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Integrated collector storage solar water heater: Temperature stratification
Abstract
An analysis of the temperature stratification inside an Integrated Collector Storage Solar Water Heater (ICS-SWH) was carried out. The system takes the form of a rectangular-shaped box incorporating the solar collector and storage tank into a single unit and was optimised for simulation in Scottish weather conditions. A 3-month experimental study on the ICS-SWH was undertaken in order to provide empirical data for comparison with the computed results. Using a previously developed macro model; a number of improvements were made. The initial macro model was able to generate corresponding water bulk temperature in the collector with a given hourly incident solar radiation, ambient temperature and inlet water temperature and therefore able to predict ICS-SWH performance. The new model was able to compute the bulk water temperature variation in different SWH collectors for a given aspect ratio and the water temperature along the height of the collector (temperature stratification). Computed longitudinal temperature stratification results obtained were found to be in close agreement with the experimental data.
... In this context, many studies on solar energy consumption have been carried out. These include the following solar water heaters [2]- [4] and concentrated solar power (CSP) plants [5]- [7], which is a promising and reliable solution [8]. Nevertheless, solar energy has a disadvantage: it is unstable, intermittent and non-continuous depending on the different times. ...
... x > 0, 0 < r < R1, t > 0 Mathematical formulation for PCM , , = ² , , ² + , , ) -∆H (2) x > 0, R1 < r < R2, t > 0 0, 0 1, 1, ...
... The effect of the addition of fins on the PCM smelting fraction is illustrated more clearly in Figure 6. The LHS unit melting process can be divided into three stages: (1) a first step is a sensible heat storage step, wherein the PCM temperature is below the melt temperature (250 ° C) and the melt fraction is zero; (2) in the second step, the PCM temperature reaches the melting temperature and the melt fraction goes from 0 to 1; (3) and the third step is the sensible heat storage step, where the PCM is completely fused, and the temperature is greater than the melting temperature. In the first step, the solid-state heat storage step, the temperature difference between the HTF and PCM increases, which causes a very rapid increase in PCM temperature to the melting temperature. ...
The Thermal Energy Storage (TES) occupied an important role in the reasonable use of energy, because it allows the decoupling between the production and the energy demand in the applications with intermittent energy production. In recent years, many researchers have highlighted the use of Latent Heat Thermal Energy Storage (LHTES) systems, this is especially because the high energy density can be stored during phase change. Notwithstanding this great potential, the feasibility of LHTES with PCM is still limited, mainly due to a low thermal conductivity. In this sense, the exchanger with fins is the most effective proposal which is based on the increase of the exchange surface. After a review of recent advances in LHS systems with a focus on methods for improving the thermal conductivity of MCPs, and a selection methodology (Exchanger + PCM) adequate. The main objective of this paper is to develop, perform and compare a numerical study of a new finned exchanger (double pipe with Longitudinal fins on the external pipe, Phase Change Material in the annular space between the two pipes and HTF in the inner pipe) with a classic exchanger without fins. This comparative study was done according to the process of heat transfer during melting (charging) at average temperature (180-280 °C). In addition, the results obtained were adapted for an implementation of Fresnel solar power installed at Green Energy Park (1 MWe) in Morocco. This study has shown that the first exchanger has a good compactness, can store enough latent energy, and significantly overcome the problem of low thermal conductivity related to the second heat exchanger.
... Interestingly, while it is widely believed that Fourier's law is just a linear approximation to a more complex transport law, recent works have shown that, at least for some fluid models, this law holds locally far from equilibrium [7] and well beyond the linear transport regime. Numerous experimental works have studied the statistics of fluctuations of heat flux and temperature in this setting for a wide variety of systems, measuring the corresponding probability distributions [8][9][10], some low-and highorder cumulants [9][10][11][12][13][14][15][16][17][18][19] and the associated temperature profiles [11,12,14,16,19,20]. Nevertheless, developing a general theoretical scheme to understand both typical and rare heat current fluctuations in this setting remains challenging, even for the simplest model fluids. ...
... Interestingly, while it is widely believed that Fourier's law is just a linear approximation to a more complex transport law, recent works have shown that, at least for some fluid models, this law holds locally far from equilibrium [7] and well beyond the linear transport regime. Numerous experimental works have studied the statistics of fluctuations of heat flux and temperature in this setting for a wide variety of systems, measuring the corresponding probability distributions [8][9][10], some low-and highorder cumulants [9][10][11][12][13][14][15][16][17][18][19] and the associated temperature profiles [11,12,14,16,19,20]. Nevertheless, developing a general theoretical scheme to understand both typical and rare heat current fluctuations in this setting remains challenging, even for the simplest model fluids. ...
... With the aim of computing the first few cumulants of the current distribution, we calculate now the scaled cumulant generating function (sCGF) µ(λ) of the current distribution, see Eq. (16) and Section II. Indeed, considering the form of G(J) near the stationary state, Eq. (33), and the Legendre duality between µ(λ) and G(J), Eq. (17), the sCGF can be expanded as ...
Using tools from large deviation theory, we study fluctuations of the heat current in a model of $d$-dimensional incompressible fluid driven out of equilibrium by a temperature gradient. We find that the most probable temperature fields sustaining atypical values of the global current can be naturally classified in an infinite set of curves, allowing us to exhaustively analyze their topological properties and to define universal profiles onto which all optimal fields collapse. We also compute the statistics of empirical heat current, where we find remarkable logarithmic tails for large current fluctuations orthogonal to the thermal gradient. Finally, we determine explicitly a number of cumulants of the current distribution, finding remarkable relations between them.
... Draw off is performed via an internal manifold, which allows all penetrations through the SIP to be localized, reducing the required number of seals through the building's thermal envelope. As stratification within ICS-SWH has been shown to be advantageous [17,18], diffusers have been installed on the inlets to reduce disturbance during draw-off. Additionally provision has been made for the incorporation of an auxiliary heating element, providing the potential for a self-contained hot water system. ...
... The methodology used is similar to that of previous studies of rectangular ICS-SWH systems[2,18,20,21,22,23]to allow comparison of results. ...
... The thermal network solver developed during previous studies [18,20,23] for modelling the field performance of a rectangular ICS-SWH with vertical baffles between the absorber plate and the back of the storage, was extended to allow simulation of both the new ICS-SWH geometry. and account for radiative losses to laboratory surfaces. ...
Solar water heating in Scotland and a novel solar water heater for use in Scottish homes is discussed. The water heater is an evolution of the rectangular integrated collector storage (ICS) design developed at Edinburgh Napier University. Modifications have been made to the geometry, allowing the unit to be embedded within a timber modern methods of construction. The thermal network solver developed during previous studies has been expanded to account for the new design and good correlation is shown with empirical testing.
... According to the calculation, the average fluid velocity V AV shows a complex dependence on flowrate, T IN , and Θ. In the calculation of the nonvertical convection flows typical for ICSSWHs, Rich's method is widely used, where the Grashof number is substituted by Gr sinϕ as in [6] in the evaluation of Archimedean force. Similarly, the modified Richardson number Ri = [gβ(T AV -T IN )Hsinϕ]/V 2 is determined, which indicates stratification stability (here, g is the acceleration of gravity, β is the volumetric expansion factor of water, H is the tank height, ϕ is the angle of inclination of ICSSWH against the horizon, and V is the typical fluid velocity). ...
... The influence of ϕ on stratification degree is especially noticeable in the case of displacement of heated and settled water because, in the process of absorption of solar radiation, the opposite picture is observed: under the increase in ϕ, starting vertical temperature difference (T MAX -T MIN ) decreases because of the more intense convection [4,6]. CONCLUSIONS 1. ...
The numerical modeling of warm water displacement from an inclined tank of an integrated collector storage solar water heater was performed, connection schemes of two heaters and the location of a supply and an extraction pipes were compared. It was shown that the parallel connection of heaters provides the stability of the stratification and a higher heat pickup than the series one, and the diagonal layout of the pipes in a stratified tank is preferable. The picture of thermocline dissipation was studied and the strong influence of the displacing fluid temperature on the degree of stratification was shown.
