Abstract:
The invention discloses a heat-power conversion magnetism device. The heat-power conversion magnetism device includes a magneto caloric effect material so that the magnetic filed thereof can be changed according to the temperature difference. The heat-power conversion magnetism device rotates by changing the magnetic filed of magneto caloric effect material. The magnetic field is enhanced with rotating permanent magnet.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. provisional application entitled “HEAT-POWER CONVERSION DEVICE WITH PERMANENT MAGENT”, Ser. No. 61/243,379, filed Sep. 17, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention pertains to the field of a conversion device. More particularly, the invention pertains to a heat-power conversion magnetism device with permanent magnet enhancement. 
         [0004]    2. Description of the Related Art 
         [0005]    Converting thermal energy into power had a long period of time in human history. Especially the converting thermal energy into electrical power is the most common energy source today. However, the efficiency of conversion is still very low. For example, the efficiency is about 40% for steam power plant and about 30% for internal combustion engine. Almost 60-70% of energy is wasted. After power conversion, the remained energy becomes too low so that the temperature thereof is usually below 200° C. and mostly below 100° C. Such kind of low-grade energy cannot be utilized by most of the thermal engine available today. 
         [0006]    Taking the solar energy as an example, the sunshine provides huge amount of energy to earth but the energy density is one KW per square meter only. Flat panel of sunshine collector can convert solar energy into hot thermal energy very efficiently (&gt;90%) and cost effectively, but the thermal energy density is very low. Usually the temperature of flat panel solar hot water system is below 100° C. 
         [0007]    To convert low grade of energy (&lt;100° C.) into useful mechanical power by appropriate utilization of the magneto caloric effect (MCE) of solid ferromagnetic materials is desirable. 
         [0008]    Magneto caloric effect (MCE) has been discovered for over 100 years. Emil Gabriel Warburg discovered the magneto caloric effect in the iron in 1881. Soon after Warburg&#39;s discovery, Edison and Tesla tried to convert power from the magneto caloric effect of soft iron by heating and cooling, as disclosed in U.S. Pat. No. 396,121, No. 428,057, and No. 476,983. For a very long period of time, such technology was only applied in very low temperature refrigeration to cool down sample to few Kelvin to tens Kelvin since 1930′s. For near room temperature magnetic refrigeration was not able to achieve until 1976.Gadolinium (Gd) has been used as a magnetic working material and demonstrated the magnetic refrigeration at near room temperature in 1976. Gd, which has a Curie point of 293 Kelvin, is used as a working material by G. V. Brown of National Aeronautics and Space Administration. The temperature change of 14° K has been produced by applying 7 T magnetic field. Since then the study of the application of MCE materials has been increased, a lot of MCE materials property can be found in the disclosure of K. A. Gschneidner Jr, V. K. Pecharsky, “Recent developments in magnetocaloric materials”, Institute of Physics Rublishing, Reports on Progress in Physics, Rep. Prog. Phys. 68 (2005) 1479-1539. 
         [0009]    In 1997, V. K. Pecharsky and K. A. Gschneidner discovered that the entropy change (ΔS) of Gd 5 (Si X Ge 1−X ) 4  is much larger than Gd in near room temperature and the Curie temperature thereof can be changed from 29 Kelvin to 290 Kelvin by changing the composition of Si and Ge. Gd 5 (Si X Ge 1−X ) 4  can be a desirable magneto caloric effect material (MCEM). 
         [0010]    The basic principle of magneto caloric effect can be used as the magnetic refrigeration (or heat pump), which is disclosed in Peter W. Egolf, Andrej Kitanovski, “An introduction to magnetic refrigeration”, University of Applied Sciences of Western Switzerland; C. Zimm, A. Jastrab, “Description and Performance of a Near-Room Temperature Magnetic Refrigerator”, Advances in Cryogenic Engineer, Vol. 43;and G. V. Brown, “Magnetic heat pumping near room temperature”, Journal of Applied Physics, Vol. 47, No. 8, August 1976, also we can find the basic theory of magnetic cooling in the disclosure Andrej Kitanovski, Peter W. Egolf, “Thermodynamics of magnetic refrigeration”, International Journal of Refrigeration 29 (2006) 3-21. 
