Now showing 1 - 7 of 7
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Numerical investigation of micro-channel based active module cooling for solar CPV system

01-01-2014, Srinivasa K Reddy, Lokeswaran, S., Agarwal, Pulkit, Mallick, Tapas K.

Concentrating photovoltaic (CPV) technology is one of the fastest growing solar energy technologies achieving higher electrical conversion efficiencies. The increase in temperature of solar CPV cell significantly reduces the performance; the efficiency of a CPV system can be improved by introducing effective thermal management or cooling system. This paper presents the design and numerical analysis of a heat sink based on micro-channels for efficient cooling of a commercial high concentration photovoltaic (HCPV) cell. A combinatory model of an array of micro-channels enclosed in a wide parallel flow channel design is developed. The optimized geometry of the micro-channel heat sink was found by using commercial CFD software ANSYS 13. Based on numerical simulations, it is found that the optimum configuration of micro-channel with 0.5mm width and aspect ratio of 8. The micro-channels provided high heat transfer over heat generations spots and parallel flow channels resulted in lower pressure drop. The temperature rise across the micro-channel is estimated as10K in CPV module of 120 × 120 mm2 and with a pressure drop of 8.5 kPa along a single channel with six such channels in each modules at a flow rate of 0.105 liter/s. © 2014 The Authors.

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Investigation of heat losses from the trapezoidal cavity receiver for linear fresnel reflector solar power system

01-12-2011, Srinivasa K Reddy, Ravi Kumar, K.

Medium and high temperature heat can be produced by using concentrating solar power (CSP) technologies. Among CSP technologies, linear Fresnel reflector (LFR) system is simple in design and cost effective technology for medium temperature (400°C) applications. In this article, the numerical investigation of the receiver for LFR system is carried out to estimate the combined convective and radiative heat losses. The 2-D numerical simulation of trapezoidal cavity receiver is carried out using commercial CFD package, Fluent - 6.3. The cavity receiver surface absorbs maximum amount of reflected solar radiation with minimum heat losses. At steady state conditions, the cavity receiver surface will attain almost uniform temperature; therefore, an isothermal boundary condition and also Boussinesq approximation are considered in the numerical simulations. To account the radiation exchange between the surfaces, the surface-to-surface model is used. The heat loss analyses are carried out for various receiver geometric and operating parameters viz. aspect ratio (ratio of receiver aperture to receiver width), cavity depth and width, operating temperature and wind speed. Based on the numerical analysis of the receiver, an optimum configuration of the receiver is found at insulation thickness of 300 mm, cavity depth of 300 mm with an aspect ratio of 2. The total heat loss varies from 614.32 W/m to 968.8 W/m for absorber width of 300 mm to 800 mm at 500°C receiver temperature, 0.5 cavity cover emissivity and 2.5 m/s wind velocity. The effect of cavity cover emissivity on total heat loss is found to be less significant when compared to that of other cavity parameters. The optimum configuration of the inverted trapezoidal cavity receiver is arrived based on the heat loss analysis of the receiver.

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Numerical investigation of solar parabolic trough receiver under non uniform solar flux distribution

01-01-2015, Ananthsornaraj, C., Srinivasa K Reddy

Three dimensional numerical modeling of parabolic trough receiver is performed to study the non uniform flux distribution on the outer surface of the receiver by coupling Monte Carlo Ray-Tracing Method (MCRT) with the Finite Volume Method (FVM) and calculated non uniform flux distribution is considered as a thermal boundary condition. The numerical model is solved by considering RNG k-ϵ turbulent model. In this paper, different Heat Transfer Fluids (HTF) with respect to the various operating parameters such as mass flow rate, Direct Normal Irradiation (DNI), inlet temperature and ambient conditions are considered. The temperature profile of both absorber and glass envelope follows the non-uniform solar heat flux distribution curve. Three dimensional temperature distribution of the absorber tube is calculated numerically for different inlet temperature and velocity of HTF. The maximum solar heat flux attained by the PTC receiver is 9753.3 W/m2, 19506 W/m2, 29260 W/m2, and 39013 W/m2 when the DNI are 200 W/m2, 400 W/m2, 600 W/m2, and 800 W/m2 respectively.

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Performance analysis of concave cavity surface receiver for a non - Imaging solar concentrator

01-01-2015, Srinivasa K Reddy, Srihari Vikram, T.

