Collector Length Research Articles

A New Conversion Section for Parabolic Trough - Concentrated Solar Power (CSP-PT) Plants

One of the most important challenges facing our future is the balance between energy needs and production, in the framework of the CO2 commitments almost universally adopted. The total energy consumption is still a prerogative of fossil fuels, with a share close to 90%, [1]; renewable energy, apart from the energy production from hydro, photovoltaic, biomass, waste and others, counts 3-4% since many years ago. This discouraging result calls for new conversion technologies based on renewables, if the concept of sustainability is really adopted.Concentrated Solar Power (CSP) plants technology could make the difference with respect to the other renewable technologies, thanks to “bridity”n combining the concentrated solar energy source and the conventional power generation (actually steam turbine plants as energy conversion section). In the sector of energy production, parabolic trough (PT) type is more promising.Recently, the Authors showed in [2,3] how convenient could be the utilization of gases as Heat Transfer Fluid (HTF) with advantages from a technological point of view in the heat collector section and, mainly, from the conversion section point of view, having the possibility to use gas turbines in which the HTF directly expands.In this work, the Authors discuss some thermodynamic and engineering aspects concerning the use of gases as HTF, limiting the attention to air and CO2 and they further discuss the performances of an innovative gas turbine power plant. It is based on a sequence of compressions and expansions, intercooled and reheated (inside linear solar receivers) respectively, in order to increase cycle specific work and efficiency. The paper focuses the attention on the optimum number of compressions and expansions: when it changes, pressure levels change too, requiring a series of reheating processes which operate in parallel, so increasing the overall solar receiver length and, definitively, investment costs. The optimization has been done adopting as design parameter the power per unit of collector length [kW/m], which is the most sensible parameter defining investment cost.

Optimum Settings for a Compound Parabolic Concentrator with Wings Providing Increased Duration of Effective Temperature for Solar-Driven Systems: A Case Study for Tokyo

We designed a compound parabolic concentrator (CPC) with wings angled toward the east and west. Normally, solar collectors are straight, facing south, and the effective temperature is only achieved for a short period of time at midday. In the proposed design, the collector is divided into three parts, with the ends angled and tilted at different orientations. The objective was to increase the duration of the effective temperature period by capturing the maximum solar energy in the morning and afternoon without tracking by the collector. A simulation model was developed to evaluate the performance of the proposed CPC. The tilt and bending angles of the CPC wings were optimized for year-round operation in Tokyo, Japan. A 35° tilt for the south-facing central part of the CPC and a 45° tilt for the wings with 50° angles toward the east and west were found to be optimal. Analyses were conducted at these optimum settings with temperatures of 70, 80, and 90 °C as minimum requirements. The effective duration increased by up to 2 h in the winter and up to 2.53 h in the summer using the proposed CPC. The proposed CPC will improve the efficiency of solar-driven systems by providing useful heat for longer periods of time with the same collector length and without the need for tracking.

Performance and cost benefits analysis of double-pass solar collector with and without fins

The performance and cost benefit analysis of double-pass solar collector with and without fins have been conducted. The theoretical model using steady state analysis has been developed and compared with the experimental results. The performance curves of the double-pass solar collector with and without fins, which included the effects of mass flow rate and solar intensity on the thermal efficiency of the solar collector, were obtained. Results indicated that the thermal efficiency is proportional to the solar intensity at a specific mass flow rate. The thermal efficiency increased by 9% at a solar intensity of 425–790W/m2 and mass flow rate of 0.09kg/s. The theoretical and experimental analysis showed a similar trend as well as close agreement. Moreover, a cost-effectiveness model has been developed examine the cost benefit ratio of double-pass solar collector with and without fins. Evaluation of the annual cost (AC) and the annual energy gain (AEG) of the collector were also performed. The results show that the double-pass solar collector with fins is more cost-effective compared to the double-pass solar collector without fins for mass flow rate of 0.01–0.07kg/s. Also, simulations were obtained for the double-pass solar collector with fins at Nusselt number of 5.42–36.21. The energy efficiency of collector increases with the increase of Nusselt number. The results show that by increasing the Nusselt number simultaneously would drop the outlet temperature at any solar intensity. Increase in Nusselt number causes an increase in energy efficiency. On the other hand, the exergy efficiency has been obtained, which the fluctuation of exergy efficiency was based on the Nusselt number, collector length and solar intensity level.

