U.S. patent application number 12/357444 was filed with the patent office on 2009-08-27 for low-temperature power plant and process for operating a thermodynamic cycle.
This patent application is currently assigned to E-POWER GMBH. Invention is credited to Helge B. Petersen, Ingo Schroter.
Application Number | 20090211251 12/357444 |
Document ID | / |
Family ID | 40794378 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090211251 |
Kind Code |
A1 |
Petersen; Helge B. ; et
al. |
August 27, 2009 |
Low-Temperature Power Plant and Process for Operating a
Thermodynamic Cycle
Abstract
The invention concerns a mechanism for operating a thermodynamic
cycle, particularly a low-temperature power plant, as well as a
related process, whereby a low-temperature mass stream (1) feeds a
first heat stream to a working fluid (6) circulating in a first
cycle at an initial temperature level (T.sub.1), whereby subsequent
to an expansion of the working fluid in an expansion machine (7) a
second heat stream is extracted from the working fluid (6) at a
lower expansion temperature level (T5) with respect to the initial
temperature level (T1) for an improvement of the energy
exploitation of the thermodynamic cycle or the low temperature
power plant, which is pumped to a higher pump temperature level and
is fed to the low temperature mass stream (1) and/or fed at least
partially to the first cycle.
Inventors: |
Petersen; Helge B.;
(Frankfurt am Main, DE) ; Schroter; Ingo;
(Dreieich, DE) |
Correspondence
Address: |
MCDONNELL BOEHNEN HULBERT & BERGHOFF LLP
300 S. WACKER DRIVE, 32ND FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
E-POWER GMBH
Langen
DE
|
Family ID: |
40794378 |
Appl. No.: |
12/357444 |
Filed: |
January 22, 2009 |
Current U.S.
Class: |
60/645 ;
60/643 |
Current CPC
Class: |
F01K 25/00 20130101;
F01K 13/00 20130101; F01K 25/08 20130101 |
Class at
Publication: |
60/645 ;
60/643 |
International
Class: |
F01K 27/00 20060101
F01K027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 2008 |
DE |
102008005978.1 |
Claims
1. Thermodynamic machine, particularly a low-temperature power
plant, with at least one first cycle (20) for circulating a working
fluid, whereby the first cycle (20) has at least one expansion
machine (7) and at least one heat exchanger (24; 27) for feeding a
first heat stream from a low-temperature mass stream (1) into the
first cycle (20), whereby a first heat transformer (21; 26) is
provided in heat stream connection with the first cycle (20), with
a colder side (23) downstream of the expansion machine (7), and has
a heat stream connection with a warmer side (22) with the
low-temperature mass stream (1) or the first cycle (20).
2. Thermodynamic machine according to claim 1 further comprising a
second cycle (25), particularly an ORC cycle, with a second heat
transformer (26), which is located in the same way as the first
heat transformer (21), sequentially to the first cycle (20),
whereby the first (21) and the second heat transformer (26)
respectively have a heat stream connection with the low-temperature
mass stream (1) between the first (20) and the second cycle (25)
with their warmer side (22).
3. Thermodynamic machine according to claim 1 further comprising a
second cycle (25) that is fed by a branch stream (28) by the
low-temperature mass stream (1) downstream of the first cycle (20),
whereby the first heat transformer (21) with its warmer end (22)
has a heat stream connection with the branch stream (28) upstream
of the second cycle (25), and whereby a downstream feedback of the
branch stream (28) is provided downstream of the second cycle (25)
into the low-temperature mass stream (1).
4. Thermodynamic machine according to claim 1 further comprising a
second cycle (25) that has a downstream feedback (29a) to an inlet
(29b), which has a heat stream connection with the warmer end (22)
of the first heat transformer (21).
5. Thermodynamic machine according to claim 1 further comprising at
least one recirculation line (30) provided for feedback of a branch
stream (28) of the low-temperature mass stream (1) downstream of
the first cycle (20), whereby the warm side (22) of the first heat
transformer (21) has a heat stream connection with the branch
stream (28).
6. Thermodynamic machine according to claim 1 wherein the warm side
(22) of the first heat transformer (21) in a section between a
vaporizer (5) and expansion machine (7) has a heat stream
connection with the first cycle (20).
7. Process for operating a thermodynamic cycle, particularly in a
low-temperature power plant according to claim 1, with at least one
cycle (20, 25), in which a working fluid (6) circulates, to which a
first heat stream is fed by a low-temperature mass stream (1) at an
initial temperature level, whereby after an expansion of the
working fluid (6) in an expansion machine (7) releasing mechanical
energy a second heat stream is extracted from the working fluid (6)
at an expansion temperature level that is lower compared to the
initial temperature level wherein the second heat stream in at
least one heat transformer (21, 26) is pumped to a pump temperature
level which is higher or equal to the initial temperature level and
is at least partially fed back to low-temperature mass stream (1)
and/or the at least one cycle (20, 25).
8. Process according to claim 7 wherein the second heat stream,
which is raised to the pump temperature level, increases a
temperature of the low-temperature mass stream (1) and/or a
temperature of the working fluid (6) in the at least one cycle (20,
25).
9. Process according to claim 7 wherein the low-temperature mass
stream (1) is increased by a partial feedback of a low-temperature
mass stream outflow (29) that is heated by the second heat
stream.
10. Process according to claim 7, wherein at least one cycle (20,
25) is operated as an organic Rankine cycle (ORC).
11. Process according to claim 7 wherein the at least one cycle
(20, 25) is operated as a Kalina cycle.
