Srinivasa K Reddy

In this paper, thermal performance analysis of 20m2 prototype fuzzy focal solar dish collector is presented. The focal image characteristics of the solar dish are determined to propose the suitable design of absorber/receiver. First, theoretical thermal performance analysis of the fuzzy focal solar parabolic dish concentrator with modified cavity receiver is carried out for different operating conditions. Based on the theoretical performance analysis, the total heat loss (conduction, convection and radiation heat losses) from the modified cavity receiver is estimated. It is observed that the maximum theoretical efficiencies of solar dish collector are found to be as 79.2% for no wind conditions and 78.2% and 77.8% for side-on and head-on winds speed of 5m/s respectively. Latter, real time analysis of parabolic dish collector with modified cavity receiver is carried out in terms of stagnation test, time constant test and daily performance test. From stagnation test, the overall heat loss coefficient is found to be 356W/m2K. The time constant test is carried out to determine the influence of sudden change in solar radiation at steady state conditions. The daily performance tests are conducted for different flow rates. It is found that the efficiency of the collector increases with the increase of volume flow rates. The average thermal efficiencies of the parabolic dish collector for the volume flow rate of 100L/h and 250L/h are found to be 69% and 74% for the average beam radiation (Ibn) of 532W/m2 and 641W/m2 respectively. © 2014 Elsevier Ltd.

In the present work, structural and optical analysis of 23.08 m2 (Aaperture) solar parabolic trough has been done utilizing different composite materials with an optimized modelling approach. The linear parabolic trough collector is subjected to gravity and wind loads and thereby it undergoes surface deformations. Various trough materials are structurally analysed and a hybrid composite is designed. The RMS values of local slope deviations of trough termed as SD value is calculated using Modified Element Approach to observe the behaviour of trough at various tracking positions varying from 0° to 90° orientations. The cases been discussed are trough-alone (stiff) case and full collector (elastic) case under gravity and wind loading conditions with wind speed of 15 m/s. Trough parameters like fibre orientation of laminae, stacking sequence and direction and size of reinforcement conduits are optimized to minimize SD values. Furthermore, the setup is optically studied and the slope deviations are compared for individual models through intercept factors (γ). The comparative study reveals that the solar parabolic trough collector with its facets made of woven jute/glass fibre-reinforced polyester hybrid composite material yields γmax = 0.957 for avg. SD = 1.34 mrad in stiff case and γmax = 0.955 for avg. SD = 1.349 mrad in elastic case under gravity load, and γmax = 0.866 for avg. SD = 3.78 mrad in stiff case and γmax = 0.863 for avg. SD = 3.81 mrad in elastic case under both wind and gravity loads, resulting to be the best among considered models. Maximum weight reduction of up to 30% in stiff case and up to 4.5% in elastic case has also been observed compared to conventional glass collector for hybrid composite model thus reducing the tracking power and producing a cost effective system.

In this article, heat transfer enhancement of line focus solar collector with porous disc receiver is studied with water and therminol oil. A three dimensional (3-D) numerical simulation of porous disc enhanced receiver is carried out using commercial CFD software Fluent 6.3 to evolve the optimum configuration. The 3-D numerical model is solved by renormalization-group based k-e turbulent model associated with standard wall function. The effect of porous disc receiver configurations (solid disc at bottom; porous disc at bottom; porous disc at top; and alternative porous disc) on performance of the trough concentrator is investigated. The effect of porous disc geometric parameters (φ, θ, W, H and t) and fluid parameters (Pr and m) on heat transfer enhancement of the receiver is also studied. The numerical simulation results show that the flow pattern around the solid and porous discs are entirely different and it significantly influences the local heat transfer coefficient. The porous disc receiver experiences low pressure drop as compared to that of solid disc receiver due to less obstruction. The optimum configuration of porous disc receiver enhances the heat transfer rate of 221 W m -1 and 13.5% with pumping penalty of 0.014 W m -1 for water and for therminol oil-55, heat transfer rate enhances of 575 W m -1 and 31.4% with pumping penalty of 0.074 W m -1 as compared to that of tubular receiver at the mass flow rate of 0.5 kg s -1. The Nusselt number and friction factor correlations are proposed for porous disc receiver to calculate heat transfer characteristics. The porous disc receiver can be used to increase the performance of solar parabolic trough concentrator. © Springer-Verlag 2011.

