# How can I make a hot water electricity generator?

#### Alex 6

Joined Dec 25, 2016
10
I wanted to do a little project and make some kind of thermoelectric generator. I thought of using some kind of Peltier thermoelectric cooler that uses a temperature difference to generate electricity but I am not sure if it would work with hot water. I saw a video of someone using it with fire but I don't want to use fire. There was another video of someone using it with hot water and ice cubes so maybe that would work. Or maybe someone has a better idea? I am not sure if it is even possible but if it is, how would I go about doing it?

#### Tonyr1084

Joined Sep 24, 2015
7,948
The first time I learned about Peltier's was when a girl took one (or more) and mounted it (them) on a copper pipe and wired it to a flashlight head. Think she used a superbright LED. When you hold the torch the LED lit up. The reason was because of the difference in the body heat from her hand to the inside of the open ended pipe.

So any source of temperature difference between the sides will generate a voltage.

#### Alex 6

Joined Dec 25, 2016
10
The first time I learned about Peltier's was when a girl took one (or more) and mounted it (them) on a copper pipe and wired it to a flashlight head. Think she used a superbright LED. When you hold the torch the LED lit up. The reason was because of the difference in the body heat from her hand to the inside of the open ended pipe.

So any source of temperature difference between the sides will generate a voltage.
Thanks for helping!

I am not sure how much of a temperature difference I would need for it to create electricity. I don't know if boiling water and room temperature would be enough. I am new to this concept so I may not be understanding right.

#### Alec_t

Joined Sep 17, 2013
14,370
I am not sure how much of a temperature difference I would need for it to create electricity.
A small temperature difference will generate a low voltage. We have no idea how much electrical energy you are hoping to generate.

#### Tonyr1084

Joined Sep 24, 2015
7,948
The torch mentioned was powered by the heat of the girls's hand versus ambient temperature. Don't remember how many Peltier's she used but you might find something on YouTube.

#### Alex 6

Joined Dec 25, 2016
10
A small temperature difference will generate a low voltage. We have no idea how much electrical energy you are hoping to generate.
I am looking to light up an led or something small like that. I am not sure if it can turn a motor but if it can then that would be cool too.

#### Bernard

Joined Aug 7, 2008
5,784
Lots of free hot water, then " Mineto's (sp) Big Wheel ".
Found on net: Minto Wonder Wheel .

Last edited:

#### Tonyr1084

Joined Sep 24, 2015
7,948

#### Alex 6

Joined Dec 25, 2016
10
So can it light an LED? Would it work with hot water?

#### ebp

Joined Feb 8, 2018
2,332
She claims she lit a LED (actually 3! - but it does appear she has 3 "tiles") by somehow boosting 50 mV to drive them - with 4 components. I know of devices that will operate from less than one volt, but 50 mV - boosted to nearly 3 volts. I don't believe it.

5 foot candles? I don't believe that either on 500 µW (she said she needed 0.5 mW - which is 10 mA !!! at 50 mV, and she claims 50% efficiency, so make that 20 mA). It certainly looked like vastly less than that to me.

In a cool indoor ambient, you might manage a 20°C differential across a Peltier cell by holding your hand against it with ambient at the other side.

#### shteii01

Joined Feb 19, 2010
4,644
So can it light an LED? Would it work with hot water?
A "regular" red led needs 2.2 volts or a little less than that. Can you generate 2.2 volts? Either google it or buy some parts, build the device, measure the voltage.

#### ebp

Joined Feb 8, 2018
2,332
I know an electronics design consultant who has done extensive work with commercial industrial thermoelectric generators (TEG) and has also played around a bit with using TEC (cooler) assemblies as generators. I can't remember what he was using for a heat source. He was trying to use the output to drive a very small fan on the cold side and the efficiency was so low it would just barely keep the fan going. Commercial TEG cells have really dismal efficiency. Generally they are only used where other sources, such as solar, are impractical (too many dark days/weeks/months).

I'll try to remember to ask him about his experiments, but I won't be able to for a few days.

TEC modules won't withstand high temperature, but should be OK with hot water (assuming here we're not talking water heated under pressure).

I can think of ways to boost 50 mV to 2-3 volts, but not without some other source of power to at least bootstrap it.