Thermal analysis of black liquid cylindrical parabolic collector

In the present paper a simple theoretical analysis and an experiment are carried out for a modified concentrating collector which consists of a cylindrical parabolic reflector, a transparent glass tube centered along the focal line, and a highly absorbent black liquid which flows in the glass tube to directly absorb the concentrated solar beam radiation. The analytical results are presented in normalized form and proved to be in very good agreement with the experimental results.     

Performance simulation of a parabolic trough solar collector

A new analytical model for optical performance and a modified integration algorithm are proposed and applied to simulate the performance of a parabolic trough solar collector with vacuum tube receiver. The analytical equation for optical efficiency of each point at reflector is derived first, then the optical efficiency of the system is simulated by numerical integration algorithm. The cosine factor, receiver efficiency, heat loss and efficiency of conversion of solar energy into net heat energy at any time can be calculated with the program. The annual average efficiency is also simulated considering discard loss. The effects of optical error, tracking error, position error from installation of receiver, optical properties of reflector, transmittance and absorptivity of vacuum tube receiver on efficiencies of the trough system are simulated and analyzed as well as optical parameter.     

Effectiveness of solar water-lift system with parabolic cylindrical solar energy collector and jet pump

Formulas are presented and a computer calculation program is implemented for determining the energy efficiency of a solar water-lift system module with a parabolic cylindrical collector and a jet pump.     

Simulation and experimental results of a vacuum solar collector system with storage

This article presents the operation of vacuum solar collectors connected to a warm water storage. The layout of the test facility is shown. Simulation of the installation is performed with the help of differential equations that describe the solar collectors and the storage. Thus, the temperatures in the collector loop (at the collector and storage inlets and outlets) and the temperatures in the storage are determined. The developed computer programme calculates the temperatures of the complete system as well as the temperatures in the collector loop and in the storage. A comparison is made between the calculated and experimental data, showing a good concurrence between the two curves.     

Performance investigation of a solar water distiller integrated with a parabolic collector using fuzzy technique

A recent study of the design of solar distillation with solar radiation concentration was carried out by an independent device. Transformer oil was used as a fluid to transfer heat to the distilled basin. The design and operational variables are essential, such as distiller dimensions, concentration ratio, pressure, and temperature. A mathematical model was proposed to simulate the system for 2 July 2018 from 10 am to 4 pm  in the climatic conditions of the city of Kirkuk, Iraq. Fuzzy logic (FL) was used to select the affected parameters: water temperature (T_w), water pressure (P_w), glass temperature (T_g), and vapor pressure (P_g) which have a separated membership function that control the linguistic variables. The results showed that the best performance of the distiller is at T_w = 100°C, P_g = 10 000 Pa, T_g = 20°C, and P_w = 20 000 Pa, and concentration ratio of 30. This study used FL to analyze solar distiller performance and identify optimum temperature, pressure, and concentration ratio on the productivity of solar distiller.     

Simulation and optimisation studies on a solar parabolic collector: an experimental investigation

The present paper has focused on parametric optimisation of a solar parabolic collector. This work has been performed in two phases. In the first phase, simulation studies have been done to identify the influential parameters. Based on simulation results, an experimental set-up of the parabolic collector has been fabricated using the materials selected by priority-score method. In the second phase, experiments are conducted according to Taguchi's L₉ orthogonal array. Parabolic collector parameters, namely reflector materials, absorber materials, positions of the absorber tube and angle of the absorber tube, are optimised with the consideration of multi-responses such as temperature, enthalpy, optical efficiency and thermal efficiency. The obtained experimental data are analysed using the desirability functional analysis approach and optimal levels of input parameters have been identified. Analysis of variance also has been performed to know the contribution of influential parameters on the responses.     

Performance of an intermittently tracked cylindrical parabolic trough

The distribution of local concentration ratios over a flat plate absorber used with an intermittently tracked cylindrical parabolic trough is studied for two values of the rim angle. The amount of energy collected by an intermittently tracked solar concentrator, oriented in various tracking modes, at different times of the year, for two typical latitudes, is also calculated. The results are presented graphically and discussed.     

