Flat Plate Receiver Research Articles

Performance of compound parabolic concentrator solar air flat plate collector using phase change material

This work involves an experimental investigation on two different new models of Compound Parabolic Concentrator (CPC) solar air flat plate collector with adding paraffin wax Phase Change Material (PCM). The first model is called involute shape model, whereas the second model is called normal shape model. To explore the best model performance, the structures of compound parabolic concentrator models have two symmetric giant parabolic mirror reflectors, similar concentration ratio of 1.7, similar flat plate receiver with 12 tubes filled by paraffin wax phase change material. The performances of both models are presented together for purpose of comparison. The tests have been performed in April and May 2023 in Mosul city/Iraq under standard conditions for around 11 h during the day. The outcomes indicated that rising in air mass flowrate leads to rise the receiver performance. The findings confirm that the thermal efficiency of normal shape is more efficient than involute shape by 7.6%, 13%, and 11.7% for 0.0085 kg/s, 0.0174 kg/s, and 0.027 kg/s, respectively. The optimum thermal performances for involute and normal shapes have been obtained equal 65.4% and 77.1% for 0.027 kg/s, respectively. For constant air flowrate, the performance of normal shape is higher than involute shape by 15.5% (14th May), 12.6% (27th April) and 11.8% (15th April). A significant temperature change has been found in involute shape as compared to normal shape. The outlet temperature of normal shape is always lower than the involute shape for all air mass flowrate. It is demonstrated that phase change material and the position of the receiver have considerable influence on the model performance. The current work provides an important information for evaluating the compound parabolic concentrator model performance for Mosul/city.

Performance analysis of a nanofluid spectral splitting concentrating PV/T system with triangular receiver based on MCRT-FVM coupled method

Optimizing system structure is one promising way to enhance the spectral beam splitting concentrating photovoltaic/thermal (SBS CPV/T) system performance. In this study, a linear Fresnel CPV/T system incorporated with triangular cooling duct and Ag@SiO2/ethylene glycol (EG) nanofluid filter is designed to enhance the overall performance of the system. To quantitatively reflect the heat generation of Ag@SiO2/EG nanofluid filter and silicon PV modules under inhomogeneous solar flux distributions, a coupled method combining Monte Carlo ray tracing (MCRT) method with Finite Volume Method (FVM) is employed. After validating the coupled method, the performance of the system with triangular receiver is discussed under various operating conditions. The results demonstrate that the nanofluid outlet temperature and PV module temperature present 316.3 K and 306.8 K at nanofluid inlet temperature of 298 K, respectively. The high mass flow rate and low inlet temperature allow high thermal and total efficiencies, while they present slight effect on electrical efficiency. To quantify the achievable enhancements with the triangular receiver, a SBS CPV/T system with flat-plate receiver is also discussed. It is found that the total efficiency of the triangular receiver is higher than that of the flat-plate receiver, with a maximum enhancement of 7.9%.

Computational Modeling of a Small-Scale, Solar Concentrating Device Based on a Fresnel-Lens Collector and a Flat Plate Receiver with Cylindrical Channels

The energy efficiency of a small-scale solar concentrating thermal device is investigated, based on Monte-Carlo Ray-Tracing (MCRT) and Computational Fluid Dynamics (CFD) modeling. The device consists of a Fresnel lens collector—engraved on a 1 m rectangular plate—and a 10 cm sized plate receiver, with drilled cylindrical channels with a diameter of 10 mm. Inlet velocities and heat transfer fluid (HTF) temperatures lie within the range of 0.25–1 m/s and 100–200 °C, respectively. The configurations examined involve the utilization of a selective coating on the absorbing surface of the receiver, increasing the channel diameter to 15 mm and the receiver size to 20 cm, and insertion of a glass envelope in front of the absorbing surface. Energy efficiency increases with increasing fluid velocity up to 80%, a level beyond which no further improvement is observed. The coating contributes to a reduction in heat losses; it brings substantial benefits for the lower velocities examined. The increase in channels diameter also contributes to an increase in the energy efficiency, while the increase in receiver dimensions leads to the opposite effect. The glass cover does not improve the performance of the collector, due to substantial optical losses.