12. Process according to claim 7 wherein at least two cycles,
particularly two ORC cycles (20; 25), are sequentially fed by the
low-temperature mass stream (1), whereby a feedback into the
low-temperature mass stream (1) of the second heat streams of the
cycles that is pumped to the respective pump temperature level
takes place between the first cycle (20) and the second cycle
(25).
13. Process according to claim 7 wherein at least two cycles (20,
25), particularly two ORC cycles, are provided, whereby from the
low-temperature mass stream (1) downstream of the first cycle (20)
a branch stream (28) for feeding a second cycle (25) is branched
off, which downstream of the second cycle (25), is reunited
downstream with the low-temperature mass stream (1), whereby the
second heat stream that is pumped to the pump temperature level of
the first cycle (20) is fed to the branch stream (29).
14. Process according to claim 7 wherein at least two cycles (20,
25), particularly two ORC cycles are provided, whereby the second
heat stream of the first cycle (20) that is pumped to the pump
temperature level is fed to an outflow of the second cycle (25),
which is fed again to the second cycle (25) as inflow.
15. Process according to claim 7 wherein a branch stream (28) is
branched off from the low-temperature mass stream (1) downstream of
a cycle (20), which is heated by the second heat stream to the pump
temperature level and is fed to the low-temperature mass stream (1)
upstream of the cycle (20).
16. Process according to claim 15 wherein the branch stream (28) is
dimensioned in such a way, that its pump temperature level prior to
recirculation corresponds to the initial temperature level of the
low-temperature mass stream (1).
17. Process according to claim 7 wherein the second heat stream is
extracted downstream of the expansion machine (7) and after being
pumped to the pump temperature level, is fed back into the cycle
(20), particularly directly before the expansion machine (7).
18. Process according to claim 7 wherein a temperature of a heat
transformer fluid is heated by the second heat stream and raised by
at least two ejector-adsorbers to or above the pump temperature
level to pump the second heat stream to the pump temperature
level.
19. Process according to claim 7 wherein a heat transformer fluid
heated by a second heat stream is at least essentially
adiabatically compressed and thereby heated to or above the higher
pump temperature level to pump the second heat stream to pump
temperature level.
20. Thermodynamic machine, according to claim 1, with the at least
one heat transformer (21; 26) being configured such that from a
first mass stream with a first temperature level a second mass
stream with a second temperature level is produced with the second
mass stream being equal or less than the first mass stream and with
the second temperature level being higher than the first
temperature level.
Description
[0001] The invention concerns a mechanism for operating a
thermodynamic cycle, particularly a low-temperature power plant, as
well as a related process, whereby a low-temperature mass stream
feeds a first heat stream to a working fluid that circulates in a
first cycle at an initial temperature level and whereby subsequent
to an expansion of the working fluid in an expansion machine, a
second heat stream is extracted from the working fluid at a lower
expansion temperature level relative to the initial temperature
level, especially in a cooling device.
[0002] Thermodynamic cycles of this type are used especially in
low-temperature power plants for recovering the energy from a
low-temperature mass stream, for example, with a turbine, which
serves as an expansion machine. Low-temperature power plants find
application, for example, in geothermal energy, solar energy, in
energy recovery from biomass, and waste heat which is created, for
example, in rotting or fermenting processes, i.e. in a landfill or
similar. In the course of saving fossil fuels and in the course of
an attempt of dispensing with such fossil fuels completely,
interest in processes of this type is growing steadily.
[0003] Based on the smaller temperature difference in the operation
of a thermodynamic cycle compared to a high-temperature power
plant, the degree of effectiveness of a low-temperature power plant
is naturally always significantly lower than in a high-temperature
power plant. Even more, as the temperature of a low-temperature
mass stream is specified based on circumstances, for example, a
geothermal heat source or a process that conveys waste heat, there
are attempts to improve the energy exploitation of a
low-temperature power plant with optimization measures.
[0004] It is the objective of the present invention to improve the
energy exploitation of operating a low-temperature power plant,
especially, with only small changes to the apparatus of existing
thermodynamic cycles.
[0005] According to the invention, this objective is solved by a
thermodynamic machine, particularly a low-temperature power plant
with the characteristics of claim 1, as well as by a process for
operating a thermodynamic cycle, particularly a low-temperature
power plant with the characteristics of claim 6. Advantageous
embodiments and further developments are indicated in the
respective dependent claims.
[0006] In a thermodynamic machine according to the invention,
particularly in a low-temperature power plant with at least one
first cycle for circulating a working fluid, the first cycle has at
least one expansion machine and at least a first heat exchanger for
feeding the first heat stream from a low-temperature mass stream
into the first cycle, whereby at least one heat transformer is
provided with its colder side between the expansion machine and the
cooling mechanism or in the cooling device, which is, in
particular, a condenser that is in heat stream connection with the
cycle, and with its warmer side with the low-temperature mass
stream or is in heat stream connection with the first cycle. As
heat stream connection, the heat transformer has, for example, a
heat exchanger on its colder side and on its warmer side
respectively, Preferably, this makes an increase in the degree of
effectiveness or a heat throughput of a thermodynamic cycle
possible, particularly of a low-temperature power plant.
Especially, existing low-temperature cycles can be retooled with
little time and effort by the use of a heat transformer.
