Abstract:
A process for controlling a system for generating electricity which contains at least two compressors and two microturbines. Compressed gas from a pressure vessel is supplied to the first microturbine, and thereafter the pressure within the pressure vessel is measured. If the pressure is below a specified value, a first compressor is caused to operate to feed compressed gas to the pressure vessel. Thereafter, as the system needs require, a second compressor and, optionally, a third compressor is caused to furnish compressed gas to the pressure vessel. If the system pressure within the pressure vessel is too high, the third compressor is shut down and, if necessary, the second compressor and the first compressor are then sequentially shut down.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a continuation-in-part of applicants&#39; copending patent application U.S. Ser. No. 09/416,291, filed on Oct. 14, 1999, which was a continuation-in-part of patent application U.S. Ser. No. 09/396,034, filed on Sep. 15, 1999, which in turn was a continuation-in-part of patent application U.S. Ser. No. 09/181,307, filed on Oct. 28, 1998, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     A process for controlling a system for generating electricity in which a multiplicity of compressors which are connected to a microturbine are selectively turned on and off in response to the level of gas pressure. 
     BACKGROUND OF THE INVENTION 
     Microturbines, also known as turbogenerators and turboalternators, are gaining increasing popularity and acceptance. These microturbines are often used in conjunction with one or more compressors which supply gaseous fuel to them at a desired pressure, generally from about 40 to about 500 pounds per square inch. 
     The microturbines are often employed in a system comprising two or more microturbines. These systems could be supplied by only one compressor, but such operation often results in too much compressor capacity when less than all of the microturbines are operating. 
     It is an object of this invention to provide a process for controlling the output of a multiplicity of compressors connected to one or more microturbines. 
     SUMMARY OF THE INVENTION 
     A process for controlling a system for generating electricity, which system is comprised of a first compressor, a second compressor, a first microturbine, and a second microturbine, comprising the steps of supplying a first compressed gas at a pressure of from about 40 to about 500 pounds per square inch from a first gas source to said first microturbine, making a first measurement of the pressure of gas within said first gas source, supplying gas from a second gas source to a first compressor, compressing said gas from said second gas source in said first compressor to a pressure of from about 40 to about 500 pounds per square inch, thereby producing a second compressed gas, supplying said second compressed gas to said first gas source, supplying said second compressed gas from said first gas source to said first microturbine, making a second measurement of the pressure of gas within said first gas source, supplying gas from a second gas source to a second compressor, compressing said gas from said second gas source in said second compressor to a pressure of from about 40 to about 500 pounds per square inch, thereby producing a third compressed gas, supplying said third compressed gas to said first gas source, and supplying said third compressed gas from said first gas source to said second microturbine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The claimed invention will be described by reference to the specification and the following drawings, in which: 
     FIG. 1 is a perspective view of one preferred rotary mechanism claimed in U.S. Pat. No. 5,431,551; 
     FIG. 2 is an axial, cross-sectional view of the mechanism of FIG. 1; 
     FIG. 3 is a perspective view of the eccentric crank of the mechanism of FIG. 1; 
     FIG. 4A is a transverse, cross-sectional view of the eccentric crank of FIG. 3; 
     FIG. 5 is a perspective view of the rotor of the device of FIG. 1; 
     FIG. 6 is an axial, cross-sectional view of the rotor of FIG. 5; 
     FIG. 7 is a transverse, cross-sectional view of the rotor of FIG. 5; 
     FIG. 8 is an exploded, perspective view of the device of FIG. 1; 
     FIG. 9 is a sectional view of one hollow roller which can be used in the rotary positive displacement device of this invention; 
     FIG. 10 is a sectional view of another hollow roller which can be used in the rotary positive displacement device of this invention; 
     FIG. 11 is a schematic view of a modified rotor which can be used in the positive displacement device of this invention; 
     FIG. 12 is a block diagram of a preferred electrical generation system; 
     FIG. 13 is a block diagram of the gas booster system of FIG. 12; 
     FIG. 14 is a schematic representation of an apparatus comprised of a guided rotor device and a reciprocating compressor; 
     FIG. 15 is a schematic representation of another apparatus comprised of a guided rotor device and a reciprocating compressor; 
     FIG. 16 is a schematic representation of another guided rotor apparatus; and 
     FIG. 17 is a schematic representation of yet another guided rotor apparatus; 
     FIG. 18 is a sectional view of a multi-stage guided rotor assembly; 
     FIG. 19 is a sectional view of a guided rotor assembly with its drive motor enclosed within a hermetic system; 
     FIG. 20 is a schematic illustration of a microturbine electric generation and waste heat recovery system; 
     FIG. 21 is a schematic diagram of one preferred process of the invention, illustrating one preferred means for measuring gas pressure within the electrical generating system; 
     FIG. 22 is a schematic diagram of the process depicted in FIG. 21, illustrating a preferred a preferred pressure relief system; 
     FIG. 23 is graph illustrating the a typical history of gas pressure versus time for the system of FIG.  21 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the first part of this specification, applicants will describe a system for generating electricity. In the second part of this specification, applicants will describe a system for controlling the amount of gas delivered in an electrical generating system comprised of two or more microturbines. 
     FIGS. 1,  2 ,  3 ,  4 ,  4 A,  5 ,  6 ,  7 , and  8  are identical to the FIGS. 1,  2 ,  3 ,  4 ,  4 A,  5 ,  6 ,  7 , and  8  appearing in U.S. Pat. No. 5,431,551; and they are presented in this case to illustrate the similarities and differences between the rotary positive displacement device of such patent and the rotary positive displacement device of the instant application. The entire disclosure, the drawings, the claims, and the abstract of U.S. Pat. No. 5,431,551 are hereby incorporated by reference into this specification. 
