Edmonds box - laser cut panels simulation in SolidWorks

Let's research how the 1992 Edmonds [1] light deflection LCP experiments can be simulated in the CFD software.

Mikhail Tuzovskiy, August 11, 2021

Edmonds Box SolidWorks model

Introduction

Laser cat panels are used to deflect incident light to increase the illumination of the work surfaces deep in a room. LCP are applied in light pipes, light collectors etc. Edmonds [1] provided a means to calculate an optimum LCP configuration to maximize the fraction of deflected light. He also performed an experiments we will study below.

Edmonds box experiment

Scale model room with luxmeter and the adjustable tilt LCP. Measurements under clear sky with sun at 62° elevation.

Edmonds box experiment setup

Edmonds box experiment dimensions

Laser cut deflecting panels were mounted in the window aperture of the model room and tilted so that the light was deflected across the ceiling of the room. The performance of an LCP when tilted at 25° was compared with the performance of an LCP in vertical orientation and with a vertical clear acrylic panel.

LCP configuration: thickness 6mm, distance between cuts 2 mm, cut width 0.2mm, distance to width ratio D/W = 2/6 = 0.33. Refractive index 1.491. Transmissibility 92%.

Results

The measurements showed the very substantial improvement in work surface illumination (300% to 400%) may be achieved with the tilted LCP.

Edmonds box experiment results

CFD Simulation exercise

Now we run the same experiment in the SolidWorks software and compare results.

Here is the box floor solar flux distribution for the 3 cases:

Vertical window, Vertical LCP, Tilted LCP

Vertical window floor flux

LCP window floor flux

Tilted LCP floor flux

Solar flux deflected deeper in the box floor with LCP and Tilted LCP.

Next is the box ceiling solar flux distribution for the 3 cases:

Vertical window ceiling flux

LCP window ceiling flux

Tilted LCP ceiling flux

No solar flux is deflected to the ceiling for the vertical window as expected. Tilted LCP deflects light deeper into the box ceiling.

And, box rear wall (opposite to the window) solar flux distribution for the 3 cases:

Vertical window rear wall flux

LCP window rear wall flux

Tilted LCP rear wall flux

Tilted LCP delivers more light to the rear wall compared to the other cases.

Finally, chart with the solar flux distribution vs depth from the window into the box:

Solar flux distribution per distance

Beyond 0.3 meters, LCP and Tilted LCP deflect more light into the box floor.

Converted to log scale to compare with the Edmonds result charts:

Solar flux distribution per distance on semi-log plot

The solar flux is ~10 times higher for the LCP cases beyond the length 0.6 meters. This supports the case for the deeper light deflection with the laser cut panels.

Note that Edmonds were measuring illumination intensity in kilolux, however SolidWorks allows to calculate the solar flux in watts/m2.

Conclusion

SolidWorks CFD software is capable to capture the effect of light deflection by the laser cut panels, allowing LCP design and optimization for the building science applications.

It is recommended to complete the same simulation exercise with the software which handles illumination.

References

Edmonds, Ian R. "Performance of laser cut light deflecting panels in daylighting applications." Solar Energy Materials and Solar Cells29.1 (1993): 1-26.
http://www.solartran.com.au/lasercutpanel.htm