Note: Descriptions are shown in the official language in which they were submitted.
~734~
TITLE OF T~IE INVENTION
GEOTHERMAL ENERGY UTILIZATION SYSTEM
BACKG~OUND OF THE INVENTION
This invention relates to a geo-thermal energy
utilization system in which a geo-thermal fluid is
introduced to a plurality of thermal energy utilization
facilities in a sequence depending upon the thermal
energy possessed by the fluid, and in which each
facility is operated by exploiting the -thermal energy
delivered thereto to make possible the overall
effec-tive utilization of the geo-thermal energy.
Geothermal energy is a naturally occurring form of
energy which, as a resource, is available in fairly
great abundance in comparison with solar heat and wind
energy. Since it is also an inexhaustable and
domes-tically available energy source, there are great
expectations for its effective utilization. At the
present time, geothermal energy is utilized almost
entirely for power generation. Several geothermal
power generation plants have been put into operation so
far and for the most part rely upon so-called dry steam
as the geothermal fluid. Dry steam is physically
favorable in -that it has almost no moisture content at
temperatures above 150C. Geothermal energy also finds
some limited application in agriculture, heating and
cooling and in the melting of snow, depending upon the
tempera-ture of the geothermal fluid and its chemical
properties, such as acidity. Cases in which the
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thermal energy oE a geothermal Eluid can be used for
power generation or in applications other than power
generation are categorized according to the temperature
of the geothermal fluid reservoir.
Geothermal fluids do not always accumulate in the
earth in the form of layers as does petroleum but of-ten
collect in highly porous rock or in multiple rock
fractures. Geothermal energy reserves are expressed by
the tempera-ture of the fluid in the particular
reservoir and -the amount of thermal energy possessed by
the fluid, and the method in which the fluid is used is
determined by whether it exists in the form of hot
water or steam. It is believed that the amount of -the
resource available in the form of such physically
favorable steam as dry steam occupies about 10~ of the
total geotherl~al resource. Further, well production,
namely the amount of geothermal fluid which flows out
of a geothermal production well per hour, differs
greatly from well to well and the amount of thermal
energy possessed by a unit weight of the geothermal
fluid varies depending upon the weight of steam
contained in the unit weight of fluid.
When attempting to utilize a geothermal fluid,
thereEore, various restric-tions come to bear depending
upon the method of u-tilization and the properties, both
chemical and physical, of the geothermal fluid
obtained. Matching the type of geothermal fluid with
the particular manner of utilization is a difficult
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task. For example, even if a geothermal fluid reservoir is
discovered with the intent of utilizing its energy for power
generation, the reservoir may never be used if the particular
geothermal fluid is found to be unsuitable for power generation
purposes. Accordingly, there are many cases where only those
production wells that produce a gecthermal fluid suitable for a
specific utilization are kept for use, with all other production
wells being destroyed.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the
foregoing circumstances.
According to the present invention, there is provided a
system for utilizing in equipment stages the thermal energy of a
geothermal fluid produced by a geothermal production well. An
equipment stage is selected in accordance with the amount of heat
energy possessed by the geothermal fluid. The system may include
direct power generation equipment for generating electric power
directly by using the ~ ~
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geothermal fluid, indirect power generation equipment
for genera-ting electric power through heat exchange
with the geothermal fluid using carbon dioxide as a
heat -transfer medium, refrigera-tion equipment Eor
cooling water by an absorption refrigeration method,
and hot water utiliza-tion equipment for hot spring and
other purposes. The arrangement is such that high-
temperature geothermal fluid is supplied to the direct
power generation equipment -to be used for the
generation of electric power, intermediate-temperature
geothermal fluid is supplied to the indirect power
generation eguipment to be used for the generation of
electric power, and ho-t water recovered at a low
temperature following its use in cooling and air
conditioning performed by the refrigeration equipment
is utilized at the hot water utilization equipment for
hot spring and other purposes.
Thus, according to the present invention r a
geothermal fluid extracted from a production well is
utilized several times for such purposes as power
generation and cooling until it is finally used as hot
water. This makes it possible to effectively utilize
the thermal energy of the fluid without wasteful
radiation of the energy.