[0007] For example, a water stream of geothermal brine is used as a
low-temperature mass stream. At sufficient temperature of the
geothermal brine, [Note: original says "Sonde" instead of
Sole=brine.] the low-temperature mass stream can also be present in
the form of steam. However, in place of water, other fluids can
also be used as low-temperature mass streams. Alternatively to a
geothermal brine [Note: original has Sonde], the low-temperature
mass stream can also be brought to its application temperatures
with solar heat, waste heat from biomass processes, waste heat from
other processes or the like.
[0008] In particular, the working fluid is selected in such a way
that at a temperature of the low-temperature mass stream it is
present in vaporized form, whereas it is present in liquid phase at
one of the lower temperature levels of the cycle. Depending on the
application temperature, commonly used cooling agents are used, for
example, pentane, butane, other hydrocarbons or the like. In a
simple cycle, for example, the working fluid is vaporized in a
first step in a heat exchanger by the low-temperature mass stream,
in a second step it is expanded in a turbine that acts as an
expansion machine and subsequently it is condensed again, so that
it can be heated anew by the low-temperature mass stream in the
heat exchanger.
[0009] For example, the cycle can be operated as an organic Rankine
cycle, an ORC. In the process, an ORC fluid, for example, pentane,
butane or another cooling agent, is heated in a pre-heater,
vaporized in a vaporizer that is heated by the low-temperature mass
stream, conveyed to a turbine that acts as an expansion machine and
expanded there, and cooled down in a condenser so that it can be
fed into the cycle anew. In this process, a recuperator is provided
between the turbine and the condenser which serves to recover
residual heat from the exhaust emission of the turbine. The amount
of heat that is generated in this process is used to feed the
pre-heater. In a process according to the invention, a heat
transformer is provided in addition, which extracts a second heat
stream from the working fluid subsequent to the turbine or the
expansion machine and after the recuperator and prior to a cooling
device, which is, in particular, a condenser, and pumps such to a
higher pump temperature level and again feeds it into the cycle or
the low-temperature mass stream.
[0010] With respect to the fundamentals of an ORC process,
reference is made to DE 692 18 206 T2, to the entirety of which
reference is made within the framework of the revelation.
Preferably, use of an ORC cycle makes it possible to retool
existing systems that work according to this principle at little
expense to improve their degree of effectiveness.
[0011] In a different embodiment, the cycle can be operated as a
Kalina cycle. In doing so, the Kalina process uses a method that is
similar to an ORC process, whereby the working fluid is first
heated, vaporized, in the expansion machine, for example, a
turbine, pressure is released, it is condensed and subsequently
conveyed to heating again. In contrast to an ORC process, the
working fluid in the vaporizer or desorber is split into a steam
phase and a watery phase with a subsequent separator, whereby the
steam is conveyed through the expansion machine, while the tension
of the fluid phase is released after a potential recovery of heat
by a restrictor of the exit pressure of the expansion machine,
particularly the turbine. Subsequently, the two partial streams are
united again and stream back through an internal heat exchanger to
a condenser or absorber. After the condensation/absorption,
pressure is increased again, for example, by a feed pump. With
respect to the fundamentals of an ORC process, reference is made to
US 2004 0182084 A1, to the entirety of which reference is made in
the revelation.
[0012] In addition to these embodiments, any type of
low-temperature power plant can be operated in accordance with the
invention.
[0013] Particularly downstream of the expansion machine, a cooling
device is provided, for example, a condenser or the like, whereby
the second heat stream is extracted from the low-temperature mass
stream prior to or in the cooling mechanism.
[0014] As heat transformer, a system with at least two
ejector-adsorbers is used, as described in patent specification DE
34 08 192 C2, to the entirety of which reference is made within the
framework of the revelation. Alternatively, a power heating machine
with an at least essentially adiabatic compression step of a
working fluid can be used.
[0015] According to a further development, a second cycle,
particularly an ORC cycle with a second heat transformer which is
mounted in the same way as the first heat transformer, located
sequentially to the first cycle, whereby the first and second heat
transformer with their warm side respectively are in heat stream
connection with the low-temperature mass stream between the first
and the second cycle. For this purpose, the heat transformers are,
for example, respectively provided with heat exchangers at their
ends, which are, for one, in heat stream connection on the warmer
side of the heat transformer with the low-temperature mass stream,
and for another, on the colder side of the heat transformers they
are in heat stream connection with the respective cycle. The
temperature on the warmer side of the second heat transformer is
thereby preferably lower than the temperature on the warmer side of
the first heat transformer. Preferably, the heat exchangers of the
heat transformers are located in the low-temperature mass stream in
such a way that first the heat of the second heat transformer is
given off to the low-temperature mass stream and subsequently the
heat of the second heat transformer. Thereby, the temperature of
the low-temperature mass stream preferably increases stepwise
upstream of the second cycle.
[0016] In a further embodiment, a second cycle is provided, which
is fed downstream of the first cycle by a branch stream of the
low-temperature mass stream, whereby the first heat transformer
with its warmer end is in heat stream connection with the branch
stream upstream of the second cycle and whereby a down-stream
feedback of the branch stream is provided downstream of the second
cycle into the low-temperature mass stream. For example, an
existing heat cycle, particularly according to the ORC principle,
can be improved in its energy exploitation by coupling it with a
second heat cycle, particularly according to the ORC principle, so
that only a feeder line must be placed from one outlet of the first
cycle to the inlet of the second cycle and a downstream line from
the second cycle again to the first downstream line, whereby in
addition to the basically ordinary heat cycles according to, for
example, the ORC principle, a heat transformer is used in such a
way that its warm end is in heat stream connection with the inlet
line of the second heat cycle. Preferably, electricity exploitation
can thereby be improved by approximately 15%.