     Referring to FIGS. 1 through 8, and to the embodiment depicted therein, it will be noted that rollers  18 ,  20 ,  22 , and  24  (see FIGS. 1 and 8) are solid. In the rotary positive displacement device of the instant invention, however, the rollers used are hollow. 
     FIG. 9 is a sectional view of a hollow roller  100  which may be used to replace the rollers  18 ,  20 ,  22 , and  24  of the device of FIGS. 1 through 8. In the preferred embodiment depicted, it will be seen that roller  100  is a hollow cylindricral tube  102  with ends  104  and  106 . 
     Tube  102  may consist of metallic and/or non-metallic material, such as aluminum, bronze, polyethyletherketone, reinforced plastic, and the like. The hollow portion  108  of tube  102  has a diameter  110  which is at least about 50 percent of the outer diameter  112  of tube  102 . 
     The presence of ends  106  and  108  prevents the passage of gas from a low pressure region (not shown) to a high pressure region (not shown). These ends may be attached to tube  102  by conventional means, such as adhesive means, friction means, fasteners, threading, etc. 
     In the preferred embodiment depicted, the ends  106  and  108  are aligned with the ends  114  and  116  of tube  102 . In another embodiment, either or both of such ends  106  and  108  are not so aligned. 
     In one embodiment, the ends  106  and  108  consist essentially of the same material from which tube  102  is made. In another embodiment, different materials are present in either or both of ends  106  and  108 , and tube  102 . 
     In one embodiment, one of ends  106  and/or  108  is more resistant to wear than another one of such ends, and/or is more elastic. 
     FIG. 10 is sectional view of another preferred hollow roller  130 , which is comprised of a hollow cylindrical tube  132 , end  134 , end  136 , resilient means  138 , and O-rings  140  and  142 . In this embodiment, a spring  138  is disposed between and contiguous with ends  134  and  136 , urging such ends in the directions of arrows  1444  and  146 , respectively. It will be appreciated that these spring-loaded ends tend to minimize the clearance between roller  130  and the housing in which it is disposed; and the O-rings  140  and  142  tend to prevent gas and/or liquid from entering the hollow center section  150 . 
     In the preferred embodiment depicted, the ends  144  and  146  are aligned with the ends  152  and  154  of tube  132 . In another embodiment, not shown, one or both of ends  144  and/or  146  are not so aligned. 
     The resilient means  138  may be, e.g., a coil spring, a flat spring, and/or any other suitable resilient biasing means. 
     FIG. 11 is a schematic view of a rotor  200  which may be used in place of the rotor  16  depicted in FIGS. 1,  5 ,  6 ,  7 , and  8 . Referring to FIG. 11, partial bores  202 ,  204 ,  206 , and  208  are similar in function, to at least some extent, the partial bores  61 ,  63 ,  65 , and  67  depicted in FIGS. 5,  6 ,  7 , and  8 . Although, in FIG. 11, a different partial bore has been depicted for elements  202 ,  204 ,  206 , and  208 , it will be appreciated that this has been done primarily for the sake of simplicity of representation and that, in most instances, each of partial bores  61 ,  63 ,  65 , and  67  will be substantially identical to each other. 
     It will also be appreciated that the partial bores  202 ,  204 ,  206 , and  208  are adapted to be substantially compliant to the forces and loads exerted upon the rollers (not shown) disposed within said partial bores and, additionally, to exert an outwardly extending force upon each of said rollers (not shown) to reduce the clearances between them and the housing (not shown). 
     Referring to FIG. 11, partial bore  202  is comprised of a ribbon spring  210  removably attached to rotor  16  at points  212  and  214 . Because of such attachment, ribbon spring  210  neither rotates nor slips during use. The ribbon spring  210  may be metallic or non-metallic. 
     In one embodiment, depicted in FIG. 11, the ribbon spring  210  extends over an arc greater than 90 degrees, thereby allowing it to accept loads at points which are far from centerline  216 . 
     Partial bore  204  is comprised of a bent spring  220  which is affixed at ends  222  and  224  and provides substantially the same function as ribbon spring  210 . However, because bent spring extends over an arc less than 90 degrees, it accepts loads primarily at our around centerline  226 . 
     Partial bore  206  is comprised of a cavity  230  in which is disposed bent spring  232  and insert  234  which contains partial bore  206 . It will be apparent that the roller disposed within bore  206  (and also within bores  202  and  204 ) are trapped by the shape of the bore and, thus, in spite of any outwardly extending resilient forces, cannot be forced out of the partial bore. In another embodiment, not shown, the partial bores  202 ,  204 ,  206 , and  208  do not extend beyond the point that rollers are entrapped, and thus the rollers are free to partially or completely extend beyond the partial bores. 
     Referring again to FIG. 11, it will be seen that partial bore  208  is comprised of a ribbon spring  250  which is similar to ribbon spring  210  but has a slightly different shape in that it is disposed within a cavity  252  behind a removable cradle  254 . As will be apparent, the spring  250  urges the cradle  254  outwardly along axis  226 . Inasmuch as the spring  250  extends more than about 90 degrees, it also allows force vectors near ends  256  and  258 , which, in the embodiment depicted, are also attachment points for the spring  250 . 
     Figure is  12  is a block diagram of one preferred apparatus of the invention. Referring to FIG. 12, it will be seen that gas (not shown) is preferably passed via gas line  310  to gas booster  312  in which it is compressed to pressure required by micro turbine generator  314 . In general, the gas must be compressed to a pressure in excess of 30 p.s.i.g., although pressures as low as about 20 p.s.i.g. and as high as 360 p.s.i.g. or more also may be used. 
