Parabolic Concentrator Research Articles

Experimental Study of Electric Power Generation with Concentrated Solar Thermoelectric Generator

Although thermoelectric technology is little-known in the public domain, it presents an exciting alternative solution in many cases where lost heat energy can be quickly recovered to produce electricity. In the present paper, an attempt is undertaken to exploit this energy. For this purpose, an experimental study is conducted to produce electricity with the thermoelectric effect by utilizing a device placed on a parabolic concentrator. The device is placed on a solar tracker. The results obtained for two days of two distinct months, January and June, revealed that the production in June was higher than that in January by around 92.86%. This distinction is due to the concentrated solar beam being different on a day in each month. A vital product was recorded by utilizing the concentrator. This gadget permitted us to take advantage of the limit of sun-based radiation to produce power. The power may be stored with a legitimate stockpiling procedure.

A note of quantitative diagnosis of compound errors in trough concentration system

In practice, there are multiple optical errors existing in parabolic trough concentrator, which respectively have a unique effect on the flux distribution on the wall of the absorber, causing it to deviate from the ideal operating condition. Diagnosis for multiple errors is difficult. The effect of combined optical errors on the flux distribution can be modelled using convolution operations. In this study, the flux patterns under multiple types of optical errors are traversed and combined, and the actual flux distribution profiles of the parabolic trough concentrator measured by a camera-based method are compared to identify the Gaussian slope error, gravity deformation error and alignment error of the concentrator. This indicates that it is feasible to invert the flux profile on the absorber wall and diagnose the types and values of the corresponding optical errors of the concentrator.

Experimental investigation on a floating multi-effect solar still with rising seawater film

In this paper, a floating multi-effect solar still using parabolic concentrators to directly heat rising seawater film is investigated. The novel desalination device integrates solar still and two concentrators as a whole, which avoids the installation of a heat exchange pipeline and can float on the ocean to produce freshwater. The floating still consists of a front parabolic concentrator, a rear parabolic concentrator, and several embedded distillation cells. The distillation cell is composed of a hydrophilic wick, a condensing plate, and a narrow space in between. The parabolic concentrator greatly increases the solar heat to improve the temperature gradient and enhance the phase transition and diffusion process of water vapor. During desalination, the rising seawater film for evaporation is formed in the hydrophilic wick by capillary force. Through indoor steady-state experiments, some key parameters such as solar irradiance and incident angle on the temperature, water yield and gain output ratio (GOR) of the still were studied. Results indicate that the maximum temperature gradient in the 5-effect still can reach 48.5 °C. Under a 900 W/m2 irradiation, the water productivity and GOR are 2.7 kg/m2/h and 2.2, respectively. Additionally, outdoor experiments show that the daily freshwater reaches 4.7 kg/m2 with an average irradiation of 543 W/m2.

Experimental study on heat transfer of dense phase flow through a horizontal tube under constant wall flux conditions

A novel application of particles is utilization as dense phase flow for heat capture, transportation and storage. The use of horizontal dense phase flow as heat transfer fluid in solar systems is discussed with respect to current technologies. The investigation aims to analyze the heat transfer behavior of a horizontal dense phase flow under the condition of uniform surface heat flux. The proposed technologies transport particles as semi-continuous plug flow with a bottom layer, particles at the bottom layer will regularly renew once plugs pass by. Tests were conducted in a self-pilot scale-up platform. The measured wall-to-mixture heat transfer coefficient varies from ∼303 to 813 W/m2K in the particle mass flux range from 125 to 777 kg/m2s. Three heat transfer equations will be provided with the experimental data. A heat transfer equation describes the wall-to-mixture heat transfer coefficient linearly increases with particle mass flux. Then, a general empirical correlation in a dimensionless form predicted results well with experimental data of the present work and other data reported in the literature. Furthermore, a mechanistic heat transfer model is proposed according to a partial penetration mechanism and multi-layer flow model. The predicted results agree with experimental results within 12% of the average error. Considering the findings in this paper, researchers may have ideas to improve the heat transfer of horizontal dense phase flow to utilize this technology to the parabolic concentrator for the solar thermal industry.

