How much electricity can a homemade thermoelectric generator (TEG) produce?

In one line

The rule

A thermoelectric generator (TEG) makes electricity from heat by using the Seebeck effect: when two different metals or semiconductors are joined and their junctions are kept at different temperatures, a voltage is produced.

The basic formula is: V = S × ΔT

• V = voltage produced (in volts)
• S = Seebeck coefficient (depends on the materials, in volts per degree Celsius)
• ΔT = temperature difference (in degrees Celsius)

Let's understand it simply

Imagine you have a hot cup of chai and a steel spoon in it. The spoon gets hot at the end touching the chai, but the other end is cooler. If you use special materials and connect them between something hot (like a candle flame) and something cold (like a bowl of water), electricity can flow. This is what a TEG does: it turns heat differences into electricity.

How it works

1. You need two sides: one hot, one cold.
2. Special plates (thermoelectric modules) are placed between these sides.
3. Heat flows from the hot side to the cold side through the module.
4. The module creates a voltage because of the temperature difference.
5. This voltage can power small devices or charge a battery.

The story behind it

The Seebeck effect was discovered by Thomas Seebeck in 1821. He noticed that a circuit made from two different metals with different temperatures at each end could produce electricity. This idea is now used in TEGs, especially in places where normal electricity is hard to get.

Where you see it in real life

• Camping gadgets: Some stoves use TEGs to charge phones using the heat from a fire.
• Spacecraft: NASA uses TEGs to power space probes far from the Sun, using heat from radioactive materials.
• Remote weather stations: TEGs run on heat from burning fuel to keep sensors working in cold places.
• Waste heat recovery: Factories sometimes use TEGs to turn waste heat into extra electricity.

Why it matters

• TEGs can make electricity where there are no wires—like in villages or forests.
• They are silent and have no moving parts, so they last long.
• Useful for emergency charging of small devices.
• They help us use waste heat, saving energy.

Worked example

Let's say you make a homemade TEG with a temperature difference of 50°C and a module with a Seebeck coefficient of 0.05 V/°C.

Given: ΔT = 50°C, S = 0.05 V/°C
Step 1: Write the rule        V = S × ΔT
Step 2: Put in the numbers    V = 0.05 × 50
Step 3: Answer                V = 2.5 V

But the current (how much charge flows) is usually small—often less than 100 milliamps (0.1 A) for homemade TEGs. So, power = V × I = 2.5 V × 0.1 A = 0.25 watts. This is enough for a few LEDs or to slowly charge a phone.

Common mistakes

• Thinking a homemade TEG can run a fan or TV—it usually cannot, as it makes very little power.
• Not keeping one side cold—if both sides get hot, no electricity is made.
• Using the wrong materials—ordinary metals like iron and copper do not work well; special semiconductors are needed.

Remember it

A homemade TEG can light a few LEDs or charge a small device, but not big appliances.