     In FIGS. 12 and 13, a micro turbine generator  314  is shown as the preferred receiver of the gas via line  313 . In other embodiments, not shown, a larger gas turbine and/or a fuel cell may be substituted for the micro turbine generator  314 . 
     In one embodiment, in addition to increasing the pressure of the natural gas, the gas booster  312  also generally increases its temperature to a temperature within the range of from about 100 to about 150 degrees Fahrenheit. In one embodiment, the gas booster  312  increases the temperature of the natural gas from pipeline temperature to a temperature of from about 100 to about 120 degrees Fahrenheit. 
     The compressed gas from gas booster  312  is then fed via line  313  to micro turbine generator  314 . The components used in gas booster  312  and in micro turbine generator  314  will now be described. 
     FIG. 13 is a schematic diagram of the gas booster system  312  of FIG.  12 . Referring to FIG. 12, it will be seen that gas booster system  312  preferably is comprised of a guided rotor compressor  316 . 
     The guided rotor compressor  316  depicted in FIG. 13 is substantially identical to the guided rotor compressor  10  disclosed in U.S. Pat. No. 5,431,551, the entire disclosure of which is hereby incorporated by reference into this patent application. This guided rotor compressor is preferably comprised of a housing comprising a curved inner surface with a profile equidistant from a trochoidal curve, an eccentric mounted on a shaft disposed within said housing, a first rotor mounted on said eccentric shaft which is comprised of a first side, a second side, and a third side, a first partial bore disposed at the intersection of said first side and said second side, a second partial bore disposed at the intersection of said second side and said third side, a third partial bore disposed at the intersection of said third side and said first side, a first solid roller disposed and rotatably mounted within said first partial bore, a second solid roller disposed and rotatably mounted within said second partial bore, and a third solid roller disposed and rotatably mounted within said third partial bore. 
     The rotor is comprised of a front face, a back face, said first side, said second side, and said third side. A first opening is formed between and communicates between said front face and said first side, a second opening is formed between and communicates between said back face and said first side, wherein each of said first opening and said second opening is substantially equidistant and symmetrical between said first partial bore and said second partial bore. A third opening is formed between and communicates between said front face and said second side. A fourth opening is formed between and communicates between said back face and said second side, wherein each of said third opening and said fourth opening is substantially equidistant and symmetrical between said second partial bore and said third partial bore. A fifth opening is formed between and communicates between said front face and said third side. A sixth opening is formed between and communicates between said back face and said third side, wherein each of said fifth opening and said sixth opening is substantially equidistant and symmetrical between said third partial bore and said first partial bore. 
     Each of said first partial bore, said second partial bore, and said third partial bore is comprised of a centerpoint which, as said rotary device rotates, moves along said trochoidal curve. 
     Each of said first opening, said second opening, said third opening, said fourth opening, said fifth opening, and said sixth opening has a substantially U-shaped cross-sectional shape defined by a first linear side, a second linear side, and an arcuate section joining said first linear side and said second linear side. The first linear side and the second linear side are disposed with respect to each other at an angle of less than ninety degrees; and said substantially U-shaped cross-sectional shape has a depth which is at least equal to its width. 
     The diameter of said first roller is equal to the diameter of said second solid roller, and the diameter of said second solid roller is equal to the diameter of said third solid roller. 
     The widths of each of said first opening, said second opening, said third opening, said fourth opening, said fifth opening, and said sixth opening are substantially the same, and the width of each of said openings is less than the diameter of said first solid roller. 
     Each of said first side, said second side, and said third side has substantially the same geometry and size and is a composite shape comprised of a first section and a second section, where in said first section has a shape which is different from that of said second section. 
     The aforementioned compressor is a very preferred embodiment of the rotary positive displacement compressor which may be used as compressor  316 ; it is substantially smaller, more reliable, more durable, and quieter than prior art compressors. However, one may use other rotary positive displacement compressors such as, e.g., one or more of the compressors described in U.S. Pat. Nos. 5,605,124, 5,597,287, 5,537,974, 5,522,356, 5,489,199, 5,459,358, 5,410,998, 5,063,750, 4,531,899, and the like. The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification. 
     In one preferred embodiment, the rotary positive displacement compressor used as compressor  316  is a Guided Rotor Compressor which is sold by the Phoenix Engine and Compressor Corporation of 210 Pennsylvania Avenue, East Aurora, N.Y. 
     Referring again to FIG. 13, it will be seen that the compressed gas from compressor  316  is fed via line  313  to micro turbine generator  314 . As is disclosed in U.S. Pat. No. 5,810,524 (see, e.g., claim 1 thereof), such micro turbine generator  314  is a turbogenerator set including a turbogenerator power controller, wherein said turbogenerator also includes a compressor, a turbine, a combustor with a plurality of gaseous fuel nozzles and a plurality of air inlets, and a permanent magnet motor generator; see, e.g., FIGS. 1 and 2 of such patent and the description associated with such Figures. 
     The assignee of U.S. Pat. No. 5,819,524 manufactures and sells micro turbine generators, such as those described in its patent. 
     Similar micro turbine generators  314  are also manufactured and sold by Elliott Energy Systems company of 2901 S.E. Monroe Street, Stuart, Fla. 34997 as “The TA Series Turbo Alternator.” 
     Such micro turbines are also manufactured by the Northern Research and Engineering Corporation (NREC), of Boston, Mass., which is a wholly-owned subsidiary of Ingersoll-Rand Company; see, e.g., page 64 of the June, 1998 issue of “Diesel &amp; Gas Turbine Worldwide.” These micro turbines are adapted to be used with either generators (to produce micro turbine generators) or, alternatively, without such generators in mechanical drive applications. It will be apparent to those skilled in the art that applicants&#39; rotary positive displacement device may be used with either of these applications. 
