Compact Linear Fresnel Reflector Research Articles

Design and performance analysis of a novel solar photovoltaic/thermal system using compact linear Fresnel reflector and nanofluids beam splitting device

The current study conducts the performance estimate of a new photovoltaic thermal (PV/T) system using compact linear Fresnel reflector (CLFR) and Ag/CoSO 4 -PG nanofluids beam splitting device (BSD). Design method and working flow of the PV/T system are introduced. The absorption rate of the nanofluids BSD is 58.6% in the full spectral range. The optical behaviour evaluation results reveal a relatively high uniform sunlight irradiance distribution on the nanofluids BSD bottom and a single-peak shape sunlight irradiance distribution on the PV module. The optical efficiency of the PV/T system is 91.5% with a sun-tracking error of 0.2°. The operation behaviour of the PV/T system is analyzed by using the Computational Fluid Dynamics method. The analysis results indicate that the photoelectric efficiency of the PV module and thermal efficiency of the PV/T system are 30.2% and 49.3%. The thermal efficiency will increase when the inlet nanofluids flow velocity augments, or when the inlet nanofluids temperature decreases.

Theoretical design, material study and material selection for compact linear Fresnel reflector concentrating system

A comparative study is made between two different Compact Linear Fresnel reflector concentrating (CLFRC) systems with tubular absorber. The CLFRC systems with constant width reflectors and varying width reflectors are taken for study. The systems are analyzed with design parameters and Material study. By varying various design parameters like width of the reflector plates, shift between the plates, the height of the receiver tube from the reflector plane and diameter of the receiver tube, by using the geometrical equations calculations are done using MATLAB and the optimum values are taken for the design. The solar flux is considered to be a constant of 0.6 kW/m2. Concentrated ratio and concentrated flux are determined for each case to select the best system. Results show that the CLFRC system with constant width plates has better performance with concentration power, C.P = 3.15 kW and concentration ratio, C.R = 103.3 are better than those with varying width plates, while considering optimum design parameters of height from reflector plane, width of the plates and diameter of the receiver tube as 1.5 m, 0.03 m and 0.015 m respectively. The best system is selected through theoretical study and software analysis the system is modified with different reflectors (Glass mirror, Acrylic sheet, Chromium coated sheet, Polished Aluminum sheet) glass mirror is found to be the best reflector based on it reflectivity (ρ = 0.98) and the absorber is coated with different coating materials (Black Copper-Cu, Black Chrome- Ni-Cu/Steel, Black Nickel- Steel/Ni coated steel, Ni-Nox- Al) the best coating material is found to be Black Chrome- Ni-Cu/Steel absorber through theoretical and CFD analysis.

Design and experimental study of a solar CPV system using CLFR concentrator

A solar concentration photovoltaic (CPV) system with compact linear Fresnel reflector (CLFR) concentrator is described in this paper. The design approach of the CPV system is introduced. Four different CLFRs are designed and compared, including one complete type and three hybrid type CLFRs. In order to evaluate the optical performance of the CPV system, solar concentration processes of the four CLFRs are simulated by using the MCRT method. The results indicate that the complete type CLFR (CLFR-c) has the highest concentrated solar radiation uniformity. An experimental set-up is built to carry out the evaluation of actual optical performance of the CLFR-c and a good agreement between the simulation and measurement results is demonstrated. The optical parameter analysis results of the CPV system reveal that the optimal solar panel height exists, which can result in the maximum ground utilization and concentration ratios. The influence of sun-tracking accuracy on the optical efficiency of the CPV system is analyzed. The results indicate that the normalized optical efficiency of the CLFR-c concentrator is 0.89 when the tracking error is 0.2°. The preliminary PV performance test results reveal a photoelectric conversion efficiency of 15.9% for the PV cell module installed on the solar CPV system.

Novel design and thermodynamic analysis of a solar concentration PV and thermal combined system based on compact linear Fresnel reflector

A novel solar concentration photovoltaic (PV) and thermal combined system based on compact linear Fresnel reflector (CLFR) concentrator is proposed. The configuration and structural design approach of the PV and thermal combined system are introduced. The spectral beam splitter is designed by using the Needle optimization approach. Solar concentrating processes are simulated and relevant results show a high solar concentrating uniformity provided by the proposed combined system. The investigations of optical performance and relevant influential factors reveal that there is an optimal solar panel installation height for the proposed combined system when the slope angle and width of solar cells are settled. The effect of sun tracking error on the optical performance is also studied. The energy conversion analysis is carried out and the results show that the PV and thermal combined system has higher PV conversion and overall energy efficiencies in comparison with the solar concentration PV system without beam splitter. Furthermore, the effect of solar thermal collector temperature is investigated and the results reveal that there is an optimal tube collector operating temperature which can lead to the maximum total output power and overall energy efficiency.