         [0011]    For an reversible adiabatic process and from Maxwell equation, the equations are disclosed as the following: 
         [0000]        ΔS   m =−∫μ 0 ( ∂M/∂T ) dH   (1)
 
         [0000]    wherein S m  is magnetic entropy; μ 0 is permeability of vacuum; M is magnetic moment; T is temperature; and H is magnetic field strength; 
         [0000]        ΔT   ad =−∫( T/C   p )( ∂M/∂T ) dH   (2)
 
         [0000]    wherein ΔT ad  is adiabatic temperature change and C p  is heat capacity; and 
         [0000]        ΔS   m   *T=C   p   *ΔT   ad   (3)
 
         [0012]    When a magnetic field is applied to the MCEM and the MCEM is magnetized, the magnetic entropy, S m , is changed according to the magnetic field changed by the magnetic order of the material. Under the adiabatic condition, the magnetic entropy change, ΔS m , must be compensated by an opposite change of the entropy associated with the lattice. The result is a change in temperature of the MCEM. In other words, when a magnetic field is applied to MCEM and loss its magnetic entropy, the temperature of the MCEM rise up to compensate the magnetic entropy loss. When the magnetic field is removed away from the MCEM and increase its magnetic entropy, the temperature of the MCEM cool down to compensate the magnetic entropy increase. 
         [0013]    By using MCEM together with proper thermal dynamic cycles, some heat engine for cooling, or heating, can be designed. 
         [0014]    There are four basic processes for MCE magnetic heat engine: (A) adiabatic magnetization: a magneto caloric effect material is subjected to magnetic field in adiabatic condition, and the temperature of the material rises up; (B) constant magnetic field cooling: a cold thermal heat source is provided to cool the material to low temperature; (C) adiabatic demagnetization: magnetic field is removed away from the material in an adiabatic condition, and temperature of the material goes down; and (D) zero magnetic field heat absorption: a hot thermal heat source is provided to heat the material. For cooling application, the process (D) is used to cool the environment. For heating application, the process (B) is used to warm the environment. 
         [0015]    From this equation, we can know that the magnetic entropy change of MCEM is relative to the (∂M/∂T). The larger (∂M/∂T) of the material is, the larger entropy change is, which will induce larger cooling capacity of magnetic thermal cycles. For the magnetic cooling (heat pump) application, the magnetic field is chosen to change the magnetic phase of MCEM, and the result is the change of magnetic entropy and eventually the change of temperature. The more largely the magnetic moment changes, the larger cooling capacity will be achieved. 
         [0016]    When dealing with heat-power conversion, the thermal energy is chosen to change the magnetic moment of MCEM, and the result is the power generation. For most of the MCEM, as the heat is applied to the MCEM and the temperature pass through the Curie temperature, the magnetic moment will change from high to low. Assume that a magnetism device with MCEM has been designed and allowed the magnetic flux flowing through the MCEM. When the thermal energy is applied to the MCEM and change its magnetic moment, the magnetic flux will be changed due to the magnetic moment change. 
         [0017]    The magneto caloric effect material (MCEM) is not only suitable for the magnetic refrigeration application, it also suitable for the reverse processing which is the heat-power conversion application. 
         [0018]    U.S. Pat. No. 396,121, No. 428,057, and No. 476,983 show the earlier ideas of heat-power conversion device. Although those prior arts give some great ideas of how to change the thermal energy into the mechanical work or electrical power but it never come to realization. It requires huge amount of energy to rise the temperature up to the Curie temperature and efficiency is low. Simply because of the near room temperature, a magneto caloric effect material (MCEM) had not been discovered until 1970&#39;s. U.S. Pat. No. 396,121 also requires spring or flywheel as mechanical energy storage device to complete the cycle. Also the armature moves forward and backward like a pendulum, which is not an efficient way for power generation. 
