Sun projector

[lilimike]

I have this idea which I think can work. I have not started working on this project yet, I am still in the process of browsing but not finding much. I would like to get your opinions on this.

I have a few bushes in my yard that are under two large trees. At the beginning of the season (I am in Quebec so we start from scratch in Spring) all is good until the leaves grow on the trees at the point where it hides the sun from the bushes. The latter are not giving me as much flowers as they should.

My idea is to track the sun from a location where I have no shade on my yard and then scan the bushes using small mirrors with the reflection of the sun in the same way as a laser show and/or like an old CRT tube. The scanning idea is to reduce the size of the mirrors. I understand the bushes would only get a % of sunlight but a % is better than nothing and might be enough.

I foresee this project in 3 parts.

1 – Tracking the sun location based on a position on the earth, I have seen some code (Arduino) that does that so this is not an issue.

2 - I would then have to figure out how to redirect the reflection to a specific place in my yard with the option of sizing x and y axis. This part looks more complicated to me but in the worst case, I can manually change the position and log the data based on each day of the year for the first year.

3 – Since I’d be working with the sun and nothing would be needed if the sun is not out, I would implement solar as the power for this project (no problem there).

Any thoughts?

 

[Lightium]

Why don't you just hang arc-lamps under the tree and above the bushes?

 

[lilimike]

I have no power at that location, I could burry a 75 feet cable but the project I mentioned sounds interesting to me.

 

[Nigel Goodwin]

Why don't you just hang arc-lamps under the tree and above the bushes?

Because of the HUGE expense of running them?

 

[crutschow]

The amount of sun reflected is obviously proportional to the mirror size.
How big a mirror do you plan on using?

 

[lilimike]

This is the base of my idea, I want to reduce the mirror size down to about one inch square and have the mirror move quickly using a couple of step motors (or servos) and project the sun reflection on a preselected area so it will scan from left to right (x) with multiple lines from up to down (y) both x and y will be adjustable to select the size of the projected area.

 

[crutschow]

I want to reduce the mirror size down to about one inch square

That's a really small mirror.
How big an area do you want to illuminate with that mirror?

You do realize that the average light intensity will be reduced by the ratio of the mirror area to the area illuminated.
So for example, if the bush is say 2' x 2', then the area is 4 sq. ft. or 576 sq. in., so the sunlight would be reduced to <0.2% of the original sunlight intensity, likely not enough to much aid the bush's growth.

 

[Nigel Goodwin]

This is the base of my idea, I want to reduce the mirror size down to about one inch square and have the mirror move quickly using a couple of step motors (or servos) and project the sun reflection on a preselected area so it will scan from left to right (x) with multiple lines from up to down (y) both x and y will be adjustable to select the size of the projected area.

That will supply almost no light at all, it would be a complete waste of time - as 'crutschow' suggested.

If you're going to do it, then you need BIG mirrors, to permanently provide sunlight for the bushes.

Best options, severely trim or remove the trees, or just cut the bushes down

 

[lilimike]

if the bush is say 2' x 2', then the area is 4 sq. ft. or 576 sq. in., so the sunlight would be reduced to <0.2% of the original sunlight intensity

I could be wrong but my thinking is if I reflect the sun from a 1 sq. in. mirror on a 576 sq. in. surface and the scan of the full surface takes 1 second, the bush will have received 1/576 of the sunlight during that second and yes that is really small but if I increase the scan frequency, it will increase the sunlight reflected on that surface. The question is, how fast can I scan the surface? perhaps step motors or servos are not fast enough. I would think increasing the scan frequency by about 200 times so in this example, the surface would get over 30% of the sun. Does this makes sense? or I am in the bushes...

 

[Nigel Goodwin]

I could be wrong but my thinking is if I reflect the sun from a 1 sq. in. mirror on a 576 sq. in. surface and the scan of the full surface takes 1 second, the bush will have received 1/576 of the sunlight during that second and yes that is really small but if I increase the scan frequency, it will increase the sunlight reflected on that surface. The question is, how fast can I scan the surface? perhaps step motors or servos are not fast enough. I would think increasing the scan frequency by about 200 times so in this example, the surface would get over 30% of the sun. Does this makes sense? or I am in the bushes...

No it makes no sense, it still only receives 1/576 of the sunlight no matter how fast you move it. It's a completely impractical and pointless exercise, and will have no effect on the bushes.

 

[Pommie]

Agree with Nigel completely, absolutely pointless. Only bigger mirrors make any sense.

Mike.

 

[lilimike]

Would adding a concave lens in front of the mirror have the same effect as making the mirror bigger?

EDIT: or simply using a slightly concave mirror?

 

[Nigel Goodwin]

Would adding a concave lens in front of the mirror have the same effect as making the mirror bigger?

EDIT: or simply using a slightly concave mirror?

Assuming you mean a large mirror, and not a pointless tiny one.

But assuming you actually mean focusing the sun onto a tiny mirror, via a huge lens - then you're creating a death ray - assuming the tiny mirror doesn't melt?, you will set your bushes on fire, and burn anyone who walks in the path.

Have a look here:

 

[lilimike]

Yes I was just browsing and I realize the focal point is an issue with concave lenses or mirrors.
I think I will do some testing by replacing the bushes by a solar panel, scan the sun's reflection at different frequencies and look at the output voltages. Not that I don't trust your answers but my level of curiosity is closely related to the number of hours I get of sleep.

 

[audioguru]

Simply cut down the trees. They make too much shade, pollen, and millions of seeds and leaves to clean up. Here in Ontario you need a city permit to cut down your tree, only one tree each year. You must promise to plant a replacement tree somewhere in your yard. The permit says nothing about keeping the replacement tree alive.

 

[lilimike]

Simply cut down the trees

Cutting the trees is not an option. It took me long enough to get my yard pretty. Worst case I will replace the bushes with some that grows in the shade but not until I've tested reflecting the sun.

 

[crutschow]

Would adding a concave lens in front of the mirror have the same effect as making the mirror bigger?

EDIT: or simply using a slightly concave mirror?

None of that makes any difference.
It's the simple physics of energy.
The amount of energy reflected is proportional only to the amount of energy intercepted from the sun and that is determined solely by the size of the mirror.
You can't increase the energy reflected by how fast you scan it or its shape, or adding a lens, as that would be multiplying the energy, which is not possible with a passive device.
It's simply the size of the mirror.

 

[BR-549]

I believe some of your idea has merit. Although I would abandon the scanning part. And replace it with one scan per day. A solar panel tracking device. And keep the focal point on bush. The mirror does not need to be large. Just large enough to light the bush and a little air and soil around it. I believe many posters here would be surprised at the results. As you will be. A very worthwhile experiment. A small non moving solar panel and battery can power it. Even in Quebec.

 

[crutschow]

I believe many posters here would be surprised at the results.

Why?
The whole point of most of the replies was that a small mirror won't work, thus you would need a larger mirror for the scheme to be practical.

 

[BR-549]

I think that you would be surprised at the size of the mirror needed.