0
Research Papers

An Experimental Study of Ammonia Receiver Geometries for Dish Concentrators

[+] Author and Article Information
Rebecca Dunn

Solar Thermal Group,  Australian National University (ANU), Research School of Engineering, Building 31, North Road, Canberra ACT 0200, Australiarebecca.dunn@anu.edu.au

Keith Lovegrove

 IT Power Australia, PO Box 6127, O’Connor ACT 2602, Australia

Greg Burgess, John Pye

Solar Thermal Group,  Australian National University (ANU), Research School of Engineering, Building 31, North Road, Canberra ACT 0200, Australia

J. Sol. Energy Eng 134(4), 041007 (Aug 06, 2012) (9 pages) doi:10.1115/1.4006891 History: Received January 27, 2011; Revised April 26, 2012; Published August 06, 2012; Online August 06, 2012

This paper presents experimental evaluation of ammonia receiver geometries with a 9 m2 dish concentrator. The experiments involved varying the geometric arrangement of reactor tubes in a thermochemical reactor built from a series of tubes arranged in a conical shape inside a cavity receiver. Differences in conical arrangement were found to affect the efficiency of energy conversion. The solar-to-chemical efficiency gain obtained by varying the receiver geometry was up to 7% absolute. From this, it is apparent that geometric optimizations are worth pursuing since the resulting efficiency gains are achieved with no increase in costs of manufacture for receivers. The experimental results and methodology can be used when developing receivers for larger dish concentrators, such as the second generation 500 m2 dish concentrator developed at the Australian National University.

Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Energy storage using dissociated ammonia (nitrogen and hydrogen gas) as the storage medium at ambient temperature

Grahic Jump Location
Figure 2

Left: The prototype second generation 500 m2 dish on the ANU campus (SG4). Right: ANU’s 20 m2 dish masked to a 50 deg rim angle and 9 m2 area

Grahic Jump Location
Figure 3

Prototype solar dissociation receiver/reactor construction. Left: cross-section. Right: ammonia receiver for the 20 m2 dish (Fig. 2) with a 17.5 deg half cone angle (insulation removed)

Grahic Jump Location
Figure 4

The OptiCAD model of the dish masked to 9 m2 and the receiver, as used for ray-tracing

Grahic Jump Location
Figure 5

Flux maps produced from an experiment and an OptiCAD ray-trace of the 9 m2 dish masked as shown in Fig. 2

Grahic Jump Location
Figure 6

Receiver geometries modeled in OptiCAD. From top left: the original prototype receiver—a frustum of reactor tubes with angle 17.5 deg to the horizontal; a frustum with angle 7.5 deg to the horizontal; reactor tubes arranged in a cylinder with radius 45 mm (no gaps between tubes); a 77 mm radius cylinder; and a 108 mm radius cylinder

Grahic Jump Location
Figure 7

Flux profiles obtained by ray-tracing for five receiver geometries. Irradiance values are an average around the outer circumference of the tubes.

Grahic Jump Location
Figure 8

Three receiver configurations. Top: receiver with the original 17.5 deg half cone angle (all insulation removed). Middle: receiver with a 7.5 deg half cone angle (viewed looking in to the aperture with the front shield removed). The indents in the wall insulation indicate the position of the tubes in the frustum with a 17.5 deg half cone angle. Bottom: receiver in a frustum with base radius 77 mm (front shield removed).

Grahic Jump Location
Figure 9

Solar-to-chemical efficiencies of a frustum receiver with 17.5 deg half angle at various flow rates, with a linear fit for flow rates in the optimal range of 1.0 g/s–1.25 g/s

Grahic Jump Location
Figure 10

Solar-to-chemical efficiencies of a frustum receiver with 7.5 deg half angle at various flow rates, with a linear fit for the optimal flow rates of 1.0 g/s and 1.25 g/s

Grahic Jump Location
Figure 11

Solar-to-chemical efficiencies of a frustum receiver with 77 mm radius base at various flow rates

Grahic Jump Location
Figure 12

Solar-to-chemical efficiencies for the three receiver geometries in their optimal flow rate ranges. The crosses for the 7.5 deg half cone (upper curve) and triangles for the 17.5 deg half cone (lower curve) show results at a flow rate of 1.25 g/s only. The diamonds (7.5 deg half cone, upper curve) and squares (17.5 deg half cone, lower curve) group together results for 1.0 and 1.25 g/s.

Grahic Jump Location
Figure 13

The solar dissociation experimental system and associated losses. The arrows pointing left from the system (red arrows) comprise the receiver losses—due to heat losses and reflection from the cavity. Accounting only for these losses gives the receiver efficiency. Adding these to the flux spillage, dish reflectivity, tracking error and heat exchanger losses gives all the losses in the system, which are accounted for in the solar-to-chemical efficiency. (Adapted from Paitoonsurikarn [19].)

Grahic Jump Location
Figure 14

Percentage of flux captured by the cavity aperture of radius 0.0975 m. Left: 99.1% for the OptiCAD ray-trace. Right: 93.4% for the experimental flux map described in Sec. 2.

Grahic Jump Location
Figure 15

Dissociation rates (left) and average tube temperatures (right) for the three receiver geometries in their optimal flow rate ranges

Grahic Jump Location
Figure 16

Selected temperature profiles for reactor tube number 7 for solar altitudes ranging from 35.5 deg to 67.6 deg during an experiment on Feb. 10, 2010. The distance 0 cm is closest to the aperture (segment 7 in Fig. 1).

Grahic Jump Location
Figure 17

A comparison of experimental receiver efficiencies and solar-to-chemical efficiencies from an experiment with 17.5 deg half cone and mass flow rate of 1.25 g/s on Feb. 10, 2010

Grahic Jump Location
Figure 18

An energy balance: calculated energy losses and their sum compared with experimental receiver losses from an experiment with 17.5 deg half cone and mass flow rate of 1.25 g/s on Feb. 10, 2010

Grahic Jump Location
Figure 19

Division of the receiver cavity into seven segments, with 1–4 representing the reactor tubes and cavity walls, 5 the manifold, 6 the front shield, and 7 the aperture

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