Thermoelectric Powered Flashlight

Here's a water bottle which generates electricity to power a flashlight. Useful when camping or if the power goes out.

So how is this amazing feat achieved? The electricity is generated form a Thermoelectric module installed to the base of an aluminum water bottle. A voltmeter has been added to monitor the modules' operation.

Thermoelectric module (TEC1-12706)

Aluminum water bottle

Empty aluminum beverage can

heat sink plaster

1.5-volt Flashlight (Torch)

Battery tester

The electric power is generated form a Thermoelectric module. These can be designed primarily for generating power when a heat source is applied to one side and a cold source is applied to the other side (TEG) or to cool/heat when connected to a power source (TEC). As they can be used in either role a TEC was chosen (TEC1-12706) due to its price and because it will generate electricity at lower temperatures.

Wikipedia has an explanation on how the module works.

A piece of thin aluminum sheet was cut from an empty aluminum beverage can and made flat by moving the sheet against the edge of a table. This sheet of aluminum was cut to same size as the TEC module and attached to the side of the TEG with no writing with some heat sink plaster.

The side of the TEC module with writing on had heat sink plaster applied and then it was attached to bottom of an aluminum water bottle. A weight was applied to the bottle to ensure a close fit occurred while the heat sink plaster dried.

Fill the bottle with cold water and place on a heat plate. Heat the plate to about 80c. Electricity can be measured using a multimeter. About 40 mA and 0.8volts will be generated at about 80c-100c. If the temperature of the hot plate exceeds 120c the solder attaching the wires to TEC are likely to melt and the module will fail. The temperature needs to be carefully monitored. One way to do this is using a temperature gun.

Another way is to monitor the volts generated - as they increase with temperature. At 0.8volts the temperature will be about 100c - the maximum without causing damage. The volts (and therefore temperature) can be constantly monitored by fitting a small voltmeter to the bottle.

Small, low voltage volt meters are a little hard to come by, so make from a battery tester.

Open the back on the battery tester to see if it can be removed from the case, this one needed to be attached to the case to work, so the case was cut to a smaller size using a small hack saw. The cut down meter was then attached to the water bottle using glue form a hot glue gun. Some duct tape was applied around the sides to fill in some gaps of the case.

The meter was solder to the wires coming from the TEC module and a couple of additional wires spliced in and soldered - to output the electricity generated.

The flashlight powered from the TEC and water bottle is kind of special one as it runs off a single AA battery. It was purchased from a diaso discount store.

Wire from the water bottle was connected to the battery terminals of the light.

It was then placed on a heat plate set to about 80c. If more than one volt is shown on the voltmeter, reduce the heat to protect the TEG module from becoming too hot and failing.

The setting on stove's hotplate was at its lowest, the flame was only just on. Any more heat and there's a good chance this particular TEC could overheat and fail. The metal heat plate also helped to disperse the heat.

The water bottle will power the light for about 30 - 60 minutes before the water has warmed too much and needs to be replaced with cold water.

The light can be used away from the heat source by incorporating an extension cable made with wire cut from empty aluminum beverage cans. This will allow you to use the light while you are wondering around, useful when you are camping.

1. A more accurate amp meter was used to measure the current output to be 200mA.
2. When the heat didn't exceed about 100c the light was able to stay on for over 3 1/2 hours.
3. Over this time the water in the bottle increased to 50c.