Heating Semiconductors: Generating Current?

[chhitiz]

if we heat semiconductors, so that the energy provided is more than threshold energy will they generate a current?

 

[Dadface]

if we heat semiconductors, so that the energy provided is more than threshold energy will they generate a current?

Yes I think so if there is a closed circuit for the current to flow.Like conductors, semiconductor arrangements exhibit thermoelectric effects.

 

[chhitiz]

Yes I think so if there is a closed circuit for the current to flow.Like conductors, semiconductor arrangements exhibit thermoelectric effects.

so is it better to use conductors or semiconductors?
what would be the best material for generating maximum current in the least amount of heat?
can you give me it's specifics?
thanks.

 

[Dadface]

For conductors you can refer to the thermoelectric series(try googling).The further apart the metals are in the series the greater the emf for a given temperature difference.I'm not sure about semiconductors but I assume this depends on the doping across the junction and continues to be a developing technology.Perhaps your best bet would be to get in touch with some manfacturers and ask for copies of their data sheets.

 

[ZapperZ]

if we heat semiconductors, so that the energy provided is more than threshold energy will they generate a current?

There's something confusing about this question, and the thread so far.

A "semiconductor" (at least an intrinsic one) is a material with a band gap typically small enough that the ambient temperature is sufficient to allow for the formation of charge careers (electrons in conduction band and holes in the valence band). This is what distinguish semiconductors from band insulators, whereby in the latter, the band gap is large enough that you don't get free charge carriers at room temperature and possibly over a large range of temperature.

Now, in addition to that, just because you have free charge carriers, it doesn't mean that you'll "generate a current", the same way a conductor doesn't spontaneously generate a current just because it has free charge carriers. You still need either an electric potential, or if you are applying the thermoelectric properties, a thermal gradient.

So that is why I am a bit puzzled by the question.

Zz.

 

[Dadface]

There's something confusing about this question, and the thread so far.

A "semiconductor" (at least an intrinsic one) is a material with a band gap typically small enough that the ambient temperature is sufficient to allow for the formation of charge careers (electrons in conduction band and holes in the valence band). This is what distinguish semiconductors from band insulators, whereby in the latter, the band gap is large enough that you don't get free charge carriers at room temperature and possibly over a large range of temperature.

Now, in addition to that, just because you have free charge carriers, it doesn't mean that you'll "generate a current", the same way a conductor doesn't spontaneously generate a current just because it has free charge carriers. You still need either an electric potential, or if you are applying the thermoelectric properties, a thermal gradient.

So that is why I am a bit puzzled by the question.

Zz.

I assumed that he was referring to the semiconductor analogue of an ordinary thermocouple using,for example, PN junctions instead of two different metals

 

[vk6kro]

There are plenty of examples of photovoltaic cells where light causes the generation of a voltage. Solar panels are a collection of such cells.

If you heat one side of a Peltier Cell, you get a voltage generated across the terminals of the device.

 

[ZapperZ]

There are plenty of example of photovoltaic cells where light causes the generation of a voltage. Solar panels are a collection of such cells.

If you heat one side of a Peltier Cell, you get a voltage generated across the terminals of the device.

But that is exactly an example of a thermal gradient!

Until the OP comes back and writes more explanation, we're just guessing.

Zz.

 

[vk6kro]

if we heat semiconductors, so that the energy provided is more than threshold energy will they generate a current?

The Peltier device is the only one I can think of where heat on a semiconductor device produces a voltage. Provided the other side is kept at a constant or lower temperature, of course.

 

[chhitiz]

i was wondering if the heat rejected by an ic engine can be used to charge the automobile battery. what would be the best thing to use?thermoelctric generators or panels of doped semiconductors?could i get any statistics(how much temp diff. produces how much current, etc.)?
thank you

 

[uart]

i was wondering if the heat rejected by an ic engine can be used to charge the automobile battery. what would be the best thing to use?thermoelctric generators or panels of doped semiconductors?could i get any statistics(how much temp diff. produces how much current, etc.)?
thank you

Yes moden thermoelectric generators (TEG's) use semiconductor junctions and the Seebeck/Peltier effect. They're not particulary efficient but there's plenty of waste heat from an IC engine so cost and reliability are probably more important. Car manufacturers are already seriously working on this and I expect we well eventually see the technology in some production models. Currently BMW has implemented a prototype 200 Watt TEG system and VW has implemented fairly impressive 600W of TEG's which they claim can reduce the load on the alternator enough to improve overall fuel efficiency by about 5%.

See article here : http://www.themotorreport.com.au/19610/vw-and-bmw-dabble-in-thermoelectric-generators/"

 

[vk6kro]

You could also use a technique borrowed from Geothermal systems.

They take hot water from underground. Use it to boil a liquid with a low boiling point and use the gas pressure from this boiled liquid to drive a turbine.
A suitable liquid is 2 Methly Butane which boils at 28 deg C (82 deg F). This liquid would then be recovered by cooling it back to a liquid and it could be used again.

The turbine could generate electricity.