... C. Garnier and et al (2009) [1], they analyzed of the temperature stratification inside an Integrated Collector Storage Solar Water Heater )ICS-SWH) was carried out. The system takes the form of a rectangular-shaped box incorporating the solar collector and storage tank into a single unit and was optimized for simulation in Scottish weather conditions. ...
... C. Garnier and et al (2009) [1], they analyzed of the temperature stratification inside an Integrated Collector Storage Solar Water Heater )ICS-SWH) was carried out. The system takes the form of a rectangular-shaped box incorporating the solar collector and storage tank into a single unit and was optimized for simulation in Scottish weather conditions. ...
The Integrated Collector Storage Solar Water Heater (ICS-SWH) designed and manufactured in the Alternative and Renewable Energy Research unit, at Technical Engineering College of Najaf. Its consist of a collector box that works as container of receiver cylinder having a length of 1.3m, width 0.83m , short height 0.32 m, and long height 0.81m and receiver cylinder work as the receiver of solar energy to heat the water flows have outer diameter 0.4 m and length 1.1 m. The thermal performance was evaluated extensively throughout the month of March 2015; a maximum temperature difference of 36.3 o C between inlet and outlet of the solar water heater at a mass flow rate of 9 kg/h was achieved. The efficiency of the integrated collector storage solar water heater was calculated. The maximum value during the experimental period was found to be 52%. This reveals a good capability of the system to convert solar energy to heat which can be used for heating water. The objectives of this work are construction solar water heater with minimum law cost and work in Iraq weather.
... Furthermore these authors used honeycomb based transparent insulating material which was rather cost intensive (USD 100/m 2 ) so the concept did not receive mass scale adoption. Garnier et al. [13] studied the temperature stratification of integrated collector storage system in Scottish weather condition. ...
... In Table 1 [13]. Figure 2 shows the temperature variation for a typical sunny day in February. ...
In this paper we describe an integrated collector storage solar water heater for the North Western region of India for use as domestic water heater during the winter season and present the experimental results of temperature stratification. The system consists of a steel water storage tank with azimuthal orientation such that its walls face south east, south west, north east and North West directions. The sunlit walls (south east and south west) and the top cover surface of the storage tank are covered with transparent insulation material (TIM) and the off-sunlit sides with opaque insulation. Experimental results show that the top layer is at the highest temperature. The top layer is drained using a new design of the outlet. The system can be used in rural areas or as a pre heater in more affluent households. The system can return the cost of conversion of the storage tank into a Solar Water Heater in one winter season by saving the cost of electrical energy required for heating water during winter months.
... The results of studying accumulative SWHs suggest that in the heating process, stable stratification forms in the accumulator tank, the vertical temperature dif ference at the maximum density of the heat flow reaches 20-25 K, then slow mixing decreases to approximately 10 K, and the initial steep temperature profile is gradually linearized [7,10,11]. The initial temperature of the liquid in the tank was taken as 323 K, and the temperature of the supplied water was T IN -293 K. Water with temperature T IN entered at a con stant flow rate Q through inlet ∅1 (10 mm in diameter) at the lowest point of the tank and was taken off with temperature T OUT from the top point (opening ∅2 or ∅3, 15 mm in diameter). ...
... The process model to which dimensionless param eter ξ is applicable implies the existence of a ther mocline under a hot unperturbed volume of liquid with a known maximum temperature, which makes it possible to find the value ε ST . In the case of heating of the tank of an accumulative SWH at zero or low load, this is impossible and the smooth temperature profile does not show a pronounced thermocline [6,7,10,11]. For this reason, we have attempted to assess the degree of stratification according to the relation ε/ε SM , which is reliably determined as a result of simulation and does not require a model with ideal plug flow. ...
The process of rapid hot water displacement from the inclined tank of an accumulative solar water heater was simulated, the thermocline dissipation pattern was studied, and the effect on the degree of stratification of the flow rate, the angle of installation of the tank, and the relative position of intake and outtake pipes were determined. Conclusions are presented on the preferential arrangement of hydraulic connections and recommended water pumping, as well as exergetic assessments of the degree of stratification in the accumulator tanks.
... The problem has an analytical solution against which the trained neural networks are tested. This class of problems is used to study buoyancy-induced convection and heat transfer phenomenon and has wide-ranging applications in engineering systems, such as solar collectors, electronic cooling, heat exchangers, and thermal insulating systems etc. [45]. The analytical expressions for the velocity, pressure and relative temperature fields are as follows, ...
Physics Informed Neural Networks (PINNs) are shown to be a promising method for the approximation of partial differential equations (PDEs). PINNs approximate the PDE solution by minimizing physics-based loss functions over a given domain. Despite substantial progress in the application of PINNs to a range of problem classes, investigation of error estimation and convergence properties of PINNs, which is important for establishing the rationale behind their good empirical performance, has been lacking. This paper presents convergence analysis and error estimates of PINNs for a multi-physics problem of thermally coupled incompressible Navier–Stokes equations. Through a model problem of Beltrami flow it is shown that a small training error implies a small generalization error. Posteriori convergence rates of total error with respect to the training residual and collocation points are presented. This is of practical significance in determining appropriate number of training parameters and training residual thresholds to get good PINNs prediction of thermally coupled steady state laminar flows. These convergence rates are then generalized to different spatial geometries as well as to different flow parameters that lie in the laminar regime. A pressure stabilization term in the form of pressure Poisson equation is added to the PDE residuals for PINNs. This physics informed augmentation is shown to improve accuracy of the pressure field by an order of magnitude as compared to the case without augmentation. Results from PINNs are compared to the ones obtained from stabilized finite element method and good properties of PINNs are highlighted.
... The problem has an analytical solution against which neural networks are trained and tested. This class of problems is used to study buoyancy-induced convection and heat transfer phenomenon and has wide-ranging applications in engineering systems, such as solar collectors, electronic cooling, heat exchangers, and thermal insulating systems etc. [40]. The analytical expressions for the velocity, pressure and relative temperature fields are as follows, ...
Physics Informed Neural Networks (PINNs) are shown to be a promising method for the approximation of Partial Differential Equations (PDEs). PINNs approximate the PDE solution by minimizing physics-based loss functions over a given domain. Despite substantial progress in the application of PINNs to a range of problem classes, investigation of error estimation and convergence properties of PINNs, which is important for establishing the rationale behind their good empirical performance, has been lacking. This paper presents convergence analysis and error estimates of PINNs for a multi-physics problem of thermally coupled incompressible Navier-Stokes equations. Through a model problem of Beltrami flow it is shown that a small training error implies a small generalization error. \textit{Posteriori} convergence rates of total error with respect to the training residual and collocation points are presented. This is of practical significance in determining appropriate number of training parameters and training residual thresholds to get good PINNs prediction of thermally coupled steady state laminar flows. These convergence rates are then generalized to different spatial geometries as well as to different flow parameters that lie in the laminar regime. A pressure stabilization term in the form of pressure Poisson equation is added to the PDE residuals for PINNs. This physics informed augmentation is shown to improve accuracy of the pressure field by an order of magnitude as compared to the case without augmentation. Results from PINNs are compared to the ones obtained from stabilized finite element method and good properties of PINNs are highlighted.
... The new climate change law [3] established a goal of a 60% reduction by 2050. Little and nil carbon technologies offer the ability to address major concerns about sustainable development's economic, ecological, and social difficulties [4]. Solar energy has received particular attention among the numerous types of renewable energy since it is readily accessible. ...
