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					                                11/11/2007




UNIVERSITY
OF GÄVLE     STIRLING ENGINE




                     MAIER Christoph
                     GIL Arnaud
                     AGUILERA Rafael
                     SHUANG Li
                     YU Xue
                                                             Index


    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




2                                                                     Stirling Engine
                                Summary

       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.




                          Stirling Engine                                            3
                                 Introduction
    "…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])




                                Figure 1 : Sketch of Robert Stirling of his invent



            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.




4                                                   Stirling Engine
                                  History

        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




                         Stirling Engine                                               5
    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.




6                                                  Stirling Engine
           Presentation of Stirling
                                   Engines

 I.             thermodynamic cycle
       Stirling thermodyna

        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
is that of thermal expansion and contraction of this fluid due to a temperature
differential.
                                                     thermodynamics
        So the ideal Stirling cycle consists of four thermodynamic distinct processes
                                              temperature                    constant-
acting on the working fluid: two constant-temperature processes and two constant
volume processes.

         ch
       Each one of which can be separately analysed:

                                       process.
       1-2: 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 temperature
       TC.
             onstant                                            addition.
       2-3: constant volume displacement process with heat addition Heat Q2-3 is
       absorbed by the working fluid and temperature is raised from TC to TH. No
       work is done.
                                   process.
       3-4: isothermal expansion process Work W3-4 is done by the working fluidfluid,
       while 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 TH.
                                                               rejection.
       4-1: constant volume displacement process with heat rejection Heat Q4-1 is
       rejected by the working fluid and temperature decrease from TC to TH. No
       work is done.




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


                         Stirling Engine                                             7
           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.




8                                            Stirling Engine
   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”.




                                 Figure 5 : Alpha engine’s configuration


       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.




 Expansion: At this point, the most of                 Transfer: At this point, the gas has
 the gas in the system is at the hot piston            expanded. Most of the gas is still in the
 cylinder. The gas heats and expands,                  hot cylinder. As the crankshaft continues
                                                       to turn the next 90°, transferring the bulk
 pushing the hot piston down, and
                                                       of the gas to the cold piston cylinder. As
 flowing through the pipe into the cold                it does so, it pushes most of the fluid
 cylinder, pushing it down as well.                    through the heat exchanger and into the
                                                       cold piston cylinder.




                         Stirling Engine                                                    9
     Contraction: Now the majority of the                                                        now
                                                               Transfer: The fluid is cooled and n the
     expanded gas is shifted to the cool piston                      shaft
                                                               crankshaft turns another 90°. The gas is
     cylinder. It cools and contracts, drawing                 therefore pumped back, through the heat
     both pistons up                                           exchanger, into the hot piston cylinder.
                                                               Once in this, it is heated and we go back
                                                               to the first step.




                                                          This diagram is feature of an alpha engine.
                                                          The most important is to have the biggest
                                                          grey area which represents the
                                                          recuperated work during a cycle.




Figure 6 : Example of a real cycle of an alpha engine




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




 10                                                     Stirling Engine
                                            power-to-volume
       This type of engine has a very high power volume ratio but has technical
problems 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.

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




                                Figure 7 : Beta engine’s configuration



                       the
      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.

                                           piston
        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 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
                                                                         Figure 8 : Beta engine
cylinder it contracts and the momentum of the machine, usually
                                                                           with momentum
enhanced by a flywheel, pushes the power piston the other way to
                                                                               flywheel
compress the gas. Unlike the alpha type, the beta type avoids the
technical problems of hot moving seals.




                        Stirling Engine                                                       11
 Expansion: At this point, most of the gas in          Transfer: At this point, the gas has
 the system is at the heated end of                    expanded. Most of the gas is still located in
 the cylinder. The gas heats and expands               the hot end of the cylinder. Flywheel
 driving the power piston outward.                     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                   Transfer: The contracted gas is still located
expanded gas has been shifted to the cool              near the cool end of the cylinder. Flywheel
end. It contracts and the displacer is almost          momentum carries the crank another quarter
at the bottom of its cycle.                            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.




   12                                           Stirling Engine
                                     Figure 9 : Example of a real cycle of a beta
                                                       engine




   3. Gamma Stirling


      A gamma Stirling is simply a beta Stirling in which the power piston is
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
                                                                  lower
them and remains a single body. This configuration produces a lowe compression
                                                     multi-cylinder
ratio but is mechanically simpler and often used in multi cylinder Stirling engines.
Gamma type engines have a displacer and power piston, similar to Beta machines, but
                                                                     between the heat
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.