     In general, and as is known to those skilled in the art, the micro turbine generator  314  is comprised of a radial, mixed flow or axial, turbine and compressor and a generator rotor and stator. The system also contains a combustor, bearings and bearings lubrication system. The micro turbine generator  314  operates on a Brayton cycle of the open type; see, e.g., page 48 of the June,  1998  issue of “Diesel &amp; Gas Turbine Worldwide.” 
     Referring again to FIG. 13, and in the preferred embodiment depicted therein, it will be seen that natural gas is fed via line  310  to manual ball valve  318  and thence to Y-strainer  320 , which removes any heavy, solid particles entrained within the gas stream. The gas is then passed to check valve  322 , which prevents backflow of the natural gas. Relief valve  324  prevents overpressurization of the system. 
     The natural gas is then fed via line  326  to the compressor  316 , which is described elsewhere in this specification in detail. Referring to FIG. 13, it will be seen that compressor  316  is operatively connected via distance piece  328 , housing a coupling (not shown) which connects the shafts (not shown) of compressor  316  and electric motor  330 . The compressor  316 , distance piece  328 , and electric motor  330  are mounted on or near a receiving tank, which receives and separates a substantial portion of the oil used in compressor  316 . 
     Referring again to FIG. 13, when the compressor  316  has compressed a portion of natural gas, such natural gas also contains some oil. The gas/oil mixture is then fed via line  334  to check valve  336  (which prevents backflow), and thence to relief valve  338  (which prevents overpressurization), and then via line  340  to radiator/heat exchanger  342 . 
     Referring again to FIG. 13, it will be seen that oil is charged into the system via line  344  through plug  346 . Any conventional oil or lubricating fluid may be used; in one embodiment, automatic transmission fluid sold as “ATF” by automotive supply houses is used. 
     A portion of the oil which was introduced via line  344  resides in the bottom of tank  332 . This portion of the oil is pressurized by the natural gas in the tank, and the pressurized oil is then pushed by pressurized gas through line  348 , through check valve (to eliminate back flow), and then past needle valve  352 , into radiator  354 ; a similar needle valve  352  may be used after the radiator  354 . The oil flowing into radiator  354  is then cooled to a temperature which generally is from about 10 to about 30 degrees Fahrenheit above the ambient air temperature. The cooled oil then exits radiator  354  via line  356 , passes through oil filter  358 , and then is returned to compressor  316  where it is injected; the injection is controlled by solenoid valve  360 . 
     In the preferred embodiment depicted in FIG. 13, a fan  362  is shown as the cooling means; this fan is preferably driven by motor  364 ; in the preferred embodiment depicted in FIG. 13, air is drawn through radiators  342  and  354  in the direction of arrows  363 . As will be apparent to those skilled in the art, other cooling means (such as water cooling) also and/or alternatively may be used. 
     Referring again to FIG. 13, the cooled oil and gas mixture from radiator  342  is passed via line  366  through ball valve  368  and then introduced into tank  332  at point  370 . 
     In the operation of the system depicted in FIG. 13, a sight gauge  380  provides visual indication of how much oil is in receiving tank  332 . When an excess of such oil is present, it may be drained via manual valve  384 . In general, it is preferred to have from about 20 to about 30 volume percent of the tank be comprised of oil. 
     Referring again to FIG. 13, compressed gas may be delivered to turbogenerator  314  through port  386 , which is preferably located on receiving tank  332  but above the oil level (not shown) in such tank. Bypass line  388  and pressure relief valve  390  allows excess gas flow to be diverted back into inlet line  326 . That gas which is not in bypass line  388  flows via line  313  through check valve  392  (to prevent backflow), manual valve  394  and thence to turbogenerator  314 . 
     Thus, and again referring to FIG. 13, it will be seen that, in this preferred embodiment, there is a turbo alternator  314 , an oil lubricated rotary displacement compressor  316 , a receiving tank  332 , a means  310  for feeding gas to the rotary positive displacement compressor, a means  346  for feeding oil to the receiving tank, a means  342  for cooling a mixture of gas and oil, a means  332  for separating a mixture of gas and oil, and a means  356  for feeding oil to the rotary positive displacement compressor. 
     In the preferred embodiment depicted in FIG. 13, there are two separate means for controlling the flow capacity of compressor  316 . One such means, discussed elsewhere in this specification as a bypass loop, is the combination of port  386 , line  388 , relief valve  390 , and line  391 . Another such means is to control the inlet flow of the natural gas by means of control valve  396 . As will be apparent, both such means, singly or in combination, exert their control in response to the gas needs of turbogenerator  314 . 
     FIG. 14 is a schematic representation of a hybrid booster system  420  which is comprised of a rotary positive displacement device assembly  422  operatively connected via line  424  to a reciprocating compressor  426 . 
     Rotary positive displacement device assembly  422  may be comprised of one or more of the rotary positive displacement devices depicted in either FIGS. 1-8 (with solid rollers) and/or  9 - 11  (hollow rollers). Alternatively, or additionally, the displacement device  422  may be comprised of one or more of the rotary compressors claimed in U.S. Pat. No. 5,769,619, the entire disclosure of which is hereby incorporated by reference into this specification. 