Performance analysis and experimental validation of a vee-corrugated absorber integrated collector storage solar water heater

This paper focuses on enhancing the energy collection efficiency of an integrated collector storage solar water heater (ICS SWH) by vee-corrugating the absorber and optimizing the design for the vee-included angle through simulation and experimental study. This paper presents an efficient algorithm for analyzing a vee-corrugated absorber ICS SWH using Engineering Equation Solver Software. For validating this algorithm, two models of ICS SWH systems have been fabricated: one with a flat absorber and the other with a 60° vee-included angle corrugated absorber with eight corrugations. The basic purpose of the fabrication of the flat absorber ICS SWH system was to approximate the absorptivity of the absorber. A typical value of 0.68 was estimated for the absorptivity of the aluminum absorber coated with nonselective black paint. After the experimental investigation of the 60° vee-included angle ICS SWH system, it was found that the real-time readings were in close agreement with the numerical model readings. For comparison with the previous work, a five-corrugation system with an approximate 90° vee-included angle with the same projected dimensions was modeled and the efficiencies of both the models for the time from 7 a.m. to 3 p.m. were calculated. The efficiency of the eight-corrugation model was 42.56%, which was better than the previous work of the five-corrugation model, with a 38.86% efficiency for the same ambient conditions. Also, it was theoretically deduced that we had an optimized system at 18 corrugations and a vee-included angle of 28.78°.     

Performance analysis of a solar glass tube collector

The thermal performance and thermal processes of a glass tube collector have been analysed in this paper. Its thermal performance can be improved by changing the thermal processes to take advantage of the glass tube's ability to transmit sunlight; that makes it possible for the working fluid to directly absorb part of solar radiation. Its thermal performance is even better in most parts of the working region than that of a steel tube collector, even when the structure, meteorological conditions and thermodynamic properties of the working fluid are exactly the same.An equation of steady-state instantaneous efficiency of a glass tube collector has been derived in the paper. Calculations of various operating conditions have been made with a computer, and the calculated results are quite agreeable with the experimental results. Thus the equation and the calculation method can be used in the design of glass tube collectors and for comparison calculations. The calculations also show some other important features of a glass tube collector.     

Development of a point focusing collector farm system

A parabolic collector and thermal test loop has been operated and a small solar farm is under construction in Kuwait. Some experiences gained in the analysis and design of solar farm systems are summarized. Derived from this experience, possible future development trends of such farm systems using point focusing paraboloid collectors are outlined.     

Performance of a cylindrical parabolic trough using a fin receiver: Limb darkening effects

The distribution of local concentration ratio on a fin receiver used with cylindrical parabolic solar concentrators has been calculated analytically considering the variation of intensity over the solar disc. The effect of the pointing error of the concentrator and that of the lateral shift and tilt of the fin receiver have also been studied. The results are plotted graphically and discussed.     

Performance analysis of a double-pass thermoelectric solar air collector

The thermoelectric (TE) solar air collector, sometimes known as the hybrid solar collector, generates both thermal and electrical energies simultaneously. A double-pass TE solar air collector has been developed and tested. The TE solar collector was composed of transparent glass, air gap, an absorber plate, thermoelectric modules and rectangular fin heat sink. The incident solar radiation heats up the absorber plate so that a temperature difference is created between the thermoelectric modules that generates a direct current. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the absorber plate. The ambient air flows through the heat sink located in the lower channel to gain heat. The heated air then flows to the upper channel where it receives additional heating from the absorber plate. Improvements to the thermal and overall efficiencies of the system can be achieved by the use of the double-pass collector system and TE technology. Results show that the thermal efficiency increases as the air flow rate increases. Meanwhile, the electrical power output and the conversion efficiency depend on the temperature difference between the hot and cold side of the TE modules. At a temperature difference of 22.8 °C, the unit achieved a power output of 2.13 W and the conversion efficiency of 6.17%. Therefore, the proposed TE solar collector concept is anticipated to contribute to wider applications of the TE hybrid systems due to the increased overall efficiency.     

