U.S. patent application number 10/133167 was filed with the patent office on 2003-10-30 for cryoelectric power system.
This patent application is currently assigned to Cryoelectric, Inc.. Invention is credited to Plummer, Mitty Charles, Sterling, E. Charles, Thompson, Joseph V. JR..
Application Number | 20030200751 10/133167 |
Document ID | / |
Family ID | 29248936 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030200751 |
Kind Code |
A1 |
Thompson, Joseph V. JR. ; et
al. |
October 30, 2003 |
Cryoelectric power system
Abstract
A cryoelectric power system for use in application(s) in which a
conventional internal combustion engine is used. The power system
includes a source of cryogenic fuel, a cryoelectric boiler for
vaporizing the cryogenic fuel, a heat exchanger for warming the
vapor, and two or more turboalternators, each turboalternator
generating electricity. This power system may be utilized either as
the primary power source or as secondary pending the needs of the
application or location of the power requirement. The Seebeck and
Ettingshausen effects may be utilized in the thermoelectric boiler,
thereby producing additional electricity, and the electricity
produced by the cryoelectric boiler and the turboalternators is
output to appropriate controls and circuitry where it may be summed
and used to power an electric power system. Superconductive
material may be used in the manufacture of the turboalternators and
magnetic coil for additional system enhancement. The resulting,
highly efficient, power system is used to advantage in, for
instance, for powering a non-polluting automobile or as a prime
mover for providing a wide array of commercial electrical services
or for driving a wide variety of industrial electrical systems.
Inventors: |
Thompson, Joseph V. JR.;
(Pasadena, TX) ; Plummer, Mitty Charles; (Sanger,
TX) ; Sterling, E. Charles; (Houston, TX) |
Correspondence
Address: |
Mark R. Wisner
WISNER & ASSOCIATES
2925 Briarpark, Suite 930
Houston
TX
77042-3728
US
|
Assignee: |
Cryoelectric, Inc.
Houston
TX
|
Family ID: |
29248936 |
Appl. No.: |
10/133167 |
Filed: |
April 26, 2002 |
Current U.S.
Class: |
60/671 |
Current CPC
Class: |
H01L 35/30 20130101;
F01K 25/10 20130101 |
Class at
Publication: |
60/671 |
International
Class: |
F01K 025/00 |
Claims
What is claimed is:
1. A cryoelectric power system comprising: a source of cryogenic
fuel; a cryogenic boiler in which the cryogenic fuel is vaporized;
a heat exchanger to increase the temperature of the vaporized
cryogenic fuel; and one or more turboalternators driven by the high
pressure vapor to generate electricity, said turboalternators being
located in such proximity to said source of cryogenic fuel as to be
maintained at a temperature selected to improve the efficiency of
said turboalternators.
2. The cryoelectric power system of claim 1 wherein said
turboalternators are connected in series so that the vapor output
from one of said turboalternators is input to the next of said
turboalternators.
3. The cryoelectric power system of claim 1 additionally comprising
a manifold between said heat exchanger and said turboalternators
for distributing the vapor to said turboalternators.
4. The cryoelectric power system of claim 1 additionally comprising
an enclosure in which said cryogenic boiler is located and the
vapor exiting said turboalternators passes through said enclosure
for reducing the accumulation of frost around said cryogenic
boiler.
5. The cryoelectric power system of claim 1 wherein said boiler is
provided with means for generating electricity from the difference
in the temperature of the cryogenic fuel in said cryogenic boiler
and the temperature outside said cryogenic boiler.
6. The cryoelectric power system of claim 5 wherein said generating
means additionally comprises means for exchanging heat between the
vaporized cryogenic fuel inside the cryogenic boiler and the
ambient temperature outside said cryogenic boiler.
7. The cryoelectric power system of claim 5 wherein the electricity
generated by said generating means and the electricity produced by
said turboalternators is summed.
8. The cryoelectric power system of claim 5 wherein said generating
means comprises a layer of thermoelectric material positioned
adjacent said cryogenic boiler for producing electricity from the
temperature difference between the vaporized cryogenic fuel inside
said cryogenic boiler and the ambient temperature outside said
cryogenic boiler.
9. The cryoelectric power system of claim 8 additionally comprising
means for applying a magnetic field to said layer of thermoelectric
material.