                              Figure 10 : Gamma engine’s configuration



       Furthermore during the expansion process some of the expansion must take
place in the compression space leading to a reduction of specific power. Gamma
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
                    cylinders
convenience of two cylinders in which only the piston has to be sealed. The




                        Stirling Engine                                             13
 disadvantage is the lower compression ratio but the gamma configuration is the
 favorite for modelers and hobbyists.



                                           .




                                                                  Figure 11 : Small gamma engine



     Figure 12 : Example of a real cycle of a
                  beta engine




     4. Other types

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

        There is also a 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
                                          non-return
 contains a working gas, a liquid and two non return valves. The work produced by the
  luidyne
 fluidyne goes into pumping the liquid.




14                                              Stirling Engine
     Reasons to use a Stirling
                               Engine

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




                     Stirling Engine                                            15
     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




16                                       Stirling Engine
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.




                        Figure 16 : Low power Stirling engine



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 17 : CHP




                 Stirling Engine                                               17
     Analyze from Economic point


                         he
         As said above the Stirling engine is a kind of external combustion engine, and
                                   can
 it can use a variety of fuels. It can be estimated that combustible gases are the best
 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
                   iver.
 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 external
 heating sealed chamber, the expansion of gases inside the engine promotes the pistons
                he                                          air-conditioned
 work. After the expanded gases cooling down in the air conditioned room, next
 process is taking on. As long as a certain value of the temperature difference exists, a
 Stirling Engine can be formed.




                        Figure 18 : Stirling Engine working on a cup of coffee


         This experiment shows that only a very small power operation can carry out a
 Stirling engine, which contributes a lot to energy conservation. This characteristic
 especially shows out on economy point. The benefits obtained from the Stirling
      ne
 engine are definitely far beyond the costs.

         So once solar is used to produce energy for the Stirling engine, the cost would
 surely be cut down for quite a lot. As long as there is sunshine, the Stirling engine will
                                            manufacture
 run on and on. Of course it costs much to manufacture a Stirling engine, as it requires




18                                              Stirling Engine
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.




                          Stirling Engine                                               19
          Applications of the Stirling
                                     power

     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




20                                          Stirling Engine
   II.      Submarine
        “Kockums”, a Swedish defense contractor, produce Stirling Engines for the
  navy making the quietest submarines in the world.




                                               Figure 20 : AIP system


           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 21 : Stirling engine in Näcken




                                   Stirling Engine                                                21
 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.




                                   Figure 22 : Torque-Crankshaft Angle



        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.
             Figure 23 : Altitude-Airspeed
                                                           Another hamper is eliminated




22                                               Stirling Engine
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...”

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




                               Stirling Engine                                            23
          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




24                                          Stirling Engine
 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
  Figure 25 : Conceptual design of the SRG by Lockheed
                                                 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.




                               Stirling Engine                                                 25
                           Figure 26 : Solar Dynamic Brayton Schematic



         Some companies are launching technology using steel, cooper, aluminium and
 glass in the same low cost manufacturing techniques used to make consumer products.
                                          over                   sun
 The equipment is well characterized with ove 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
 solar technologies.

         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
 those found in internal combustion engines but without
 igniting the gas. The drive shaft is connected to a small
 electricity generator.                                                  Figure 27 : Solar Dynamic Brayton
                                                                                    Schematic


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

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




26                                            Stirling Engine
                                           Estimated   Estimated
                                           Annual      Annual      Initial
                               Possible
                     Initial               Energy      Energy      Phase     Completion      Term of     Estimated
         Gen.                  Expansion
Seller               Size                  Based on    Based on    On-       Date      for   Agreement   Capacity
         Type                  Size
                     (MW)                  Initial     Expansion   Line      Initial Size    (Years)     Factor
                               (MW)
                                           Size        Size        Date
                                           (GWH)       (GWH)
SES      Solar
Solar    Thermal                                                   Jan.                                  23.90
                     500       850         1,047       1,780                 Dec. 2012       20
One      (Stirling                                                 2009                                  percent
LLC      Dish)
          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




                                     Stirling Engine                                                               27
 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




28                                           Stirling Engine
                            Conclusion


       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.




                         Stirling Engine                                                29
        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.




30                                        Stirling Engine
                          References

       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%20engi
       nes&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




                        Stirling Engine                                            31
 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




32                                          Stirling Engine
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




                     Stirling Engine                       33

				
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