simple stirling hot air engine made at home with simple tools ,2 cans a baloon

[Malcom \Mal\ Reynolds]

...

 

[Rick]

..

Lots of things _can_ be made. Lots of things that _can_ be made are
not practical.

|

"The Stirling engine is noted for its high efficiency compared to steam
engines, quiet operation, and the ease with which it can use almost any heat
source.
This compatibility with alternative and renewable energy sources has become
increasingly significant as the price of conventional fuels rises, and also
in light of concerns such as peak oil and climate change.
This engine is currently exciting interest as the core component of micro
combined heat and power (CHP) units, in which it is more efficient and safer
than a comparable steam engine."

"Other suitable heat sources are concentrated solar energy, geothermal
energy, nuclear energy, waste heat, or even biological. If the heat source
is solar power, regular solar mirrors and solar dishes may be used."

<http://en.wikipedia.org/wiki/Stirling_engine>

 

[vaughn]

"The Stirling engine is noted for its high efficiency compared to steam
engines...

In theory perhaps, but I really wonder if that is true in real life.

, ...quiet operation, and the ease with which it can use almost any heat
source.

True, but the Stirling has a low power density, which means it gets very big to
produce significant amounts of power. This is especially true is a low-grade
heat source is used because the heat transfer surfaces must become very large.
The Stirling engine is almost 200 years old, yet I have never seen one. There
are multiple reason why they have neve become common. .

Vaughn

 

[Rick]

I want to buy a Stirling engine in the 1-2 hp range suitable for using in
a solar heat (~750F) context. Do you have, or can you find, a link to a
product with a price comparable to internal combustion engines in that
power range?

I'm sorry Morris but other than replying to the post that apparently
Stirling engines do appear to have at least some practical use in the
conversion of solar energy to electricity, I have no involvement whatsoever,
however this engine manufacturer was mentioned in the Wiki article.

 

[Rick]

I'm sorry Morris but other than replying to the post that apparently
Stirling engines do appear to have at least some practical use in the
conversion of solar energy to electricity, I have no involvement
whatsoever, however this engine manufacturer was mentioned in the Wiki
article.

<http://www.infiniacorp.com/application.html>

I've actually come across an online instruction manual for the Philips
MP1002CA 230v/180W hot air generator, manufactured back in 1951, I'm
guessing that a version made now, 60 years on, would be considerably more
efficient?

 

[vaughn]

I'm guessing that a version made now, 60 years on, would be considerably more
efficient?

How so?

 

[Rick]

How so?

I was thinking along the lines off comparing the efficiency of a 60 year old
cars generator to a modern alternator.

 

[Rick]

Interesting, but it doesn't appear to be in the same price class as
Briggs & Stratton (et al). I've done a lot of searching, but it doesn't
appear that anyone is offering consumer-affordable products.

Still looking - and hoping (but not holding my breath).

Yep. The Stirling does have some hope of practical use. I will make
a prediction that if it ever does, it will be in a very limited
application. For sure beats out the wackos pushing "the Amazing Air
Car", the "Psuedoturbine" and the like

It's tantalising to think that enough energy from the sun falls on the earth
in less than an hour to power the world's energy needs for a whole year, if
only we could find a really efficient way of capitalising on even a small
amount of that.
This $600 billion project looks interesting, but without any way of being
able to provide an 'absolute guarantee' of long-term political stability,
then in my view it's a much too risky investment.

 

[Daniel who wants to know]

I was thinking along the lines off comparing the efficiency of a 60 year
old cars generator to a modern alternator.

The generator was actually likely more efficient than an alternator, they
were phased out because they didn't charge at idle unless a pulley ratio was
used that would make them self destruct at engine redline.

12v alternators are only 50-60% efficient, heck they lose 10% just in the
diodes because they put out roughly 14 volts and there is a .7 volt drop
across each diode, so 1.4 volts for the positive and negative diodes
combined. A 6v alternator would lose 20% in the diodes, a 24v just 5%, etc.

