U.S. patent application number 13/674176 was filed with the patent office on 2013-05-23 for thermal energy storage and recovery system comprising a storage arrangement and a charging/discharging arrangement being connected via a heat exchanger.
The applicant listed for this patent is TILL BARMEIER, GILDAS JEAN COURTET, AIDAN CRONIN, HANS LAURBERG, JESPER ELLIOT PETERSEN, HENRIK STIESDAL. Invention is credited to TILL BARMEIER, GILDAS JEAN COURTET, AIDAN CRONIN, HANS LAURBERG, JESPER ELLIOT PETERSEN, HENRIK STIESDAL.
Application Number | 20130125546 13/674176 |
Document ID | / |
Family ID | 45370424 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130125546 |
Kind Code |
A1 |
BARMEIER; TILL ; et
al. |
May 23, 2013 |
THERMAL ENERGY STORAGE AND RECOVERY SYSTEM COMPRISING A STORAGE
ARRANGEMENT AND A CHARGING/DISCHARGING ARRANGEMENT BEING CONNECTED
VIA A HEAT EXCHANGER
Abstract
A thermal energy storage and recovery system including a storage
arrangement having a thermal energy storage device for temporarily
storing thermal energy, a charging/discharging arrangement having a
fluid energy machine for exchanging mechanical work with a working
fluid cycling through the charging/discharging arrangement, and a
heat exchanger which is arranged between the storage arrangement
and the charging/discharging arrangement and which
thermodynamically couples a heat transfer fluid cycling through the
storage arrangement with the working fluid is provided. The storage
arrangement is configured in such a manner that the heat transfer
fluid is under a first pressure and the charging/discharging
arrangement is configured in such a manner that the working fluid
is at least partially under a second pressure, wherein the second
pressure is higher than the first pressure.
Inventors: |
BARMEIER; TILL; (Herning,
DK) ; COURTET; GILDAS JEAN; (Herning, DK) ;
CRONIN; AIDAN; (Holstebro, DK) ; LAURBERG; HANS;
(Arhus C, DK) ; PETERSEN; JESPER ELLIOT; (Olgod,
DK) ; STIESDAL; HENRIK; (Odense C, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BARMEIER; TILL
COURTET; GILDAS JEAN
CRONIN; AIDAN
LAURBERG; HANS
PETERSEN; JESPER ELLIOT
STIESDAL; HENRIK |
Herning
Herning
Holstebro
Arhus C
Olgod
Odense C |
|
DK
DK
DK
DK
DK
DK |
|
|
Family ID: |
45370424 |
Appl. No.: |
13/674176 |
Filed: |
November 12, 2012 |
Current U.S.
Class: |
60/643 |
Current CPC
Class: |
F01K 13/006 20130101;
F01K 3/00 20130101; Y02E 20/14 20130101 |
Class at
Publication: |
60/643 |
International
Class: |
F01K 13/00 20060101
F01K013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2011 |
EP |
11189939.9 |
Claims
1. A thermal energy storage and recovery system comprising a
storage arrangement having a thermal energy storage device for
temporarily storing thermal energy; a charging/discharging
arrangement having a fluid energy machine for exchanging mechanical
work with a working fluid cycling through the charging/discharging
arrangement; and a heat exchanger arranged between the storage
arrangement and the charging/discharging arrangement and
thermodynamically couples a heat transfer fluid cycling through the
storage arrangement with the working fluid, wherein the storage
arrangement is configured in such a manner that the heat transfer
fluid is under a first pressure, wherein the charging/discharging
arrangement is configured in such a manner that the working fluid
is under a second pressure, and wherein the second pressure is
higher than the first pressure.
2. The thermal energy storage and recovery system as claimed in
claim 1, wherein the first pressure is an ambient pressure of the
thermal energy storage and recovery system.
3. The thermal energy storage and recovery system as claimed in
claim 1, wherein the storage arrangement comprises means for
driving a flow of heat transfer fluid through the storage
arrangement.
4. The thermal energy storage and recovery system as claimed in
claim 1, wherein in a first operational mode, in which the thermal
energy storage device receives thermal energy from the heat
transfer fluid, the storage arrangement is configured for
circulating the heat transfer fluid in a first direction, and
wherein in a second operational mode, in which the thermal energy
storage device transfers thermal energy to the heat transfer fluid,
the storage arrangement is configured for circulating the heat
transfer fluid in a second direction being opposite to the first
direction.
5. The thermal energy storage and recovery system as claimed in
claim 4, wherein in the first operational mode the
charging/discharging arrangement is configured for circulating the
working fluid in a further first direction, and wherein in the
second operational mode the charging/discharging arrangement is
configured for circulating the working fluid in a further second
direction being opposite to the first direction.
6. The thermal energy storage and recovery system as claimed in
claim 4, wherein the charging/discharging arrangement further
comprises a further fluid energy machine, and wherein with respect
to a flow direction of the working fluid the fluid energy machine
is located upstream of the heat exchanger and the further fluid
energy machine is located downstream of the heat exchanger.
