U.S. patent application number 12/375980 was filed with the patent office on 2009-10-29 for process and device for using of low temperature heat for the production of electrical energy.
Invention is credited to Daniel Nestke, Siegfried Westmeier.
Application Number | 20090266075 12/375980 |
Document ID | / |
Family ID | 38521920 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090266075 |
Kind Code |
A1 |
Westmeier; Siegfried ; et
al. |
October 29, 2009 |
PROCESS AND DEVICE FOR USING OF LOW TEMPERATURE HEAT FOR THE
PRODUCTION OF ELECTRICAL ENERGY
Abstract
The invention relates to the using of low temperature heat for
the production of electrical energy by using of supercritical
carbon dioxide as working fluid. It included a process and a device
for process realizing with higher efficiency in relation to other
known processes and with a wide temperature working range. This is
related to a wider adjustability which allows an optimal operation
both in summer and in winter operation without technical or
constructional changes. The process is realizable without damages
to the environment and is realizable with low effort. The relative
emission of carbon dioxide is reduced in relation to other
processes. Low temperature heat from a given heat source (1) is
taken off by carbon dioxide at high supercritical pressure as heat
transfer and working fluid in the process. Then the heated fluid is
expanding in an expansion machine (2), which is connected with a
generator (3) for the production of electric power. In this process
the fluid will be cooled, then liquefied by using of a cold source
(4) and in liquid state compressed to the working pressure.
Inventors: |
Westmeier; Siegfried;
(Halle, DE) ; Nestke; Daniel; (Halle, DE) |
Correspondence
Address: |
MCGLEW & TUTTLE, PC
P.O. BOX 9227, SCARBOROUGH STATION
SCARBOROUGH
NY
10510-9227
US
|
Family ID: |
38521920 |
Appl. No.: |
12/375980 |
Filed: |
July 31, 2007 |
PCT Filed: |
July 31, 2007 |
PCT NO: |
PCT/DE2007/001351 |
371 Date: |
February 2, 2009 |
Current U.S.
Class: |
60/651 ;
60/641.1; 60/671 |
Current CPC
Class: |
F01K 25/103 20130101;
Y02E 20/14 20130101 |
Class at
Publication: |
60/651 ; 60/671;
60/641.1 |
International
Class: |
F01K 25/10 20060101
F01K025/10; F01K 27/00 20060101 F01K027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2006 |
DE |
10 2006 035 272.6 |
Claims
1. A process for using of low temperature heat for the production
of electric power, the process comprising: using supercritical
carbon dioxide as working fluid, in which high compressed
supercritical carbon dioxide as heat transfer fluid takes off low
temperature heat of a heat source and then is expanded in a
labor-producing expansion machine, which is connected with a
generator, is cooled in this process and liquefied by means of a
cold source, then increased of pressure by a pump for liquids to
the working pressure and stored in a high pressure interim
storage.
2. A process as claimed in claim 1, wherein the labor-producing
expansion is made into the range of vapor-liquid-equilibrium with a
partial condensation of carbon dioxide and the vapor-liquid-mixture
is liquefied totally by means of a cold source, then increased of
pressure by a pump for liquids to the working pressure and stored
in a high pressure interim storage.
3. A process as claimed in claim 1, wherein as interim storages are
used salt caverns in big depth.
4. A process as claimed in claim 1, wherein the waste heat of a
power station is used as heat source.
5. A process as claimed in claim 1, wherein the waste heat of
motors is used as heat source.
6. A process as claimed in claim 1, wherein the waste heat of
machines and plants is used as heat source.
7. A process as claimed in claim 1, wherein geothermal energy is
used as heat source.
8. A process as claimed in claim 1, wherein solar energy is used as
heat source.
9. A process as claimed in claim 1, wherein the geothermal
potential in depth of 5 to 30 meters is used as cold source for the
liquefaction of the carbon dioxide at last partially.
10. A process as claimed in claim 1, wherein the ambient air or
substances which are tempered by the ambient air are used as cold
source for the liquefaction of the carbon dioxide at last
partially.
11. A process as claimed in claim 1, wherein deep water of seas,
rivers or oceans or substances which are tempered by deep water are
used as cold source for the liquefaction of the carbon dioxide at
last partially.
