Beam Solar Radiation Research Articles

Integrating solar-powered branched GAX cycle and claude cycle for producing liquid hydrogen: Comprehensive study using real data and optimization

The present study introduces a novel hydrogen liquefaction system that integrates a Claude cycle and a branched GAX cycle, marking the first instance of such a combination. Utilizing solar energy improves hydrogen manufacturing efficiency and sustainability. This research uses actual data to estimate the best operating time by examining thermodynamic performance, payback duration, exergoeconomic parameters, environmental effect, and sustainability. A current bi-objective optimization technique maximizes exergy efficiency and minimizes hydrogen liquefaction cost. Evaporator and generator temperatures, solar direct beam irradiation, and cycle's high pressure are key decision variables. The sensitivity analysis highlights the substantial influence of cycle's high pressure on hydrogen liquefaction cost, as indicated by a sensitivity index of 0.486. The research calculates the best solution using TOPSIS decision-making, resulting in 50.22 % exergy efficiency and $1.366/kg hydrogen liquefaction cost. After conducting a thorough case study, it becomes evident that May is the most optimal month for liquid hydrogen production, payback period, and net profit. However, January has a high coefficient of performance and exergy efficiency and low liquid hydrogen production cost. The cheapest capital investment month is July. This complete study of the solar-driven hydrogen liquefaction system uncovers critical parameters and their effects, enabling hydrogen production efficiency and sustainability.

A novel micro non-imaging concentrating solar module for building façade integration

Owing to the limited installation space and relative low energy density of solar radiation, how to fully utilize the solar energy potential on the building south façade is always an important issue. In this regard, this paper proposed a faced embedded solar thermal module with mini asymmetric parabolic concentrator, which could capture solar radiation within a wide range of incidence angles with relatively high thermal conversion efficiency. The optical efficiency of the proposed solar module maintains over 0.7 with the solar projection angle increasing from 0° to 90°, which covers the annual altitude angle variation of beam solar radiation incidence on the south façade. Corresponding photo-thermal model was developed and validated with 5 days continues outdoor measurement data. The predicted values were in good consistence with the experimental data with a R2 value of 0.975. Experimental results showed a daily thermal efficiency of 0.66 during the clear sky weather. The average daily thermal efficiency of the ACPC module throughout the year was 0.47 with a constant working temperature of 60 °C. The proposed device is expected to help the building integration design towards zero carbon emission building.

Design optimization of a new cavity receiver for a parabolic trough solar collector

The most important parameter affecting the optical efficiency, the upper limit for an overall efficiency of parabolic trough solar collector (PTC), is the net absorbed heat rate by receiver on which solar beam radiation is concentrated. The objective of this study is to propose and optimize a new cavity receiver used in PTC for increasing optical efficiency. Three different geometries (triangle, rectangle and polygon), aperture widths, heights and positions of cavity receiver are taken as optimization parameters. A design of experiments (DoE) approach is used to evaluate the effects of these parameters on the absorbed radiation heat rate by receiver at the same time. SolTrace is used to investigate the effects of these parameters by optical analysis. The results indicate that the optimum cavity geometry is polygonal, and the cavity depth and aperture both are equal to 0.05 m. Moreover, it is found that the most effective parameter is the position of the cavity receiver, and the optimum position is at the focal line of the parabolic concentrator. The highest absorbed radiation rate by the cavity receiver and the optical efficiency of the PTC are equal to 3241.99 W and 81.05 % respectively for the optimum cavity receiver design.

Comparison of entransy loss analysis and the first law of thermodynamics in the optimization of organic Rankine cycle coupled with parabolic trough collector

