Tube Solar Collector Research Articles

A review of different working fluids used in the receiver tube of parabolic trough solar collector

A review of different working fluids used in the receiver tube of parabolic trough solar collector

Development and thermodynamic analysis of a novel heat pipe vacuum tube solar collector with sensible heat storage

ABSTRACT A novel heat pipe vacuum tube solar collector has been developed and experimentally investigated for sensible heat storage in different climatic conditions. The solar collector has been introduced with a new header where heat transfer fluid (Therminol-55) gains heat directly in contact with the condenser section of heat pipe. This eliminates the application of thermal paste between condenser and manifold in existing systems. Thermal performance of the system has been evaluated with a heating load of 30 L of Therminol-55 in three consecutive months (March, April, and May) to check its maximum and average performance. Maximum temperature has been found as 145.8°C, 153°C, and 151.2°C in March, April, and May respectively. Maximum energy efficiency has been observed as 44.7%, 24.3%, 23.4%, and maximum exergy efficiency has been observed as 3.1%, 3.3%, and 2.6% in March, April, and May respectively. Average energy efficiency for the whole duration of experiment has been determined as 12.1%, 8.3%, 8.4%, and average exergy efficiency has been determined as 2.1%, 1.9%, 1.8% in March, April, and May respectively. The results suggest utility of the developed solar collector for consistent use in daytime for medium temperature solar heating applications.

Improving a solar collector's efficiency by selecting the composition of the working fluid used

Abstract The study's purpose was to determine the efficiency, as well as the energy and exergy analysis of the vacuum tube solar collector when using a mixture of water with Fe3O4 nanoparticles and multiwall carbon nanotubes in the selected percentage ratio as the working fluid. By varying the concentration of Fe3O4 nanoparticles in the working fluid from 0.05 to 0.15 wt.%, it was found that the maximum efficiency is achieved at a Fe3O4 content equal to 0.1 wt.%. At this concentration, the ratio of Fe3O4 and multiwall carbon nanotubes in the mixture varied from 4:1 to 1:4. It was found that the Fe3O4/multiwall carbon nanotubes ratio (1:4) can increase the efficiency of the solar collector up to 84%. Exergy analysis performed showed that water without the addition of nanoparticles Fe3O4 and multiwall carbon nanotubes was characterized by the maximum values of exergy destruction and entropy generation at any level of solar radiation, and water with the addition of nanoparticles Fe3O4/multiwall carbon nanotubes in a ratio of 1:4 was characterized by the minimum values of exergy destruction and entropy generation.

Experiment of a novel collector design with concentrators and heat storage cores

Combining the compound parabolic concentrator, phase change heat storage cores and vacuum tube solar air collector, a novel solar collector with both heat storage function and concentrating effect was proposed in this paper. Theoretical analysis and experimental investigation were used to illustrate the heat transfer principles and thermal performance of the novel collector. The results indicate that this type of collector not only increased the heat-collecting temperature and efficiency compared to the general solar collector, but also extended the heating time: the maximum output temperature could be improved by 4.5 °C (110.8 °C), maximum transient efficiency could be increased by 12.09 % (73.09 %) and heating time could be extended by approximately 3 h during the day. This study can provide a reference for the future research of multi-technology integrated collectors.

Application of the Thermal Solar Energy in the Primary Circuit of Hot Water of the Four Palms Hotel

A proposal is made in the sanitary hot water system in a hotel installation consisting in the change of the black steel pipe system by high density polypropylene pipes in the primary circuit of the system. A field of vacuum tube solar collectors is sized to work in replacement of the heat recovery system of the water chiller. An economic and environmental analysis of the proposal is made. With the installation of the solar collectors, the hotel will deduct 27,545 liters (15,425 kg) of liquid gas propane (LPG) from its annual consumption, equivalent to 51,728 USD, avoiding the emission of 104,583 kg of CO2eq into the environment. The simple recovery time of the investment will be 5.88 years. The results obtained demonstrate the feasibility of using solar thermal energy in the heating of sanitary water due to the decrease in the consumption of liquefied petroleum gas and, therefore, the environmental damage is reduced when greenhouse gases are no longer emitted.

