Introduction to Stirling Engines - University of Gavle

11/11/2007

UNIVERSITY

OF GÄVLE STIRLING ENGINE

MAIER Christoph

GIL Arnaud

AGUILERA Rafael

SHUANG Li

YU Xue

2 Stirling Engine

IndexIndexIndexIndex

Summary ........................................................................................................................ 3

Introduction .................................................................................................................... 4

History............................................................................................................................ 5

Presentation of Stirling Engines..................................................................................... 7

I. Stirling thermodynamic cycle ............................................................................. 7

II. Engine configurations ......................................................................................... 8

1. Alpha Stirling: ................................................................................................. 9

2. Beta Stirling................................................................................................... 11

3. Gamma Stirling ............................................................................................. 13

4. Other types .................................................................................................... 14

Reasons to use a Stirling Engine .................................................................................. 15

Analyze from Economic point ..................................................................................... 18

Applications of the Stirling power ............................................................................... 20

I. Cars ................................................................................................................... 20

II. Submarine ......................................................................................................... 21

III. Aircrafts ......................................................................................................... 22

IV. Heat and power System ................................................................................. 23

V. Cryocooler......................................................................................................... 24

VI. Nuclear power ............................................................................................... 24

VII. Solar Energy .................................................................................................. 25

Conclusion ................................................................................................................... 29

References .................................................................................................................... 31

Stirling Engine 3

SummarySummarySummarySummary

This essay mainly makes an exposition of the Stirling Engine. Firstly, the

history of Stirling Engine is showed to make a guide of first comprehension. Then the

Stirling Engine’s thermodynamic cycle is explained and the configuration is analyzed,

which we do to make sure a further insight into the Stirling Engine. After that, the

reasons to use a Stirling Engine are discussed, especially from an economic point of

view. This is to describe why the Stirling Engine is widely used in nowadays’ world.

And the last part is to show out how the Stirling Engine is applied in each field. But

with a special focus on sterling engines in applications with renewable energies. This

whole essay displayed a broad overall presentation to the Stirling Engine, and

analyzed its intrinsic value for the future.

4 Stirling Engine

IntroductionIntroductionIntroductionIntroduction

"…These imperfections have been in a great measure removed by time and especially by the genius of the distinguished Bessemer. If Bessemer Iron or steel had been known thirty five or forty years ago there is a scarce doubt that the air engine would have been a great success … It remains for some skilled and ambitious mechanist in a future age to repeat it under more favorable circumstances and with complete success…" (Written in the year 1876 by Dr. Robert Stirling [1790-1878])

The Stirling Engine was invented by Robert Stirling. This device was born as a

competence to the vapor machine, since a Stirling Engine works with smaller pressures than

the device created by Watt and it did not require a qualified train engineer. At the end of

s.XIX with the development of the internal combustion engine and the appearance of electric

engines, the machine of this study was forgotten.

Nowadays the technology that involves the invention of Robert Stirling is in

completely development because of the fact that now very useful applications are available.

This document travels in the history of this curious device looking for reasons of this

incredible development in this called high technology with its different applications and doing

an analysis from the point of view of the economy. This project explains the principle

function of the engine with a deep investigation. And we show how the Sterling Engine in

combination with renewable energy sources can be part of a sustainable energy supply.

Figure 1 : Sketch of Robert Stirling of his invent

Stirling Engine 5

HHHHistoryistoryistoryistory

The Stirling Engine is one of the hot air engines. It was invented by Robert Stirling (1790-1878) and his brother James. His father was interesting in engine and he inherited it. He became a minister of the church at Scotland in 1816. At this period, he found the steam engines are dangerous for the workers. He decided to improve the design of an existing air engine. He hope it wound be safer alternative. After one year, he invented a regenerator. He called the “Economiser” and the engine improves the efficiency. This is the earliest Stirling Engine. It is put out 100 W to 4 kW. But the internal combustion engine substituted for it quickly. The Ericsson invented the solar energy in 1864 and did some improvements for after several years. Robert’s brother, James Stirling, also played an important role in the development of Stirling engines.

Figure 2 : Earliest Stirling engine

Robert Stirling gets a patent for the economizer with an air engine incorporating it in 1817. Since the Stirling engine worked at a lower pressure, and could not cause steam burns, the danger to explode is impossible. In 1818 he built the first practical exponent of his engine, used to pump water from a quarry. The inventors sought to create a safer engine instead of steam engines at that time, whose boilers often exploded as a result of high pressure of the steam and the inadequate materials.

The original patent by Reverend Stirling was called the "economizer", for its improvement of fuel-economy. The patent also mentioned the possibility of using the

6 Stirling Engine

device in an engine. Several patents were later determined by two brothers for different configurations including pressurized versions of the engine. This component is now commonly known as the "regenerator" and is essential in all high-power Stirling devices.

Figure 3 : Stirling Engine’s principle of operation

Stirling engine of the second generation began in 1937.The Philips of Holland used new materials and technology to ascend a very high level. The knowledge about the heat transfer and fluid physical, which is a great significance to improving of the structure and raised the stability.

Throughout World War II and by the late 1940s, Philips’ subsidiary Johan de Witt does this work continued. And they did the Type 10, incorporated into a generator set as originally planned The set progressed through three prototypes (102A, B, and C), with the production version, rated at 200 watts electrical output from a bore and stroke of 55x27mm, being designated MP1002CA.

