Kender Solar Engine

lancelot21 · December 5, 2009

Just to illustrate the heat pump into heat engine idea, take the ideal case. For a given temperature differential [math]T_h - T_c{}[/math]:

The ideal energy advantage (coefficient of performance) of a heat pump

[math]COP = T_h - T_c[/math]

The ideal (Carnot) efficiency of a heat engine

[math]\eta = 1-T_c/T_h = (T_h-T_c)/T_h[/math]

So if you run a heat engine from the heat transferred by a heat pump, the overall result is

[math]COP . \eta = 1[/math]

In other words, even if the system has no losses and is ideal, there is no net gain of energy.

Following your own formulas I get rather:

[math]COP . \eta = (T_h-T_c)^2/T_h[/math]

In other words (if I understand your formulas well): if the system has no losses and is ideal, there is a net gain of energy as long as the temperature differential is big enough.

Edited December 5, 2009 by lancelot21

Mr Skeptic · December 5, 2009

In the ideal case, the efficiency of a heat pump into heat engine with such "hot" and cold temperatures is therefore:

Wrong. The hot temperature is the temperature of the heat source, and the cold temperature the temperature of the heat sink. Your confusion is intentional, they put a very cold spot in their design that does nothing but be cold. However, that spot can only be their heat sink if it is warmer than the air outside.

neonsignal · December 5, 2009

Sorry, I messed up the start of the COP equation when I put in the formatting. It is fixed above. And yes, as Mr Skeptic points out, the only potential heat sink is the external air.

lancelot21 · December 11, 2009

Wrong. The hot temperature is the temperature of the heat source, and the cold temperature the temperature of the heat sink. Your confusion is intentional, they put a very cold spot in their design that does nothing but be cold. However, that spot can only be their heat sink if it is warmer than the air outside.

If I understand it well, the cold spot of the Kender engine is a heat sink since it will be heated up by the (warmer) air outside - and the definition of a heat sink (according to http://en.wikipedia.org/wiki/Heat_sink ) is "an environment or object that absorbs and dissipates heat from another object using thermal contact".

Mr Skeptic · December 11, 2009

Yeah, the cold spot is the opposite of a heat sink. Said another way, it is a heat sink for the atmosphere, and a heat source for the engine. This supposed engine has two heat sources and no heat sinks.

**CaptainPanic** · December 21, 2009

Can all the employees of Kender Solar please raise their hands?

Why is it that only new members with less than 10 posts on the forum are defending this scam?

npts2020 · December 21, 2009

Can all the employees of Kender Solar please raise their hands?

Why is it that only new members with less than 10 posts on the forum are defending this scam?

I am sure it is a coincidence.

Tom Booth · January 30, 2010

Hi,

I just happened upon this thread while doing some research for a "Stirling Turbine" of my own design.

Doing research, because I haven't built it yet, and I was trying to figure out if it could really work or not.

Maybe you folks would like to help me out.

I was not at all aware of this "Kender" engine until just arriving here now, but it appears to be based on the same theory as my "Stirling Turbine" idea.

Originally I was just trying to maximize the efficiency of a solar powered Stirling Engine I was working on. As I refined the design and had this machine running in my head... Well, I envisioned the sun going down... but it (The Stirling Turbine) just kept on running drawing indirect solar heat energy from the air.

(Note, this was just ~in my mind~ and I don't know if it could actually work or not but I'm having a difficult time trying to figure out why it wouldn't)

BTW.. in response to the "where is the heat sink ?" question...

I would respond that the "heat sink" is the power turbine.

The turbine works (in part) by converting heat in the air into kinetic energy, thus your "heat sink".

That is, the heat in the air is not traveling to a conventional heat sink, rather, the heat is being CONVERTED into kinetic energy.

This is how an "air cycle" refrigeration or "air cycle" air conditioning system works.

Relatively warm or hot air goes into the turbine... The air molecules impact the turbine blades (Or disks - in a Tesla Turbine) giving up some of their energy. The only energy that a gas has to give up is in the form of heat, so the air temperature drops,... not only due to expansion but ALSO due to the heat energy being converted to kinetic energy.

This is easy to see if you have ever used an air tool for any length of time. When an air tool is under a load, you will see frost forming around the air outlet as the air exiting the turbine is very very cold, not just due to expansion but also due to having given up some of its HEAT energy, even though the air entering the turbine may be quite warm - it exits ice cold (or colder).

This type of refrigeration system is used on cryogenic freezers due to the extreem cold that can be produced using a turbine air cycle refrigeration system.

Unlike the Kender engine there is nothing secret about my design... It has been posted on this Stirling Engine Forum where the theory is explained in detail:

http://stirlingengineforum.com/viewtopic.php?f=1&t=461

And here are a few illustrations I made recently of different designs:

http://prc_projects.tripod.com/stirling_air_turbine.html

http://prc_projects.tripod.com/stirling_air_turbine_2.html

In short, you are creating your "cold spot" for your temperature differential by converting the heat into kinetic energy through the turbine.

This can be accomplished only if the turbine is actually doing some work. While under a load, such as turning a generator, the heat in the air or gas passing through the turbine is converted into kinetic energy then the kinetic energy is converted into electricity by the generator. In effect, this is your heat sink where the excess energy to maintain your temperature differential is being "dumped". But, in this case, instead of just being dumped as "waste" heat it is being CONVERTED into a usable form of energy.

I would be happy to hear your comments and criticisms in regard to the theory and design of this "Stirling Turbine".

BTW. I am using an open air cycle system rather than a closed system, though this could also be a closed system with the addition of another heat exchanger between the intake and the exhaust, but I thought, if you consider the atmosphere itself as part of the system... this becomes your "heat exchanger" - i.e. cold air is exhausted where it is re-heated by the sun and ambient air is drawn into the intake. So the air itself acts as both your heat/energy source and your "refrigerant".

This should be relatively simple to build I think. Just to see if it works...

Mr Skeptic · January 30, 2010

Here's your mistake: a turbine doesn't turn when it gets hot. Do you know what turns a turbine?

Tom Booth · January 30, 2010

Here's your mistake: a turbine doesn't turn when it gets hot. Do you know what turns a turbine?

In an Air-Cycle system the turbine doesn't get hot, it gets cold. One of the problems encountered with an air-cycle system is ICE forming on the turbine blades. Usually this means that moisture must be removed from the system prior to entering the turbine, but I'm hoping that by using a Tesla Turbine (bladeless turbine) this will not be a problem as ice would have a difficult time sticking to smooth disks (hopefully).

The turbine doesn't get hot. The Heat energy in the compressed air powering the turbine is CONVERTED into "pure" kinetic energy.

As I'm sure you are aware, virtually the only energy available to a gas is in the form of "heat" (actually the kinetic energy of the air molecules) so when the gas is made to do work, such as turning a turbine or pushing a piston in a hot air engine, the heat energy is converted into kinetic energy (the motion of the turbine or piston) and the air expanding through and then exiting the turbine then tries to recapture that lost heat energy (i.e. the air gets extremely "cold"), similar to how a gas in the expansion phase of a refrigeration system seeks to recapture lost heat i.e. gets "cold".

"Heat" is partly potential energy and partly kinetic energy. In a gas it consist almost entirely of the kinetic energy of the gas molecules. A gas, expanding through a turbine loses its kinetic/heat energy to the turbine and gets very cold - potentially it can drop to near cryogenic temperatures, but this does not make the turbine hot as the "Heat" has been converted to another form. If the turbine is turning a generator, then the "heat" has ultimately been converted into electricity.

If I'm mistaken, then I'm afraid that guy that had his brain cryogenically preserved so he could be reanimated some day is going to be out of luck, because that is how a cryogenic freezer works, from what I understand.

npts2020 · January 30, 2010

TomBooth; A turbine and an air tool both work from expanding a gas (air in this case) across a set of blades. A pressurized tank or pump provides the differential, causing cooling at the point of expansion i.e. frost on the air tool. In your turbine I am not understanding where you are getting a vacuum to draw warm (or any temperature) air through your turbine blades. If you are not familiar with thermodynamics, it would be well worth your while to learn about the subject before investing a lot of time and energy in what you are proposing. I think when you look closely, you will find that whatever is used to create the pressure differential to draw air through your turbine will use more energy than the turbine generates. In other words, you need a power source of some kind to run it because you don't get out what you put in. I do think that if you can even come up with a more efficient motor it would still be worthwhile, but I will believe it when I see it.

