Traditional Solar Collector Research Articles

Experimental Investigation of Thermal Performancefor Novel Integrated Collector Storage

To lower the expenses of manufacturing traditional solar collectors and perfect use of water tanks in developing countries, a new design of integrated water heaters has been presented in a rhombus shape. This new design consists of a cube whose upper surface was cut into two directions at a 45o angle. This system's initial expenses can be kept to a minimum by using inexpensive commercial materials and little manufacturing skills. In cases of thermal instability, the MUE curve is typically employed to calculate the maximum efficiency that the system can attain. The MUE curve, which saves time and computer approaches in calculations of this kind, is the basis for this study. This experiment was studied during November and March to compare the system behavior under different climate conditions. The study included three cases per month. The first case was without any load, which reached a maximum useful efficiency of 59% for both November and March. In the case of continual loading, the system shows a maximum useful efficiency of 59% in March. When dealing with intermittent load, the maximum useful efficiency of 58% in March.

Investigation of Solar Air Collectors with Carbon-Nanotube-Based Turbulators and Pin Fin Arrangements

This research attempts to investigate the thermal performance of solar air collectors with pin fins and turbulators. Incorporating carbon-nanotube-based fins and turbulators in solar collectors can enhance their performance due to their high thermal conductivity, low weight, and high aspect ratio. In the present study, numerical analyses of a solar collector with pin fins and turbulators are carried out to investigate its effect on the Nusselt number. The paper begins with the numerical analysis of conventional air collectors and compares them with theoretical results. This is followed by numerical analyses, which are carried out to examine different configurations of the absorber plate with pin fins of varying diameters (10 mm, 20 mm, and 30 mm) and turbulators of varying heights (20 mm, 40 mm, and 60 mm) in the base plate. The analyses include variations in the Reynolds number ranging from 3000 to 15,000. Subsequently, after the performance of the solar collector with pin fins is evaluated, the effect of turbulators of varying heights on the Nusselt number is analyzed, followed by the analysis of the combined effect of pin fins and turbulators. The results are compared with traditional solar collectors and show that the combined effect of pin fins and turbulators can significantly improve the thermal performance of solar air collectors. The findings of this study can contribute to the development of renewable energy-based air conditioning, ventilation, and heating systems.

The effect of annular phase-change material layer on the thermal behavior of solar collector tube

The temperature of the Heat Transfer Fluid (HTF) in the solar collector tube is greatly affected by the instantaneous solar radiation and which usually causes the HTF temperature large fluctuations. To improve this performance, a novel solar collector tube integrated by annular phase-change material (PCM) layer and solar collector tube was proposed in this study, and the thermal behavior of the tube with 630 mm in length and 20/70 mm in diameter inside and outside has been studied. Solar Salt (60 wt% NaNO3 and 40 wt% KNO3) was applied as the PCM. Air was selected as HTF. The thermal characteristics of the novel and traditional solar collector tubes were experimentally and numerically investigated under different solar radiations and air flow rates. The results show that the temperature in the solar collector tube with PCM were 65.45–128.75 °C higher than that without PCM after cooling for 4 h in different solar radiations. The temperature in the solar collector tube decreased as the air flow rate increased. The average temperature falling rate with PCM were 35.6–76.4 °C/m·s−1 slower than that without PCM during the heat storage process, the solar collector tube with PCM shows more advantages at high flow rates. Within the measuring time of 300 min, the total thermal efficiency of the collector tube with PCM layer is higher than that of without PCM layer. The solar collector tube with PCM is better suited to create a stable mid-temperature and high-temperature environment in continuous solar radiation and heat extraction.