Optical, thermal and thermo-mechanical model for a larger-aperture parabolic trough concentrator system consisting of a novel flat secondary reflector and an improved absorber tube

Using a larger-aperture parabolic trough concentrator can reduce cost and improve cycle efficiency. At present, the maximum output temperature of the typical parabolic trough concentrator systems is lower than the set 580 °C. Here a novel flat reflector was incorporated into the absorber tube to improve the intercept factor and optical efficiency and hence the overall performance. At the same time, the optimal diameter of the collector tube was also researched to meet the outlet temperature exceeding the set 580 °C and the absorber tube’s maximum temperature below 600 °C. A large-aperture parabolic trough concentrator (8 m aperture wide with 80° half rim-angle) is used as a case to demonstrate the effect of a flat reflector and advantages of the optimal absorber tube. Results obtained through simulations show that, in the large-aperture parabolic trough concentrator system with the flat reflector, the optimal diameter of the absorber tube was 70 mm for this design reaching 75% optical efficiency and 60.8% thermal efficiency at DNI = 1000 W/m2 and 53% daily average thermal efficiency for DNI = 400–1000 W/m2. Through adding a flat reflector, the optical efficiency and the uniformity were increased by 4–12% and 2–22% respectively, but the benefit gradually decreases with increasing the absorber tube diameter. To meet the requirement of outlet temperature more than 580 °C and absorber tube’s maximum temperature below 600 °C and reduce the thermal strain, a scheme of adjusting flow rate was incorporated.

Evaluation of the incidence of the geometry of the reflection area in the optical performance of a handmade prototype of a parabolic trough concentrator

Este artículo tiene como objeto evaluar la incidencia de la geometría del área de reflexión en el rendimiento óptico de un sistema a baja escala de concentrados cilindro-parabólico. El sistema fue desarrollado y probado para calentar agua o generar vapor de agua en las Unidades Tecnológicas de Santander, ubicadas en Bucaramanga, Colombia. Se tuvieron en cuenta factores ópticos del prototipo real para realizar un análisis de trazado de rayos de monte Carlo, aplicando la Herramienta SolTrace. El sistema de concentración real, fue sometido a una comparación con dos sistemas geométricamente diferentes, es decir, un concentrador con dimensiones inferiores al sistema real y uno con dimensiones mayores, con el fin de determinar los rendimientos ópticos y las relaciones de concentración, para determinar la relación existente entre estos dos parámetros y el rendimiento de la unidad. Los resultados obtenidos, mostraron que el área de reflexión afecta directamente el rendimiento óptico y la relación de concentración del dispositivo, evidenciando que, a mayor área de concentración, mayor rendimiento del equipo.

Performance enhancement of double pass photovoltaic/thermal solar collector using asymmetric compound parabolic concentrator (PV/T-ACPC) for façade application in different climates

Symmetrical compound parabolic concentrators (CPC) for a stationary double pass photovoltaic thermal (PV/T) air solar collector has been widely employed. However, for high yearly energy delivery, the solar incidence angle must be within the full acceptance angle of the CPC which is a challenge to determine for a symmetrical CPC. This paper presents the performance enhancement of a double pass photovoltaic/thermal air solar collector using an asymmetric compound parabolic concentrator (PV/T-ACPC) suitable for building façade application. Mathematical modelling was developed and validated against established experimental results. The potential of double pass PV/T-ACPC was then evaluated for different locations that represent low, mid, and high latitudes. Double pass PV/T-ACPC outperforms the conventional symmetric compound parabolic concentrator (PV/T-CPC) and the conventional flat type of double pass PV/T solar air collector. When compared with conventional flat type, the average percentage increase in the average daily total power yield for the PV/T-ACPC is as high as 14% and 50% for the low and mid-latitude, and high latitude countries, respectively. Meanwhile, for the PV/T CPC, the percentage of the average daily total power yield was slightly negative in value for low and mid-latitude countries, which indicates worse performance compared to the conventional type.