The goal of this study is to investigate the heat transfer as well as optimizing the tilt angle of an active flat plate solar collector. In addition, MATLAB software is used for study the flat plate solar performance of the collector. The entire test rig, with a complete control system, has been set up to collect practical data in September and October 2021. The results showed that the collector efficiency rises with the usable heat rate, peaking at 77% in the autumn (14 October) at the optimal heat rate of 975 W and an outlet water temperature of 64℃. However, the system efficiency for the sunny environment is 53% with an outlet temperature of 36℃ in winter (6 Jan). According to this investigation, the monthly average value and yearly value of optimum tilt angle were found to be 30° to 40° and 30°, respectively, for Erbil climate conditions. Also, this study reveals that the average heat loss coefficient between theoretical models and experimental work was 4.352 W/m2.℃. Furthermore, the temperature difference, corresponding to the same amount of heat loss coefficient, was 14.4℃ for the practical model but 15.25℃ for the theoretical part. This study proposes that using the entire experimental data from a Flat Plate Solar Collector instead of using average values and comparing it to the mathematical equations implemented in the MATLAB software, the thermal efficiency of the system was increased by 5%.
... Similarly, the results of Kessentini and Bouden [81] indicate a maximum stored water temperature of 62.0 • C for a 60 L storage tank. In comparison, Dharuman et al. [82] reported the maximum stored water temperature of 60.0 • C for a 100 L storage tank, and Garnier et al. [83] obtained a maximum stored water temperature of 50.0 • C for a 50 L storage tank. On the partly cloudy day, the stored water temperature was 30.0 • C in Esen and Esen [84] and 37.0 • C in Norton et al. [85]. ...
Solar water heating systems can be used in any climate. However, their performance varies depending on the quantity of solar energy available in the region, and more importantly, the temperature of the water entering the system – the colder the incoming water, the higher the operating efficiency of the solar water heater. One of the noble benefits of solar water heating systems is the ability to save money, which is a reason that motivates most people to adopt them. In this study, a thermosyphon solar water heater was built and experimentally tested in an open field in Minna, Niger State-Nigeria, to determine the maximum water temperature and stability of water temperature in a 300-litre storage tank for use in commercial beauty salons. The systems' performance was evaluated on partly cloudy and clear sunny days. The maximum outlet water temperature of the collector was 70.0 °C and 84.0 °C on partly cloudy and clear sunny days, respectively. The maximum temperature values of stored water obtained were 67.0 °C and 78.0 °C on partly cloudy and clear sunny days, respectively. The maximum thermal efficiency values of the solar collector obtained on partly cloudy and clear sunny days were 81.0% and 81.5%, respectively. The respective quantitative values of the collector's operational parameters – the energy absorption (FR(τα)) and the energy loss (FRUL) characteristics – were 0.621 and 2.66 on the partly cloudy day and 0.622 and 2.25 on the clear sunny day. Thus, the thermosyphon solar water heater can meet the hot water needs of beauty salons in Nigeria.
... Borello et al. [30] studied experimentally and numerically the performance of an ICS with a simple design for tents to be installed in case of emergencies such as postearthquake situations in Africa. Garnier et al. [31] investigated numerically the performance of ICS in Scottish weather and validated the data against the results of three months of experimental study. During the study, the water temperature was likely to exceed 70℃, and the study was concluded reliable based on different statistical indicators. ...
This article presents information on thermal management in poultry farming. The different stages of poultry farming require temperatures between 21˚C and 37.7˚C. To fulfill the thermal energy requirements for hatching and brooding researchers have proposed solar energy systems such as trombe wall, solar thermal collectors, etc. To take advantage of latent heat thermal energy storage the incorporation of medium temperature range PCM (5˚C-80˚C) is proposed in this study. This review finds immense scope for PCM incorporation in various systems in poultry farms for sustainable poultry farming which can help in conserving fossil fuels and curbing environmental pollution.
... Selama proses pengujian charging dan discharging, suhu bagian atas/Ttop tangki selalu lebih tinggi dibandingkan suhu bagian bawah/Tbottom. Perbedaan posisi air akibat beda suhu disebabkan oleh buoyancy effect (Garnier et al. 2009). Hal ini menunjukkan bahwa panas yang dihembuskan ke ruang pengering tidak sepenuhnya diambil dari heat exchanger, sehingga air yang sampai ke tangki penyimpanan termal masih memiliki energi panas. ...
The glazed flat plate solar collector has reflective properties so that not all heat energy can be absorbed, but has the ability to trap heat. While the unglazed flat plate solar collector, solar irradiation directly overrides the absorber plate surface (no reflection), but the heat energy absorbed is easily released because this collector has no cover.
This study aims to compare the performance of glazed and unglazed flat plate solar collectors in the same weather conditions for various sun positions, flow rates, and inlet temperatures as well as analyze the performance of glazed and unglazed flat plate solar collector combinations in generating hot air for grain drying applications. This research was conducted in three stages, namely, uniformity testing by looking at the outlet temperature of the two collector types, the ratio of collector efficiency in several conditions which included two levels of water flow rate (1.8 and 3 liters/minute), two inlet temperature levels (40 and 55 °C) and three positions of solar radiation (08.00-09.00, 11.30-12.30 and 15.00-16.00) as well as testing a combination of collector systems with variations in water flow rates through glazed and unglazed flat plate solar collector for air heating.
Performance testing of solar collectors shows that in general glazed flat plate solar collector has better efficiency compared to unglazed flat plate solar collector.The highest efficiency in glazed flat plate solar collector was 64% and unglazed flat plate solar collector was 53% with a flow rate of 3 liters/minute and inlet temperature of 40°C. The inlet temperature of 40°C with a flow rate of 3 liters/minute gives a range of efficiency values of glazed flat plate solar collector of 32-64%, unglazed flat plate solar collector is 26-53% while for inlet temperature of 40°C with a flow rate of 1.8 liters/minute the efficiency range of glazed flat plate solar collector was 33-50% and unglazed flat plate solar collector was 26-38%. Furthermore, for inlet temperature of 55°C with a flow rate of 3 liters/minute, the range of glazed flat plate solar collector efficiency values of 6-37% and unglazed flat plate solar collector was 2-20%, while for flow rate of 1.8 liters per minute the efficiency range of glazed flat plate solar collector of 0-33% and unglazed flat plate solar collector of 0-24%. At noon, in general, the efficiency of solar collectors is greater, where the efficiency of glazed flat plate solar collector is 33-64%, while unglazed flat plate solar collector is 20-53%. In the morning and evening, the highest efficiency of glazed flat plate solar collector was only 40% and unglazed flat plate solar collector was 32%. Cost per Watt (useful energy) depends on the inlet temperature and flow rate used ranging from Rp 5,310/W to Rp 20,268/W. In general, these costs are higher for unglazed flat plate solar collector except for the inlet temperature of 40°C and at the same flow rate of 3 liters/minute, namely glazed flat plate solar collector of Rp 5,310/W and unglazed flat plate solar collector of Rp 5,570/W. The collector combination system has worked well in meeting the needs of drying air for grain dryers. In sunny conditions and during the charging and discharging process, the efficiency of the solar collector remains positive. The best combination of collectors is obtained from the treatment of low initial water temperature (33-35°C) with a flow rate of 4 liters/minute on the unglazed flat plate solar collector inlet and 10 liters/minute on the unglazed flat plate solar collector inlet-glazed flat plate solar collector with an efficiency value of 59.58%. The high initial water temperature treatment (48 -52°C) was able to dry the grain at 745.62kg and at the initial low-temperature treatment it was able (33 -35°C) to dry the grain drying 538.01kg (availability of heat energy for 8 hours).
Keywords: heat energy, flow rate, glazed and unglazed solar collector, solar collector effiency, solar irradiation.
... Borello et al. [124] studied experimentally and numerically the performance of an ICS with a simple design for tents to be installed in case of emergencies such as post-earthquake situations in Africa. Garnier et al. [125] investigated numerically the performance of ICS in Scottish weather and validated the data against the results of three months of experimental study. During the study the water temperature was likely to exceed 70˚C as shown in Fig. 11, and the study was concluded reliable based on different statistical indicators. ...
This review article contains information related to the inactivation of SARS-CoV-2 (Coronavirus) in water and air. It focuses on Heat and UV inactivation of viruses. The author proposed solar energy which is a good source of heat and UV in fight against COVID-19 pandemic. The study also suggests the disinfection of facial masks, PPE kits, health care equipment, public transport, food items, household water, utensils, portable quarantine facilities, hospital wards, etc. using solar energy systems. Thus the evidence-based study of this paper will also provide a new direction to thermal engineers for research in materials, design, and economic feasibility of solar energy systems to combat with COVID-19.