O-ther fea-tures and advan-tages of the present
invention will be apparent from the :Eollowing
description taken in conjunction with the accompanying
drawings, in which like reference characters designate
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the same or simi]ar par-ts -throughout the figures
thereoE.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is block diagram useful in describing an
embodiment of a geothermal energy utilization system
according to the presen-t invention;
Fig. 2 is a schematic view illustrating the
arrangement of hot water energy combining units and
direct power genera-tion equipment according to the
embodiment of the present inven-tion;
Fig. 3 is a schematic view for describing an
ejector used in the hot water combining units of Fig.
2;
Fig. 4 is a block diagram showing an embodiment of
indirect power generation equipment according to the
present invention;
Fig. 5 is a thermodynamic diagram useful in
describing the cycle of the power generation equipment
shown in Fig. 4;
Fig. 6 is a diagrammatic view showing the
arrangement of refrigeration equipment according to the
embodiment of the present invention;
Fig. 7 is a diagrammatic view showing the
arrangement of a water-wheel generator annexed to the
power generation equipment of a geothermal energy
utilization system according to the embodiment of the
present invention;
Fig. 8 is a diagrammatic view for describing an
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embodiment oE a vacuum conveyance system applied to the
present invention; and
Figs. 9(A), ~B), (C) are views for describing an
embodiment of a hot wa-ter conveyance path applied to
the present invention.
DESCRIPTION OE THE PREFERRED EMBODIMEN_
An embodimen-t of -the present invention will now be
described with reference to the accompanying drawings.
Fig. 1 is a block diagram illustrating an
embodiment of a geo-thermal energy utilization system
according to the present invention. The system
includes units 11, 1~ each for combining hot water
energy from several production wells, direc-t power
generating equipment 12, indirect power generating
equipment 13, refrigeration equipment 14, and hot water
utilization equipment 15. The combining units 11, 16
combine and extract hot water energy from a plurality
of production wells so as to make effective overall use
of the energy. The direct power generating equipment
12 uses high-temperature geothermal fluid to directly
drive a turbine for power generat1on. Examples of this
equipment used conventionally are a steam generator,
flash generator and total flow generator. The most
suitable power generator is selected depending upon the
contents of the geothermal fluid extracted from the hot
water energy combining unit. Alternatively, a
plurality oE thesè power generators may by used in a
parallel configuration. The only power generation
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whlch takes place in the prior art uses steam having a
temperature above 150C, as men-tioned above. ~owever,
by employing an atmospheric pressure turbine which uses
saturated steam at a temperature of 100C as the input
energy, the direct power generating equipment 12 in
accordance with the present invention generates power
by utilizing the heat energy of steam the temperature
whereof drops to that usable by the indirect power
generating equipment 13, which is the next stage. The
indirect power generating equipment 13 employs carbon
dioxide as a medium and drives a turbine by raising the
temperature and pressure of the carbon dioxide to 65C
and 130 kg/cm , respectively, through indirect contact
between this medium and the geothermal fluid having an
intermediate temperature of 50 - 80C. Like the
indirect power generating equipment 13, the
refrigeration equipment 14 uses the intermediate
temperature geothermal fluid to effect cooling and
reErigeration by an absorption refrigeration method.
The hot water utilization equipment 15, an example of
which is a hot spring or heating equipment, utilizes
hot water of comparatively low temperature which
- results from earlier use in the indirect power
genera-ting equipment 13 and refrigeration equipment 14.
The geothermal fluid is broadly classified according to
the amount of its heat energy. The intermediate- and
low-temperature geothermal fluid may be introduced into
the system at intermediate points through the combining
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unit 16, as illustrated in Fig. 1.
A specific embodiment of each item of equipment
shown in Fig. 1 as well as the geothermal fluid
conveyance system will now be described.
Fig. 2 is a schematic view illustrating the
arrangement of a hot water energy combining unit and
the direct power generation equipment according to the
embodiment of the present invention. Fig. 3 is a
schematic view for describing an ejector used in the
hot water combining unit of Fig. 2. As shown in Fig.