Double Pass Solar Air Heater with Transvers Fins and without Absorber Plate

The single pass solar air heater, with transverse fins and wire mesh used as an absorber plate, is constructed and tested for thermal efficiency at a geographic location of Cyprus in the city of Famagusta. The absorber plate was replaced by sixteen steel wire mesh layers, 0.18 x 0.18cm in cross section opening and a 0.02cm in diameter. The fins were painted with black color and positioned transversely along the bed such that four equally spaced sections were created. The transversely fins are arranged in a way to force the air to flow through the bed like eight letter path. The obtained results show that for air mass flow rate rang between 0.011-0.032 kg/s, the thermal efficiency increases with increasing the air mass flow. The maximum efficiency obtained is 58% for the mass flow rate of 0.037 kg/s. Moreover, the temperature difference between the outlet flow and the ambient, ΔT, reduces as the air mass flow rate increases. The maximum difference between the outlet and ambient temperature obtained was 40.6 o C for mass flow rate of 0.011kg/s. Comparison with a conventional single pass collector shows a substantially enhancement in the thermal efficiency. INTRODUCTION: Heating air with solar energy is much cleaner than heating with fossil fuel, the delivered heat from air solar device can be used for drying agricultural products such as crop, grains, seeds, fruits, and vegetables. Solar air heaters are also used as pre heaters in industries and as auxiliary heaters in building to save energy during winter times [1]. Conventional solar air heaters mainly consist of panels, insulated hot air ducts and air blowers in active systems. The panel consists of an absorber plate and a transparent cover. There are many different parameters affecting on the solar air heater efficiency, e.g. collector length, collector depth, type of absorber plate, glass cover plate, wind speed, etc. [2]. The absorber plate area and heat transfer coefficient between the air and the absorber plate are two important parameters affecting the efficiency of the collector. When increased these parameters will increase the collector efficiency. On the other hand it will increase the pressure drops inside the solar air heater and increases the pumping power required [2]. The convective heat transfer rate between air flow and absorber plate could be augmented by increasing the absorber surface area and by increasing turbulence inside the bed [3]. The use of Vgroove absorber was found to be more efficient by 12% than the flat plate collector of similar design [4] [5]. Using corrugated plates is a suitable method to increase the thermal performance and provides higher compactness [6]. A mathematical model that allows the determination of the thermal performances of the single-pass solar air collector with offset rectangular plate fin absorber plate is developed by [7]. Experimental and theoretical investigations are carried out on sheet metal absorber in the form of a chevron pattern [8]. The effect of using absorber plates coated with various selective coating materials on the heater performance was also investigated by [9]. Comparisons were made among four types of solar air collectors by Suleyman [10]. It has been found that the performance of a solar air heating system can be improved by operating several sub collectors in series in place of a single large collector with the same total area [11] [12]. The study concludes that the performance of solar air heater with single plastic glazing and flat plate absorber were approximately 9% more than the collector with double plastic glazing. Another study was carried out to determine the comparative performance of one-pass for fixed and free fins,

A Parametric Study of a Natural Flow Solar Air Heater with a Rectangular Air-Duct Profile

This article presents a theoretical analysis of a solar air heater (SAH) with a rectangular air duct profile operated in a natural airflow mode. The study involves modelling the SAH system and simulated results are used to study the effects of various operating conditions and design parameters on its performance. The results show that an increase in the mass flow rate, solar insolation and collector length increases the efficiency of the SAH system. Optimal values of efficiency are obtained when the mass flow rate is greater than 0.01 kgs−1, solar insolation is greater than 1000 W/m2 and with a collector length of between 1.5 and 2.0 m. It is also observed that the efficiency of the collector decreases with increasing channel depth, showing that better performances of the collector are obtained at small channel depths but this results in an increase in the pressure drop which requires more pumping power.

