Here is a page answering that question.
In short, I did it because it was fun to do.
How did you build it?
I wrote some software to help me compute the angles of the mirrors. I cut wood
blocks to these angles, mounted the blocks on the wood frame, and then glued
mirrors on the blocks.
How does it work?
Here is a page explaining some of the science behind the Solar Death Ray.
What about mounting a
magnifying glass in the focus?
I don't think this would do anything. When
using a magnifying glass (or similar lens, like a
Fresnel lens), every point on the lens is
associated with a specific direction of
incoming light (upper image). However this is
not the situation in the focus of the Solar
Death Ray, because all of the light from the
focus is reflected off of mirrors at different
angles (lower image). Because of this, a
conventional lens would not help concentrate
the light, and would most likely dilute
("de-concentrate") the sunlight. There are
ways to minimize the effect, but the Solar
Death Ray would have to be explicitly
designed to use a magnifying glass or other
secondary concentrator.
MythBusters is a show on the Discovery Channel, where some talented people
test various myths and urban legends. During episode 16, they tackled the
question "Did the Greek scientist Archimedes set fire to a Roman fleet of ships
using only mirrors and sunlight?" They built a very large but eerily similar cousin
of the Solar Death Ray and tried to set a chunk of a recreated Roman boat on
fire. Long story short: they couldn't get it to work. And yet my version does...
Why? Well, for one thing, I'm trying to focus light on an object a few feet from the
mirrors, and they were trying to focus on an object dozens of feet away. The
farther away the target, the more precisely aligned your mirrors have to be. I know
my mirrors have to be within about +- 0.5 degrees to properly focus light on the
target, and so the MythBusters had to have mirrors much more precisely aligned. I
don't know how they aligned their mirrors, but I suspect that was the problem. In
addition, I would have used a concentrator design much different from both their
version and the Solar Death Ray. Still, I agree with their conclusion: It would be
very difficult, but not impossible, for Archimedes to have pulled this off, mainly
because of the manufacturing tolerances involved. But if Archimedes had the
resources...
Did MythBusters copy your design? Did you copy their design?
No, I built both of my Solar Death Rays (Mark 1 and Mark 2) before this episode
aired, so I couldn't have copied their design. And I didn't start the website until
after the episode aired, so they couldn't have copied my design. It's probably just
a coincidence (great minds think alike).
Isn't it 113 suns (112 reflections and 1 original sun)?
Uh, yeah, that's a good point.
What about hooking it up to a Sterling engine?
Yeah, that would be cool. The thermodynamic efficiency should be decent
(maybe over 60%) assuming I can reject heat near room temperature (about 300
K). I haven't seen a kilowatt-class Sterling engine for sale, but that might be
because the guy who makes them hasn't seen a kilowatt-class solar concentrator
for sale.
What about commercial/practical applications?
You could use something like the Solar Death Ray for heating and electrical
power generation. There's researchers out there looking into this kind of stuff,
both in the U.S.A. and around the world.
If you like space stuff, check this out:
Solar concentrator/photovoltaics (solar panels) in space
Solar thermal spacecraft propulsion
BIG Solar Concentrators:
Odeillo Solar Furnace (I'm not sure if this is the official page)
PSA (I'm not sure if this is the official page, either)
Solar Two
And so on...