In 1951, the price of Stirling engine is too high for the market. It made used of radios at that time. Though the MP1002CA may have been a dead end, it represents the blooming of the modern age of Stirling Engine development. In addition to which the advent of transistor radios with their much lower power requirements meant that the market for the set was fast disappearing. Though the MP1002CA may have been a dead end, it represents the start of the modern age of Stirling engine development.

Stirling Engine

Presentation of Stirling Presentation of Stirling Presentation of Stirling Presentation of Stirling

I. Stirling thermodyna

The Stirling engine

fixed mass of gas called the "working fluid" (air, hydrogen or helium). The principle is that of thermal expansion and contraction of this fluid due to a temperature differential.

So the ideal Stirling cycle consists of four thermodynamicacting on the working fluid:volume processes.

Each one of which can be separately analysed:

� 1-2: isothermal compression processfluid, while an equal amount of heat Qcooling source. The working fluid cools and contracts at constantTC.

� 2-3: constant volume displacement process with heat additionabsorbed by the working fluid and temperature is raised from Twork is done.

� 3-4: isothermal expansion processwhile an equal amount of heat Qsource. The working fluid heats and expands at constant temperature T

� 4-1: constant volume displacement process with heat rejectionrejected by the working fluid work is done.

Figure

Stirling Engine


EnginesEnginesEnginesEngines

Stirling thermodynamic cycle

The Stirling engine cycle is a closed cycle and it contains, most commonly a fixed mass of gas called the "working fluid" (air, hydrogen or helium). The principle

ansion and contraction of this fluid due to a temperature

So the ideal Stirling cycle consists of four thermodynamics distinct processes fluid: two constant-temperature processes and two constant

ch one of which can be separately analysed:

isothermal compression process. Work W1-2 is done on the working fluid, while an equal amount of heat Q1-2 is rejected by the system to the cooling source. The working fluid cools and contracts at constant

onstant volume displacement process with heat additionabsorbed by the working fluid and temperature is raised from T

isothermal expansion process. Work W3-4 is done by the working fluidwhile an equal amount of heat Q3-4 is added to the system from the heating source. The working fluid heats and expands at constant temperature T

constant volume displacement process with heat rejectionrejected by the working fluid and temperature decrease from T

Figure 4 : A pressure/volume graph of the ideal Stirling

cycle

7


it contains, most commonly a fixed mass of gas called the "working fluid" (air, hydrogen or helium). The principle

ansion and contraction of this fluid due to a temperature

distinct processes temperature processes and two constant-

is done on the working is rejected by the system to the

cooling source. The working fluid cools and contracts at constant temperature

onstant volume displacement process with heat addition. Heat Q2-3 is absorbed by the working fluid and temperature is raised from TC to TH. No

is done by the working fluid, is added to the system from the heating

source. The working fluid heats and expands at constant temperature TH. constant volume displacement process with heat rejection. Heat Q4-1 is

and temperature decrease from TC to TH. No

8 Stirling Engine

The process lines in the figure above reflect the properties of an ideal gas. The main processes, like for most heat engines, are cooling, compression, heating and expansion. A Stirling engine operates through the use of an external heat source and an external heat sink having a sufficiently large temperature difference between them.

Compared to the ideal cycle, the efficiency of a real engine is reduced by

irreversibilities, friction, and the loss of short-circuit conducted heat, so that the overall efficiency is often only about half of the ideal (Carnot) efficiency.

The gasses used inside a Stirling engine never leave the engine. There are no exhaust valves that vent high-pressure gasses, as in a gasoline or diesel engine, and there are no explosions taking place.

Another useful characteristic of the Stirling engine is that if supplied with mechanical power, it can function as a heat pump (reversibility of the Stirling cycle).

Understanding how a Stirling engine works is not a simple matter. It is not overly intuitive. Let’s explain the device through the presentation of the different engines configuration.

II. Engine configurations

Mechanical configurations of Stirling engines are classified into three

important distinct types: Alpha, Beta and Gamma arrangements. These engines also feature a regenerator (invented by Robert Stirling). The

regenerator is constructed by a material that conducts readily heat and has a high surface area (a mesh of closely spaced thin metal plates for example).

When hot gas is transferred to the cool cylinder, it is first driven through the

regenerator, where a portion of the heat is deposited. When the cool gas is transferred back, this heat is reclaimed. Thus the regenerator “pre heats” and “pre cools” the working gas, and so improve the efficiency.

But many engines have no apparent regenerator like beta and gamma engines

configurations with a “loose fitting” displacer, the surfaces of the displacer and its cylinder will cyclically exchange heat with the working fluid providing some regenerative effect.

Stirling Engine 9

1. Alpha Stirling:

Alpha engines have two separate power pistons in separate cylinders which are connected in series by a heater, a regenerator and a cooler. One is a “hot” piston and the other one a “cold piston”.

The hot piston cylinder is situated inside the high temperature heat exchanger

and the cold piston cylinder is situated inside the low temperature heat exchanger. The generator is illustrated by the chamber containing the hatch lines.

Figure 5 : Alpha engine’s configuration

Expansion: At this point, the most of

the gas in the system is at the hot piston

cylinder. The gas heats and expands,

pushing the hot piston down, and

flowing through the pipe into the cold

cylinder, pushing it down as well.

Transfer: At this point, the gas has expanded. Most of the gas is still in the hot cylinder. As the crankshaft continues to turn the next 90°, transferring the bulk of the gas to the cold piston cylinder. As it does so, it pushes most of the fluid through the heat exchanger and into the cold piston cylinder.

10

The Alpha engine is c

however suffers from the disadvantage that both pistons need to have seals to contain the working gas.