Thermal and optical analysis of an evacuated circular cylindrical concentrating collector

An evacuated concentrating circular cylindrical collector has been numerically investigated by ray tracing analyses. The optical efficiency of the collector is found by following incident rays onto the collector cover, calculating the amount of energy absorbed by the receiver for each ray, and then integrating the energy for all rays. Absorption and reflection losses in the collector materials are considered, as well as the formation of ray cascades. A thermal radiation exchange factor between the collector receiver and the cover, needed to find the thermal radiation losses, is also determined using ray tracing techniques. The collector overall efficiency was found for the case of a selective surface coating on the inner receiver cylinder and for the case of an absorbing fluid contained within a semi-transparent inner cylinder. The addition of a highly reflective thermal radiation coating of the inner surface of the cover, in order to suppress thermal radiation losses, was also evaluated.     

Performance comparison of two-pass modified reverse flat-plate collector with conventional flat-plate collectors

The performance of a modified reverse flat-plate collector with air as working fluid is studied. The results are compared with the corresponding results of a reverse flat-plate collector originally proposed as well as with normal flat-plate collectors operating under single and two pass modes. It is found that much higher fluid temperature can be obtained with the new reverse flat-plate collector.     

小型槽式太阳能集热器优化设计与试验研究

按照高性能低成本的原则设计并制作了集热面积为12 m2的商用小型槽式集热器。其主要创新优化之处包括:1通过免背板设计减少了槽式反射镜面结构的重量和用材,提高了镜面曲率精度;2通过推杆联动机构减少了驱动装置;3反射镜面板分离式结构起到了自清洁功能,减轻了清扫的工作强度;4将闭环反馈技术应用到太阳能跟踪控制系统,可实现四季全天候跟踪。现场试验结果表明:在太阳辐射强度为540~660 W/m2时,该集热器可将循环水加热至170℃以上,系统整体集热效率最高可达0.52,但随水温的升高逐渐降低。     

Experimental analysis of a two‐axis tracking system for solar parabolic dish collector

In this paper, an attempt has been made to develop a two‐axis tracking system for solar parabolic dish concentrator and experimentally evaluated the performance of the tracking system. In this proposed design, the sensor design uses the illumination produced by the convex lens on the apex of a pyramid to align the dish in‐line with the sun. The change in incident angle of the solar rays on the lens surface shifts the area of illumination from the apex of the pyramid towards its faces. Photodiodes placed on the faces of the pyramid are used as the sensitive elements to detect the movement of the sun. The sensor output is fed to a microcontroller‐based system to drive the stepper motor on the basis of the programmed algorithm such that it receives normal incidence of sunlight on the sensor. To evaluate the performance of the proposed system, a conventional available 1‐W photovoltaic (PV) panel is placed at the focal point to measure the short circuit current and open circuit voltage. With respect to the conventional solar PV panel, it is observed that the positioning accuracy of the proposed tracking system enhances the short circuit current of 0.11 A by 86%. Thus, the proposed tracking system can be used in a stand‐alone parabolic dish with concentrating PV module as the focal point for further studies.     

Optimization of parabolic trough solar collector system

Process heat produced by solar collectors can contribute significantly in the conservation of conventional energy resources, reducing CO₂ emission, and delaying global warming. One of the major problems associated with solar process heat application is fluctuation in system temperature during unsteady state radiation conditions which may cause significant thermal and operation problems. In this paper a transient simulation model is developed for analysing the performance of industrial water heating systems using parabolic trough solar collectors. The results showed that to prevent dramatic change and instability in process heat during transient radiation periods thermal storage tank size should not be lower than 14.5 l m^?2 of collector area. Small periods of radiation instability lower than 30 min do not have significant effect on system operation. During these periods when water flow rate of collector loop is doubled the time required to restore system normal operating condition increased by a ratio of 1.5. Copyright © 2005 John Wiley & Sons, Ltd.     

The performance of a cylindrical parabolic solar concentrator

An experimental study has been conducted to determine the performance of a cylindrical parabolic concentrating collector with a novel design of the absorber. The experiments have been performed during winter and summer at Basrah, Iraq. It has been found that the concentrator performance depends mainly on water mass flow rate, and there is no significant change when the water mass flow rate becomes more than 10 kg/h.