10. The cryoelectric power system of claim 9 wherein said means for
applying a magnetic field is positioned inside said boiler.
11. The cryoelectric power system of claim 5 additionally
comprising means for increasing the electrical output of said
generating means by utilizing the Ettingshausen effect.
12. A method of generating electricity from cryogenic fuel
comprising the steps of: pumping a cryogenic fuel from a storage
tank; utilizing the Seebeck effect to generate electricity from the
difference in the temperature of the cryogenic fuel and the ambient
temperature; warming the cryogenic fuel through one or more heat
exchangers; driving a turboalternator with the warmed cryogenic
fuel to generate electricity; and summing the electricity produced
by the Seebeck effect and the electricity generated by the
turboalternators.
13. The method of claim 12 wherein the cryogenic fuel is vaporized
in a thermoelectric boiler.
14. The method of claim 12 additionally comprising utilizing the
expanded cryogenic fuel to reduce the accumulation of frost on the
thermoelectric boiler.
15. The method of claim 12 additionally comprising venting the
expanded vapor to the atmosphere.
16. The method of claim 12 additionally comprising applying a
magnetic field to the thermoelectric boiler.
17. A method of generating electricity from a cryogenic liquid
comprising the steps of: heating the cryogenic liquid to change the
cryogenic liquid from a liquid to a vapor; increasing the volume of
the vapor in one or more heat exchangers to an operating range of
from about 200 to about 500 psig; and driving at least one or more
turboalternators with the expanded vapor to generate
electricity.
18. The method of claim 17 additionally comprising utilizing the
Seebeck effect to produce electricity from a difference in the
temperature of the cryogenic liquid and ambient temperature.
19. The method of claim 18 additionally comprising summing the
electricity generated by the turboalternators and the electricity
produced by utilizing the Seebeck effect.
Description
BACKGROUND OF THE INVENTION
[0001] This invention generally relates to the use of a cryogen as
a fuel for a prime mover. In more detail, the present invention
relates to improvements on the device disclosed in U.S. Pat. No.
4,311,917, which prior patent is incorporated into this disclosure
in its entirety as if fully set forth herein.
[0002] The finite quantity of hydrocarbon fuels that are available,
the cost of such fuels, and the pollutants produced by combustion
of such fuels together indicate that it is necessary to develop
alternatives to the power sources in current widespread use. One
alternative that has been investigated is the use of cryogenic heat
engines, a concept in which a cryogenic substance is used as a heat
sink for a heat engine. Examples of such engines include those that
utilize liquid nitrogen to propel the vehicles that were designed
and built at the University of North Texas and the University of
Washington. In the engines of both of these vehicles, liquid
nitrogen is vaporized and then expanded through an expansion engine
to produce work.
[0003] The above-incorporated U.S. Pat. No. 4,311,917 discloses a
motor that operates in much the same fashion, but which utilizes
the work output from an expansion engine to drive a generator that
either powers an electric motor or charges a battery pack. That
patent discloses the advantage of cooling the generator and the
motor with the cryogenic gas so as to improve the performance
characteristics of these components. There is, however, a need for
improvements in the efficiency of the power system disclosed in
that patent, and it is a primary object of the present invention to
provide such improvements in the apparatus disclosed in that prior
U.S. Pat. No. 4,311,917.
[0004] Another object of the present invention is to provide an
alternative to the internal combustion engine that provides
sufficient power output to be useful as a prime mover for providing
power in many industrial and consumer applications. The power from
the prime mover is utilized in industrial applications, in remote
locations, back-up power systems for hospitals and other
facilities, as a primary power system in locations in which
emissions must be controlled, in the automotive industry and for
other vehicles, for instance, as a non-polluting automobile or
other motorized vehicle such as industrial trucks and refrigeration
units, to run the lights and refrigeration systems of vehicles that
would normally draw against the vehicle's electrical system, as a
secondary power source in an electrical or hybrid vehicle, and as a
charging system for electrical or hybrid vehicles so that the
batteries of the vehicle are charged while the vehicle is in use or
parked.
[0005] Another object of the present invention is to provide a
cryoelectric power system that utilizes a turbo-alternator
producing AC or DC voltage in place of known alternator circuits,
thereby reducing the size of the system while retaining, and even
increasing, the power output of the power system.