Comparative study of the optical and economic performance of etendue-conserving compact linear Fresnel reflector concepts

This paper presents a comparative performance investigation of three Compact linear Fresnel collectors; a flat collector, a sun-tracking etendue-conserving collector and an off-peak etendue-conserving collector. A Monte Carlo ray tracing program is used to simulate the fields. The resultant incident radiation on the receiver aperture is used to quantify the geometric intercept factor and optical efficiency of the field. Each field is then optimised for mirror width and the ratio between the mirrors targeting each receiver aperture. The three fields are then compared on the basis of performance. The off-peak etendue-conserving compact linear Fresnel field reaches a peak geometric intercept factor of 92%, while the sun-tracking etendue-conserving field and flat field had a peak geometric intercept factor of 83% and 79% respectively. A maximum total plant cost for the same Levelized Electricity Cost is presented to incorporate a cost comparison.

Assessment of concentrated solar power (CSP) technologies based on a modified intuitionistic fuzzy topsis and trigonometric entropy weights

Concentrated solar power (CSP) technology has shown considerable long-term growth with varying levels of peak development and stall phases over the years. More and more countries are finding CSP technology attractive for the production of electricity and other applications. CSP offers a variety of applications where solar power can be used appropriately, although the debate about which CSP technology has a better future perspective is still ongoing. This technology sector has seen a multitude of advancements and technological innovations. These improvements are primarily concerned with the design of the collectors and the related materials they are made from, the heat transfer processes, and the production and accumulation of energy.In order to assess these CSP technologies, in this paper we propose a fuzzy multi-criteria method. Then, Solar tower (ST), Parabolic solar trough (PST), Compact linear Fresnel reflector (CLFR), and Dish Stirling (DS) are evaluated using a modified intuitionistic fuzzy TOPSIS with a trigonometric entropy vector weight.

Optical design of compact linear fresnel reflector systems

Compact linear Fresnel reflector (CLFR) system employing multiple receivers is promising with better optical performance and cost effectiveness compared to linear Fresnel reflector (LFR) system, especially for applications with limited ground availabilities. Nevertheless, only few researches have been conducted to evaluate optical design and performance of the CLFR system. In this study, geometrical models for the CLFR system with flat mirrors and receivers are developed on the basis of polar orientation. A comparative study of concentration characteristics among the LFR, CLFR-complete and CLFR-hybrid systems is conducted based on numerical, ray tracing simulation and experimental results. In addition, optical design analyses of the CLFR-hybrid system are carried out from various design aspects. It is noteworthy that the mirror arrangement and focal length should be optimized for the CLFR-hybrid system with considerations of the associated geometrical characteristic and optical performance. For a small-scale CLFR-hybrid system with a solar field width of 2100mm and a focal length of 1500mm, the geometrical concentration ratio of 15.14 and ground utilization ratio of 0.95 are achieved respectively. The findings demonstrate the feasibility of the CLFR-hybrid system with flat mirrors and polar orientation, which provide progress to the concentrated solar power technology.

Effects of shading and blocking in compact linear fresnel reflector field

In a compact linear fresnel reflector field, ‘s’ number of reflector-rows lying between two receivers can be configured in 2s ways. Each possible configuration will lead to different energy loss, electricity generation and cost of electricity. The variations in energy losses, energy collection by fluid, electricity generation and cost of electricity with length (L) and width (w) of aperture of a reflector-row, spacing between adjacent reflector-rows (p), number of reflector-rows (2n), receiver-height (H), collector-configuration and location have been studied. It is found that the collector configuration has no significant effect on annual shading. However, it affects annual energy losses due to cosine effect, blocking and the factors τ and α significantly. As a result, the cost of electricity can be improved significantly by varying collector configuration. The cost of electricity decreases with increment in p/w and later on, it starts increasing. The best p/w ratio corresponding to minimum cost of electricity is 1.44 for H/nw = 0.3 and 1.85 for H/nw = 0.7. The energy collection by fluid increases rapidly with increment in H/nw initially. However, beyond H/nw about 0.7, further increase in H/nw does not lead to significant increase in energy collection.

Comparison of line focusing solar concentrator fields considering shading and blocking

The performance of line focusing solar collectors [Parabolic Trough Concentrator (PTC), Linear Fresnel Reflector (LFR) and Compact Linear Fresnel Reflector (CLFR)] is affected by many factors. Due to end effect, inter-row shading and blocking (for LFR and CLFR), the complete aperture of the collector cannot be utilized. Besides, the cosine effect, reflectivity of reflectors, intercept factor, transmissivity of receiver cover, absorptivity of absorber tube and thermal losses are the other major contributors to the energy losses. In the current work, PTC, LFR and CLFR fields are compared in terms of energy losses, net energy collection by fluid, electricity generation and cost of electricity. The ratio of collector aperture area to land area is named as land coverage ratio. The appropriate values of land coverage ratio are found out corresponding to minimum cost of electricity for different technologies. The corresponding annual energy collection by fluid and the annual electricity generation have also been calculated. It is seen that there is no significant difference in the performance of LFR and CLFR fields. For low values of receiver height to collector width ratio, the LFR field results in the largest levelised cost of electricity and the PTC field results in the lowest.

