Apparatus for generating electricity

An apparatus for generating electric current which includes an integrated system comprising a fuel cell which is interconnected with two or more turbocompressors in a manner so as to increase the pressure of atmospheric oxygen fed to a fuel cell by utilizing the potential energy of the exhaust of the fuel cell as well as the potential energy of a source of fuel under pressure.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to apparatus for generating 
electric current. More particularly, the invention concerns an integrated 
system comprising a fuel cell which is interconnected with a pair of 
turbocompressors in a manner so as to increase the pressure of atmospheric 
oxygen fed to a fuel cell by utilizing the potential energy of the exhaust 
of the fuel cell as well as the potential energy of a source of fuel under 
pressure. 
2. Discussion of the Invention 
A fuel cell is a device in which the energy released in the oxidation of a 
conventional fuel is made directly available in the form of an electric 
current. Although the principle of the fuel cell was formulated as long 
ago as 1894, it is only in recent years that reasonably efficient fuel 
cells have been constructed and put to practical use for generating 
electricity in many applications, including vehicular propulsion. 
Typically the fuel cell operates by bringing together a fuel gas, as for 
example hydrogen, and oxygen, typically taken from the atmosphere. 
Generally the hydrogen fuel is bottled under high pressure, liquefied, or 
chemically bound. The reactants are combined in a vessel under some 
convenient combination of pressure and temperature, for example, 10 to 40 
pounds per square inch gauge and 220 degrees Fahrenheit. The so called 
Proton Exchange Membrane (PEM) fuel cell represents a typical prior art 
fuel cell usable in the apparatus of the invention, but the invention is 
not limited to the use of this type of cell. 
A typical PEM fuel cell operates by combining oxygen and hydrogen across a 
membrane while developing an electromotive potential between two 
electrodes placed on either side of the membrane. The process also 
releases heat which increases the temperature of the reacting fluids and 
tends to vaporize the newly formed water. 
Although the oxygen could be supplied in pure molecular form (this is done 
for some applications, e.g. space and submarine), earthbound fuel cells 
use atmospheric air as the source of the oxygen, which is pumped into the 
fuel cell together with the nitrogen, carbon dioxide, argon, moisture and 
any other trace gases present in the air. The excess water formed in the 
cell reaction is generally removed as water vapor entrained in the exhaust 
of the non-reacting nitrogen, carbon dioxide, etc. from the fuel cell back 
to the atmosphere. 
In practice the removal of the water in the form of saturated vapor 
requires a volume of entraining gas larger than the volume containing the 
stoichiometric quantity of oxygen reacted to form the water to be removed. 
Typically, complete removal of the water requires a volume of air 
approximately 1.5 times larger than stoichiometric. This imbalance has the 
consequence that the exhaust gas also contains a percentage of unreacted 
oxygen. Assuming that atmospheric air contains, in round numbers, 80% 
nitrogen and 20% oxygen (and neglecting for simplicity the minor 
constituents) the reaction: 
EQU 2H+O.fwdarw.H.sub.2 O+heat 
or indicating complete molecules, 
EQU 2H.sub.2 +O.sub.2 .fwdarw.2H.sub.2 O+heat 
becomes 
EQU 2H+1.5O+6N+. . . .fwdarw.H.sub.2 O+0.50+6N+heat 
or indicating complete molecules, 
EQU 4H.sub.2 +3O.sub.2 +12N.sub.2 +. . . .fwdarw.4H.sub.2 O+O.sub.2 +12N.sub.2 
+. . .+heat 
The enthalpy of the exhaust gas is available for use in a turbine, which 
can operate with a typical efficiency of 85-90% when built in accordance 
with the state of the art for the dimensions and RPM appropriate to the 
applications. 