     U.S. Pat. No. 5,769,619 claims a rotary device comprised of a housing comprising a curved inner surface in the shape of a trochoid and an interior wall, an eccentric mounted on a shaft disposed within said housing, a first rotor mounted on said eccentric shaft which is comprised of a first side and a seocnd side, a first pin attached to said rotor and extending from said rotor to said interior wall of said housing, and a second pin attached to said rotor and extending from said rotor to said interior wall of said housing, and a third pin attached to said rotor and extending from said rotor to said interior wall of said housing. A continuously arcuate track is disposed within said interior wall of said housing, wherein said continuously arcuate track is in the shape of an envoluted trochoid. Each of said first pin, said second pin, and said third pin has a distal end which is disposed within said continuously arcuate track. Each of said first pin, said second pin, and said third pin has a distal end comprised of a shaft disposed within a rotatable sleeve. The rotor is comprised of a multiplicity of apices, wherein each such apex forms a compliant seal with said curved inner surface, and wherein each said apex is comprised of a separate curved surface which is formed from a strip of material pressed into a recess. The curved inner surface of the housing is generated from an ideal epictrochoidal curve and is outwardly recessed from said ideal epitrochoidal curve by a distance of from about 0.05 to about 5 times as great as the eccentricity of said eccentric. The diameter of the distal end of each of said first pin and said second pin is from about 2 to about 4 times as great as the eccentricity of the eccentric. Each of the first pin, the second pin, and the third pin extends from beyond the interior wall of the housing by from about 2 to about 2 times the diameter of each of said pins. 
     Referring again to FIG. 14, it is preferred that several rotary positive displacement devices  10  and  10 ′ be used to compress the gas ultimately fed via line  424  to reciprocating positive compressor  426 . As is disclosed in U.S. Pat. No. 5,431,551, the devices  10  and  10 ′ are staged to provide a multiplicity of fluid compression means in series. 
     Thus, as was disclosed in U.S. Pat. No. 5,431,551 (see lines 62 et seq. of column 9), “In one embodiment, not shown, a series of four rotors are used to compress natural gas. The first two stacked rotors are substantially identical and relatively large; they are 180 degrees out of phase with each other; and they are used to compress natural gas to an intermediate pressure level of from about 150 to about 200 p.s.i.g. The third stacked rotor, which comprises the second stage of the device, is substantially smaller than the first two and compresses the natural gas to a higher pressure of from about 800 to about 1,000 p.s.i.g. The last stacked compressor, which is yet smaller, is the third stage of the device and compresses the natural gas to a pressure of from about 3,600 to about 4,500 p.s.i.g.” 
     Many other staged compressor circuits will be apparent to those skilled in the art. What is common to all of them, however, is the presence of at least one rotary positive displacement device  10  whose output is directly or indirectly operatively connected to at least one cylinder of a reciprocating positive displacement compressor  426 . 
     One may use any of the reciprocating positive displacement compressor designs well known to the art. Thus, by way of illustration and not limitation, one may use one or more of the reciprocating positive compressor designs disclosed in U.S. Pat. Nos. 5,811,669, 5,457,964, 5,411,054, 5,311,902, 4,345,880, 4332,144, 3,965,253, 3,719,749, 3,656,905, 3,585,451, and the like. The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification. 
     Referring again to FIG. 14, it will be apparent that reciprocating positive displacement compressor  426  may be comprised of one or more stages. In the preferred embodiment depicted, compressor  426  is comprised of stages  428  and  430 . 
     Referring again to FIG. 14, an electric motor  432  connected by shafts  434  and  436  is operatively connected to compressors  428 / 430  and  10 / 10 ′. It will be apparent that many other such drive assemblies may be used. 
     In one embodiment, not shown, the gas from one stage of either the  10 / 10 ′ assembly and/or the  428 / 430  assembly is cooled prior to the time it is passed to the next stage. In this embodiment, it is preferred to cool the gas exiting each stage at least about 10 degrees Fahrenheit prior to the time it is introduced to the next compressor stage. 
     FIG. 15 depicts an assembly  450  similar to the assembly  420  depicted in FIG.  14 . Referring to FIG. 15, it will be seen that gas is fed to compressor assembly  10 / 10 ′ by line  452 . In this embodiment, some pressurized gas at an intermediate pressure is fed from compressor  10  via line  454  to turbine or micro-turbine or fuel cell  456 . Alternatively, or additionally, gas is fed to electrical generation assembly  456  by a separate compressor (not shown). 
     The electrical output from electrical generation assembly  456  is used, at least in part, to power electrical motor  432 . Additionally, electrical power is fed via lines  458  and/or  460  to an electrical vehicle recharging station  462  and/or to an electrical load  464 . 
     Referring again to FIG. 15, and in the preferred embodiment depicted therein, waste heat produced in turbine/microturbine/fuel cell  456  is fed via line  466  to a heat load  468 , where the heat can be advantageously utilized, such as, e.g., heating means, cooling means, industrial processes, etc. Additionally, the high pressure discharge from compressor  430  is fed via line  470  to a compressed natural gas refueling system  472 . 
     In one embodiment, not shown, guided rotor assembly  10 / 10 ′ is replaced is conventional compressor means such as reciprocating compressor, or other positive displacement compressor. Alternatively, or additionally, the reciprocating compressor assembly may be replaced by one or more rotary positive displacement devices which, preferably, are adapted to produce a more highly pressurized gas output the either compressor  10  or compressor  10 ′. Such an arrangement is illustrated in FIG. 16, wherein rotary positive displacement devices  11 / 11 ′ are higher pressure compressors used. In one embodiment, not shown, separate electrical motors are used to power one or more different compressors. 
     FIG. 17 is a schematic representation of an assembly  500  in which electrical generation assembly  456  is used to power a motor  502  which is turn provides power to rotary positive displacement device  504 . Gas from well head  506  is passed via line  508 , and pressurized gas from rotary positive displacement device  504  is fed via line  510  to electrical generation assembly  456 , wherein it is converted to electrical energy. Some of this energy is fed via line  512  to electric motor  432 , which provides motive power to a single or multi-compressor guided rotary compressor  514 ; this “well head booster” may be similar in design to the compressor assembly illustrated in FIGS. 1-8, or to the compressor assembly illustrated in FIGS. 9-12, and it may contain one more compressor stages. The output from rotary positive displacement assembly  514  may be sent via line  516  to gas processing and/or gas transmission lines. The input to rotary positive displacement assembly  514  may come from well head  518 , which may be (but need not be) the same well head as well head  516 , via line  520 . 
