Fresnel Collector Research Articles

Neurofuzzy Defocusing strategy for a Fresnel collector

Concentrating Solar Power systems are widely applied as a means to utilize the sun's abundant renewable energy, but the design of these processes facilitates the occurrence of overheating. This work presents two approaches for calculating the mirror angles of a fresnel collector in order to limit the amount of solar energy collected. The proposed structures are designed to receive a desired focus value from a controller and generate references for the mirror inclination controllers of the collector. The first strategy consists of the use of an optimization problem coupled with a simplified model of the collector. Whereas, the second approach consists of an ANFIS network that is trained with data from a reliable collector model made in SolTrace®. Both approaches are compared with simulations in SolTrace® the results show that the ANFIS solution presented overall better results, taking into account error and computational time.

A Review of Linear Fresnel Collector Receivers used in Solar Thermal Technology

Linear Fresnel collectors (LFC) have, among the four technologies of concentrating solar power (CSP), the simpler technology. They have a one axis sun tracking, plane mirrors and a fix receiver. All these elements make them the most suitable for small scales CSP plants adapted to rural area of the Sub-Saharan region. The receiver is an important part of the LFC. There is a wide variety of receivers that differ in the shape of the absorber: mono-tube, multi-tube, plane. The shape of the secondary concentrator or its absence allows to categorize the receivers in a butterfly, compound parabolic concentrator, segmented parabolic secondary concentrator or trapezoidal receiver. Vacuum mono-tube receivers have heat losses between 200 W/m and 270 W/m at an absorber temperature of 350°C. A mono tube receiver at partial vacuum losses more than 350 W/m at 350°C. The lowest heat losses of a multi-tube receiver with a trapezoidal secondary concentrator can reach 500 W/m at an absorber temperature of 350°C. This paper discusses a comparative study of existing receiver designs in order to find the most suitable for rural areas in the sub-Saharan region, i.e. easy to design by hand and low cost. Although they do not have the best thermal performance, trapezoidal receivers with a black-painted copper multi-tube absorber and a glass cover seem to be the most suitable.

Measuring Concentrated Solar Radiation Flux in a Linear Fresnel-Type Solar Collector

Linear Fresnel solar collectors are a promising and emerging solution to contribute to renewable heat supply in industrial processes with thermal energy demand in the medium temperature range (<250 °C). An innovative linear Fresnel collector (LFC) prototype has been designed, patented, and built at the Plataforma Solar de Almería (PSA), Spain. This work presents the applied methodology, experimental device, and results obtained in the measurement of the flux density of concentrated solar radiation in the focal plane of the solar collector. The experimental results confirm that an average flux density of (9.8 ± 0.6) kW/m2 was obtained with a direct normal solar irradiance of (870 ± 10) W/m2 in tests performed in May 2002, which is a result similar to that obtained in optical simulations of the system.

Experimental and techno-economic analysis of two innovative solar thermal receiver designs for a point focus solar Fresnel collector

In this paper, techno-economic analysis and the experimental campaign for a new solar concentrating system are presented. Two novel receivers (Jet impingement receiver with mesh structure & helical channel receiver) are tested on a novel collector technology. The collector technology integrates the two established models of solar concentrating technologies, which are linear Fresnel reflector technology and central receiver technology, into the new concept called the Point Focus Fresnel Collector (PFFC). It is found that the PFFC system with jet impingement receiver and mesh structure provides higher thermal efficiency and manufacturing ease compared to parabolic dish systems. Maximum thermal efficiency of jet impingement receiver is highest at 87% whereas that for helical channel receiver is 83%. Average thermal efficiency of jet impingement receiver is 61% whereas that for helical channel receiver is 58%. Economic analysis of the system reveals that the discounted payback time for the PFFC system is only 5.5 years and less than one year compared to diesel and electricity powered steam generators respectively at an inflation rate of 2.5%. Substantial saving is predicted with PFFC system compared to diesel and electricity powered steam generator. For all discount rates in the range of 2.5–25%, the levelized cost of energy (LCOE) for PFFC system is much lower than that of LCOE in Saudi Arabia for conventional system. Since the LCOE in most of the Middle East and North Africa (MENA) countries is higher than the LCOE in Saudi Arabia, therefore, the PFFC system is also suitable for other MENA countries where average direct normal irradiation values are comparable to Saudi Arabia.