Due to the numerous environmental issues associated with fossil fuel power plants, using solar energy to generate electricity is a viable alternative. The organic Rankine cycle (ORC) is a thermodynamic process used to convert low- and medium-temperature heat sources into electricity, often utilizing organic fluids as the working medium. Entransy is a relatively new concept that many readers may not be familiar with. Moreover, entransy loss (Ġloss) is derived from the entransy concept, which quantifies the inefficiency in transferring thermal energy through a system. In this study, (Ġloss) is used for the first time when designing an ORC cycle coupled with parabolic trough collectors. The entransy loss relations were driven with assumption that the heat capacity is a function of temperature. A genetic algorithm is a search heuristic inspired by natural selection. It is used to find optimal or near-optimal solutions to complex problems by evolving a population of candidate solutions. Two scenarios utilized the genetic algorithm in MATLAB to optimize the system (scenario 1: maximizing the output power and scenario 2: maximizing the Ġloss). In addition, the optimization parameters included turbine inlet temperature (Ttur), boiler pressure (Pboil), condenser pressure (Pcond), and the temperature of the collector fluid at the boiler outlet (Thf,out). This optimization was performed for the temperature of the collector fluid at the boiler inlet (Thf,in) in the range 310–400 °C at 10 °C intervals with four working fluids (i.e., toluene, cyclohexane, MM, and water). The land area and the beam solar radiation were considered to be 100 hectares and 800 W/m2, respectively. The results indicated that according to scenario one, at temperatures of 310–320 °C, the maximum power was obtained for the case of toluene fluid with values 59.8 and 63.5 MW. For the collector fluid temperature from 330 to 400 °C, water had the most optimal power with values ranging from 66.2 to 88.2 MW. Furthermore, toluene exhibited superiority to two other organic fluids in the 330–400 °C temperature range after water, with net power values ranged between 65.7 and 76.3 MW. The results indicated that the maximum entransy loss does not correspond to the maximum output power because the application preconditions of the entransy loss concept are not all satisfied. Across all working fluids and Thf,in, scenario 2 resulted in lower optimal output power, cycle efficiency, and system efficiency compared to scenario 1.

Exergo-economic analyzes of a combined CPVT solar dish/Kalina Cycle/HDH desalination system; intelligent forecasting using artificial neural network (ANN) and improved particle swarm optimization (IPSO)

Power and freshwater are two energy-intensive products, which consume a huge amount of fossil fuels. It is important to supply the aforementioned products using renewable energy sources due to the depletion of fossil fuel resources and environmental issues. This paper investigates the exergy and exergy-economic analysis of water and power production using a small-scale combined cycle encompasses the concentrated photovoltaic thermal (CPVT) solar collectors, a Kalina cycle (KC), and a humidification-dehumidification (HDH) desalination unit. An exergo-economic parametric analysis was first investigated to determine the influence of some pertinent parameters on the exergy efficiency, and specific unit cost of the products. In the second stage, two intelligent forecasting approaches based on the artificial neural network (ANN) and improved particle swarm optimization (PSO) algorithms were utilized for predicting the performance metrics of the studied system. The system was supposed to work at half of the year's hour. The results demonstrated that the shares of CPVT, generator, humidifier, dehumidifier, and condenser in exergy destruction are 84 %, 6 %, 3 %, 2.5 %, and 2 %, respectively. Moreover, the exergy efficiency, and specific unit cost of the products, unit cost of electricity, and unit cost of the fresh water at the design condition were obtained as 23.23 %, 0.0806 $/kWh, 5.44 $/m3, and 31.15 $/GJ, respectively. Besides, the most effective parameter on the exergy efficiency and the specific unit cost of the products was the solar beam radiation, the increment in which from 300 W/m2 to 1000 W/m2 improved the exergy efficiency by 15.21 % and reduced the specific unit cost of the products by 63.16 %. In addition, the increase in the condenser pressure from 15 bar to 22 bar and the generator pinch point temperature difference from 5 °C to 15 °C reduced the exergy efficiency by 8.13 % and 4.03 %, respectively, leading to increasing the specific unit cost of the products by 1.30 % and 4.30 %. The results of modeling showed that hybrid ANN-IPSO models provide the most accurate prediction, highest tendency, and agreement to observation as compared to ANN in terms of (R2| exergy efficiency = 0.9903 and R2| specific unit cost of products = 0.9948) and (RMSE| exergy efficiency = 0.0010 and RMSE| specific unit cost of products = 0.9684).