Mr Skeptic · January 30, 2010

TomBooth, if a turbine works as you say, why not toss a turbine into a furnace? Or, why not just let it run off the ambient heat and use it as an air conditioner? Why the rest of the contraption and not just the turbine?

And here I thought that to turn a turbine you had to have fluid flowing through it.

Because if it needs fluid flowing through it, you need some way to make the fluid flow. One way to do that is with a temperature differential, but that requires a heat source and a heat sink.

Tom Booth · January 30, 2010

TomBooth; A turbine and an air tool both work from expanding a gas (air in this case) across a set of blades.

Right

A pressurized tank or pump provides the differential, causing cooling at the point of expansion i.e. frost on the air tool.

What kind of "differential" are you referring to here ?

Pressure differential or temperature differential ?

In your turbine I am not understanding where you are getting a vacuum to draw warm (or any temperature) air through your turbine blades.

A "vacuum" ?

The air isn't drawn through the turbine exactly. It is pressurized above atmospheric pressure and injected into the turbine through a nozzle. In a sense, I guess you could say that the atmosphere is your "vacuum". At least a partial one as compared to the air under pressure. Same as with an air tool. The air is drawn in from the atmosphere and compressed and then decompressed or expanded through the turbine back to the atmosphere.

If you are not familiar with thermodynamics, it would be well worth your while to learn about the subject before investing a lot of time and energy in what you are proposing. I think when you look closely, you will find that whatever is used to create the pressure differential (OK) to draw air through your turbine will use more energy than the turbine generates. In other words, you need a power source of some kind to run it because you don't get out what you put in. I do think that if you can even come up with a more efficient motor it would still be worthwhile, but I will believe it when I see it.

My idea does not use a motor to compress the air. It uses the temperature differential created by the "air cycle system" heat exchanger.

When air is heated it expands and the same air contracts when it is cooled. A Stirling engine uses this principle to drive a piston. The "displacer" in a Stirling engine drives air back and forth against the top and bottom of the displacer chamber, one end of the chamber is hotter than the other so the air alternately expands - creating pressure, then it is driven to the other end where it cools and contracts - creating a partial vacuum. This expansion and contraction drives the piston in a Stirling engine.

At first I was working on having a Stirling engine drive a compressor, but I figured, why use the pressure differential in a Stirling engine to drive a piston to turn a crankshaft to turn a pulley to drive a belt to turn another pulley to drive another crankshaft in the compressor to drive a piston to compress air and trap it behind a check valve to get pressurized air to have a pressure differential to drive the turbine ?

I just eliminated all those redundant moving parts and put some check valves in the displacer chamber to make a kind of direct "Stirling compressor" out of a Stirling type displacer chamber. You get the same, (or possibly greater) pressure differential with just one moving part and very little friction.

It takes very little energy to move a displacer, much much less energy than what you would theoretically get back by using this principle to convert some of the available heat in the atmosphere into pressurized air.

In this concept, as the air is driven back and forth by the displacer - causing it to alternately heat and expand then cool and contract, first the expanding air, instead of driving a piston some of the air is allowed to simply escape through a port where it is trapped behind a check valve. Then as the displacer moves causing the remaining air to impact the cold end of the chamber and lose heat and contract a vacuum is created which draws in more air which is trapped in the displacer chamber behind another check valve. In other words, you have an air pump which operates on a temperature differential to create a pressure differential.

You could think of the check valves as acting like a set of diodes in an electrical circuit used to convert alternating current into direct current.

The check valves convert the alternating pressure in the displacer chamber into direct pressure to run the turbine. (theoretically).

This is difficult to visualize because the air is invisible. It would appear that the "displacer" is just moving up and down in an empty chamber, not doing anything, however, when the air hits the hot end of a displacer chamber it expands explosively in a Stirling engine driving a piston with enough force to drive the engine. Instead of using this expanding air to drive a piston I'm just letting some of the air escape through a port where it is trapped behind a check valve. It's only escape route back to atmosphere is then through the turbine.

Before it reaches the turbine, however, it must pass through a narrow tube in the displacer chamber where it gives off some heat - similar to how electricity gives off heat when passed through a thin wire - due to the resistance. With a gas passing through a narrow tube your resistance comes from the tendency of the air to cling to the inner wall of the tube converting the kinetic energy of the moving pressurized air into heat to heat the top of your displacer chamber and increase the temperature differential within the displacer chamber. The remaining heat is extracted by the turbine to do work (run an electrical generator) causing the air to become very cold. This cold air is then sent through another set of coils in the bottom of the displacer chamber before being evacuated back to the atmosphere.

Merged post follows:

Consecutive posts merged

TomBooth, if a turbine works as you say, why not toss a turbine into a furnace?

Ummm...

I don't think you would get it to do much work that way. That's like saying, why not throw a car engine into a furnace.

Or, why not just let it run off the ambient heat and use it as an air conditioner?

Now you're getting the idea!

Why the rest of the contraption and not just the turbine?

That's like saying why not just run a car engine without gasoline. "The rest of the contraption" as you say, is your "fuel" delivery system. It is what compresses the air to run the turbine.

And here I thought that to turn a turbine you had to have fluid flowing through it.

I think you thunk correctly. If you consider compressed air to be a "fluid". More like a gas I think.

Technically, this is an "expansion turbine" as it uses expanding gas (in this case, compressed air released through a nozzle) to drive it.

Because if it needs fluid flowing through it, you need some way to make the fluid flow. One way to do that is with a temperature differential, but that requires a heat source and a heat sink.

The turbine, in this case, is not driven by a temperature differential, it is driven by a pressure differential. Compressed air in, expanded air out.

In this case, the air is compressed by the expanding air in the displacer chamber where it is then trapped behind a check valve. Since the air is working against itself, instead of the heat/kinetic energy in the air being lost to work against a piston the energy in the air used to compress more air is conserved (transfered air to air) until it reaches the turbine. (except for some that is used to heat the hot end of your displacer chamber, but this heat/energy too is recirculated back into the system)

Edited January 30, 2010 by Tom Booth
Just fixing messed up quote marks

Mr Skeptic · January 30, 2010

But, surely you realize that there is no practical difference between throwing a turbine into a furnace and running it off ambient heat, other than that the furnace has more ambient heat.

Yes, a gas is a compressible fluid.

The turbine, as you say, is run off a pressure differential. The question then, is how do you get your pressure differential. A heat engine creates a pressure differential by using a temperature differential. The turbine draws a fraction of the energy transferred from the heat source to the heat sink. The turbine does not change temperature, other than heating via friction or due to the temperature of the fluid flowing through it.

Let me restate that: the turbine does not suck in heat energy. If it did, again, you wouldn't need any other component.

Also, you can't use a compressor to create the pressure differential, as that is just wasteful.

At the heat source, the fluid expands, increasing its pressure. At the heat sink, the fluid contracts, decreasing its temperature. The turbine is between the heat source and the heat sink, where the pressure differential makes the fluid flow through the turbine. Without the pressure differential, the fluid would not flow and the turbine would not spin.

It may help you significantly to replace the turbine with a piston, as they essentially do the same thing, but one is easier to understand.

Tom Booth · January 30, 2010

But, surely you realize that there is no practical difference between throwing a turbine into a furnace and running it off ambient heat, other than that the furnace has more ambient heat.

I see your point: i.e. the atmosphere is like a giant furnace heated by the sun.

However, in this case, the turbine is not running on ambient heat exactly. At least not directly.

As you say "A heat engine creates a pressure differential by using a temperature differential" The displacer chamber (basically a modified heat engine, at least in principle) uses a temperature differential to create the pressure differential which runs the turbine. (theoretically of course)

The turbine, as you say, is run off a pressure differential. The question then, is how do you get your pressure differential. A heat engine creates a pressure differential by using a temperature differential.

I think you just answered your own question.