Preprint also available at http://www.enerarxiv.org/page/thesis.html?id=1907
... Charging with various temperature inlet and continuous and batch-wise discharging characteristics were reported. An experiment to simulate the practical conditions in low temperature ambience was done by the study of temperature stratification for a solar water heater by C. Garnier [10] in the Scottish conditions where the radiance fluctuated between 900 W/m 2 to less than 400 W/m 2 .Whereas in India the solar radiation will not be less than 1400 W/m 2 A numerical model was created and validated with the experimental values. Practically the PCM used in application of waste heat was shown by V. Pandiayaraj et al [11] who had done experimental investigation on shell and tube heat exchanger and thermal storage and found that 10% to 15% of heat can be successfully retrieved using this thermal storage application along the exhaust of a diesel storage unit. ...
A latent heat storage system comprising of Phase Change Material (PCM) OM65 encapsulated in spherical capsules and stacked in a cylindrical vessel to form packed bed PCM containment is taken for experiment. The phase change material OM 65 used in thermal storage is useful to store latent heat at 65ºC. At this temperature heat stored is very useful for many of the process industries. This paper not only deals with storing the heat but also deals about the stratification of the PCM containment. The operating parameters like mass flow rate, thermo physical properties of the Heat Transfer Fluid (HTF) and OM 65 PCM have been considered. The inlet temperature of the HTF has been raised according to the heater input to the PCM containment. The temperature profiles of the PCM containment and the HTF were determined using J-type thermocouples and it is recorded by AI8000+ DAQ. These temperature values are used to determine the variation in Stratification number, Richardson number, storage charging efficiency, charging efficiency for the system which has been reported.
... There are many different designs in the literature for ICS. Garnier et al. [3] considered a rectangular-shaped box incorporating the solar collector and storage tank into a single unit and was optimized for simulation in Scottish weather conditions. Kalogirou [4] compared the ICS with flat plate collector and reported that ICS is efficient and inexpensive. ...
Parametric study is carried out in the present article to investigate the unsteady performance of solar energy gain and heat retention of two different integrated-collector storage systems. The systems are the conventional rectangular-shaped storage tank and the modified tank shaped as rectangular cuboid with one semi -circular top. The two systems have the same absorber surface area and volume for water. The heat and fluid
flow is assumed to be unsteady, two-dimensional, laminar and incompressible. The performances of the two systems are evaluated based on the maximum temperature in the system during daytime heating period and nighttime cooling period. For comprehensive study, 24 hours simulations for 3 cases with different wall boundary condition impose on the absorber plate are investigated. The simulation results show that the modified system has better heat retain than the conventional system. Periodic variations of both systems are investigated, and it is found that both systems show consistent results on different days. The modified system is able to store most of the thermal energy in the semi-circular top region with higher temperature than that of the conventional system.
... Garnier et al. [2] have carry out an analysis inside an Integrated Collector Storage Solar Water Heater (ICS-SWH) on the temperature stratification. The system appeared as a rectangular-shaped box consolidating the solar collector and storage tank into a single unit, and was developed for performing a simulation in the Scottish weather conditions. ...
The target of this work is to examine the performance of an integrated solar water heater with corrugated absorber surface. An integrated solar water heater was built and experimentally tested outside so
as to observe the temperature variation of water in the storage tank. The present solar water heater capacity is 140 L. Two cases have been studied, which are with and without flow rate. In case of without
flow rate, the maximum value of stored water temperature obtained is 58 �C and 78 �C during winter and spring seasons, respectively. The stored water temperature got in the present work is higher than for the previous work principally attributable to the corrugated absorber of the storage tank. In case of with load, the daily thermal efficiency values of the solar collector were 59%, 65%, and 67%, when the mass
flow rate values were 0.005 kg/s, 0.0091 kg/s, and 0.013 kg/s, respectively. The outcomes demonstrate that a large thermal losses from the system was observed during the night hours. In addition, the present integrated solar water heater is success to provide hot water suitable to use by the human during the winter and spring seasons of Iraq.
... [6][7][8] Extensive work on this direction has been performed by Tripanagnostopoulos et al 9 and Souliotis et al, 10 as well as several other researchers. [11][12][13][14][15][16] The field's main objective is the development of low cost solar water heaters with effective performance and esthetic incorporation in several types of buildings. 11,[17][18][19][20][21][22][23] A key operational feature of these devices is related to the stratification of water temperature inside the storage tanks. ...
The distribution of solar irradiance on the absorbing surface of a typical integrated collector storage (ICS) system combined with reflector troughs is commonly studied by means of ray tracing techniques. A conceptually different alternative is offered by the method of the average number of reflections (ANR). In the present work, the latter is employed for the systematic optical study of realistic ICS models. In all cases, the solar devices consist of twin cylindrical storage tanks which are mounted on top of stationary asymmetrical CPC‐type reflectors. The emphasis of the current research is mainly placed on the evaluation of the ANR reliability for the calculation of the optical efficiency of the related twin‐tanked devices. Additionally, useful operational parameters, such as the optical performance of the proposed geometries, are also determined. The behavior of the tested ICS systems reveals that the optical efficiency may vary in the range of 0.75 to 0.91, exhibiting a strong dependence on the geometric parameters of the solar devices. The highest efficiency is achieved by the systems which combine large reflecting area and storage tanks in close proximity.
Highlights
• Geometric analysis of double‐tanked ICS solar water heaters.
• Calculation of the average number of reflections.
• Optical efficiency of the examined ICS solar water heaters.
• Nonuniform illumination of the storage tank of each ICS solar water heater.
... It was pointed out that the proposed design demonstrated better preservation of hot water temperature during the night. Garnier et al. (2009) studied and optimized a rectangular-shaped box assembling the solar collector and storage tank into a single unit, longitudinal stratification of temperature within the collector was modeled and the system efficiency was discussed. Kumar and Rosen (2010) have introduced a corrugated absorber surface over plane surface in the ICSSWH. ...
This work presents a detailed analysis of an improved Integrated Collector Storage Solar Water Heater (ICSSWH). This type of device is well suited for rural areas of Morocco because of its low cost, simplicity and compact structure. The innovation targeted in this system lies in the integration of a latent storage system by using a layer of phase change materials (PCM) in its lower part. Indeed, this integration is likely to increase the thermal energy delivered to the user during the night. The overall performance of the system depends on external climate data, type of PCM used and its mass, and flow rate of water. N-eicosane is considered as PCM in this application while hourly weather data corresponding to the city ER-RACHIDIA is used for the analysis. A detailed 2-D transient simulation has been established to optimize the system performance by studying the effect of different design variables and operating conditions. A deep analysis was also made to understand the PCM melting and solidification processes for a better exploitation of this storage technique. Optimized results are obtained when a mass flow rate of 0.0015 kg/s is used with a PCM thickness of 0.01 m and a set temperature of 313 K.
... It was pointed out that the proposed design demonstrated better preservation of hot water temperature during the night. Garnier et al. (2009) studied and optimized a rectangular-shaped box assembling the solar collector and storage tank into a single unit, longitudinal stratification of temperature within the collector was modeled and the system efficiency was discussed. Kumar and Rosen (2010) have introduced a corrugated absorber surface over plane surface in the ICSSWH. ...
... It is one of the main factors of the performance of the hot water storages. It is the degree of the difference in temperatures between the top and the bottom parts of water inside the collector [18]. Stratification is found to be efficient not only for the water storage tank but also for the whole system linked to it. ...