[0017] In order to realize a closed low-temperature mass stream
cycle, a second cycle can be provided which shows a downstream
feedback to its inlet, which is in heat stream connection with the
warmer end of the first heat transformer. The first and second
cycle stream separately, in particular, they are completely
separate from one another and are only connected with one another
in heat stream connection by the first heat transformer.
[0018] In a further development, at least one feedback line for
feeding back a partial stream from the low-temperature mass stream
is provided downstream of the first cycle, whereby the warm side of
the first heat transformer is in heat stream connection with this
partial stream. Thereby, the low-temperature mass stream is
preferably increased upstream of the first cycle. Particularly,
heat transformers and feedback lines are to be dimensioned such
that the recycled partial stream can be heated precisely to the
initial temperature level, i.e. the first temperature of the
low-temperature mass stream.
[0019] In another embodiment, the warm side of the first heat
transformer is in heat stream connection with the first cycle in a
section between the vaporizer and the expansion machine. In
particular, in this section a corresponding heat exchanger is
provided which is fed by the warm side of the first heat
transformer. For this reason a temperature of the working fluid
directly before entry into the expansion machine is preferably
increased and thereby the energy exploitation of the expansion is
improved.
[0020] Moreover, the invention concerns a process for operating a
thermodynamic cycle, particularly a low-temperature power plant,
particularly according to one of the previously described
embodiments in which a working fluid circulates, to which a first
heat stream is fed by a low-temperature mass stream at an initial
temperature level, whereby after expansion of the working fluid in
an expansion machine--by releasing mechanical energy--a second heat
stream is extracted from the working fluid at a second lower
expansion temperature level with respect to the initial temperature
level, particularly prior to entry into a cooling device, which is
pumped to a pump temperature level that is higher or equal to the
initial temperature level in at least one heat transformer, and is
again fed to the low-temperature mass stream and/or the first cycle
at least in part.
[0021] Advantageously, this makes an increase in the degree of
effectiveness or the heat throughput rate of the thermodynamic
cycle possible, particularly of a low-temperature power plant.
[0022] The initial temperature level which corresponds to the
temperature level of the low-temperature mass stream is, for
example, a temperature between an ambient exterior temperature and
approximately 200.degree. C., for example, 120.degree. C. The pump
temperature level is preferably at least equally high,
advantageously, however, higher than the initial temperature
level.
[0023] In order to pump the second heat stream to the higher pump
temperature level, according to a further development, a
temperature of a heat transformer fluid that is heated by a second
heat stream with two ejector adsorbers is raised to or above the
higher pump temperature level.
[0024] In the process, for example, the heat transformer fluid is
driven out of a fixed adsorption means by a relatively low first
pressure, the gaseous heat transformer fluid that is created during
the ejection at a relatively low first temperature is transformed
into a fluid phase by giving off heat and heat transformer fluid
that is present in fluid phase at an intermediate second
temperature and at a relatively higher pressure is transformed into
the gaseous phase by absorbing heat, the gaseous working fluid by
giving off useful heat at a relatively high third temperature is
adsorbed by a fixed adsorption means and the process is maintained
by cyclical ejection and adsorption of working fluid in the
adsorption means or parts thereof, whereby at least two ejection
adsorbers present at varying temperatures and pressures exchange
heat via heat exchange devices from the heat transformer
fluid-richer to the heat transformer fluid-poorer
ejection-adsorber, whereby subsequent to the heat exchange between
these ejector-adsorbers, heat transformer fluid is exchanged
between these ejection adsorbers by pressure adjustment, and is
driven out of the heat transformer fluid-richer adsorption means by
absorbing heat and is adsorbed in the heat transformer fluid-poorer
adsorption means by generating heat.
[0025] In a further variation, a heat transformer fluid heated by a
second heat stream is at least essentially adiabatically compressed
and thereby heated to or above the pump temperature level in order
to pump the second heat stream to the pump temperature level. A
suitable cooling agent such as, for example, pentane, butane or
another suitable hydrocarbon compound is used as heat transformer
fluid depending on the temperature range.
[0026] According to a further development it is provided that
through a second heat stream that is raised to the pump temperature
level, a temperature of the low-temperature mass stream or/and a
temperature of the working fluid is increased in the first cycle.
Preferably, this makes an increase of the degree of effectiveness
of the thermodynamic cycle possible, particularly the
low-temperature power plant. In this process, for example, the
second heat stream is pumped to the higher pump temperature level,
which lies above the initial temperature level, the temperature of
the low-temperature mass stream. In this manner, the temperature of
the low-temperature mass stream in increased. Similarly, an
increase in the temperature of the working fluid can be provided at
one point in the cycle. Preferably, a maximum temperature of the
working fluid is increased within the thermodynamic cycle.
[0027] Alternatively or additionally, it can be provided that the
low-temperature mass stream is increased by a partial feedback of a
low-temperature mass stream outflow that is heated with a second
heat stream. Preferably, the partially recirculated low-temperature
mass stream outflow is pumped to the same temperature level as the
incoming low-temperature mass stream. It is self-explanatory that
the volume stream or mass stream transported out of a geothermal
source, for example, is not changed in the process. However, as a
result of the recirculation, the mass stream or volume stream that
passes through the cycle is increased.
