Linear Fresnel Reflector Concentrator Research Articles

Heat-collecting performance of linear Fresnel reflector concentrator measuring and forecasting after dust accumulation

To quantitatively analyze the influence of dust on the linear Fresnel reflector in different seasons on the thermal performance of the system. In this paper, a two-year outdoor dust accumulation test was carried out, and a quasi-dynamic test method considering dust accumulation factors was adopted to study and predict the influence of dust on the thermal performance of linear Fresnel reflector concentrating system. The results show that for every 1 g/m2 increase in dust density, the relative reflectivity decreases by 4.11 %, and the thermal efficiency decreases 6.96 %. The model prediction shows that when the dust density is 5 g/m2 and the solar radiation is 750 w/m2, the thermal power of the system will decrease by 52.90 % in winter, 26.98 % in summer and 35.30 % in spring and autumn. Therefore, to ensure the efficient operation and economy of the system, in the case of no rain, the dust removal period of the mirror in spring and autumn is 20 days, in summer and winter is 30 days and 10 days respectively.

A spectral splitting CPV/T hybrid system based on wave-selecting filter coated compound parabolic concentrator and linear Fresnel reflector concentrator

Efficient full-spectrum solar energy utilization shows great potential to improve solar energy conversion efficiency. In this paper, a spectral splitting concentrated photovoltaic/thermal hybrid system based on a wave-selecting filter-coated compound parabolic concentrator and linear Fresnel reflector mirror field is developed. Optical models to simulate the linear Fresnel reflector have been developed and validated. With the wave-selecting filter coated compound parabolic concentrator, the visible and near infrared spectra transmit onto the photovoltaic cells, while the rest are reflected to the receiver tube. Furthermore, a simplified receiver indoor test prototype is designed to investigate the characteristic of solar photovoltaic module with the spectral filter in the context of the compound parabolic concentrator. The measured I–V curves are compared with the modeled results. Additionally, the thermodynamic performance of the system is analyzed. Parametric studies are performed to investigate the effect of key design parameters including the mirror width, focal length and the radius of the receiver tube on the solar flux density and the exergy efficiency. An exergy efficiency of 35.51% and an optical efficiency of 94.78% are achieved. With a preliminary techno-economic analysis, the levelized cost of the electricity of the system is $0.209/kWh with a payback period of 10 years.

Comparative Analysis of Thermodynamic Performances of a Linear Fresnel Reflector Photovoltaic/Thermal System Using Ag/Water and Ag-CoSO4/Water Nano-Fluid Spectrum Filters

Renewable energy represented by solar energy has played an important role in the transformation of the energy consumption structure of the world. This study describes and studies a hybrid photovoltaic/thermal (HPVT) system using a linear Fresnel reflector concentrator (LFRC) and nano-fluid spectrum filter (NFSF). The method of designing the HPVT system is provided. Ag/water and Ag-CoSO4/water NFSFs used for this HPVT system were prepared and experimentally tested. Optical analysing results indicate that the optical efficiencies of the PV cell module (PVCM) and NFSF are 0.7556 and 0.9053 under the condition of 0.3° solar tracking error (STE), demonstrating good adaptable capacity to the STE. Moreover, the operating performances of the HPVT system using different NFSFs are compared. The comparison results demonstrate that compared with the Ag/water NFSF, the introduction of CoSO4 can enhance the thermal performance but decrease the photovoltaic efficiency of the HPVT system. When the Ag-CoSO4/water (1.2 mg–3 g/130 mL) NFSF is used, the photovoltaic and thermal efficiencies of the whole HPVT system are 0.1366 and 0.4259, and the overall exergy efficiency is 0.209. The exergy efficiency of the HPVT system will be improved if the NFSF temperature is increased appropriately or if the external convection heat transfer coefficient and environment temperature are reduced.

Solar Flux Measuring and Optical Efficiency Forecasting of the Linear Fresnel Reflector Concentrator after Dust Accumulation

Solar Flux Measuring and Optical Efficiency Forecasting of the Linear Fresnel Reflector Concentrator after Dust Accumulation

Novel design and analysis of a solar PVT system using LFR concentrator and nano-fluids optical filter

The current study proposes a novel solar PV and thermal (PVT) system based on the combination of linear Fresnel reflector (LFR) concentrator and ITO-EG nano-fluids optical filter. Preparation and relevant measurements of the ITO nano-particles as well as the ITO-EG nano-fluids are conducted. The test results reveal that the optical filter has an average absorptivity of 30.9% in the spectrum range of 250.0–2500.0 nm. The solar concentration behaviour of the PVT system is revealed and the sensitivity analysis results of sun tracking error indicate that when the north-south tracking error is 0.2°, the overall optical efficiency is 90.12%, which means the PVT system has a relatively good adaptive faculty on sun tracking error. Theoretical thermodynamic calculation and CFD simulation methods are utilized to estimate the operation behaviour of the PVT system. The results demonstrate that the PVT system has a photoelectric conversion efficiency of 29.6% as well as a thermal efficiency of 18.52%. Parametric analysis results show that the thermal efficiency of the PVT system can be improved by increasing the inlet nano-fluids flow velocity as well as the ambient temperature, or by reducing the inlet nano-fluids temperature or convection heat transfer coefficient.