         [0019]    Both U.S. Pat. No. 428,057 and No. 476,983 require electric conductor coil for electrical power generation. When the temperature of the magnetic core is changed between its Curie temperature, the magnetic moment will be changed and cause the magnetic flux to change, thus the induced electrical current flows through the electric conductor coil. Another report in the disclosure of Paul F. Massier, C. P. Bankston, ECUT, Energy Conversion and Utilization Technologies Program “Direct Conversion Technology”, Annual Summary Report CY1988, Dec. 1, 1988 a  also introduces electric conductor coil for electrical power generation. The problem of electric conductor coil is that the power generation of the coil strongly depends on the magnetic flux changing frequency. The thermal transfer process for changing the magnetic moment of MCEM is slow , and the cycle time is 6 seconds (0.166 Hz) in the report of Reference of C. Zimm, A. Jastrab, “Description and Performance of a Near-Room Temperature Magnetic Refrigerator”, Advances in Cryogenic Engineer, Vol. 43. Another report of Dr. Zimm of Astronautics Corporation shows the operation frequency of 4 Hz. Being under such low operation frequency will limit the electrical power output of electric conductor coil and waste large amount of MCEM to convert enough power. 
         [0020]    U.S. Pat. No. 4,447,736 discloses the rotary magneto caloric ring system schematic. In this system, the MCEM forms a ring shape and rotates in the center of the ring. An extra magnet covers certain portion of ring, and hot heat exchanger and cold heat exchanger are applied to the rotation ring. A part of the rotating ring is being heated by hot heat exchanger, and a part of the rotation ring which is outside the magnetic field bounds is being cooled. The cooled portion of rotary magneto caloric ring, which the temperature is under its Curie temperature, will be attracted by the magnetic field. Such kind of rotary magneto caloric ring system schematic can provide a continuous smooth mechanical torque output. However it is difficult to utilize all the magnetic flux generated by the magnet, and only a part of the magneto caloric ring is attracted by the magnet, thus the mechanical torque output is relative low. Also how to prevent the leakage of the refrigerant between the heat exchanger and the rotary magneto caloric ring became a very difficult issue. 
         [0021]    Some interesting magnetic cooling or heating devices for generating a thermal flux with magneto caloric materials are disclosed in U.S. Publication No. 2007/0130960 and No. 2008/0236172. Permanent magnets are used to generate magnetic field and multiple number of magneto caloric effect materials (MCEM) are used so that the MCEMs are subjected to a variation in magnetic field. In order to generate strongest magnetic field as possible, a number of MCEMs are arranged as a multiple number of magnets. The location arrangement of magnetic poles of magnet and the MCEMs are well-aligned, and the magnetic flux can pass through the magnetic paths as smooth as possible. In other words, the magnetic resistance of magnetic paths is designed to be minimized. For the first example of U.S. Publication No. 2007/0130960, twelve thermal bodies made of MCEM and six magnetic elements are used. Such arrangement can allow the minimum magnetic resistance and maximum magnetic fluxing pass through the MCEMs when they are allied. Although such arrangement can create the maximum thermal effect of the MCEMs, but it also leads to extra problem. The static torque is also large and requires more driving power to move the magnetic field away from the MCEMs. 
         [0022]    Both U.S. Pat. No. 6,668,560 and No. 6,935,121 show a rotating magnet magnetic refrigerator. Both a number of magneto caloric material is a common multiple of the number of magnetic poles, and the attraction force at neutral position is large, thus the torque require to overcome the attraction force is large. 
         [0023]    An MCEM is the temperature dependency of magnetization. Cleber Santiago Alves, Sergio Gama, “Giant Magnetocaloric effect in Gd 5 (Si 2 Ge 2 ) Alloy with Low Purity Gd” and E. Bruck, O. Tegus, “Magnetic refrigeration—towards room-temperature application”, Physica B 327 (2003) 431-437 show the magnetization curves of Gd, Gd 5 Si 2 Ge 2 , and MnFe(P,As) at near room temperature. 
         [0024]      FIG. 1 . shows magnetization curves of Gadolinium (Gd);  FIG. 2 . shows magnetization curves of Gd 5 Si 2 Ge 2 ;  FIG. 3  shows magnetization curves of (Mn, Fe) 2 P 0.5 As 0.5 ; and  FIG. 4  shows MCE of MnFePAs in 2 T and 5 T magnetic field. 