The next question I suppose would be, where does the "heat engine" get the temperature differential ? (so as to create the pressure differential to run the turbine)

The turbine draws a fraction of the energy transferred from the heat source to the heat sink. The turbine does not change temperature, other than heating via friction or due to the temperature of the fluid flowing through it.

This is true in the majority of cases where a turbine is used, yes, but I believe the situation is a little different when a turbine is used in an air-cycle refrigeration system.

In an air cycle system, the pressurized air is injected into the turbine while the turbine is under a load. Before entering the turbine the air is not just compressed but it is also cooled by compressing it through a narrow duct or tube where it gives up heat prior to entering the turbine. When it (reatively cold air) is injected under pressure into the turbine it expands violently and is simultaneously made to do work since the turbine is under a load - turning a generator to power something else remote from the system.

In many air cycle systems the turbine is just given some redundant work to do, like powering a big electric fan that serves no other purpose other than to draw energy off the turbine so that it is under a load as the air is expanded through it to draw more energy out of the air so as to furter cool the air for refrigeration or air conditioning purposes.

Where does this energy to run this remote fan (or other load) come from ?

The only place it can come from is from the expanding air that is driving the turbine and the only kind of energy the air has to give up is its heat energy.

This only works when the turbine is under a load (made to do work). if the air is expanded trough a turbine which is simply freewheeling without a load (not doing any work) then yes, there would be no significant energy or heat loss, though the air would become a little colder due to being allowed to expand, but the cold produced due to simple expansion is relatively insignificant as the actual energy contained in the air would not change, it would just be more diffuse. Put the turbine under a load however and the energy level in the air has to drop as this energy is ultimately leaving the system and therefore the temperature of the air passing through the turbine must also drop significantly over and above the temperature drop due to simple expansion alone.

You do not get frost forming on an air tool if you just run the air tool without a load. The simple expansion of the air through the turbine in the air tool does not produce enough cold to form frost. You only get frost on an air tool when it is actually doing work as the heat energy in the expanding air while expanding through a turbine under a load is being converted into kinetic energy to do the work - such as removing lug nuts or tightening down some head bolts.

Let me restate that: the turbine does not suck in heat energy. If it did, again, you wouldn't need any other component.

Except a load and something to supply the working fluid (in this case, compressed air).

The energetic air molecules expanding through a turbine while under a load, impact the turbine blades and transfer their energy to the turbine (to power the load) becoming less energetic. This translates into heat loss. Why? because heat is the only form of energy that a gas has to give up.

Also, you can't use a compressor to create the pressure differential, as that is just wasteful.

Normally I would agree. But what I am using to compress the air is not a conventional air compressor. The air is compressed using the Stirling principle utilizing the temperature differential that results from the ice cold air leaving the turbine which has become very cold as a result of being made to do work while it is trying to expand.

That very cold air from the turbine under a load and ambient air alone could provide some temperature differential. but I'm also (theoretically) removing some heat from the compressed air before it reaches the turbine and adding that heat to the hot end of the displacer chamber to increase the temperature differential in the displacer chamber where the air is being compressed.

At the heat source, the fluid expands, increasing its pressure.

In this case, the heat source is the atmosphere. That furnace you were talking about. Once the air exits the system it is returned to the atmosphere where it can reabsorb more heat. Fresh warm air is drawn back in. If it expands in the atmosphere, this is irrelevant. The atmosphere is the low end of your pressure differential.

At the heat sink, the fluid contracts, decreasing its temperature.

Right. Sort of. As the air is trying to expand through the turbine (under a load) it impacts the turbine blades gives up some of its energy - gets colder and contracts before leaving the turbine housing.

The turbine is between the heat source and the heat sink,

Normally, or in most applications. In this case I think that the heat energy is being taken from the air to do work, this heat energy in the air is being converted into kinetic energy to do work, your "heat sink" is the point at which the air molecules impact the turbine blades transferring their energy to the turbine, which is what turns the turbine and allows it to do work. The air molecules become less energetic at that point. For a gas, "less energetic" translates into "colder".

So the turbine, in this scenario, is not "between" the heat source and the heat sink. It IS between high pressure compressed air and relatively low pressure atmospheric air, but the transfer of "heat" energy into kinetic energy is taking place on a molecular level at the point where the air molecules impact the turbine blades - molecule by molecule.

Actually the "heat" in the air IS kinetic energy on a molecular level, so as the air molecules give up their kinetic energy to the turbine this translates into a drop in air temperature. As these same air molecules are leaving the turbine they are "hungry" to get back that energy that they lost, i.e. the air is now "cold" - able to draw in heat.

where the pressure differential makes the fluid flow through the turbine. Without the pressure differential, the fluid would not flow and the turbine would not spin.

I think there is some confusion here between pressure differential and temperature differential.

The air under pressure enters the turbine through a nozzle where it is expanded to atmospheric pressure as it passes through and leaves the turbine.

It may help you significantly to replace the turbine with a piston, as they essentially do the same thing, but one is easier to understand.

Hmmm...

Makes no difference really. When air or other gas is made to do work it's temperature drops in proportion to how much work it does. Doesn't matter if that work is transfered by means of a piston or a turbine - the air gets colder either way. The only difference is that a turbine is generally much more efficient resulting in colder temperatures.

The temperature of the expanding hot air pushing a piston in a heat engine also drops as a result of being made to do work (not just due to expansion) which helps to maintain the temperature differential.

In an efficient (I mean ideal) Stirling engine, the heat from the hot side of the displacer chamber would never really reach the cold side of the chamber as the heat in the expanding air is converted into kinetic energy to do work as the expanding air pushes the piston.

A Stirling engine actually runs cooler under a load. Without a load the temperature differential would tend to equalize and the engine would loose power or "overheat". Without doing work to convert the heat into another form of energy the heat would eventually creep to the cold end and the temperature differential would be lost.

Same principle. The turbine is just potentially more efficient at converting the kinetic/heat energy in the air into practical work, therefore the turbine is better for making the cold air which is needed for this application to run the "air compressor" to compress more air to run the turbine to make more cold to keep the "compressor" running.

All of this is contingent on the theory that a Stirling type "displacer chamber" can be converted into an "air compressor" by eliminating the piston and replacing it with a couple of check valves.

In other words, the big question is - can you run an air compressor on a temperature differential with virtually no additional energy input other than heat ?

Will the air actually expand out through one check valve and be drawn into the chamber through the other check valve with nothing more than a feather weight displacer bobbing up and down inside the chamber, its movement consuming a relatively insignificant amount of energy.

Is a "Stirling compressor" possible ? Which is the heart of this system.

If that is possible, then the pressure differential produced should be able to run the turbine (or at least try for a while) which could then produce the temperature differential (theoretically) needed to continue compressing air to continue running the turbine etc..

The "waste" product of this system would then be the energy used to power the load on the turbine... i.e. usable energy exiting the system.

This is not energy from nothing or "perpetual motion". The solar heat energy in this "furnace" we call an atmosphere would be so-to-speak "wrung out" of the air and converted into a usable form leaving behind it a cold spot for your temperature differential.

This will only continue (if it ever gets started) so long as the excess energy is being drawn off by the attached load on the turbine. In effect, the remote load on the turbine is your "heat" sink.

Mr Skeptic · January 31, 2010

This is true in the majority of cases where a turbine is used, yes, but I believe the situation is a little different when a turbine is used in an air-cycle refrigeration system.

In an air cycle system, the pressurized air is injected into the turbine while the turbine is under a load. Before entering the turbine the air is not just compressed but it is also cooled by compressing it through a narrow duct or tube where it gives up heat prior to entering the turbine. When it (reatively cold air) is injected under pressure into the turbine it expands violently and is simultaneously made to do work since the turbine is under a load - turning a generator to power something else remote from the system.

Be aware that refrigeration is a heat pump, not a heat engine. A heat pump creates a temperature differential via input of energy. A heat engine uses a temperature differential to output energy. They are opposites in a sense.

In a heat pump, the turbine does work compressing a gas, usually to it's condensation point, and passes it through the heat sink. After cooling at the heat sink, the fluid is allowed to expand at the heat source, and the expansion causes the temperature to drop, so that it can pick up heat from the heat source. The heat source in this case is usually cooler than the heat sink. This requires an energy input to function, which is used to create a pressure differential.