Study on the annual optical comprehensive performance of linear Fresnel reflector concentrators with an effective multi-objective optimization model

In this paper, a more general multi-objective optimization model is developed to efficiently investigate the annual optical comprehensive performance of the entire linear Fresnel reflector concentrator (LFRC). It was carried out by combining the multi-objective genetic algorithm (MOGA) and the Monte Carlo ray-tracing (MCRT) method, with an effective objective function verified to efficiently characterize the annual solar flux non-uniformity of LFRCs, named as the nominal annual solar flux non-uniformity. With this indicator, trade-off studies can be realized for considering the common conflicting relationship between the optical efficiency and the solar flux non-uniformity on annual time scale. It was validated and proved to make the costly infeasible LFRC MOGA-MCRT optimization feasible, which significantly reduces the computing time of the originally time-consuming optimization almost two orders of magnitude. After validation, this optimization model was successfully applied to optimize LFRCs of different mirror shapes and tracking modes at different latitudes. The recommended geometrical parameters combination was obtained from each Pareto front, by using a method called Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS). Through continuously expanding the application scope and reusing TOPSIS, better parameters combination was further recommended. For the most recommended parameters combination studied in this paper, the nominal annual solar flux non-uniformity decreased by 38.04% while the nominal annual optical efficiency increased by 133.60%, as compared with the original LFRC baseline system. This time-reducing optimization model is thus proved to be effective, which could also provide guidance for the optical optimization of other similar solar thermal applications.

A spectrally splitting concentrating PV/T system using combined absorption optical filter and linear Fresnel reflector concentrator

A novel spectral splitting concentrating PV/T system (CPV) based on a combined absorption optical filter and a linear Fresnel reflector concentrator is developed. The combined absorption optical filter includes a selective absorbing liquid and a solid absorption filter, acting as a band pass filter for silicon concentrator solar cells. The optical performance of both the concentrator and the hybrid receiver under different conditions is investigated through ray tracing software-LightTools. The results show that the concentrated illumination distribution within the PV module width at the focal region of the concentrator is quite uniform and 72.15% of the spectral power in the spectral band 650–1075 nm incidents the PV module using light filtering by propylene glycol (PG) and HB650. Furthermore, an indoor test of a simplified receiver is conducted to verify the effectiveness of the combined absorption filter and an energy conversion performance of the proposed spectral splitting CPV/T system is evaluated. The use of PG and HB650 combined filter produces a higher total efficiency of 46.77% and yields economic value enhancement of 54% compared to the PV only system.

Experimental and optical performances of a solar CPV device using a linear Fresnel reflector concentrator

A solar CPV device using a linear Fresnel reflector (LFR) concentrator is described. The design principle of the concentrator is provided. The solar concentrating processes are simulated by using the MCRT approach. A small scale test rig of the concentrator is constructed to investigate the actual optical and I–V performances of the CPV device. Both of the simulation and experimental results reveal that the proposed concentrator has a relatively high solar concentrating uniformity. The configuration and optical analyses of the concentrator are launched. The results show that the geometric concentrating ratio and ground utilization ratio both increase with the solar panel installing height increased. When the solar cell height is settled, the maximum value of ground utilization ratio exists with the mirror field width increased. The sun-tracking accuracy effect analysis is also carried out. The results indicate that the normalized optical efficiency of the CPV system using the LFR concentrator can be 0.62 or higher when the tracking error is less than 1°. A solar cell monomer and a cell module are used to carry out the I–V experiments. The test results of their energy conversion efficiencies are 14.7% and 13.6%, respectively.

Performance evaluation of a direct vapor generation supercritical ORC system driven by linear Fresnel reflector solar concentrator

For the purpose of getting higher system efficiency at high temperature and avoiding the complex two-phase problem, the performance of a direct vapor generation (DVG) supercritical organic Rankine cycle (SORC) system driven by linear Fresnel reflector (LFR) concentrator was evaluated in the paper. The detailed procedure for modeling the LFR concentrator and SORC process through the EES environment was presented. The method to select suitable supercritical organic working fluids for middle–high temperature (150 °C–350 °C) was also indicated. The results showed that coupling the supercritical and DVG technology not only decreases the irreversibility at evaporator, it also reduces the heat loss and cost of system and allows obtaining higher overall efficiency. With the increasing of inlet temperature before turbine, the overall efficiency increases. In addition, the results demonstrated that supercritical cycle can be seen as a way to increase the maximum operating temperature. The results of the present work implied that cyclohexane is the best choice of organic working fluid for SORC system with an overall efficiency of 19.65%.