         [0025]    The materials in  FIGS. 2 and 3  show the dramatically magnetic moment change when the temperature of the materials changes around its Curie temperature (Tc). Such kinds of materials are perfectly suitable for heat and mechanical power conversion.  FIG. 4 . shows the entropy change calculated using the equation (1). 
         [0026]    When a MCE material is subjected to magnetic field, large magnetic property (magnetic moment) changing occurs over relatively small temperature changes near the Curie temperature. Referring to  FIG. 4 , it is much clear to understand how the magnetic phase changes corresponding to the temperature. At 2 T magnetic field strength, the magnetic phase changes completely when the changing temperature (around 12 Kelvin) is between T low  and T high . 
         [0027]    If a heat source temperature is 10 Kelvin higher than Tc, it will be enough to change the magnetic moment from high to low. Taking the  FIG. 4  as an example, the Curie temperature of the material is 280 Kelvin, the hot heat source of 290 Kelvin and cold heat source of 275 Kelvin will be enough to change the magnetic moment between T high  and T low . 
         [0028]    Such kind of hot heat source can be found everywhere in our ordinary life. The disclosure of Andrej Kitanovski, Marc Diebold, “Applications of Magnetic “Power Production: and its assessment”, Final Report, Swiss Federal Office of Energy—BFE, 2007 shows some of the type of heat source, for example solar, geothermal, vehicle or industry processes, and the temperature range from 60° C. to 180° C. The invention intends to convert such low-grade of thermal energy into useful mechanical power efficiency. 
       BRIEF SUMMARY OF THE INVENTION 
       [0029]    A new kind of heat-power conversion technology is introduced in the invention. This invention intend to achieve the goal as below: 
         [0030]    1. Converting a very low temperature heat source (&lt;100° C.) into useful power; 
         [0031]    2. Without using electric conductor coil for power generation; 
         [0032]    3. Simplifying rotation magnetic mechanism design; and 
         [0033]    4. Having high thermal efficiency. 
         [0034]    Now, two important basic rules are understudied and will be used commonly in this invention as the following. 
         [0035]    (1) The temperature of a magneto caloric effect material over its Curie temperature will influence the magnetic properties and the magnetic moment of the material at low level. The magnetic property is more like a paramagnetism material. 
         [0036]    (2) The temperature of the magneto caloric effect material below its Curie temperature will influence the magnetic properties and the magnetic moment of the material at high level. The magnetic property is more like a ferromagnetism material. 
         [0037]    These two basic rules will be used frequently in this invention. 
         [0038]    An exemplary embodiment of a heat-power conversion magnetism device comprises a sleeve, a magnet, a plurality of magneto caloric effect material units, and a plurality of rotating magnets. The magnet is disposed at a center area of the sleeve and has at least one pair of magnetic poles. The plurality of magneto caloric effect material units are disposed between the sleeve and the magnet. The plurality of rotating magnets are disposed in the sleeve. 
         [0039]    Another exemplary embodiment of a heat-power conversion magnetism device comprises a sleeve, a plurality of rotating magnets, and a plurality of magneto caloric effect material units. The plurality of rotating magnets are disposed at an inner surface of the sleeve. The plurality of magneto caloric effect material units are disposed in the sleeve. The rotating magnets and the magneto caloric effect material units are alternately disposed. 
         [0040]    Another exemplary embodiment of a heat-power conversion magnetism device comprises a sleeve, a core, a plurality of rotating magnets, and a plurality of magneto caloric effect material units. The core is disposed at a center area of the sleeve. The plurality of rotating magnets are disposed on an outer face of the core. The plurality of magneto caloric effect material units are disposed between the sleeve and the magnet. 