Thermal Performance Analysis of a Linear Fresnel Concentrating Solar Collector Absorber Tube

Linear Fresnel solar collectors are suitable for a wide range of applications, which include steam generation for power generation, industrial process heat, solar cooling, institutional and domestic hot water production etc. The thermal performance of a linear Fresnel solar collector absorber tube was investigated in this study for different fluid mass flow rates, heat flux intensities, heat transfer fluid inlet temperatures, ambient air temperatures and external loss heat transfer rate. Turbulent flow liquid water heat transfer fluid and uniform circumferential heat flux distribution boundary were considered under steady-state conditions. The fluid flow was considered incompressible. This study was limited to a first order model approximation for thermal performance of a linear Fresnel solar collector absorber tube. The heat transfer fluid and absorber tube material properties were considered constant and independent of temperature. The results indicated that the absorber tube outlet heat transfer fluid temperature decreased with an increase in the Reynolds number and increased with the heat flux intensities. Thermal efficiency increased with an increase in the heat transfer fluid mass flow rate and however, decreased with increase in pressure drop and the consequent pumping power requirement. It was also found that the thermal efficiency of the collector decreased with an increase in the fluid bulk inlet temperature and decreased with an increase in the external loss heat transfer rate.

Optical performance comparison of two receiver configurations for medium temperature Linear Fresnel Collectors

Linear Fresnel collectors are good candidates to lower the use of fossil fuels in the built environment and in the industry, due to their compact nature and adaptability. In addition, the technology shows large margins for improvement, in terms of efficiency capital and operational expenditures. The present study presents a new atmospheric double tube absorber, which fully explores non-imaging optics design. An existing LFR system with a second stage concentrator consisting of an evacuated tube with an associated secondary parabolic reflector, is compared with a novel model adopting the same LFR primary field but a new second stage concentrator, which achieves a much wider acceptance angle. It is shown that, beyond a better performance, the novel proposed solution provides simpler maintenance, as in cleaning and parts’ replacement, and a reduced cost, as it includes cheaper standard components. The study was conducted in ray-tracing environment with the Tonatiuh++ software, which is able to directly implement non-imaging optics configurations via analytic equations. The present study is centred on the optical performance of the collector. The quantitative comparison demonstrates that the annual yield of the novel model is increased at least by 8.3% while the cost per metre of the receiver is decreased by 45%.

Impacts of biomass hybridization on exergetic sustainability of a solar organic Rankine cycle power plant

Due to the low thermo-economic performance of solar ORC plants, several studies are ongoing to investigate the potential merits/demerits of biomass hybridization as a retrofit. Although many of such studies have examined the technical and economic viabilities of various hybrid solar-biomass concepts, due attention has not been directed to the area of their sustainability based on the Second Law of Thermodynamics. This study was aimed at investigating the potential effects of biomass hybridization on the exergetic sustainability of an organic Rankine cycle (ORC) power plant. Design data of an existing solar ORC plant currently operational at Ottana (Italy) were employed for analysis. The referenced ORC plant is rated at about 630 kWe, powered at the moment solely by a concentrated solar power (CSP) field, which integrates linear Fresnel collectors with two-tank thermal energy storage (TES) device. Five different exergetic sustainability indicators were employed in this study to assess the aforementioned ORC plant when fed by hybrid solar-biomass energy resources. Results showed the hybrid plant's destruction factor (DF), exergetic sustainability index (ESI), environmental effect factor (EEF), improvement potential rate (IPR), and recoverability ratio (RECR) of 89.40%, 0.119, 8.435, 4744.8 kW, and 0.89, respectively. Additionally, a comparison of the solar-only and the hybrid solar-biomass schemes revealed that biomass hybridization would improve the exergetic sustainability of the ORC plant. Nevertheless, the high value of IPR obtained suggests that ample opportunities would yet exist to further enhance sustainability indices of the studied ORC plant post biomass hybridization. In sum, biomass hybridization of the solar ORC plant considered in this study would enhance sustainability performance but more opportunities would yet exist to further optimize the system.

Control Strategies Applied to a Heat Transfer Loop of a Linear Fresnel Collector

The modelling of Linear Fresnel Collectors (LFCs) is crucial in order to predict accurate performance for annual yields and to define proper commands to design the suitable controller. The ISO 9806 modelling, applied to thermal collectors, presents some gaps especially with concentration collectors including LFCs notably due to the factorisation of the incidence angle modifiers and the fact that they are considered symmetric around the south meridian. The present work details the use of two alternative modellings methodologies based on recorded experimental data on the solar system installed at the Cyprus Institute, in the outskirts of Nicosia, Cyprus. The first modelling is the RealTrackEff, which is an improved ISO9806 modelling, and the second is constructed using the CARNOT blockset in MATLAB/Simulink. Both models include all the elements of the heat transfer fluid loop, i.e., mineral oil, with a tank and a heat-exchanger. First, the open loop’s studies demonstrated that the root mean square on temperature is 1 °C with the RealTrackEff; 2.9 °C with the CARNOT and 6.3 °C with the ISO9806 in comparison to the experimental data. Then, a PID control is applied on the experimental values in order to estimate the impact on the outlet temperature on the absorber and on power generation. Results showed that the error on the estimation of the heat absorbed reaches 32%.