The Multi-layered Thermal Energy Storage (TES) tank consists of three regions–top and bottom part is packed with suitable Phase Change Materials (PCM) and low-cost pebbles are placed in the middle region, whereas entire tank portion is filled by solid fillers in Single-layered tank system. For a storage tank operating between 563 and 663 K with bed dimensions of 12 and 14.38 m using Solar salt as Heat Transfer Fluid (HTF), it is observed that the duration of discharge for multi-layered tank is 5.32 h whereas it is 4.19 h for single-layered tank with a Reynolds number of 10. The effect of intermediate melting temperature range of PCMs are also analyzed by taking PCMs with sharp as well as intermediate melting ranges. Further, comparison of single and multi-layered systems is carried out by analyzing the temperature profiles and width of both PCM layers. The width of top and bottom PCM layers of tank is varied from 0 to 30% to analyze its effect on the discharging duration. It is observed that multi-layered system provides extra discharge of 1 h with introduction of PCM at top and bottom with a width of 10%. Discharge duration increases with increase in PCM width whereas the percentage increase in duration of discharge with increase in PCM width is comparatively less. It is also seen that PCMs with sharp melting point performs better compared to one having intermediate range of melting temperatures. Multi-layered configuration concept offers best possibilities as integration to CSP plants with desired efficiency.

Cogeneration plant produces heat and electricity simultaneously, and have a great potential towards best use of primary energy resources as compared to other plants, which produces heat and electricity separately. Parabolic trough integrated cogeneration power plant (PTICPP) is one of the attractive alternatives to utilising solar energy in an efficient manner. The economically viable PTICPP could bring an opportunity for its utilisation at large scale. Therefore, estimation of the levelised cost of electricity (LCE) is done by two different rational cost apportionment method namely; lost-kilowatt and exergy method. To achieve the objective of this paper, a reference PTICPP having a capacity of 20 MWe and 61.94 MWth is designed, and comprehensive thermal performance of reference plant is analysed at the variable amount of irradiation. In Indian climatic condition, the minimum estimated LCE are 0.127 $/kWh and 0.114 $/kWh respectively by lost-kilowatt and exergy method.

A two-dimensional numerical analysis has been carried out to study the phenomenon of thermal striping in a prototype fast breeder reactor using a 10-jet water model that represents a row of the reactor core consisting of fuel and blanket zones. The above-core structures in the reactor are modeled with a porous lattice plate and solid core cover plate. The Reynolds stress model is used for simulating the turbulence characteristics of jet mixing phenomena. When the ratio of hot jet velocity to cold jet velocity is equal to 1, maximum fluctuations of temperature have been observed. Also the temperature fluctuations reduced gradually beyond a hot jet to cold jet velocity ratio of 1.0. The lattice plate is found to be more prone to thermal striping as compared to the core cover plate. © 2011 Taylor and Francis Group, LLC.

A plasmonic LaFeO3-Ag (LFO-Ag) photocathode was synthesized by incorporating Ag nanoparticles to excite surface plasmon resonances (SPRs) for enhanced light harvesting to drive photoelectrochemical (PEC) hydrogen evolution. The Ag nanoparticles were modeled using finite difference time domain (FDTD) simulations, and the results show an optimal dimension of 50-80 nm for SPR enhancement. Nanostructured LFO films were prepared by a novel and inexpensive spray pyrolysis method, and the Ag nanoparticles were dispersed uniformly on to the films by simple spin coating method. The LFO-Ag photocathode exhibited strong light absorption capability and high current density, twice that of its untreated counterpart. This subsequently led to enhanced PEC hydrogen evolution, doubling the volume of hydrogen generated compared to untreated LFO. The enhancement is ascribed to the strong SPR effect and the synergy between the Ag nanoparticles and nanostructured LFO photocathode.