Contraction: Now the majority of the expanded gas is shifted to the cool cylinder. It cools and contracts, drawing both pistons up

Figure 6 : Example of a real cycle of an

Stirling Engine

This diagram is feature of an alpha engine.

The most important is to have the biggest

grey area which represents

recuperated work during a cycle.

The Alpha engine is conceptually the simplest Stirling engine configuration, however suffers from the disadvantage that both pistons need to have seals to contain

Now the majority of the shifted to the cool piston

It cools and contracts, drawing

Transfer: The fluid is cooled and ncrankshaft turns another 90°.therefore pumped back, through the heat exchanger, into the hot piston Once in this, it is heated and we go back to the first step.

alpha engine

This diagram is feature of an alpha engine.

The most important is to have the biggest

area which represents the

recuperated work during a cycle.

onceptually the simplest Stirling engine configuration, however suffers from the disadvantage that both pistons need to have seals to contain

The fluid is cooled and now the shaft turns another 90°. The gas is

therefore pumped back, through the heat the hot piston cylinder.

it is heated and we go back

Stirling Engine

This type of engine has a very high powerproblems due to the usually high temperature of the "hot" piston and its seals

2. Beta Stirling The Beta configuration is the classic Stirling engine configuration and has

enjoyed popularity from its inception until today. Stirling's original engine from his patent drawing of 1816 shows a Beta arrangement.

Both Beta and Gamma engines use displacer

engine has both the displacer and the piston in an inengine uses separate cylinders.

The purpose of th

working gas at constant volume, and shuttle it between the expansion and the compression spaces through the series arrangement cooler, regenerator, and heater.

A beta Stirling has a single power p

the same shaft as a displacer piston. The displacer piston is a loose fit and does not extract any power from the expanding gas but only serves to shuttle the working gas from the hot heat exchanger to the cold heat exchanger.

When the working gas is pushed to the hot

end of the cylinder it expands and pushes the power piston. When it is pushed to the cold end of the cylinder it contracts and the momentum of the machine, usually enhanced by a flywheel, pushes thecompress the gas. Unlike the alpha type, the beta type avoids the technical problems of hot moving seals.

Stirling Engine

This type of engine has a very high power-to-volume ratio but has technical usually high temperature of the "hot" piston and its seals

The Beta configuration is the classic Stirling engine configuration and has enjoyed popularity from its inception until today. Stirling's original engine from his

1816 shows a Beta arrangement.

Both Beta and Gamma engines use displacer-piston arrangements. The Beta engine has both the displacer and the piston in an in-line cylinder system. The Gamma engine uses separate cylinders.

The purpose of the single power piston and displacer is to “displace” the working gas at constant volume, and shuttle it between the expansion and the compression spaces through the series arrangement cooler, regenerator, and heater.

A beta Stirling has a single power piston arranged within the same cylinder on the same shaft as a displacer piston. The displacer piston is a loose fit and does not extract any power from the expanding gas but only serves to shuttle the working gas from the hot heat

at exchanger.

When the working gas is pushed to the hot end of the cylinder it expands and pushes the power piston. When it is pushed to the cold end of the cylinder it contracts and the momentum of the machine, usually enhanced by a flywheel, pushes the power piston the other way to compress the gas. Unlike the alpha type, the beta type avoids the technical problems of hot moving seals.

Figure 7 : Beta engine’s configuration

Figure

11

volume ratio but has technical usually high temperature of the "hot" piston and its seals

The Beta configuration is the classic Stirling engine configuration and has enjoyed popularity from its inception until today. Stirling's original engine from his

piston arrangements. The Beta line cylinder system. The Gamma

e single power piston and displacer is to “displace” the working gas at constant volume, and shuttle it between the expansion and the compression spaces through the series arrangement cooler, regenerator, and heater.

iston arranged within the same cylinder on the same shaft as a displacer piston. The displacer piston is a loose fit and does not

Figure 8 : Beta engine

with momentum

flywheel

12 Stirling Engine

Expansion: At this point, most of the gas in the system is at the heated end of the cylinder. The gas heats and expands driving the power piston outward.

Transfer: At this point, the gas has expanded. Most of the gas is still located in the hot end of the cylinder. Flywheel momentum carries the crankshaft the next quarter turn. As the crank goes round, the bulk of the gas is transferred around the displacer to the cool end of the cylinder,

driving more fluid into the cooled end of the

cylinder.

Contraction: Now the majority of the expanded gas has been shifted to the cool end. It contracts and the displacer is almost at the bottom of its cycle.

Transfer: The contracted gas is still located near the cool end of the cylinder. Flywheel momentum carries the crank another quarter turn, moving the displacer and transferring the bulk of the gas back to the hot end of the cylinder. And at this point, the cycle repeats.

Stirling Engine

3. Gamma Stirling

A gamma Stirling is simply a beta Stirling in which

mounted in a separate cylinder alongside the displacer piston cylinder, but is still

connected to the same flywheel. The gas in the two cylinders can flow freely between

them and remains a single body. This configuration produces a lowe

ratio but is mechanically simpler and often used in multi

Gamma type engines have a displacer and power piston, similar to Beta machines, but

in different cylinders. This allows a convenient complete separation betw

exchangers associated with the displacer cylinder and the compression and expansion

work space associated with the piston.

Furthermore during the expansion process some of the expansion must take

place in the compression space leading to a

engines are therefore used when the advantages of having separate cylinders outweigh

the specific power disadvantage.