A solar-air hybrid source heat pump for space heating and domestic hot water

Traditional solar collectors (SCs) cannot effectively use solar energy of varying intensity, and air source heat pumps cannot supply heat steadily during defrosting conditions. Accordingly, a solar-air hybrid source heat pump (HSHP) system is proposed to solve these problems. A SC was indirectly connected to a heat pump evaporator and water tank for a user at the same time, to allow direct heating when the solar energy is abundant and to supply heat to the heat pump. Multiple air heat exchangers were also connected indirectly to the heat pump. When one of these is in defrosting mode, the others can still work to guarantee a continuous heat output. The structure and operation strategies are introduced, and a numerical model is established to evaluate the performance of the solar-air HSHP. The performance was also compared with a traditional SC plus an air source heat pump (SC + ASHP). The results show that: (1) the heat provided by the solar-air source heat pump mode is 15%, 11%, and 12% of the total heat production in Chengdu, Beijing, and Shenyang, respectively, which indicates that weak solar radiation can also be used effectively; (2) the energy for defrosting using a solar-air HSHP is only between 30% and 36% of that when using a SC + ASHP system, and between 16% and 35% of that in the ASHP system, which indicates a large energy savings potential of the system in defrosting conditions; and (3) the seasonal performance factor (SPF) during a heating season is 3.61, 3.27, and 2.45 in Chengdu, Beijing, and Shenyang, respectively, and it can reach up to 6.92 in Lhasa due to sufficient solar energy resources.

Experimental research and numerical simulations of a ceramic panel used for solar energy conversion

The paper presents the results of the laboratory testing and numerical simulations of ceramic solar panels. The experimental research was carried out in artificial (laboratory) operating conditions. Rise in temperature and pressure drop of the fluid flowing through the collector was measured. As a result of the tests, the linear relationship between efficiency and reduced temperature difference was determined. While the pressure drop was approximated by the exponential function. Another research method based on numerical modelling using Computational Fluid Dynamics (CFD) algorithms was applied in this study. The three-dimensional geometric model of the ceramic panel was developed using the application included in the Ansys v. 19.2 package. The data obtained from computer simulations were compared with the results of the experiment to validate the numerical model. In order to find potential opportunities to increase the efficiency and due to the fact that the ceramic panel can be made in various inlet and outlet configurations, three simulation cases were considered: diagonal, top – bottom, and left – right. As the results of numerical calculations showed, the largest flow irregularity occurred in the last configuration. Based on the analysis of the test results, it can be concluded that, in spite of some disadvantages, ceramic panels can compete with traditional solar collectors currently available on the market.

Experimental investigation of CuO nanofluid in the thermal characteristics of a flat plate solar collector

Application of nanofluid to increase the thermal efficiency of a traditional solar collector is getting tremendous attention among the scientific community. In this work, the effect of CuO‐water nanofluid, as a working fluid on the efficiency of a flat plate solar collector (FPSC) was investigated experimentally. Volume fraction of nanoparticles was 0.1%, and the particles dimension was 40 nm. The mass flow rates of the nanofluid varied from 1 to 4 L/min. Thermal efficiencies of a FPSC using water and nanofluids as working fluids were matched and compared. The results show that, in comparison with water as the absorption medium using the nanofluids as working fluid increase the efficiency. The results revealed that nanofluids enhanced the energy efficiency up by 15.2%, 17.1%, and 55.1% for the flow rate of 1, 2, and 4 L/min, respectively. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 260–267, 2019

Optical and mechanical tolerances in hybrid concentrated thermal-PV solar trough.

Hybrid thermal-PV solar trough collectors combine concentrated photovoltaics and concentrated solar power technology to harvest and store solar energy. In this work, the optical and mechanical requirements for optimal efficiency are analyzed using non-sequential ray tracing techniques. The results are used to generate opto-mechanical tolerances that can be compared to those of traditional solar collectors. We also explore ideas on how to relieve tracking tolerances for single-axis solar collectors. The objective is to establish a basis for tolerances required for the fabrication and manufacturing of hybrid solar trough collectors.

Numerical and experimental study of building integrated solar tile collectors

This paper is dealing with the development of a new type of shell-structured solar collector for the heat exploitation of solar energy for building use and to determine its thermal efficiency. The literature review confirms that solar collectors appreciated not only by their usefulness, but also according to their aesthetic considerations. In addition to traditional solar collectors it is viable to study the solutions how the structural elements of the buildings can also be used to capture solar energy, when the architectural design would not change, but the required surface operates as solar collector. During the modelling and simulation of the shell-structured solar system strong consideration was given to the efficiency issues. The energy balance equation of the collector includes the influencing factors especially the radiation and heat convection, which are expressed by their heat loss coefficients. Based on the measurements it can be stated that in the case of the simplest structural design (no thermal insulation, no surface covering) the working fluid can warm up to 20–25 °C. Concerning to the structural design the built-in pipe diameter cannot be increased over the half of the concrete tile thickness, and it is not suggested to increase the pipe length beyond 3 m within the tile. A recommended use of such architectural elements can be designed for renovation of buildings, along with the active utilization of solar energy in order to meet the increasingly stringent energy standards for buildings.