     Multistage Rotor Assembly 
     FIG. 18 is a sectional view of a multistage rotor assembly  600  which is comprised of a shaft  602  integrally connected to eccentric  604  and eccentric  606 . The rotating shaft  600 /eccentric  604 /eccentric  606  assembly is supported by main bearings  608  and  610 ; eccentrics  604  and  606  are disposed within bearings  612  and  614 ; and the eccentrics  604 / 606  and bearings  612 / 614  assemblies are disposed within guided rotors  616  and  618 . This arrangement is somewhat similar to that depicted in FIG. 1, wherein eccentric  52  is disposed within guided rotor  60 . 
     As will be apparent to those skilled in the art, one shaft  602  is being used to translate two rotors  616  and  618 . The gas to be compressed is introduced into port  620  and then introduced into the volume created by the rotor  616  and the housing  622 . The compressed gas from the volume created by the rotor  616  and the housing  622  is then introduced within an annulus  624  within intermediate plate  626  via port  628  and then sent into the volume created by rotor  618  and housing  630  through port  632 . After being further compressed in this second rotor system, it is then sent to discharge annulus  632  within discharge housing  634  by port  636 . 
     Referring to FIG. 1, it will be seen that guided rotor assembly  10  has a housing  12  with a thickness  640  which is slightly larger than the thickness of the rotor  16  disposed within such housing (see FIG.  1 ). Similarly, the thickness  642  of rotor assembly  616 , and the thickness  644  of rotor assembly  618  are also slightly smaller than the thicknesses of the housings in which the guided rotors are disposed. 
     It is preferred that the thickness  644  be less than the thickness  642 . In one embodiment, thickness  642  is at least 1.1 times as great as the thickness  644  and, preferably, at least 1.5 times as great as the thickness  644 . 
     It will be apparent that, with the assembly  600  of FIG. 18, one can achieve higher pressures with lower operating costs. 
     A Hermetically Sealed Guided Rotor Apparatus 
     FIG. 19 illustrates an guided rotor assembly  670  comprised of a multiplicity of guided rotors  672  and  674 . Shaft  676  is rotated by electric motor  678  which, in the embodiment depicted, is comprised of motor shaft  680 , motor rotor  682 , and stator  684  supported by bearings  686  and  688 . The motor shaft  680  is directly coupled to compressor shaft  676  by means a coupling  690 . 
     The compressor shaft  676  rotates one or more of rotors  672  and  674 , which may be of the same size, a different size, of the same function, and/or of a different function. 
     The motor  678  is cooled by incoming gas (not shown), and such incoming gas is then passed to compressor  692 , wherein it is distributed equally to the rotor assemblies  672  and  674 , which are disposed within housings  694  and  696 , respectively. 
     In the embodiment depicted in FIG. 19, the rotor assemblies  674  and  676  have substantially the same geometry and capacity. In another embodiment, not shown, the rotor assemblies  674  and  674  have different geometries and/or capacities. 
     Referring again to FIG. 19, it will be seen that the entire compressor and drive assembly is disposed within hermetic enclosure  698 . The end flange  700  is form an interface  702  with enclosure  698  which is a hermetic seal. 
     FIG. 20 is a schematic of an assembly  750  for generating electric power and recovering thermal energy for other useful work. Referring to FIG. 20, it will be seen that a multiplicity of micro turbines  752 ,  754 ,  756 , and  758  are used to generate electricity which, in the embodiment depicted, is fed from the unit at outlet  760 . 
     In one embodiment, a micro turbine such as those sold by the Capstone Turbine Corporation of Woodland Hills, Calif. may be used. Thus, e.g., the Model 330 Capstone Micro Turbine may be used. Thus, e.g., one may use one or more of the micro turbines disclosed in U.S. Pat. Nos. 5,903,116, 5,899,673, 5,850,733, 5,819,524, and the like. The disclosure of each of these United States patents is hereby incorporated by reference into this specification. 
     Referring again to FIG. 20, the heat, discharged from one or more of micro turbines  752 ,  754 ,  756 , and/or  758  is passed to waste heat boilers  760  and/or  762 , wherein the waste heat is used to heat fluid, such as water, and to preferably generate either hot water or steam. The hot fluid from waste heat boilers  760  and/or  762  is then passed via lines  764  and  766  to industrial processes  768  and  770 . Any industrial or commercial processes which utilize heat energy may be used in the process. Thus, the waste heat may be used to heat or cool working space, inventory space, etc.; it may be used to heat chemical reagents; it may, in fact, be used in any process which requires heat. Conventional means, such as pipes, heat exchangers, and the like (see, e.g., heat exchanger  771 ) may be used to extract heat from the heated fluid. 
     In one embodiment, not shown, the exhaust gases from micro turbines  752 ,  754 ,  756 , and/or  758  into the air inlet of a combustion boiler, or into any other device which can profitably utilize such hot gasses. 
     Referring again to FIG. 20, it will be seen that a multiplicity of guided rotor compressors  772  and  774  supply compressed natural gas to the micro turbines  752 ,  754 ,  756 , and/or  758 . Accumulator  776  accumulates compressed gas produced by compressors  772  and/or  774 ; and, as needed, it also may supply compressed gas to micro turbines  752 ,  754 ,  756 , and  758 . 
     A Process for Controlling Compressors 
     FIG. 21 is a schematic diagram of a system  800  for generating electricity which is comprised of a multiplicity of microturbines  752 ,  754 ,  756 , and  758  which are described elsewhere in this specification. The system  800  also is comprised of a multiplicity of compressors  802 ,  804 , and  806 . 