The advantage of this design is that it is mechanically simpler because of the

convenience of two cyli

Stirling Engine

A gamma Stirling is simply a beta Stirling in which the power piston is



them and remains a single body. This configuration produces a lowe

ratio but is mechanically simpler and often used in multi-cylinder Stirling engines.


in different cylinders. This allows a convenient complete separation betw


work space associated with the piston.


place in the compression space leading to a reduction of specific power. Gamma


the specific power disadvantage.


convenience of two cylinders in which only the piston has to be sealed. The

Figure 10 : Gamma engine’s configuration

Figure 9 : Example of a real cycle of a beta

engine

13

the power piston is



them and remains a single body. This configuration produces a lower compression

cylinder Stirling engines.


in different cylinders. This allows a convenient complete separation between the heat



reduction of specific power. Gamma



nders in which only the piston has to be sealed. The

14

disadvantage is the lower compression ratio but the gamma configuration is the

favorite for modelers and hobbyists.

4. Other types

Changes to the configuration of mechanical Stirling engiinterest engineers and inventors who create a lot of different version of the engine.

There is also a large

those with liquid pistons and those with diaphragms as pistons.

For example, as an alternative to the mechanical Stirling engine is the fluidyne pump, which uses the Stirling cycle via a hydraulic piston. In its most basic form it contains a working gas, a liquid and two nonfluidyne goes into pumping the liquid.

Figure 12 : Example of a real cycle of a

beta engine

Stirling Engine


and hobbyists.

.

Changes to the configuration of mechanical Stirling engines continue to interest engineers and inventors who create a lot of different version of the

large field of "free piston" Stirling cycles engines, including those with liquid pistons and those with diaphragms as pistons.

For example, as an alternative to the mechanical Stirling engine is the fluidyne pump, which uses the Stirling cycle via a hydraulic piston. In its most basic form it contains a working gas, a liquid and two non-return valves. The work produced by the luidyne goes into pumping the liquid.

Figure 11 : Small gamma engine

: Example of a real cycle of a


nes continue to interest engineers and inventors who create a lot of different version of the Stirling

field of "free piston" Stirling cycles engines, including

For example, as an alternative to the mechanical Stirling engine is the fluidyne pump, which uses the Stirling cycle via a hydraulic piston. In its most basic form it

return valves. The work produced by the

: Small gamma engine

Stirling Engine 15

Reasons to use a Stirling Reasons to use a Stirling Reasons to use a Stirling Reasons to use a Stirling

EngineEngineEngineEngine

There are several reasons to use a Stirling Engine:

� One reason is that for this kind of engine it’s almost impossible to explode. You don’t have to produce steam in a high pressure boiler. And inside the cylinder there are no explosions needed to run the pistons like in an Otto or Diesel engine. There are no ignitions, no carburetion because you only need one kind of gas and no valve train because there are no valves. This was a big advantage to the steam engines in the days when Stirling invented his engine because it was much less dangerous to work next to a Sterling Engine than to a common steam engine.

� Inside the pistons can be used air, helium, nitrogen or hydrogen and you don’t have to refill it because it uses always the same body of gas.

Figure 13 : Schematic Stirling Engine

16 Stirling Engine

� To produce heat you can use whatever you want: fuel, oil, gas, nuclear power and of course renewable energies like solar, biomass or geothermal heat.

Figure 14 : Solar panel

� The external combustion process can be designed as a continuous process, so the most types of emissions can be reduced.

� If heat comes from a renewable energy source they produce no emissions.

� They run very silent and they don’t need any air supply. That’s why they are

used a lot in submarines. E.g. in the Royal Swedish Navy.

Figure 15 : Figure 16 Gotland : HMS

Stirling Engine 17

� They can be constructed to run very quiet and practically without any vibration.

� They can run with a small temperature difference, e.g. with the heat of your hand or from a cup of hot coffee. They can be used as little engines for work which needs only low power.

� They can run for a very long time because the bearings and seals can be placed at the cool side of the engine → they need less lubricant and they don’t have to be checked very often ( longer period between the overhauls ).

� They are extremely flexible. The engine can run as a CHP (combined heat and power) because the heat which is produced to run it can easily be collected. Or in summers they can be used as coolers.

Figure 16 : Low power Stirling engine

Figure 17 : CHP

18

Analyze from Economic pointAnalyze from Economic pointAnalyze from Economic pointAnalyze from Economic point

As said above the Stirling engine is a kind of external combustion engine, and

it can use a variety of fuels. It ca

material, including gasoline, diesel, propane, sunshine and salad oil; even cow dung

can be run on as fuels.

A cup of coffee cannot become a cup of gasoline, but it can be also used as a

Stirling engine driver. There is a famous experiment that a Stirling engine can easily

run on a cup of coffee. The Stirling engine is a kind of piston engine. In the

heating sealed chamber, the expansion of gases inside the engine promotes the pistons

work. After the expanded gases cooling down in the air

process is taking on. As long as a certain value of the temperature difference exists, a

Stirling Engine can be formed.

Figure

This experiment shows that only a very small power operation can carry out a

Stirling engine, which contributes a lot to

especially shows out on economy point. The benefits obtained from the Stirling

engine are definitely far beyond the costs.

So once solar is used to produce energy for

surely be cut down for quite a lot. As long as there is sunshine, the Stirling engine will

run on and on. Of course it costs much to ma

Stirling Engine


he Stirling engine is a kind of external combustion engine, and

it can use a variety of fuels. It can be estimated that combustible gases are the best



iver. There is a famous experiment that a Stirling engine can easily

run on a cup of coffee. The Stirling engine is a kind of piston engine. In the


he expanded gases cooling down in the air-conditioned room, next


Stirling Engine can be formed.