The increasing demand to enhance sustainability and reduce carbon emission and pollution is attracting the attention for implementing and integrating diverse heating technologies such as heat pumps, solar energy, gas boilers, Combined Heat and Power (CHP), and electric heaters. Integrated technologies for heating include low and high temperature district heating, domestic small-scale applications and commercial large-scale buildings. Energy from flooded coalmines and water from other sources could also play a vital role in improving energy efficiency of heating and cooling applications. Stratified thermal storage are likely to significantly contribute to energy efficient heating, particularly when implementing a mixed-approach of diverse technologies. A stratified hot water tank, and naturally stratified reservoirs, are expected to play a central role in the integration of several heating technologies that operate efficiently at different levels of temperature with reduced cost. This paper presents a new innovative technology to improve stratification, namely ‘the water snake’ and an automated test rig to evaluate the new stratification method for energy utilisation using energy storage of hot water. An automated system is utilised to evaluate the performance. The results indicate that the test rig has been successful for the automated testing of the technology. Moreover, the results show that the water snake, as a new technology for stratification, is successful in minimising mixing and turbulence inside the thermal energy storage. The results prove that the technology could be implemented for a wide range of applications to enhance the efficiency of heating systems in buildings as well as district heating and cooling applications.
... Developing an efficient storage tank design is yet another strategy to enhance the performance of the ICSSWHs. Many storage tank configurations are being researched such as cylindrical [41][42][43][44], rectangular [24,32,[45][46][47][48][49][50][51][52], triangular [30,[53][54][55], and trapezoidal [36,56] while others include two parts one exposed and one insulated [32,33,57]. While some systems help increase the heat transfer from absorber plate to the water [53,54], others improve thermal stratification in the water storage tank [56] or both [33,58,59] or have better heat retention capability [59][60][61]. ...
Integrated collector storage is a long established simple low cost solar water heater configuration combining the solar collector with a storage tank into a single unit. Previous studies have shown the potential of integrated collector storage solar water heaters to significantly reduce domestic energy requirements for water heating, however challenges still remain to integrate them in roof/façades and ensure appropriate domestic hot water demand. In this article, a novel integrated collector storage solar water heaters is being investigated. The configuration and geometry proposed incorporates an embedded heating element to provide a self-contained domestic hot water system and consider roof integration restriction allowing the unit to be embedded within a structural insulated roofing panel system. The proposed system also utilizes an inlet diffuser designed to reduce the disruption to the stratification within the storage during and following draw-off. This article presents a Computational Fluid Dynamic analysis of internal flows and heat transfer regimes within this new collector configuration and compares its performance against previous developed prototypes using empirical testing. The increased aspect ratio of the new design was shown to significantly alter the heating and cooling characteristics of the collector, both gaining and loosing heat at a greater rate than the original prototype. The computational analysis showed that the collector charges effectively with some stratification. Higher draw-off rates however resulted in higher bulk water outlet temperatures, providing better energy delivery efficiency. The inlet diffuser was also shown to improve the thermal efficiency of the unit overall. The empirical testing shows the improvement in performance of this novel integrated collector storage solar water heaters against previous developed prototypes. The study highlights the need to review the effect of draw-off regime upon the performance of such systems in order to identify optimal regime and control strategy.
... LHSS were the subject of numerous research works during the last 20 years. This is due to the fact that they are used in several practical applications including solar building systems [1], [2], solar water heating systems [3], [4] and solar energy generation systems [5]- [9]. ...
... LHSU were the subject of numerous research works during the last 20 years. This interest is due to the fact that they are used in several practical applications including solar building systems [1,2], solar water heating systems [3,4] and solar energy generation systems [5][6][7][8][9]. ...
... However, tank geometry can effect temperature distribution. Previous researches (Joudi et al., 2004;Jordan and Furbo, 2005;Garnier et al., 2009;Oshchepkov and Frid 2015) focused on stratification in a solar water heating systems. A solar collector designed for disinfection, especially with a non-continuous form, should provide a uniform temperature distribution. ...
Reusing water drainage can effectively reduce water consumption in greenhouses. However, disinfection is unavoidable. A proper solar disinfection system needs uniform temperature distribution. Four different adiabatic tanks (prism, changed prism, cube and half-cylinder) were compared to achieve temperature distribution using a 3D computational fluid dynamics simulation. The tanks were equipped with solar heat pipes and their heat flux were assumed constant. A 30 minutes transient simulation was performed. The results showed that the cube tank had the most temperature uniformity, then the prism but with lower mean temperature. The changed prism and half-cylinder had almost similar effects and lower uniformity.
... The melting and solidification processes are encountered in a wide range of applications, such as electronic cooling [6][7][8][9], solar water heating systems [10][11][12][13][14][15], and building envelopes [16][17][18][19][20]. Consequently, a number of numerical, analytical, and experimental studies on latent heat storage units (LHSUs) have been performed over the last 20 years. Lazaro et al. [21] presented an experimental setup for evaluating the thermal performance of a phase change thermal storage system used for free-cooling. ...
... The new climate change bill [4] set a target reduction of at least 60 % by 2050. Low and Zero Carbon Technologies (LZCT) have the potential to meet the important concern with respect to economical, ecological and social issues of sustainable development [5]. ...
... Meanwhile, another example of the passive systems is the integrated collector storage (ICS). It is a combination of the solar collector and thermal storage tank [71] which incorporates both components in a single unit [72]. Apart from being one of the simplest forms of solar water heater in the market and becoming a very popular choice when choosing solar water heaters [73], it also reduced the cost [74], as they integrate the collector and the heat storage in the same construction [75]. ...
Solar energy is one of the widely used renewable energy that can be harnessed either by directly deriving energy from sunlight or indirectly. Solar water heating system, on the other hand, is one of the applications of solar energy that has drawn great attention among researchers in this field. Solar collectors, storage tanks and heat transfer fluids are the three core components in solar water heater applications, which are reviewed in this paper. This paper discusses the latest developments and advancement of a solar water heater based on the three basic components that may affect the thermal performance of the system. It also reviews the development of various types of solar collectors in solar water heater, including both the non-concentrating collectors (flat plate collector, evacuated tube collector) and the concentrating collectors (parabolic dish reflector, parabolic trough collector). All these are studied in terms of optical optimization, heat loss reduction, heat recuperation enhancement and different sun tracking mechanisms. Among the non-concentrating and concentrating collectors, the parabolic dish reflector collectors show the best overall performance. The use of nanofluids as a heat transfer fluid was also discovered in this paper.
... The development of numerical methods, particu larly, the control volume method [13] and the inven tion of specialized CFD (ComputerFluidDynamics) software have encouraged interest in the numerical modeling of heat mass transfer during fluid motion in chambers of different forms, including storage tanks of solar water heating units. In recent years several papers on modeling convective processes in stratified tanks [4,[14][15][16][17][18][19][20][21][22], including accumulative SWHU tanks, have been published. ...
The 2D numerical model of an accumulative solar water heating unit is developed. The model was verified by comparing the modeling results with the 3D calculations and experimental data. The resulting pattern of flow made it possible to prove the validity of using the zone model to simulate the fluid flow in a solar water heating unit (SWHU) and suggest a simplified model of the unit, the calculation results for which agree with the numerical modeling results.
... The daytime collection efficiency and overall efficiency of the system were estimated 60% and 40% respectively. The temperature stratification, stratification time and the water temperature in a rectangular shaped box type ICSSWH system were studied investigated by Garnier et al. [68] using a macromodel previously developed by Currie et al. [69]. ...
... However, the practical long-term performance of these devices under scaling conditions, or in terms of pathogen control, has never been rigorously assessed. Concerns have been expressed about pathogen re-growth in solar applications although limited data available to date is inconclusive [44,45]. In general, it might be expected that electric heat pump and solar systems would behave like electric tank systems relative to possible growth of premise plumbing pathogens, but with much higher storage volumes. ...
Residential water heating is linked to the primary source of waterborne disease outbreaks in the United States, and accounts for greater energy demand than the combined water/wastewater utility sector. Furthermore, home water heating is the second largest energy consumer in the home and thus represents an integral part of the water-energy nexus. To date, there has been little practical research that can guide decision-making by consumers, public health officials and regulators with regards to water heater selection and operation to minimize energy costs and the likelihood of waterborne disease. Scientific uncertainties associated with existing " green " advice have potentially created misguided policy with long-term negative repercussions. This review is aimed at defining the current state of knowledge related to hot water infrastructure and in highlighting current gaps in the research. While there are many sustainability claims of certain water heater types (i.e., hot water recirculation systems and instantaneous water heaters) these claims have not been substantiated in head-to-head testing of the interplay between water temperature, energy, microbial growth, and scaling, all measures that need to be better defined.