[0028] Various embodiments and procedures or arrangements can be
provided for the operation of a cycle. In a first provided process,
at least two cycles, particularly ORC cycles, are sequentially fed
by the low-temperature mass stream, whereby the recirculation into
the low-temperature mass stream of the second heat streams that are
respectively pumped to the higher pump temperature level takes
place between the first and the second cycle. Preferably, this
makes an increase in temperature of the low-temperature mass stream
possible which has passed through the first cycle, particularly the
ORC process, and an enhanced energy exploitation of the second ORC
process.
[0029] In an additional variant, at least two cycles are provided,
particularly ORC cycles, whereby from the low-temperature mass
stream downstream of the first cycle a branch stream is branched
off for feeding the second cycle, which is reunited again
downstream with the low-temperature mass stream downstream of the
second cycle, whereby the second heat stream that is pumped to the
higher temperature level of the first cycle is conveyed to the
branch stream. Advantageously, this makes an enhancement of the
existing system possible by coupling in a second thermodynamic
cycle, particularly an ORC cycle.
[0030] According to a further development, at least two cycles,
particularly two ORC cycles are provided, whereby the second heat
stream that is pumped to the pump temperature level of the first
cycle is fed to an outflow of the second cycle, which is fed to the
second cycle again as inflow. As a result, the second ORC cycle can
be designed completely separate from the first ORC cycle except for
a heat stream connection. In this process, the heat stream is
conveyed without exchanging a mass stream between the two
cycles.
[0031] In an additional embodiment it is provided that from the
low-temperature mass stream downstream of the first cycle a branch
stream is branched off which is heated with the second heat stream
that is pumped to the higher pump temperature level and is fed
again to the low-temperature mass stream upstream of the first
cycle.
[0032] Thereby it is provided that the branch stream is dimensioned
in such a way that its pump temperature level corresponds to the
initial temperature level of the low-temperature mass stream prior
to being recirculated. In this way, the low-temperature mass stream
is enlarged upstream of the first cycle. Advantageously, this leads
to enhanced energy exploitation. Simultaneously, particularly a
low-temperature mass stream outflow is not increased in spite of
the higher low-temperature mass stream passing through the first
cycle.
[0033] In a different embodiment, the second heat stream is
extracted downstream of the expansion machine and after being
pumped to the higher pump temperature level, is again fed into the
first cycle particularly directly before the expansion machine.
Preferably, a temperature in a mass stream of the working fluid in
the first cycle between a vaporizer and the expansion machine is
thereby increased. In the process, the heat potential in this mass
stream is increased in particular.
[0034] In the following, the invention is explained using the
drawing. However, the invention is not limited to the combination
of characteristics shown there. Rather, characteristics shown in
the respective figures as well as the description can be combined
with one another within the framework of the protective area of the
claims for further development.
[0035] Shown are:
[0036] FIG. 1 design of an ORG cycle according to prior art,
[0037] FIG. 2 design of a Kalina cycle according to prior art,
[0038] FIG. 3 a first embodiment of a cycle according to the
invention,
[0039] FIG. 4 a second embodiment of a cycle according to the
invention,
[0040] FIG. 5 a third embodiment of a cycle according to the
invention,
[0041] FIG. 6 a fourth embodiment of a cycle according to the
invention,
[0042] FIG. 7 a fifth embodiment of a cycle according to the
invention,
[0043] FIG. 8 a sixth embodiment of a cycle according to the
invention, and
[0044] FIG. 9 a seventh embodiment of a cycle according to the
invention.
[0045] The design shown in FIG. 1 is a design used in a geological
application of an ORC cycle according to prior art. For supplying a
low-temperature mass stream 1, a deep well pump 2 is provided,
which transports thermal water from a geothermal well 3 that has a
temperature of 80.degree. C. Thus the low-temperature mass stream 1
thus provides an initial temperature level of 80.degree. C. and
heats a working fluid 6 by means of a first heat exchanger 4 in a
vaporizer 5, which is brought to vaporization in vaporizer 5. In
the embodiment according to FIG. 1, working fluid 6 is pentane.
After vaporization, working fluid 6 is fed to a turbine 7 that acts
as an expansion machine in which vaporized working fluid 6 works
and is being released. In the process, the temperature of working
fluid 6, which subsequently runs through a recuperator 8 is
decreased to an expansion temperature level. Downstream of
recuperator 8, working fluid 6 runs through a condenser 9, in which
working fluid 6 is condensed again. After condensation, working
fluid 6 is fed again to vaporizer 5 by delivery pump 10 through
recuperator 8 and a pre-heater 11. In this process, recuperator 8
serves to at least partially extract heat contained in working
fluid 6 after expansion in turbine 7 and feed it again to the
working fluid 6 prior to entry into pre-heater 11.
[0046] The design of a Kalina cycle according to prior art that is
shown in FIG. 2 is in large part similar to the ORC design shown in
FIG. 1. A low-temperature mass stream 1 that is fed by a geothermal
well 3 heats a working fluid 6 in a desorber 12 which is then
desorbed. Subsequently, this working fluid 6 is split into a steam
phase 14 and a watery phase 15 in a separator 13.
[0047] Ammonia mixed with water is used as working fluid 6. For
this reason, the steam phase 14 is ammonia-rich steam and the
watery phase 15 is an ammonia-poor watery phase 15. Subsequently,
the steam phase 14 is delivered to a turbine 7 that acts as an
expansion machine in which steam 14 is expanded and thereby work is
performed. The watery phase 15 is put together again with the steam
phase 14 via a high temperature recuperator 16 and a restrictor 17
after exiting turbine 7, and conveyed again to an absorber 19 via a
low-temperature recuperator 18. Subsequently, working fluid 6 is
again fed to desorber 12 by a feed pump 10 via low temperature
recuperator 18 and high temperature recuperator 16, as well as
pre-heater 11.