[0006] Another object of the present invention is to provide a
cryoelectric power system utilizing superconductive materials for
enhancing electrical efficiency and increasing electrical output
over prior cryoelectric power systems.
[0007] Another object of the present invention is to provide a
cryoelectric power system that operates virtually frost-free by
utilizing a flow of warmed cryogen to flow across the heat
exchangers and a cryogenic boiler to enhance the efficiency of the
expansion of the cryogen and reduce, or even eliminate, frost
accumulation.
[0008] Another object of the present invention is to provide a
cryoelectric power system that utilizes one or more heat exchangers
for enhancing the efficiency of the of the system by warming the
cryogen to a high pressure vapor, reducing the size of the re-heat
stages (as compared to prior known systems) and clearing (or
keeping clear) one or more sections of the cryoelectric power
system of frost.
[0009] Another object of the present invention is to provide a
cryoelectric power system with enhanced efficiency in the
generation of DC power by utilizing one or more thermodynamic
phenomena, such as the Seebeck and/or Ettingshausen effects.
[0010] Yet another object of the present invention is to provide a
cryoelectric power system that produces electricity at higher
efficiency than prior cryoelectric power systems by further
enhancing power output by utilizing the Ettingshausen effect.
[0011] Another object of the present invention is to provide a
cryoelectric power system that produces electricity at a higher
efficiency than prior power systems by using regenerative processes
to enhance the expansion of a cryogenic fuel, such as liquid
nitrogen, to high pressure vapor for the purpose of driving
(fueling) one or more turboalternators to generate electricity.
[0012] Other objects, and the advantages of the invention, will be
made clear to those skilled in the art by the following description
of a preferred embodiment of an apparatus constructed in accordance
with the teachings of the present invention and methods of
utilizing those teachings.
SUMMARY OF THE INVENTION
[0013] These objects, and the advantages of the cryoelectric power
system of the present invention, are met by providing a source of
cryogenic fuel, a cryogenic boiler for vaporizing the cryogenic
fuel, a heat exchanger for increasing the temperature of the
vaporized fuel to expand and increase the volume of the vapor, and
at least two turboalternators driven by the vapor output from the
boiler to generate electricity, the turboalternators being located
in such proximity to the source of cryogenic fuel as to be
maintained at a temperature selected to improve the efficiency of
the turboalternators. The turboalternators may be arranged in
series so that they are each driven by the exhaust from the
previous turboalternator to maintain maximum use and efficiency of
the expanding cryogenic fuel. The windings of the turboalternators
are preferably comprised of super-conducting materials and are
located in close enough proximity to the cryogenic fuel source as
to be maintained at a temperature selected to improve the
performance of the alternator, and therefore, the efficiency and
output of the cryoelectric power system. Optionally, the
turboalternators are arranged in parallel from a manifold located
between the heat exchanger and the turboalternators such that the
expanding cryogenic fuel is heated and expanded just once.
[0014] In the case of a cryoelectric power system that includes
parallel turboalternators, the use of two or more turboalternators
allows for a corresponding number of individual power circuits via
common electrical circuit connections or they can be phased so as
to produce three-phase power for larger and more complex AC
electrical power needs. Further, the individual power circuits can
be synchronized together so as to produce a single, high wattage
output that can be utilized to feed into an electrical utility
network to provide power to the power grid or for other industrial
applications.
[0015] The efficiency of the cryoelectric power system of the
present invention is further enhanced by providing means for
generating electricity from the increase in the temperature of the
cryogenic fuel entering the boiler and the vaporized cryogenic fuel
exhausted from the turbines. The electricity produced by both the
generating means and the turboalternators is summed and output for
the particular desired application, which may be as a prime mover
for a wide variety of electrically driven systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic diagram of a preferred embodiment of a
cryoelectric power system constructed in accordance with the
teachings of the present invention.
[0017] FIG. 2 is a schematic diagram of a second preferred
embodiment of a cryoelectric power system constructed in accordance
with the teachings of the present invention.
[0018] FIG. 3 is a longitudinal sectional view, shown in schematic
illustration, of a thermoelectric boiler of a type suitable for use
in connection with the cryoelectric power systems of either FIGS. 1
or 2.