Innovative solar augmentation of gas turbine combined cycle plants

The objective of this paper is to offer а concept for innovative hybridization of gas turbine combined cycle plant and solar power system. This conceptual plant is named as Solar Assisted Combined Cycle, as the solar energy is indirectly involved in power generation. The proposed solar hybridization can be accomplished in two ways. The first solar assisted option introduces mechanical chiller for a complete cooling of gas turbine inlet air. Such of cooling is commonly used to increase the power output of gas turbines during hot days of the year. This mechanical chiller is powered with electricity generated by a dedicated photovoltaic plant. The next solar assisted option does the same but with an absorption chiller. The steam for this chiller is generated in a solar field equipped with Linear Fresnel Reflectors. The efficiency and the total additional costs for development of these two configurations are estimated with relevant software packages. Similar power augmentation can be achieved with traditional Integrated Solar Combined Cycle plant. All main additional costs for construction of this alternative plant are also estimated. As a result, the specific costs for solar augmentation of a basic GTCC plant are obtained and compared. The configuration with an absorption chiller has lower specific incremental plant capital costs and requires smaller land area than the others. The proposed solar assisted plant concept offers an effective way for further implementation of compact linear Fresnel reflector technology.

Heat loss characteristics of trapezoidal cavity receiver for solar linear concentrating system

In this paper, a numerical study of combined natural convection and surface radiation heat transfer in a solar trapezoidal cavity absorber for Compact Linear Fresnel Reflector (CLFR) is presented. The CFD package, FLUENT 6.3 is used to develop the 2-D, non-Boussinesq, steady state, laminar, combined natural convection and surface radiation heat transfer model for a trapezoidal cavity absorber. The validation of the present non-Boussinesq numerical procedure is compared with other closed cavity model. Based on the validated non-Boussinesq model, the combined heat loss coefficients are predicted for various parameters such as Grashof number, absorber angles, surface emissivity, aspect ratio, temperature ratio and radiation–conduction number. The numerical simulation results are presented in terms of Nusselt number correlation to show the effect of these parameters on combined natural convection and surface radiation heat loss.

Toward clean environment: evaluation of solar electric power technologies using fuzzy logic

The rapid expansion of the use of solar energy power plants worldwide is a subject that is being followed with interest. Fuzzy logic methodology is used for evaluating the solar thermal power technology, it compresses huge amount of data into smaller sets, and it has the ability to decide between different solar technologies on the basis of their benefits and costs. The most often considered solar technologies were parabolic trough, central receiver, dish sterling engine, compact linear Fresnel reflector (CLFR), solar chimney, photovoltaic (PV), and solar pond. The aim of our research is to provide the needed information to make a judgment or a decision of adopting the most preferred solar technology in terms of installation and development using fuzzy set methodology. The criteria of the evaluation were based on different parameters, i.e., power capacity, efficiency, availability, capacity factor, storage capability, cost, maturity, water usage, land usage, and safety. The key barriers and features for each technology on the basis of benefit-to-cost ratios are addressed. The results showed that CLFR was found to be the best choice in terms of research, development, and implementation, followed by parabolic trough technology, then the central receiver technology, dish sterling engine, solar chimney, PV, and solar pond, according to the order of preference.

Etendue-matched two-stage concentrators with multiple receivers

A possible way to concentrate sun light is by using a Fresnel reflector: a large number of small mirrors (called heliostats) that mimic the behavior of a large concentrator, replacing it. These heliostats can move to track the sun, keeping its light concentrated onto the receiver. Fresnel concentrators, however, may have important losses. If the heliostats are spaced from each other, some light will miss them and be lost. If the heliostats are close to each other, they will block part of each other’s reflected light, also producing losses. One possible way to minimize these losses is to intersect two focusing Fresnel concentrators forming a Compact Linear Fresnel Reflector – CLFR. Although improving on a simple focusing Fresnel concentrator, these optics are still not optimal. Here new geometries for Fresnel reflectors are explored, minimizing their losses and increasing their concentration. This is achieved by changing the overall shape of the primary, making it a wave-shaped trough surface and/or by allowing for a variable size and shape of the heliostats as a function of the position in the heliostat field. These new Fresnel concentrators may also be combined with secondaries significantly improving their total concentration, which now approaches the theoretical maximum.

