0
Research Papers

Investigation of Prismatic Daylight Collectors With Different Apexes

[+] Author and Article Information
Allen Jong-Woei Whang

e-mail: whang@mail.ntust.edu.tw

Chia-Min Lin

e-mail: d10002305@mail.ntust.edu.tw
National Taiwan University of
Science and Technology,
T2-507, 43, Sec. 4, Keelung Rd.,
Taipei 10607, Taiwan

Shih-Chuan Yeh

De Lin Institute of Technology,
No. 1, Ln. 380, Qingyun Rd.,
Tucheng Dist,
New Taipei City 236, Taiwan
e-mail: yehsc@dlit.edu.tw

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received January 3, 2012; final manuscript received July 2, 2012; published online September 10, 2012. Assoc. Editor: Akiba Segal.

J. Sol. Energy Eng 135(1), 011015 (Sep 10, 2012) (10 pages) Paper No: SOL-12-1001; doi: 10.1115/1.4007301 History: Received January 03, 2012; Revised July 02, 2012

Prismatic elements are widely used in daylight illumination systems. The characteristics of the light that emerges from the surface of a right-angled prism vary with the apex of the prism and the incident angle of the sunshine illuminating the surface of the prismatic daylight collector. This paper investigates the effect of the apex angle of a right-angled prismatic collector on the performance of the collector using a matrix ray-tracing model and the edge principle. It was found that the majority of the light emerges from the hypotenuse of the right-angled prism when sunshine is incident on the surface of the prismatic daylight collector; furthermore, the flux of the light emerging from the hypotenuse that directs illuminating space decreases as the apex of the right-angled prism is increased. The intensity distribution of the majority of the light emerging from the hypotenuse of a right-angled prism can be used to guide the design of natural light illumination systems and enhance their performance. The percentage of light emerging from the hypotenuse decreases with the number of prismatic elements because the relative area of the emerging light that reaches the adjacent prism increases with the number of prismatic elements. The analysis of the relative area of the hypotenuse, where the emerging light that reaches the adjacent prism according to the edge ray principle shows that the total area is constant when the number of prismatic elements is greater than 10; an economical prismatic daylight collector can be realized with less material due to the larger number of smaller prisms with the same apex.

FIGURES IN THIS ARTICLE
<>
Copyright © 2012 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Fig. 1

(a) An illustration of the interfaces of the media, the plane of incidence, the unit vectors of the incident ray, reflective ray, and refracted ray, and the angles δir and δit. (b) The definition of the polar angle of a ray.

Grahic Jump Location
Fig. 2

Illustrations of sunshine illuminating S1 of the prismatic daylight collector: (a) the parallel light beam is divided into two parts to strike surfaces S2 and S3 of the prism for an incident polar angle of 180 deg < θi < 270 deg, and (b) all of the parallel light beam strikes surface S2 for an incident polar angle of 270 deg ≦ θi < 360 deg

Grahic Jump Location
Fig. 3

(a) The light emerging from S2 illuminates the space and re-illuminates S3 of the adjacent prism of the prismatic daylight collector for an incident polar angle of 270 deg ≦ θi < 360 deg, (b) the illustration of a simulated model

Grahic Jump Location
Fig. 4

(a) Percentage of the area that transmitted light would strike to the hypotenuse, (b) the minimum incident polar angle that transmitted light of S1 would also transmit the hypotenuse, (c) the normalized intensity for transmitted light of S1 and emerged from S2 for different apex angles: αA = 20 deg, αA = 30 deg, and αA = 40 deg

Grahic Jump Location
Fig. 5

The polar angle of the transmitted ray of the light emerging from S2 for daylight illuminating prismatic daylight collectors with apex angles of αA = 20 deg, αA = 30 deg, and αA = 40 deg

Grahic Jump Location
Fig. 6

The percentage of light emerging from S2 that would strike surface S3 of the adjacent prism for daylight illuminating prismatic daylight collectors with apex angles of αA = 20 deg, αA = 30 deg, and αA = 40 deg

Grahic Jump Location
Fig. 7

The relative intensity of internal reflected light from S2 and the transmitted light of S1: (a) the reflective light that is incident on S1, (b) the reflective light that is incident on S3

Grahic Jump Location
Fig. 8

The polar angle of the internal reflective ray at S2 relative to the incident polar angle for daylight illuminating the prisms

Grahic Jump Location
Fig. 9

The polar angle of the transmitted light from S3

Grahic Jump Location
Fig. 10

The intensity distribution of light transmitted through S1 that strikes S2 for sunshine illuminating prisms with apex angles of (a) αA = 20 deg, (b) αA = 30 deg, and (c) αA = 40 deg

Grahic Jump Location
Fig. 11

The normalized intensity that illuminates space (S) and the adjacent prism (P) due to light emerging from the hypotenuse (S2) when sunshine illuminates the surface of prisms with apex angles of α = 20 deg, 30 deg, and 40 deg

Grahic Jump Location
Fig. 12

(a) The normalized intensity of spatial illumination. (b) The normalized intensity of light illuminating the adjacent prism that emerged from S2 for apex angles of the right-angle prism α = 20 deg, 30 deg, and 40 deg.

Grahic Jump Location
Fig. 13

(a) The area of space that the emerging light illuminates when sunshine initially illuminates S1 of prismatic arrays with different elements at θi = 325 deg. (b) The area of space that the light emerging from S2 illuminates relative to the area of S1 that is initially illuminated for prismatic array with 20 elements at 270 deg ≦ θi < 360 deg.

Grahic Jump Location
Fig. 14

The intensities distribution of light emerging from S2 for sunshine illuminating the surface of prismatic collectors with apex angles of αA = 20 deg, αA = 30 deg, and αA = 40 deg

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