The rest is lost from powering the field coil, along with eddy current,
hysteresis, and the I2R losses of the stator windings.

 

[Daniel who wants to know]

Which losses also apply to the dynamo.

However, a further improvement in efficiency can be obtained by using a
permanent magnet based rotor and using a switching regulator to
efficiently convert the varying (with speed) output voltage to the desired
DC output voltage.

This principle is used in the "inverter" based generator sets such as the
Honda EU3000i with its "eco throttle" feature where the DC output is used
to power the 50/60Hz 230/120 volt inverter module.

Whilst the inverter based genset designs might seem to have introduced
additional losses (most notably that of the inverter module), the
efficiency difference is insignificant compared to the two benefits
conferred which are:

1) Decoupling of generator speed from the AC output frequency which allows
engine speed to be used as the main form of output power regulation when
the eco throttle feature is enabled.

2) Decoupling of reactive loads (in particular, leading currents due to
excess capacitance) which can adversely effect voltage regulation in the
classic (cheaper) AC generator based genset designs. In fact it this
'feature' that makes them so unsuitable for powering Personal Computers
(especially when protected by an in line UPS).

The output voltage regulation of a switching sinewave inverter remains
totally unaffected (within defined limits) by such reactive loads. For
example, a cheap 2.8KVA genset I once owned, would, on its 230v regulated
output setting, overvolt to 280v when connected to a 4.7 microFarad PF
correction capacitor borrowed from a 20W fluorescent light fitting. An
inverter based genset would suffer no such deficiency.

I think even just adding a rotor position sensor (simple hall effect reading
the rotor poles just like in a PC brushless muffin fan) and replacing the
regular diodes with MOSFETs would enable synchronous rectification and get
rid of the diode forward drop. The fun part here is that the alternator
would also try to run as a BLDC motor when the engine speed dropped too low
so it would need a circuit to prevent it.

BTW I did not know how much was lost in the carbon brushes of the dynamo, I
just know I have a "3 bobbin" (cut-in/out, current, voltage) 12v mechanical
voltage regulator in front of me that I plan to use on an externally
regulated Chrysler/Bosch alternator to make a rotary 2 stage battery
charger, not efficient, but an interesting project nonetheless.

I still like the Toyota hybrid method, no alternator, just a PM rotor
motor/generator (MG1) and a regulated DC-DC converter for 12v battery
charging. It is kind of an inverter generator integrated into a car.

 

[vaughn]

I still like the Toyota hybrid method, no alternator, just a PM rotor
motor/generator (MG1) and a regulated DC-DC converter for 12v battery
charging. It is kind of an inverter generator integrated into a car.

This is the wave of the future. Another advantage is that they are compact and
can be designed for a wide range of rotor speed, so they can be driven right off
the crankshaft or possibly combined with some other engine accessory. These
things are gaining traction in homebuilt aircraft for just that reason.

Vaughn.

 

[daestrom]

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Hash: SHA1



I beg to disagree.

It could be argued that laminated armatures are far stronger than one
piece, cast versions. Each lamination has a hardened 'skin' on it that
forms during the manufacturing process.

They are certainly more vibration resistant than cast pieces. The reason
they are cast is one of economics. It's cheaper than assembling laminations.

As for the co-axially wound field, it would make no difference. The
reason alternators can spin so high is the fact that it's the *field*
spinning instead of the main windings. The rotor wire is a lot smaller
than that of generator, resulting in a great reduction of centrifugal
force.

Well I disagree with your disagree statement.

It isn't a question of how strong the steel is, it's a matter of how the
winding is placed.

In conventional DC generator, the windings are placed axially in slots
with insulation and wedging. This wedging fails at high speeds,
allowing the winding to spill out of the slot.

Also the turns at each end of the rotor where the wire exits one slot,
travels part way around the rotor and enters another slot is subject to
failure. In tiny machines, the wire is self-supported. In larger
units, the end turns are banded with insulation and steel wire to hold
them inward against the centrifugal forces. Spin it fast enough and
when that support fails, the end turns bow outward, contact the stator
iron and get destroyed.