Effect of various configurations of swirl generator system on the hydrothermal performance of the flat-plate solar collector

This is a numerical study that analysis the heat extraction potential of solar collector tubes by assembling a couple of nozzles at the sealed end of the pipe to make swirl flow. Swirl flow intensifies the turbulence rate which augments heat transfer by ruffling the boundary layer. To this end, several decisive factors including nozzle angle (A: 30°, 45°, 60°, 90°), tube diameter (D: 20 mm, 50 mm), nozzle edge size (N: 6.25, 12.5, 25 mm (for D50) and N: 2.5, 5, 10 mm (for D20)), and mass flow rate (M: 0.1, 0.5, 1 kg/s (for D50) and M: 0.04, 0.2, 0.4 kg/s (for D20)) were considered. Results demonstrated that all of the models of class ''A…/D20/N…/M…“ had higher heat extraction potential but lower friction factor compared with ”A…/D50/N…/M…“. Maximum and minimum values of heat flux extractions are 2113390 W/m2 and 59239 W/m2 that were obtained by ”A60/D20/N2.5/M0.4″ and “A30/D50/N25/M0.1″. The created friction factor by class ”A…/D50/N…/M…“ is higher than class ''A…/D20/N…/M…”. The highest friction factor is 3.51 (''A90/D20/N2.5/M0.04″) and the lowest friction factor is 0.019 (“A30/D20/N2.5/M0.2″). Overall, for all cases, class ”A…/D50/N…/M…“ bear the higher TPF compared with class ”A…/D50/N…/M…“ so that the greatest and lowest values of TPF are 5.09 and 0.49 achieved by ”A30/D50/N6.25/M1″ and “A90/D20/N5/M0.4″, respectively.

Güneş Enerjisi Kaynaklı Farklı Transkritik CO2 Rankine Çevrimlerinin Karşılaştırılması

In this study, different transcritical CO2 Rankine (tCO2-RC) cycles with vacuum tube solar collectors are examined. In this context, the transcritical CO2 Rankine cycle in different configurations, such as simple, regenerator, reheat, regenerator, and reheat, which is widely used in the literature, has been chosen. First, the energy and exergy efficiencies of the cycles were founded by performing thermodynamic analyzes of four various tCO2-RCs under certain operating parameters. Moreover, parametric studies were carried out according to the factors affecting the system performance, like turbine input temperature and input pressure of the turbine. Both analyzes and parametric studies were conducted utilizing the Engineering Equation Solver (EES) computer program. As outcomes of analyzes, the highest thermal efficiency was founded for the tCO2-RC with reheat and regenerator by 11.8%, and the lowest energy efficiency was calculated for the simple tCO2-RC and tCO2-RC with reheat by approximately 6.6%. While all tCO2-RCs' energy and exergy efficiencies increased with the rise of the turbine’s input pressure, the energy and exergy efficiency of all tCO2-RCs decreased with the rise of the pump’s input pressure.

Evaluation of efficiency, thermohydraulic performance evaluation criterion, and field synergy principle improvement of the parabolic solar collector containing the hybrid nanofluid using spring turbulators

In this paper, the study and simulation of turbulent flow inside a parabolic solar collector tube equipped with two spring insert samples with two different pitch ratios (P/D = 0.22, 0.44) and a specific cross-section are investigated. Heat transfer and properties of Cu–Fe3O4/Water hybrid nanofluid with volume fractions of φ = 1%, 3%, and 5% for the range of Reynolds numbers of 7000, 9000, and 11000 are selected and investigated using the single-phase method. The tube is used as the adsorbent pipe of a parabolic solar collector to investigate the performance of the parameters such as volume fraction, Nusselt number, pressure drop, parabolic solar collector efficiency, performance evaluation criterion, and field synergy principle. The results show that with decreasing the pitch ratio, Nu and solar collector efficiency increase. The maximum efficiency is 2.53 for a tube with P/D = 0.22 (Re = 7000, φ = 1%). The maximum efficiency is obtained under the same conditions in a tube containing the spring insert with P/D = 0.44 is equal to 2.39. At the same Reynolds numbers, the average of these velocities is significantly higher than a plain tube. Field Synergy Principle is a reliable criterion to investigate the mechanism of heat transfer increase that this coefficient value in the tube equipped with a spring insert is much higher than in a plain tube. This increase indicates the positive performance of the spring insert on the heat transfer rate and solar collector efficiency improvements. Therefore, spring inserts with a lower P/D are more desirable to achieve the highest efficiency of solar collectors as a source of renewable energy.