[0048] Based on this prior art, the invention is shown in the
following by using various variants schematically and as
examples.
[0049] In a first variant as per FIG. 3, a first cycle 20 is
provided which is an ORC cycle as it is shown in FIG. 1, for
example. Additionally, a first heat transformer 21 is provided
which has a warmer side 22 and a colder side 23. The warm side 22
has a heat stream connection with a low-temperature mass stream 1
via heat exchanger 24. This low-temperature mass stream 1 has a
mass stream dm.sub.1/dt at an initial temperature level T.sub.1.
Thereby, the initial temperature level T.sub.1 is 120.degree. C.
After passing through heat exchanger 24, low-temperature mass
stream 1 has a temperature T.sub.2, which is 126.34.degree. C. The
increase of temperature T.sub.2 with respect to initial temperature
level T.sub.1 is a result of, that a heat stream--not shown--in the
ORC arrangement as per FIG. 1 between turbine 7 that is shown there
and recuperator 8 that is shown there, a heat exchanger--not
shown--is used to heat the cold side 23 of heat transformer 21,
whereby the second heat stream that is extracted at an expansion
temperature level is pumped to a pump temperature level above the
initial temperature level T.sub.1.
[0050] In an embodiment of the process, condenser 9 and recuperator
8 that are shown in FIG. 1 can also be omitted so that working
fluid 6--after the turbine--is heated for extraction of the second
heat stream by the--not shown--heat exchanger and is conveyed from
there to the pre-heater.
[0051] Downstream of ORC cycle 20, the low-temperature mass stream
has a temperature T.sub.3. This temperature is lower than the first
temperature level T.sub.1 as well as the second temperature
T.sub.2.
[0052] In place of ORC cycle 20, in an embodiment according to the
invention that is not shown, a Kalina cycle can also be used.
[0053] The following table shows exemplified calculations for
salt-containing brine with a salt content of 100 g per liter as
low-temperature mass stream 1. The low-temperature mass stream 1 is
indicated in the first column as delivery in I/s and the density of
the brine is 1077.84 kg/m.sup.3. For reasons of clarity, however,
only the volume streams are indicated. The inlet temperature and
thus the initial temperature level T.sub.1 is 120.degree. C., as
shown in column 2. The outlet temperature T.sub.3 is 75.degree. C.,
as shown in column 3. The heat capacity of the brine of 3.2
kJ/(kgK) results in thermal output as shown in column 4. When a
degree of effectiveness of the power plant is assumed as indicated
in column 5, electrical output results as shown in column 6. Use of
a heat transformer 21, which pumps the second heat stream to the
higher pump temperature level of 160.degree. C. after it has been
extracted from working fluid 6 subsequent to expansion in the
turbine, leads--assuming waste heat of 20%--to an output of a
second heat stream as per column 7. Assuming that this second heat
stream after it is pumped to 160.degree. C. at a loss of 10% is
input into the low-temperature mass stream, input heat as per
column 8 results, which leads to a temperature increase of
low-temperature mass stream 1 as per column 9 of 6.34 K, at a
degree of effectiveness of 12% for the power plant. Thus an
improvement of the electrical effectiveness of the low-temperature
power plant of 14.1% is the result.
[0054] For other waste heat that is dissipated by the heat
transformer, other values are attained respectively. For example,
at a delivery of 100 I/s and a degree of effectiveness of the power
plant of 12% at waste heat of 25%, a temperature increase of the
low-temperature mass stream 1 of 7.92K results and an improvement
of the degree of effectiveness of the low-temperature power plant
of 17.6%.
[0055] At a delivery of 100 I/s when the power plant has a degree
of effectiveness of 12% and waste heat of 30% a temperature
increase of 9.5K results and an improvement of the degree of
effectiveness of the low-temperature power plant of 21.1%.
TABLE-US-00001 Delivery Inlet Outlet Thermal KW Electrical Output
Input Temperature Increase in in Temp. in Temp. in output in
effectiveness output in heat in heat in increase in effectiveness
l/s .degree. C. .degree. C. kW in % kW kW kW .degree. C. % 50 120
75 7,760 12 931 1,366 1,093 6.34 14.1% 100 120 75 15,521 12 1,863
2,732 2,185 6.34 14.1% 150 120 75 23,281 12 2,794 4,098 3,278 6.34
14.1% 50 120 75 7,760 14 1,086 1,335 1,068 6.19 13.8% 100 120 75
15,521 14 2,173 2,670 2,136 6.19 13.8% 150 120 75 23,281 14 3,259
4,004 3,204 6.19 13.8% 50 120 75 7,760 16 1,242 1,304 1,043 6.05
13.4% 100 120 75 15,521 16 2,483 2,608 2,086 6.05 13.4% 150 120 75
23,281 16 3,725 3,911 3,129 6.05 13.4%
[0056] In the variant shown in FIG. 4, in addition to a first ORC
cycle 20, a second ORC cycle 25 is provided, which is located
sequentially downstream of first ORC cycle 20 relative to a
low-temperature mass stream 1. Further, a first heat transformer,
21, as well as a second heat transformer 26 is provided which have
a heat stream connection with low-temperature mass stream 1 with
their warmer sides 22 respectively. In turn, the cold sides 23 of
the heat transformers are located, as in the previous example of an
embodiment as per FIG. 3, down-stream of the turbine. The second
heat flows extracted from the waste gas streams of the turbine
respectively at an expansion temperature level, are pumped
respectively to a higher pump temperature level in first heat
transformer 21 or in second heat transformer 26. As a result of a
corresponding location of first heat exchanger 24 and a second heat
exchanger 27, a step-wise temperature increase of the first
low-temperature mass stream 1 downstream of first ORC cycle 20 can
be provided from a temperature T.sub.2 to a temperature T.sub.3 and
then subsequently to a temperature T.sub.4. Thereby in turn,
temperature T.sub.1 is lower than the initial temperature level
T.sub.1, whereby temperature level T.sub.5, at which
low-temperature mass stream 1 exits again downstream of the second
ORC cycle 25, is lower than temperature T.sub.4.