Analysis and Research on the Performance of Solar Concentration Based on Big Data and Machine Learning

Empirical formulas for PTC optical efficiency calculation are difficult and costly to obtain from rigorous comparative experiments, whereas simpler optical modeling methods inadequately incorporate realistic optical effects. In this article, algorithms are respectively developed to calculate the geometric concentration ratio (Cg) of linear Cassegrainian solar concentrators (CSC) with a secondary flat mirror based on the way of edge rays from solar sources to a flat-plate receiver. On the basis of the large amount of data generated, machine learning and Python language programming methods are used to analyze and process the data, and the functional relationship between the concentration ratio and each parameter is obtained. The learning and training effect is good, and the ideal result is achieved.

Experimental study of compound parabolic concentrator with flat plate receiver

In this paper, an experimental work has been performed to investigate the performance of a new Compound Parabolic Concentrator (CPC) with a flat plate receiver model. The CPC structure has been designed based on the two offset large parabolas reflector surfaces with a concentration ratio equal to 1.5. The experiments have been carried out in winter 2019 from beginning of January to end of March using the solar radiation of Mosul city in Iraq under outdoor clear sky condition for around 8 h during the day. The experimental results indicate that the increase in water mass flowrates enhances the efficiency of the collector and reduces the outlet water temperature. The results show that the change in months from January to March has little impact on the total solar radiation. The maximum solar radiation has been recorded in March and the peak value has been observed between 12 PM and 1 PM. The results also indicate that the CPC provides a maximum efficiency 26.5% and hence, sufficient consideration should be taken while designing such CPC collectors. It is evident that CPC area has significantly effect on the collector performance. The present study provides a useful tools for calculating the efficiency of CPC for Mosul city.

On the thermal performance of flat and cavity receivers for a parabolic dish concentrator and low/medium temperatures

Application of parabolic dish collector systems working in a range of low/medium temperatures is of great importance in industrial practice. In this work, a thermal efficiency analysis will be performed for different receivers such as a flat-plate receiver and a cavity receiver (with and without a glass cover). Most of the previous receivers analyses found in the literature have been performed for applications with high temperatures. Moreover, a detailed analysis including losses such as reradiation, natural and forced convection, and conduction, have been performed, developing new correlations for natural and forced convention. The obtained results are discussed in detail, obtaining a significant increasing of efficiency of the cavity receivers against the flat-plat receiver with much less working temperatures: up to 20% for the covered cavity receiver in comparison with the flat-plate receiver, with a temperature reduction at the receiver of more than 450 °C.

Inverse heat transfer technique for estimation of focal flux distribution for a concentrating photovoltaic (CPV) square solar parabola dish collector

For a CPV system, prediction of focal flux distribution at the receiver area will give insight to more effective, energy efficient designs and to estimate power output. An experimental method for in-situ prediction of heat flux distribution profile using inverse heat transfer technique on a flat plate receiver for a CPV square parabolic dish is presented. An IR camera is used to measure the temperature of the concentrated receiver surface. The receiver domain is discretised into several heat flux elements and heat flux values for each grid is then estimated using the measured infrared (IR) pixel temperature and ordinary least square. A 3-D steady state heat conduction equation with convection and radiation heat loss boundary is regarded as the forward problem. The simulated temperatures generated from the solution of forward problem using the predicted heat flux distribution and measured temperature distribution are in close agreement. For validation purpose, the concentrated heat flux is also measured using Gardon and Schmidt-Boelter heat flux sensor. The peak predicted focal heat flux on the receiver is found to be 37.41 kW/m2 whereas the heat flux value measured by the flux sensor is 39.15 kW/m2 within the deviation of 4.4%.

Design Criteria for Micro-Optical Tandem Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) harness light generated by luminophores embedded in a light-trapping waveguide to concentrate onto smaller cells. LSCs can absorb both direct and diffuse sunlight, and thus can operate as flat plate receivers at a fixed tilt and with a conventional module form factor. However, current LSCs experience significant power loss through parasitic luminophore absorption and incomplete light trapping by the optical waveguide. Here, we introduce a tandem LSC device architecture that overcomes both of these limitations, consisting of a poly(lauryl methacrylate) polymer layer with embedded cadmium selenide core, cadmium sulfide shell (CdSe/CdS) quantum dot (QD) luminophores and an InGaP microcell array, which serves as high bandgap absorbers on the top of a conventional Si photovoltaic. We investigate the design space for a tandem LSC, using experimentally measured performance parameters for key components, including the InGaP microcell array, CdSe/CdS QDs, and spectrally selective waveguide filters. Using a Monte Carlo ray-tracing model, we compute the power conversion efficiency for a tandem LSC module with these components to be 29.4% under partially diffuse illumination conditions. These results indicate that a tandem LSC-on-Si architecture could significantly improve upon the efficiency of a conventional Si photovoltaic cell.