         [0041]    Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0043]      FIG. 1  shows magnetization curves of Gadolinium (Gd); 
           [0044]      FIG. 2 . shows magnetization curves of Gd 5 Si 2 Ge 2 ; 
           [0045]      FIG. 3 . shows magnetization curves of (Mn, Fe) 2 P 0.5 As 0.5 ; 
           [0046]      FIG. 4 . shows MCE of MnFePAs in 2 T and 5 T magnetic field; 
           [0047]      FIG. 5A  shows cross-sectional view of a heat-power conversion magnetism device according to an embodiment of the present invention; 
           [0048]      FIG. 5B  shows another sectional view of the heat-power conversion magnetism device; 
           [0049]      FIGS. 6A-6E  show rotating steps illustrated by cross-sectional views of the rotating magnet heat-power conversion magnetism device of  FIG. 5A ; 
           [0050]      FIGS. 7A-7F  show embodiments with different arrangements of magneto caloric effect material units of a heat-power conversion magnetism device of the present invention; 
           [0051]      FIG. 8  shows a heat-power conversion magnetism device according to an embodiment of the present invention; 
           [0052]      FIGS. 9A-9D  show rotating steps illustrated by cross-sectional views of a rotating magnet heat-power conversion magnetism device according to another embodiment of the invention; 
           [0053]      FIGS. 10A-10D  show rotating steps illustrated by cross-sectional views of a rotating magnet heat-power conversion magnetism device according to another embodiment of the invention; and 
           [0054]      FIGS. 11A-11C  show variations of embodiments of a heat-power conversion magnetism device of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0055]    The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
         [0056]      FIG. 5A  shows cross-sectional view of a heat-power conversion magnetism device  100  according to an embodiment of the invention. As shown in the drawing, the heat-power conversion magnetism device  100  includes a sleeve  25  and a core  26  which is disposed at the center area of the sleeve  25 . Six MCEM units  6 - 11  are disposed at the inner face of the sleeve  25 , and four magnets  2 - 5  are disposed at the outer face of the core  26 . Six rotating magnets  12 - 17  are embedded at the sleeve  25 . The rotating magnets  12 - 17  rotates in a clockwise (CW) direction, and the core  26  rotates along the canter axis  1  in a counterclockwise (CCW) direction, as indicated by arrows  18  and  19  respectively. 
         [0057]      FIG. 5B  shows the synchromesh structure of rotating magnets and center axis. A center gear  20  is connected with the center axis  1 , and six rotating magnet gears  21  are connected with the rotating magnets  12 ,  13 ,  14 ,  15 ,  16 , and  17 . The center gear  20  is larger than the rotating magnet gears  21  so that the rotation speed of the rotating magnets are faster than the center axis  1  in opposite direction. A number of magnetic poles and MCEM units will influence the gear ratio and the relative rotation direction. The synchronize belt can be provided for those case who&#39;s rotation directions are the same. 
         [0058]      FIGS. 6A-6E  show rotating steps illustrated by cross-sectional views of the heat-power conversion magnetism device  100 . 
         [0059]    As shown in  FIG. 6A , the MCEM units  6  and  9 , as marked shadow, are heated to reach a temperature higher than Curie temperature thereof, and the temperature of the MCEM units  7 ,  8 ,  10 , and  11  is lower than Curie temperature thereof. Multi magnetic flux paths  30 ,  31 ,  32 , and  33  are generated. At this moment, the core  26  is at lowest magnetic resistance and in the neutral position. The rotating magnets  12 ,  13 ,  14 ,  15 ,  16 , and  17  are arranged to enhance the magnetic flux density of the magnetic flux paths. 
         [0060]    In  FIG. 6B , the MCEM units  7  and  10  are heated to reach a temperature higher than Curie temperature thereof, and the temperature of the MCEM units  6 ,  8 ,  9 , and  11  is lower than its Curie temperature. The pattern of major magnetic flux paths  34  and  35  are much different from the magnetic flux paths  30 ,  31 ,  32 , and  33  in  FIG. 6A . The core  26  will try to rotate in a counterclockwise direction to the new location with lower magnetic resistance. 
         [0061]    Eventually, the core  26  reaches the neutral position as shown in  FIG. 6C , which the major magnetic flux paths  36 ,  37 ,  38 , and  39  are similar to the magnetic flux paths  30 ,  31 ,  32 , and  33  in  FIG. 6A . 
         [0062]    Note the magnetic pole and the flux near the MCEM unit  9  and the rotating magnets A and B in  FIG. 6A . The magnetic flux  33  is shown to flow in a clockwise direction, and the magnetic poles of the rotating magnet A and B will enhance the flowing of the magnetic flux  33 . 