[0019] FIG. 4 is a cross-sectional view of the thermoelectric
boiler of FIG. 3 taken along the lines 4-4 in FIG. 3.
[0020] FIG. 5 is a longitudinal sectional view, shown in schematic
illustration, of a cryoelectric boiler of a type suitable for use
in connection with the cryoelectric power systems of either FIGS. 1
or 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] Referring first to FIG. 1 of the accompanying drawings, a
schematic drawing of a preferred embodiment of a cryoelectric power
system constructed in accordance with the teachings of the present
invention is shown. In the particular embodiment shown, the
cryoelectric power system includes a source of cryogenic fuel in
the form of a cryogenic tank 10 and cryogenic pump 12 for
pressurizing the liquid cryogenic fuel from the tank 10. The
cryogenic fuel is preferably liquid nitrogen (LN.sub.2), but those
skilled in the art will recognize from this disclosure that other
cryogens, such as liquid air, are available that provide the
extreme cold that allows their use as a cryogenic fuel that is
suitable for use in connection with the present invention. Liquid
Nitrogen (LN2) has been selected as the primary fuel due to its
favorable expansion properties, because it is 100% non-polluting
and is 100% non-flammable, and because it is extracted from the
breathable air and is returned to the atmosphere as the exhaust
(warmed nitrogen vapor) of the present invention. Other cryogens,
including liquified air; helium and hydrogen, may optionally be
used as the primary fuel. The cost, availability and efficiencies
of the cryogenic fuel will vary on the cryogen or combinations of
cryogens selected as the fuel. An external storage tank 14 is
shown, with a pump 24 for pressurizing the cryogenic fuel from
storage tank 14 to cryogenic tank 10, that may be an on-site tank,
a railroad car, truck trailer, or other source of cryogenic fuel as
known in the art.
[0022] The cryogenic fuel exits cryogenic tank 10 through a pump 24
and is vaporized in a cryoelectric boiler 16, which takes the form
of a thermoelectric boiler (TEB) in the particular embodiment
shown. Appropriate flow and pressure controls 12, as well as flow,
pressure, and temperature sensors (not shown), are located at
appropriate locations as needed to balance the flow of the cryogen
and the expanded vapor as known in the art.
[0023] The primary warming of the vaporized cryogen occurs in the
high pressure heat exchanger 20 that is preferably located in a dry
gas enclosure, or frost-free chamber, 18 which, like the
alternators 26 and boiler 16, is described in more detail below.
The pressurized cryogenic vapor exits the thermoelectric boiler 16
to a high pressure heat exchanger 20 and then passes through one or
more heat exchanger/turboalternator sets, each operating at
progressively lower pressures, all of which may be contained within
an enclosure 22 through which the warmed, expanded vapor (exhaust)
is circulated internally before being exhausted to line 38 and
eventually to the atmosphere. In the preferred embodiment shown in
FIG. 1, a series of three heat exchanger/turbines is provided, the
vapor exiting the high pressure heat exchanger 20 to a high
pressure turboalternator 26 through line 28, to an intermediate
heat exchanger 30, intermediate pressure turboalternator 32, low
pressure heat exchanger 34, low pressure turboalternator 36, and
out into the enclosure 22 from the final turboalternator 36. Vapor
exiting the enclosure 22 is routed through line 38 to the dry gas
enclosure 18 for reducing frost formation around thermoelectric
boiler 16 and high pressure heat exchanger 20, and then vented to
the atmosphere. A baffle 72 may be provided in the enclosure 18
(see FIGS. 3 and 5) to insure even distribution of the warm gas
within enclosure 18.
[0024] In the embodiment shown in FIG. 2, in which like structure
is denominated with the same reference numerals as utilized in FIG.
1 but preceded by a "2," the high pressure vapor exiting the
thermoelectric boiler 216 through line 228 passes through the high
pressure heat exchanger 220. The vapor exits heat exchanger 220 to
a manifold 250 that distributes the high pressure vapor stream to
one or more turboalternators (AC or DC), three being shown at
reference numerals 230A, 230B, and 230C in FIG. 2, and out of the
turboalternators 230 to be rewarmed and circulated over the high
pressure heat exchanger before exhausting to the atmosphere.