Refrigeration however you may to it requires an energy input. This usually means electricity, and most definitely does not mean ambient heat (because, again, you can't turn a turbine by putting it in a room).

Makes no difference really. When air or other gas is made to do work it's temperature drops in proportion to how much work it does. Doesn't matter if that work is transfered by means of a piston or a turbine - the air gets colder either way. The only difference is that a turbine is generally much more efficient resulting in colder temperatures.

Correct, they do the same but the turbine is usually more efficient. I guess the part you are missing is, how do you get your pressure differential? Here the piston helps you understand things. Also, remember that heat flows from hotter things to colder things, as you can look at a batch rather than a flow which may be easier. You correctly infer that some of the heat energy gets converted to kinetic energy of the machine. Your mistake is in the quantity, or perhaps confusion between heat and kinetic energy.

Temperature has no direction. Kinetic energy has a direction. You can use a temperature difference to give a heat flow, which does have a direction.

Somehow, you think that the turbine or piston will get cold in and of itself... it won't. Heat flows from hot to cold, Second Law of Thermodynamics and the arch-nemesis of all free energy machines.

In an efficient (I mean ideal) Stirling engine, the heat from the hot side of the displacer chamber would never really reach the cold side of the chamber as the heat in the expanding air is converted into kinetic energy to do work as the expanding air pushes the piston.

The efficiency of an ideal heat engine is Efficiency = [1 - (temperature of heat sink)/(temperature of heat source)]. Real heat engines are less efficient.

http://en.wikipedia.org/wiki/Heat_engine#Efficiency

In other words, the big question is - can you run an air compressor on a temperature differential with virtually no additional energy input other than heat ?

The temperature differential is the compressor. The "compressor" creates the pressure differential that powers the turbine. But, again, the turbine is not a heat sink.

This is how a heat engine works:

1) Heat source heats up fluid maintaining constant volume, which pressurizes it.

2) Pressure differential is used to drive a piston or turbine. Only a fraction of the energy is transferred to the the turbine; the rest is waste heat.

3) The gas is allowed to cool at the heat sink at constant pressure, which reduces its volume.

4) The cooled, reduced volume fluid is introduced into the heat source. If a pump is needed to force it in, this will require less work than gained in step 2, because the pressure is the same but the volume smaller.

The net results are:

A) Transfer of heat from heat source to heat sink

B) A fraction of the heat transferred, is converted to mechanical work.

Tom Booth · February 1, 2010

Be aware that refrigeration is a heat pump, not a heat engine. A heat pump creates a temperature differential via input of energy. A heat engine uses a temperature differential to output energy. They are opposites in a sense.

Hmmm...

I am aware of these points. No problem there, except that I'm beginning to wonder if you have looked at the diagrams of my theoretical "Stirling Turbine" idea.

Two different versions here:

http://prc_projects.tripod.com/stirling_air_turbine.html

http://prc_projects.tripod.com/stirling_air_turbine_2.html

This is a kind of hybrid heat engine AND air-cycle heat pump combined with all redundant moving parts eliminated. As you say: "A heat pump creates a temperature differential via input of energy. A heat engine uses a temperature differential to output energy. They are opposites in a sense"

This is correct. But this engine is BOTH. However the "Heat Engine" has been stripped down to the bare essential element. It's "displacer chamber" with only one moving part that bears no load and encounters very little friction in its operation. It also doubles as the "compressor" for your air-cycle cooling system. A "compressor" which still, bears no load and encounters no friction.

The only other moving part is the turbine for your air-cycle heat pump which also operates with relatively little friction.

By combining these "opposites" at least two major sources of energy drain on both systems have been virtually eliminated in their entirety. The compressor for your heat exchanger and the entire mechanical apparatus of your heat engine - no piston, crankshaft, gears etc.

I'm not certain how much you know about the Stirling engine,... but I'm assuming that you know that what allows it to operate and produce power is the fact that it takes LESS power to move the displacer than it takes to drive the piston with the resulting pressure changes.

By eliminating the piston and replacing it with a more efficient turbine and using check valves to convert the alternating pressure changes into a steady flow, the same principle should hold true i.e. it takes less energy to move the displacer than what we can gain back at the turbine.

Your turbine is now a replacement for the piston in your heat engine and has therefore become your power producing unit which theoretically, like the piston in a Stirling Engine can produce more power than it took to compress the air to run it... and it is MORE EFFICIENT than a piston. It also doubles as the primary element in your air-cycle refrigeration system... Which in a normal air-cycle system would be an energy drain on the air-cycle system. This former "energy drain" that normally would have also needed a compressor to run it, has now, with this configuration, become a power producing element of the system, replacing your former power producing piston in your heat engine. So, given an initial temperature differential you can now theoretically get more power from the turbine than what would be needed to move your displacer to keep compressing air to keep powering the turbine.

As long as a temperature differential can be maintained, you are now getting more power out than what you put in. Incidentally, an air-cycle system heat pump produces an extreme temperature differential. A temperature differential more extreme than what would probably be needed to get the system started... and that, without any additional energy input. By combining functions, no other elements are needed - other then a steady supply of heat.

In a heat pump, the turbine does work compressing a gas, usually to it's condensation point, and passes it through the heat sink. After cooling at the heat sink, the fluid is allowed to expand at the heat source, and the expansion causes the temperature to drop, so that it can pick up heat from the heat source. The heat source in this case is usually cooler than the heat sink. This requires an energy input to function, which is used to create a pressure differential.

These points are well understood, but they do not apply to this particular configuration. In this case, the turbine does not compress the gas, the gas is decompressed through it. The turbine is your power producing element not a power consuming element. The gas is compressed by the action of the displacer.

Refrigeration however you may to it requires an energy input. This usually means electricity, and most definitely does not mean ambient heat (because, again, you can't turn a turbine by putting it in a room).

I'm sure you are aware that any air conditioner, refrigerator, freezer, and any other heat exchanger including the air-cycle system with a turbine function quite normally while immersed in this "furnace" we call an atmosphere. Theoretically, they could all be run on the energy output from a Stirling Engine running on the same ambient temperature air if the Stirling engine were made to run on ice to provide it with a temperature differential.... and the air-cycle system not only produces temperatures potentially much colder than ice, it also produces heat much hotter than ambient temperatures.

...I guess the part you are missing is, how do you get your pressure differential?

Initially, to get things started you would have to "charge" the system with compressed air from an outside energy source - like an air compressor.

This air would be pumped into the pipes at some point near where the pressure gage in the second illustration is located. The compressed air, as it begins to travel through the system would first encounter the narrow "heating element" in the top of the displacer chamber and begin giving up some heat, initiating some temperature differential within the displacer chamber. The air would then continue traveling through some additional coils until it reached the turbine. The compressed air would exit the nozzle into the turbine and begin turning the turbine rotor. When the turbine got up to speed, you could then apply a load to the turbine. The air expanding through the turbine would be colder than it was upon entering the turbine. This colder air would be piped (The pipes insulated against the heat of the ambient air) back to the displacer chamber to begin providing the cold element of your temperature differential. The cold air would then continue traveling - exiting the pipes at the bottom of the displacer chamber and the cold air would be passed across the previously mentioned "additional coils". This would begin cooling the compressed air inside these coils before the compressed air could reach the turbine - pre-cooling the air before it enters the turbine and thus making the air exiting the turbine that much colder. The cool air then exits the system back to atmosphere. This would continue until a substantial temperature differential is established within the displacer chamber and we can begin running the displacer off of a fraction of the electrical energy being produced by the turbo-generator. An additional remote load would also have to be maintained on the turbine.

Once the displacer begins its motion - converting the established temperature differential into a pressure differential the external source of compressed air can be removed. As the turbine is putting out more energy than it take to provide action to the displacer the system should now be able to maintain its own temperature differential and keep running. In fact, the temperature differential should INCREASE as it begins to run on its own as the heat used by the displacer unit to compress the incoming air is being recirculated and there is a continuous supply of heat provided by the fresh incoming air being supplied to it. So rather than loosing the pressure and temperature differentials provided by the initial "charging" of the system the temperature and pressure differentials should increase incrementally as the system operates. Theoretically, some regulating mechanisms would need to be introduced to prevent a run away condition and keep the pressure and temperature differentials at some specified levels.