Figure 18 : Stirling Engine working on a cup of coffee


Stirling engine, which contributes a lot to energy conservation. This characteristic


ne are definitely far beyond the costs.

So once solar is used to produce energy for the Stirling engine, the cost would


Of course it costs much to manufacture a Stirling engine, as it requires


he Stirling engine is a kind of external combustion engine, and

n be estimated that combustible gases are the best



iver. There is a famous experiment that a Stirling engine can easily

run on a cup of coffee. The Stirling engine is a kind of piston engine. In the external


conditioned room, next



energy conservation. This characteristic


the Stirling engine, the cost would


nufacture a Stirling engine, as it requires

Stirling Engine 19

a high level of the materials and manufacturing processes. The expansion-side heat

exchanger’s temperature is often very high, so the materials must stand the corrosive

consequences of the heat. Typically these material requirements substantially increase

the cost of the engine. The materials and assembly costs for a high temperature heat

exchanger typically accounts for 40% of the total engine cost.

But once the Stirling engine is made and put into a proper condition, quite a

few costs would be paid for keeping it running.

Some engines cause a lot of pollution, so much is cost for pollution control

and government. On contrast, Stirling engine exhausts cleanly and avoid this type of

matter. Development and utilization of solar will not pollute the environment, as solar

is one of the cleanest energy. While the environmental pollution is becoming more

and more serious today, this characteristic is extremely valuable. It saves the cost for a

lot while making sustainable development.

At the end of 18th century and the early 19th century, heat engine generally is

steam engine. Its efficiency is very low, only 3% to 5%, that is, over 95% of the heat

is not used. Stirling thermodynamic theory is aiming to improve the thermal

efficiency. Stirling proposed that the Stirling cycle efficiency, under the ideal

condition, may get the infinite enhancement. Certainly it cannot come to 100% due to

the physical limitation, however the theory provide a direction for improving the

thermal efficiency. In fact, now the efficiency of Stirling engine can come up to 80%

or even more. So another part of cost is saved.

Nowadays, more and more countries have recognized that a society with

sustainable development should be able to meet the needs of the community without

endangering future generations. Therefore, use clean energy as much as possible

instead of the high carbon content of fossil energy is a principle which should be

followed during energy construction. Vigorously develop new and renewable sources

of energy utilization technology will be an important measure to reduce pollution.

Energy problem is a worldwide one, and it is sooner or later to get into the transition-

to-new-energy period. Because of its sustainability, renewably and efficiency, the

Stirling engine is just the very one being consistent with the requirements of the

times.

20 Stirling Engine

Applications of the Stirling Applications of the Stirling Applications of the Stirling Applications of the Stirling

powerpowerpowerpower

I. Cars

In the ages of 1970s and 1980s several automobile companies like “General

Motors” or “Ford” were researching about Stirling Engine. This device is good for a

constant power setting, but it is a challenge for the stop and go of the automobile.

A good car can change the power quickly. One possibility to obtain this

important characteristic is design a power control mechanism that will turn up or

down the burner. This is a slow method of changing power levels because is not

enough to accelerate crossing an intersection.

The best solution in spite of these difficulties in automobiles is hybrid electric

cars where Stirling Engine could give enough power to make long trips where could

get burn gasoline or diesel, depending on which fuel was cheaper. The batteries could

give the instant acceleration that

drivers are used to. This invention

makes the car silent and clean

running.

On March 20, 2002 I

delivered one of our KY-2000

Stirling engines to the Mechanical

Engineering department at San

Diego State University. While I was

there I had the opportunity to see

their hybrid diesel/electric car. It has

a 60 hp diesel engine and a 200 hp

electric motor. The extra power

(above 60 hp) for the electric motor

is of course supplied by the batteries

when needed.“ Brent Van Arsdell",

March 21, 2002.

Figure 19 : Hybrid car designed by GM 1

Stirling Engine 21

II. Submarine

“Kockums”, a Swedish defense contractor, produce Stirling Engines for the

navy making the quietest submarines in the world.

This high-technology is named air-independent propulsion (AIP). There are

four submarines equipment with Stirling AIP. The models are HMS Näcken, which

was launch in 1978 and after ten years 1988 became the first submarine equipped with

AIP system, by means of a cut and lengthened by an intersection of a Stirling AIP

section, which before the installation is equipped by two Stirling units, liquid oxygen

(LOX) tanks and electrical equipment.

Successful demonstration of AIP system during many routine patrols of HMS

Näcken made that Gotland, another type of submarine, was the first submarine

designed from the beginning to operate with AIP system.

The other four submarines that operates with this technology are two

Söderman class were upgraded by 2004.

If the Stirling was designed to operate at ambient

pressure (and had a valve system to ensure such) then it

could be enclosed in a small bubble of gas that would

slowly be crushed by the pressure of the ocean and

increase the internal working volume of gas to a level that

could not be easily achieved at sea level. With such

enormous internal pressure the power output would be

huge!

“ Mick Viner, June 23, 2002”

Figure 20 : AIP system

Figure 21 : Stirling engine in Näcken

22 Stirling Engine

III. Aircrafts

In relation about Stirling engines in aircraft, the communities near airports

could benefit from the quiet engine. Unlike other types of aircrafts this kind of

aircrafts increases the performance climbs to altitude.

Like is showed above vibration is an area that Stirling excel. The shaft torque

on four cylinders varies from 100% negative to 350% positive in each revolution.