Because the alternator winding is mounted in between the two iron rotor
pieces, and they each have about 14 steel teeth bent towards the
opposite piece, they provide a very strong case to hold the copper
windings inside. The 'teeth' are about 3/8 inch by 1/2 inch square
steel bar (or larger). When assembled, there is very little space
between them and the wire is crossing the gap at nearly right angles,
not lined along the gap like the slots in a DC generator. (The steel
pieces are forged and heat treated, not cast, BTW)

DC generators are also limited in speed by the commutator construction.
All the bars are held in place with just a couple of bands, one on
each end (on small machines, sometimes steel wire wrapped over the bars
with insulation). At high speeds these bands can stretch from the
extreme forces. This lets the bars slip in relation to one another.
Even if the bars don't come out completely from under the banding, once
a bar slips the brushes get chopped off by the high bar like a buzz-saw
in a matter of seconds.

These problems are also eliminated with an alternator and replaced with
single piece slip rings that are made of one piece (again, much stronger
construction).

daestrom

 

[News]

"The Stirling engine is noted for its high efficiency compared to steam
engines, quiet operation, and the ease with which it can use almost any
heat source.
This compatibility with alternative and renewable energy sources has
become increasingly significant as the price of conventional fuels rises,
and also in light of concerns such as peak oil and climate change.
This engine is currently exciting interest as the core component of micro
combined heat and power (CHP) units, in which it is more efficient and
safer than a comparable steam engine."

For auto use the Stirling was big, heavy and slow to respond, but far more
efficient than an IC engine. The response was the prime drawback. AMC nearly
introduced a Stirling car in the 1970s, claiming the response was overcome
somewhat. For only turning a constant speed generator in a hybrid and no
other function - range extender - they are starting to make sense. Instant
response is then not an issue. The freewheeling piston design Stirling is
small enough these day for such an application - pending R&D. The external
combustion is far cleaner than explosions in a cylinder as in ICE engines.
Highly efficient condensing burning is possible as in gas and oil boilers.

 

[News]

True, but the Stirling has a low power density, which means it gets very
big to produce significant amounts of power. This is especially true is a
low-grade heat source is used because the heat transfer surfaces must
become very large. The Stirling engine is almost 200 years old, yet I have
never seen one. There are multiple reason why they have neve become
common. .

Philips used a small one (an air engine) for running a radio in Africa in
the 1950s. The prime reason they have never caught on is that large auto
makers do not want to take the plunge. They had the ICE piston engines and
cheap oil and made money - to them, they did not want change. The
self-serving corporateocracy advances like a snail.

 

[News]

Yep. The Stirling does have some hope
of practical use.

It powers French and Swedish submarines.

I will make a prediction

Please don't.

 

[Jim Wilkins]

...It appears that it /may/ be possible to incorporate a 100kW
Stirling-driven generator capacity comfortably into a Cooper Mini.
...
Morris Dovey

Have you found a 100W generator that fits on a wood stove?

jsw

 

[News]

It powers French and Swedish submarines.


Please don't.

Cite?
<<<<

Learn to use Google. Again..."It powers French and Swedish submarines".

 

[News]

I'll make another prediction.

Please do not. Drivel usually comes out.

Electric drives will be the norm - the new Tosh batteries and
supercapacitors will make them viable. Physically small range extenders are
seriously being looked into. Audi is looking into the Wankel under the trunk
floor - a concept car had one in. Running at their constant speed "sweet
spot" they are economical and via able. They would be rarely be used anyhow,
so size is more in order than ultra efficiency.

It is clear you do not know the advances in Stirling engines. One a samll
free piston (the only moving part) model is in domestic heating CHP boilers.

 

[News]

On 12/20/11 9:32 PM, harry k wrote:

Agreed.

Only because of massive vested interest in the silly Victorian piston
engines.

 

[Gordon]

It powers French and Swedish submarines.

It also sits at the focal point of a large mirror and generates electricity.
Another form of solar power