is adjusted by increasing the outlet collector height, while the inlet collector height is fixed to the height of the collector of the Manzanares solar chimney pilot plant. The results showed that changes in the collector-roof inclination affect the convection pattern through the collector, which results in an increase in the mass flow rate of the system.

Numerical and experimental study of a corrugated thermal collector

The present work proposes a design for solar thermal collectors and also a numerical simulation analysis procedure to evaluate the collector performance. The performance of this collector is compared with the performance of other two commercial ones by observing both the numerical modeling study and experimental test results. Benefits of using the corrugated parallel approach, in terms of yield, are shown applying a new alternative approach of numerical modeling. A better performance is observed for the corrugated parallel collector, which provides a higher yield using an energy-absorbing surface. Moreover, the proposed numerical methodology could be used to evaluate the performance of other thermal collector configurations.

Study and modeling of energy performance of a hybrid photovoltaic/thermal solar collector: Configuration suitable for an indirect solar dryer

In this paper, a configuration of photovoltaic-thermal hybrid solar collector embeddable in an indirect solar dryer system is studied. In the present structure of the solar photovoltaic/thermal air collector, the air goes through a double pass below and above the photovoltaic module. A system of electrical and thermal balance equations is developed and analyzed governing various electric and heat transfer parameters in the solar hybrid air collector. The numerical model planned for this study gives a good precision of results, which are close to the experimental ones (of previous literature), and makes it possible to have a good assessment of energy performance regarding the studied configuration (temperature, electric and thermal powers, electrical and thermal efficiencies, etc.). The numerical results show the energy effectiveness of this hybrid collector configuration and particularly its interesting use in an indirect solar dryer system that provides a more suitable air temperature for drying agricultural products. The values of the electrical, thermal and overall energy efficiencies reaches 10.5%, 70% and 90% respectively, with a mass flow rate of 0.0155kg/s and weather data sample for the month of June in the Algiers site. The results presented in this study also reveal how important the effect of certain parameters and operating conditions on the performance of the hybrid collector.

Performance improvement of adsorption solar cooling system

This paper presents the study of a tubular adsorber of solar adsorption cooling machine, driven by flat-type solar collector with three different configurations of glazes: (i) single glazed cover, (ii) double glazed cover and (iii) transparent insulation material (TIM) cover. The modelling and the analysis of the adsorber are the key point of such studies, because of the complex coupled heat and mass transfer phenomena that occur during the working cycle. The adsorber is heated by solar energy and contains a porous medium constituted of activated carbon AC-35 reacting by adsorption with methanol.The simulation technique takes into account the variation of ambient temperature and solar intensity along a simulated day, which corresponds to a total daily insolation of 26,12 MJ/m2 and an average ambient temperature of 27.7 °C. The obtained solution allows to know the daily thermal behaviour of a tubular adsorber. The model is used to study the influence of the solar collector type and its surface on the system's performances COPth and COPs (thermal and solar performance coefficient, respectively). It is found that the type of collector configuration and its surface have a big difference on the system's performance.

Effects of shading and blocking in compact linear fresnel reflector field

In a compact linear fresnel reflector field, ‘s’ number of reflector-rows lying between two receivers can be configured in 2s ways. Each possible configuration will lead to different energy loss, electricity generation and cost of electricity. The variations in energy losses, energy collection by fluid, electricity generation and cost of electricity with length (L) and width (w) of aperture of a reflector-row, spacing between adjacent reflector-rows (p), number of reflector-rows (2n), receiver-height (H), collector-configuration and location have been studied. It is found that the collector configuration has no significant effect on annual shading. However, it affects annual energy losses due to cosine effect, blocking and the factors τ and α significantly. As a result, the cost of electricity can be improved significantly by varying collector configuration. The cost of electricity decreases with increment in p/w and later on, it starts increasing. The best p/w ratio corresponding to minimum cost of electricity is 1.44 for H/nw = 0.3 and 1.85 for H/nw = 0.7. The energy collection by fluid increases rapidly with increment in H/nw initially. However, beyond H/nw about 0.7, further increase in H/nw does not lead to significant increase in energy collection.