Experimental room heating applications relative to increasingly evacuated vacuum tube solar collectors

Experimental room heating applications relative to increasingly evacuated vacuum tube solar collectors

Investigations of performance improvements on the evacuated tube solar collector with and without the incorporation of preheater through various engineering approaches

Solar irradiation is a clean form of energy, and absorption cooling systems powered by solar energy allow for significant energy savings. In the future, the demand for renewable energy may be the most effective way to serve clean energy, especially in Iraq, which has an excellent geographical location. In this research work, the performances of solar collector with and without of preheater have been evaluated. When compared to flat plate collectors at temperatures above 80°C, glass evacuated tube solar collectors provide the combined effects of a highly selective surface coating and vacuum insulation of the absorber element, resulting in a high heat extraction efficiency. Firstly, the Evacuated Vacuum Tube Solar Collector (EVTSC) was tested through experimentation. Secondly, Computational Fluid Dynamics (CFD) approach has been involved in this EVTSC system and thereby the conductive, convective and radiation based heat transfers are computed. Additionally, all possible with inclusive preheater cases are computationally investigated, thereafter the comprehensive report is prepared though validated computational procedures. Finally, the maximum efficiency is observed to be 53% without using a preheater and 61.8% with the usage of the preheater. The increase in efficiency using the preheater is found to be 16.6%.

Heat Transfer Enhancement in a Receiver Tube of Solar Collector Using Various Materials and Nanofluids

The solar flux distribution on the Parabolic Trough Collector (PTC) absorber tube is extremely non-uniform, which causes non-uniform temperature distribution outside the absorber tube. Therefore, it generates high thermal stress which causes creep and fatigue damage. This presents a challenge to the efficiency and reliability of parabolic trough receivers. To override this problem, we have to homogenize the heat flux distribution and enhance the heat transfer in the receiver’s absorber tube to improve the performance of the PTC. In this work, 3D thermal and thermal stress analyses of PTC receiver performance were investigated with a combination of Monte Carlo Ray-Trace (MCRT), Computational Fluid Dynamics (CFD) analysis, and thermal stress analysis using the static structural module of ANSYS. At first, we studied the effect of the receiver tube material (aluminium, copper, and stainless steel) on heat transfer. The temperature gradients and the thermal stresses were compared. Second, we studied the effect of the addition of nanoparticles on the working Heat Transfer Fluid (HTF), employing an Al2O3-H2O based nanofluid at various volume concentrations. To improve the thermal performance of the PTC, a nanoparticle volume concentration ratio of 1%–6% is required. The results show that the temperature gradients and thermal stresses of stainless steel are significantly higher than those of aluminium and copper. From the standpoint of thermal stress, copper is recommended as the tube receiver material. Using Al2O3 in water as an HTF increases the average output temperature by 2%, 6%, and 10% under volume concentrations of 0%, 2%, and 6% respectively. The study concluded that the thermal efficiency increases from 3% to 14% for nanoparticle volume fractions ranging from 2% to 6%.

Active solar collector located on roof ridge assisted Chinese solar greenhouse for thermal environment enhancement

ABSTRACT Maximizing the use of solar energy to increase the indoor temperature of greenhouse is of great significance to the green and energy-saving intensive greenhouse production in China. In this study, an active solar heating system (ASHS) was developed and analyzed, consisting of five solar water heaters equipped with vacuum tube solar collectors, one heat storage tank and heating system including booster pump and heating pipes. During the day, the water was heated in the solar collectors and stored in tanks before being placed into circulation in the heating pipes to distribute the heat to the aerial and root zones of plants. To evaluate the performance of ASHS and the feasibility of practical application, climate and plant growth parameters were monitored in two Chinese Solar Greenhouses (CSGs) located in Yangling, China. Results revealed that under the operating condition with the flow rate of 5.4 L/min, the effective heat collection, average heat collection efficiency and energy-saving efficiency of ASHS were 1.9 MJ/(m2•h), 64% and 84%, respectively. The coefficient of performance (COP) was between 4.5 and 6.2, and the payback period was 12.0 years. Furthermore, the results revealed that the ASHS successfully provided 76% of its annual heating needs, heated the CSG for 4 months and maintained the nocturnal temperature above 8 ℃. The actual application effect proved that it increased average indoor air temperature by 2.2 ℃ and substrate temperature by 3.3 ℃ in heated greenhouse. The growth rate of tomato plant height in the heated greenhouse was 0.7427 cm/d, greater than that in the unheated greenhouse (0.6 cm/d). The novel system proposed in this study adopting particular location enables the rise of the ambient and the substrate temperatures with lower energy consumption, improvement of the environmental conditions in CSG, and a more suitable growing environment for plants in the cold season.