[0025] The electrical output from each of the turboalternators 26,
32, and 36, or 230A, 230B, and 230C, is routed through a lead 40
(or 240) to the power terminal block 48 (or 248), preferably
located proximate control panel 44/244. Similarly, the electrical
output from thermoelectric boiler 16/216 is routed through lead 45
to the power terminal block 42, where it is summed with the output
of turboalternators 26, 32, and 36 or 230A, 230B, and 230C. The
output from TEB 16/216 is DC power whereas the output from
turboalternators 26, 32, and 36, or 230A, 230B, and 230C is either
AC or DC, hence separate terminal blocks 42 and 48 are shown, but
those skilled in the art who have the benefit of this disclosure
will recognize that separate terminal blocks are not necessary
depending upon the particular electrical power output that is
desired. Control panel 44/244 is provided with appropriate
controls, indicated generally at reference numeral 46/246, for
system main on/off, control of voltage, amperage, frequency, rpm,
pressure and temperature monitoring and control, and monitoring and
control of output power (for instance, in watts), all accomplished
in accordance with principles known in the art.
[0026] In the preferred embodiments shown in FIGS. 1 and 2, the
cryogenic boiler 16 is provided with means for generating
electricity from the temperature difference of the cryogenic fuel
entering the cryogenic boiler and the vaporized cryogenic fuel
exiting the turbines and reheated to near atmospheric
termperatures. In the embodiments shown, the generating means takes
the form of a layer of thermoelectric (TE) material 74 positioned
adjacent the cryoelectric boiler 16 (hence the references herein to
a thermoelectric boiler (TEB)). The TEB 16 of the present invention
is shown schematically and in more detail in FIG. 3 and generates
DC voltage/current. The use of such a boiler in connection with the
cryoelectric power system of the present invention increases the
power production of the cryoelectric power system by as much as
4-6%, depending upon such factors as the particular cryogenic fuel
being utilized, the output of the turboaltemators, being either or
both AC or DC power, and the presence of a magnetic field.
[0027] As shown in FIGS. 3 and 4, TEB 16 is comprised of a shell
60, preferably made of stainless steel or aluminum, having a magnet
coil 62 mounted in a sleeve 64 that is commonly retained therein. A
flanged coupling 66 to lid 68 is provided so that the sleeve 64 in
which the magnet 62 is mounted can be removed from the shell 60 for
maintenance. The shell 60 is shown enclosed by the dry gas
enclosure 18, the dry gas that is routed through enclosure 18
being, of course, the vapor exiting the last (low pressure) turbine
36 as shown in FIG. 1, for preventing frost formation therein.
[0028] The shell 60 of TEB 16 is surrounded by layers of very thin
electrical insulation 70 sandwiching a TE material 74 comprised of,
for instance, Bi.sub.2Te.sub.3-Bi.sub.2Se.sub.3Te.sub.3 having
electrically conductive straps 76 alternately connecting the TE
material, for generating electricity from the temperature
difference between the cryogen in shell 60 and the ambient
temperature in accordance with the Seebeck effect. The shell 60 is
preferably oriented vertically so that the cryogen entering shell
60 receives heat and causes the liquid cryogen to vaporize and rise
through the shell 60 to exit at the top of the shell.
[0029] The Seebeck effect occurs when the
Bi.sub.2Te.sub.3-Bi.sub.2Se.sub.- 3Te.sub.3 comprising TE material
74 is exposed to the difference in temperature between the inside
of shell 60 and the ambient air outside of shell 60. Thus, TEB 16
produces electricity that is delivered to the output leads 45
through the conductive straps 76. The figure of merit of the TE
material is increased by a factor of approximately two by the
presence of a magnetic field such as is produced by the magnet 62
located in shell 60, and in the embodiment shown, means is provided
for applying a magnetic field to the TE material 74 in the form of
electromagnetic coils, comprised of copper or superconductive
wiring, for additional power output from TEB 16 by utilizing the
Ettingshausen effect. The Ettingshausen effect requires a
concurrent magnetic field of approximately 0.5 Tesla parallel to
the heat flow of the TE material 74 and a difference in the
temperature from the atmosphere outside the TEB to the cryogenic
fuel passing through TEB 16. Power is provided to the
electromagnetic coil 62 through leads A, B.