Comparative Study on Heat Flux and Temperature Distribution Performance of Linear Fresnel Collector Based on Uniformity Index

Comparative Study on Heat Flux and Temperature Distribution Performance of Linear Fresnel Collector Based on Uniformity Index

Split-range control for improved operation of solar absorption cooling plants

This paper proposes the first application of a split-range control technique on a concentrating solar collector to improve an absorption plant production. Solar absorption plants have solar power availability in phase with cooling demand under design conditions. Thus, it is a powerful cooling technology in the context of renewable energy and energy efficiency. These plants need control systems to cope with solar irradiance intermittency, reject irradiation disturbances, manage fossil fuels backup systems and dump closed-loop thermal-hydraulic oscillations. In this work, control techniques are proposed and simulated in an absorption plant in Spain. The plant consists of a concentrating Fresnel solar collector connected to an absorption chiller. The objectives are to operate with 100% renewable solar energy and avoid safety defocus events while reducing temperature oscillations and control actuators effort. Firstly, the current available plant controllers are defined, then two modifications are proposed. The first modification is a split-range controller capable of manipulating both flow and defocus of the Fresnel collector, the second modification is a PI controller to substitute the original chiller on-off controller. The results compare, through validated models, the different control systems and indicate that using both proposed controllers reduces 94% of the sum of actuators effort and 43% of the integral of absolute set-point tracking error compared to the plant's factory pre-set controllers. The suggested controllers increase 66% of energy production and 63% of exergy production. Besides, the split-range technique can be extended to any concentrating solar collector control.

Comparative evaluation of Integrated Solar combined cycle plant with cascade thermal storage system for different heat transfer fluids

The existing conventional combined cycle power plant(s) are generally not getting the schedules for supply of power because of the high price of Natural Gas and are forced to remain idle or to run on part load. On the other side, the focus is on the capacity addition of power generation units based on the alternate sources mainly solar to counter the ill effects on environment through fossils fuel-based plant(s). In such a scenario, the combined cycle power plant(s) with its integration with solar (ISCC) can pave the way forward to provide an optimal solution to tap most of the power generation through solar power and to ensure grid stability through utilising the installed combined cycle power plant(s) at part or full load. It will be a win-win situation for solar plants as well as combined cycle power plants. This study presents an integration of Linear Fresnel collector solar system and latent heat cascade storage system with a 328.10 MW combined cycle power plant of north India for operating it as integrated solar combined cycle (ISCC). The present work discusses the configurations of integration of solar power generation cycle with the combined cycle power generation and presents the analysis of the performance of these integration configurations including the operation of gas turbine(s) at full load or part load. A MATLAB code is used for simulation to analyse the performance of ISCC by varying direct normal irradiation at different part-load condition of gas turbine with different heat transfer fluids such as water and molten salt, then also compare the performance of latent heat cascade thermal storage system with oil & molten salt as HTF. The effect of cascade thermal storage has also been analysed on the plant performance. The efficiency of ISCC with molten salt as HTF is 50.87% which is more than with water as HTF by 1.51%. The present study also brings out the saving of the fuel to figure out the financial benefit. However, the financial model has not been developed in the present work due to the dynamics of the price of natural gas internationally. The study also presents the analysis of the enhanced fuel-saving ratio and reduced emissions.

Thermal performance assessment of the world’s first solar thermal Fresnel lens collector field

Fresnel lenses are used in a wide range of solar energy applications, primarily due to their reduced material usage, low cost, and high optical efficiency. This study presents an investigation of the world’s first full-scale Fresnel lens solar collector field. The collector field consists of 144 two-axis tracking solar collectors manufactured by the Danish company Heliac and supplies heat to the local district heating network in Lendemarke, Denmark. The thermal performance of the solar collector field was determined using the quasi-dynamic test method. It was found that the peak efficiency was 11% lower compared to a brand-new collector and that heat losses from the collectors made up half of the total heat losses of the solar field. The reduction in the peak efficiency was primarily caused by soiling as the collectors were exposed to outdoor conditions for one year without cleaning. Furthermore, the system’s annual performance was determined using a simulation model developed in TRNSYS and validated by comparison to measurement data. For 2020, the heat generation was 373 kWh/m2 (relative to aperture area) when operating with an outlet temperature of 90 °C and inlet temperature of 50 °C. Additionally, a sensitivity analysis of the annual heat generation was performed, varying the ground cover ratio, mean collector temperature, and soiling level. The sensitivity analysis showed that the heat generation was relatively insensitive to changes in the mean collector temperature, demonstrating that the collectors are suitable for generating heat above 100 °C, unlike flat-plate collectors.