         [0063]    The four major magnetic flux paths  30 ,  31 ,  32 , and  33  are at it lowest magnetic resistance, and the rotor is in the neutral position. The rotating magnets are arranged to enhance the magnetic flux density of each major magnetic flux path. 
         [0064]    The MCEM units  6  and  9  are heated in  FIG. 6A , and the four magnetic flux  30 ,  31 ,  32  ,and  33  are generated. The magnetic resistance of this device is in the low state. 
         [0065]    Now look at the magnetic pole and the flux near the MCEM unit  10  and rotating magnets C and D in  FIG. 6C . The magnetic flux  39  flows in the counterclockwise direction, and the magnetic poles of the rotating magnets C and D will enhance the flowing of the magnetic flux  39 . 
         [0066]    The rotation angle of the core  26  from  FIG. 6B  to  FIG. 6C  is 30 degree in the counterclockwise direction, and the rotation angle of each of the rotating magnets is 60 degree in the clockwise direction. The new location of the rotating magnets still enhances the magnetic flux density of each of the major magnetic flux paths. 
         [0067]    The device  100  now is ready for next temperature changing step which is shown in  FIG. 6D  and  FIG. 6E . 
         [0068]    In  FIG. 6D  and  FIG. 6E , the temperature of the MCEM units  8  and  11  are now higher than its Curie temperature, and the temperature of the MCEM units  6 ,  7 ,  9 , and  10  are lower than it&#39;s Curie temperature. 
         [0069]    The rotation angle of the rotor from  FIG. 11D  to  FIG. 11E  is 30 degree in the counterclockwise direction and the rotation angle of each rotating magnets is 60 degree in the clockwise direction. The new location of the rotating magnets still enhances the magnetic flux density of each of the major magnetic flux paths. 
         [0070]    From  FIG. 6A  to  FIG. 6E , it is clear to understand that the rotating magnets are arranged to always enhance the magnetic flux density so that the torque is continuously enhanced. The rotating magnets  12 - 17  will enhance the variation of the magnetic flux density of each of the magnetic flux paths, which will enhance the magnetic resistance. 
         [0071]    It is easy to understand that different kinds of magnetism designs will lead to different location arrangements of TMFGs. There are various possibilities with regard to alternative embodiments of a heat power conversion apparatus according to the invention. The same principle of  FIGS. 6A-6E  is easy to apply to those devices in  FIGS. 7A-7F . 
         [0072]      FIGS. 7A-7F  show different arrangements of MCEM units of heat-power conversion magnetism devices  100 A- 100 F. In  FIGS. 7A-7F , MCEM units are labeled by “ 91 ”, magnets are labeled by “ 92 ”, a sleeve is labeled by “ 93 ”, and rotating magnets are labeled by  94 ′. 
         [0073]      FIG. 8  shows a rotating magnet heat-power conversion magnetism device  101  including a superconductor coil magnet. The device  101  includes a sleeve  3  and a superconductor coil magnet which is disposed at the center area of the sleeve  3 . Four magnetic poles  21 ,  22 ,  23 , and  24  are formed with the superconductor coil magnet. Six MCEM units  4 ,  5 ,  6 ,  7 ,  8 , and  9  are disposed on the inner face of the sleeve  3 . A thermal insulation shield  30  is disposed on the outer face of the superconductor coil magnet. 
         [0074]    There are two benefits of using the superconductor coil magnet: (1) much higher magnetic field density (larger than 5 Telsa) to be generated; and (2) magnetic field density which is controllable by changing the electrical current. 
         [0075]      FIGS. 9A-9D  show a rotating magnet heat-power conversion magnetism device  102  according to the other embodiment of the invention. The device  102  includes a sleeve  6 , a core  7  disposed at the center area of the sleeve  6 , two magnetic poles  4  and  5  disposed on the outer face of the core  7 , three MCEM units  1 ,  2  and  3  disposed in the sleeve  6 , and three rotating magnets  10 ,  11 , and  12  disposed in the sleeve  6 . The MCEM units  1 ,  2 , and  3  and the rotating magnets  10 ,  11 , and  12  are alternately disposed. 