The power developed by the turbine is coupled to a centrifugal compressor 
matched to the turbine RPM through a shaft comprising a gas bearing as 
illustrated for example in FIG. 7 of U.S. Pat. No. 4,808,070, which issued 
to the present inventor. Since the efficiency of the state-of-the art 
centrifugal compressor is typically 70-75%, the power developed in the 
turbine may not be sufficient (depending on the temperature of the exhaust 
flow) to compress the air to the desired pressure. In any event, a 
single-stage centrifugal compressor has a practical limit of about 1.8:1 
for the ratio of absolute pressure of the discharge over the inlet, or 12 
psig. discharge for an atmospheric inlet. If the desired operating 
pressure of the fuel cell is higher than this, two or more stages will be 
required, and the upper stages can be driven by expanding hydrogen through 
turbines rather than through a regulator valve. For simplicity a two-stage 
system is discussed hereafter. 
As a general rule, in operating a fuel cell of conventional construction, 
the pressure of the hydrogen must be lowered from that existing in the 
storage bottle, while the pressure of the oxygen taken from atmosphere 
must be increased above atmospheric pressure. In prior art devices, these 
pressure changes are accomplished by means of a regulator valve, in the 
case of the hydrogen, and by a compressor, in the case of the oxygen. 
Generally, in operating the prior art fuel cell, the power needed to run 
the compressor is taken from the electrical output of the fuel cell and 
can constitute a substantial fraction thereof. In addition, the compressor 
used in prior art applications requires lubrication which is typically 
supplied by various types of lubricating means. The lubricating means 
generally increases the complexity, weight and cost of the operating 
system and offers a finite possibility of undesirable contamination of the 
fuel cell with lubricants. 
In carefully analyzing fuel cell operation it became apparent to the 
present inventor that there are at least two sources of energy that can be 
used to directly drive a compressor. One such source is the potential 
energy of the exhaust gas expanding from the fuel cell operating pressure 
to atmospheric pressure. Another source of energy is the potential energy 
of the compressed hydrogen expanding from the reservoir to the fuel cell 
itself. In typical prior art system, this latter source of energy is 
dissipated by dropping the pressure through one or more regulating valves. 
However, as will be better understood from the discussion which follows, 
this energy can be beneficially recovered by expanding the hydrogen 
through one or more turbines which are directly connected to one or more 
centrifugal compressors. It is this novel feature which comprises an 
important aspect of the apparatus of the present invention. More 
particularly, a significant contribution to the present invention was the 
realization by the present inventor that part of the pressurized hydrogen 
normally used as the fuel source effectively could be exploited to drive a 
turbine and the energy thus derived could be used to drive a centrifugal 
compressor which, in turn, could function to increase the pressure of the 
oxygen taken from atmosphere and supplied to the fuel cell. 
Another important aspect of the present invention involves the use in the 
apparatus of the invention of a novel gas bearing turbine of the character 
described in U.S. Pat. No. 4,808,070 issued to the present inventor. Use 
of this highly novel, non-lubricated fluid bearing turbine not only 
provides the high operating efficiency required in the present 
application, but also elegantly solves the contamination problem 
encountered as a result of the use of conventional lubricated turbines. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an integrated 
electrical power generating system which uses, in conjunction with a fuel 
cell, two or more turbocompressors that function to controllably increase 
the pressure of atmospheric oxygen fed to a fuel cell by utilizing the 
potential energy of the exhaust of the fuel cell augmented by the 
potential energy of the pressurized hydrogen which is used as the fuel 
source. 
Another object of the invention is to eliminate the need for a lubricated 
turbocompressor by using a gas bearing as disclosed in U.S. Pat. No. 
4,808,070 to provide the interconnection of an expansion turbine with the 
corresponding stage of a centrifugal compressor. 
Still another object of the invention is to provide an integrated system of 
the character described which embodies a fuel cell, turbine, bearing, and 
compressor which are interconnected together in a small, self-contained 
package. 
A further object of the invention is to prevent lubrication contamination 
the fuel cell caused by coupling the fuel cell with a turbine.