P‐74: Student Poster: High Efficiency μLED Light Engine for AR/VR Displays

By tailoring the radiation pattern through cavity effect, together with a compact compound parabolic concentrator, the light efficiency of μLED is increased by 1.9×. Such a high brightness μLED light engine helps to enhance the ambient contrast ratio for AR displays or to reduce the power consumption for VR headsets.

40 W Continuous Wave Ce:Nd:YAG Solar Laser through a Fused Silica Light Guide

The solar laser power scaling potential of a side-pumped Ce:Nd:YAG solar laser through a rectangular fused silica light guide was investigated by using a 2 m diameter parabolic concentrator. The laser head was formed by the light guide and a V-shaped pump cavity to efficiently couple and redistribute the concentrated solar radiation from the parabolic mirror to a 4 mm diameter, 35 mm length Ce(0.1 at.%):Nd(1.1 at.%):YAG laser rod. The rectangular light guide ensured a homogeneous distribution of the solar radiation along the laser rod, allowing it to withstand highly concentrated solar energy. With the full collection area of the parabolic mirror, the maximum continuous wave (cw) solar laser power of 40 W was measured. This, to the best of our knowledge, corresponds to the highest cw laser power obtained from a Ce:Nd:YAG medium pumped by solar radiation, representing an enhancement of two times over that of the previous side-pumped Ce:Nd:YAG solar laser and 1.19 times over the highest Cr:Nd:YAG solar laser power with a rectangular light-guide. This research proved that, with an appropriate pumping configuration, the Ce:Nd:YAG medium is very promising for scaling solar laser output power to a higher level.

Mathematical modelling, performance evaluation and exergy analysis of a hybrid photovoltaic/thermal-solar thermoelectric system integrated with compound parabolic concentrator and parabolic trough concentrator

This article discusses the electrical and thermal performance of a hybrid concentrator photovoltaic thermal and solar thermoelectric generator (CPV/T-STEG) system using a compound parabolic concentrator (CPC) and a parabolic trough concentrator (PTC). For the first time, the idea of merging imaging and non-imaging concentrators for a CPV and TEG hybrid system is examined, providing an option to retrofit or remodel existing PTC-based CSP systems. The thermal resistance concept is applied to establish a steady-state mathematical model of the proposed hybrid CPV/T-STEG system. A Newton-Raphson iterative approach is employed to solve the mathematical model and compute the temperature in every layer of the hybrid system. After validation, the mathematical model is employed to evaluate the overall performance of the hybrid system. The modelling results revealed that the electrical and thermal output of the developed hybrid system were higher by 2 and 1.6 times, respectively, when compared with the prior parabolic trough-based hybrid CPV/T-STEG system described in the literature. The effects of ambient temperature, wind speed, flow rate, number of TEGs, and solar concentration ratio on the electrical and thermal performance were investigated. The optimal number of TEGs required for maximum electrical performance under different solar concentration ratios is also obtained. Finally, the hybrid system’s exergy efficiency is investigated for various solar concentration ratios. The simulation results revealed that the increase in the Reynolds number from 100 to 2000 improves the net electrical and thermal efficiency by 10.21% and 5.7%, respectively. At a fixed solar concentration ratio (CCPC=4suns and WPTC=2WCPC), the electrical efficiency of TEG drops by 81.4%, but the thermal efficiency increases by 16.81%, provided that the number of TEGs is increased from 1 to 17. The highest exergy of the hybrid system is 8.36% when CCPC=2suns and WPTC=2WCPC. Due to the poor efficiency of commercial TEGs, the overall exergy efficiency of the hybrid system decreases with an increasing solar concentration ratio. In the proposed hybrid system, a fluid channel separates both the PV and TEG modules; hence the electrical conversion efficiencies of both modules are not closely related.