In the present study, a numerical investigation of concave surface cavity receiver of non-imaging solar concentrator is carried out considering various operating and geometrical parameters such as mass flow rate of the fluid, solar radiation and receiver configuration. The fluid outlet temperature, pressure drop across the coil for different receiver configurations are studied along with the heat loss estimation of concave cavity surface receiver for non-imaging concentrating collector. The convective and radiative heat loss from the receiver surface is calculated based on 3-D numerical simulations. For helical receiver, the temperature rise is found to be 30°C (0.5kg/min) and 17°C (1kg/min) respectively; whereas for helical-spiral receiver, the temperature rise is found to be 27°C (0.5 kg/min) and 15°C (1 kg/min). The pressure drop across the coil ranges between 1kPa to 14kPa for different mass flow rate and solar radiation for two configurations of the receiver. The present model can be used for estimating the heat transfer and fluid flow characteristics of helical receiver for EHC.

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Design of a 16-cell densely-packed receiver for high concentrating photovoltaic applications

01-01-2014, Micheli, Leonardo, Sarmah, Nabin, Luo, Xichun, Srinivasa K Reddy, Mallick, Tapas K.

A novel densely packed receiver for concentrating photovoltaics has been designed to fit a 125× primary and a 4× secondary reflective optics. It can allocate 16 1cm2-sized high concentrating solar cells and is expected to work at about 300 Wp, with a short-circuit current of 6.6 A and an open circuit voltage of 50.72 V. In the light of a preliminary thermal simulation, an aluminum-based insulated metal substrate has been use as baseplate. The original outline of the conductive copper layer has been developed to minimize the Joule losses, by reducing the number of interconnections between the cells in series. Slightly oversized Schottky diodes have been applied for bypassing purposes and the whole design fits the IPC-2221 requirements. A fullscale thermal simulation has been implemented to prove the reliability of an insulated metal substrate in CPV application, even if compared to the widely-used direct bonded copper board. The Joule heating phenomenon has been analytically calculated first, to understand the effect on the electrical power output, and then simulate, to predict the consequences on the thermal management of the board. The outcomes of the present research will be used to optimize the design of a novel actively cooled 144-cell receiver for high concentrating photovoltaic applications. © 2014 The Authors.

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Design of non-imaging solar collectors for process heat

01-01-2017, Srinivasa K Reddy, Srihari Vikram, T.

In this article, a comprehensive optical analysis of a non-imaging elliptical hyperbolic concentrating collector has been carried out. This collector system has a wide acceptance angle so that it can be operated with no/minimum tracking based on the location of operation. Two types of receivers say flat and trapezoidal surface are considered and the flux distribution over these receivers are estimated and compared. It is found that maximum peak flux is intercepted by the trapezoidal surface receiver. The effect of concentrator geometrical parameters such as concentrator height (Hc) and concentration ratio (CR); receiver geometrical parameters such as aperture width (Wr) and receiver height (Hr) on optical performance of the collector has been studied. The optical efficiency varies between 5-15 % for the concentrators with height less than 1 m whose acceptance angle is about 60°, whereas for the concentrator height greater than 1m, the acceptance angle is +45° and the optical efficiency varies between 20-30 % for incidence angles +30°. The maximum flux incident on the trapezoidal surface is about 60585 W/m2 however for flat surface, it is 40468 W/m2. Based on the optical analysis, it can be seen that this system can be widely used for applications such as low and medium temperature applications and it requires less/no tracking with wider acceptance angle.

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Improvement of solar thermal plant efficiency by the use of secondary concentrators

01-01-2018, Sundararajan, T., Reddy, K. S., Balaji, Shanmugapriya, Chaitanya Prasad, G. S.

A solar collector field based on linear Fresnel reflectors has been set up with support from the Department of Science and Technology, Government of India. Fresnel mirrors coupled with secondary concentrator are employed to focus solar radiation on a coated stainless steel receiver tube of 70 mm diameter. The collector system directly generates superheated steam at about 45 bar and 400oC. The receiver tube is covered with borosilicate glass, with the annular space evacuated to reduce heat losses. Theoretical studies have been carried out to optimize the secondary concentrator profile and to assess the heat losses from the solar collector. Compound-parabolic, trapezoidal and segmented- parabolic configurations are considered for the secondary concentrator. It is shown that the segmented parabolic configuration can provide high optical efficiency as well as nearly uniform flux distribution on the receiver tube. Evacuation of the annular space between the absorber tube and the glass cover, significantly reduces heat losses and improves the temperature distribution within the absorber.