This generator converts the heat produced by the lamps flame into a small amount of electricity. I've been experimenting with generating power using various methods and wanted to play around with thermoelectric devices. A few Thermoelectric Coolers (TEC) have been collecting dust in my part drawers and it's time to put one to use.
Thermoelectric coolers operate by the peltier effect. When power is applied, one side gets hot and the other cold. This also works in reverse. If you heat the hot side while keeping the other side as cool as possible, electricity is produced.
This TEC is rated at 12v DC 60W but they're not very efficient when used to generate power however you can still make enough juice to run small items.
The basic design consists of a small heatsink or metal plate on the hot side of the TEC while a large passive CPU heatsink is attached to the cold side. The hot side is heated and dissipated by the cold side's large heatsink. A red LED is connected to the leads of the TEC and will light up once the generator is heated sufficiently.
The lamp is simply an old tin filled with olive oil. A cotton wick is dangled into the tin which soaks up the oil and burns nicely. Many fuels can be used such as vegetable oil or commercial lamp oils. Different fuels and wick diameters will alter flame height and intensity. Vegetable oil works great if you don't mind everything smelling like french fries.
Four 60mm M4 bolts make up the legs with a washer and two nuts on each. To find out which was the hot side of the TEC, I connected it briefly to the 5v on my bench power supply. Be very careful if you chose to do this as the temperature changes quickly. Only apply power very briefly and use a low voltage.
The hot side heatsink slots over the four posts. All connecting surfaces receive a clean with methylated spirits (aka. denatured alcohol) and a dab of thermal paste. Acetone or rubbing alcohol will also do the job.
Thermal paste is essential as it fills the microscopic gaps between the two surfaces allowing better heat transfer for improved electricity production. The TEC is placed on the heatsink hot side down.
The mounting holes of the large heastink were drilled out and a thread tapped. The leg bolts are screwed into these holes and the whole assembly is secured by tightening the nuts. Any excess thermal paste that squeezes from the edges of the TEC can be cleaned with a cotton tip and some methylated spirits.
A red LED will receive the power generated. A small piece of protoboard with a couple of screw posts and a 1 ohm resistor is used to mount the LED and transfer the power. Should the LED meet its maker, it can be switched out for another one easily with the screw posts.
To provide some protection from the wind and prevent contact with the flame, two pipe clamps are secured around the bolts.
The wick is just a piece of cotton rope threaded through a washer. It will take the wick hours to soak up the oil completely but you can cheat by dunking the entire wick in oil for a while before installing in the lamp. Just clean up any spillage on the tin, works better when only the wick is on fire.
The lamp is half filled with olive oil and ready for action. Never fill it more than 2/3 of the reservoir, especially with petroleum based fuels like commercial lamp fuels as they ignite very easily. Obviously this will get hot during use. Let it cool before handling and don't perform any maintenance on a lamp while it's warm. Never leave it unattended either.
It can produce a stable 1.8 to 2 volt in light wind which is fine for the red LED. The key is to get the flame as high as possible while not touching the heatsink as this will leave soot preventing heat exchange.
This worked well however I was interested in how much this little generator could produce if it had a more powerful heat source. An alcohol burner produces an intense flame while being cheap and easy to make. The top reservoir of this alcohol lamp consists of two aluminium can bottoms connected together and a single jet punched in the center with a small nail. The refill cap is made by sticking a nut on the inside with JB Weld allowing a 10mm bolt to screw in and seal the hole.
The bottom of the lamp is a spagetti tin with vent holes and an opening cut with my dremel large enough to accept a tea candle. These two pieces are attached with JB Weld. Just add a small amount of methylated spirits to the reservoir and a candle in the base.
It's primed by lighting the candle and waiting 20 seconds or so. This heats the fuel causing it to release vapour from the jet. Ignite the jet and you've got a decent flame. This type of design is usually used to make portable camping stoves.
This milo tin is modified to suspend the generator above the lamp while protecting the flame from wind. The flame guard portion is a corn tin with the bottom removed and vent holes drilled.
The flames intensity is controlled by the tea candle heating the fuel reservoir therefore the power generated fluctuates a little but still produces between 2.4 to 3 volt which destroyed the unsuspecting LED. I can get a higher voltage by heating the fuel further but this was more to see how far I could push the little chip. I ended up bolting it back on the oil lamp, it's a bit more practical and it looks interesting. Hope you enjoyed the project, consider following me on twitter.