         [0076]    In  FIG. 9A , the MCEM unit  1  is heated (marked by shadow), and the MCEM units  2  and  3  are cooled. 
         [0077]    In  FIG. 9B , the MCEM unit  2  just has been heated, and the MECM units  1  and  3  just have been cooled. 
         [0078]    In  FIG. 9C , the core  7  rotates 30 degree (half step), and the rotating magnets  10 ,  11 , and  12  rotate 90 degree. 
         [0079]    In  FIG. 9D , the core  7  rotates 60 degree (full step), and the rotating magnets  10 ,  11 , and  12  rotate 180 degree. 
         [0080]    From  FIG. 9A  to  FIG. 9D , a full step angle is completed. 
         [0081]      FIGS. 10A-10D  show a rotating magnet heat-power conversion magnetism device  103  according to another embodiment of the invention. The device  103  includes a sleeve  6 , a core  7  disposed at the center area of the sleeve  6 , two magnetic poles  4  and  5  disposed on the outer face of the core  7 , three MCEM units  1 ,  2 , and  3  disposed on the inner face of the sleeve  6 , and three rotating magnets  10 ,  11 , and  12  embedded in the sleeve  6 . 
         [0082]    In  FIG. 10A , the MCEM unit  1  is heated (marked by shadow), and the MCEM units  2  and  3  are cooled. 
         [0083]    In  FIG. 10B , the MCEM unit  2  just has been heated, and the MCEM units  1  and  3  just have been cooled. 
         [0084]    In  FIG. 10C , the core  7  rotates 30 degree (half step), and the rotating magnets  10 ,  11 , and  12  rotate 90 degree. 
         [0085]    In  FIG. 10D , the core  7  rotates 60 degree (full step), and the rotating magnets  10 ,  11 , and  12  rotate 180 degree. 
         [0086]    From  FIG. 10A  to  FIG. 10D , a full step angle is completed. 
         [0087]      FIG. 11A  shows a rotating magnet heat-power conversion magnetism device  104 A according to another embodiment of the invention. The device  104 A includes a Halbach magnet ring  2  which is a kind of permanent magnet array with eight segments with special magnetization vector as indicated by arrows shown in  FIG. 11A . Two equivalent magnetic poles are generated in the center space of the ring  2 . Three MCEM units  4 ,  5 , and  6 , a high permeability magnetic material  3 , and three rotating magnets are arranged in the center space of the Halbach magnet ring  2 . The magnetic flux density of the center space of the Halbach magnet ring  2  can be designed as high as 2˜3 Tesla. The magnetic flux density is presented as the following equation: 
         [0000]        B=Br* ( In ( Ro/Ri ))  (4)
 
         [0088]    wherein B is the magnetic flux density; Br is the remanence of the material of the Halbach magnet ring; Ro is the radius of the outer dimension of the Halbach magnet ring; and Ri is the radius of the inner dimension of the Halbach magnet ring. 
         [0089]      FIG. 11B  shows another example of permanent magnet array as magnetic field source. A device  104 B is disclosed. Eight magnets, six MCEM units  4 , 5 , 6 , 7 , 8 , and  9 , and six rotating magnets are presented. TMFGs and rotating magnets are located inside the Halbach magnet ring  2 . 
         [0090]      FIG. 11C  shows an application of a permanent magnet array with external magnetic field. 
         [0091]    It should be noted that the temperature difference of the system for converting energy should be larger than the temperature for changing the magnetic phase of the MCEM. Generally, the temperature difference of day and night is sometimes larger than 40 Kelvin. Again referring to  FIG. 4 , the temperature difference of the MCEM, such as MnFeP 0.5 As 0.5 , for changing the magnetic phase thereof is about 12-15 Kevin only. If a hot source is arranged to absorb the heat from the environment in the day time and a cold source is arranged to expel the heat to the cooler environment in the night time, the temperature difference between the hot and cold sources will be as large as 40 Kevin and enough to change the magnetic field of the MCEM, i.e. MnFeP 0.5 As 0.5 . The heat-power conversion magnetism device to be driven by the temperature difference in the environment is workable. 
         [0092]    To sum up, while the invention has been described by way of example and in terms of preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.