[0057] By using the previously mentioned brine as low-temperature
mass stream, at an initial temperature level T.sub.1 of 120.degree.
C. and an exit temperature T.sub.5 of 75.degree. C., the following
values result for temperatures T.sub.2, T.sub.3 and T.sub.4,
whereby the higher pump temperature level of the first and second
heat transformer is respectively 160.degree. C. and 20% of the
waste heat of the turbine is dissipated by the heat transformers at
a loss of 10%: T.sub.2=97.5.degree. C.,
T.sub.3=T.sub.2+3.96.degree. C., T.sub.4=T.sub.2+3.96.degree.
C.+4.26.degree. C. Thereby, the degree of effectiveness of the
overall system is improved by 11.2%.
[0058] In a variant according to FIG. 5, a first ORC cycle 20 and a
second ORC cycle 25 are provided, whereby a branch stream 28 is
branched off from low-temperature mass stream 1 downstream of first
ORC cycle 20, whereby a heat exchanger 24 is provided which has a
heat stream connection with a warm side 22 of a heat transformer
21, and thus heats a mass stream dm.sub.2/dt from a temperature
T.sub.2 to a temperature T.sub.3. A cold side 23 of heat
transformer 21 is thereby in turn, as in the previously described
embodiments, brought in contact with a working fluid of first ORC
cycle 20 downstream of a turbine. The second heat stream that is
extracted thereby is pumped by a heat transformer 21 to a
temperature above temperature T.sub.2, so that the mass stream
dm.sub.2/dT can be heated from temperature T.sub.2 to temperature
T.sub.3. This heated mass stream dm.sub.2/dt at a temperature
T.sub.3 is used for the operation of second ORC cycle 25. An
outflow 29 downstream of second ORC cycle 25 is fed
again--downstream of the first ORC cycle 20--into first
low-temperature mass stream 1.
[0059] Thereby, the outflow shows a temperature T4, which is larger
than T.sub.5, which is shown by low-temperature mass stream 1 at
the end. Moreover, temperature T.sub.3 is higher than temperature
T.sub.2.
[0060] By using the brine that was already presented as
low-temperature mass stream, the following values result in an
exemplified calculation. Thereby, a branch stream 28 is provided as
per partial delivery according to column 6. The second heat stream
which is extracted by heat transformer 21, also amounts to 20% of
the heat carried in the outflow from the turbine. This second heat
stream is given off again at a loss of 10% by the heat transformer
after being pumped to the higher pump level. The input temperature
and thus the initial temperature level is 120.degree. C., the exit
temperature T.sub.5 is 75.degree. C. Thereby, temperatures T.sub.2
and T.sub.4 are approximately identical to temperature T.sub.5.
TABLE-US-00002 Delivery Inlet Outlet Thermal Degree of Electrical
output Partial Electrical energy Increase in in Temp. in Temp. in
output in effectiveness in in KW effectiveness delivery in creation
in effectiveness l/s .degree. C. .degree. C. kW % 12% l/s KW % 50
120 75 7,760 12 931 9.50 177.01 19.0% 100 120 75 15,521 12 1,863
19.01 354.03 19.0% 150 120 75 23,281 12 2,794 28.51 531.04 19.0% 50
120 75 7,760 14 1,086 9.29 201.82 18.6% 100 120 75 15,521 14 2,173
18.58 403.64 18.6% 150 120 75 23,281 14 3,259 27.86 605.46 18.6% 50
120 75 7,760 16 1,242 9.07 225.29 18.1% 100 120 75 15,521 16 2,483
18.14 450.58 18.1% 150 120 75 23,281 16 3,725 27.22 675.87
18.1%
[0061] One possibility of separately streaming cycles is shown in
FIG. 6. Thereby, a first ORC cycle 20 and a second ORC cycle 25 are
only connected by a heat transformer 21, whereby the warm side 22
of the heat transformer supplies a heat exchanger 24 with a heat
stream. This heat stream is fed to a low-temperature mass stream 1,
which, via a downstream feedback 29a is again conveyed to an inlet
29b of ORC cycle 20 and thus is continuously circulated. The heat
stream supplied to heat transformer 21 is extracted downstream of
first ORC cycle 20 from outflow 29.
[0062] In a modified arrangement according to FIG. 7, heat
exchanger 24, contrary to the embodiment in FIG. 6, is not
downstream of first ORC cycle 20, but located in this first ORC
cycle 20. Heat exchanger 24 is thereby provided next to or instead
of a condenser.
