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'] Superb low temperature differential Stirling Eng'
2004\04\06@030840 by Ake Hedman

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This has always fascinating me.

Living in Northern Sweden with with the heater on for the bigger part of
the year: Could a stirling engine be used to drive an electric
generator? Anyone tried that?

/Ake

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Ämne: [OT:] Superb low temperature differential Stirling Engine


Superb low temperature differential Stirling Engine.
As nice as I've seen.

       http://users.moscow.com/oiseming/lc_ant_p/Pic_Prj2.htm

Can run on the warmth of a  hand.
Runs for hours from the heat in a cup of coffee (or hot beverage of your
choice).

_________________________

I made the mistake while looking for something else of looking in a
mailbox
that I don't look at often - archived "against the day" - it had 1397
unread
entries. Only looked at a few. This entry caught my eye. Getting started
on
looking at Stirling Engines is a bad way to get any work done :-).

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2004\04\06@035234 by Jason S

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As I understand the stirling engine, it looks like you could power it that
way if the temperature differential is enough.

It would be impractical though.  There is no such thing as a free lunch.  To
run the engine you will be losing heat from your house, and from the first
and second laws of thermodynamics, you will lose more energy than if you
just ran an electric motor or more conventional engine (depending on if your
heating is electric or combustion).

JAson


{Original Message removed}

2004\04\06@042842 by Russell McMahon

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flavicon
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This has always fascinating me.

> Living in Northern Sweden with with the heater on for the bigger part of
> the year: Could a stirling engine be used to drive an electric
> generator? Anyone tried that?

Short answer: No.
Conservation of energy applies.
You need an energy source to power the motor and all such motors will result
in an overall net energy loss.

However, if you had a low grade source of heat you could conceivably use it
to drive an engine to do useful work.
You could eg use a Stirling that ran off the difference between ceiling and
floor heat to drive a fan to pump hot air down to floor level. Would run
faster as difference increased :-)

A Stirling engine's MAXIMUM THEORETICAL efficiency is (Tin-Tout)/Tin.
T in degrees Kelvin = C + 273
actual efficiency is typically 1/2 to 1/3 of this although theoretical can
be approached more closely in a  good design.
eg Boiling water in and room temp out = 373 K in and 300 K out.
Eff = (373-300)/373 = 19.6% MAXIMUM.
Actual would be typically 5% to 10%.
Which shows why a HOT Tin is desirable.

A Stirling runs on the Carnot Cycle which is the most efficient cycle
possible BUT a good engine on another cycle can be more efficient than a bad
Stirling Engine.

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2004\04\06@050237 by Ake Hedman

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But if you use a higher temp difference.

In my case I warm the house with pellets and say I have a stirling
engine in a pre stage to my heater. pellets burn with a temp around 1200
C

1200 + 273 - 300 / 1475 = 79%  1/3 => 27% This goes to the electric
generator.

I guess the losses are in heat so it can be used it to warm the house.

I use about 1000 kg of pellets a week for warming in the winter ( big
house ). The total energy used a day is thus 1000 * 4.8kWh = 4800 KWh
Say I have 20% efficiency for the electivity generator I can take out
960 KWh a day in electric energy!!! and have the rest left to warm the
house.

Do I have a fault in my thinking here?

/Ake

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[.....PICLISTKILLspamspam.....MITVMA.MIT.EDU]För Russell McMahon
Skickat: den 6 april 2004 09:26
Till: EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
Ämne: Re: SV: ] Superb low temperature differential Stirling Engine


This has always fascinating me.

> Living in Northern Sweden with with the heater on for the bigger part
of
> the year: Could a stirling engine be used to drive an electric
> generator? Anyone tried that?

Short answer: No.
Conservation of energy applies.
You need an energy source to power the motor and all such motors will
result
in an overall net energy loss.

However, if you had a low grade source of heat you could conceivably use
it
to drive an engine to do useful work.
You could eg use a Stirling that ran off the difference between ceiling
and
floor heat to drive a fan to pump hot air down to floor level. Would run
faster as difference increased :-)

A Stirling engine's MAXIMUM THEORETICAL efficiency is (Tin-Tout)/Tin.
T in degrees Kelvin = C + 273
actual efficiency is typically 1/2 to 1/3 of this although theoretical
can
be approached more closely in a  good design.
eg Boiling water in and room temp out = 373 K in and 300 K out.
Eff = (373-300)/373 = 19.6% MAXIMUM.
Actual would be typically 5% to 10%.
Which shows why a HOT Tin is desirable.

A Stirling runs on the Carnot Cycle which is the most efficient cycle
possible BUT a good engine on another cycle can be more efficient than a
bad
Stirling Engine.

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2004\04\06@051315 by Ake Hedman

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Sorry 137 KWh a day is the correct value.

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[PICLISTspamspam_OUTMITVMA.MIT.EDU]För Ake Hedman
Skickat: den 6 april 2004 11:02
Till: @spam@PICLISTKILLspamspamMITVMA.MIT.EDU
Ämne: SV: SV: ] Superb low temperature differential Stirling Engine


But if you use a higher temp difference.

In my case I warm the house with pellets and say I have a stirling
engine in a pre stage to my heater. pellets burn with a temp around 1200
C

1200 + 273 - 300 / 1475 = 79%  1/3 => 27% This goes to the electric
generator.

I guess the losses are in heat so it can be used it to warm the house.

I use about 1000 kg of pellets a week for warming in the winter ( big
house ). The total energy used a day is thus 1000 * 4.8kWh = 4800 KWh
Say I have 20% efficiency for the electivity generator I can take out
960 KWh a day in electric energy!!! and have the rest left to warm the
house.

Do I have a fault in my thinking here?

/Ake

-----Ursprungligt meddelande-----
Från: pic microcontroller discussion list
[KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU]För Russell McMahon
Skickat: den 6 april 2004 09:26
Till: RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU
Ämne: Re: SV: ] Superb low temperature differential Stirling Engine


This has always fascinating me.

> Living in Northern Sweden with with the heater on for the bigger part
of
> the year: Could a stirling engine be used to drive an electric
> generator? Anyone tried that?

Short answer: No.
Conservation of energy applies.
You need an energy source to power the motor and all such motors will
result
in an overall net energy loss.

However, if you had a low grade source of heat you could conceivably use
it
to drive an engine to do useful work.
You could eg use a Stirling that ran off the difference between ceiling
and
floor heat to drive a fan to pump hot air down to floor level. Would run
faster as difference increased :-)

A Stirling engine's MAXIMUM THEORETICAL efficiency is (Tin-Tout)/Tin.
T in degrees Kelvin = C + 273
actual efficiency is typically 1/2 to 1/3 of this although theoretical
can
be approached more closely in a  good design.
eg Boiling water in and room temp out = 373 K in and 300 K out.
Eff = (373-300)/373 = 19.6% MAXIMUM.
Actual would be typically 5% to 10%.
Which shows why a HOT Tin is desirable.

A Stirling runs on the Carnot Cycle which is the most efficient cycle
possible BUT a good engine on another cycle can be more efficient than a
bad
Stirling Engine.

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