Experimental investigation of a developed tubular solar still with longitudinal wicked fins

Water scarcity and desertification is the real threat for many countries which is rapidly increasing. With the rapid development and increase of world population, solar water desalination is a suitable solution for future technologies. However, solar water desalination still needs a lot of research effort to reach an acceptable competing level with the conventional techniques. The present study investigated the effect of the vertical fins with wicks on the performance of the tubular solar still integrated with a parabolic concentrator solar tracking system. Real field experiments were conducted under the climatic conditions of Ha'il city, Saudi Arabia. Results showed relatively high freshwater yield and efficiency of 5.72 L/m2day and 45%, respectively, with a production cost of $0.0071/L. Adding fins to the device enhanced the heat transfer conditions by increasing the contact area between the solar collector and wick material which is wet by saline water. This strategy increased the device yield and efficiency by 44.8% and 41.1%, respectively, and reduced the production cost per liter by 40.7%. The developed device can be considered as a very competitive device with a relatively high yield and considerably low cost per liter of freshwater.

Development and thermal performance evaluation of solar parabolic dish based on fiber‐reinforced plastic

AbstractThis paper illustrates the design and fabrication of a 76° rim angle solar parabolic dish concentrator with low cost based on fiberglass‐reinforced for heating of heat transfer fluid using the hand layup process. Numerous advantages of fiberglass material include corrosion resistance, lightweight, design flexibility, quick installation time, and low cost makes it suitable for fabrication. The concave surface on which the reflective sheets are mounted is made to a high degree of perfection. The design process, as well as the complete fabrication process, are elaborately discussed in this article. The thermal efficiency of the newly constructed fiberglass‐reinforced solar parabolic dish concentrator was assessed by heating the heat transfer fluid in the conical cavity receiver, which was cycled from the sump via a gear pump and flexible stainless steel connecting pipes. The maximum value of heat transfer fluid temperature achieved was 194°C at the sump. The average thermal efficiency achieved for indoor heating at the sump was 17.42%, 17.16%, and 17.21%, respectively, during Experiments 1, 2, and 3. The results indicate that this system is acceptable for indoor cooking in the kitchen, as the system achieves temperatures between 150°C and 194°C.

Thermodynamic and optical analyses of a novel solar CPVT system based on parabolic trough concentrator and nanofluid spectral filter

This study presents the design and performance evaluation of a novel concentration photovoltaic/thermal (PV/thermal) system based on parabolic trough concentrator and indium tin oxide-ethylene glycol (ITOEG) nanofluid spectral filter. The overall design principle of the PV/thermal system is introduced, and the ITOEG nanofluid spectral filter is prepared and experimentally tested. For the full spectrum, the average transmittance and absorbance of the nanofluid spectral filter are 69.1% and 30.9%. The optical behaviour evaluation results reveal a double-peak radiation flux density distribution on the nanofluid channel bottom surface as well as on the solar cell module surface. When the north-south sun-tracking error increases to 0.2°, the optical efficiency of the PV/thermal system decreases to 93.7%. That means the system has a relatively good adaptability to the sun-tracking error. The thermodynamic analysis results reveal that the theoretical photoelectric conversion and solar thermal efficiencies of the PV/thermal system are 29.1% and 17.2%. The thermal efficiency of the PV/thermal system can be increased by increasing the nanofluid inlet flow velocity or by decreasing the nanofluid inlet temperature properly.

