0
Research Papers

A 9-m-Aperture Solar Parabolic Trough Concentrator Based on a Multilayer Polymer Mirror Membrane Mounted on a Concrete Structure

[+] Author and Article Information
Roman Bader, Andrea Pedretti

 Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland Airlight Energy Holding SA, 6710 Biasca, Switzerland

Aldo Steinfeld1

 Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland Solar Technology Laboratory, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland e-mail: aldo.steinfeld@ethz.ch

1

Corresponding author.

J. Sol. Energy Eng 133(3), 031016 (Jul 28, 2011) (12 pages) doi:10.1115/1.4004353 History: Received January 11, 2011; Accepted May 17, 2011; Published July 28, 2011; Online July 28, 2011

A large-span solar parabolic trough concentrator is designed based on a multilayer polymer mirror membrane mounted on a rotatable concrete structure. The multilayer membrane is contained in a transparent protective air tube and generates a multicircular profile that approaches the trough parabolic shape. An analytical model of the mechanical behavior of the membrane mirror construction coupled to a Monte Carlo ray-tracing simulation is formulated and applied for design and optimization and for elucidating the influence of manufacturing and operational parameter variations on the radiative flux distribution. It is found that the parabolic shape can be well approximated with four stacked membranes that generate an arc-spline of four tangentially adjacent circular arcs. A 45-m-long 9-m-aperture full-scale prototype concentrator was fabricated and experimentation was carried out to validate the simulation model. Highest measured peak solar radiative flux concentration was 18.9, corresponding to 39% of the theoretical maximum value for an ideal parabolic trough concentrator.

Copyright © 2011 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

(a) Concrete support structure and foundation, receiver posts; (b) inflated air tube, formed by ETFE-membrane and fiberglass fabric, containing pneumatically spanned mirror membranes and receiver; (c) photograph of the 45-m-long, 10-m-wide prototype concentrator

Grahic Jump Location
Figure 2

Geometry of the arc-spline (black solid curve) with n=4 arcs per wing, running from P1 to P5. The profile of support membrane j (j=2,3,...,n, black dashed curves) consists of a circular section Sj running from inner clamping point P1,j to node Pi=j, and a tangentially adjacent section running from Pi=j to outer clamping point P5, which is coincident with the arc-spline profile. Membrane pressures are indicated by p1 to p5.

Grahic Jump Location
Figure 3

Best-fit arc-spline profile (solid line), suspended sections Sj of support membrane profiles (dashed lines) for n=4; circles indicate clamping points (prescribed) and arc boundaries (nodes). The baseline concentrator dimensions and the arc-spline/support membrane parameters are listed in Table 1.

Grahic Jump Location
Figure 4

z-Coordinate difference (dashed line) and slope angle α-difference (solid line) between arc-spline (AS) with n=4 arcs (Fig. 3) and reference parabola. The arc-spline parameters in Table 1 apply.

Grahic Jump Location
Figure 5

Force balance for arc i, fixed at nodes Pi and Pi+1, subjected to pressure difference Δparc,i>0

Grahic Jump Location
Figure 6

Distribution of the solar concentration ratio at the focal plane for optimized arc-spline concentrators with n= 2–5 arcs per mirror wing and for an ideal parabolic concentrator; distributions are symmetric to the ordinate of the graph

Grahic Jump Location
Figure 7

Average solar concentration ratio (a) and intercept factor (b) as functions of the dimensionless target width wtarget/f for optimized arc-spline concentrators with n= 2–5 arcs per mirror wing, and for an ideal parabolic concentrator

Grahic Jump Location
Figure 8

rms-z-coordinate difference Δzrms and rms-slope angle difference Δαrms of the optimized arc-spline profile compared to the reference parabola, as a function of the number of arcs n in the arc-spline

Grahic Jump Location
Figure 9

Distribution of the solar concentration ratio at the focal plane for various membrane pressure deviations δp applied to pidesign (given in Table 1); δp=0 corresponds to the undistorted mirror shape

Grahic Jump Location
Figure 10

Average solar concentration ratio (a) and intercept factor (b) as functions of the dimensionless target width wtarget/f for various membrane pressure deviations δp applied to pidesign (given in Table 1); δp=0 corresponds to the undistorted mirror shape

Grahic Jump Location
Figure 11

Distribution of the solar concentration ratio at the focal plane for various membrane width deviations Δw=-5÷-1mm from the design value wmembranereference,design; Δw=0 corresponds to the undistorted mirror shape; design pressures pidesign listed in Table 1 are applied

Grahic Jump Location
Figure 12

Average solar concentration ratio (a) and intercept factor (b) as functions of the dimensionless target width wtarget/f for various membrane width deviations Δw=-5÷-1mm from the design value wmembranereference,design; Δw=0 corresponds to the undistorted mirror shape; design pressures pidesign listed in Table 1 are applied

Grahic Jump Location
Figure 13

Membrane pressures picorrected to be applied in case that the width wmembranereference of each mirror membrane deviates by Δw=-5÷1mm from the design value wmembranereference,design; p5corrected = 0

Grahic Jump Location
Figure 14

Distribution of the solar concentration ratio at the focal plane for various membrane width deviations Δw=2÷5mm from the design value wmembranereference,design; Δw=0 corresponds to the undistorted mirror shape; optimized pressures pi listed in Table 7 are applied

Grahic Jump Location
Figure 15

Average solar concentration ratio (a) and intercept factor (b) as functions of the dimensionless target width wtarget/f for various membrane width deviations Δw=2÷5mm from the design value wmembranereference,design; Δw=0 corresponds to the undistorted mirror shape; optimized pressures pi listed in Table 7 are applied

Grahic Jump Location
Figure 16

Forces (black) and moments (gray) acting on the lateral longitudinal girders with equilateral triangular hollow profile. FETFE: force exerted by ETFE-membrane, Fgravitation: gravitational force, Fmembrane,total: force exerted by all mirror membranes, Ffiberglass: force exerted by fiberglass fabric, Fresultant: resultant force, Mbending: bending moment; x2,x3: principal directions of girder profile; βinclination: concentrator inclination; G: center of gravity.

Grahic Jump Location
Figure 17

Deflection of lateral and central longitudinal girders as a function of position along the girder for βinclination=30∘; girder parameters of Table 8 are used

Grahic Jump Location
Figure 18

(a) Displacement vector umax=u(y=lgirder/2) of lateral longitudinal girders as a function of concentrator inclination βinclination; (b) maximum girder displacements as a function of girder length lgirder for βinclination = 30°; girder parameters of Table 8 are used

Grahic Jump Location
Figure 19

Distribution of the solar concentration ratio at the focal plane for deflections of the longitudinal girders by umax at βinclination=30∘; the parameter is the girder length lgirder=8÷12 m; girder parameters of Table 8 are used

Grahic Jump Location
Figure 20

Average solar concentration ratio (a) and intercept factor (b) as functions of the dimensionless target width wtarget/f for deflections of the longitudinal girder by umax at βinclination=30∘; the parameter is the girder length lgirder=8÷12 m; girder parameters of Table 8 are used

Grahic Jump Location
Figure 21

Concentrator model validation: measured (black solid curves) versus simulated (black dashed curves) distributions of the solar concentration ratio on the target; for comparison the distributions for an ideal arc-spline concentrator with 4 arcs per mirror wing (gray solid curves) and for an ideal parabolic concentrator (gray dashed curves) are shown; VETFE=1 and ρmirror=1 for the ideal cases

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In