2, the arrangemen-t includes geothermal production wells
21, 22, 23, a silencer 24, ejectors 25, 26, a steam
separator 27, a steam conveyance pipe 28, a turbine 29,
a power generator 30, a pump 31, an injection condenser
32, a hot water tank 33 and a nozzle 34. The
production wells 21, 22, 23 are for generating hot
water at high, intermediate and low pressures~
respectively. In order that the low-pressure hot water
may be successively drawn out by ejection of the
high-pressure hot water, the high-pressure production
well 21 is connected to the intermediate-pressure
production well 22 through the ejector 25, and the
intermediate-pressure production well 22 is in turn
connected to the low-pressure production well 23 via
the ejector 25. The hot water combined by the ejectors
25, 26 is delivered to the steam separator 27. Here
steam is separated from the hot water and is then fed
to the turbine 29 through the steam conveyance pipe 28.
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The turbine 29 is driven by -the steam delivered
thereto, after which the steam i5 condensed by the
injection condenser 32. The resul-ting condensate
collects in the hot water tank 33 whence it is
introduced to the geothermal energy utilization
equipment, which is the next stage. Any uncondensed
gas is released to the atmosphere.
As shown in Fig. 3, the ejector 25, which combines
the high-pressure hot water from the production well 21
and the intermediate-pressure hot water from the
production well 22, is adapted to form the
high-pressure hot water into a jet by the nozzle 34 and
eject the high-pressure hot water toward the
low-pressure production well 23 while the intermediate-
pressure hot water is drawn into the flow at theinterfacial boundary thereof. A similar construction
is adopted for the ejector 2~, which combines the
ejected hot water from the ejec-tor 25 and the
low-pressure hot water from the production well 23.
According to the method adopted in the prior art,
the steam from a plurality of production wells is
combined with the steam from the production well having
the low well head pressure so that the energy from the
production well having the high steam pressure is used
after it is effectively reduced. The energy is thus
used in a wasteful manner. One reason for adopting
this method is that in an arrangement where a plurality
of production wells are connected in series, the
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low-pressure steam is suppressed by the high-pressure
steam, so that the only solution was -to combine the
high-pressure steam with the low. A consequence of
this conventional approach is a relatively lower input
pressure applied to the turbine, as a result of which
the latter operates inefficien-tly. By contrast, in
accordance with the present invention, the ejectors 25,
26 are employed to connect a plurality of production
wells having different geothermal temperatures and the
hot water from -the low-pressure production well is
successively drawn up by the ejection of the hot water
from the high-pressure production well and combined
therewith. This enables a large quantity of steam to
be supplied to the turbine at the higher pressure
rather than the lower so that the turbine can be
operated more efficiently.
Fig. 4 illustrates an embodiment of the indirect
power generation equipment according to the present
invention. The equipment includes a hot water supply
unit 41, a preheater/evaporator 42, a turbine 43, a
power generator 44, a compression pump 45, a condenser
46, and a medium pump 47. Carbon dioxide, which is
used as the heat transfer medium, is fed into the
preheater/evaporator 42 by the medium pump 47. The
preheater/evaporator 42 is also supplied by the hot
water supply unit 41 with geothermal fluid at a low
temperature of 65 - 80C. The supply unit 41 receives
the hot water from a geothermal production well or from
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the direct power generation e~uipment, which is the
preceding stage. A heat exchange between the carbon
dioxide heat transfer medium and the low-temperature
(65 - 80C) geothermal :Eluid takes place inside the
preheater/evaporator 42. The carbon dioxide heat
transfer medium has a critical temperature of 35C,
70 kg/cm and remains stable without undergoing thermal
decomposition even if it is raised to a temperature of
65C and a pressure of 130 kg/cm2. By making effective
use of the nature of stable carbon dioxide having the
critical temperature of 35C, 70 kg/cm2, the carbon
dioxide heat transfer medium is raised to a temperature
and pressure of 65C and 130 kg/cm2, respectively, by
the indirect contact with the geothermal fluid inside
the preheater/evaporator 42 before being supplied to
the turbine 43. As a result, the turbine 43 is driven
into operation so that the power generator 44 generates
electric power. Low-temperature geothermal fluid
discharged from the preheater/evaporator 42 is
introduced to a hot spring or other hot water
utilization system. Following its use in operating the
turbine 43, the carbon dioxide is cooled and compressed
by the compression pump 45 to be converted into a
liquid before being re-turned to the condenser 46. The
carbon dioxide heat medium is then resupplied to the
preheaterJevaporator 42 from the condenser 46 by the
medium pump 47. Circulation of the carbon dioxide is
thus accomplished.