DESCRIPTION OF THE INVENTION 
Referring to the drawings and particularly FIG. 1, one form of the 
electrical current generating apparatus of the present invention is there 
illustrated and comprises a conventional fuel cell of the proton-exchange 
membrane character. The construction and operation of this type of fuel 
cell is well known to those skilled in the art and will not be discussed 
in detail herein. Such fuel cells comprise a housing 12 having first and 
second chambers 14 and 16 and a membrane 18 disposed intermediate first 
and second chambers 14 and 16 and an exhaust gas outlet 23. First chamber 
14 is provided with an air inlet 20 while second chamber 16 is provided 
with a hydrogen inlet 22. 
In a manner presently to be described in detail, a pair of turbocompressor 
units 24 and 26 are operably interconnected with the fuel cell. More 
particularly, in the form of the invention shown in FIGS. 1 and 2, a first 
drive means, which forms a part of turbocompressor 24, is connected to 
exhaust gas outlet 23 of second chamber 16 and is driven by the exhaust 
gases flowing therefrom. 
A first gas compressor means, which also forms a part of turbocompressor 
24, is drivably interconnected with first drive means, for compressing gas 
derived from atmosphere. 
A second gas compressor means, which forms a part of second turbocompressor 
26, has an inlet in communication with an outlet of the first gas 
compressor means and an outlet in communication with the inlet of first 
chamber 14 of housing 12 of the fuel cell. 
A second drive means, which forms a part of turbocompressor 26, is drivably 
interconnected with a second gas compressor means for driving the second 
gas compressor means. 
As shown in FIG. 1, the second drive means has a gas outlet 64 in 
communication with inlet 22 of second chamber 16 of the fuel cell. 
A fuel supply means, shown here as a hydrogen reservoir, has an outlet in 
communication with the inlet of the second drive means for driving the 
drive means. 
As best seen by now referring to FIG. 3, turbocompressor 24 comprises a 
support housing 30 having an inlet port 32 and an outlet port 34. An 
internal bore 36 extends longitudinally of housing 30 and defines a smooth 
inner surface. Rotatable within bore 36 is a shaft 38 having first and 
second ends 38a and 38b. Connected to shaft 38 proximate end 38a is a 
compressor wheel 40 which forms a part of the first gas compressor means 
of the invention. Connected to shaft 38 proximate opposite end 38b is a 
turbine wheel 42 which forms a part of the first drive means of the 
invention. As shown in FIG. 3, compressor wheel 40 is disposed proximate 
inlet port 32 while turbine wheel 42 is disposed proximate outlet port 34. 
It is to be understood that turbocompressor 26 is of identical construction 
to turbocompressor 24 and is of the configuration shown in FIG. 3. 
Reference to U.S. Pat. No. 4,808,070 issued to G. Fonda-Bonardi describes 
in greater detail the construction and operation of the turbocompressor 
shown in FIG. 2. U.S. Pat. No. 4,808,070 is incorporated herein by 
reference as though fully set forth herein, and reference should be made 
to this patent for additional details concerning the nature and operation 
of the gas bearing portions of turbocompressors 24 and 26. 
As more fully described in U.S. Pat. No. 4,808,070, bore 36 is generally 
circular in cross section at any point and is of a predetermined diameter. 
The inner surface of the bore is preferably generally smooth and 
uninterrupted. Shaft 38 is of a predetermined diameter less than the 
diameter of bore 36 and defines an elongated outer surface. Formed in the 
outer surface of the shaft are a plurality of circumferentially spaced, 
longitudinally extending recesses or cavities "C" of a pre-determined 
depth. Each cavity "C" defines along one margin thereof a radially, 
outwardly extending step "S" of a pre-determined height (see also U.S. 
Pat. No. 4,808,070, FIG. 3). 
Also formed in shaft 38 are a plurality of circumferentially spaced, 
longitudinally extending grooves or channels 44, the purpose of which is 
discussed in detail in U.S. Pat. No. 4,808,070. As discussed in this 
patent, as shaft 38 rotates, gas will be drawn into the space between the 
inner walls of the cylindrical bore and the outer surfaces of the shaft 
and will function to maintain precise concentricity of the shaft within 
the bore 36. As previously mentioned herein, the use of this novel gas 
bearing arrangement, not only provides the efficiency necessary to the 
optimum operation of the apparatus of the invention, but also elegantly 
removes any possibility of contaminating the fuel cells, since the 
turbocompressor construction shown in FIG. 3 requires the use of no 
lubricants. 