Experimental investigation on the thermal appraisal of heat pipe-evacuated tube collector-based water heating system integrated with PCM

There is a great deal of research being done on the performance of solar collectors. Evacuated tube solar collectors are a mature technology that has proved reassuring performance for heat generation. However, low thermal efficiency remains their main challenge. Therefore, research to improve the efficiency of Evacuated Tube of Solar has continued to date based on some new approaches. The present study presented various designs of Evacuated Tube of Solar collector (ETSC) thermally enhanced by the addition of reflectors and thermal storage units with phase change materials and nanoparticles. The proposed models were assessed during different periods and different zones in Tunisia, especially in the Northern and Southern regions. This work established the energy balance of solar thermal systems determined by the input/output method. Assumptions and mathematical relations are presented for the proposed designs. Additionally, measured and regression useful energy as a function of the daily cumulative global solar energy of all ETSC-types was also evaluated. Research gaps in this field are identified and future research trends and directions are recommended.

TRNSYS Modeling of flat plate and vacuum tube solar collector systems for residential use under equatorial middle altitude climate condition

In this work, residential solar systems were simulated to predict feeding domestic hot water, using TRNSYS (TraNsient SYstem Simulation software), under the operating conditions in Cuenca, Ecuador. The type of research is quantitative and with a correlational approach. Using data from an experimental test, a technical sheet was prepared that sought to identify the main variables to be applied in the model. The diffuse and direct radiation data were obtained by applying the isotropic diffuse model. When simulating in the software, the results show that the system presents an efficiency of 56.54% when heating water in a range of 30° to 45 °C. For the validation of the model, the chisquared statistical test was applied, with which it was determined that the simulated data follow the same distribution as the real data.

Modelling single-effect of Lithium Bromide-Water (LiBr–H2O) driven by an evacuated solar tube collector in Ma'an city (Jordan) case study

The refrigeration systems consume a high amount of energy. In Jordan, conventional energy is an expensive option. Thus, this consumption will be significant. In this work, a mathematical model of the Single-Effect Solar Absorption Cooling system (SESAC), utilizing Lithium Bromide-Water (LiBr–H 2 O) as the working fluid, has been developed with evacuated tube collectors. This model has been designed according to the climate in Ma'an, Jordan. The effect of the temperature changing of the cooling system cycle on the coefficient of performance (COP) and the LiBr–H 2 O crystallization has been investigated using MATLAB/Simulink environment. The best temperatures at which the system operates without crystallization were defined. Moreover, the effect of improving the heat exchanger solution on the overall system performance has been investigated. The medium cooling capacity was (120 kW) and it runs by 243.3 m 2 evacuated tube solar collectors. It was found that the generator's temperature is the critical factor that affects the system's performance as a whole. The highest value of COP was 0.74, at a generator temperature of 110 °C without crystallization.

Air-Type Vacuum-Tube Solar Collector Design and Heat Collection Performance Test

With the continuous development and utilization of clean energy, the thermal utilization of solar energy is an important research direction. In view of the problems of the low utilization rate of solar heat in alpine regions of solar energy, an air-type vacuum-tube solar collector (AVSC) with air as the heat-exchange medium was designed. The vacuum tube of the solar heat collector adopted a double-pass spiral direct-current structure, and the vacuum tube had a built-in heat-storage rod. In order to test the heat collection performance of the designed air evacuated-tube solar collector, a heat collection performance test of the collector was conducted. The results showed that the average heat collection efficiency of the vacuum tube solar collector without phase-change heat-storage rods was 38%. The evacuated-tube solar collector using water as the heat transfer medium had an average heat collection efficiency of 58%. The average equivalent heat collection efficiency of the AVSC with a built-in phase-change heat-storage rod was 61%.