Experimental and numerical study of a linear Fresnel solar collector attached with dual axis tracking system

The demand for an alternative to fossil fuel energy is increasing as environmental and economic challenges rise. The linear Fresnel solar collector is considered a promising option for obtaining thermal energy at medium and high temperatures. A linear Fresnel solar collector consists of a number of mirror strips that are used to focus solar beam radiation toward a line receiver. This study aims to obtain a clear evaluation of the thermal performance of a linear Fresnel solar collector through design, manufacture, and experimental testing under different outdoor conditions in Baghdad over various periods. There have been tests on April 1 and 22, as well as May 8 and 27, using water as the working fluid. The solar collector used is an aluminum base measuring 200 cm in length and 150 cm in width on which 14 mirror strips from each side are fixed. The receiver (absorber copper tube) has a length of 200 cm and a height of 60 cm from the base. The solar collector is provided with a dual-axis tracking system (North-South and East-West) for ensuring that the solar concentrator faces the sun at normal incidence during all daytime hours. The best thermal performance of the solar collector was observed on May 27, where the average useful energy, thermal and exergy efficiency reached 1042.61 W, 39.15 %, and 1.31 %, respectively. The present study also included a numerical analysis done using computational fluid dynamics (CFD) to verify the experimental results. The numerical results confirmed the validity of the experimental results.

Energy response of a mono-axis tracked solar thermal collector with vacuum tubes

. Looking towards a sustainable future, Transilvania University of Brasov develops many projects on diverse renewable energy conversion systems; this paper presents a solar tracked solar thermal collector (STC) system, designed for a future implementation on Transilvania University campus. The specific requirement is that the STC system has to be configured to keep a zero energy response during the summer holydays (when the energy consumption is null). The proposed solution describes a mono-axial solar tracking system designed to perform an annual step wise tracking program to capture the most of the available solar energy using a solar thermal collector (STC) with vacuum tubes. The tracking program represents an optimised step tracking law developed in dependence with the diurnal movement of the sun. Numerical simulations are done for one year interval, for Brasov Romania geographic site, to evaluate the daily variations of: the pseudo-equatorial solar angles (γ, β); the pseudo-equatorial tracking angles (γ*, β*); the incidence angle; the available beam solar radiation (B) and the beam received solar radiation by the STC system (B*). The energy response of the tracked STC, for Brasov, Romania, is evaluated considering both clear sky and cloudy sky conditions, while neglecting the diffuse radiation effect.

Analysis of the light performance of Chinese solar greenhouse with internal insulation based on a solar radiation model

Chinese solar greenhouses are important agricultural building facilities with highly efficient and sustainable solar energy consumption. A solar greenhouse with an external insulation blanket for heat preservation is the most prevalent type of CSG. However, greenhouse performance degrades as the thermal insulation performance of the external blanket deteriorates over time when the blanket is exposed to harsh environmental conditions. Moreover, the external blanket is usually parked in an inconvenient location on the south roof in the practice, resulting in shading owing to its increasing coverage length. This significantly influences the solar radiation received by the south roof and that projected on the wall, ultimately affecting the light performance of the greenhouse. Therefore, a solar greenhouse with an innovatively applied internal insulation system was proposed in this study. To analyze the light performance of the solar greenhouse, a solar radiation model was established and verified by comparing the measured and calculated values. Based on the calculated model results, the spatial distribution of solar radiation inside the greenhouse and its allocation to the interior surfaces of the greenhouse were simulated. The total captured and transmitted solar radiation accumulations were compared for three different roof shapes. The captured and transmitted radiation accumulation of the greenhouse with internal insulation increased by 3.9–9.5 and 1.8–4.4 MJ compared to the two other greenhouses, respectively. The effect of the position of the parked blanket on the beam solar radiation projected on the wall and ground was considered. The results indicated that the increased blanket coverage length decreased the cumulative radiation on the wall by 25.24%–99.82%, which did not contribute to improving greenhouse energy-saving production. This study provides a new approach to greenhouse design and optimization.

Heat Transfer Model of Curtain Wall Facade Systems under Insolation

This paper deals with the problem of creating the basis of microclimate regulations and increasing the energy efficiency of various types of curtain walls in relation to the building thermal air envelope. The aim of the study is to distribute the heat flux flowing through the experimental envelope and determine the minimum temperature on the inner surface of the facade to develop a heat transfer model and increase the energy efficiency of curtain walls. The research methods are known scientific and technical results analytical generalization, the processes under study physical and mathematical modelling, the provisions theory of probability and mathematical statistics implementation, and fullscale experimental research. A computational model of heat transfer through curtain walls of various types is developed in relation to multiple reflections (absorption) of their surfaces in hot climatic conditions when the heat flux of beam and diffuse solar radiation passes through. Optimization of curtain wall with modern shading systems is considered. Comparison of the characteristics of similar experimental setup with traditional translucent curtain walls confirms the simulation. The proposed curtain wall with shading systems significantly improves the energy performance in the warm season compared to traditional curtain walls. A methodology based on modern computational methods that allow more accurate consideration of heat transfer through curtain walls in relation to the insolation of thermal building air envelope was developed. The methodology improves the quality of building design and microclimate and energy savings for indoor air conditioning.