Turning once again to FIG. 1, it is to be noted that the first gas 
compressor means portion of turbocompressor assembly 24 has an outlet port 
50 which is appropriately interconnected as by a conduit 52 with an inlet 
port 54 of the second gas compressor means portion turbocompressor 
assembly 26. Turbocompressor assembly 26 also is provided with an inlet 
port 56 which is disposed proximate a turbine wheel 58. Operably 
interconnected with inlet 56 by means of a conduit 58 is a fuel supply 
means shown here as a bottle or reservoir 60 containing hydrogen under 
pressure. A suitable valve 62 is disposed in conduit 58 to control the 
flow of hydrogen under pressure toward inlet 56 of second drive means 
portion of turbocompressor assembly 26. An exhaust outlet 64 of the second 
drive means portion of turbocompressor 26 is interconnected with inlet 22 
of chamber 16 of the fuel cell by means of an appropriate conduit 64. 
As best seen by referring to the upper portion of FIG. 1, outlet 23 of 
second housing 12 of the fuel cell is connected with an inlet 66 provided 
on the first drive means portion of turbocompressor assembly 24 proximate 
turbine wheel 42 by means of a conduit 68. Similarly, as seen by referring 
to the central portion of FIG. 1, inlet 20 of chamber 14 of the fuel cell 
is interconnected with an outlet 70 provided on the second gas compressor 
means portion of turbocompressor 26 by means of a conduit 72. 
With the construction thus described and as illustrated in FIG. 1, when the 
fuel cell is in operation, exhaust gases flowing through outlet 23 from 
housing 12 of the fuel cell will drive the turbine wheel 42 of the first 
drive means which will, in turn, drive the compressor wheel 40 of the 
first gas compressor means. This will cause air from atmosphere to be 
drawn into inlet port 32 and forced outwardly through outlet 50 toward 
inlet port 54 of the second gas compressor means portion of 
turbocompressor 26 via conduit 52. At the same time, hydrogen gas being 
expelled from reservoir 60 will flow into the second drive means portion 
of turbocompressor unit 26 via valve 62 and conduit 58 and will drive 
turbine wheel 58. Rotation of turbine wheel 58 will cause concomitant 
rotation of a compressor wheel 76 which is mounted for rotation with the 
shaft of turbocompressor 26. This rotation of compressor wheel 76 will 
further pressurize the air flowing into inlet port 58 and will exhaust the 
pressurized air toward chamber 14 of the fuel cell via conduit 72 and 
inlet 20 of chamber 14 of the fuel cell. 
In case the pressure developed by the compressor wheel 40 of the first 
compressor means, as augmented by the pressure developed by wheel 76 of 
the second compressor, is still below the pressure desired for the 
operation of the cell, but the net energy available from the expansion of 
the exhaust gases flowing through outlet 23 and delivered to the turbine 
wheel 42 of the first turbocompressor is in fact sufficient, if fully 
utilized, to compress the air to the desired pressure, then first 
turbocompressor 24 may be subdivided in two or more subunits, wherein the 
turbine means of all subunits are connected in parallel, but the 
compressor means of the subunits are connected in series. This is more 
specifically illustrated in FIG. 2, where all reference numbers have the 
same meaning as in FIG. 1, except those pertaining to the subunits, which 
are differentiated by appending letters "a" and respectively "b" to the 
reference numbers. 
It should be noted that intercoolers (not shown) may be profitably inserted 
between turbocompressor 24a and turbocompressor 24b for the purpose of 
increasing the overall efficiency of the system, as is well known in the 
art. 
Having now described the invention in detail in accordance with the 
requirements of the patent statutes, those skilled in this art will have 
no difficulty in making changes and modifications in the individual parts 
or their relative assembly in order to meet specific requirements or 
conditions. Such changes and modifications may be made without departing 
from the scope and spirit of the invention, as set forth in the following 
claims.