A new design of multi-tube receiver for Fresnel technology to increase the thermal performance

• This work presents a thermal design guideline for multi-tube Fresnel receivers. • The fluid flow layout in multi-tube Fresnel receivers fits to the symmetry of the solar image at noon. • The fluid circulates from the lower to the higher flux density zone in the absorber of the multitube. • The fluid velocity is modified by changing the tube diameter, to optimize heat transfer in multitube. • Optimization of the tube diameters is accomplished by exergy efficiency calculation. Solar heat for industrial processes is a promising way to meet the high thermal demand required by the industry, while this application becomes an important niche market for solar technology. In this research line, it is proposed a novelty concept based on a rotary Fresnel solar collector to supply heat above 150 °C. This work is focused on the multi-tube receiver for this Fresnel collector, proposing a thermal design based on three criteria that can be generalized for any multi-tube receiver: the fluid flow layout is arranged to meet the symmetry of the solar flux map; the fluid circulates from the lower to the higher flux density zone; and the fluid velocity is modified by modifying the tube diameter, to optimize the heat transfer. Following these criteria, the final configuration of the receiver is chosen based on an exergy optimization, in which both heat loss and pressure drop must be quantified. It has been also accomplished a generalization of the optimization methodology for Fresnel collectors providing heat at different temperatures, showing that, in these cases, the configuration that maximizes the exergy efficiency does not correspond to the one with the highest energy efficiency. This thermal design method can be applied to multi-tube receivers working at higher temperatures in longer Fresnel loops, in which case the optimization will result in more marked differences between the optimal values and the standard ones.

Simplified optical model, aiming strategy and partial defocusing strategy for solar Fresnel collectors

This paper presents the development of a simplified analytical optical model, an analysis of aiming strategies and a defocusing strategy for a Fresnel solar collector. The model aims to represent the main components of solar concentration on a Fresnel collector when considering independent rotation on each mirror in order compute the solar radiance flux on the absorber. The model is validated with data from a reference Ray-Tracing software and from experimental data. The model is then used to evaluate three aiming proposals with regards to solar radiance flux over the absorber. Data from the optical model and mirror inclinations proposed by the aiming strategies are used to implement a partial defocusing strategy for Fresnel collectors. The main purpose of this analysis is to assess the possible gains that individual manipulation of each collector mirror can bring to the process. It is shown that all the analyzed aiming methods present similar performances regrading the optical efficiency aspect. Thus, the use of the simplest solar aiming method presents itself as a very effective solution. Results also show the possibility to implement partial defocusing on Fresnel collectors, allowing the use of focus as a manipulated variable for control.

Fault Detection and Isolation Based on Deep Learning for a Fresnel Collector Field

With the advancement of new technologies, power systems are increasingly equipped with more sensors and actuators, heightening the risk of failure. This fact, together with the vulnerability of solar plants -not only to internal faults but also to the action of the sun, rain, wind, and animals, among others- gives rise to the need for detecting and identifying faults to deal with them. Methods that detect and diagnose faults play a crucial role in solar plants, allowing the systems to cope with them as soon as they occur and before they lead to large-scale problems. This work proposes using neural networks to detect and distinguish mirror and flow rate faults in a Fresnel plant. In addition, a defocusing stage is added to access hard-to-isolate faults, increasing the accuracy of 89.61% to 97.43%. These results contribute to the problem of isolability in thermal solar plants. The simulations for obtaining the neural networks and the results were conducted on a model of the Fresnel plant located at the Engineering School of Seville, Spain (ETSI).

