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Home > Archive > Alternative Power sources > January 2006 > Is this for real?
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| A while ago now, a search engine spat out this website while I was
looking for components to build a prototype...
http://www.sterlingsolar.com/main.htm They say thay have a patented
modification to a rankin cycle system that can produce enough power to
run a house from what seems like a tiny amount of thermal energy.
At the time, it looked like an interesting concept, but now they claim
to have a working prototype, and progress toward a production model.
What do you guys think? Is it for real? I must confess, it sounds almost
like it's in the "too good to be true" category for me...
Regards,
Pal
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| The idea is OK. My only problem would be with the amount of fluid you
have to move to generate about 15kw to run a house. This looks like it
will make a fine AC too.
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| Arnold Walker 2006-01-23, 4:21 am |
|
"Bob" <rbarn115@valornet.com> wrote in message
news:1137987813.103918.325460@g49g2000cwa.googlegroups.com...
> The idea is OK. My only problem would be with the amount of fluid you
> have to move to generate about 15kw to run a house. This looks like it
> will make a fine AC too.
It is little wonder you would say that ,since many AC guys will see
adsorption refrigration.
Or more accurately Kalina cycle principles,being used.
Not only would it be put out power ,but the kalina units do it at upwards of
80% effeciency.
60% is more normal.....though.At least that is what the utilty companies are
getting in the field.
His non pump is the theory behind a coffee percolater pump.
Just a few musings from a steamer.......
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| daestrom 2006-01-23, 7:21 pm |
|
"Pal" <"gtsubs at tpg dot com dot au"> wrote in message
news:43d41d84$1@dnews.tpgi.com.au...
>A while ago now, a search engine spat out this website while I was looking
>for components to build a prototype...
>http://www.sterlingsolar.com/main.htm They say thay have a patented
>modification to a rankin cycle system that can produce enough power to run
>a house from what seems like a tiny amount of thermal energy.
>
> At the time, it looked like an interesting concept, but now they claim to
> have a working prototype, and progress toward a production model.
>
> What do you guys think? Is it for real? I must confess, it sounds almost
> like it's in the "too good to be true" category for me...
>
Okay, here is a little 'thermodynamics 101'. A 'heat engine' is a device
that transforms thermal energy (heat) into mechanical energy using a cycle.
*ALL* heat engines have four basic components. 1) A place where heat is
added to a working fluid. 2) A device that extracts mechanical energy from
the working fluid (often a turbine, but cylinder/piston is also used). 3) A
place where some heat is rejected from the working fluid and 4) a device
that returns the working fluid back to (1). The 'pump' doesn't have to be a
spinning centrifugal pump.
Sometimes the various parts are not too obvious. Look for the 'pump' in a
little two-stroke gas engine (the kind that has oil mixed with the gas and
the carburetor feeds into the crankcase). For them, the underside of the
piston draws the air/fuel mix into the crankcase and then pushes it around
into the working cylinder. On gas turbines, it is the inlet compressor. On
some diesel engines, it's a turbocharger. But all heat engines have a
method of moving the fluid back to point number one. That little 'heat
exchanger' that is alternately heated and cooled while the inlet and outlet
valves are alternately opened and closed is the 'pump'.
Okay, now lesson two. 'Efficiency' for a heat engine is defined as <work
output> / <total heat input>. No 'heat engine' can be more efficient than
the Carnot efficiency. The Carnot efficiency is (Thot - Tcold) / Thot where
Thot is the highest temperature reached by the working fluid (measured on an
absolute temperature scale), and Tcold is the lowest temperature reached by
the working fluid (also measured on an absolute temperature scale). So the
most efficient a heat engine operating between 160F (620R) and 80F (540R) is
12.9%. Never (at least in this universe) can it be more efficient than
that. Yes, many folks claim that co-gen is more 'efficient', but only
because they make up their own definition of 'efficiency' as something like
<'useful' energy output> / <heat input> and include some or all of the
*heat* rejected in step 3 as <'useful' energy output>. This rejected energy
can still be useful for some things, but they are not using the
thermodynamic definition of heat engine efficiency.