12. A process as claimed in claim 1, wherein the cold energy of the
expansion of compressed air or natural gas or substances which are
tempered by the cold energy of the expansion are used as cold
source for the liquefaction of the carbon dioxide at last
partially.
13. A process as claimed in claim 1, wherein the labor-producing
two-stage expansion is characterized by an expansion into the
two-phase region in the first step by separating of the gas part
and using of a liquid part of this stream for cooling of the whole
stream for the expansion, in this process will be the stream heated
and then in a second step expanded to lower pressures, then used
for the cooling and liquefying of the first gas stream and after
them compressed and assembled with the liquefied first gas part and
in the liquid form compressed to the working pressure.
14. A process as claimed in claim 1, wherein the salt caverns in
the process are used both storages for carbon dioxide in the
supercritical high pressure state and geothermic heat sources and
heat exchanger, through which the potential of the carbon dioxide
emission is lowered additional
15. A process as claimed in claim 1, wherein the liquefaction takes
place in the earth near the surface of the earth and the depth
storage in more than 400 meters because the high pressure of the
carbon dioxide of 10 MPa at least by safety reasons and the high
static pressure the costs of the compression reduces.
16. A process as claimed in claim 1, wherein the process is
operating in joint with a peak load power station of natural gas
basis and operating discontinuously, through which the excess
energy is used to load natural gas, compressed air and carbon
dioxide in underground buffers under high pressure and, when
needed, to take off air and natural gas discontinuously and the
storage for carbon dioxide to use both as buffer storage and as
geothermal heat source for the working fluid.
17. A device realizing the process as claimed in claim 1, wherein
is used at least a given heat source, a heat exchanger with
liquefying function, a medium for the heat transfer, an expansion
machine, a generator which is connected with the expansion machine,
a pump for the compression of the liquid carbon dioxide, a buffer
for the storage of the liquid working fluid, control devices and
valves.
Description
[0001] The invention relates to the using of low temperature heat
for the production of electrical energy by using of supercritical
carbon dioxide as working fluid.
FIELD AND BACKGROUND OF THE INVENTION
[0002] There known two methods for the using of low temperature
heat from burning and reaction processes as well as from solar
thermal and geothermic processes essentially: [0003] 1. In the OCR
(Organic-Rankine-Cycle)-process the heat is taking away from the
process medium by a heat exchanger and using for the production of
steam. Refrigerants, freezing or low boiling substances as e.g.
pentane are used in this process, vaporized and labor-producing
expanded due a expansion turbine connecting with a generator. The
expanded vapor is used for preheating and then condensed. The heat
of condensation will be delivered into the surrounding. The
efficiency is estimated by the difference between the temperature
of condensation (temperature of the surrounding) and the reachable
temperature of vaporization from 300 K to 625 K depending of the
used working fluid. The heat transfer is realized by a silicon oil
cycle normally. A changed version of the OCR-process for low power
is known as edc-process. The edc-process is working with
temperatures of condensation from nearly 248 K to 350 K and is
using special constructed turbines. The efficiency of the
ORC-process is reaching at a temperatures level of 100.degree. C.
nearly 6.5% and at a temperature level of 200.degree. C. nearly
13-14%. [0004] 2. In the Kalina-process the heat is taking away
from the process medium by a saturated ammonia-water mixture, in
which ammonia is desorbed. The ammonia is labor-producing expanded
due an expansion turbine which is connected with a generator. After
them the cold ammonia is reabsorbed in the ammonia-water mixture.
The efficiency of the Kalinin process is with 18% (brutto) a little
higher than the ORC-process, according to the literature.
Profitable is the simpler construction of the plant as well as the
significant wider range of temperatures of the working fluid.
Disadvantageous are the problems with the construction material by
using of the aggressive ammonia-water mixture which is leading to a
lowering of the cycling time of the little proved plant. Another
disadvantage is the danger of possible emissions of the high-toxic
and environmentally dangerous ammonia at possible leakages or
disturbances.
Task Invention
[0005] Task invention is developing a process for using low
temperature heat for the production of electric power with a higher
efficiency and a broader working range as known processes and a
simple device for the realization of this process with a low
material effort and with a low environmental hazard.