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Fig. 5 is a thermodynamic diagram useful in
describing the cycle of the power generation equipment
shown in Fig. 4. Temperature T is plotted along the
vertical axis, and enthalpy h (kcal/kg) is plotted
along the horizontal axis. The curves plotted include
a geothermal fluid temperature change curve 51 and a
C2 saturated steam curve 53 for a case where carbon
dioxide is used as the heat transfer medium, and a
geothermal fluid temperature change curve 52 and a fron
satura-ted steam curve 5~ for a case where fron is used
as the heat transfer medium. Where fron is used, the
medium is elevated in pressure from point a to point b
by a pump and is thereafter heated by a geothermal
fluid whose temperature changes from ~ ' to ~ ,
thereby increasing enthalpy to effect preheating and
evaporation from b to c' to c". In the turbine,
expansion occurs from c" to d so that work is
performed, i.e., so that the turbine is driven.
Cooling and condensation occur from d to e to a, ~ ~-
whereby the initial state is restored. Where carbon
dioxide is used as the heat transfer medium, the medium
is elevated in pressure from point a to point b by a
pump and is thereafter heated by a geothermal fluid
whose temperature changes from ~ to ~ , -thereby
increasing enthalpy to effect preheating and
evaporation from b to c. Accordingly, in a case where
the outlet temperature of the geothermal fluid is the
same, i.e., t3, the inlet temperature t2 of the
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geothermal fluid where carbon dioxide is used as the
medium is much lower than the inlet temperature tl oE
the geothermal medium where ~ron is used as the medium.
Accordingly, excellent results are obtained in terms of
the usable temperature range of t2 t3, as opposed to
tl - t3, and in terms of the ratio of maximum output to
the amount of heat emitted by the geothermal fluid (the
ratio of c" - d to tl - t3 and of c - d to t2 ~ t3).
In cases where the temperature of the geothermal
fluid is not very high or where reliability becomes a
problem because the geothermal fluid is strongly acidic
and the material constituting the casing or blades of
the steam turbine is not sufficiently corrosion
resistant, binary cycle power generation using a
working medium is adopted. In binary cycle power
: generation, the heat energy of the geothermal fluid is
transmitted to the working medium to effect its
evaporation, the turbine is driven by the steam from
the working medium, and electric power is produced by
the generator connected to the turbine. With
conventional power generation, the geothermal steam
temperature inevitably is greater than 150C, with
power being generated at low efficiency if the
geothermal steam temperature is ~n the order of 80C.
For this reason, geothermal steam at this temperature
has not been considered to be usable for power
generation. According to the present invention,
however, carbon dioxide is used as the heat medium and
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~273496
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is raised in temperature and pressure to 65C and 130
kg/cm2, respectively, to drive the turbine. This makes
it possible to fully utilize even a geothermal fluid
whose temperature is 65 to 80C. Further, iE the
geothermal fluid used has a temperature higher than the
critical temperature (35C) of the carbon dioxide heat
medium, even a geothermal fluid whose temperature is
50C can be employed. Specifically, since this medium
can be elevated in temperature and pressure beyond its
cri-tical state, the turbine can be driven even by using
geothermal fluid of considerably reduced temperature
that results from previous use in power generation by
the direct power generation equipment.