Analysis of the Energetic Feasibility of Parabolic Trough Collectors Integrated in Solar Towers in Adrar Area

In solar energy, the parabolic trough collector plays a capital role in the production of the high temperatures, great than 250°C. Being very robust and with a lifetime relatively rather long, the parabolic trough collectors are used to produce the electricity in the solar towers in the Adrar area, in Algerian Sahara, witch characterized by a high density of sunning 71.259 KWh/m2.yr. In order to analyze its profitability, we proceeded to the mathematical modeling of the various elements of the parabolic trough collector to lead to the advection equation by the recourse to the thermal balances in transient regime. A program, in language FORTRAN 90, was written to solve the system of algebraic equations system, deduced from the discretization method of the model equations. For one day typical and a volumetric flux of 0.6m/h, the simulation results highlighted a significant profit in temperature at the level of the refrigerant which could reach 200°C. Also, it was highlighted the impact of the sunning intensity and the collector length on the absorber temperature, T1. The temperatures distributions in the absorber wall, T2, and that of the envelope in glass, T3, were calculated and we showed that its shape follows a Gaussian law whose the peak is reached in neighborhoods’ noon. Such a temperature has a consequence on the vapor production, with a pressure to 18 bars, capable to convey the turbine intended for generation of electricity. In addition, the program enabled us to examine the influence of the rate flow of refrigerant on the diurnal distribution of its temperature at outlet of the absorber tube.

Bounded Relay Hop Mobile Data Gathering in Wireless Sensor Networks

Recent study reveals that great benefit can be achieved for data gathering in wireless sensor networks by employing mobile collectors that gather data via short-range communications. To pursue maximum energy saving at sensor nodes, intuitively, a mobile collector should traverse the transmission range of each sensor in the field such that each data packet can be directly transmitted to the mobile collector without any relay. However, this approach may lead to significantly increased data gathering latency due to the low moving velocity of the mobile collector. Fortunately, it is observed that data gathering latency can be effectively shortened by performing proper local aggregation via multihop transmissions and then uploading the aggregated data to the mobile collector. In such a scheme, the number of local transmission hops should not be arbitrarily large as it may increase the energy consumption on packet relays, which would adversely affect the overall efficiency of mobile data gathering. Based on these observations, in this paper, we study the tradeoff between energy saving and data gathering latency in mobile data gathering by exploring a balance between the relay hop count of local data aggregation and the moving tour length of the mobile collector. We first propose a polling-based mobile gathering approach and formulate it into an optimization problem, named bounded relay hop mobile data gathering (BRH-MDG). Specifically, a subset of sensors will be selected as polling points that buffer locally aggregated data and upload the data to the mobile collector when it arrives. In the meanwhile, when sensors are affiliated with these polling points, it is guaranteed that any packet relay is bounded within a given number of hops. We then give two efficient algorithms for selecting polling points among sensors. The effectiveness of our approach is validated through extensive simulations.