7. The thermal energy storage and recovery system as claimed in
claim 6, wherein the fluid energy machine and the further fluid
energy machine are configured such that in the first operational
mode, the fluid energy machine generates thermal energy for the
heat exchanger and the further fluid energy machine receives
thermal energy from the heat exchanger, whereby the generated
thermal energy is larger than the received thermal energy, and
wherein the fluid energy machine and the further fluid energy
machine are configured such that in the second operational mode,
the fluid energy machine receives thermal energy from the heat
exchanger and the further fluid energy machine generates thermal
energy for the heat exchanger, whereby the received thermal energy
is larger than the generated thermal energy.
8. The thermal energy storage and recovery system as claimed in
claim 7, wherein the charging/discharging arrangement further
comprises a mechanical energy transmission arrangement, which is
connected between the fluid energy machine and the further fluid
energy machine, and wherein the mechanical energy transmission
arrangement is configured for directly exchanging mechanical energy
between the fluid energy machine and the further fluid energy
machine.
9. The thermal energy storage and recovery system as claimed in
claim 8, wherein in the first operational mode the further fluid
energy machine is configured for producing cold when expanding the
working fluid, and wherein the produced cold is useable for cooling
purposes.
10. The thermal energy storage and recovery system as claimed in
claim 1, wherein the charging/discharging arrangement is configured
in such a manner that the working fluid when circulating through
the charging/discharging arrangement undergoes a change of its
state of aggregation.
11. The thermal energy storage and recovery system as claimed in
claim 10, wherein the charging/discharging arrangement is
configured in such a manner that in the first operational mode the
charging/discharging arrangement is configured for acting as a heat
pump and in the second operational mode the working fluid within
the charging/discharging arrangement undergoes a steam cycle.
12. The thermal energy storage and recovery system as claimed in
claim 1, wherein the thermal energy storage device comprises a
container having a first fluid terminal for inserting the heat
transfer fluid into the interior of the container and a second
fluid terminal for extracting the heat transfer medium from the
interior of the container and a heat storage material accommodated
within the container, and wherein the heat storage material is
spatially arranged within the container in such a manner that heat
transfer fluid flowing between the first fluid terminal and the
second fluid terminal gets into direct physical contact with the
accommodated heat storage material.
13. The thermal energy storage and recovery system as claimed in
claim 12, wherein the heat storage material comprises rock material
and/or sand material.
14. The thermal energy storage and recovery system as claimed in
claim 13, wherein the heat storage material comprises concrete.
15. The thermal energy storage and recovery system as claimed in
claim 1, wherein the heat transfer fluid and/or the working fluid
is a gas.
16. The thermal energy storage and recovery system as claimed in
claim 15, wherein the working gas is air.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority of European Patent Office
application No. 11189939.9 EP filed Nov. 21, 2011. All of the
applications are incorporated by reference herein in their
entirety.
FIELD OF INVENTION
[0002] The field of invention relates to temporarily storing and
recovering thermal energy. A thermal energy storage and recovery
system comprising a storage arrangement having a thermal energy
storage device for temporarily storing thermal energy and a
charging/discharging arrangement for (a) charging, in a first
operational mode, the thermal energy storage device and for (b)
discharging, in a second operational mode, the thermal energy
storage device is provided.
ART BACKGROUND
[0003] The production of electric power from various types of
alternative energy sources such as for instance wind turbines,
solar power plants and wave energy plants is not continuous. The
production may be dependent on environmental parameters such as for
instance wind speed (for wind turbines), sunshine intensity (for
solar power plant) and wave height and wave direction (for wave
energy plants). There is very often little or no correlation
between the energy production and the energy demand.
[0004] One known approach to solve the problem of uncorrelated
electric power production and electric power demand is to
temporally store energy, which has been produced but which has not
been demanded, and to release the stored energy at times at which
there is a high demand. In the past there have been suggested many
different methods to temporarily store energy. Suggested methods
are for instance (a) mechanical energy storage methods e.g. pumped
hydro storage, compressed air storage and flywheels, (b) chemical
energy storage methods e.g. electrochemical batteries and organic
molecular storage, (c) magnetic energy storage, and (d) thermal
energy storage e.g. within water or molten salts.
[0005] The document US 2010/0301614 A1 discloses an installation
for storing and returning electrical energy. The disclosed
installation comprises a first enclosure and a second enclosure
each containing a gas and porous refractory materials suitable for
transferring heat by a contact between said porous refractory
materials and a gas flowing through the respective enclosure.
Thereby, the porous refractory material represents a heat storage
material and the gas represents a heat transfer medium. The
disclosed installation further comprises a compressor and an
expander for the gas flowing in pipes between each of the ends of
an enclosure connected to an end of the other enclosure. By guiding
compressed gas through the porous refractory materials an efficient
heat transfer between the gas and the refractory materials can be
realized.