Fig. 6 is a diagrammatic view showing the
arrangement of refrigeration equipment according to the
embodiment of the present invention. The equipment
includes an evaporation tank 61, a condensation tank
62, refrigerants 63, 64, a pump 65, and a pan 66. The
refrigerants 63, 64 consist oF a mixture of a lithium
bromide hydrate (Li-Br 2H2O) and an alcohol solution
such as ethanol or methanol. The evaporation tank 61
contains the refrigerant 63 under a vacuum oE about 75
mmHg, and the condensation -tank 62 contains the
refrigerant 64 under a vacuum of about 7 mmHg. ~ pipe
for refluxing hot water in the form of steam from a
steam well passes through the refrigerant 63 contained
in the evaporation tank 61 in order to hea-t the
refrigerant 63 under the vacuum oE 75 mmHg. Since it
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~Z73496
contains the alcohol solution, the refrigerant 63 has a
low boiling point and is boiled into a vapor by steam
or hot water having a temperature even an low as 65C.
Arranged in -the evaporation tank 61 above the surface
of the refrigerant 63 is a pipe for refluxing water
Erom an out-of-door cooler. The pan 66 is disposed
undernea-th this pipe. Here water vapor obtained from
the boiling and evaporation oE the refrigerant 63 is
collected in the form of moist steam which is then
refluxed from the pan 66 to the condensation tank 62,
in the course of which cold water is produced by
adiabatic expansion. The cold water is introduced in-to
the upper part of the condensation tank 62 to cool an
air conditioner water pipe before merging with the
refrigerant 64. Water refluxed through the air
conditioner water pipe is thus cooled from 12C to 7C.
In the above process, the refrigerant 63 becomes more
concentrated due to boiling and evaporation, whereas
the refrigerant 64 becomes less concentrated owing to
the inflow of the cold water. This makes it necessary
to introduce some of the refrigerant 63 into the
refrigerant 64 of condensation tank 62 and to reElux
some of the refrigerant 64 to the refrigerant 63 in
evaporation tank 61 by using the pump 65 so that the
concentration of the refrigerants will be maintained at
a predetermined value at all times.
Thus, in -the refrigeration equipment as described
above, lithium bromide hydrate whose boiling point is
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lowered by the addition of an alcohol solution is used
as a refrigerant, the water content thereof is
evaporated and condensed in the evaporation tank 61,
cold water is produced from -the condensate by adiabatic
expansion, and the cold water is used to cool the water
refluxed through the air conditioner water pipe. This
makes it possible to effectively exploit even a
low-temperature heat source that was difficult to
utilize in the prior art. Further, in the arrangement
of Fig. 6, the cooling water regulated to a temperature
of 32C by the out-of-door cooler is for auxiliary
cooling of the steam in the evaporation tank 61 and the
refrigerant 64 in the condensation tank 62 and thus
improves the condition in these tanks. More
specifically, cooling and condensing some of the steam
in the evaporation tank 61 by the water from the cooler
to produce wet stearn enhances the adiabatic expansion
effect. In the condensation tank 62, the water from
the cooler lowers the temperature of the refrigerant 64
so that the discharge temperature of the water refluxed
through the air conditioner water pipe will not be
raised owing to the refrigerant refluxed from the
evaporation tank~61 at a high temperature.
Geothermal energy may be tapped in various forms
such as steam, hot water and fluids which are a mix-ture
thereof, and the temperature of these geotherrnal fluids
varies over a wide range of from high to low
-temperatures. Nevertheless, the geothermal energy
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sources utilized in the prior ar-t generally give an
inlet -temperature of no less -than 80C, with fluids
exhibiting a lower tempera-ture having been considered
unusable. Even with refrigeration equipment utilizing
this conventional geothermal fluid, fresh water at a
temperature of 90C is converted into hot wa-ter having
a temperature of 95C and this is used as a heat source
for producing cold water exhibiting a tempera-ture of
from 5 to 10C. Accordingly, with this refrigeration
equipment, even when low-temperature hot water is
available i-t cannot be utilized if it is below the
abovementioned temperature, and even though a heat
source having a low temperature of less than 80C is
actually usable, the coefficient of performance
obtained is only 3 or 4, thus rendering effective
utilization impossible. According to the present
invention, however, use is made of the mixture of
lithium bromide hydrate (Li-Br ~2) and alcohol
solution to enable operation of a refrigerator using
even low-temperature hot water at 65 to 68C as the
energy source. Exploiting such a heat source
effectively was difficult in the prior art. Moreover,
the presen-t invention makes it possible to attain a
coefficient of performance of 7 or 8, which is
approximately twice the coefficient of performance of 3
or 4 obtained conventionally. It is thus possible to
utilize a much wider range of thermal energies
possessed by low-temperature geothermal fluids.