Multi-tower Line Focus Fresnel Array Project

As an alternative to conventional tracking solar thermal trough systems, one may use line focus Fresnel reflector systems. In a conventional Fresnel reflector design, each field of reflectors is directed to a single tower. However, efficient systems of very high ground utilisation can be setup if a field of reflectors uses multiple receivers on different towers. This paper describes a line focus system, called the compact linear fresnel reflector system and a project to produce an initial 95 MWth solar array. The array will be used as a retrofit preheater for a coal fired generating plant.

An experimental and computational study of the heat loss characteristics of a trapezoidal cavity absorber

A solar thermal power project that makes use of a compact linear Fresnel reflector array to concentrate solar radiation onto a stationary absorber cavity suspended above the array has been proposed. The cavity is trapezoidal in cross-section. The upper surface of the cavity is a flat plate absorber with steam tubes running behind it. The lower surface is a glass window that allows solar radiation, focused by the mirror array, to enter the cavity. Heat loss from the absorber occurs via a complex interaction between radiation, convection and conduction within the cavity, and then from the cavity to the surroundings. This paper describes the experimental techniques used to investigate the heat losses from the absorber, and the flow visualization technique used to capture the flow patterns within the cavity. It then goes on to compare the experimental results with predictions obtained from a model developed using FLUENT, a commercially available computational fluid dynamics package. Excellent agreement is achieved between the flow patterns observed in the experiment and those predicted by the computational model. Reasonable agreement between the experimentally determined heat losses and those predicted by the computational model are also shown to exist.

Heat transfer aspects of an elevated linear absorber

This paper describes aspects of the design methodology and heat transfer calculations for an elevated north–south oriented linear absorber. The absorber is part of a direct steam generation solar thermal concentrating system based on the Australian compact linear Fresnel reflector (CLFR) concept. The basic absorber design is an inverted air cavity with a glass cover enclosing a selective surface. This arrangement has been shown previously to offer good optical and thermal performance from measurements on a 4 kW thermal outdoor test apparatus. Two main design aims are discussed here: Firstly to maximise the heat transfer between the absorbing surface and the steam pipes, and secondly, to ensure that the absorber surface temperature is sufficiently uniform so as not to cause thermal degradation of the selective surface. Results are given of the absorber temperature distribution obtained from finite element analysis. Sufficiently low temperature differences between the fluid surface and the absorbing surface (<20 K) can be achieved with satisfactory pipe separations and sizes, and with practical absorber plate thicknesses.

Compact Linear Fresnel Reflector solar thermal powerplants

This paper evaluates Compact Linear Fresnel Reflector (CLFR) concepts suitable for large scale solar thermal electricity generation plants. In the CLFR, it is assumed that there will be many parallel linear receivers elevated on tower structures that are close enough for individual mirror rows to have the option of directing reflected solar radiation to two alternative linear receivers on separate towers. This additional variable in reflector orientation provides the means for much more densely packed arrays. Patterns of alternating mirror inclination can be set up such that shading and blocking are almost eliminated while ground coverage is maximised. Preferred designs would also use secondary optics which will reduce tower height requirements. The avoidance of large mirror row spacings and receiver heights is an important cost issue in determining the cost of ground preparation, array substructure cost, tower structure cost, steam line thermal losses, and steam line cost. The improved ability to use the Fresnel approach delivers the traditional benefits of such a system, namely small reflector size, low structural cost, fixed receiver position without moving joints, and non-cylindrical receiver geometry. The modelled array also uses low emittance all-glass evacuated Dewar tubes as the receiver elements. Alternative versions of the basic CLFR concept that are evaluated include absorber orientation, absorber structure, the use of secondary reflectors adjacent to the absorbers, reflector field configurations, mirror packing densities, and receiver heights. A necessary requirement in this activity was the development of specific raytrace and thermal models to simulate the new concepts.

Modelling study for compact Fresnel reflector power plant

This paper describes Compact Linear Fresnel Reflector (CLFR) concepts suitable for large scale solar thermal electricity generation plants. In the CLFR it is assumed that there will be many parallel receiver towers that are close enough for individual reflectors to have the option of directing reflected solar radiation to two linear receivers on separate towers. This additional variable in reflector orientation provides the means for much more densely packed arrays. Patterns of alternating reflector orientation can be set up such that closely packed reflectors can be positioned so that shading and blocking are almost eliminated. The avoidance of large reflector spacings and tower heights is an important cost issue in determining the cost of ground preparation, array substructure cost, tower structure cost, steam line thermal losses, and steam line cost. The improved ability to use the Fresnel approach delivers the traditional benefits of such a system, namely small reflector size, low structural cost, fixed receiver position without moving joints, and non-cylindrical receiver geometry. The modelled array also uses advanced all glass evacuated tubular absorbers with low emittance selective coatings.