Study the impact of sunlight’s frequencies and solar collector tube magnetic fields in heating generation power of the magnetic nanoparticles: Optimizing by ANN modeling

In addition to radiating high-energy X-rays and long-wavelength radio waves, the Sun emits radiation in all wavelengths along the electromagnetic spectrum. This emission peak happens in the visible part of the spectrum. A Flat-plate Solar-collector is a heat exchanger that change radiant solar energy from sun into heat energy by greenhouse effect. The heat absorbing surface has certain parallel tubes, running length ways crosswise plate that contain heat transfer fluid, routinely water. In this paper, this water replaced to nanofluid containing magnetic nanoparticles and zinc oxide with various volume fractions from 0.1 to 10.0%. Then, a magnetic field was applied around the risers from 100 to 200 Oe. Examination was done for 25 to 45 °C environmental temperature and for 200 kHz frequency. Further, Simulation and Artificial neural network training was done to model the experiment and to find the whole dataset effecting in heating generation power of the magnetic nanoparticles. Final results showed that magnetic field and frequency has an effect in heating generation power of the magnetic nanoparticles.

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.

Using of heat thermal storage of PCM and solar energy for distributed clean building heating: A multi-level scale-up research

Solar energy coupled with electric heat storage is a promising energy saving technology for distributed building heating. Energy saving performance of this technology used in buildings has been widely investigated by prototype-scale experiments and numerical assessments. However, the commercial and economic feasibility of this technology during the operational phase of a real building have not been proven yet. This study conducted a comprehensive techno-economic analysis of the electric heat storage system coupled with solar energy installed in a three-story office building (2000 m2 heating area) in Tianjin, China. The electric heat storage system with the heat storage capacity of 1274.8 MJ was installed on the first floor of the building. The solar collector system with a total heat collection area of 160 m2 was installed on the roof of the building. Meanwhile, the long short-term memory was used to predict the heat gain of solar collector in order to adjust the quantity of storage heat of storage device. The results indicated that the prepared storage medium possessed an excellent thermal property with a total heat storage capacity of 448.8 kJ/kg within 50–150 °C. The average thermal efficiency of vacuum tube solar collector was 51.3%, its heat gain per square meter per day was 6.5 MJ. The use of the solar radiation prediction model stabilized thermal efficiency of heat storage reservoir at 95.8%. The specific operational cost of this system within an entire heating season was 15.6 renminbi (RMB)/m2/season. Distribute clean building heating (DCBH) system can save up to 61% of heating cost compared to the centralized heating. The results showed a great application potential of combination of electric heat storage and solar energy based on solar energy prediction for the heat dispatch of distributed building heating.

Design and Testing of a Separation and Desalination Device for Farmland Saline-Alkaline Water in Arid Areas.

To solve the problem of soil salination and to desalinate saline–alkaline water in arid areas, this study involved the design and testing of a separation and desalination device for farmland saline–alkaline water that is suitable for arid areas. The results of this study indicate that after the pretreatment of farmland saline–alkaline water, the water yielded by the pretreatment device had a mean turbidity of <1 and a mean silt density index (SDI) of <3, which met the working conditions of nanofiltration (NF) and reverse osmosis (RO) membranes. When used to filter saline–alkaline water, the composite NF–RO membrane system achieved a desalination rate of 97.06%, a total hardness removal rate of 97.83%, and a Cl− removal rate of 99.65%, which satisfied the standard for irrigation water quality. Some indicators of the yielded water reached the hygienic standard for drinking water, thus successfully reutilizing water resources. The circulating solar collector tube of the device was designed with a collection area of 6 m2, which could basically satisfy the heat demand of the flash tank for distillation. The design of the flash tank and the shell-and-tube circulating condenser met the requirements for vapor condensation. The crystals in the solar salt box precipitated under solar action. X-ray diffraction was used to identify the primary compound of the crystals as NaCl, suggesting that the precipitates have potential value as industrial salts. This study offers new technical references and helpful engineering guidance for arid saline–alkaline enrichment areas facing the problem of saline farmland irrigation water.