... Another version of a solar water heater, the integrated solar water heater or built-in-storage (BIS), has been proposed and tested by several researchers [4][5][6][7][8][9][10]. The simple design of this type solar water heater has a good potential for many developing countries and also for countries with cold climates (for seasonal applications). ...
... The process of thermal stratification in a square collector of 1 m 2 of area and 50 L of volume is consid ered in [2][3][4][5]. The idealization of the model was that the heat flux during the time of warming up the tank is considered constant (although its value varied from 50 to 600 W/m 2 ), the process does not exceed a few hours, and the problem was solved in a two dimen sional approximation. ...
To determine the influence of the shape of the tank, the installation angle, and the magnitude of the absorbed heat flux on thermal stratification in integrated collector-storage solar water heaters, numerical simulation of thermal convection in tanks of different shapes and same volume was carried out. Idealized two-dimensional models were studied; automodel stratification profiles were obtained at the constant heat flux. The shape of the tank, the pattern of the heat flux dynamics, the adiabatic mixing on the circulation rate and the degree of stratification were shown to have significant influence.
One of the most extensively used forms of energy is solar energy. It is a widely utilized, low-cost, eco-friendly, sustainable, emission-free renewable energy source, and it reduces power costs from coal, electricity, and other sources. Solar energy is utilized for several reasons, such as water heating in homes and industrial applications using solar collectors. Unlike other solar collector energy applications, flat plate solar collector techniques for water heating offer low maintenance and operational expenses. This article reviewed the innovations of flat plate solar collectors for improved thermal performance with reflectors in solar water heaters. The impact of combining flat plate solar collectors and reflectors for thermal performance improvements is discussed in this article. Integrating flat plate solar collectors using reflectors is an effective and cost-effective approach among the numerous geometries utilized for thermal performance improvements. In order to improve SWH performance, researchers have implemented a number of modifications so far. These modifications are associated with various types of reflector integration in SWH such as booster mirror reflector, plane reflector, side reflector, bottom reflector, top-edge reflector, inclination angle of reflector, gap between reflector and collector, trapezoidal reflector, parabolic reflector, polyline reflector etc. The major goal of this paper is to evaluate several studies wherein different reflectors have already been utilized to improve thermal performance and to recommend a design for the best performance. Furthermore, the research gap has been identified, along with suggested upgrades for future study, which should benefit researchers in extending the growth of this technology.
The notion of enhanced thermal convection via particle laden fluids has been around for a long time. Technological challenges associated with the development of micro to nano particles with desired properties and their uniform dispersion in the base fluid have been a bottleneck. Relatively recently, the advent of modern manufacturing techniques from micro to nanoscales have rekindled extreme interest in this class of fluids for innovative applications in advanced engineering systems.
Buoyancy-induced convection and heat transfer involves conservation laws of mass, momentum, and energy. The mathematical model is comprised of two-way coupled system of mixed-field and convection-dominated partial differential equations. A stabilized method for nonlinearly coupled system is presented, and a systematic approach to develop the sub-grid scale (SGS) physics-based models is described. Explicit structure of the stabilization tensor is derived and it is shown to preserve nonlinear coupling in the SGS models that plays a critical role when nonlinear coupling of mechanical and thermal fields leads to anisotropy across the scales. The formulation is variationally consistent and results in optimal spatial convergence rates on structured meshes for linear triangles and bilinear quadrilaterals. Consistent linearization of the nonlinear system of equations yields quadratic rate of convergence of nonlinear iterations in the Newton-Raphson method. The method is tested on problems with increasing level of complexity to highlight the mathematical attributes of the method and its range of applicability.
Due to the lower cost and compact structure, Photovoltaic Integrated Collector Storage Water heater combined (PV– ICSSWH) is an alternative form of PV/T system that differs from traditional flat-plate or vacuum tube PV/T system. An analysis was carried out to investigate the effect of operating parameters and structural factors on system performance. A numerical model was developed to predict the performance of the systems. To validate the numerical model, a prototype system was built and tested. The influence of solar radiation, ambient temperature, the thickness of systems, and the aspect ratio of systems was analyzed and the results indicate that: (a) The aspect ratio has a negligible effect on the efficiency. However, it has a significant influence on temperature stratification. (b) As the thickness of the system drops from 100 mm to 60 mm, its total efficiency descents from 55.1% to 52.7% and the relationship is given. (c) The total efficiency only decreases from 54.7% to 53.5%, when the solar radiation rises from 400W/m2 to 800W/m2. (d) As the ambient temperature increases from 283K to 303K, the total efficiency of the system ascends from 45.6% to 61.4%. (e) The total efficiency is about 48.0% in Lanzhou, China which is predicted.
Conversion of solar energy to heat energy is a cost effective, sustainable and an efficient technology to heat water. Solar integrated collector-storage type of water heaters (ICSSWH) is a water heating device which alchemizes solar radiation directly into heat so that it is used for water heating. These systems are compact, simple in design and free from copper tubes bounded structures which unnecessarily causes heat losses and leakage issues. Their collection efficiency is usually higher than commonly used flat plate collectors (FPC). Despite of many advantages, the main disadvantage of compact integrated collection-storage type of water heaters (ICSSWH) is high heat losses during night hours which decreases the water affects the thus decreases the overall efficiency of the system. However, there are some strategies to minimize this heat loss from the system at the time when sunshine is not available; some of the methods are discussed in this paper. Moreover, in this article, the authors discuss the latest development in the new and improved compact water heater designs. In present paper authors critically reviewed various designs of ICSSWH. Use of insulated cover during night, introducing baffle plate structure, using PCM materials and using reverse thermosyphon valve are some of the strategies to minimize the heat losses from the system these methods are discussed in the present paper. Connecting tanks in series is also an effective method to overcome this problem of heat loss during night. In this paper the effect of connecting tanks in series on water temperature has been discussed. This paper presents an overall summary on compact ICSSWH systems which can be useful for further research to design and develop a new small size solar water heater.
This paper presents a locally and dynamically adaptive residual-based closure model for density stratified incompressible flows. The method is based on the three-level form of the Variational Multiscale (VMS) modeling paradigm applied to the system of incompressible Navier–Stokes equations and an energy conservation equation for the relative temperature field. The velocity, pressure, and relative temperature fields are additively decomposed into overlapping scales which leads to a set of coupled mixed-field sub-problems for the coarse- and the fine-scales. In the hierarchical application of the VMS method, the fine-scale velocity and relative temperature fields are further decomposed, leading to a nested system of two-way coupled fine-scale level-I and level-II variational subproblems. A direct application of bubble functions approach to the fine-scale variational equations helps derive fine-scale models that are nonlinear and time dependent. Embedding the derived model from the level-II variational equation in the level-I variational equation helps stabilize the convection-dominated mixed-field thermodynamic subproblem. Locally resolving the unconstrained level-I variational equation yields the residual-based turbulence model which is a function of the residual of the Euler–Lagrange equations of the conservation of momentum, mass, and energy. The derived model accommodates forward- and back-scatter of energy and entropy and embeds sub-grid scale physics in the computable scales of the problem. The steps of the derivation show that it is essential to apply the concept of scale separation systematically to the coupled system of equations and it is critical to preserve the coupling between flow and thermal phases in the fine-scale variational equations. The method has been implemented with hexahedral and tetrahedral elements with equal order interpolations for the velocity, pressure, and temperature fields. Several canonical flow cases are presented that include Rayleigh–Bénard instability, Rayleigh–Taylor instability, and turbulent plane Couette flow with stable stratification.