A two-layered solution for automatic heliostat aiming

The efficiency and safety of a solar central receiver system depend on the flux distribution reflected by the heliostat field on its receiver. Thus, the field must be carefully controlled to avoid dangerous radiation peaks and temperature gradients while also maximizing the efficiency of the system. Control tasks include deciding which heliostats to activate and where to aim them. The field is usually under direct human supervision, which is a potential limitation, and automatic aiming procedures are of great interest. This work proposes a general aiming methodology for flat-plate receivers. It intends to cover heliostat selection and aim point assignation to replicate any given reference flux distribution on the receiver. The methodology, which addresses this situation as a large-scale optimization problem, defines two consecutive stages. The first one handles heliostat selection by applying a specific genetic algorithm. The second one, based on a local gradient descent, assigns a final aim point to every active heliostat. The proposed methodology, in contrast to other existing methods in the literature, is not limited to achieve any specific target distribution. It exploits the analytical characterization of the considered field to minimize the accumulated squared error between any reference flux distribution and the achieved one. The results show very good replication quality and, considering its execution time, this method is suitable for preliminary and high-resolution field configuration.

Experimental investigation of the daily performance of an integrated linear Fresnel reflector system

The objective of this work is to investigate the daily and the instantaneous performance of a linear Fresnel reflector (LFR) experimentally and numerically. The examined LFR has an inverted flat plate receiver with a 36 m2 total collecting aperture area and is coupled to a storage tank of 1 m3 volume. This system is investigated experimentally for daily operation in the period from May to October for the climate conditions of Athens (Greece), using water as the working fluid (temperature levels up to 100 °C). Moreover, a detailed mathematical model for the prediction of the instantaneous and of the daily performance is developed. This model is validated with the experimental results for 52 operating days and it estimates the daily useful energy production with a mean error of 3%. This modeling is based on the energy balance on the collector loop and the storage tank. The emphasis is given on the determination of the optical losses of the collector, which are associated with the sun position during the day. It is found that the maximum useful heat production is about 8.4 kW, while the maximum daily heat production is about 260 MJ. The results of this work can be exploited for the evaluation of integrated solar concentrating systems and especially of linear Fresnel reflectors.

Optical analysis of a novel collector design for a solar concentrated thermoelectric generator

This paper proposes a novel design for a solar concentrated collector for thermoelectric power generator (SCTEG), with optimum power output per unit length of collector. This collector consists of a parabolic trough concentrator (PTC) and a receiver mounted with two thermoelectric generators (TEGs) along the aperture of the concentrator. In addition to assessment of the conventional design parameters, this study investigates the effects of two new geometrical parameters on the optical performance of SCTEGs. These parameters are the vertex angle between the inner surfaces of the TEGs, and the focus offset, which is the displacement of the vertices of the TEGs above or below the focal point of the concentrator. A geometric model, which develops the basis of a ray-tracing technique for performing the optical analysis, is also described. Simulations performed for a set of design parameters showed that both parameters affected not only the optical efficiency but also the local flux distribution (LFD) on the surface of the TEGs. Iso-optical efficiency contours and numbers of LFDs were plotted, taking different values of these parameters to determine optical efficiencies. A flat-plate receiver configuration showed 85.2% optical efficiency but with a single high peak in LFD at the centre, which was undesirable. A slight alteration in vertex angle and focus offset resulted in same optical efficiency but improved LFD. The highest optical efficiency determined was 93.61% for the wide-receiver configuration. A thermodynamic analysis of the SCTEG design is also presented. This research work will assist in the development of more efficient SCTEGs.

