# How do you convert Heat into stored Energy/Electricity?

1. ### nukeman

656
Hi everyone,

I am no expert in any means, so if what I am asking is silly, just tell me.

This is an example.

Lets say I have a stove top, and I turn it on full for an hour. Without putting anything on it, how can I harness the heat energy and store it, into lets say something like a battery, or anything I can use to power something.

The stove top is giving out some great heat for an hour. I am wondering if there is a way to harsness the heat energy the stove top is giving off, and storing it.

Does this make any sense?

2. ### rock.freak667

6,231
Normally you'd need to convert that heat into mechanical motion which can convert that into electrical energy.

Like how a turbine is used to generate electricity. Other than that, I do not think there is any directly way to go from heat -> electricity.

3. ### brainstorm

You could heat water and put the water in insulated thermos bottles. Depending on what you want to use the energy for later on, you might want to choose different methods of storing it.

4. ### nukeman

656

I see what you are saying, thanks for clearing that up.

If you can answer this: Example, if I was to hook something up to my bathtub nozzle, that when I fill up the bathtube and as the water pours out of the nozzle it spins a super tiny turbine, how much energy could it store, if theoretically I had something to store the power.

?

### Staff: Mentor

You might generate 100W or so.

6. ### nukeman

656

Forgive me, but generally what could that generate and for what time period?

:)

### Staff: Mentor

I'm not sure what you mean - 100W is 100W.

...though the time to fill your tub is probably 5-10 min, right?

8. ### nukeman

656
I see. So, if I am getting this right, if it takes me 10 minutes to fill my tube, and generates 100W, I could run a 100W light for 10 minutes?

10. ### nukeman

656
Hey really appreciate the info here!

Would you happen to know where I can get info on how much powering a 100w light costs for 10 minutes, or whatever timeframe to go by?

BTW: Awesome astrophotography page! I just bought my first telescope, 6inch dob skywatcher. After I get much better using it, I want to eventually go to something simular to your setup. Nice pics!

11. ### DaleSwanson

351
I couldn't help but be reminded of this SMBC comic.

To make this post on topic and useful, a watt is a unit of power. Energy is often confusingly measured in kilowatt hours, i.e., the energy used by a 1 kilowatt device over 1 hour. To get energy usage just multiply power by time. A 100 watt bulb ran for 10 hours is 1000 watt hours (1 kilowatt). The price of a kilowatt hour varies, and you can check your electric bill for a local price. A general estimate for the US might be 15 cents per killowatt hour.

### Staff: Mentor

Any electric bill will do. My electricity costs about $.16/kWh so 100W for 10 minutes costs about$.0027
Thanks!

13. ### sweet springs

575
Hi, nukeman
Wiki radioisotope thermoelectric generator may be of your interest. Also heat sources of high and of low temperatures produce electricity by technology applied in coal or oil fire or nuclear power plants.
Regards.

14. ### QuantumPion

875
You can turn a temperature differential directly into electricity using a Stirling engine or a Thermoelectric generator. The efficiency is fairly low however, and suffice it to say, you spend a lot more energy running the stove then you could get back from the heat.

15. ### Krotas

1
I want to point out that magnetohydrodynamic (MHD) generator wasn't mentioned. Such system involves a container with ionized gas (plasma), a pipe in with a horizontal constant magnetic field turned on and electrodes at the top and bottom sides of the pipe. If one used the heat to raise kinetic energy of gas inside the container, then releasing gas through the pipe and the magnetic field would make the positive ions and negative electrons flow vertically into opposite directions due to Lorentz force, thus giving a potential difference between the electrodes.
This design is only one type of MHD generators (Faraday's, to be exact). Wikipedia gives other two: Disk and Hall generators.
I don't think that my answer is useful for nukeman, but such ways of getting electricity by only having a heat source should also be kept in mind :)

1

### Staff: Mentor

The OP also ought to check to see how much he pays for the water. It's bound to be more than the value of the electricity he generated.