     Although four microturbines  752  et seq. are shown in the system depicted in FIG. 21, fewer or more microturbines can be used. It is preferred to use at least two such microturbines in the system  800 , but one can use many more in such system such as, e.g., 60 microturbines. 
     Although three compressors  802  et seq. are shown in the system depicted in FIG. 21, fewer or more such compressors may be used. It is preferred to use at least two such compressors in the system  800 , but one can use many more such compressors such as, e.g., 60 compressors. 
     One may use the guided rotor compressor, described and claimed in U.S. Pat. No. 5,431,551, as one or more of the compressors in system  800 . Alternatively, or additionally, one may use one or more of the “hollow roller compressors,” described elsewhere in this specification, as one or more of the compressors in system  800 . Alternatively, or additionally, one may use other types of compressors such as, e.g., scroll compressors, vane compressors, twin screw compressors, reciprocating compressors, continuous flow compressors, and the like. 
     Regardless of the compressor, it should be capable of compressing gas to a pressure of from about 40 to about 500 pounds per square inch and of delivering such compressed gas at a flow rate of from about 5 to about 200 standard cubic feet per minute (“scfm”). The term “scfm” is well known to those skilled in the art, and means for measuring it are also well known. See, e.g. U.S. Pat. Nos. 5,672,827, 4,977,921, 5,695,641, 5,664,426, 5,597,491, and the like. The disclosure of each of these United States patents is hereby incorporated by reference into this specification. 
     Referring to FIG. 21, when system  800  has been shut down and is in the process of just starting up, compressed gas at a pressure of from about 40 to about 500 pounds per square inch is first delivered to microturbine  752 . 
     In the embodiment depicted in FIG. 21, it is preferred to use a pressure regulator  836  in line  313  to insure that gas delivered to microturbine(s)  752  and/or  754  and/or  756  and/or  758  is stable and remains within a specified range of gas pressure. 
     In the embodiment shown in Figure, reservoir  808  generally will contain a source of compressed gas at a pressure of from about 40 to about 500 pounds per square inch, and this compressed gas may be fed via lines  313  and  810  to microturbine  752 . 
     Reservoir  808  can be any container sufficient for storing and/or dispensing gas at a pressure of from about 40 to about 500 pounds per square inch. Thus, by way of illustration and not limitation, one may use any of the gas storage vessels disclosed in U.S. Pat. Nos. 5,908,134, 5,901,758, 5,826,632, 5,798,156, 5,997,611, and the like. The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification. 
     In the embodiment depicted in FIG. 21, gas storage vessel  808  acts as the initial supply of compressed gas to microturbine  752 . In another embodiment, not shown, gas storage vessel  808  is not used in the system and compressed gas is fed to microturbine  752  from another initial gas source such as, e.g., gas delivery line  810 . 
     Referring again to FIG. 21, after the compressed gas has been delivered to microturbine  752  from either storage vessel  808  and/or line  810 , the microturbine starts operation. In the embodiment depicted in FIG. 21, each of microturbines  752 ,  754 ,  756 , and  758  is comprised of its own controller which, in response to the introduction of gas to such microturbine, starts it in operation. In another embodiment, a central controller operatively connected to each of microturbines  752 ,  754 ,  756 , and  758 , and to each of compressors  802 ,  804 , and  806 , is utilized. 
     Referring again to FIG. 21, each of compressors  802 ,  804 , and  806  is operatively connected to a controller  812 ,  814 , and  816 , respectively. In another embodiment, not shown, one controller (not shown) is connected to each of the compressors; this controller might be a computer, a programmable logic controller, etc. In one aspect of this latter embodiment, one controller is operatively connected to each of the compressors, but such unitary controller includes a separate gas pressure sensor device for each such compressor. It is preferred, regardless whether one uses one or more controllers, that each such controller contain a separate gas sensing device for each compressor. 
     Regardless of which controller or controllers are connected to the compressors  802 ,  04 , and  806 , it is preferred that such controllers(s) be comprised of pressure sensing means (not shown) for measuring the pressure of gas. Thus, for example, the pressure sensing means may be pressure switches which combine the function of pressure sensing and electrical switching. Thus, e.g., the pressure sensing means may be pressure transducers adapted to provide a signal to a programmable logic controller. 
     Regardless of the pressure sensing means used, such means is adapted to determine the pressure within either vessel  808  and/or line  810 . When such pressure is outside of a specified desired range of a pressure, but is within the broad pressure range of from about 40 to about 500 pounds per square inch, the pressure sensing means acts as a switch to turn one or more of compressors  802 ,  804 , and/or  806  on or off, depending upon the pressure sensed. 
     Referring again to FIG. 21, the controllers  812 ,  814 , and  816  are operatively connected to compressors  806 ,  804 , and  802 , respectively, by lines  818  and  820 ,  822  and  824 , and  826  and  828 , respectively. It should be noted that lines  820 ,  824 , and  828 , in one embodiment, preferably comprise a manual switch  830 ,  832 , and  834 , respectively to allow one to manually control each of the compressors. 
     As will be apparent to those skilled in the art, one or more of the manual switches  830 ,  832 , and/or  834  may be used in conjunction with the controllers  812 ,  814 , and  816 . When one or more of the controllers  812 ,  814 , and/or  816  are connected in the system  800 , the manual switches may be used to disconnect the compressors and negate the effects of the controllers. If the controllers  812 ,  814 , and/or  816  are omitted from system  800 , one may manually perform the operations of such controllers by using such switches in response to gas pressure readings may be manual means. 