Experimental investigation of the comparison of compound parabolic concentrator and ordinary heat pipe-type solar concentrator

In this research study, we have compared between the two different concentrators with the flat absorber plate receiver of the compound parabolic concentrator heat pipe solar concentrator and ordinary heat pipe flat plate solar concentrator. For the reproduction of solar radiation in the experiment, iodine tungsten lamp was used. Thermal performance comparison of the two types of solar concentrator under different simulating radiation intensity conditions was carried out with including the fluid temperature, instantaneous efficiency, average efficiency, and average heat loss coefficient. The results of the experiment indicate that the compound parabolic concentrator heat pipe-type solar concentrator not only increased the fluid temperature and instantaneous efficiency but also decreased the average heat loss coefficient as compared with the ordinary heat pipe flat plate solar concentrator. It was noticed from the experimental results that the efficiency of compound parabolic heat pipe solar concentrator was higher than ordinary heat pipe solar concentrator up to 6 and 10°C with the light intensity, that is I = 679 W/m2 and I = 892 W/m2, respectively. From the results, it was concluded that the using of compound parabolic heat pipe solar concentrator increased the thermal performance of solar concentrator.

In-situ prediction of focal flux distribution for concentrating photovoltaic (CPV) system using inverse heat transfer technique for effective design of receiver

The knowledge of heat flux distribution on the receiver area is very important to improve the overall performance of the solar Concentrating Photovoltaic (CPV) system. In a CPV system, non-uniform flux distribution is one of the common issues. Non-uniform illumination of heat flux is mainly due to the limitations in the design of concentrator optics, slope error in the concentrator profile, tracking system error, misalignment of concentrator, and the efficiency of refractive lens/reflecting mirrors. The prediction of the heat flux distribution will play a vital role in the CPV system such as designing the receiver area, selection of the materials, thermal management and to estimate the power output. In this paper, an experimental work for in-situ prediction of heat flux distribution profile on a flat plate receiver is presented. Inverse heat transfer technique is adopted to predict the heat flux distribution. A Gaussian distribution is assumed to model the distribution of the heat flux. The forward problem is a 3-D steady state heat conduction equation subjected to convection and radiation heat loss boundary conditions.The forward problem is solved using Finite Element Method in Ansys APDL. The unknown parameters of the assumed heat flux distribution are then estimated by minimizing the sum of squared error between measured and simulated temperature distribution. A deterministic search technique, Levenberg-Marquardt algorithm is used to solve the inverse problem. The simulated temperature distribution with the predicted heat flux are in good agreement with the measured temperature with a maximum residue of ±5 °C. Also, the deviation between theoretical and predicted total solar energy is found to be <6%.

Experimental and theoretical performance investigation of asymmetric photovoltaic/thermal hybrid solar collectors connected in series

Abstract In this study five asymmetric hybrid solar collectors with flat plate receiver connected in series are investigated experimentally and mathematically through analytical expressions deriving from heat transfer and thermodynamics fundamentals. The main objective of this study is to evaluate the collectors' performance in terms of thermal energy and exergy production under various operating conditions thus the experiments are performed at open circuit mode regarding their electrical part and with water as working fluid. Concerning the theoretical analysis, the developed model combines optical, thermal and flow analysis for the determination of both first and second law efficiencies and it is validated against experimental data with an acceptable agreement being observed. Following the model validation, the performance of the collectors is analyzed in terms of thermal and exergy efficiency, thermal losses and absorber temperature. After the thermal analysis, the mathematical model is further developed so as to take into account the electrical production for the overall performance evaluation of the compound parabolic PVT solar collectors. Among the main findings, the final experimental results proved that these solar collectors connected in series work efficiently throughout the year as they are able to produce about 2.2 kW useful energy in summer, 2.8 kW in spring and 2.6 kW in autumn.

Optimisation of aiming strategies in Solar Power Tower plants

The distribution of temperature on a Solar Power Tower (SPT) plant receiver directly affects the lifespan of the structure and energy generated by the plant. Temperature peaks and uneven distributions can be caused by the aiming strategy enforced on the heliostat field.A non-optimised aiming strategy can lead to suboptimal energy generation and, more importantly, to risk of permanent damage to receiver components from thermal overloading due to sharp flux gradients.In order to reduce damage to receivers and optimise the energy generation, an aiming strategy is developed which homogenises the flux distribution on a flat plate receiver in a SPT plant.Results of a near real-time optimised aiming strategy are presented, demonstrating applicability to SPT plants of any size and shape, whilst also considering inclement weather conditions.