[0063] In the variant shown in FIG. 8, no temperature increase of a
low-temperature mass stream 1 is undertaken instead, this
low-temperature mass stream 1 is increased by partial recirculation
30. For this purpose, a branch stream 28 is branched off from the
low-temperature mass stream 1 downstream of an ORC cycle 20, which
runs through a heat exchanger 24 that is fed by the warm side 22 of
heat transformer 21. A cold side 23 of heat transformer 21 is in
turn connected with ORC cycle 20 in the way it was previously
described. In heat exchanger 24, branch stream 28 dm.sub.3/dt is
heated from a temperature T.sub.2 to a pump temperature level
T.sub.1, which precisely corresponds to the initial temperature
level T.sub.1 of the low-temperature mass stream 1. In this manner,
a comparison to the originally present mass stream
dm.sub.1/dt+dm.sub.3/dt results. Simultaneously, the mass stream
flowing downstream is only dm.sub.1/dt.
[0064] The following values are in turn calculated for brine as a
low-temperature mass stream with an initial temperature level of
120.degree. C. as inlet temperature. The branch stream is set as
per the partial delivery shown in column 7. As pump temperature
level of the second heat stream, 160.degree. C. is provided,
whereby heat transformer 21 pumps 20% of the waste heat of the
turbine to pump temperature level with a degree of effectiveness of
90%.
TABLE-US-00003 Delivery Inlet Outlet Thermal KW Electrical Partial
Increase in in Temp. in Temp. in output in effectiveness
performance in delivery in effectiveness l/s .degree. C. .degree.
C. kW in % kW l/s % 50 120 75 7,760.45 12 931.25 9.50 19.0% 100 120
75 15,520.90 12 1,862.51 19.01 19.0% 150 120 75 23,281.34 12
2,793.76 28.51 19.0% 50 120 75 7,760.45 14 1,086.46 9.29 18.6% 100
120 75 15,520.90 14 2,172.93 18.58 18.6% 150 120 75 23,281.34 14
3,259.39 27.86 18.6% 50 120 75 7,760.45 16 1,241.67 9.07 18.1% 100
120 75 15,520.90 16 2,483.34 18.14 18.1% 150 120 75 23,281.34 16
3,725.02 27.22 18.1%
[0065] In the arrangement shown in FIG. 9, a working fluid 6 is
brought to a higher temperature level directly prior to a turbine 7
by a heat transformer 21. In detail, this is again an ORC cycle in
which a low-temperature mass stream 1 heats a vaporizer 5 at an
initial temperature level, whereby working fluid 6 is vaporized and
after an additional heating by a warm side 22 of heat transformer
21 is fed to turbine 7. There, an expansion takes place on account
of which work is performed that is transformed into electrical
energy by an electric generator 31. After exiting turbine 7,
expanded working fluid 6 is supplied to a heat exchanger 24, which
has a heat stream connection with a cold end 23 of heat transformer
21. As a result, from expanded working fluid 6 exiting the turbine
at an expansion temperature T.sub.5, a second heat stream is
extracted which is being pumped to a pump temperature level above
temperature T.sub.3 with the help of heat transformer 21. Thus,
temperature T.sub.4 prior to entering turbine 7 is above
temperature T.sub.1 of low-temperature mass stream 1 in the
vaporizer.
[0066] The following values are in turn calculated for brine as
low-temperature mass stream at an initial temperature level T.sub.1
of 120.degree. C. as inlet temperature. As pump temperature level
of the second heat stream, 160.degree. C. is provided, whereby
heat, transformer 21 pumps 20% of the waste heat of the turbine to
pump temperature level with a degree of effectiveness of 90%. The
outlet temperature T.sub.5 is 75.degree. C.
TABLE-US-00004 Delivery Inlet Oulet Thermal KW Electrical Output
Input Increase in in Temp. in Temp. in output in effectiveness
output in heat in heat in effectiveness l/s .degree. C. .degree. C.
kW in % kW kW kW % 50 120 75 7,760 12 931 1,366 1,093 14.1% 100 120
75 15,521 12 1,863 2,732 2,185 14.1% 150 120 75 23,281 12 2,794
4,098 3,278 14.1% 50 120 75 7,760.45 14 1,086.46 1,334.80 1,067.84
13.8% 100 120 75 15,520.90 14 2,172.93 2,669.59 2,135.68 13.8% 150
120 75 23,281.34 14 3,259.39 4,004.39 3,203.51 13.8% 50 120 75
7,760.45 16 1,241.67 1,303.76 1,043.00 13.4% 100 120 75 15,520.90
16 2,483.34 2,607.51 2,086.01 13.4% 150 120 75 23,281.34 16
3,725.02 3,911.27 3,129.01 13.4%
REFERENCE Numbers
[0067] 1 Low-temperature mass stream [0068] 2 deep well pump [0069]
3 geothermal source [0070] 4 first heat exchanger [0071] 5
vaporizer [0072] 6 working fluid [0073] 7 turbine [0074] 8
recuperator [0075] 9 condenser [0076] 10 fee pump [0077] 11
pre-heater [0078] 12 desorber [0079] 13 separator [0080] 14 steam
phase [0081] 15 watery phase [0082] 16 high temperature recuperator
[0083] 17 constrictor [0084] 18 low-temperature recuperator [0085]
19 absorber [0086] 20 first ORC cycle [0087] 21 first heat
transformer [0088] 22 warm side of heat transformer [0089] 23 cold
side of heat transformer [0090] 24 (first) heat exchanger [0091] 25
second ORC cycle [0092] 26 first heat transformer [0093] 27 second
heat transformer [0094] 28 branch stream [0095] 29 outflow [0096]
29a downstream recirculation [0097] 29b inlet (of ORC cycle) [0098]
30 partial recirculation [0099] 31 electric generator
* * * * *