This strange looking pan
is a device to generate power from a low temperature heat source. By
using the seebeck effect, it is able to produce enough electricity to
charge a cell phone and other USB devices. The best part about this
contraption is that it has no moving parts. The mars rover curiosity is powered by a thermoelectric generator similar to this, although they use radioactive material as the heat source.
The device has a nimh
power pack which stores electrical energy for use whenever you need
it, the power pack can be detached for use anywhere. The output is 5V
through a USB port. This device would work especially well were there
is snow available for extra cooling – for example off grid cabins
in remote (snowy!) locations. The bigger the temperature difference
between the two sides of the peltier the bigger the power output.
This idea is not new, it
has been around for a long time. See here
for some very old thermoelectric
generators
The peltiers produce
between 0.6W of electricity to recharge the battery pack.
Download PDF version here
Materials needed
|
- 2 x TEC-12706 Peltier Modules
- DC-DC USB Step Up converter
- Small switch
- Project box
- Small scrap of vero board
- 4 x 3000mah nimh/ni-cd batteries
- 1N4001 diode.
- Battery holders for the batteries
- Miscellaneous wire, solder etc.
- Thermal compound
- Aluminium or copper milk pan
- PC CPU Heatsink
- 4 M4 x 12 bolts
- 4 Long (>75 mm) M6 bolts for the feet
- Electrical connectors (screw terminal type)
- Silicone tubing
Notes:
- The PC heat-sink must
be big enough for the two peltiers to sit on.
- I bought the DC-DC
converter on ebay, it has an integral USB port.
|
Videos (best viewed fullscreen) :
Step 1:
The heat-sink will be
bolted to the milk pan. Mark 4 holes to for bolts to go through the
milk pan into the heat sink. The sizing of these holes will depend
entirely on the heat-sink
|
|
Step 2:
Drill out the holes you
just marked. The drill size should be 4mm
|
|
Step 3:
Drill matching holes in the
heat-sink with a 3.2mm and cut an M4 thread in these holes.
|
|
Step 4:
Lay the peltiers onto the
heat-sink, ready for the dry fit. It's best to do a dry fit first to
make sure that everything lines up properly. When you're ready to
assemble the pan for good, apply thermal compound to both sides of
the peltiers.
|
|
Step 5:
Bolt the pan to the
heat-sink using the M4 bolts. Make sure the peltiers are sandwiched
neatly in between.
Take care not to
overtighten the bolts as this could crush the peltier chips.
|
|
Step 6:
Slip some silicone tubing
over the electrical wires to help protect them from the heat. This
also makes the wires a bit neater.
|
|
Step 7:
Drill four 6mm holes
around the edge of the pan for the feet (bolts). |
|
Step 8:
Bolt the four legs onto
the pan.
|
|
Step 9:
Bolt the screw terminal
to the side of the pan using two M3 x 20mm bolts.
|
|
Step 10:
Connect the two peltier chips in series using the
screw terminals. Light some candles underneath the thermoelectric pan
and fill the pan with water.
Connect a multimeter to the output and measure the
voltage. If the voltage is very low, such as 0.1 – 0.5 volts, then
one of the peltiers is probably connected the wrong way around. Flip
the wires around on one of the peltiers.
It will take around 5 minutes for the heat-sink to
reach full temperature, at this point you should see between 3 – 7
Volts DC output.
|
|
Step 11:
Solder up the circuit for
the step up converter. The peltiers are connected to the battery pack
through the 1N4001 diode. The step up converter is connected to the
battery pack through the switch.
Note: The 3.5mm jack
shown was not used in the final build.
Circuit diagram below.
|
|
Step 12:
Cut out the holes in the
project box for the switches and USB port.
The USB board is glued to
the scrap of strip-board to keep it securely in place and the
strip-board fits into the slots in the project box.
|
|
|
|