Incorporating theoretical and practical approaches to assess the amount of sunlight captured by a tilted surface in a tropical climate

Global solar radiation can theoretically be approximated in terms of tilt and azimuth of the surface regarding the impossibility of simultaneous measurement of solar radiation at various surface tilt and azimuth angles. Moreover, the random and anisotropic nature of diffuse radiation in a tropical climate makes it extremely difficult to estimate global solar radiation accurately as a function of surface tilt and azimuth angles. This study aims to develop a novel experimental and theoretical approach in the form of a computational network in order to determine a precise combined model integrated with global horizontal solar radiation to evaluate global tilted solar radiation in a tropical climate. Obtained results revealed that precisely estimation of the global tilted solar radiation was possible, by combining geometric factors for the tilted beam solar radiation, a combination of Gueymard and Louche models for the tilted diffuse solar radiation, and isotropic ground reflectance model for the ground reflected radiation, along with global horizontal solar radiation. It was observed that the accuracy of the model developed was higher for the partly sunny sky compared to the cloudy and rainy sky, estimates were more accurate on south-facing surfaces, and the model's accuracy declined with the increasing tilt angle of the surface. The statistical analysis exhibited excellent agreement between the measured data and simulation results, considering the value of normalized mean absolute error (nMAE %), normalized root mean squared error (nRMSE %), and mean absolute percentage error (MAPE %), which were in the ranges 0.22–0.94, 0.27–1.11, and 0.23–1.02, respectively for estimating global tilted solar radiation in various regions of Peninsular Malaysia, and they were respectively found in the range of 10.2–27.5%, 16.1–38.9%, and 6.0–17.8%, for evaluating the monthly optimum tilt angle towards the south, that leads to a loss of solar energy from 1.3 to 5.4 kWh/m2/year in Peninsular Malaysia. This search revealed that the experimental and theoretical approach employed in this study can be extended to more climatic regions.

Mathematical modeling of a binary ORC operated with solar collectors. Case study—Ecuador

<abstract> <p>The present study is significant because it can contribute to developing sustainable energy strategies and expanding knowledge about renewable energies in Ecuador, specifically by modeling two modules: the thermal module (parabolic solar collectors and energy storage tank) and the Organic Rankine Cycle (ORC) module. The objective was to determine a region in Ecuador where the thermal module exhibits the highest efficiency for solar collectors. Subsequently, a detailed analysis of the ORC module was conducted, considering the working fluid, boiling temperature, condensation temperature, pinch point temperature, solar collector area, and the collector area-to-energy storage volume ratio (<italic>Ac/V</italic>). Finally, an economic analysis was performed based on the Net Present Value (NPV), Internal Rate of Return (IRR), and payback period of implementing this type of system. After conducting all the respective analyses in the thermal module, while considering the yearly average meteorological data of ten years (2012–2022), it was determined that due to its meteorological conditions, ambient temperature (14.7 ℃) and solar beam radiation (184.5 W/m<sup>2</sup>), the efficiency of the collectors in the Andean region of Ecuador is higher. This efficiency is further enhanced by using Therminol VP-1 as the thermal fluid, as it possesses better thermodynamic properties than the other fluids analyzed. Similarly, the ORC module analysis results determined that cyclohexane is the working fluid for the ORC, thereby leading to a higher ORC efficiency (25%) and overall system efficiency (20%). Finally, the system was optimized to maximize the IRR and minimize the <italic>A</italic>c/<italic>V</italic> of the collector for a nominal power of 92 kW. As a result, the optimal operating conditions of the system include a solar collector area of 1600 m<sup>2</sup>, an energy storage tank volume of 54 m<sup>3</sup>, an electricity production of 23757 MW/year, a total system efficiency of 22%, an IRR of 15.65% and a payback period of 9.81 years.</p> </abstract>

