Thermopiles for power ?

[Super_voip]

I used to have a book "Modern Thermoelectrics" by D.M. Rowe published in the early 80's, in it where many generators based on pielter devices. These included the pace maker to large US Military generators, and gave a good background to all the space based generators. All the moon landings left a nuke behind to power experiments, and the Pioneer? spacecraft also have nukes, no solar in deep space. Deep sea cable repeaters can also be nuke powered according to the book.

 

[Hero999]

I don't see who a pacemaker would work because you need a cold sink for it to work.

 

[The Mad Professor]

'Cold' sink is a relative term, a thermopile generates electricity by exploiting the difference across a temperature gradient.

If your heat source was hot enough even molten lava could be used as a cold sink.

Getting back to the pacemaker, provided the temperature of the heat source is greater than that of the body and the thermopile is efficient enough to extract sufficient energy from the thermal gradient then it could work.

Now if memory serves me correctly there is something on the NASA website about putting the radiator element near the surface of the skin to aid the cooling process.

 

[Hero999]

'Cold' sink is a relative term, a thermopile generates electricity by exploiting the difference across a temperature gradient.

If your heat source was hot enough even molten lava could be used as a cold sink.

Yea I know the second law of thermodynamics.

Getting back to the pacemaker, provided the temperature of the heat source is greater than that of the body and the thermopile is efficient enough to extract sufficient energy from the thermal gradient then it could work.

What would you use for a heat source, I thought the whole point was to use the human body as a het source.

In that case haven't you got that the wrong way round? You need a cooler region of the body heat to escape into.

Now if memory serves me correctly there is something on the NASA website about putting the radiator element near the surface of the skin to aid the cooling process.

Which is useless because as soon as the ambient temperature approaces the body temperature it will stop working. Lie in the sun, in front of a fire or even in bed and it will stop working.

 

[The Mad Professor]

I'm glad you have sound grasp of the second law of dynamics others who read this in years to come may not have the benefit of your education.

If one used a nuclear thermal decay heat source whose temperature was a little higher than the average mean body core temperature then the human body was act as a 'cold sink'. The biological system is designed to be self regulating and can maintain the temperature gradient under a wide range of climatic conditions.

Now if you wanted to use the heat of the human body it gets a bit more tricky but two areas have the potential to be used as cold sinks. The loss of heat from the human skin is well understood but less well documented is the cooling effect of another organ whose surface area is even greater.

As the ambient air temperature is often lower than that of the body you might find a gradient in areas associated with the respiratory system. However the difference in temperatures is likely to be small therefore a lot will depend upon the theromopile design, so your probably looking for a device etched in silicon on the nano scale.

 

[Hero999]

I thought about a nuclear thermal decay but putting highly radioactive isotopes inside the body wouldn't be a very popular idea and there's alos the question of whether you could get rid of the heat without damaging tissue.

I wouldn't rely on the ambient air temperature being sufficiently lower than body temperature to drive a thermopile.

 

[The Mad Professor]

Mention the word 'Atomic' and most people go nuclear on you, so any discussion concerning the general public's popularity of fission power and its derivatives is probably best left alone for now or perhaps started as a separate thread.


Nuclear powered pacemakers have been in use since the 1970's without any adverse problems. Google dug up this pdf which makes for a good overview of the subject.


As for human power;
Whilst the temperature gradient between body and the ambient air may only be small it does exist, all we lack is the technology at present to exploit it.

 

[Hero999]

As for human power;
Whilst the temperature gradient between body and the ambient air may only be small it does exist, all we lack is the technology at present to exploit it.

What happens if the person is in a kitchen, sauna or in hot weather?

If the air temperature is near body temperature then the pacemaker will not work.

 

[rjvh]

What happens if the person is in a kitchen, sauna or in hot weather?

If the air temperature is near body temperature then the pacemaker will not work.

it will start to work when the body is cooled down enoughf RIP

sort of auto start

Robert-Jan

 

[The Mad Professor]

As the body actively regulates its core temperature to stay alive under the conditions you describe 'Hero999' then the gradient would still be there but reversed. Sure there is going to be an upper limit for prolonged periods of exposure to high air temperatures but it would kill a healthy person just as easily.

Fitting a chemical battery or capacitor in the farad range should take up any slack when the thermopile output falls off for whatever reason.

 

[Hero999]

There would need to be some sort of warning device to tell the person when the capacitor is discharging telling them to get out of the heat or die.