Here the piston helps you understand things. Also, remember that heat flows from hotter things to colder things, as you can look at a batch rather than a flow which may be easier. You correctly infer that some of the heat energy gets converted to kinetic energy of the machine. Your mistake is in the quantity, or perhaps confusion between heat and kinetic energy.

As I understand it. For a gas, heat energy and kinetic energy are essentially the same thing. When heat is added to a gas, the molecules become more active and therefore need more room to move around, i.e. the gas tries to expand. If the gas is forced into a small confined area where it cannot move around as freely it is forced to give up heat. etc. With a gas, heat energy and kinetic energy are closely related if not identical.

Temperature has no direction. Kinetic energy has a direction. You can use a temperature difference to give a heat flow, which does have a direction.

I don't think this has any relevance to this system except perhaps within the "displacer" unit where the temperature differential between the heating and cooling coils is used along with the action of the check valves to convert the alternating expansion and contraction of the air into a direct flow for your "compressor".

Somehow, you think that the turbine or piston will get cold in and of itself... it won't. Heat flows from hot to cold, Second Law of Thermodynamics and the arch-nemesis of all free energy machines.

I do not "think that the turbine or piston will get cold in and of itself".

Are you at all familiar with the air-cycle system cooling process ?

As I understand it, the air passing through the turbine gets extremely cold due to the expanding air being made to do work.

There is no "flow" of "heat" to a "heat sink". There is, however a flow of energy out of the system. As this energy is being taken from the "kinetic" energy of the gas which is driving the turbine - the gas becomes less energetic and its expansion is reversed. The gas gives up much of its energy but has no way of getting it back immediately, assuming that the turbine is insulated from external heat sources. It is therefore ready to absorb more energy i.e. it is extremely cold, but it is unable to do so until it reaches the displacer chamber, where it is used to provide your temperature differential but will not ultimately gain back the energy lost until it is evacuated from the system back into the atmosphere where it can heat up again. Eventually, after it makes a few trips around the world it may reenter the system with a fresh supply of heat to be utilized by the system.

The efficiency of an ideal heat engine is Efficiency = [1 - (temperature of heat sink)/(temperature of heat source)]. Real heat engines are less efficient.

http://en.wikipedia.org/wiki/Heat_engine#Efficiency

Of course, which is why I made the distinction.

The temperature differential is the compressor. The "compressor" creates the pressure differential that powers the turbine. But, again, the turbine is not a heat sink.

No, it is not a "heat sink". Not in the conventional sense anyway. But in this system it IS an ENERGY SINK and for a gas, that amounts to the same thing.

Technically, I would say that the heat is CONVERTED into another form of energy - ultimately, it is converted into electricity by the turbo-generator and exits the system. If this were connected to the grid, the heat might re-emerge as radiant heat in a toaster or electric range somewhere to help cook somebody's breakfast - be released back into the atmosphere and eventually find its way back in the vicinity of the "Stirling Turbine" and be sucked in where its heat energy could once again be utilized. If you include the atmosphere as part of the system this is really a "closed" system with the atmosphere acting as your heat exchanger where the gas is expanded and allowed to recapture some heat before being drawn back in - maybe, someday, if the system is in operation long enough.

This is how a heat engine works:

1) Heat source heats up fluid maintaining constant volume, which pressurizes it.

2) Pressure differential is used to drive a piston or turbine. Only a fraction of the energy is transferred to the the turbine; the rest is waste heat.

3) The gas is allowed to cool at the heat sink at constant pressure, which reduces its volume.

4) The cooled, reduced volume fluid is introduced into the heat source. If a pump is needed to force it in, this will require less work than gained in step 2, because the pressure is the same but the volume smaller.

The net results are:

A) Transfer of heat from heat source to heat sink

B) A fraction of the heat transferred, is converted to mechanical work.

I'm not sure what you are describing in the above, but it does not sound like the action of any Stirling Engine that I'm aware of and certainly does not apply to this system in every particular.

Taking it step by step as it applies or otherwise to this system:

1) Heat source heats up fluid maintaining constant volume, which pressurizes it.

This applies, the hot end of the displacer chamber heats up the air inside it when the displacer moves down forcing the air up against the "heating" coils.

2) Pressure differential is used to drive a piston or turbine.

In this system, this does not happen immediately. Rather, the air is allowed to expand through a port with a check valve as it reaches maximum pressure. Once it exits it is trapped under pressure behind the check valve.

Only a fraction of the energy is transferred to the the turbine; the rest is waste heat.

In this system, much of this "waste heat" in the gas is recirculated through a narrow coil within the displacer chamber where under pressure and passing through a confined space it is made to give back much of this "waste heat" so as to help maintain your temperature differential - before it ever reaches the turbine. By the time the compressed air reaches the turbine it should be below ambient temperatures while still under pressure. This is much like a gas liquefaction process where gas is simultaneously compressed and cooled until it becomes so dense that it liquefies. This system does not go to that extreme of liquefying the air but it is going in that direction long before the gas reached the turbine. What powers the turbine is NOT the heat of the compressed gas, which has already been removed but its violent expansion once it is injected into the turbine through a very narrow nozzle (like a propane torch nozzle) where it escapes its confinement compressed and cooled within a narrow tube. This is not quite a change of state, but the principle is similar,... like the liquid propane escaping the bottle through the torch nozzle where it can now expand back into a gas. Temperature and pressure have little of nothing to do with this expansion, it is more like a change of state where the cooled and compressed gas is liberated and expands simply because it now has room to do so. In the process it now is looking to absorb heat but it is not able to do so until it returns to the displacer chamber. i.e. there is no, or very little "waste heat".

3) The gas is allowed to cool at the heat sink at constant pressure, which reduces its volume.

The cold gas leaving the turbine has already expanded to atmospheric pressure. There is no "Heat Sink" where the gas is "allowed to cool" it is already cold. This cold gas itself is used as your heat sink as it is piped through the displacer chamber to provide the cold side of your temperature

differential to the displacer chamber which operates like a "heat engine" but functions as your "compressor" for the Air-Cycle System. The volume of the gas is not "reduced". If anything it is still expanding after leaving the turbine and still trying to reclaim its lost heat until it is evacuated back to the atmosphere.

4) The cooled, reduced volume fluid is introduced into the heat source.

Sort of. But the "fluid" (Air) is not reduced in volume, except perhaps on a molecular level, but has been exposed to atmospheric pressures. The "heat source" is the atmosphere into which the air is eventually released and can reclaim the heat it lost while passing through the system.

If a pump is needed to force it in,

No pump is needed. The air escapes to the atmosphere quite willingly I should think.

this will require less work than gained in step 2, because the pressure is the same but the volume smaller.

It will require no, or very little "work" whatsoever, other than perhaps a bit of back pressure against the air exiting the turbine behind it... which is helping to push it along. But again, the turbine is not a power consuming unit, it is a power producing unit. It does not "pump" the gas. It simply provides an escape route back to atmosphere through the orifice in the turbine nozzle and extracts energy from the gas in the process as it is attempting to escape and expand and return back to the atmosphere. That this will require "less work" is something of an understatement.

Rather than needing a pump to force the gas to the heat source the gas quite willingly escapes to the "heat source" and energy is extracted from it in the process by only allowing it to escape back to the atmosphere if it first does some work for us at the turbine.

How whatever kind of heat engine you are describing operates, this applies very little to this hybrid air-cycle system/heat engine hybrid thing that for want of a better name I'm calling a "Stirling Turbine" for the moment.

I believe that it can very well operate within this "furnace" if you can initiate a temperature differential and then insulate and maintain it against unwanted heat gains and losses to or from the atmosphere.

A Stirling Engine could "run on ice" inside a furnace if your block of ice is kept well insulated and if you can eject unwanted excess heat by converting it into electricity where it can be dissipated at some remote location. Especially if you can find a way to make your "Stirling Engine" double as an "ice maker".

My illustrations do not depict any insulation around this thing, but certainly it would have to be well insulated against various unwanted heat gains and losses at various junctures throughout the system.

I have my own doubts about all this working as intended, but as far as I can see your criticisms don't seem to apply or are irrelevant to this particular system.