Simultaneous design and control optimization of smart glazed windows

The paper examines the benefits of simultaneous optimization of various design and control parameters for smart glazing windows of office buildings. The design variables include the window U-value, solar heat gain coefficient (SHGC), visible transmittance (Tvis), and window-to-wall ratio (WWR). The tint-switching control strategies reviewed include outdoor air temperature (OAT), indoor air temperature (IAT), incident total solar radiation (ITSR), and incident beam solar radiation (IBSR). These variables are optimized independently and simultaneously to determine the best specifications to minimize operating costs while maintained desired thermal and visual comfort levels. Specifically, electrochromic (EC) smart glazed windows are optimally designed and controlled when installed for a prototypical medium office building in Denver, Colorado. The optimization analysis results are considered to determine the breakeven installation costs required for smart glazing systems to be cost competitive compared to their static glazing counterparts. The analysis found that the annual energy cost savings from optimally designed and controlled smart glazed windows ranged from 11% − 18%. Of the design parameters, the U-value proved to be the most impactful on energy and cost reductions, followed by SHGC and WWR. Indoor and outdoor air temperature-based controls are determined the most effective operation strategies. Simultaneously optimizing for the design and control parameters provided the highest annual savings.

Hybridization of statistical machine learning and numerical models for improving beam, diffuse and global solar radiation prediction

Prediction, separation, and improvement of beam (Hb), diffuse (Hd), and global solar radiation (H) using an efficient Gumbel probabilistic model (GP) and hybridization of GP with auto-regression integrated moving average (ARIMA) is essential in regions of Southern Africa and the Middle East. This is because, most of the inhabitants of these localities are not connected to the national grid due to extreme cost implications, frequent power outages, and in most cases, unavailability of the national power supply; as well as the fact that most government meteorological stations are technologically or financially unable to routinely measure these radiometric parameters in most metropolitan cities, developing cities, and remote villages, where there is a severe need for electricity. Although the prediction of H has many advantages in adapting and deploying clean and affordable energy infrastructure through solar photovoltaic (PV) systems, the separation of H into Hb and Hd will further increase cleaner and more affordable systems like solar PV thermal/concentrators, which require Hb for its use. In this era of climate change, Hb, Hd, and H information are needed to detect and adapt climate mitigation plans in places adversely affected by climate change and global warming externalities. Eight different configurations of input combination elements were assembled to stimulate their hybrid evolutionary ARIMA-GP controlled, swapped model through the instrumentality of generalized solar meteorological datasets needed for modeling. The result revealed that the swapped ARIMA models outperformed the controlled and controlled ARIMA models using Gumbel's numerical approach. The best min beam and diffuse irradiance frocontrolled ARIMA models were probabilistically optimized using the Gumbel (GP) probabilistic model to produce ARIMA-GP. From the evaluations of the error metrics, the ARIMA-GP models outperformed the swapped and controlled ARIMA models, as well as the Gumbel models used to separate HB and Hd from H. The selected best performing models produced the RMSE-induced decrease and increase in R2 of 73.73% and 15.25% respectively for GSRML-GP3 (model H), 71.71%, and 14.19% for DSRML-GP5 (model Hd), and 61.91% and 11.70% for DNIML-GP5 (model Hb). These high values of the percentage improvement of the suitable model obtained for the Hb, Hd, and H modeling suggest that the proposed hybrid evolutionary ARIMA-GP model can be adopted to improve the prediction of solar beam, diffuse and global radiation in any region of the world, as the input parameters incorporate the data sets on geo-climatic conditions needed for global modeling. This study also suggests that it is more realistic to use the generalized functional forms GP and ARIMA-GP to separate Hb and Hd from the parameter H and also to generate their corresponding coefficients in the studied regions than applying empirical and machine learning models consolidated in the literature. The proposed ARIMA-GP models are sufficient as a valid evolutionary hybrid model that will accelerate a holistic understanding of the solar resources available in the selected regions and beyond, as well as spread the application of solar photovoltaic/thermal technologies within these countries.

