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Research Papers

Thermal Performances of a High Temperature Air Solar Absorber Based on Compact Heat Exchange Technology

[+] Author and Article Information
B. Grange

CNRS (Odeillo, France) and EDF R&D (Clamart, France,), 7 rue du Four Solaire, 66120 Font Romeu, France benjamin.grange@promes.cnrs.fr

A. Ferrière

 CNRS (Odeillo, France)

D. Bellard

 CNRS (Odeillo, France) and  CEA (Grenoble, France)

M. Vrinat

 SOGREAH (Lyon, France)

R. Couturier, F. Pra

 CEA (Grenoble, France)

Y. Fan

 LOCIE-CNRS/université de Savoie (Chambéry, France)

J. Sol. Energy Eng 133(3), 031004 (Jul 19, 2011) (11 pages) doi:10.1115/1.4004356 History: Received January 17, 2011; Revised May 16, 2011; Published July 19, 2011; Online July 19, 2011

In the framework of the French PEGASE project (Production of Electricity by GAs turbine and Solar Energy), CNRS/PROMES laboratory is developing a 4 MWth pressurized air solar receiver with a surface absorber based on a compact heat exchanger technology. The first step of this development consists in designing and testing a pilot scale (1/10 scale, e.g., 360 kWth) solar receiver based on a metallic surface absorber. This paper briefly presents the hydraulic and thermal performances of the innovative pressurized air solar absorber developed in a previous work. The goal is to be capable of preheating pressurized air from 350 °C at the inlet to 750 °C at the outlet, with a maximum pressure drop of 300 mbar. The receiver is a cavity of square aperture 120 cm × 120 cm and 1 m deepness with an average concentration in the aperture of more than 300. The square shaped aperture is chosen due to the small scale of the receiver; indeed, the performances are not enhanced that much with a round aperture, while the manufacturability is much more complicated. However in the perspective of PEGASE, a round aperture is likely to be used. The back of the cavity is covered by modules arranged in two series making the modular and multistage absorber. The thermal performances of one module are considered to simulate the thermal exchange within the receiver and to estimate the energy efficiency of this receiver. The results of the simulation show that the basic design yields an air outlet temperature of 739 °C under design operation conditions (1000 W/m2 solar irradiation, 0.8 kg/s air flow rate). Using the cavity walls as air preheating elements allows increasing the air outlet temperature above 750 °C as well as the energy efficiency up to 81% but at the cost of a critical absorber wall temperature. However, this wall temperature can be controlled by applying an aiming point strategy with the heliostat field.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 6

Solar flux distribution on the four cavity walls (left, right, up, and down) for a 1 m deep cavity−αcav  = 1 −DNI = 1000 W/m2 —Simulations at noon—12 heliostats used

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Figure 7

Crossed aiming point strategy

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Figure 8

Side view of the receiver

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Figure 9

Layout of the modules within the absorber—Two active stages in series

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Figure 10

Top view of the receiver—Preheating around the cavity

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Figure 11

Discretization of the cavity

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Figure 12

Discretization of the absorber with each element incident flux (kW/m2 )

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Figure 13

Geometry of the view factors calculation [11]

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Figure 14

Air outlet temperature (red, bottom) and wall temperature (black, top) of each element of the receiver (°C)—Flux distribution of the reference case

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Figure 15

Air outlet temperature (red, bottom) and wall temperature (black, top) of each element of the receiver (°C)—Whole cavity used to preheat the fluid—Flux distribution of the reference case

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Figure 16

Air outlet temperature (red, bottom) and wall temperature (black, top) of each element of the receiver (°C)—Whole cavity used to preheat the fluid—Flux distribution provided by a crossed aiming point strategy with a 20 cm deviation

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Figure 17

Share of the different powers inside the cavity as a percentage of the incident power on the aperture

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Figure 4

Heliostat field of Themis (the 12 heliostats used for Mini-Pegase are filled in yellow)

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Figure 5

Solar flux distribution on the absorber for a 1 m deep cavity−αabsorber  = 1− DNI = 1000 W/m2 −Simulations at noon—12 heliostats used

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Figure 1

Scheme of the Porcupine absorber concept [4]

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Figure 2

A Porcupine model tested at the Weizmann Institute’s Solar Furnace

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Figure 3

Internal structure of a module (dimensions are in mm)

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