This is not just a heat engine nor is it just an air-cycle cooling system it is a hybrid combination of both which has allowed for the elimination of all the "energy hog" components generally present in such systems. All redundant moving parts have been eliminated, there is very little friction anywhere within the system. The only energy drain on the system is minuscule (the operation of the displacer) and the potential energy output is virtually unlimited.

If a block of ice were well insulated, I imagine that a well built Stirling Engine could use it for it's temperature differential almost indefinitely as the heat passing through the engine on its way to the ice is interrupted and energy is extracted and the heat itself is "regenerated" so very little of it ever actually completes its path towards the ice. If the engine can double as an "ice-maker", with no additional energy input, why could it not maintain this temperature differential indefinitely while continuing to output energy which it has drawn from the atmosphere and converted from heat energy into kinetic energy ?

Merged post follows:

Consecutive posts merged

And here I thought that to turn a turbine you had to have fluid flowing through it.

Because if it needs fluid flowing through it, you need some way to make the fluid flow. One way to do that is with a temperature differential, but that requires a heat source and a heat sink.

This point regarding the air getting cold as it passes into and is made to do work through the turbine seems to be the main point of contention.

There is another way that a turbine can be turned which is commonly used in refrigeration and gas liquefaction processes, especially where very low temperatures are required.

Technically the gas being "injected" into the turbine in this engine is not really being injected under any tremendous amount of pressure. First it has been compressed in the displacer chamber, then it goes through several stages of cooling. This cooling helps to contract the air reducing its volume so that more and more air can be compressed into the same narrow tube. By the time this gas reaches the turbine it has cooled and contracted so much that it still is not under all that great a pressure.

When it is released into the turbine, it is NOT the little pressure behind it that turns the turbine. The gas virtually drips out of the nozzle as a liquid so-to-speak. Though it is very unlikely that the gas will actually be liquefied at this point it is theoretically possible. My point is that there is not a lot of pressure behind it. Not enough to actually turn the turbine.

The energy to turn the turbine comes mostly from the gas itself. The gas expands on its own.

This is the reverse of what took place earlier when the gas was compressed and forced to give up heat. Just as air got hot under compression it gets cold during decompression.

The ENERGY for this violent expansion has to come from the air molecules themselves. As a result, the pre-cooled air entering the turbine cools down even more as it expands.

But as it expands through the turbine it is also made to do work. As the pre-cooled gas, now even colder due to using its own INTERNAL molecular energy to expand itself works against the turbine blades, it loses even more energy and its temperature drops further.

This process of turbo-expansion can result in such extremely cold temperatures it is commonly used in the liquefaction of gases or in cryogenic freezers. If this process were repeated the gas could loose enough energy to cause it to liquefy.

I don't think that this little engine would get anywhere near producing that kind of cold but it is not only theoretically possible, this is how gasses are presently being liquefied by industries all over the world. i.e. by turbo-expansion of a pre-cooled compressed gas.

Your insistence that no change of temperature takes place inside a turbine is only applicable to - say, something like a water driven turbine or a wind turbine not a turbo-expander where a gas is giving up its own internal molecular energy to do the work of expanding and turning the turbine.

Edited February 1, 2010 by Tom Booth
typo

Mr Skeptic · February 1, 2010

So, basically a compressor is powering your turbine. I must admit I don't see the point in allowing the compressed fluid to cool and then allowing it to warm to expand. That way you lose even more energy than just allowing it to expand while still hot.

Your insistence that no change of temperature takes place inside a turbine is only applicable to - say, something like a water driven turbine or a wind turbine not a turbo-expander where a gas is giving up its own internal molecular energy to do the work of expanding and turning the turbine.

No, it is exactly the same. The same thing drives the turbine, there is no difference. In both cases the energy is extracted from the flow of fluid, and not from the temperature of them. In both cases, were the fluid to be slowed by friction or turbulence instead, the fluid would heat up.

Now, it seems to me that you probably got something backwards. If the turbine you describe is used specifically to achieve low temperatures, then it would make no sense at all to power the turbine with the gas's expansion. Rather, it would make more sense to input energy into the turbine to create a lower pressure causing the gas to expand or evaporate more rapidly and thus produce more cooling.

Tom Booth · February 1, 2010

So, basically a compressor is powering your turbine.

Not exactly.

I must admit I don't see the point in allowing the compressed fluid to cool and then allowing it to warm to expand.

I'm not sure what you are talking about. In the turbine ?

It is not being allowed to warm to expand. The expansion takes place without any transfer of heat. The gas expands on its own becoming more diffused. As the molecules are using their own energy to carry out the expansion the gas gets colder not warmer.

That way you lose even more energy than just allowing it to expand while still hot.

No, actually, the little buggers have a lot more heat energy to give up than you might imagine. All the way down to near absolute zero. If anything you are actually gaining energy as the expanding molecules impact the turbine.

No, it is exactly the same. The same thing drives the turbine, there is no difference. In both cases the energy is extracted from the flow of fluid, and not from the temperature of them.

I don't mean to be disagreeable, but I believe you are very mistaken. The use of expansion turbines to cool gases is a fairly obscure topic. If the turbine is insulated against heat intrusion from the environment the gas expands anyway drawing upon its own internal energy to do so and gets colder in the process.

In both cases, were the fluid to be slowed by friction or turbulence instead, the fluid would heat up.

If there is any heating up by friction it is minuscule as compared with the internal energy given up by the gas molecules to do the work of turning the turbine against the load on the turbine load. In giving up this energy the Gas gets extremely cold.

Now, it seems to me that you probably got something back wards. If the turbine you describe is used specifically to achieve low temperatures, then it would make no sense at all to power the turbine with the gas's expansion. Rather, it would make more sense to input energy into the turbine to create a lower pressure causing the gas to expand or evaporate more rapidly and thus produce more cooling.

In this case you isolate the turbine from external heat sources so that the gas is forced to use its own internal energy to Carry out the expansion through the turbine - doing work in the process.

The reason being that you want the gas to get very cold so as to be able to utilize that cold for your temperature differential when the air makes its way back through the displacer chamber as well as to further pre-cool the air before entering the turbine.

If you powered the turbine, rather than drawing power from it, the gas, if anything would have less work to do - since it no longer has to do any work to move the turbine out of its way to expand and therefor you would draw less energy from the gas and you would get less cooling of the gas.

I don't believe I have anything backward, but I think that you may need to brush up on how an expansion turbine is used to cool various gasses. This has innumerable applications for refining of natural gas, liquefaction of gases, cryogenics, refrigeration, etc.

Turbines are used in this manner to cool gases every day, to liquefy oxygen to fill oxygen tanks, cool aircraft cabins, to liquefy propane so it can be put into tanks to heat peoples homes etc. etc.

I've read dozens of articles on the subject, watched educational videos, read dozens of websites and looked in numerous books and encyclopedias about the use of turbines for cooling in refrigeration, the refinement of petroleum, and various other low temperature processes. I don't think I'm wrong about how this works.

It sounds unbelievable, like the heat just "disappears" as the gas passes through the turbine, but it doesn't just disappear, it is CONVERTED into another form of energy to do work. The energy to do the work of turning the turbine comes from the expansion of the gas itself and and this causes the gas to become cold. Apparently it wants to expand so badly that it is willing to give up its own internal energy to do so even if it has to loose energy and push a turbine out of the way in the process.

Mr Skeptic · February 1, 2010

Can you give even one example of a turbine where the expansion of a compressed and chilled gas is used to produce, not consume, electricity?

Tom Booth · February 1, 2010

Can you give even one example of a turbine where the expansion of a compressed and chilled gas is used to produce, not consume, electricity?

I've read about many different applications. Generally speaking though, in most applications the turbo-expander is coupled to the compressor on the same shaft so that the power output from the turbine is used to reduce the load on the compressor.

Like I said previously, all this is contingent upon the efficiency of the compressor. Could a Stirling type displacer chamber actually compress air at all ? I don't really know. And at what kind of pressure and volume. I don't know that either. And at what efficiency...

