Experimenting with the Sketchup_Light Ray Reflection Simulator Plugin

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This page shows off some experiments done with the Sketchup Light Ray Reflection Simulator Plugin. The reason this plugin was written was so that both myself, and hopefully others too, can gain a better understanding of how light rays behave as they reflect from a surface.

If you have an interest in solar energy and like to tinker, this plugin could be a big help for when you design your next solar project. Hopefully, some of the experiments featured on this page might just give you some ideas for what that project might be.

Now, on to the experiments.

A Parabolic Trough

Here is a quick test I did with a drawing of a parabolic trough just to start things off.

In this picture, you can see how the light does indeed concentrate to a single point at the bottom of the trough just as it is supposed to. Note: The plugin was set up to only do one reflection here, which is why some of the light rays are traveling through the “mirror” surface.

A Parabolic Solar Greenhouse

I once read about a parabolic solar greenhouse in the Solar Greenhouse Book. (Here is a picture of it on flickr too) It’s a pretty neat idea. Basically, the back of the greenhouse has a parabolic shape to focus the sun’s light on a tank of water. The water stores the heat given from the sun and then releases it when the temperature drops.

To get a better idea of how this might work, I drew a simple model in Sketchup and ran the light simulation plugin on it.

Here you can see the “rays of light” lined up to simulate the sun’s rays.

Here’s what it looks like as the sun’s rays reflect off of the back. You can see that they do indeed focus on the tank of water.

This is, or course, just a quick example. I have no idea what parabolic shape is actually the best, and it would probably take a fair amount of effort to figure out since the sun’s light can come from so many different angles. In principle though, it looks like the idea works.

My Solar Cooker

I decided to do a quick test on my solar cooker to see how well it collected the light from the sun.

I picture of the “light rays” lined up with it.

You may have to use your imagination a little bit here, but this how the inside of the cooker looks when viewing it from the top. From this picture, it looks like I should try and keep the pot of food close to the front since the light seems to be more concentrated there.

A Fresnel Solar Cooker

If you have ever tried to make a parabolic solar concentrator before, you no doubt understand just how difficult they are to build. It is for this reason that I really like the solar cooker on this site http://www.sunspot.org.uk/ed/. It is (sort of) parabolic in nature while also being a lot simpler to make.

Following the plans at the link, I was able to quickly put together this Sketchup model. Now, I can test to see how well it concentrates the light.

Here, you can see that it does indeed do a good job of focusing the light. Instead of concentrating the light to a small point like with a parabolic dish though, the light is concentrated over, relatively speaking, a much larger area, roughly the size of the bottom of a pot.

Although a small very focused and very hot point of light may be desirable in some applications, much of the time it is unnecessary and ultimately just more dangerous.

Here is another experiment with the “rays of the sun” angled as though an hour of time had passed without the solar cooker being realigned to face the sun.

Without being updated to match the sun, it looks like the cooking pot (small oval at the top of the picture) would be fully outside of the concentrated rays within the hour. In fact the site where this design comes from says that the position of the solar cooker should be updated every 10 minutes.

What Happens when a Ray of Light Enters a Sphere?

Although not really related to solar energy, here is an experiment I did with the plugin to see how well it would do with multiple reflections.

I first drew a sphere and then a line to represent a ray of light, which is what you see in the picture below.

Here is a picture of what happened after the plugin was run. It’s kind of neat to see how the light just keeps bouncing around and around indefinitely. Of course, in the real world, the light would eventually be absorbed since no material is a perfect reflector, but it is still cool nonetheless.

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