Only 5% of variation characterised the quiet engine obviously increasing the comfort

of occupants as well as airframe fatigue is greatly reduced and isolator’s materials.

Less vibration is good advantage for

the propeller in means of torque,

nowadays the propeller is designed

considering the pulse of torque As

long as the prop is also the flywheel

it must be heavy and robust.

Usually the first failure is the

ignition system, in the Stirling the

ignition is necessary at the beginning

to start the fire after is not needed.

Another hamper is eliminated

Figure 22 : Torque-Crankshaft Angle

Figure 23 : Altitude-Airspeed

Stirling Engine 23

without valves. In the following graph it is possible see that the performance of the

Stirling engine increases with altitude because the system is sealed without reference

of ambient air density. As the outside temperature declines, engine power increases.

This compounds the natural ability of the aircraft to fly faster as air density decreases.

Stirling allow the plane to cruise above the weather rather than trough it thus it

is a safety aspect because there are many accidents because the weather. In addiction,

the possibility of the pilot to choose the altitude could benefit the optimize use of the

winds.

There are several reasons for the superior fuel economy. First, the Stirling is a

much more efficient powerplant. An internal combustion engine takes in new air and

fuel for each stroke, saving nothing from the previous one. But the Stirling re-uses the

same heat energy on successive strokes; the fuel is only needed to make up the losses.

The second reason is that the fuel is always burned full lean, at the best air/fuel ratio,

while normal aircraft engines actually use gasoline as a coolant. The Stirling also

uses the exhaust from the burner to preheat the incoming combustion air. Since the

Stirling exhaust is cool, it is obvious that less energy is being thrown away.

“Darryl Philip, April 1993”

IV. Heat and power System

This device replaces traditional boilers in houses. It is an innovative system

developed to provide central heating, water heating and electricity.

Usually this device is called “Micro Combined

Heat and Power (CHP)” and produces much less

carbon dioxide than other ways of providing heat and

power. In fact, if the level of CHP was increased to the

Government's target of 10,000 MW, the UK could be

one third of the way to meeting its international

commitments to reduce carbon dioxide emissions.

“...We can combine the building of homes with

building communities with combined heat and

power...”

“Rt Hon Gordon Brown MP, Prime Minister” Figure 24 : AC Whisper Gen

24 Stirling Engine

The company Whisper Gen has launched to the market the market MkV AC

gas fired that consists in four cylinders with double acting Stirling cycle. It is possible

coach heat output from 7.5-12KW at 220-240V

Benefits: • Savings through the production of own electricity. • Reduce emissions of CO2 and other emissions. • Avoiding peak-load costs when the network is overloaded. • Allows for rapid introduction of new generation capacity.

The performance is over 90% of the fuel energy resulting in a cleaner and

more cost effective alternative to traditional electricity generation. Electricity

generated can be fed back into the electricity grid or used in the home, reducing

electricity costs even further. Invent provides an average household with a saving of

about £150 per year. It also reduces carbon dioxide emissions by up to 1.5 tonnes per

year, a real contribution towards tackling the effects of global warming. That’s 20%

less carbon dioxide per household.

V. Cryocooler

If It is applied mechanical energy instead of cold and heat sources by means of

external engine, It is possible reach temperatures like 10 K (-263°C) in machines of

high technology.

The first Stirling-cycle cryocooler was developed at Philips in the 1950s and

commercialized in such places as liquid nitrogen production plants. This company is

still active in the development and manufacturing Stirling cryocoolers and cryogenic

cooling systems.

A wide variety of smaller size Stirling cryocoolers are commercially available

for tasks such as the cooling of sensors.

Thermoacoustic refrigeration uses a Stirling cycle in a working gas which is

created by high amplitude sound waves.

VI. Nuclear power

Steam turbines of a nuclear plan can be replaced by Stirling engine thus reduce

the radioactive by-products and be more efficient. Steam plants use liquid sodium as

Stirling Engine 25

coolant in breeder reactors, water/sodium exchanger are required, which in some

cases that temperature increase so much this coolant could reacts violently with water.

NASA has developed a Stirling Engine known as Stirling Radioisotope (SRG)

Generator designed to generate electricity in for deep space proves in lasting

missions. The heat source is a dry solid nuclear fuel slug and the cold source is space

itself. This device converter produces

about four times more electric power

from the plutonium fuel than a

radioisotope thermoelectric generator.

These generators have been

extensively tested but have not yet

been deployed on actual missions.

Thus each SRG will utilise two

Stirling converter units with about 500

watts of thermal power supplied by

two GPHS (General Purpose Heat

Source) units and will deliver 100-120 watts of electric power. Each GPHS contains

four iridium-clad Pu-238 fuel pellets, stands 5 cm tall, 10 cm square and weighs 1.44

kg. The hot end of the Stirling converter reaches 650°C.

The power output of the generator will be greater than 100 W at the beginning

of life, but the wear out of plutonium decrease the heat source. However control

system allows long life.

VII. Solar Energy

Placed at the focus of a parabolic mirror a Stirling engine can convert solar

energy to electricity with efficiency better than non-concentrated photovoltaic cells.

In 2005 It is created a 1 kW Stirling generator with a solar concentrator, this was a herald of the coming of a revolutionary solar, nowadays It generates electricity much more efficiently and economically than Photovoltaic (PV) systems whit technology called concentrated solar power (CPS). Nowadays the company Infina Applications has development a 3 kW Solar Stirling Product.