But if a Stirling engine's displacer is able to deliver more power to a piston than it takes for the piston to drive a crankshaft which in turn drives the displacer as well as producing work in the process, I don't see why the same would not hold true for the same displacer being used to drive a turbine and having some of the power produced by the turbine in turn operating the displacer as well as doing work. You have eliminated a lot of the friction by eliminating the piston and crankshaft and rocker arms and what not and the turbine is supposed to be more efficient than a piston...

We are just moving heat around with this system and from what I understand about heat-pumps, it requires less energy input for the heat pump to simply transport heat to where it is needed than what it would take to provide the same amount of heat by some other method.

But all that is beside the point regarding the Turbo-expander.

Given a supply of compressed air a turbo-expander does produce a power output. It has to, as that is its function and the reason why the things are being used: To cool gases - to draw off the energy to get the gas cold enough for refrigeration or cold enough to liquefy. To do that it has to have a load of some kind, it has to be producing power so as to convert the heat energy in the gas into another form so that the gas gets cold.

In most cases the gas is not pre-cooled, but in other cases it is, so as to get even lower temperatures, like in cryogenics or liquefaction of gases. In most other applications pre-cooling is not necessary.

Whether it could produce enough cold to supply sufficient amounts of cold air to the displacer while still producing a surplus power output at the generator is a different issue.

Bottom line in regard to the turbo-expander is, it can and does produce both a power output and remove heat. It has to have a power output in order to remove heat. That is its usual function. This is particularly true in refrigeration and in the liquefaction of gases or other applications where extremely cold temperatures are needed where excess heat constitutes an unwanted "waste" product. In such applications the turbine is used to get rid of the unwanted heat very rapidly and efficiently by converting it into electricity and operating some redundant load just to carry away the excess heat.

That is what is needed here as well.

As you say,... if you are going to try to run something on ambient air temperatures, you might as well just toss it in a furnace...

Well, as I said earlier. This might be possible if you can find some way of getting rid of all the excess heat. Get rid of the heat, dump it somewhere far away. Create a cold spot and then keep that cold spot well insulated against any kind of unnecessary heat intrusion. If you can do that, and keep doing it fast enough and efficiently enough then you have a temperature differential to run your engine - drawing its energy from the surrounding heat of the "furnace" just a little at a time, and using just some of that heat to export the excess heat that might inadvertently find its way into the system.

This is what the expansion turbine does. It is an efficient means of exporting excess heat. The Stirling displacer set up is an efficient means of utilizing the resulting temperature differential.

Both the Stirling compressor unit AND the turbine are utilizing heat. The displacer uses some of the heat from the little bit of air that is let in to compress more air to run the turbine. The turbine uses what heat is left in the cooled air coming from the displacer to produce electricity, any additional excess heat can be removed by exposing some of the heating coils to cooler ambient temperatures at some point or by passing the coils through the cold exhaust. Once you use up all that heat energy you are left with very cold air, which is just the absence of heat.

Can the two working together get rid of the excess heat fast enough to keep each other operating ?

I'm not sure about that, but if they can, then much of the resulting "waste product" is usable electricity from the turbo-generator.

Naturally all this stuff would have to be balanced out and well insulated to maintain constant specified temperatures.

Personally, I'm thinking that all that is really needed to make this work is a lot of good insulation to prevent heat from infiltrating the system, Then your intake pipe coming from the outside hot air "furnace" is like a fuel line.

By converting the heat into electricity you can dump it far away somewhere through the electric lines powering some load - like the utility grid. You use the cold produced by the turbo-generator to keep your space air conditioned.

You can also dump some of the excess heat by exposing a portion of the heating coils (still above ambient temperature) to ambient temperature air and to the cold air exhaust after you have used as much heat as you need to operate the displacer/compressor. You don't want to leave any excess heat lying around as this would eventually reduce your temperature differential - you need to get rid of all the excess heat you don't use.

As far as the way the Turboexpander operates, just put "Turboexpander" into a search engine. or "liquefaction of gasses" or "air cycle refrigeration" or "air cycle machine" or "ACM" or "expansion turbine"

Here is a website that explains it fairly simply:

http://www.scienceclarified.com/Ga-He/Gases-Liquefaction-of.html

Regarding the use of the turbine for cooling the gas to temperatures cold enough for liquefaction:

----------------

"Methods of liquefaction

Making a gas work against an external force.

...The liquefaction of a true gas, therefore, requires two steps. First, the gas is cooled. Next, the cool gas is forced to do work against some external system. It might, for example, be driven through a small turbine... As the cooled gas pushes against the turbine blades, it makes the rod rotate. At the same time, the gas loses energy, and its temperature drops even further. Eventually the gas loses enough energy for it to change to a liquid."

http://www.scienceclarified.com/Ga-He/Gases-Liquefaction-of.html

-------------------------

This particular article doesn't mention that there has to be a load on the turbine, but I've read elsewhere that this is necessary. The turbine can't just freewheel.

Here is a You Tube video about the Air cycle system that talks about reducing the temperature of a gas by "making the gas to do work in an isentropic process".

I don't think I could provide you with any existing scenario that exactly matches what I'm trying to do here because as far as I'm aware nobody has ever considered this particular application mainly because there has never been any such thing as an efficient compressor, or any compressor for that matter that runs on a temperature differential. Most compressors draw so much power that the output of the turbine is not used for anything more than to reduce the load on the compressor.

The situation is the same for the expansion turbines used by industry. Generally, whatever process is going on usually requires a compressor of some sort and the power output from the turbine is used for nothing more than to reduce the load on the compressor, but there is a power output from the turbine - but with this system the energy needed to move the displacer is probably only a fraction of the energy that the turbine has to expend in overcoming the friction of its own bearings, no less helping to power a compressor.

I mean, maybe it can't work because there is too much back pressure or the turbine cant produce enough cold air or some other reason, like the "Stirling compressor" just won't work the way I imagine it might, but I don't think that there is any problem as far as the turbine simultaneously removing heat and doing work at the same time... that is what it does. That is why it is being used in countless applications right now, and has been for many years already.

That is a given.

This Wiki article gives many examples:

http://en.wikipedia.org/wiki/Turboexpander

Edited February 1, 2010 by Tom Booth
added Wiki link

Mr Skeptic · February 1, 2010

I've read about many different applications. Generally speaking though, in most applications the turbo-expander is coupled to the compressor on the same shaft so that the power output from the turbine is used to reduce the load on the compressor.

That does not follow.

But if a Stirling engine's displacer is able to deliver more power to a piston than it takes for the piston to drive a crankshaft which in turn drives the displacer as well as producing work in the process,

It doesn't.

We are just moving heat around with this system and from what I understand about heat-pumps, it requires less energy input for the heat pump to simply transport heat to where it is needed than what it would take to provide the same amount of heat by some other method.

A heat pump can transport heat in addition to the waste heat it produces from its energy input, whereas a simple heater does not have that first component.

Given a supply of compressed air a turbo-expander does produce a power output. It has to, as that is its function and the reason why the things are being used: To cool gases - to draw off the energy to get the gas cold enough for refrigeration or cold enough to liquefy. To do that it has to have a load of some kind, it has to be producing power so as to convert the heat energy in the gas into another form so that the gas gets cold.

If its function is to cool the gas then it follows that it requires a power input, and most definitely not an output. By lowering the pressure (doing work to do so) it will speed up evaporation and lower the temperature at which it evaporates, allowing it to reach a lower temperature more quickly.

An expanding gas gets cold regardless of whether any work is extracted from it.

---

But I grow bored of this. Pick up a basic book on thermodynamics and learn on your own.

npts2020 · February 1, 2010

TomBooth; Why wouldn't this engine work even better in a furnace? You have even greater potential temperature differential than at atmospheric values. The other thing I am not understanding is why your heat sink will not become the same as ambient after while and no longer give you the differential required to make it run? This is not a trivial matter for operation of any power generator and is usually done by pumping great volumes of water, air or some other coolant through the sink. You may claim all you like that there is some magical differential in temperature and pressure but there has to be a mechanism to create and maintain it. What you are describing does not do it.

Tom Booth · February 2, 2010

...in most applications the turbo-expander is coupled to the compressor on the same shaft so that the power output from the turbine is used to reduce the load on the compressor.

That does not follow.

It doesn't follow ? Maybe I'm reading it wrong somehow, but that seems to me to be what the references say.