     In one embodiment, the controllers  812 ,  814 , and  816  are programmed to turn compressors  802 ,  804 , and  806  on sequentially, in response to the presence of different gas pressure levels within either vessel  808  or line  810 . This feature will be illustrated later in the specification by reference to FIG.  23 . 
     Thus, in one typical embodiment, compressor  802  will be turned on when the gas pressure in vessel  808  and/or line  810  is less than, e.g., 60 pounds per square inch; compressors  802 ,  804 , and  806  may be fed gas from gas lines  310 ,  311 ,  313 , and  315 . When this condition occurs, compressor  802  will be switched on and will cause compressed gas to flow to microturbine  752  at a flow rate of, e.g., 7 standard cubic feet per minute. 
     During the operation of compressor  802 , and as long as the gas flow from compressor  802  is sufficient to meet the needs of whichever of microturbines  752 ,  754 ,  756 , and/or  758  is running, the gas pressure within vessel  808  and line  810  preferably remains at a specified value such as, e.g., 60 pounds per square inch. 
     After controller  816  has activated compressor  802 , when one or more of the sensors in controller  814  senses that the gas pressure within vessel  808  and line  810  has dropped below a desired value, such as, e.g., 55 pounds per square inch, it will then turn on compressor  804  so that it is operating in addition to compressor  802 . 
     Similarly, when compressors  802  and  804  are running, and the sensor in, e.g., controller  812  senses that the gas pressure within vessel  808  and/or line  810  has dropped below a desired value such as, e.g., 50 pounds per square inch, it will turn on compressor  806 . 
     The same process may be used in the reverse order, when one or more of the controllers  812 ,  814 , and  816  sense that the pressure within vessel  808  and/or line  810  exceeds a certain predetermined value. Thus, e.g., compressor  806  may be turned off when the pressure sensed is greater than about, e.g., 65 pounds per square inch, compressor  804  may be turned off when the pressure sensed is greater than about, e.g., 66 pounds per square inch, and compressor  802  may be turned off when the pressure sensed is greater than about 67 pounds per square inch. 
     As will be apparent to those skilled in the art, other conditions and sequences may be used. What is common to all of the processes, however, is the sequential turning on and/or turning off of a multiplicity of compressors. 
     FIG. 22 illustrates one preferred means of providing pressure relief in an electricity generating system  800 . 
     Referring to FIG. 22, when the pressure within pressure vessel  808  exceeds a specified value, pressure relief valve  850  allows such pressure to vent via line  852  to atmosphere. Thus, e.g., valve  850  can be set to open when, e.g., the pressure within vessel  808  exceeds, e.g., 150 pounds per square inch. 
     A bypass relief valve  854  is set to open whenever the pressure within vessel  808  exceeds a specified value. In one embodiment, the pressure required to actuate valve  850  is greater than the pressure required to actuate valve  854 ; if the former pressure, e.g., may 150 pounds per square inch and the latter pressure may be, e.g., 70 pounds per square inch. As will be apparent to those skilled in the art, the actual actuation points for valves  850  and  854  will vary depending upon factors such as the rating of the vessel  808 , the power ratings of compressors  802 ,  804 , and  806 , the pressures required in the system, etc. 
     Referring again to FIG. 22, when valve  854  is actuated, gas flows from vessel  808  through line  856  and then through check valve  858  back into line  310  at point  860 . Check valve  862  prevents gas recycled into the system at point  860  from flowing back to the original gas supply  864 . 
     Referring again to FIG. 22, and in the preferred embodiment depicted therein, it will be seen that each of compressors  802 ,  804 , and  806  is comprised of a pressure relief valve  866 ,  868 , and  870  which, when the pressure within the compressor discharge  872 ,  874 , and  876  exceeds a certain specified value, gas is vented to the atmosphere  878 . Thus, e.g., pressure relief valves  866 ,  868 , and  870  may be designed to actuate at a pressure of, e.g., 150 pounds per square inch. 
     When the gas pressure at compressor discharge  872 ,  874 , and  876  is less than the pressure required to actuate valves  866 ,  868  and  870  but is more than another specified value (such as, e.g., 80 pounds per square inch), bypass relief valves  880 ,  882 , and  884  open and flow gas through lines  886 ,  888 , and  890  through check valves  892 ,  894 , and  896  and thence back into lines  311 ,  313 , and  315 . In one embodiment, the relief valves  880 ,  882 , and  884  are set to be actuated at levels somewhat lower than the settings in controllers  816 ,  814 , and  812  for turning the compressors off (see FIG.  21 ). 
     Referring again to FIG. 22, it will be seen that the gas exiting from compressors  802 ,  804 , and  806  via lines  898 ,  900 , and  902  pass through check valves  904 ,  906 , and  908  which can be used to prevent backflow. 
     FIG. 23 is a graph of pressure versus the number of compressors operating, in the system depicted in FIG.  21 . 
     As is illustrated in FIG. 23, the pressure PI, which is within the range defined by points  910  and  912 , exists when each of compressors  802 ,  804 , and  806  are operating. The pressure P 2 , which is within the range defined by points  914  and  916 , exists when only compressors  802  and  804  are operating. The pressure P 3 , which is defined by the points  918  and  920 , exists when only compressor  802  is operating. The pressure P 4 , which is defined by a pressure in excess of the pressure at point  920 , exists when the pressure vessel  808  has a pressure outside of the desired range and at least one compressor is operating and producing pressure outside of the desired range, which causes bypass relief valve  854  (see FIG. 21) to open and reduce the pressure at or below level  920 . 
     It is to be understood that the aforementioned description is illustrative only and that changes can be made in the apparatus, in the ingredients and their proportions, and in the sequence of combinations and process steps, as well as in other aspects of the invention discussed herein, without departing from the scope of the invention as defined in the following claims.