A quasi-dynamic simulation model for direct steam generation in parabolic troughs using TRNSYS

This work describes and evaluates a new simulation model for direct steam generation in parabolic-trough solar collectors. In direct steam generation, water is heated and evaporated through a solar field to feed a steam Rankine cycle or an industrial process. However, the behaviour of the involved multiphase fluid poses some challenges to simulation models. The model explained in this work is based on a steady-state approach but deals with transient conditions such as start-up, shutdown and clouds in a reasonable computing time. A new simulation tool is implemented in the TRNSYS software environment by means of new components that are suitable to be integrated into a whole solar plant model in order to carry out long-term energy production analyses with low computational resources. The main advantages of the new quasi-dynamic approach include fast computation with satisfactory accuracy; consideration of thermal inertia when addressing transient conditions; and flexibility to use different types of collector or solar field configurations. The performance of the model is validated with real experimental data obtained from the DISS solar test loop in Plataforma Solar de Almería, Spain. This paper describes the modelling approach and summarizes the comparison of simulation results with measurements taken at the DISS facility.

Performance Analysis and Design of Liquid Based Solar Heating System

Designing of a solar heating system involves appropriate sizing of different components based on predicted solar insolation and heating load demand. But, it is a complex problem due to unpredictable weather data components. A number of design methods are available for solar heating systems. In this paper, f-chart method has been used due to its simplified design procedure, analysis and low cost in selecting the sizes and type of solar collectors and in estimating the annual thermal performance of solar heating system. Using this method, the design of liquid solar heating system and the estimation of the fraction of total heating load (domestic water and space heating load) that will be supplied by solar energy for a family of six in Riyadh have been conducted. The study includes the effect of different collector areas and storage capacity per square meter of collector area and collector tilt angle on fraction of the load supplied by solar energy. It has been found that increasing the collector area results in an increasing of annual load fraction supplied by solar energy. It has also been seen that increasing the specific storage capacity results in small increase in solar load fraction and the effect is more visible during the summer than during the winter. The result of the study reveals that collector configurations with lower tilt angles are better during the summer and higher values of angles are better during the winter. The optimal annual collector configuration tilt angle which gives the maximum solar load fraction has been found to be 30o

Nitrite/nitrate detection in serum based on dual-plate generator–collector currents in a microtrench

A dual-electrode sensor is developed for rapid detection of nitrite/nitrate at micromolar levels in phosphate buffer media and in dilute horse serum without additional sample pre-treatment. A generator–collector configuration is employed so that on one electrode nitrate is reduced to nitrite and on the second electrode nitrite is oxidised back to nitrate. The resulting redox cycle gives rise to a specific and enhanced current signal which is exploited for sensitive and reliable measurement of nitrite/nitrate in the presence of oxygen.The electrode design is based on a dual-plate microtrench (approximately 15µm inter-electrode gap) fabricated from gold-coated glass and with a nano-silver catalyst for the reduction of nitrate. Fine tuning of the phosphate buffer pH is crucial for maximising collector current signals whilst minimising unwanted gold surface oxidation. A limit of detection of 24μM nitrate and a linear concentration range of 200–1400μM is reported for the microtrench sensor in phosphate buffer and dilute horse serum. Relative standard deviations for repeat measurements were in the range 1.8–6.9% (n=3) indicating good repeatability in both aqueous and biological media. Preliminary method validation against the standard chemiluminescence method used in medical laboratories is reported for nitrate analysis in serum.

Synthesis of Porous 3D Metallic Current Collectors for High Performance Lithium Batteries

Conventional thin film lithium ion batteries are built on a planar design where electrode material is coated on to a conducting current collector substrate. Contact resistance between the current collector and the electrode always hinders the overall performance of the battery. In order to better utilize the electrode material, 3D current collector architectures with nanoscale roughness have been proposed which would increase the electrode-current collector surface contact area thereby significantly reducing interfacial resistance. The nanoporous current collector configuration is one of several 3D designs which have shown high potential for the development of high energy and high power microbatteries. We present here a scalable process for the synthesis of three dimensional porous metallic current collectors with conformal graphene coating on the surface. One step chemical vapor deposition technique has been used for controlled etching and simultaneous graphene growth on the surface of metals such as copper and stainless steel. The 3D structures can be directly used as a cathode in lithium ion battery as graphene has lithium intercalating capability. The structural and morphology of the current collector/electrode hybrid structures were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS) analysis, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The contribution of 3D current collectors resulted in excellent cyclic stability and capacity compared to using conventional 2D configuration.