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Fig. 7 is a diagrammatic view showing the
arrangement of a water-wheel generator annexed to -the
power generation equipment of a geothermal energy
utilization system according to the embodlment of the
present invention. The arrangment includes a condenser
main body 71, an upper liquid reservoir 72, a central
liquid reservoir 73, a lower liquid reservoir 74l a hot
water bath 75, a wa-ter-wheel turbine 76, and a power
genera-tor 77. The condenser in the present example is
a barometric condenser. Steam supplied to a steam
turbine to perform work as mentioned earlier is cooled
and converted into water by the condenser 71. Some of
this water is fed to a cold water column for being
cooled by the atmosphere and is then utili~ed as
cooling water by the condenser 71. The remainder of
the water is pooled in the hot water bath 75. More
specifically, in the barometric condenser, steam from
the steam turbine contacts jets of cold water ejected
downwardly from a multiplicity of water holes provided
in the bottom of the central liquid reservoir 73, the
steam is condensed by such contact and the resulting
condensate is collected in the lower liquid reservoir
- 74. Steam which has not been condensed by the above
process is condensed by cold water jets falling from
the upper liquid reservoir 72. ~ny uncondensed gas
that still remains is vented from a discharge port
located at the upper portion of the condenser 71. Hot
water which has collected in the lower liquid reservoir~
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12734~
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74 is pooled in the hot water bath 75, whence the hot
water can be introduced -to the next stage of geothermal
energy utilization equipment. To utilize the hot water
even more effectively, however, the hot water which
collects in the hot water bath 75 is provided with a
head by piping or the like and is introduced to the
water-wheel turbine 76. Owing to the head developed,
greater negative pressure is produced in the condenser
and the water-wheel turbine 76 is driven. Though the
pressure in the condenser main body 71 is decided by
the sum of a head H between the liquid level of the
water bath 75 and a standard liquid level and the depth
h of the low liquid reservoir 74, negative pressure can
be generated inside the condenser by introducing the
hot water pooled in the hot water bath 75 to the
water-wheel turbine by discharge piping. This makes it
possible to dispense with or reduce the capacity of a
vacuum pump provided in the prior art for the purpose
of preventing partial loss of vacuum (0.1 - 0.3 ata).
Thus, rather than simply conveying the hot water in the
hot water bath 75 to the next stage of utilization
equipment, after power is generated by the steam
turbine the electrical potential energy thereof is
effectively exploiting and -the head is utilized to
provide the hot water pooled in the condenser with a
head so that the water-wheel turbine may generate
electric power, thus enhancing the power generating
efficiency of the overall system. The end result is
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much more efficient utilization of geothermal energy.
In the geothermal energy utilization system of the
presen-t invention, the aim is to improve the overall
effective utilization of heat energy by arranging the
utilization equipment in dependence upon the amount of
heat energy possessed by the geothermal fluid, as shown
in Fig. 1. When conveying the geothermal fluid from
one stage of utilization equipment to the next,
therefore, it is important to minimize loss and improve
conveyance efficiency in the conveyance path between
stages. An example of such conveyance means
well-suited to the present inven-tion will now be
described.