Experimental testing of ceramic solar collectors

An alternative to traditional solar collectors with absorbers made of metal or plastic can be panels which have their whole structure made of ceramics. The paper presents the results of the testing of ceramic solar collectors. The experimental research was carried out in summer 2016 in normal operating conditions. Rise in temperature of the fluid flowing through the collector was measured. The maximum value of this parameter did not exceed 7.5°C and the maximum power output extracted from 1m2 of the ceramic solar collector under test was equal to 650W/m2. The thermal characteristic of ceramic solar collectors was determined as the relationship between efficiency and the reduced temperature difference. The straight line corresponding to this characteristic is described by zero-loss collector efficiency coefficient equal to 0.8332 and heat loss coefficient equal to 16.332. Based on the analysis of the test results, it can be concluded that, in spite of some disadvantages, ceramic collectors can compete with traditional solar panels currently available on the market.

Energy and exergy efficiency of a flat plate solar collector using pH treated Al2O3 nanofluid

Application of nanofluid to increase the thermal efficiency of a traditional solar collector is getting tremendous attention among the scientific community. Al2O3–water nanofluid, as a working fluid and its effect on the energy and exergy efficiencies of a flat plate solar collector was examined experimentally. Volume fraction used for this study was 0.1% and 0.3%, while the size of the nanoparticles was ∼13 nm. Experiments were carried out using a stable nanofluid which was obtained by controlling the pH of the solution over a period of 30 days. The mass flow rates of the nanofluid varied from 0.5 to 1.5 kg/min. Energy and exergy efficiencies of a flat plate solar collector using water and nanofluids as working fluids were matched. The results revealed that nanofluids increased the energy efficiency by 83.5% for 0.3% v/v and 1.5 kg/min, whereas the exergy efficiency was enhanced by up to 20.3% for 0.1% v/v and 1 kg/min. Thermal efficiency of the system was found to be more than 50% compared to the existing system available in the literature. New findings on the stability and exergy analysis of the solar collector system operated with a pH controlled nanofluid are reported.

Analysis of Different Techniques for Improving Performance of Flat Plate Solar Collectors for Fruits Drying

Fruits drying had become a broader technology in fruits and vegetables value addition.The technology is reported to be a promising way of drying without incurring higher costbut its adaptation has not been feasible in rural areas. Solar dryers have been developedbut its poor performance limits its applicability. In this study, several techniques formodifications of traditional solar collector were addressed. It was observed that, varyingcollector designs in different techniques, a range of collector performances can bearchived. The research shows that, collector efficiency can be improved by 9.6% whenemploying double duct counter flow compared to conventional collectors. Likewise,performance difference between conventional collectors and studied models were found tobe 8%, 7.2%, 6.1% and 5.2% for model parked with charcoal, 5 mm wire mesh, 4 mmglass thickness and 8 baffles respectively. This study shows that, double duct counter flowsystem is the best option for improving the performance of the collectors, followed bycharcoal and wire mesh. On the hand, using 4 mm glass thickness gave improvedperformance, however, it is recommended for collector size not exceeding 2 m in length.

An improved dynamic test method for solar collectors

A comprehensive improvement of the mathematical model for the so called transfer function method is presented in this study. This improved transfer function method can estimate the traditional solar collector parameters such as zero loss coefficient and heat loss coefficient. Two new collector parameters t and mfCf are obtained. t is a time scale parameter which can indicate the heat transfer ability of the solar collector. mfCf can be used to calculate the fluid volume content in the solar collector or to validate the regression process by comparing it to the physical fluid volume content if known. Experiments were carried out under dynamic test conditions and then test data were processed using multi-linear regression method to get collector parameters with statistic analysis. A comparison of the collector parameters obtained from the improved transfer function (ITF) method and the quasi-dynamic test (QDT) method is carried out. The results show that the improved transfer function method can accurately obtain reasonable collector parameters. The influence of different averaging time intervals is investigated. Based on the investigation it is recommended to use on line calculation if applicable for the second-order differential term with 6–9min as the best averaging time interval. The measured and predicted collector power output of the solar collector are compared during a test of 13days continuously both for the ITF method and the QDT method. The maximum and averaging error is 53.87W/m2 and 5.22W/m2 respectively of the ITF method while 64.13W/m2 and 6.22W/m2 of the QDT method. Scatter and relative error distribution of the measured power output versus the predicted power output is also plotted for the two methods. No matter in either error analysis or scatter distribution, the ITF method is more accurate than the QDT method in predicting the power output of a solar collector.In conclusion, all the results show that the improved transfer function method can accurately and robustly estimate solar collector parameters and predict solar collector thermal performance under dynamic test conditions.