Heat transfer in a low latitude flat-plate solar collector

Study of rate of heat transfer in a flat-plate solar collector is the main subject of this paper. Measurements of collector and working fluid temperatures were carried out for one year covering the harmattan and rainy seasons in Port Harcourt, Nigeria, which is situated at the latitude of 4.858oN and longitude of 8.372oE. Energy balance equations for heat exchanger were employed to develop a mathematical model which relates the working fluid temperature with the vital collector geometric and physical design parameters. The exit fluid temperature was used to compute the rate of heat transfer to the working fluid and the efficiency of the transfer. The optimum fluid temperatures obtained for the harmattan, rainy and yearly (or combined) seasons were: 317.4, 314.9 and 316.2 [K], respectively. The corresponding insolation utilized were: 83.23, 76.61 and 79.92 [W/m2], respectively, with the corresponding mean collector efficiency of 0.190, 0.205 and 0.197 [-], respectively. The working fluid flowrate, the collector length and the range of time that gave rise to maximum results were: 0.0093 [kg/s], 2.0 [m] and 12PM - 13.00PM, respectively. There was good agreement between the computed and the measured working fluid temperatures. The results obtained are useful for the optimal design of the solar collector and its operations.

Numerical simulation of concentrating solar collector P2CC with a small concentrating ratio

Solar energy may be practically utilized directly through transformation into heat, electrical or chemical energy. A physical and mathematical model is presented, as well as a numerical procedure for predicting thermal performances of the P2CC solar concentrator. The demonstrated prototype has the reception angle of 110? at concentration ratio CR = 1.38, with the significant reception of diffuse radiation. The solar collector P2CC is designed for the area of middle temperature conversion of solar radiation into heat. The working fluid is water with laminar flow through a copper pipe surrounded by an evacuated glass layer. Based on the physical model, a mathematical model is introduced, which consists of energy balance equations for four collector components. In this paper, water temperatures in flow directions are numerically predicted, as well as temperatures of relevant P2CC collector components for various values of input temperatures and mass flow rates of the working fluid, and also for various values of direct sunlight radiation and for different collector lengths. The device which is used to transform solar energy to heat is referred to as solar collector. This paper gives numerical estimated changes of temperature in the direction of fluid flow for different flow rates, different solar radiation intensity and different inlet fluid temperatures. The increase in fluid flow reduces output temperature, while the increase in solar radiation intensity and inlet water temperature increases output temperature of water. Furthermore, the dependence on fluid output temperature is determined, along with the current efficiency by the number of nodes in the numerical calculation.

Simulations of geometry effects and loss mechanisms affecting the photon collection in photovoltaic fluorescent collectors

Monte-Carlo simulations analyze the photon collection in photovoltaic systems with fluorescent collectors. We compare two collector geometries: the classical setup with solar cells mounted at each collector side and solar cells covering the collector back surface. For small ratios of collector length and thickness, the collection probability of photons is equally high in systems with solar cells mounted on the sides or at the bottom of the collector. We apply a photonic band stop filter acting as an energy selective filter which prevents photons emitted by the dye from leaving the collector. We find that the application of such a filter allows covering only 1% of the collector side or bottom area with solar cells. Furthermore, we compare ideal systems in their radiative limits to systems with included loss mechanisms in the dye, at the mirror, or the photonic filter. Examining loss mechanisms in photovoltaic systems with fluorescent collectors enables us to estimate quality limitations of the used materials and components.

Theoretical Analysis of Solar Thermal Collector with a Flat Plate Bottom Booster Reflector

A theoretical analysis of a solar thermal collector with a flat plate bottom reflector is presented. The bottom reflector extends from the lower edge of the collector. The variations of daily solar radiation absorbed on the collector with inclinations from horizontal for both the collector and reflector throughout the year were predicted, and the optimum inclinations of the collector and reflector which maximize the daily solar radiation absorbed on the collector were determined for each month at 30 o N latitude. The effects of the size of the collector and reflector on the daily solar radiation absorbed on the collector were also investigated. The optimum collector inclination is lower in summer and higher in winter, while the optimum reflector inclination is higher in summer and lower in winter. The average daily solar radiation absorbed on the collector throughout the year can be increased about 20%, 27% and 33% by using a bottom reflector if the ratio of reflector length to collector length is 0.5, 1.0 and 2.0, respectively, when the collector’s length is equal to its width. Key words: Solar energy; Solar thermal collector; Bottom reflector; Collector-reflector; Optimum inclination