Rapid prototyping of a miniaturized Electrospinning setup for the production of polymer nanofibers

ABSTRACTFabrication of polymeric micro/nanofibers with controllable size, density, orientation, and composition is required for their translation into functional devices and materials. Electrospinning (ES) is a frequently used fiber fabrication technique, where ES parameters such as the applied electric field strength, architecture of the setup, and solution composition are manipulated to control the fiber properties. Here, we present a bench‐top method for fabricating miniaturized, integrated, and highly tunable ES setups based on shrinkable polymer substrates. We show that using a combination of numerical modeling and controlling different parameters in the ES setup, including the spinneret to collector distance, and spinneret and collector designs, it is possible to tune the density, alignment, and orientation of electrospun fibers. In this way, we have produced 300–600 nm wide poly(ethylene oxide) fibers arranged as nonwoven mats on planar electrodes, aligned fibers on electrode edges, and individual suspended fibers spanning gaps between collector electrodes. The ability to rapidly prototype ES setups should enable us to study the effects of spinneret–collector configurations on fiber morphology, distribution, and conformation and to aid in the development of miniaturized ES setups designed to serve specific applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40629.

Performances and numerical optimization of a novel thermal solar collector for residential building

Abstract A new flat-plate solar collector with high building integration was designed and a prototype of this collector was built. The implemented experimentations showed that the performances of this solar collector can be improved. A numerical thermal model using a finite difference and developed in Matlab® environment was validated. Then, a modelling of the complete solar domestic hot water system (solar collector+water storage+piping) was implemented. The performances of this system were calculated for various solar collector configurations as number and position of water pipes, air layer thickness, thermal insulation thickness… Three solar fractions are defined and used in the optimization procedure. An optimized solar collector structure is finally presented.

A Parametric Study on the Thermal Performance of Unglazed Solar Water Collectors with Their Colorbond Steel Absorber Plates Also Used as Roofs

In this paper, an innovative unglazed solar water collector with its colorbond steel absorber plate also serving as the roof is proposed. Two most common colorbond steel profiles used as roofs, namely the Lysaght BlueOrb colorbond steel with the cosine profile and the Spandek colorbond steel with a trapezoidal shaped profile, are selected as the absorber plates. A theoretical energy balance model is developed to conduct a detailed parametric study on the thermal performance of this innovative unglazed solar collector with both colorbond steel absorber plate profiles under various configuration and operating conditions. The results show that both types of collectors can achieve high thermal efficiency (˜70%) and can increase the water temperature by about 8 °C, indicating they are suitable for the domestic utilization in at least tropical and similar regions as well; The two types of collectors produce very close thermal performances; improved thermal performance can be achieved through optimizing a number of parameters such as using a selective coating for the absorber plate to enhance its optical properties, using slender collector configurations, and using a compromized mass flow rate to maintain a high efficiency and to attain the higher temperature outputs.

Development of an Insulated Glass Solar Thermal Collector

Insulated glass solar thermal collectors result from the insertion of a solar absorber into the outer gap of a multiple glazed unit. Taking advantages from the manufacturing technology of the glass and window industry, a flexible and highly automated production as well as an easier and architecturally more appealing integration into the building envelope is expected. Ensuring long-term functionality, on the other hand, represents a very challenging development task due to high temperatures and to the thermally induced deformations of the solar absorber. The paper analyzes the behavior of this new kind of collector by means of theoretical calculations and experiments, focusing on both the performance and the reliability aspects. Efficiency measurements according to EN 12975 on prototypes with a slim design report specific values comparable to those of standard flat plate collectors (η0 = 0.78, a1 = 3.77W/m2K, a2 = 0.011W/m2K2 for a 50mm thick, argon-filled prototype). Prolonged exposure to stagnation temperature and internal thermal shock-tests attest the durability of collector configurations featuring temperature- resistant components and suitable constructions, able to reduce and compensate the absorber deformation.

A Nonlinear Electric Field Sensor That Exploits Coupled Oscillator Dynamics: The Charge Collection Mechanism

In this paper, we investigate the exploitation of nonlinear behavior in ferroelectric (FE) materials in the realization of innovative transducers for detecting weak and low-frequency electric fields (E-fields). Specifically, we describe a nonlinear dynamical system based on FE capacitors coupled into a unidirectional ring circuit which, under the appropriate operating conditions, exhibits an oscillating regime of behavior in the response variable (the electric polarization). In this device, a weak target E-field induces a perturbation of the polarization of the FE material; in turn, the target signal can be detected and quantified via its effect on the coupled system response. Hence, the device entails the synergetic use of bistable FE materials, micromachining technologies that allow for addressing charge density amplification, and novel sensing strategies based on coupling nonlinear elemental cells. The “charge collector” strategy has been employed to detect the target field. An experimental characterization of the sensing device, including three cells (each cell corresponds to an FE capacitor) coupled in a ring configuration, is presented as a function of the charge collector configuration.