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Plasma

Fri Jul 06 2018, 04:16AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
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Posts: 268

Hi, I've been purchasing TEG modules to build a generator, I'm just wondering i plan to have 22 of them in series and just keep parrellel the same number.
I was planning on using one pump for the hot water and one for the cold, as the temperature changes in the water the parrellel sections will be at different voltage and current.

How would you guys balance the parrellel sections
Thanks

radiotech

Fri Jul 06 2018, 04:46PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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I read your post, and reached for a book Ch 7 , Thermo Electricity ,

Electricity and Magnetism for Degree Students, Longmans Green & Co. 7th Ed 1941.

The references go back almost 200 years. Google is your friend.

Plasma

Sat Jul 07 2018, 01:42AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
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Posts: 268

True that. I searched for connecting batteries in parrellel with different voltage, they recommended a diode to stop the higher voltage ones discharged into the lower ones.
There was linear voltage regulator, adding hot water in a tin and put it on the modules, cold side, a large chunk of steel, made about 1 volt, I think the difference would be about 20-40 degrees which matches the dataset, saying this I will look up the voltage range they can handle,
would it make sense to have a transtor bleeding the power from a zener, and try to get as high as voltage as possible, more series modules, or a linear reg at lower voltages.

I type of want the thing to last years and years with no maintenance, reliability?

radiotech

Sat Jul 07 2018, 02:54AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
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Posts: 1546

The couples in parallel would have same voltage when connected
in parallel which would form a Y . I think that if they were equal
in all respects, receiving same heat, they would just half the
source resistance and doubling the output wattage.

Delving further, a circulating current, would change the temperature
of one side of the Y. Moving from one effect to another ? So balance
becomes a thermal flow problem ?

Ohms law was done in heat, i believe before voltage was a consideration.

Tell what the layout is and maybe something will spring to
mind.

The only really clever device I recall is the radio power that ran
off kerosene and also heated the living space in Siberia.

Diodes have tricks of their own, pinch one between your fingers
and it develops a voltage. Hold a soldering iron to the anode
wire of a 1N4007 close to the body, a voltage develops, to the
cathode, it reverses.

"I type of want the thing to last years and years with no maintenance, reliability?"

Find out how satellite RTGs work.

Plasma

Sat Jul 07 2018, 03:54AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
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Posts: 268

The plan was to have 40mm rhs box section one to two meters, they would get put side by side hot, cold, hot, cold, going to weld a pipe at the ends of the box, and connect a hose from cold to cold in a Small shape, plaining on hot goes in one side cold the other to minimise.
the construction should be a problem, but how to wire it up,
the water pump will be a 15 watt 3gpm 10ft lift.
Plan on using fire wood, about 1-5kwh per kg.

Thanks

Sulaiman

Sat Jul 07 2018, 05:31AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I imagine the lengthwise differential thermal expansion of the hot and cold box sections would tear your TEGs to pieces.

Plasma

Sat Jul 07 2018, 06:35AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
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Didn't think of that, thanks, I can give it a bit of slop, don't think it will expand more than 5mm. The module won't be glued just resting against it,

Sulaiman

Sat Jul 07 2018, 11:37AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

If you have a hot water side and a cold water side then
. both sides need to be pumped,
. the hot water side will need a water heater - obviously
. the cold water side will need a water cooler/chiller - D'oh !

I can think of two approaches;
1 for the cold side of each TEG use an individual air-cooled heat sink
(also removes the differential thermal expansion problem)
2 passively cool the recirculating cold water using something like a domestic central heating radiator.

Your main challenge is to try to get your TEG as cheap, reliable, efficient and compact as a steam engine or turbine with generator

(up to about 33%, maybe 10% for a small-scale system) (1 kg coal is about 30 MJ, or 8 kW.h)

Plasma

Sat Jul 07 2018, 12:39PM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
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Posts: 268

Tegmart has water cooled heat sinks the copper and the thing, and the teg are quite cheap $4 each, but the heatsink wasn't $17.
Trying to keep the price down, aiming for 1kw a lot of tegs ðŸ˜ƒ
The wood instead of coal was Woods renewable and relatively clean and cheaper than coal.

Going to look into the domestic radiator, benefits over a car radiator?
Still working on it, but yeah reliable c, cheap heat source, maintenance free (might use gravity feed water)

Plasma

Sat Jul 07 2018, 12:45PM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268

Sorry for the double post, I need a coffee

1530967538 61406 FT182521 Img 20180708 002937

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