Energy and Exergy Analysis of a Photovoltaic-Thermal Collector With Natural Air Flow

The objective of present work is to analyze the energy and the exergy performance of a naturally ventilated photovoltaic-thermal (PV/T) air collector which is designed, manufactured and tested at a geographic location of Kerman, Iran. This PV/T collector is tested in both glazed and unglazed types. In this system, a thin metal sheet is used to improve heat extraction from the PV panels and consequently achieving higher thermal and electrical output. The metal sheet is suspended at the middle of an air channel in the studied PV/T air configuration. A theoretical model is developed and validated against experimental data, where good agreement between the predicted results and measured data is achieved. The validated model is then used to study the effect of the solar radiation, channel depth, collector length, and PV cell efficiency on total energy and exergy efficiency of the studied system.

Deflective Behavior of Charged Particles in a Two-Stage Electrostatic Precipitator

Even if smoke, fumes, mist or dust particles are removed by electrostatic precipitators (ESPs), the occurrence of ozone, which is harmful to human body, has to be severely restricted in the indoor environments of hospitals, offices, and workshops. Therefore, the two-stage ESP generating positive corona at the ionizer is typically used because it creates less ozone than the two-stage ESP generating negative corona at the ionizer.<BR> In order to predict the collection performance and the optimal design of the two-stage ESP applied to positive high-voltage, particle concentration is experimentally investigated in this paper. In addition, particle motion within the collector section is also numerically analyzed.<BR> The positive corona discharge current of the ionizer is found to be affected by the applied voltage in the collector section but less so by the particle concentration. Particle concentration shows a minimum near the high voltage electrode of the collector section. The minimum value of the collection efficiency is almost proportional to gas velocity. When the collector length decreases, the minimum value of the collection efficiency increases. Charged particles entering the collector region are linearly deflected towards the grounded plate by an electric field.<BR> From the above experimental and numerical results, two empirical equations on the concentration ratio and the collection efficiency are derived, and are in good agreement with the experimental data.

Measuring efficiency of positive and negative ionic wind devices for comparison to fans and blowers

Abstract Many industries are pursuing alternate air moving devices to reduce the power consumption of their air cooled products. The literature suggests that ionic AMDs have low efficiency. The literature, however, does not define efficiency the same way the computer industry defines it for rotary AMDs. In this study, static efficiency of ionic AMDs was evaluated similar to rotary AMDs. Various emitter to collector distances and various ring lengths, were evaluated for positive and negative coronas. By controlling emitter to collector distance and collector length, efficiencies were obtained more reasonably compared to rotary devices.

Energy and exergy analysis of an indirect solar cabinet dryer based on mathematical modeling results

In the present study, using a previously developed dynamic mathematical model for performance analysis of an indirect cabinet solar dryer [1], a microscopic energy and exergy analysis for an indirect solar cabinet dryer is carried out. To this end, appropriate energy and exergy models are developed and using the predicted values for temperature and enthalpy of gas stream and the temperature, enthalpy and moisture content of the drying solid, the energy and exergy efficiencies are estimated. The validity of the model for predicting variations in gas and solid characteristics along the time and the length of the solar collector and/or dryer length was examined against some existing experimental data. The results show that in spite of high energy efficiency, the indirect solar cabinet dryer has relatively low exergy efficiency. Results show that the maximum exergy losses are in midday. Also the minimums of total exergy efficiency are 32.3% and 47.2% on the first and second days, respectively. Furthermore, the effect of some operating parameters, including length of the collector, its surface, and air flow rate was investigated on the exergy destruction and efficiency.