[0030] Although each of the embodiments of the cryoelectric power
system of the present invention shown in FIGS. 1 and 2 utilize the
Seebeck effect to generate electricity with a TEB 16, it will be
recognized by those skilled in the art that the cryoelectric system
need not utilize the Seebeck effect to provide an advantage in
efficiency over prior known cryoelectric systems. The vaporization
of the cryogen in the boiler 16, followed by the warming of the
vapor in heat exchanger 20, provides sufficient volume to drive the
turboalternators in a manner that is highly efficient. It has been
found that an operating range of from about 200 psig to about 500
psig (measured at the output from heat exchanger 20) provides this
advantage, and this operating range can be achieved by commercial
cryogenic pumps. Sufficient warming can be achieved by the exchange
of heat with the atmosphere around boiler 16, and referring now to
the embodiment of the boiler 16 shown in FIG. 5, it can be seen
that heat fins 80 are provided to facilitate this exchange of heat
with the atmosphere. No TE material is shown in FIG. 5 because the
function of the boiler shown in that figure is to facilitate
expansion of the vaporized cryogenic fuel, but those skilled in the
art will recognize that a thermoelectric boiler such as is shown in
FIGS. 1-4 can also be provided with fins 80 for this same
purpose.
[0031] The turboalternators 26, 32, and 36 (230A, 230B, and 230C in
FIG. 2) will now be described in detail. Conventional hot
gas-fueled turbine generator sets consist of a high-speed turbine
(e.g., 25-50 k rpm) coupled to a low speed electrical generator
(e.g., 1.5 k to 3 k rpm) through a reduction gearbox, whereby the
gear reduction process produces extra losses. However, the voltage
output of such a generator is proportional to its rotational speed.
Consequently, if an alternator is run at turbine speed and is small
enough to be integrated onto the same shaft as the turbine, the
result is a compact, high-speed generator, or turboalternator. Each
of the turbines 26, 32, and 36 (and 230) is constructed in this
fashion. Such turboalternators are available commercially from
several sources, including Bowman Power Limited (Southampton,
England), Stewart & Stevenson (Houston, Tex.), Pratt &
Whitney (East Hartford, Conn.), Baldor Electric Company (Fort
Smith, Ark), Barber-Nichols, Inc. (Arvada, Calif.), Airworld (UK),
Ltd. (Winslow Bucks, UK), and Hess Microgen, LLC/Integrated Power
Systems International (Rochester, N.Y.), in varying operating
ranges and outputs. In the case of the present invention, the
operating ranges and outputs of the turboalternators are sized to
the corresponding heat exchangers 20, 30, and 34 as the cryogenic
fuel is warmed by the heat exchangers, thereby maximizing their
respective electrical outputs to the power terminal block 42. Those
skilled in the art who have the benefit of this disclosure will
recognize that the number of such turboalternators utilized in
connection with the cryoelectric power system of the present
invention, and their sizing, will involve optimization in
accordance with principles known in the art.
[0032] As shown in FIGS. 1 and 2, each of the turboalternators 26,
32, and 36, and 230A, 230B, and 230C, is positioned relative to
tank 10 so that the alternator, directly attached to the turbine
shaft, is closely situated to tank 10 so that the cold temperature
of the cryogenic fuel increases the operating efficiency of the
alternator, especially if superconductive materials are utilized in
the windings of the alternator. Specifically, the turboalternators
26, 32, and 36, and 230A, 230B, and 230C, are mounted in
complementary-shaped mounts 52/252 that are received in the wall of
tank 10.
[0033] The foregoing description of the preferred embodiment of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed, and many modifications and
variations are possible in light of the above teaching without
deviating from the spirit and the scope of the invention. The
embodiment described is selected to best explain the principles of
the invention and its practical application to thereby enable
others skilled in the art to best utilize the invention in various
embodiments and with various modifications as suited to the
particular purpose contemplated. For instance, it will be
recognized that the electrical output of the turboalternators may
need to be synchronized with the output from the thermoelectric
boiler and/or super-conducting alternator. Alternatively, each of
the electrical power outputs is utilized independently of the other
such that there is no need for synchronization. All such changes
are intended to fall within the scope of the invention as defined
by the claims appended hereto.
* * * * *