Occupant-centered evaluation on indoor environments and energy savings of radiant cooling systems with high-intensity solar radiation

Solar radiation has an overwhelming influence on indoor thermal and light environments, as well as building energy consumption. In this study, radiant cooling systems were applied to reduce the negative effects of solar radiation. The tests were carried out with the floor radiant cooling system (FRC), ceiling radiant cooling system (CRC), ·and conventional air conditioning system (AC), under typical warm days. An occupant-centered body model was presented to comprehensively evaluate the non-uniform thermal environment caused by solar heat. Besides, the effects on the cooling performance of cooling systems were evaluated by simulation and experiments. The results demonstrate that the cooling capacity rapidly increased with the intensity of the solar radiation. During beam-exposed period, cooling capacity of FRC system increased from 55.6 W/m2 to 210.0 W/m2 and the proportion of shortwave radiant heat flux qsr reached 84%. Furthermore, solar radiation also deteriorated the non-uniform thermal environment. The FRC system could reduce the mean radiant temperature by the maximum of 8.0 °C. Exposed to the beam solar radiation was the main reason that caused large vertical stratification of temperature and dissatisfaction. The FRC system effectively performed better with the maximum percentage dissatisfied value reduced by 14.76 %. Finally, the energy-saving potential of RC systems was analyzed. After the set-point temperature was corrected, the FRC system reduced the typical day’s energy consumption by 21.7% and annual energy consumption by 12.2%. Appropriate adoption of RC systems is an energy-saving method to improve thermal comfort of indoor environments with high-intensity solar radiation.

PERFORMANCE EVALUATION OF PARABOLIC CONCENTRATOR WITH THERMAL STORAGE SYSTEM FOR DOMESTIC APPLICATIONS

Solar energy is a free natural resource but its harvesting requires a high capital investment whichprohibits its maximum exploitation. A Parabolic Dish Solar Collector (PDSC) with a thermalstorage system was been constructed and developed to harness solar beam radiation. The thermalstorage system and PDSC were constructed using locally and less cost materials such asgalvanized metal sheet and steel rods curved to obey the equation of a parabola then weldedtogether with circular support rings which was then lined with stainless steel reflector pasted forthe construction of PDSC. The receiver was made of blackened aluminium material incorporatedwith coiled copper tube carrying water as the heat transfer fluid. A parabolic dish which acts of aheat collector is used to track and reflects solar radiation at a single point (focus) on a receiverabsorber. Heat transfer from the solar collector to the storage tank was done by usingthermosyphonic principle to circulate the water (heat transfer fluid) between storage tank andheating system (receiver). The evaluation of thermal storage and analyzing the efficiency oftracking and non-tracking parabolic dish solar collector was carried out during month of June,2020 for the composite climate of Sokoto. According to the finding, the efficiency of trackingPDSC with thermal storage system and non- tracking PDSC with thermal storage tank weredetermined and obtained to be 52.9% and 50% respectively.Keywords: thermal efficiency, parabolic dish collector, solar radiation, storage system andstainless steel reflector.

Reconsidering beam and diffuse solar fractions for agrivoltaics

The concept behind agrivoltaics, the use of photovoltaics (PV) with agriculture to simultaneously produce electric power and food, was first introduced by Goetzberger and Zastrow (1982) (GZ), who developed models for shading effects of fixed, opaque, monofacial PV panels on beam and diffuse solar radiation reaching the ground. This article has been cited by many since 2000. However, since then nearly all authors of related papers that cited GZ have not adopted the GZ models. Instead, ray-tracing and other methods have been used in custom computer codes. The reasons might be rooted in limitations of GZ assumptions or the need for algorithms to accommodate individual experiments and systems. Another may be lack of a complete expression for a key angle in the shadowing problem and an integral expression for diffuse solar fraction that produces suspicious results in GZ. In this work we provide a simpler, complete, and validated model for the diffuse solar fraction, add insight into the interactions between a panel and its neighbors, and the number of PV panels needed through shadowing to reach an asymptotic value. By normalizing the problem, plots of diffuse and beam solar fractions are enabled that form the basis of simple tools useful for first-order estimates in design. A design case study is presented against which results of the current work are favorably compared.