Development of Micro-Flame Ionization Detector for Portable Gas Chromatograph

Abstract A micro-flame ionization detector (μ-FID) was developed and evaluated. Its key structure parameters, such as the material and inner diameter of the jet tip, the length of collector, the distance between jet tip and collector, polarization voltage, and gas flow rate, were discussed in detail. Compared with traditional FID, the gas consumption of μ-FID decreased 70%, and only two kinds of gases (hydrogen and air) were needed. The μ-FID is an excellent detector for portable gas chromatograph due to its small size, simple structure, good sensitivity, and easy-to-construct nature. The μ-FID was applied to analyze five phenolic compounds in real water samples.

Numerical Simulation of Solar Absorption Machine

Abstract An analytical study is to performed on solar energy utilization in space cooling using a solar lithium bromide absorption system. The introduction presents the importance, the availability and the applications of solar energy, followed by a description for solar absorption machine [1] , [2] . Matlab numerical simulation of this system illustrates the change of the temperatures in the main parts starting from the collector since the temperatures change with the variation of the heat flux density provided from the sun. The temperature changes only in the part of heat exchanger collector and the idle heat exchanger where as in all other part. An electric source is required to ensure the necessary heat that when the solar heat flux does not supply the total air conditioning load. Finally the paper is concluded by studying the variation of solar flux in three cities, the collector length and the auxiliary source required in each city.

Solar thermal collector augmented by flat plate booster reflector: Optimum inclination of collector and reflector

In this report we present a theoretical analysis of a solar thermal collector with a flat plate top reflector. The top reflector extends from the upper edge of the collector, and can be inclined forwards or backwards from vertical according to the seasons. We theoretically predicted the daily solar radiation absorbed on an absorbing plate of the collector throughout the year, which varies considerably with the inclination of both the collector and reflector, and is slightly affected by the ratio of the reflector and collector length. We found the optimum inclination of the collector and reflector for each month at 30°N latitude. An increase in the daily solar radiation absorbed on the absorbing plate over a conventional solar thermal collector would average about 19%, 26% and 33% throughout the year by using the flat plate reflector when the ratio of reflector and collector length is 0.5, 1.0 and 2.0 and both the collector and reflector are adjusted to the proper inclination.

Thermofluidynamic Model and Comparative Analysis of Parabolic Trough Collectors Using Oil, Water/Steam, or Molten Salt as Heat Transfer Fluids

This paper describes the development and use of a thermofluidynamic model for parabolic trough collectors, specifically suited for carrying out systematic calculations on different design options. The model is based on detailed energy balances, and it has been applied to evaluate collector thermal performances with different working fluids: oil, molten salt, or water/steam. For each heat transfer fluid technology, four parameters have been analyzed: collector length, absorber tube diameter, working temperature, and pressure. The influence of these factors has been studied from the point of view of heat loss, pressure drop, energy, and exergy efficiencies. Exergy is considered the suitable magnitude to guide any optimization process in this field, because it accounts for all relevant energy gains and losses, characterized by their corresponding temperature and pressure. Preliminary conclusions point out that direct steam generation is more efficient than oil and molten salt systems.

The experimental response and modelling of a solar heat collector fabricated from plastic microcapillary films

This paper reports experimental data from, and numerical modelling of, plastic solar collectors fabricated from a novel thermoplastic extrudate. The extrudate, termed as microcapillary film (MCF), consists of an extruded flexible, plastic, film with a parallel array of hollow capillaries running along the film’s length. Experimental investigations were carried out on two laboratory scale solar collectors, illuminated with an infrared lamp, to determine the effects that different process fluids, glazing layers and collector backgrounds had on the overall heat recovery of the collector. The experiments also examined the effects that fluid flow rate, collector length and capillary wall thickness had on the heat recovery. Heat recovery of a similar order of magnitude to commercially available collectors was attained. A finite difference model was developed to calculate the temperature gain and the heat recovery of these solar collectors as a function of design and operating parameters. This model was successfully validated against experimental data, and was able to quantitatively predict the performance of these devices. Results from this investigation suggest that MCFs perform heat exchange duties of this type well, with the potential to make a low-cost, lightweight, mechanically flexible, solar collector.