Figure 25 : Conceptual design of the SRG by Lockheed

26

Some companies areglass in the same low cost manufacturing techniques used to make consumer products. The equipment is well characterized with ove

This technology is the world´s most efficiency for the conversion of solar energy to grid delivery electricity, roughly twice as efficient of the others alternative solar technologies.

By a mirror to focus the sun’s rays onreceiver end of a Stirling engine. The internal side of the receiver then heats hydrogen gas, which expands. The pressure created by the expanding gas drives a piston, crank shaft, and drive shaft assembly much like those found in internal combustion igniting the gas. The drive shaft is connected to a small

electricity generator.

This solar application is called significant potential grid for water pumping or electrification.

In California there is a big contract where the

approximately 1.4 percent to 2.6 percent of

Figure

Stirling Engine

are launching technology using steel, cooper, aluminium and glass in the same low cost manufacturing techniques used to make consumer products. The equipment is well characterized with over 25,000 hours of on-sun time.

This technology is the world´s most efficiency for the conversion of solar energy to grid delivery electricity, roughly twice as efficient of the others alternative

By a mirror to focus the sun’s rays on the receiver end of a Stirling engine. The internal side of the receiver then heats hydrogen gas, which expands. The pressure created by the expanding gas drives a piston, crank shaft, and drive shaft assembly much like

found in internal combustion engines but without igniting the gas. The drive shaft is connected to a small

This solar application is called concentration solar power (CSP)significant potential grid for water pumping or electrification.

here is a big contract where the electrical output represents from approximately 1.4 percent to 2.6 percent of Edison’s annual sales.

Figure 26 : Solar Dynamic Brayton Schematic

Figure 27 : Solar

Schematic

launching technology using steel, cooper, aluminium and glass in the same low cost manufacturing techniques used to make consumer products.

sun time.

This technology is the world´s most efficiency for the conversion of solar energy to grid delivery electricity, roughly twice as efficient of the others alternative

concentration solar power (CSP) and is

electrical output represents from

: Solar Dynamic Brayton

Schematic

Stirling Engine 27

Seller Gen. Type

Initial Size (MW)

Possible Expansion Size (MW)

Estimated Annual Energy Based on Initial Size (GWH)

Estimated Annual Energy Based on Expansion Size (GWH)

Initial Phase On-Line Date

Completion Date for Initial Size

Term of Agreement (Years)

Estimated Capacity Factor

SES Solar One LLC

Solar Thermal (Stirling Dish)

500 850 1,047 1,780 Jan. 2009

Dec. 2012 20 23.90 percent

Tabla 1: www.stirlingenergy.com/breaking_news.htm

Next year the Stirling solar dish will be able to be in the market, therefore high capacity to produce energy with the power of sun helping to reduce emissions of CO2 gases.

It is possible nowadays dream with CHP plants working with Stirling Engines

and it is expected that this technology will be commercially available within the next few years.

Electric power output - Stirling engine KW 35 70

Thermal power output - Stirling engine kW 105 210

Thermal power output - CHP plant kW 230 460

Fuel power input (based on NCV) kW 300 600

Electric efficiency - Stirling engine % 25,0 25,0

Overall electric efficiency - CHP plant % 11,7 11,7

Overall efficiency - CHP plant % 88,3 88,3

Working gas

Helium Helium

Mean pressure Pa 4,5 4,5

Temperature of hot heat exchanger C 750 750

Revolution speed pm 1.010 1.010

Engine weight kg 1.600 3.500 Tabla 2: www.stirling.dk/default.asp?ID=120

NASA uses an advanced system to concentrate the sunlight. Waste heat is

removed through a heat exchanger and dissipated by radiator panels to space. The

power and distribution system is based on the closed Brayton cycle. A recuperative

heat exchanger between the turbine discharge and receiver inlet is used to improve

28 Stirling Engine

cycle efficiency. Long life is made possible through the use of non-contacting gas

bearings, hermetic sealing of the gas circuit, redundant electronic components, and

ultraviolet/atomic oxygen protective coatings on all optical surfaces. Radiation

degradation is reduced relative to solar photovoltaic arrays since semi-conducting

materials are not used on the large exposed surfaces.

Figure 28 : Solar Dynamic Brayton Schematic

Stirling Engine 29

ConclusionConclusionConclusionConclusion

Stirling engines qualify for “free energy” designation when they allow us to

tap previously inaccessible sources of naturally occurring energy. Stirling cycle engines are very efficient for a given temperature difference between the heat source and the heat sink. Actually, steam engines (the Rankine cycle) fall into this category, too. But depending upon what kind of hardware and its maintenance you prefer, one or the other will be preferred. Steamers have fewer parts and higher power density. Other fluids, such as a variety of refrigerants, can be used instead of water. Stirlings avoid fluid containment problems, as they can run with air as the working fluid, and will have less maintenance issues.

Stirling Engines are very flexible. There are a lot of different types of engines. They can be very small and run with only a small temperature difference, they are very quiet, for example to use them in submarines or they can be used as a CHP plant.

Another good point is that they can be constructed in a way that they produce no emissions. That means, in combination with solar or geothermal heat, they can be used as a renewable energy source to produce electricity.

As is showed above, the Stirling engine has strong economic practicality. Above all, the original cost is quite lower than for any other engines. Even a few calories can drive it and keep it running. The next point is that the auxiliary costs are low, because the Stirling engine costs little on environment protection. The fuels it uses can be clean, so it costs little to handle with pollution governance. What is more, the profit of the Stirling engine is far beyond the cost. And the high efficiency can bring the maximum utilization. And last but not least, the Stirling engine is consistent with the requirements of sustainable development. It is the main development way in the future, so the Stirling engine does not only meet the economic needs at present time, but also in the future.