The 'Rankine' cycle is defined when the working fluid has a phase change
from liquid to gas to liquid. It is characterized by a 'boiler' to vaporize
the liquid, a turbine or piston/cylinder that extracts mechanical energy
from the vapor, a 'condenser' that returns the vapor to the liquid phase,
and a 'pump' that returns the liquid to the boiler.
So, with that, look again and what you see in this 'patented'
'Sterling'[sic] power cycle is that in reality, it is a Rankine cycle, with
a 'different kind of pump'. The heat energy needed to periodically warm the
heat exchanger counts towards the <total heat input>, and the heat energy
rejected as the heat exchanger is cooled counts does not contribute to the
<work output> (if the energy leaves as 'heat', it cannot leave as mechanical
energy).
A *true* Stirling (note correct spelling) is a cycle where heat is added at
constant pressure to a gas while it expands and pushes a piston. Then the
gas is cooled partially in a regenerator, then compressed while heat is
further rejected to the sink. Then the gas is reheated in the regenerator
as it is returned to the heater. There is *no* phase change in a Stirling
cycle. Since the heat engine discussed has a phase change, and no
regenerator, it clearly is not a 'Sterling' [sic] engine.
This vapor cycle device can develop mechanical work from low temperature
differences, but it is not 'novel' nor particularly more efficient than
other similar designs. The additional heat that must be periodically added
to the 'heat exchanger' to pressurize it so that the liquid can flow back to
the boiler just adds to the total heat input requirements. Although it has
no moving parts (other than the valves that cycle open/closed), that is
about its only advantage over a traditional feed pump. A traditional feed
pump uses less energy to move the same amount of working fluid into the
boiler, so the cycle would produce more net mechanical energy output if they
had used a properly sized conventional feed pump.
daestrom
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| daestrom wrote:
> "Pal" <"gtsubs at tpg dot com dot au"> wrote in message
> news:43d41d84$1@dnews.tpgi.com.au...
>
>
>
> Okay, here is a little 'thermodynamics 101'. A 'heat engine' is a device
> that transforms thermal energy (heat) into mechanical energy using a cycle.
> *ALL* heat engines have four basic components. 1) A place where heat is
> added to a working fluid. 2) A device that extracts mechanical energy from
> the working fluid (often a turbine, but cylinder/piston is also used). 3) A
> place where some heat is rejected from the working fluid and 4) a device
> that returns the working fluid back to (1). The 'pump' doesn't have to be a
> spinning centrifugal pump.
>
> Sometimes the various parts are not too obvious. Look for the 'pump' in a
> little two-stroke gas engine (the kind that has oil mixed with the gas and
> the carburetor feeds into the crankcase). For them, the underside of the
> piston draws the air/fuel mix into the crankcase and then pushes it around
> into the working cylinder. On gas turbines, it is the inlet compressor. On
> some diesel engines, it's a turbocharger. But all heat engines have a
> method of moving the fluid back to point number one. That little 'heat
> exchanger' that is alternately heated and cooled while the inlet and outlet
> valves are alternately opened and closed is the 'pump'.
>
> Okay, now lesson two. 'Efficiency' for a heat engine is defined as <work
> output> / <total heat input>. No 'heat engine' can be more efficient than
> the Carnot efficiency. The Carnot efficiency is (Thot - Tcold) / Thot where
> Thot is the highest temperature reached by the working fluid (measured on an
> absolute temperature scale), and Tcold is the lowest temperature reached by
> the working fluid (also measured on an absolute temperature scale). So the
> most efficient a heat engine operating between 160F (620R) and 80F (540R) is
> 12.9%. Never (at least in this universe) can it be more efficient than
> that. Yes, many folks claim that co-gen is more 'efficient', but only
> because they make up their own definition of 'efficiency' as something like
> <'useful' energy output> / <heat input> and include some or all of the
> *heat* rejected in step 3 as <'useful' energy output>. This rejected energy
> can still be useful for some things, but they are not using the
> thermodynamic definition of heat engine efficiency.