Modeling and Simulation of an Absorption Solar Cooling System Under Iraqi Weather Conditions

This work aims to model and simulate an absorption cooling system using solar flat- plate receiver with water lithium bromide (li.Br-H2O) mixture as a working fluid, and to select the optimum type for absorption cooling system, which have suitable application in Iraq. Weather conditions for Erbil city have been selected. Coefficient of performance (COP) for a single, double (series and parallel), half and triple effect of an absorption cooling system are calculated and optimized. COP Prediction, hot water temperature, and the rate of heat transfer have been simulated and represented by using TRNSYS and EES programs. Active area of the solar flat-plate receiver is calculated and optimized for five suggested areas of (140, 150, 160, 170, and 180 m 2). Average heating load, average daily - radiation and cooling load for summer months (June, July, August, and September) have been calculated. The results indicated that, the superior type of the four absorption-cooling systems is a single effect, which has COP 80% at generator temperature of (81 °C). Also the results indicated that the optimum area of solar flat-plate receiver was 160 m2 which has achieved the maximum capacity of cooling power and consumed capacity in the generator (50, and 62.5) kW respectively. I think, according to the previous studies , the current work is the first in Iraq because it approved that, single effect type is an efficient and more relevant type for good working under Iraqi climate by using solar flat–plate receiver and suitable to apply it experimentally in a wide range.

Experimental and numerical investigation of a linear Fresnel solar collector with flat plate receiver

In this study a linear Fresnel solar collector with flat plate receiver is investigated experimentally and numerically with Solidworks Flow Simulation. The developed model combines optical, thermal and flow analysis; something innovative and demanding which leads to accurate results. The main objective of this study is to determine the thermal, the optical and the exergetic performance of this collector in various operating conditions. For these reasons, the developed model is validated with the respective experimental data and after this step, the solar collector model is examined parametrically for various fluid temperature levels and solar incident angles. The use of thermal oil is also analyzed with the simulation tool in order to examine the collector performance in medium temperature levels. The experiments are performed with water as working fluid and for low temperature levels up to 100°C. The final results proved that this solar collector is able to produce about 8.5kW useful heat in summer, 5.3kW in spring and 2.9kW in winter. Moreover, the operation of this collector with thermal oil can lead to satisfying results up to 250°C.

Performance comparision of a new-type trough solar concentrator thermal system in different installations

Original scientific paper DOI: 10.2298/TSCI140127001C This paper puts forward a new-type trough solar concentrator with a compound surface, which is comprised of two upper paraboloids, lower planar mirrors, and one base paraboloid. This structure forms a co-focus where a solar receiver is installed. The performance of the new-type trough solar concentrator combined with a cylinder receiver and a flat plate receiver, respectively, was tested. For comparison, the reflector of the concentrator was made of a polished aluminum sheet and a mirror glass, respectively. The experimental results show that the prototype concentrator systems may have an average efficiency around 40% for the hot water temperature up to 80 °C and the ambient temperature below 0 °C in winter. To test and verify the performance of the system in higher temperature range, a scaled-down new concentrator of the same structure was made and tested in the outdoor. It was found from the results that the designed new-type trough concentrator can produce 220 °C solar heat. It indicates that the proposed design may be promising for solar thermal application at a medium temperature of 80 °C -150 °C.

Control of the flux distribution on a solar tower receiver using an optimized aiming point strategy: Application to THEMIS solar tower

Life time of components is one of the technological bottle-necks in the development of solar tower power plant technology. The receiver, which is subjected to high and variable concentrated solar flux density is particularly affected: High, variable and non-homogeneous solar flux on the solar receiver walls results in strong stresses because of high temperatures, thermal shocks and temperature gradient that contribute to the reduction of the life time of this key component. This work aims to present an open loop approach to control the flux density distribution delivered on a flat plate receiver for a solar power tower. Various distributions of aiming points on the aperture of the receiver are considered. The flux density distribution on the aperture is simulated by a computer code. A specific neighborhood is defined for the TABU optimization meta-heuristic according to the size of the image of each individual heliostat. This modified algorithm is implemented to select the best aiming point for each heliostat. This approach has been validated using the example of THEMIS solar power tower in Targasonne, France.

OS1702 太陽集光シミュレータ用平板型レシーバ模型の温度・ひずみ計測に関する基礎的研究

OS1702 太陽集光シミュレータ用平板型レシーバ模型の温度・ひずみ計測に関する基礎的研究