Model construction and performance investigation of multi-section compound parabolic concentrator with solar vacuum tube

Multi-section Compound Parabolic Concentrator (M-CPC) has advantages of non-tracking device, adjustable operation time, concentrating diffuse radiation, convenient system integration, etc. In this study, the structure optimization, experimental verification and optical performance analysis of M-CPC with solar vacuum tube absorber are investigated. Combined with Monte Carlo Ray Tracing (MCRT) method and Particle Swarm Optimization (PSO) intelligent algorithm, based on Novel Compound Parabolic Concentrator (N-CPC), five M-CPCs of different reflector dimensions, namely, M-CPC2, M-CPC3, M-CPC4, M-CPC5 and M-CPC6, are constructed, and experimental results show that the concentrating performance of M-CPC is consistent with the numerical results of self-designed VC++ program. It is also found that the uniformity index of energy flux distribution for M-CPC is improved, and the effective operation time of concentrating solar beam radiation for M-CPC3 to M-CPC6 is increased by 1.82%, which indicates that M-CPC has better adaptability to weather changes. The average optical efficiency of M-CPC4 and M-CPC5 come up to 60.01% and 61.68%, respectively, and it has excellent performance of collecting solar radiation. In consequence, under the condition of the design method and N-CPC model, M-CPC4 and M-CPC5 are suitable choices in application, moreover, the cost of M-CPC reflector decreased significantly.

Optical characterization of a funnel solar cooker with azimuthal sun tracking through ray-tracing simulation

Funnel type solar cookers are simple and effective. Most of them rely on a multifaceted reflector to concentrate solar radiation on a cooking pot that is placed inside a transparent enclosure to create a greenhouse effect. The analysis of the resulting optical system is a complex task, as multiple reflections occur. The overall performance of funnel solar cookers is strongly affected by their optical efficiency. There is a lack of information in academic literature about this important research topic. This work aims to fill this gap presenting an optical performance analysis of a funnel solar cooker with only azimuthal sun tracking. Open-source numerical ray-tracing software Soltrace is used to investigate relevant characteristics such as the intercept factor, optical efficiency, dependency on incidence angle, performance of each reflecting surface and irradiation density flux distribution on different surfaces of the cooking pot. Some important results for beam radiation at normal incidence are the intercept factor, determined to be 0.664, and the optical efficiency with realistic optical properties, that turned out to be 0.370. When the incidence of solar beam radiation is not normal, optical efficiency remains above 90% of its normal incidence value, if the alignment errors are less than 10°.

Analysis of Solar Irradiance Variation on Heat Flux and Temperature Distribution for a Dish Concentrator Receiver

Abstract Concentrated solar power presents immense scope for the deployment of small-scale units focusing on diverse applications, including process heat and rural on/off-grid applications. This paper presents the analysis of solar irradiance variation on heat flux and temperature distribution at the dish concentrator receiver. A solar dish concentrator with a 2.8-m aperture diameter and a 0.4-m depth was used for this analysis. The solar ray intersection between a dish concentrator and its receiver, along with the heat flux distribution prediction, was carried out using SolTrace. The effect of flux intensity variation on temperature distribution at the receiver was investigated using comsol multiphysics. The optical analysis considered 10,000 rays, and 91.65% of them were observed to reach the surface of the receiver. For 1000 W/m2 of beam solar radiation, a peak heat flux and maximum temperature at the concentrator’s focal plane are found to be 32.4 MW/m2 and 923 K, respectively. The validation had been done using previously reported results in the literature to verify the correctness of the present simulation results. The effect of beam solar radiation variation on heat flux intensity and the temperature distribution revealed that both heat flux and temperature increase with increasing solar radiation, which points out the influence of design and operating conditions. Apart from PillBox and Gaussian distributions, the effect of slope and specularity errors was characterized, suggesting a greater sensitivity to the former than the latter.

The modified layer-by-layer weakening solar radiation models based on relative humidity and air quality index

Air pollution has a significant weakening effect on solar radiation. Therefore, it is important for the development and utilization of solar energy to establish a solar radiation model under the influence of fog and haze. Based on the analysis of existing layer-by-layer weakening solar radiation models, the discontinuous meteorological data provided by MODIS satellite are replaced by continuous measured data from meteorological stations. The beam solar radiation model and diffuse solar radiation model are modified by using relative humidity (φ) and air quality index (AQI). The results show that the correction effects of these modified models are better. The R value of beam solar radiation models have increased by 5.74%, the R value of diffuse solar radiation models have increased by 41.27%, and other statistical parameters (RSE, RMSE and NSE) have also been improved to a certain extent. The calculated value of the modified models is closer to the measured data. In addition, the order of correction parameters also has an effect on the results. The research shows that the best correction effect is to use relative humidity first and then AQI. According to this method, the layer-by-layer weakening solar radiation models can be more accurate and reliable.