>
> The 'Rankine' cycle is defined when the working fluid has a phase change
> from liquid to gas to liquid. It is characterized by a 'boiler' to vaporize
> the liquid, a turbine or piston/cylinder that extracts mechanical energy
> from the vapor, a 'condenser' that returns the vapor to the liquid phase,
> and a 'pump' that returns the liquid to the boiler.
>
> So, with that, look again and what you see in this 'patented'
> 'Sterling'[sic] power cycle is that in reality, it is a Rankine cycle, with
> a 'different kind of pump'. The heat energy needed to periodically warm the
> heat exchanger counts towards the <total heat input>, and the heat energy
> rejected as the heat exchanger is cooled counts does not contribute to the
> <work output> (if the energy leaves as 'heat', it cannot leave as mechanical
> energy).
>
> A *true* Stirling (note correct spelling) is a cycle where heat is added at
> constant pressure to a gas while it expands and pushes a piston. Then the
> gas is cooled partially in a regenerator, then compressed while heat is
> further rejected to the sink. Then the gas is reheated in the regenerator
> as it is returned to the heater. There is *no* phase change in a Stirling
> cycle. Since the heat engine discussed has a phase change, and no
> regenerator, it clearly is not a 'Sterling' [sic] engine.
>
> This vapor cycle device can develop mechanical work from low temperature
> differences, but it is not 'novel' nor particularly more efficient than
> other similar designs. The additional heat that must be periodically added
> to the 'heat exchanger' to pressurize it so that the liquid can flow back to
> the boiler just adds to the total heat input requirements. Although it has
> no moving parts (other than the valves that cycle open/closed), that is
> about its only advantage over a traditional feed pump. A traditional feed
> pump uses less energy to move the same amount of working fluid into the
> boiler, so the cycle would produce more net mechanical energy output if they
> had used a properly sized conventional feed pump.
>
> daestrom
>
>
I believe their website points out right at the top of the first page
that their Sterling engine has nothing to do with the Stirling engine.
Sterling is just the name of the guy who put it together.
That said, thanks for the lesson! My skills and background are in the
electrical and electronic fields, and this whole concept of extracting
kinetic from thermal energy is little more than deep black magic to me... ;)
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| daestrom 2006-01-25, 9:21 pm |
|
"Pal" <"gtsubs at tpg dot com dot au"> wrote in message
news:43d5e5dc$1@dnews.tpgi.com.au...
> daestrom wrote:
<snip>[color=darkred]
>
> I believe their website points out right at the top of the first page that
> their Sterling engine has nothing to do with the Stirling engine. Sterling
> is just the name of the guy who put it together.
>
Yes, I saw that after I re-read the site a second time. I was trying to
read the 'scientific validation', but all I could pull up was the abstract
followed by five blank pages. The abstract claims to support the position,
with, "A supplement detailing calculations for a Rankine cycle", and other
details, but it's just blank. Maybe because the PDF was created with some
tool by 'Foxit' with just an 'For evaluation only' copy?
If they can't pay for a getting a PDF file created, what else are the
cheating on?
Can't help but wonder if they're deliberately trying to play on the
Sterling/Stirling name to fool naive investors into thinking it's a well
proven engine with a novel, 'patented' improvement.
daestrom
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>
>
> Yes, I saw that after I re-read the site a second time. I was trying to
> read the 'scientific validation', but all I could pull up was the abstract
> followed by five blank pages. The abstract claims to support the position,
> with, "A supplement detailing calculations for a Rankine cycle", and other
> details, but it's just blank. Maybe because the PDF was created with some
> tool by 'Foxit' with just an 'For evaluation only' copy?
>
....
Out of interest, are you using Acrobat reader v7? To the best of my
knowledge (second hand information only), v7 has been deliberately
knobbled to not read anything not created by genuine Acrobat software.
Try "downgrading" to v6 and see if you can read it then...
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