Comparative experiment study on photovoltaic and thermal solar system under natural circulation of water

Abstract The hybrid photovoltaic and thermal (PV/T) system can utilize solar energy more effectively and has a higher total efficiency compared with a traditional solar collecting system and a photovoltaic (PV) module. However, there is limited experimental data on how much energy the PV/T system can save when operating with same area of a PV plate and a solar collector simultaneously. In this paper, a comparative test rig had been set up to measure and analyze the performance of PV/T system. There were monocrystalline silicon PV/T solar collector, a traditional solar collector and a monocrystalline silicon photovoltaic plate. The PV/T collector and the traditional solar collector had the same collecting areas and solar cell covered area of the PV/T collector was the same as the area of the photovoltaic plate. The experimental results showed that the daily thermal efficiency of PV/T system was about 40%, which was about 75% of that for a traditional solar thermosiphon system, and the daily average electrical efficiency was found about 10%, which was a little lower than the photovoltaic module. But primary-energy saving efficiency of the PV/T system was much higher than that of the individual PV plate and the traditional solar collector.

Photocatalytic activity on TiO 2-coated side-glowing optical fiber reactor under solar light

A novel optical fiber reactor (OFR) that employs side-glowing optical fibers (SOFs) as a means of light transmission medium and TiO 2 supporter has been developed, characterized, and investigated. Different from existing ones, the SOF here is made up of quartz core with a silicon cladding, which can emit light from side surface more uniformly and can transmit light for longer distance since attenuation of light through SOF is slow; furthermore, SOF is flexible enough to be entwined into U-shapes. The crystal phase and microstructure of TiO 2 coating are investigated by XRD and SEM. Solar light collected and transmitted to SOF by automatic sun-tracing equipment (ASE) was utilized to excite the titania coating for photocatalytic degradation of 4-chlorophenol (4-CP). Compared to traditional solar collectors, the present one can collect solar light efficiently while occupying smaller area, moreover, ASE allows a long distance light transmission to somewhere such as indoor or sub-surface for photocatalytic applications. Results show that 79% of 4-CP had been decomposed under sunlight irradiation for 8 h.

An experimental study on evacuated tube solar collector using supercritical CO 2

A solar collector using supercritical CO 2 as working fluid is proposed in this paper. In order to investigate and estimate the CO 2-based solar collector, an experimental set-up was constructed. Of particular interest of this paper are the basic collector characteristics, such as CO 2 temperature and pressure in the collector, CO 2 flow rate, and collector performances. The collector has been tested under various weather conditions. The results show that the CO 2 temperature, CO 2 pressure and mass flow rate increase with the solar radiation, which is different from those of traditional solar collector using liquid as working fluid. The solar radiation has influence on the CO 2 states, being liquid, liquid-gas or supercritical state in the test, furthermore, affects the CO 2 mass flow rate. The annually-averaged collector efficiency is found to be above 60.0% in the case of supercritical CO 2 as working fluid, which is much higher than that of water-based solar collector. This study shows the potential of the supercritical CO 2-based solar collector in the field of solar thermal utilization.

Short-term thermal performance of a built-in solar storage for frost prevention in a greenhouse

Built-in solar storage is an alternative to the traditional solar collectors. This paper explores the possibility of utilizing such solar stores for frost prevention in greenhouses. In the study, two identical NE–SW orientated greenhouses with 50 m2 ground area were erected. The total ground area and volume of the water stores used in the solar greenhouse were about 6·4 and 5·4% of the total ground area and volume of the greenhouse. The short-term results showed that at times when the air temperature in the control greenhouse dropped below 0°C, it was about 3·5°C in the solar greenhouse, and sometimes this difference was more than 4·5°C. The average fraction of solar energy storage by the stores was 0·26 for a four day period. © 1998 John Wiley & Sons, Ltd.