Thermo-electricity

[silentgoodbye]

Hello! I am in no way, shape, or form a scientist. I would consider myself smart, but I wouldn't consider myself educated. I have always wondered about reverse engineering and how one goes about it. You see, I've always looked at heating pads and electric blankets, and wondered, "we can use electricity to create heat, why can we not use heat to create electricity in a wrap or pad type format"? My main reasoning has always been because of cars. Why we can't create a type of film that can be applied to the outside of the car with thermo-electric receptors in them to create electricity from the heat absorbed. I would appreciate it if someone can fill me in on why it can't be done, why it hasn't been done, or if it has what the product is called. A specific scientific explanation and then a lay-man's explanation would be much appreciate as well. I'm sorry, but I didn't know exactly where to post this, so any moderators please feel free to move this where it is needed.

[Orodruin]

It can and has been done. It is called a heat engine and can convert differences in temperature to mechanical or other forms of work.

[Acme]

Hello! I am in no way, shape, or form a scientist. I would consider myself smart, but I wouldn't consider myself educated. I have always wondered about reverse engineering and how one goes about it. You see, I've always looked at heating pads and electric blankets, and wondered, "we can use electricity to create heat, why can we not use heat to create electricity in a wrap or pad type format"? My main reasoning has always been because of cars. Why we can't create a type of film that can be applied to the outside of the car with thermo-electric receptors in them to create electricity from the heat absorbed. I would appreciate it if someone can fill me in on why it can't be done, why it hasn't been done, or if it has what the product is called. A specific scientific explanation and then a lay-man's explanation would be much appreciate as well. I'm sorry, but I didn't know exactly where to post this, so any moderators please feel free to move this where it is needed.

Devices that convert a heat gradient directly to electricity are called thermocouples.

source: >> http://en.wikipedia.org/wiki/Thermocouple

A thermocouple is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more spots. It produces a voltage when the temperature of one of the spots differs from the reference temperature at other parts of the circuit. Thermocouples are a widely used type of temperature sensor for measurement and control,[1] and can also convert a temperature gradient into electricity.

...

Power production

A thermocouple can produce current to drive some processes directly, without the need for extra circuitry and power sources. For example, the power from a thermocouple can activate a valve when a temperature difference arises. The electrical energy generated by a thermocouple is converted from the heat which must be supplied to the hot side to maintain the electric potential. A continuous transfer of heat is necessary because the current flowing through the thermocouple tends to cause the hot side to cool down and the cold side to heat up (the Peltier effect).

 

Thermocouples can be connected in series to form a thermopile, where all the hot junctions are exposed to a higher temperature and all the cold junctions to a lower temperature. The output is the sum of the voltages across the individual junctions, giving larger voltage and power output. In a radioisotope thermoelectric generator, the radioactive decay of transuranic elements as a heat source has been used to power spacecraft on missions too far from the Sun to use solar power.

[Endy0816]

Somewhat ironically you got the one name almost exactly right: Thermoelectric Effect.

 

The more common way to generate heat is via Joule heating though. The first is reversible, the second is not. So you can't reverse your electric blanket, but you could reverse a Peltier cooler.

[swansont]

Thermoelectric electricity generation isn't very efficient, so it becomes a matter of cost/benefit. You can use it in remote situations — space probes use the heat from radioactive decay to do this (RTGs), but most terrestrial situations allow for a different solution to the problem.