[0006] The wider working range and wider adjustment range are
loading to optimal processing in relation to local conditions and
climate, e.g. summer or winter operation without constructive
changes and minimization of the production of carbon dioxide.
[0007] According to the invention the task is solved by using
high-pressured supercritical carbon dioxide as heat transfer
medium, which takes off low temperature heat from a heat source,
after them is expanded labor-producing in an expansion turbine,
which is connected with a generator, as a result is cooled, then by
using of a cold source is liquefied and in liquid state is
pressured to the working pressure.
[0008] The process implied at least an external heat source (1), an
expansion machine (2) connected with a generator (3), a heat
exchanger with liquefier (4) and a pump (5) for compressing liquid
carbon dioxide to supercritical pressures and a carbon dioxide
storage (6) as soon as control devices and valves belonging to it,
characterized in that carbon dioxide is used as the heat transfer
medium and working fluid. The carbon dioxide will be liquefied at
low temperatures, compressed in the liquid state to high
supercritical pressures, at these pressures buffered for heat
exchange process, taken off the thermal energy at this pressure
from a heat source (1) and labor-producing expanded due an
expansion machine (2) with an connected generator (3). In the
expanding process carbon dioxide will be cooled and the final
temperature will be controlled by the wanted pressure for the
liquefaction. After them the carbon dioxide will be liquefied at
this pressure by heat exchange a cold source due the discharge of
the heat of condensation. The compression of the liquid carbon
dioxide by a liquid pump (5) needs relatively few energy and a
possible increase of temperature is acting in the increase of the
efficiency.
[0009] In relation to the use of steam there are many advantages.
First an expensive water purification plant will be not needed and
then the relatively high losses in the waste heat boiler are
avoided, which are resulted by the big temperature differences
between the cooling-down curve of the exhaust gas and the
warming-up curve of the steam through the vaporization of the
water. The often used two-pressure and three-pressure cycles for a
better adaption are causing a higher effort in material and
control.
[0010] These difficulties will be avoided by the alternative use of
the supercritical region for the heat transfer. The region is very
interest too because their easy thermodynamic terms for the heat
exchange by using of low temperature heat. That is caused by
relatively high values of the heat capacity, low values of the
viscosity and a heat conductivity comparable to steam.
[0011] The thermodynamic usable range of state is limited to low
temperatures by the triple point of carbon dioxide at temperature
of nearly 217 K and a pressure of 0.55 MPa. To higher temperatures
and pressures there are no limitations for thermodynamic reasons,
but for the practical use in relation to the material of the
expansion machines and the heat exchangers.
[0012] An additional advantage to the OCR-process is given by the
fact that the heat transfer and working fluid are not differently,
carbon dioxide is used for both tasks. The fluid is working in a
closed circuit and an additional heat exchanger is not needed.
[0013] Other advantages of this medium are given by its relatively
low danger potential for people and environment and its high
availability.
[0014] Besides them the storage of bigger amounts of carbon dioxide
under control and its use as working fluid relieves the atmosphere
and the environment and gives credits by the carbon dioxide trade.
Other advantages are given by a higher efficiency of the process
and in the possibility to combine the process with other heat and
cold potentials increasing real efficiency. That is possible by
using cold potentials in the earth near the surface of the earth in
low depths, as well as by using cold potentials, which are created
by expansion processes from other gases as natural gas and air and
are delivering wanted low temperatures.
[0015] The process will be used as a combination of a gas power
station with natural heat and cold potentials. Big amounts of
carbon dioxide will be stored in the buffers of carbon dioxide and
used immediately in a discontinuous working and by expansion for
the production of electrical power too without significant start-up
and shut-down periods.
[0016] The start of development of the storage for carbon dioxide
is made by winning carbon dioxide from the exhaust air by
condensation of water for removing (drying) first and after then
the carbon dioxide by compression over 5 MPa, cooling to a
temperature of 281 to 283 K and condensing. Cooling is made by the
earth temperature in 3 to 30 meters depth. The liquid carbon
dioxide is collected and given through the buffer storage into the
underground storage. A part of this can be used for substituting
losses of the circuit in the liquid range. For commissioning the
plant the carbon dioxide circuit must be filled with carbon dioxide
from other sources. In the winter time can be used the surrounding
air temperature for cooling when the temperature is below 278 K.