The Stirling engine is an interesting device like it is showed in this document

with various applications and high development. Its advantages are really beneficial for the environment because it is possible produce electricity with the power of sun with high efficiency (theorically like the Carnot Cycle). It is a huge advantage to the economy because is possible to burn the cheapest fuel and it is working instead of the more expensive one. And this engine is comfortable for the people because is quiet and not noisy like an internal combustion engine.

30 Stirling Engine

The real renewable energy is the solar application for this device because the

other ways to produce the heat source are burning something. It is possible to

decrease the emissions of CO2 or other toxic gases but not eliminate completely this

problem for the earth and therefore for humans. This application could be one of the

different ways to solve the problem of greenhouse gas emissions and to continue and

also to develop our comfort.

In all applications that was showed in this presentation the performance the

devices are better, obviously increase the efficiency is good

Depend of which kind of fuel is getting burn in process. The Stirling Engine is

a machine of external combustion thus if it is burned fuel the emissions of CO2 is not

solved. It is showed that the performance is better but in the point of view of

environment the real problem continues existing.

Find a heat source to make it works, this is the case of biomass fuels in

connection with a Stirling engine are concentrated on transferring the heat from the

combustion of the fuel into the working gas and in the same way the solar application.

Because, as companies look increasingly to alternative power units, it is entirely possible that the Stirling engine will find its own niche in the marketplace, perhaps as part of a hybrid power plant, or through further development and optimization. No high-tech materials are needed. This competes with solar cells.

Taking one with another, Stirling engine bring a tremendous revolution to human being. We think there is also a lot of potential in this area because modern industrialization should be sustained by regenerate power system. It is not a dead end but a new start.

Stirling Engine 31

ReferencesReferencesReferencesReferences

In order to accomplish the current project, the following web pages have been consulted. The authors of the project would like to thank the following for their accuracy, clarity and conciseness.

• http://en.wikipedia.org/wiki/Stirling_engine • http://www.kockums.se • http://www.grc.nasa.gov/WWW/tmsb/index.html • http://www.infiniacorp.com/main.htm • http://www.stirlingenergy.com • http://www.whispergen.com/index.cfm • http://www.sunpower.com/index.php • http://www.sesusa.org/index.html • http://news.soliclima.com • http://www.nrel.gov/csp • http://www.bekkoame.ne.jp/%7Ekhirata/english/others.htm • http://www.cec.uchile.cl/~roroman/ • http://www.stirlingengine.com/bboard/q-and-a-fetch-

msg.tcl?msg_id=00000D&topic_id=Power%2dproducing%20Stirling%20engines&topic=4

• www.blog.steamshift.com • www.techfreep.com • www.sensi.org • www.energytech.at • www.Sterlingenergy.com • www.Stirlingengine.com • www.logicsys.com.tw/wrkbas.htm. • www.bbc.co.uk/dna/h2g2/A9042707 • www.ent.ohiou.edu/~me321/chapter4th.info/Chapter3.html • www.ent.ohiou.edu/~urieli/stirling/me422.html • www.stirlingengine.com/faq/one?scope=public&faq_id=1#4

32 Stirling Engine

References of figures: Last visit of these websites: 10/11/2007

Figure1 www.sunpower.com

Figure2 www.creusot.net/archives/idee/stirling/img/stirling.gif

Figure3 tw.f14.yahoofs.com/myper/38.gq_GFHRT.YwEw_4YGB5QSPA--

/blog/ap_20060827013919701.jpg?TT_8kNHB1B7ghYo0

Figure4 http://mac6.ma.psu.edu/stirling/ideal_stirling_cycle/index.html

Figure5 http://www.ent.ohiou.edu/~urieli/stirling/engines/engines.htm

Figure6 http://www.moteurstirling.com/alpha.htm

Figure7 http://www.ent.ohiou.edu/~urieli/stirling/engines/beta.html

Figure8 http://en.wikipedia.org/wiki/Stirling_engine

Figure9 http://www.moteurstirling.com/beta.htm

Figure10 http://www.ent.ohiou.edu/~urieli/stirling/engines/gamma.html

Figure11 http://www.moteurstirling.com/gamma.htm

Figure12

http://www.diracdelta.co.uk/science/source/s/t/stirling%20engine/source.html

Figure13 http://blog.steamshift.com/2005/05/

Figure14 http://techfreep.com/category/energy/

Figure15 http://www.kockums.se/News/photostock/photo.html

Figure16 http://www.sensi.org/~svo/stirling/

Figure17 http://energytech.at/(en)/kwk/portrait_kapitel-2_6.html

Figure18 jiucifang.blog.bokee.net/bloggermodule/blog_viewblog.do?id=961285

Figure19 www.autobloggreen.com/tag/ford/

Figure20 www.kockums.se/Submarines/aipconversion.html

Figure21 www.kockums.se/Submarines/aipconversion.html

Stirling Engine 33

Figure22 www.cse.iitk.ac.in/.../371/abhishe/main1.html

Figure23 www.cse.iitk.ac.in/.../371/abhishe/main1.html

Figure24 www.whispergen.com/main/acwhispergen/

Figure25 www.grc.nasa.gov/.../5000/5490schreiber.html

Figure26 www.stirlingenergy.com/solar_overview.htm

Figure27 www.stirlingenergy.com/images.asp?Type=solar

Figure28 www.grc.nasa.gov/.../doc/adv_sd_tech.html

Documents

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