Thermodynamic and optical analysis for a CPV/T hybrid system with beam splitter and fully tracked linear Fresnel reflector concentrator utilizing sloped panels

Spectral splitting technology that separates solar spectrum into several parts and enables different energy conversions such as photovoltaic (PV) conversion and photo-thermal conversion aims to utilize the full spectrum solar energy efficiently. A novel concentrating PV/Thermal (CPV/T) hybrid system with beam splitter and fully tracked linear Fresnel reflector concentrator utilizing sloped panels was proposed in this study. The relations between the structural parameters and the optical performances of the system were investigated. The concentrated radiation distribution on the PV device surface was simulated by taking into account the main optical errors and shows a good uniformity. Based on the experimental data of the components, thermodynamic analysis on the CPV/T hybrid system was carried out and the results reveal that the overall energy conversion efficiencies of the proposed CPV/T hybrid system is higher than that of the CPV system under the same conditions.

Design and thermal performances of Semi-Parabolic Linear Fresnel Reflector solar concentration collector

A Semi-Parabolic Linear Fresnel Reflector (SPLFR) solar concentrator is proposed in this paper. The SPLFR is formed by linear plate mirrors whose edges located at a parabolic line. The ray trace simulation results show the SPLFR has the same concentrating efficiency as that of the parabolic trough concentrator (PTC), but lower manufacture cost. The SPLFR concentrator has higher ground utilization ratio compared with that of Linear Fresnel Reflector (LFR) concentrator because it has no shading and blocking shortcomings. The SPLFR concentrated radiation distribution along the circumference of absorber pipe cross section is investigated and compared with that of LFR concentrator. The thermal performance of linear evacuated absorber for the SPLFR is simulated numerically as well. The nonuniform radiation distribution induces two convection eddies at each side of absorber pipe which enhances the heat transfer from the wall of absorber to the working fluid.

Thermal Performance Prediction of a Trapezoidal Cavity Absorber for a Linear Fresnel Reflector

A trapezoidal cavity absorber for a linear Fresnel reflector concentrator is analyzed and optimized via CFD simulation. The heat loss coefficient is introduced; the influences of ambient temperature, absorber temperature, cavity depth, inclination of side walls, insulation thickness, glass window, and emissivity of selective absorption coating have been studied. The results show that radiation dominates the cavity heat loss, and heat loss through the glass window is higher than through the insulation layer; among these factors, impact of emissivity of selective absorption coating and insulation layer is greater than that of the other factors. The simulation results via CFD prove that cavity with a 100 mm depth shows the best thermal performance among the parameters that have been taken into account.

Numerical simulation of a Linear Fresnel Reflector Concentrator used as direct generator in a Solar-GAX cycle

Abstract In this work a methodological analysis to design and evaluate the technical feasibility of use a Linear Fresnel Reflector Concentrator (LFRC) as generator in an advanced absorption refrigeration system (Solar-GAX cycle) has been carried out. For this purpose, a detailed one-dimensional numerical simulation of the thermal and fluid-dynamic behavior of a LFRC that solves, in a segregated manner, four subroutines: (a) fluid flow inside the receptor tube, (b) heat transfer in the receptor tube wall, (c) heat transfer in cover tube wall, and (d) solar thermal analysis in the solar concentrator has been developed. The LFRC numerical model has been validated with experimental data obtained from the technical literature; after that, a parametric study for different configurations of design has been carried out in order to obtain the highest solar concentration with the lowest thermal losses, keeping in mind both specific weather conditions and construction restrictions. The numerical result obtained demonstrates that using a LFRC as a direct generator in a Solar-GAX cycle satisfy not only the quantity and quality of the energy demanded by the advanced cooling system, it also allows to obtain higher global efficiencies of the system due to it can be operated in conditions where the maximum performance of the Solar-GAX cycle is obtained without affecting in any significant way the solar collector efficiency.

A fresnel strip reflector-concentrator for tubular solar-energy collectors

A linear Fresnel reflector-concentrator employing commercial flat, front-reflecting mirror strips (of reflectivity ϱ = 0·6), arranged in a planar configuration, has been fabricated and analyzed. An average concentration ratio of about 18 has been obtained for two-thirds of the periphery of a tubular receiver of 0·025 m diameter. Working in conjunction with a partially evacuated (10 −2 Torr) cylindrical collector employing a selective cobalt oxide coating (with α = 0·88, ε 250°C = 0·25 and stable up to 600°C), a stagnation temperature of ∼ 385°C has been obtained, corresponding to a direct solar flux of ∼ 600 W/m 2.