Then can be is used a lower pressure for the liquefaction,
depending from the real air temperature.
EXAMPLES OF APPLICATION
[0017] Further advantages are given by the description of examples
of application of the invention as well as the connected picture
and table.
[0018] The fundamental principle of the application of the process
and the device for using of the waste energy of an energy
generation plant by using the earth as cooling source for
condensation of the working fluid carbon dioxide is shown in the
picture. Three different heat potentials at 363 K, 373 K und 623 K
are used exemplary as heat sources at the working pressure at 15
MPa in the examples I to III. As expansion machine (2) is used an
expansion turbine. The earth heat potential in the depths of 8 to
30 meters is used as cold source (4) for the condensation of the
working fluid carbon dioxide which was expanded to 4.5 MPa. A
pressure chamber (6) will used as a temporary storage. The pipes
for the carbon dioxide circuit are the lines 7 to 11 according to
the picture. The calculation of the examples was made with the
program EBSILON Professional. In example IV of the second part of
the table is calculated the situation of example II (heat source at
373 K) with a lower air temperature of 271 K, which is
characteristic for the winter, as cold source (4) and their using
by air coolers. For this it is given a lower turbine output
pressure of 3.7 MPa. By using of the broader ranges of temperature
and pressure the efficiency of energy generation plant is 1.3%
better than in example II. This result is important especially of
regions with low temperatures as well as for using of geothermic
energy and power stations.
[0019] The low temperatures are causing a relatively low efficiency
but in all cases the efficiency of this process was more than 2%
higher than in comparable processes. In a co-generation the heat
source (1) of the process was the waste energy. In the examples I
to IV the waste energy is used at the given temperature levels 363
K, 373 K, and 623 K and should be used energetically. The fluid
carbon dioxide is streaming from the underground buffer (6) with a
pressure of 15 MPa and temperatures of 293.5 K (examples I to III)
and 284.5 K (example IV) through the heat exchanger (1), heated at
the given temperatures to 363 K (example I), 373 K (example II and
IV), and 623 K (example III), streaming through a control valve to
an expansion turbine (2), expanding labor-producing from 15 MPa to
4.5 MPa (examples I to III) or rather 3.7 MPa (example IV) and
driving on this way a with the turbine connected generator (3). The
carbon dioxide was expanded into an underground pipe network as the
cold source (4) to a temperature of 281 K in the examples I to III.
The carbon dioxide is liquefied at this temperature because the
long retention period of the carbon dioxide in the pipe network. An
air cooler was used as the cold source (4) at 271 K in the example
IV and the carbon dioxide was expanded to a pressure of 3.7 MPa.
The liquid carbon dioxide is going through a heat isolated pipe (9)
to the liquid pump (5), compressed to a pressure of 15 MPa, and
stored in the buffer (6). The work for the compression of the
liquid carbon dioxide is lower than 30% of the produced energy. The
netto-efficiency of the process is given in the table. The
efficiency is increased at higher heat potentials and lower cold
sources are usable, e.g. by using of the expansion cold of natural
gas and can reach at 373 K efficiencies of nearly 25%.
TABLE-US-00001 TABLE Fluid Temperature Pressure Power KW Elt Elt
Netto flow Unit K MPa Therm. Electr. Brutto Netto Efficiency
Example 7 363 15 I 2, 3 328 8 283 4.5 4 -1809 9 283 4.5 5 -119 10,
11 293.5 15 1 2018 328 209 10.4% 7 373 15 II 2, 3 450 8 283 4.5 4
-1902 9 283 4.5 5 -119 10, 11 293.5 15 1 2243 450 331 14.4% 7 623
15 III 2, 3 1230 8 493 4.5 4 -4486 9 283 4.5 5 -119 10, 11 293.5 15
1 5598 1230 1112 19.9% 7 373 15 IV 2, 3 514 air 8 275.5 3,7 cooling
4 -2049 9 271.5 3.7 5 -121 10, 11 284.5 15 1 2442 514 393 16.1%
* * * * *