Fig. 8 is a diagrammatic view for describing an
embodiment of a vacuum conveyance system applied to the
present invention. The system includes a hot water
supply pipe 81, a hot water feed pump 82, a hot water
reservoir column 83, refrigeration equipment 84, a
conveyance pipe 85, a vacuum pump 86, geothermal energy
utilization equipment 87, a hot water level detector
88, a level controller 89, and a drain valve B. Hot
water is fed by the hot water feed pump 82 from the hot
water supply pipe 81 to the hot water reservoir column
83 where -the hot water is pooled. Connected to the hot
water storage column 83 is the conveyance pipe 85,
which is Eor feeding hot water to the geothermal ener~y
utilization equipment 87, which is the next stage. The
vacuum pump 86 is connected to the terminus of the
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73~6
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conveyance pipe 85. The hot water storage column 83 is
provided with the detector 88 for detecting the level
oE -the hot water, and the drain valve ~ for extracting
ho-t water as well as impurity deposits and the like
from the bo-ttom of the column. The level controller
89, which is connected between the detector 88 and the
drain valve B, is Eor controlling the opening and
closing of the valve B in dependence upon the hot water
level detected by the detector 88. More specifically,
the level controller 89 is set to upper and lower limit
values, with a certain control level serving as a
reference value. The level controller 89 opens the
drain valve B -to discharge the hot water and settled
impurities from the bottom of the hot water reservoir
column 83 on the condition that the detected hot water~
level attains the upper limit value, and closes the
drain valve B on the condition that the detected hot
water level attains the lower limit value. An
alternative method ~is to set solely a drainage start
value as the reference value and have the level
controller 89 open the drain valve B only for a
predetermined period of time on the condition that the
detected level attains the drainage start valueO Other
control methods are of course possible. The heat
energy which radiates from the conveyance pipe 85 in
the course of conveying the hot water is effectively
utilized for heating and cooling by the refrigeration
equipmen-t 84.
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The system shown in Fig. 8 is set into operation
by driving the hot water feed pump 82 to supply ho-t to
-the hot water reseroive column 83, the internal
pressure of which is reducecl by operating the vacuum
pump 86. As result, -the hot: water fed into the column
83 is flashed into steam which, free of impurities, is
conveyed smoothly and automatically through the
conveyance pipe 85. As the steam is being conveyed
through the pipe 85, thermal energy leaking to the
exterior of the pipe through its wall is utilized by
the refrigeration equipment 84. Steam conveyed to the
hot water utilization equipment 87 at the terminus of
the conveyance pipe 85 is condensed and utilized as a
hot spring, by way of example. Meanwhile, when the
level of the hot water in the reservoir column 83 rises
and is detected to reach a predetermined level
(reference level) by the level detector 88, the latter
issues an output signal to which the level controller
89 responds by opening the drain valve B. As a result,
excess hot water collected in the reservoir column 83,
as well as impurities which precipitate and settle in
the hot water, is discharged from -the column. Thus,
impurities contained in the hot water and left behind
in the reservoir column 83 by flashing are discharged
through the drain valve B at prescribed times.
In the prior art, situations where piping is of
great length due to a long conveyance dis-tance or where
piping is of a complex configuration are dealt with by
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increasing the motive power for conveyance. This makes
it necessary to install a fairly large pump for
conveyance pipes of larger diameter or length or for
piping of some complexity. 'rhe disadvantageous result
is greater cost for equipment, operation and
maintenance. In addition, since the hot wate:r is
conveyed by ordinary piping, the impurities contained
in the hot water are also fed through the piping.
These impurities form scale which deposits on the
piping walls and eventually blocks the piping flow
path. The scale may also attach itself to the interior
of the equipment that utilizes the hot water and thus
cause equipment damage or failure. Removing such scale
demands even more equipment and extra expense.
In the system of the present invention, however,
the vacuum pump 86 is operated at the terminus of the
conveyance pipe 85 to evacuate the interior of the pipe
85 and the interior of the hot water reservoir column
83, thereby flashing -the hot water and conveying the
same automatically in the form of steam, as set forth
above. As a result, 90 to 95~ of the impurities can be
removed by being forced to remain in the hot water left :
in the reservoir column. Moreover, since the system
functions by relying solely upon operation of the
vacuum pump 86, conveyance of the steam can be
accomplished at 30% of the power used conventionally to
transport hot water thanks to the expansion of the hot
water steam, even if the hot water .has a comparatively
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low temperature of 50 - 60C.