Performance Evaluation of Spiral Coil Receiver for Thermal Steam Generation Using Optical and Thermal Analysis of Parabolic Dish Concentrator

Solar energy has been advocated as the substitute for depleting fossil fuels for thermal applications and electricity generation. The research was aimed at determining the performance evaluation of the spiral coil receiver for thermal steam generation using a parabolic concentrating system. The parabolic dish solar concentrator (PDSC) with a rim angle of450C, the focal length of 6.15 m, and an aperture area of 5.8 m2 were designed and constructed for the determination of the variables. The PDSC and spiral coil receiver were made of stainless-steel reflector sheet and copper tube pipe respectively. Since the PDSC is for high enthalpy steam generation, it can be used for hot water and cooking applications. A finite element stress analysis was carried out to determine the thermal and optical efficiency of the system under various weather conditions. The thermal efficiency and optical analysis of the system were determined and obtained to be 54.4%, and 48.6% respectively. The efficiency according to the finding depends on the optical properties of the materials involved, the geometry of the collector, and the various imperfections arising from the construction of the collector.

A novel solution method for reflector shape of solar Compound Parabolic Concentrator and verification

In the existing studies, there are many methods to obtain the reflector shape equations of a CPC(Compound Parabolic Concentrator), but these methods are complicated and not unified. This paper aims to propose a novel method that is based on the edge-ray principle, the differential geometry theory, and the geometrical optical reflection law to get the reflector shape equations. Then, the reflector shape equations of an arc absorber CPC (A-CPC) which focuses light on the lower part of a circular absorber are calculated. The optical properties of such an A-CPC experimental model determined by these equations are studied via laser experiments. Afterward, the error between the calculated values obtained by MCRT(Monte Carlo Ray-Trace) method and experimental values are analyzed. The experimental results show that the optical properties of the A-CPC are in accordance with the theoretical expectations. They indicate also that the theoretical method is flexible and suitable for calculating a specific CPC reflector shape.

Optimization of concentration performance at focal plane considering mirror refraction in parabolic trough concentrator

ABSTRACT Parabolic trough solar thermal technology is the most cost-effective approach for concentrated solar energy applications. The concentrator thickness significantly affects the performance of the parabolic trough collector. To examine the effect of mirror refraction in the concentrator, the focal plane concentration for different concentrator thicknesses was studied using theoretical calculations, simulations, and experimental verification. A longitudinal offset of the focal plane is proposed to optimize the focal plane concentration. The deviation of the reflected sunlight depending on the concentrator thickness was found to strongly affect the concentration in the focal plane. When the concentrator thickness was increased by a factor of 5, the focal plane was 5 times as wide, the maximum energy flux density in the focal plane decreased by a factor of 5, and the optical efficiency decreased by 0.24%. The longitudinal offset of the absorber plane position was introduced to avoid local overheating of the absorber and low collector temperature by maintaining the focal plane width and maximum energy flux density in the focal plane within appropriate ranges. The experimental results showed that with optimization, the maximum energy flux density, uniformity, and optical efficiency increased by 5.75%, 3.35%, and 2.43%, respectively.

Design of a Low-Cost Parabolic Concentrator Solar Tracking System: Tubular Solar Still Application

Abstract The high cost of the solar tracking systems is the major obstacle facing the growth of the solar harvesting technology. Therefore, reducing the solar tracking cost is necessary for developing this important energy sector. This study developed a simple and low-cost solar tracking system for parabolic concentrator (PCST) assisting tubular solar still (TSS). A single-axis solar tracking mechanism is developed based on two small light-dependent resistors (LDRs) shielded by a blank sheet which keeps the two cells shielded from sunlight. When the sunlight moves, one of the two LDRs will gain some light activating a switch to turn on the driving motor moving the system in the opposite direction till the LDR shielded again. By this simple mechanism, the two LDRs are shielded from sunlight all the time and consequently, the solar collector is always facing the sunlight. A simple parametric study is also conducted for an efficient PCST-TSS device with higher freshwater productivity. The performance of the most promising five design categories is compared. Results showed that the lowest cost tracking system was 34.6% lower than the highest one. Moreover, the lowest CPL was $0.0074/L which is 43.1% lower than the highest CPL category. Moreover, a comparison with other studies showed high potential for the present significant reduction in the cost which ranges between 43.1% and 87% compared with the recent related studies. The developed device is fully self-reliance and suitable for rural and isolated communities having limited infrastructure.