But if a Stirling engine's displacer is able to deliver more power to a piston than it takes for the piston to drive a crankshaft which in turn drives the displacer as well as producing work in the process,

It doesn't.

What do you mean it doesn't ?

O.K. maybe it doesn't exactly "deliver" the power directly. It just controls the heat flow that makes the power available to drive the piston, itself and some external load... The power comes from the heat, but it only takes the displacer a minuscule amount of power to direct the flow of heat as compared with the resulting power output.

A heat pump can transport heat in addition to the waste heat it produces from its energy input, whereas a simple heater does not have that first component.

Granted, I suppose. But I don't know what your point is there.

If its function is to cool the gas then it follows that it requires a power input,

If the turbine had a power input it would be driving the gas or compressing the gas. Either way the gas would heat up as the energy would be transfered to the gas. When the gas is driving the turbine the energy is being transfered to the turbine.

and most definitely not an output.

It has to have an output, otherwise the gas wouldn't be doing any work and it wouldn't get cold. Not very cold anyway. The energy has to go somewhere.

By lowering the pressure (doing work to do so) it will speed up evaporation and lower the temperature at which it evaporates, allowing it to reach a lower temperature more quickly.

That is if you have a gas in a confined space or cylinder and you are drawing back the piston to lower the vacuum, or I suppose a turbine could also be used... if the turbine is sucking the gas up a tube or something. But if the turbine were sucking the gas up it would also be driving it out once the gas reached the turbine and then heat it back up in the process. What kind of "evaporation" are you talking about anyway ? How does a gas "evaporate" ? It's already a gas !

An expanding gas gets cold regardless of whether any work is extracted from it.

Right. and it gets even colder when it is made to do work at the same time.

But I grow bored of this. Pick up a basic book on thermodynamics and learn on your own.

Well, I provided you with the one example you requested. Several examples and additional references actually.

But maybe it won't work, who knows ? I just don't think it won't work for any of the reasons you have mentioned so far.

An expansion turbine is driven or powered by the expanding gas. The gas is being shot through a nozzle into the turbine, sometimes at sonic or supersonic speed causing it to rotate at tens of thousands of RPMs in some cases. The turbo-expander is not creating any kind of vacuum to speed up any sort of "evaporation".

Did you read the reference ?

quote: "As the cooled gas pushes against the turbine blades, it makes the rod rotate"

It says "The gas pushes against the turbine blades" not that the turbine blades push the gas"

Every other reference says the same thing. The gas drives the turbine not vice versa and the turbine driven by the expanding gas outputs power.

There is no reason to connect that power to the grid or anything when the power generated by the turbine can be used right on the spot to take the load off the compressor - usually coupled right to the same shaft as the compressor.

But if you no longer wish to discuss this, I'll just thank you for the time and attention you have given to this. It is most appreciated.

Thanks.

Tom

Merged post follows:

Consecutive posts merged

TomBooth; Why wouldn't this engine work even better in a furnace?

Who says it wouldn't ? I suppose it would, if encased in asbestos.

You have even greater potential temperature differential than at atmospheric values. The other thing I am not understanding is why your heat sink will not become the same as ambient after while and no longer give you the differential required to make it run?

This thing is basically a refrigeration system. You may be aware that some refrigerators operate on a heat source. Gas refrigerators for example.

It took me a long time for me to understand that myself - how does a hot gas flame make ice in an ice box ???? It makes no sense. Add heat and get cold ??? impossible !

Well, you use the heat to compress a gas. Under pressure, the gas heats up ABOVE AMBIENT TEMPERATURE. You can now use ambient temperature air to cool the pressurized gas. The gas is trapped in a narrow hollow tubular coil and you just allow convection to cool the coil.

Now when you allow the gas to expand into a larger tube, after having all that heat driven off, upon expanding to its former pressure and volume the gas tries to get the heat back, but now it is in a different area, now instead of being out in ambient temperature air it is in some pipe in a little insulated freezer box, but it draws as much heat out of the box as it can before moving along to another tube where it is re-heated by the flame.

Why doesn't the air inside a Gas freezer eventually return to ambient temperature? Especially when its input source of energy is a blue hot flame ?

This is not a trivial matter for operation of any power generator and is usually done by pumping great volumes of water, air or some other coolant through the sink.

Well, here your "sink" for your displacer chamber is the constant supply of air from the turbine which has had the heat removed from it by being compressed, cooled, allowed to expand and made to do work. This cold air constantly flows through the tubing in the displacer chamber which constitutes your heat sink. Any heat that this cold air picks up is then evacuated from the system back to the atmosphere where it heats up again.

You may claim all you like that there is some magical differential in temperature and pressure but there has to be a mechanism to create and maintain it. What you are describing does not do it.

I've just described how it does. at least in theory. The "pumping" of "great volumes of water, air or some other coolant through the sink." is accomplished by channeling the flow of cold air coming out from the turbine through your heat sink. which in this case is the tubing in the bottom of the displacer chamber.

But it isn't being "pumped" exactly. More like just being pushed along by the additional cold air coming out of the turbine behind it. There is no additional energy requirement for this "pumping", in fact, the turbine itself is being driven. The only real energy input into this system other than the hot air coming from the atmosphere is whatever it takes to move the displacer, which is insignificant compared with the power output from the turbine.

Theoretically anyway.

Edited February 2, 2010 by Tom Booth
fixed quote marks

Mr Skeptic · February 2, 2010

What do you mean it doesn't ?

O.K. maybe it doesn't exactly "deliver" the power directly. It just controls the heat flow that makes the power available to drive the piston, itself and some external load... The power comes from the heat, but it only takes the displacer a minuscule amount of power to direct the flow of heat as compared with the resulting power output.

Exactly. The temperature difference is the power source here, and the displacer is just a necessary power loss in the process. Without a temperature difference it just won't run.

If the turbine had a power input it would be driving the gas or compressing the gas. Either way the gas would heat up as the energy would be transfered to the gas. When the gas is driving the turbine the energy is being transfered to the turbine.

What I was thinking was speeding up the expansion or evaporation of a fluid, which would cool it. A gas does work expanding regardless of whether that work is used for anything, and will cool regardless. A turbine drawing power to force the gas to expand will cool it on that side, but compress it on the other so that it can release its heat on the other side.

It has to have an output, otherwise the gas wouldn't be doing any work and it wouldn't get cold. Not very cold anyway. The energy has to go somewhere.

A heat sink is needed even if you draw power from the gas.

That is if you have a gas in a confined space or cylinder and you are drawing back the piston to lower the vacuum, or I suppose a turbine could also be used... if the turbine is sucking the gas up a tube or something. But if the turbine were sucking the gas up it would also be driving it out once the gas reached the turbine and then heat it back up in the process. What kind of "evaporation" are you talking about anyway ? How does a gas "evaporate" ? It's already a gas !

A liquefied gas can evaporate, or a gas expand. Either way it will cool. The only way to cool it is to raise its temperature it via compression (or use something colder than it), so that it can release its heat energy.

An expansion turbine is driven or powered by the expanding gas. The gas is being shot through a nozzle into the turbine, sometimes at sonic or supersonic speed causing it to rotate at tens of thousands of RPMs in some cases. The turbo-expander is not creating any kind of vacuum to speed up any sort of "evaporation".

Did you read the reference ?

quote: "As the cooled gas pushes against the turbine blades, it makes the rod rotate"

It says "The gas pushes against the turbine blades" not that the turbine blades push the gas"

Every other reference says the same thing. The gas drives the turbine not vice versa and the turbine driven by the expanding gas outputs power.

Honestly, I hadn't read it; I just had taken your word for it that its purpose was to cool the gas... now I see it is not. It's purpose is to recover power. The gas will cool just fine without the expansion half of the turboexpander. The wiki says it gives an additional 6-15% efficiency though.

The reason I said that it did not follow that it supplies power from the fact that it is connected to the compressor is because depending on the relative sizes of the expansion and compression parts, it could instead be an additional draw of power.

But if you no longer wish to discuss this, I'll just thank you for the time and attention you have given to this. It is most appreciated.

No problem. I also used to enjoy designing perpetual motion machines of various types, and always learned something when I eventually figured out why it wouldn't work. It was great fun.

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