Figs. 9(A), (B), (C) are views for describing a
embodiment of a hot water conveyance path applied to
the present invention. The arrangement includes a
concrete frame 91, a conveyance pipe 92, a flexible
pipe 93, an insulating air layer 94, an insulator 95, a
support 96, a channel 97 and a drain 98.
As shown in Fig. 9(A), the conveyance pipe 92
constitutes a concrete pipe through which hot water is
passed. The flexible pipe 93 covers the conveyance
pipe 92 and is constituted by a plastic conduit (e.g,
of the type manufactured by Furukawa Denko). The
insulating air layer 94 is formed between the
conveyance pipe 92 and flexible pipe 93 and is filled
with air for insulating purposes. The space between
the flexible pipe 93 and concrete frame 91 is filed
with the insulator 95. The flexible pipe 93 is fixedly
positioned in the concrete frame 91 by the support 96.
Fig. 9(B) is a sectional view taken along line A-B of
Fig. 9(A) and showing the portion at which the support
96 is provided.
Since the hot water conveyance path having the
construction shown in Figs. 9(A), (B) has the
insulating air layer 94 interposed between the
conveyance pipe 92 and the plastic, flexible pipe 93,
the pipe 92 is capable of maintaining heat resistance.
In addition, if hot water should leak from the
conveyance pipe 92, expansion of the insulating air
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layer 9~ due to a rise in temperature resul-ts in the
production of pressure that acts to impede leakage.
Even if hot water should manage to leak out of the
conveyance pipe 92, the fact that the flexible pipe 93
is made of water--tight plastic assures that the hot
water will remain in the insulating air layer and not
reach the insulator 95. Since the insulating mechanism
thus remains unaffected, a drop in temperature is
prevented from occurring. Further, since the hot water
leakage does not permeate and degrade the insulator 95
as is common in the prior art, the quality of the
insulator can be maintained. It is also unnecessary to
use an insulator of high cost.
Various methods of conveying a geothermal fluid,
mainly hot water, are known in the prlor art. One
method involves covering the channel conveying the hot
water with concrete and passing the hot water through
the channel to achieve conveyance. Another method is
to cover a concrete channel with a glass wool insulator
(or a double layer of urethane) and convey the hot
water through the concrete channel. However, these
conventional methods of hot water conveyance often
demand use of a structure of the type in which an iron
pipe is laid in a trench formed in the earth, and the
cost of maintaining a temperature drop of no more than
0.1 - 1C/km is considera~le. This has delayed the
development of conveyance systems for multi-purpose
use. More specifically, when hot water leaks from the
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concrete pipe, permeates the insulator and eventually
destroys it owiny to attendant expansion caused by the
hea-t ~rom the water, the abovementioned temperature
drop can no longer be maintained. Insufficient
insulation can result in a large drop in temperature,
especially where the atmospheric temperature is low,
thus leading to a significant loss of effective energy.
According to the above-described hot water conveyance
path of the present invention, however, leakage from
the conveyance pipe 92 of concrete or the like is
prevented from reaching the insulator layer 94 by the
flexible pipe 93 made of plastic. This assures that
the insulator will not be adversely affected by the
leakage. Accordingly, the insulating effect can be
fully maintained even if an inexpensive insulator is
used. Further, the insulating effect is enhanced and
leakage is either blocked or limited by virtue of the
insulating air layer 94 furnished between the :~
conveyance pipe 92 and the flexible pipe 93.
Thus, as is evident from the foregoing
description, the present invention makes it possible to
exploit virtually all of the heat energy possessed by
geothermal fluids ranging from hi~h-temperature
geothermal fluids to those of low temperature
utilizable for hot springs. Geothermal energy can thus
be utilized with a very high efficiency overall. In
addition, since utilization equipment may be installed
over a number of stages, ordinary electricity, the
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energy for hea-ting and cooling and the requirements for
a hot spring can be provided for by the heat energy
extracted from a geothermal production well. This is
highly conducive to conservation of energy resources.
As many apparently widely different embodiments of
the present inven-tion can be made without departing
from the spirit and scope thereof, it is to be
understood that the invention is not limited to the
specific embodiments thereof except as de-fined in the
appended claims.
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