A Detailed Review Investigating the Mathematical Modeling of Solar Stills

In recent years providing potable water for humans has become a major problem, especially in rural and remote regions. In the last few decades, methods of providing potable water using solar radiation have proved that there are methods without negative impacts. Solar is a solution and attractive alternative to still non-potable water without adverse consequences on ecosystems. Researchers have presented the results of their investigations in journals, using experimental, numerical, and analytical forms through the study of solar still performance in native climatic conditions. This paper undertakes an extensive review of recent modeling processes in solar stills and the thermal models proposed and derived for different types of solar stills and the modifications recommended to enhance efficiency and performance. During the selection of appropriate geometry and belonging components, this evaluation demonstrates that numerous designs and characteristics are useful in terms of productivity and efficiency. According to the reviewed results, the definition of concentration ratio is a fundamental concept for evaluating the evaporative heat transfer coefficient in relation to the convective heat transfer coefficient. Employing phase change materials, the results reveal that a large mass of PCM produces less solar still productivity, whereas increasing the PCM to water mass ratio from 10 to 100 reduces productivity by up to 30%. Using a parabolic concentrator, results show that productivity can be increased by 56 and 38.5% in the winter and summer, respectively.

Techno-enviro-exergo-economic and water hygiene assessment of non-cover box solar still employing parabolic dish concentrator and thermoelectric peltier effect

This study was conducted to design a parabolic dish concentrator box solar still without a glass cover combined with a thermoelectric condensing duct. The parabolic set reflects the sun's rays beneath the basin and the vapor generated in the basin is sucked by a fan with variable volume flow rate into the condensing duct, which is surrounded by four thermoelectrics cooling modules. The performance of non-cover box solar still with thermoelectric is reported based on the component temperature, distilled water production, energy, exergy, energy payback period, energy production factor, economic, exergoeconomic, environmental, enviroeconomic, exergoenvironmental, exergoenviroeconomic, and water hygiene assessment. In the optimal case, in which the fan sucks the vapor at a volume rate of 300 L/min, the average winter daily cumulative distilled water, energy efficiency, and exergy efficiency were enhanced by 25.6%, 4.88%, and 1.06%, respectively, compared to the case, which the fan is off. The cost of distilled water production and the payback period in the optimal case are 0.0056 $/L/m2 and 114 days, respectively. Also, the techno-enviro-exergo-economic findings revealed that the parabolic dish concentrator box solar still with thermoelectric in terms of enviroeconomic and exergoenviroeconomic can create a financial reserve of $320.02 and $50.32, respectively. The distilled water produced by the desalination system is safe in terms of hygiene and drinking ability.

2E (energy and exergy) analysis of solar evacuated tube-compound parabolic concentrator with different configurations of thermal energy storage system.

The intermittent nature of solar radiation requires a thermal energy storage (TES) system for reducing the mismatch between energy demand and supply. Solar water heating (SWH) systems can help save up to 90% of the utilized energy for water heating. In this study, a compound parabolic concentrator (CPC) solar collector has been coupled to three different configurations of TES system. A comprehensive analysis on the effects of PCMs arrangements in TES systems viz three PCMs (case 1) and five PCMs (case 2) on the energy efficiency, exergy efficiency, and overall loss coefficient of the solar collector and TES system has been made and compared with sensible TES system. An experimental data showed an augmented energy storage of 12% and 41% in "case 1" and "case 2" over sensible TES system as a result of reduction in heat losses with the cascaded arrangement of PCMs. The collector paired with case 2 configuration clearly exhibited a higher exergy efficiency due to supply of heat transfer fluid at relatively lower temperature while compared to other TES configurations. The outcomes of this study reveal the key role of cascaded arrangement of PCMs for enhancing energy and exergy efficiencies of solar collector.