The photovoltaic/thermal system with direct-coupled photovoltaic pump is different from the one with traditional DC pump or with natural circulation. Because for the photovoltaic/thermal system with photovoltaic pump, when the solar irradiation increased the water flow rate of the photovoltaic pump would increase, which would enhance the heat convection between the water and photovoltaic/thermal collectors, and made the water obtain more thermal energy, and when the solar irradiation decreased the water flow rate would also decrease, which would reduce the thermal loss for the one with traditional DC pump. In order to compare the three systems, in this paper three photovoltaic/thermal systems with different circulation methods were set up and tested. And comparison among them was made to analyze their performances. The results showed that the photovoltaic/thermal system with photovoltaic pump had the best thermal performance among the three systems. The net energy obtained by the system with photovoltaic pump was close to or a little more than the system with natural circulation, but which was significantly higher than that of the system with traditional DC pump. For the three systems, the system with natural circulation obtained the highest energy efficiency of 69.63% and the highest exergy efficiency of 12.84%.
The demand for effective and efficient use of solar heating arrangement is increasing in domestic and industrial applications. The existing renewable energy resources are intermittent and fluctuate depending upon the meteorological conditions. So, the main aim of this present work is to develop thermosyphon solar heating system for improving the performance using modified phase change material (PCM) modules. Paraffin wax material is used as PCM for holding the heat energy to attain an effective solar fraction. A detailed stratification experimental analysis for heat energy accumulation tank has been carried out on without PCM, PCM without fins, PCM with ring type fins and spiral fins. An hourly based charging and discharging efficiency are also calculated for the above cases and compared. All the experiments are carried out three times and average values are taken for the analysis. From the results measured experimentally, it is inferred that the discharging time of solar water heating system with cylindrical PCM ring type fins is 3 h more than without PCM. The discharging time of solar water heating system with cylindrical PCM took 7 h more than without PCM. The charging energy efficiency of heat energy accumulation tank with cylindrical PCM ring type and PCM in spiral module fins confers better results than cylindrical PCM and without PCM. This shows that the PCM get better stratification time and increases the overall performance of solar water heating system.
Integrated solar water heating is the conversion of sunlight into heat for water heating using a solar thermal collector.
Using tools from large deviation theory, we study fluctuations of the heat current in a model of d-dimensional incompressible fluid driven out of equilibrium by a temperature gradient. We find that the most probable temperature fields sustaining atypical values of the global current can be naturally classified in an infinite set of curves, allowing us to exhaustively analyze their topological properties and to define universal profiles onto which all optimal fields collapse. We also compute the statistics of empirical heat current, where we find remarkable logarithmic tails for large current fluctuations orthogonal to the thermal gradient. Finally, we determine explicitly a number of cumulants of the current distribution, finding interesting relations between them.
This research is about performance investigation of a multiple-tank integrated-solar collector storage heater. A prototype of the heater having a capacity of 300 Liter was constructed and experimentally tested outdoors to observe the variation of water temperature in the storage tanks. A Fluent program is used to predict the storage water temperature. The experimental data was verified with the results from the simulation model. In vice versa, the simulation model was validated using the experimental data. Two cases have been studied, namely with and without flow rate. The results show that the maximum water temperature exited from the storage tanks during February month of 2010 was 48°C. The results illustrated that the present integrated solar water heater was a success in providing hot water suitable for day time use by households during the winter in Iraq.
The work focuses on the experimental study of the heat diode mechanism in an Integrated Collector Storage Solar Water Heater (ICSSWH) for domestic applications. The solar device combines a horizontal cylindrical vessel with an asymmetric reflector trough (Compound Parabolic Concentrator – CPC). The cylindrical storage tank comprises two concentric cylindrical vessels: the outer absorbing vessel and the inner storage vessel. The annulus between the cylindrical vessels is partially depressurized and contains a small amount of water serving as Phase Change Material (PCM), which changes phase (mainly at low temperatures) thus producing vapor and creating a thermal diode transfer mechanism from the outer to the inner surfaces of the vessels. Several experimental results, including uncertainty analysis, are demonstrated through diagrams depicting temperature variations, mean daily efficiency and thermal losses coefficient. Additionally results from the variation of the temperature and the total pressure inside annulus are also presented. The results clearly show that the vapor's pressure plays the most important role regarding the thermal performance of the device.
This study investigated the performance of an integrated collector storage solar air heater based on latent heat storage and flat micro-heat pipe arrays. The structure and working principle of the device were explained in detail. The effective area of the collector is 0.93 m², and the mass of the phase change material (PCM) is 45.8 kg. An integrated collector storage experimental system was set up, and outdoor experiments were conducted to demonstrate the feasibility of the device for energy storage and air heating. The temperature distribution of the PCM was recorded during charging and discharging to monitor the propagation of the melting and freezing front. Efficiency and power during charging and discharging were also calculated. The integrative device exhibited 59% and 91.6% efficiencies for solar air charging and discharging at 393 and 344 W power, respectively.
This paper presents the comparative study of two commercially available types of solar water heaters for domestic applications: Flat Plate Thermosyphonic Units (FPTU) and Integrated Collector Storage (ICS) solar water heaters. The conducted analysis initially focuses on the experimental investigation of the thermal behaviour and proceeds to the detailed holistic environmental analysis for both systems through a completed Life Cycle Assessment (LCA) study (i.e. throughout their fabrication, installation and operation phases).
This paper presents the results of a simulation study of a solar domestic water heating system using the Exodus method. The simulations have been performed with three days of real weather data. Investigations of thermal conditions in the flat-plate solar collector-water-storage tank system enabled to carry out a detailed evaluation of energy efficiency of the solar installation. The influence of the flow rate of the medium in the collector cycle, of initial water temperature in the tank and of the solar irradiation for a day on the quantity of energy accumulated in this system was analyzed. The efficiency of energy accumulation in the tank at the stage of its loading and during hot-water consumption was determined.
The solar water heater is one of the fastest growing technologies in the renewable energy sector. Numerous designs of solar water heaters have been developed in the past that aim to make the system simple, reliable and cost-effective. The integrated collector storage (ICS) solar water heater is one of the simplest applications of solar energy for water heating. In an ICS solar water heater the collection of solar energy and the storage of hot water occur in a single unit. The ICS solar water heater is an isolated system that involves no moving parts and allows the user to be independent of grid electricity. The ICS solar water heater has been demonstrated to operate consistently and reliably for many years with a small initial investment relative to other solar water heater designs. However, the ICS solar water heater is not very efficient for overnight applications and its thermal output diminishes sharply as the time increases between solar irradiance and use. This performance decline can be attributed to the increased heat losses during off-sunshine hours. To make the ICS solar water heater a more economically viable
option, the system has evolved, utilizing new research advances to maximise solar radiation collection and minimise thermal losses as much as can be reasonably accomplished.
A simple low cost Integrated Collector Storage Solar Water Heater (ICS-SWH) was proposed for simulation in Scottish weather conditions. The system takes the form of a rectangular-shaped design incorporating the solar collector and storage tank into a single unit and the simplicity of construction and installation make this type of SWH a popular choice of solar water heater. A 3-month experimental and numerical study on the ICS-SWH was undertaken in order to compare the results with a newly developed macro model. Improvements were incorporated into the macro model by differentiating non-finned and finned collectors. The macro model was able to compare the water bulk temperature variation in different SWH collector material, with or without fins, internal temperature and external weather conditions for a given aspect ratio. Numerical results obtained by this new tool were found to be in close agreement with the experimental data.
Practical applications: Direct comparison of measured system performances is relatively straight forward; however, predicting the performance of an ICS-SWH at another location or with a different installation configuration is more challenging. A model able to predict water temperature in ICS-SWH would be a useful tool to allow any user to predict the performance of the installed SWH, depending on the orientation and location. Builders could use such a tool to demonstrate the performance of the ICS-SWH and the benefit of such installation.
