There were a lot of
choices that I made while designing my box. Initially, I thought about two ways
that I could go about heating the water that I was supposed to heat, which
would be to directly get sunlight to hit the water by reflecting it at it or
heating up the air around it as effectively as possible. I decided to go with
the latter to make calculations easier, as it would require incredibly precise
calculations to achieve something like that, and even slight movements of the
sun could throw everything off.
Another
one of the things that I thought about was to make the entire thing tilted,
which allowed for the contraption to be better exposed to the sun, as ultimately,
I wanted as much of the contraption to be directly exposed to the sun. I went
outside to see how much the sun travels during the day (before school to right
after school) to decide how much to tilt the box, and I got an angle around 30
degrees to be ideal for the tilt.
For the
actual reflective surfaces, I researched strategies that had been done previously
and saw a lot that were either round or 4 rectangular panels, so I decided to
use trapezoid panels to increase the surface area. My reasoning for this was
that even if it hit the corners, due to the funnel shape of the reflective
surfaces, the light would still be reflected somewhere into the box, which
achieves the purpose of heating up the surroundings, as I decided earlier.
I also
noticed that when the tinfoil crumples, there are some areas of shade and other
areas that reflect better. I realized that if the tinfoil crumpled, it would
reflect less sunlight toward the center, which would lead to less heating. What
I decided to do to ensure that this wasn’t a problem was to adhere Duct Tape to
the back of the pieces of tinfoil, so that it would prevent the foil from being
able to crumple on the areas which area meant to
reflect. This idea worked well, and I saw that there was much better reflection
even while I was in the process of installing it.
I had a
very unorthodox approach as I used a wooden popsicle stick frame rather than
the carboard ones that everyone had been building, and my reasoning for that
was structural stability. Each of the panels was a lot bigger than the others
that I had seen, so I wanted to ensure that each of them would be upright and
not collapse, so I decided the frame would be the best way to go. This also
allowed the tinfoil to be pulled taught, to make it better reflective.
Trapping
heat was incredibly important, so I did a few things to insulate the box.
Firstly, I covered the inside and outside of the box completely in black duct
tape to reduce its albedo, as I know black traps more heat. I then got a bigger
box and placed the assembly which was 8 x 10 (same size as the plexiglass to
make it as airtight as possible) inside it and insulated it by stuffing paper
in the margins and then covered the sides of this box with duct tape as well.
The reflective
surface and plexiglass were easily removable as I added securing tabs to
prevent the contraption from moving when tilted but comes off easily so that I will
be able to replace the thermometer with ease. This was something small but had
a decent impact as it allowed me to quickly test and tweak as I worked.
I also did some research
to decide on the material to make these surfaces out of, as I wanted to see if
reflective blankets or reflective tape would be a better solution than the
tinfoil, but I saw no drastic benefit and realized that it might pose a bigger
overhead. I also thought about the material of the clear window. I investigated
any benefit from using a material other than plexiglass, which I thought brought
me to one-way mirrors, but obtaining one and cutting it to perfect size was
something that I thought was not worth the limited benefit it gave me.