This document summarizes a DIY project to use recycled pop cans and passive solar heating to warm a cold bedroom. Key points: - The bedroom gets too cold in the daytime due to its distance from the central furnace. - A solar collector chimney system was designed using pop cans as the absorber surface and independent chimneys to transfer heat into the room. - Two iterations were tested - the first with bottom-vented cans did not have enough airflow, while cutting out the bottoms improved airflow and heat transfer. - Initial tests showed a 40 degree rise in temperature within the chimneys and some warming of the room.

1. Solar – just for fun
• The sole purpose of this project is to experiment
with possibilities for solar space heating.
• Unlike a normal experiment, I knew what I
wanted to do so I looked for a problem that
would fit the solution.
• The process is documented in a classroom format
as an easy way to communicate it to others that
may be interested.
• A special thank you to my wife and daughter for
tolerating pop cans, power tools, and spray paint
in the house.

2. AET290 Unit 1 Slide 12
A DIY Response

3. Identify the problem
• Master Bedroom is too cold during the day
• Temp is ok at night
• Bedroom is at the farthest point from the
central furnace
• The rest of the house is OK during the day

4. Brainstorm
• Space heater – too noisy and costly
• Turn up the thermostat – rest of the house
would be too warm
• The room has south facing window – develop
a solar collector to heat the room

5. Design
• Adapt a 2nd generation hot box to fit the
window
• Pop can style collector
• Use the cans as independent chimneys
• Passive air flow
• Old window is usually cold, anything is an
improvement

6. Safety first !!!
• Safety glasses
• Ear protection
• Leather gloves

7. Build – 1st round
The first step was to puncture holes
in the bottom of the cans. The logic
was to let the air through slowly in
an attempt to collect as much heat
as possible from the cans

8. Assembly
No alterations were made to the can
tops. The cans were glued together
with hot glue and then painted black

9. The chimneys
• Each chimney would
consist of 14 cans, each
can vented though the
bottoms.
• The bottom can has a
hole in the side to allow
fresh air intake

10. Test and Evaluate
• 8 chimneys were assembled in this fashion
• The chimneys were placed on the window sill
between the curtain and the glass
• Δt was impressive, each chimney averaged a
40° rise in temp and they peaked at 60°
• Airflow was not measured so BTU calculations
were not possible
• Very little air flowed through the chimneys
and they began to self destruct at 135°

11. Qualitative results
• The room was -4° relative to the central
thermostat
• With the chimneys the room is +4°
• The room is 15x15x10’
• I consider this performance OK, I expected
better

12. Redesign – improve air flow
• The bottoms of the cans
were cut out completely
using a 1 5/8” hole saw
• The tops were roughly
cut completely away
using a Roto Zip cut out
tool

13. New Logic
• Each joint inside the
chimney will cause a
turbulence in the air
flow
• This turbulence will be
enough to aid the heat
transfer from the
chimney to the air

14. Assembly line production
• 14 cans are laid in place
• The joints are glued 1/3
of the circumference
then the whole chimney
is rotated
• Repeat glue procedure
twice so all joints are
100%

15. Henry Ford
• In the spirit of assembly
line productions
• “you can have your
chimney in any color, as
long as it is black”
• The second set of
chimneys are ready to
go to the window

16. Installed
• A view from the inside
• 8 chimneys on the left
are the first batch
• 7 chimneys on right are
second batch
• The curtains will cover
them completely and
they will not be seen from
the inside
• Data and calculations will
be shared as they develop

17. Tools used
Hot glue gun The foam can coolers are perfect to
hold the cans while tooling, non slip
and protects your hands

18. Tools used
3/8” electric drill with 1 5/8” hole saw bit
Roto Zip cut out tool, Dremel
Would work also

19. What about next summer?
• My wife’s first question
• Probably divide the chimneys into 2 or 3
modular units
• Mount them into a traditional black box
• Use them to circulate hot air in the wood shed
to dry the firewood for next winter
• Or use for solar cooling of unvented attic
space