Stratification inside the water storage tank of a solar heater is a desirable natural phenomenon that improves the collector output. For an ICS storage heater type, where the storage tank is in direct contact with the heating surface (absorber plate), stratification becomes more important as it plays an additional role of defining the heat gain characteristics. In the present research, stratification has been studied for a simple flat plate integrated collector storage (ICS) type heater at various inclinations and applied heat flux values. Experimental results have been compared to CFD results and good agreement is found between the two. The influence of stratification on the heat gain characteristics has also been examined. As the collector can be mounted at different angles to maximize solar gain at different latitudes, the angle of inclination of the solar water heater can vary in range 0°-90°. This variation in angle influences the stratification pattern. The study of stratification is important for determining the weighted average temperature, which is the sole parameter to evaluate the total heat gained by the water inside heater. It was found that stratification changes with the change in the angle, applied heat flux and time. These changes were experimentally recorded and analyzed to evaluate the thermal response of the system to the stratification. CFD studies were also carried out for deeper insight as the experimental setup did not provide finer details. The results can be used for designing outlets for ICS heaters at various locations.
The thermal performance of three different small solar heating systems for domestic hot water supply has been measured under the same conditions. A reference system with a normal volume flow rate, a pumped system using a low volume flow rate, and a thermosyphon system have been tested.
Extensive theoretical and experimental studies on a built-in-storage solar water heater which was developed earlier by Garg in India, are carried out. In this water heater the absorber plate performs the dual function of absorbing the solar energy and storing the heated water. In the theoretical study, the transient performance of the system is predicted by solving the mathematical models consisting of energy balance equations which are written on different collector nodes by considering their capacity effects and various heat loss effects. These equations are converted in the finite difference form and then solved by digital computer. Solar radiation and ambient temperature are represented by Fourier series in the theoretical analysis. Its night cooling drawback is somehow checked by covering the collector system by an insulation cover during cooling hours and also by using a insulated baffle plate inside the tank adjacent to the absorber plate. It is observed that by using the insulation cover, the collector performance can be improved by 70 per cent. Use of baffle plate improves the performance during day as well as night time.
Performance of a 160 m2photovoltaic installation at the Napier University's Merchiston Campus, situated 3 km from Edinburgh's city centre, is presented. The alternative current and direct current electrical outputs were recorded since the installation of the facility was completed in April 2005. An analysis of the efficiency of the facility, as well as energetic, environmental, and monetary life cycle assessments, using long-term meteorological data is presented in this article.
Thermally stratified storage in solar power systems is examined,
utilizing a simulation model and comparing results with previous
observations made on two actual solar heating systems in the
Netherlands. Although the benefits of stratification are small when the
mass flow rate is large, the good agreement between the simulation and
experimental results indicates that a more widespread utilization of
thermally stratified storage in combination with much lower collector
flow rates than usual will lead to considerable improvements in the
performance of solar space heating and hot water supply systems.
Experiments have also shown that the floating inlet, which is a wide,
thin-walled, flexible plastic hose connected to the inlet stud for
delivering the hot water from the collector at exactly the level of
temperature in the storage tank, improves the stratification by a factor
of 2 compared to natural stratification.
Solar domestic water heaters are usually forced circulation or thermosyphon heaters. A new design of heater in which the storage and collector are combined in one unit has been tested. The construction of the heater involves a rectangular box-like structure with the top face painted black and enclosed behind a single or double sheet of glass. The back surface and sides are insulated, with the assembly inclined at a suitable angle.The main advantages of such a heater are higher collection efficiency, due to direct contact of water with the absorber plate, and the absence of pipes connecting the collector to storage. In this study, the effect of storage volume/collector area ratio, number of glazings and mode of operation on the heater's performance was experimentally investigated.The work involved construction of three built-in-storage heaters, two of which had depths of 8 cm and one of 6 cm. The heaters were operated concurrently for 5 months in which measurements of heated water temperature, ambient temperature and insolation were made.Experimentation was carried out to study the effect of storage tank depth (volume/collector area) over a 4-month period by side-by-side operation of 6-cm and 8-cm heaters. The maximum and minimum temperatures recorded for the 6-cm heater were 76 and 46°C, respectively, while the corresponding temperatures for the 8-cm heater were 70 and 41°C, respectively. The day-average maximum efficiencies of the 6-cm and 8-cm heaters were 65 and 73%, respectively, with a difference of 8–10% throughout the observation period. The study of stratification on the two heaters showed no significant influence of the depth.The effect of glass covers was studied by tests on two heaters, both of 8-cm depth. One of these had a single glass cover while the other was double-glazed. The double-glazed heater performed better with a difference of 1–10°C in water temperature.Different modes of operation were studied by concurrent tests on two heaters of 801. capacity. The results showed that best performance could be obtained by drawing off all heated water into a separate storage as soon as it reached a pre-set temperature level (in this study 35°C). The heater was also found to be capable of handling intermittent loads quite easily.Finally, it is concluded that the built-in-storage heater performs quite well under Benghazi conditions, and the choice of 8-cm depth with double-glazing seems a good design optimum.
Energy is the prime source of human activities in all sectors of life. Traditionally fossil fuel has been the prime source of energy. However, there are two major concerns regarding fossil fuels, i.e. their rapid depletion and their contribution towards growing global warming. It is being widely realized that for sustainable development presently used energy mediums such as fossil fuel and nuclear power have to be quickly replaced by renewable energy sources. The latter are sustainable and have the potential to meet present and future projected global energy demands without inflicting any environmental impacts.
Researchers have discovered that by using low collector flow rates (roughly one-seventh of those that have been generally used) and by taking measures to ensure the water in the storage tank remains stratified, the energy delivered by a forced-flow solar system can be increased substantially. In addition, the lower collector flow rates permit substantial savings in system cost, mainly through reduction in plumbing costs. This paper reviews the state of the art in this highly promising change in approach. Items discussed include physical reasons for the predicted performance improvement, savings in system cost, current knowledge in tank stratification, methods of analyzing and computer-simulating the systems, and finally, full-scale system experiments.
The integrated collector storage (ICS) is the type of solar water heater that has retained its existance for well over a century. The flat absorber plate ICS collector type is a relatively recent addition. Being effective, low cost and simple to manufacture, their importance has been further enhanced by the recent upsurge in efforts to effectively tap renewable energy resources. Having different inclinations based on latitude, the design of flat plate heaters can benefit from extensive amount of research on the topic of natural convection in inclined cavities. More than half-century of exploration on inclined cavities has witnessed added activity particularly in the last three decades. Despite this consistent research, efforts to apply the outcomes to the flat plate collectors have been few and collectors reported in the literature appear to be deficient in embedding the knowledge into the design parameters. For an ICS type heater, natural convection studies gain even more weight as the apparatus is functionally an assembly of two natural convection cavities: an air cavity (space between the absorber and cover plates) and a water cavity (water storage tank). An extensive review of previous studies on inclined cavities relevant to flat plate collectors has been complied and discussed. Experimental tests of the ICS heater have been conducted for controlled heat flux up to 400 W. The thermal performance of the heater is recorded experimentally at angles 0–60° from horizontal, in 15° intervals. CFD analysis is also carried out for the same and is found to be in good agreement with previous studies. It was found that for any given constant value of heat flux, the performance of the heater is a strong function of the angle of inclination. The optimum configuration of the heater for Edinburgh conditions (latitude 55°55′N) is also evaluated. The present study also covers the convective behavior inside the water tank, which has been neglected in the past. A step-by-step build-up approach is adopted to resolve water tank behavior as its treatment as a simple natural convention cavity is invalid. This article would serve as a design guide for developing heaters tailored for a specific geographical location.
Two important aspects of short-term thermally stratified energy storage, thermocline mixing and thermocline thickness, are studied analytically, experimentally and numerically. The storage detrimental aspects are investigated for a simplified configuration, i.e. an adiabatic box containing a quasi-stationary thermocline. Numerical finite difference/volume simulations agree well with experiments. The dissipation-free 1D analytical model shows a large discrepancy. It appears that mixing inside thermally stratified stores is a two-stage process. First fluid is withdrawn from the thermocline by viscous drag. Subsequent mixing takes place by stretching and folding of fluid particles, thereby enabling diffusion to become active.
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