Analysis of Light Concentration Error and Compensation Algorithm of Linear Fresnel Collector

Analysis of Light Concentration Error and Compensation Algorithm of Linear Fresnel Collector

Realistic Simulation Tool for practical Analysis of Solar Cooling Thermal Systems driven by Linear Fresnel Collectors

The objectives of this study were to develop a realistic simulation tool to analyze solar thermal cooling systems driven by Fresnel collectors and carry out a case study in which the performance of a solar cooling system of 190 kW located in Riyadh is simulated to demonstrate the functionality and potentiality of the developed tool. This tool is based on an integrated mathematical model that considers the ambient conditions, the thermal loads of the building, the pre-sizing data of each of the components of the system and the simultaneous interaction among them, to conduct a realistic, simple, and precise analysis. A demonstrative simulation example was performed. During the month of July, with a solar opening area of 704 m2 and a tank of 35200 L, a total amount of 47,5 MWh of cooling energy was obtained, with a reduced contribution of the auxiliary system (5,6 MWh) and a minimum number of solar collector system deactivation hours (0,7 %). The daily COP of the absorption machine remained above 0,69. The obtained results from the case study with the simulation tool allowed to verify its functionality, capabilities and correct operation to carry out hourly and parametric studies of this type of systems.

Comparative exergoeconomic evaluation of integrated solar combined-cycle (ISCC) configurations

This paper provides an exergy, economic, and exergoeconomic comparative analysis for the three most promising solar thermal technologies of integrated solar combined-cycle systems: direct steam generation linear Fresnel collectors, solar power tower, and oil parabolic trough collectors. The exergetic analysis shows that configurations using Fresnel collectors result in the highest exergetic efficiencies (44.1%), while the configuration using a solar tower leads to the lowest efficiency of 33.2%. Integrating the solar field into the high-pressure part results in higher efficiencies for day operation. However, this limits the steam cycle to benefit from higher pressure levels, especially during night operation, as the cycle has to operate on the same design pressure level to avoid possible part-load losses. Findings of the economic analysis show that sharing the same power block of the combined-cycle plant results in a significantly lower incremental specific investment cost for concentrated solar power (2545 $/kW) that helps new installations at moderate investments, leading to steeper learning curves of the technology. Configurations using solar collectors with direct steam generation produce electricity at the lowest price of 36.75 $/MWh. The configuration using oil parabolic trough produces electricity at the highest price (38.62 $/MWh).

Transient simulation of hybridized system: Waste heat recovery system integrated to ORC and Linear Fresnel collectors from energy and exergy viewpoint

Industrial waste heat often has a discontinuous flow with considerable fluctuations in both mass flow rates and temperature. Besides, there are challenges associated with the reliability of solar power due to its intermittent nature. The present study has prepared a continuous and steady heat load for the Organic Rankine Cycle (ORC) in two sectors. The first sector, waste heat recovery system (WHRS) of low-temperature gases in an electric arc furnace (EAF) integrated to ORC, secondly the hybrid of WHRS and ORC along with linear Fresnel collectors (LFC). Steam accumulators as thermal energy storage (TES) stabilize the thermal power fluctuations in both WHRS and LFC. The steam accumulator thermodynamic model was simulated in terms of the non-equilibrium thermal model for the liquid and vapor phases. The behavior of the hybridized WHRS was presented with three solar multiples of 1.8, 2.1, 2.8. Constant and continuous thermal power for the ORC was provided with a solar multiple of 2.8 in a full day (20th August) with an average net power of 1252 kW. It should be noted that the transient state of the system was examined from the energy and exergy viewpoint. The thermal and exergy efficiencies of the WHRS integrated with the ORC were 16.4% and 27.1%, respectively. However, the hybridized WHRS concerning thermal and exergy efficiencies were 12.3% and 16.35%, respectively. Moreover, the exergy destruction rate for all system components was calculated, and the maximum value was found to occur in the LFCs.

Calculation of the incidence angle modifier of a Linear Fresnel Collector: The proposed declination and zenith angle model compared to the biaxial factored approach

Since their first appearance as a contribution by Professor Francia at the University of Genova, Italy, the Linear Fresnel Collectors (LFC) demonstrated to be an engineering efficient technology for medium to high temperature solar applications. The strength of the LFC concept is related to the simple mirror motion law, to the compactness of the mirror fields (power to land surface ratios), to the lowest resistance to wind, to the system intrinsic scalability. To perform reliable LCOE analyses, robust performance simulation tools are needed. The Authors developed to this aim a 3D ray-tracing model, able to account for shading, blocking, and end effects as a function of LFC geometry, including primary and secondary mirror curvatures. In this paper, a new approach is implemented to reduce huge yearly ray-tracing datasets and provide very compact analytical equations for fast hourly performance simulations. The present model introduces new Incidence Angle Modifier (IAM) correlations based on the declination and zenith angles. The new model demonstrated to fit subhourly 3D ray-tracing data all year long with an overall error lower than 1.5%, well below the best IAM factored models here compared as a general criticism to the biaxial factored approach related to Fresnel applications.