Solar parabolic trough collector is one of the most potential Concentrated Solar Power (CSP) technologies with high dispatchability. The performance of the Parabolic Trough Collector (PTC) is significantly influenced by the distribution of radiant flux around the line focus receiver. In this paper, an accurate estimation of radiant flux around the line focus receivers of different parabolic trough collectors of varying aperture widths from 5 to 7.5 m has been studied. Effects of total internal reflection in the glass tube, glass tube absorptivity, receiver reflectivity, limb-darkening effect, surface errors and anti-reflective coating have been considered. A direct steam generation model (recirculation mode) has been developed and the effect of geometric errors in the collector on its optical and thermal performance characteristics has been discussed. The thermal efficiency of the direct steam generation collector is influenced by the optical characteristics of the collector and hence the thermal efficiency at different optical errors has been evaluated for the fore-mentioned commercial collectors under the influence of declination. The thermal efficiency is more sensitive to optical errors at low insolation levels and vice versa. For a change in tracking from 0 to 10 mrad, for PTC7.3 configuration, thermal efficiency drops by 0.58% at 1000 W/m2, and 2.02% at 300 W/m2. The thermal efficiency is also more sensitive to optical errors at higher values of declination. The collector of low geometric concentration ratio has a low sensitivity and low thermal efficiency and vice versa. Hence, the overall efficiency of different collectors at different optical errors has to be studied so as to obtain the appropriate collector configuration for specified optical errors and location of installation. Based on the analysis, graphical results which could aid in the selection of best collectors based on the latitude location, DNI and optical errors has been developed. The evaluation of collectors has also been extended towards power plant characteristics. The nominal power has been set to 50 MW. The location of Jodhpur in India has been selected and the total power generated per unit area has been studied for different collectors, for different optical errors. Based on the graphical results developed, appropriate collectors may be chosen for those locations based on their associated optical errors.

In this work, detailed investigations of convection heat loss from conical cavity receiver of solar parabolic dish collector using a numerical method and artificial neural network have been performed. The convective heat loss from the cavity receiver is primarily influenced by geometrical parameters, receiver orientation, and wind characteristics. The heat loss estimation is carried out by considering wind speed (V = 0–10 m/s), wind direction ((Formula presented.) = 90 (Formula presented.) and −90 (Formula presented.)), receiver tilt ((Formula presented.) = 0–90 (Formula presented.)), diameter to height ratio (d/h = 0.5–1.5), and surface temperature (T s = 500–800 K). The utmost heat loss occurs at a tilt of 60 (Formula presented.) for d/h < 1 and 75 (Formula presented.) for d/h (Formula presented.) 1 in head-on high wind speed, while in back-on high wind speed, it occurs at a tilt of 30 (Formula presented.) for all d/h values. The heat loss is lowest at 90° for V > 4 m/s. The d/h value of 0.5 performs well compared to other values. Further, the correlation for the Nusselt number has been proposed for the conical cavity receiver.

In this work, a non-imaging low concentrating 2.5X Compound Parabolic Concentrator (CPC) truncated to 1.7X has been explored. CPCs inherently form non-uniform distribution of flux on the PVT module which has been mitigated by the integration of optimized homogenizer referred to as Elongated CPC (ECPC). The study involves detailed optical, thermal, and electrical modeling of the ECPC based Low Concentrating Photovoltaic Thermal (LCPVT) system. Optical simulations provide insight into the flux distribution on the PVT panel surface, which is further coupled with a thermal and electrical model for precise prediction of the performance of the system. These models are validated experimentally with a 315 Wp solar panel integrated with ECPC based LCPVT system. Performance evaluation of the system has shown peak thermal efficiency of ∼40% at ΔT of 16 °C, peak electrical efficiency of 12%, and an overall peak exergy efficiency of 15% at 38 Liters per hour (LPH) flow rate. A comparison of outlet water temperature results obtained from the numerical model and experiments has shown an excellent match with a relative error of 4%. Results also show that the increase in mass flow rate from 22 LPH to 38 LPH improves the electrical efficiency by 3% however a drop in ΔT of 2–3 °C is observed.