[0006] With respect to the physical structure and the dimension of
the enclosure accommodating the porous refractory material it is
clear that the necessary wall thickness of the enclosure is
associated with the maximum pressure of the gas. Further, since the
storage method has the capacity to store very large quantities of
energy the installation for storing and returning electrical energy
would use an enclosure having very large dimensions. It is
therefore economically advantageous to seek to minimize the
internal pressure level of the gas acting as heat transfer medium
or heat transfer fluid. One simple way of reducing the internal
pressure achieving this result would be simply to limit the
compression ratio of the gas. However, within the enclosure there
will still be a higher pressure than usual ambient pressure.
Therefore, the enclosure will still need to be large and pressure
tight and need to comply with relevant safety provisions. However,
when the size of the enclosure goes up the volume of gas needed to
fill out the enclosure volume goes up correspondingly. Thus, a
large amount of gas is not effectively used.
[0007] There may be a need for improving the efficiency of a
temporal storage of thermal energy within a thermal energy storage
and recovery device of a thermal energy storage and recovery
system.
SUMMARY OF THE INVENTION
[0008] This need may be met by the subject matter according to the
independent claims Advantageous embodiments of the present
invention are described by the dependent claims.
[0009] According to a first aspect, there is provided a thermal
energy storage and recovery system comprising (a) a storage
arrangement having a thermal energy storage device for temporarily
storing thermal energy, (b) a charging/discharging arrangement
having a fluid energy machine for exchanging mechanical work with a
working fluid cycling through the charging/discharging arrangement,
and (c) a heat exchanger which is arranged between the storage
arrangement and the charging/discharging arrangement and which
thermodynamically couples a heat transfer fluid cycling through the
storage arrangement with the working fluid. The storage arrangement
is configured in such a manner that the heat transfer fluid is
under a first pressure and the charging/discharging arrangement is
configured in such a manner that the working fluid is under a
second pressure, wherein the second pressure is higher than the
first pressure.
[0010] The described thermal energy storage and recovery system is
based on the idea that when using different pressures for the heat
transfer fluid being assigned to the storage arrangement and for
the working fluid being assigned to the charging/discharging
arrangement with respect to a thermodynamic efficiency a highly
efficient temporal heat storage and heat recovery can be
realized.
[0011] The heat exchanger may be connected to the thermal energy
storage device by means of pipes, in particular insulated steel
pipes. Alternatively, the heat exchanger can be located inside the
thermal energy storage device in such a way that a possible leaking
of heat transfer fluid from the heat exchanger stays inside the
thermal energy storage device.
[0012] In this document the term "charging/discharging arrangement"
may denominate any thermodynamic arrangement, which is capable of
(a) charging the storage arrangement respectively the thermal
energy storage device, (b) discharging the storage arrangement
respectively the thermal energy storage device or (c) charging and
discharging the storage arrangement respectively the thermal energy
storage device.
[0013] In this document the term "fluid energy machine" may be used
for any thermodynamic arrangement, which is capable of exchanging
mechanical work or mechanical energy between the working fluid and
the exterior of the charging/discharging arrangement.
[0014] A fluid energy machine as defined above either (a) transfers
mechanical work or mechanical energy from outside to the working
fluid or (b) extracts mechanical work or mechanical energy from the
working fluid and delivers this extracted mechanical work or energy
to the outside (e.g. a rotating shaft of an electric
generator).
[0015] It is mentioned that the working fluid may carry different
types of energy. In particular, the working fluid may carry a
mixture between thermal energy and mechanic energy, wherein the
latter is stored in a compressible fluid when the fluid is under
pressure. Further, also a kinetic energy may be associated with the
working fluid when the working fluid flows with a certain velocity
through corresponding guide channels.
[0016] The first pressure of the heat transfer fluid is at least
approximately constant within the whole storage arrangement. This
does not mean that there are not allowed any minor pressure
variations which can be caused e.g. by fluid mechanic effects
and/or by any means which are responsible for cycling the heat
transfer fluid through the storage arrangement. Specifically, of
course a pressure drop is needed for establishing a flow of the
heat transfer fluid through the storage arrangement. For instance
the pressure may be 1.4 bar at an inlet of the storage arrangement
and 1 bar at an outlet of the storage arrangement in order to
guarantee a necessary flow through for instance a storage
arrangement being filled with a rock material. In this respect
"approximately constant within the whole storage arrangement" means
that within the storage arrangement there is provided no compressor
or expander which intentionally changes the pressure within a
thermodynamic process.
[0017] According to an embodiment, the first pressure is an ambient
pressure of the thermal energy storage and recovery system. This
may provide the advantage that there is no need for using a
pressurized storage vessel for realizing the thermal energy storage
device. As a consequence, the thermal energy storage device can be
realized by means of an easy construction, wherein no sealing means
are required in order to ensure an efficient operation of the whole
thermal energy storage and recovery system.
[0018] In this respect it is mentioned that for the operation of
the storage arrangement at ambient pressure the provision of the
heat exchanger may be essential, which allows for a thermodynamic
coupling but for a spatial separation between the heat transfer
fluid and the working fluid. This way, it is possible to operate
the storage arrangement and in particular the thermal energy
storage device at ambient pressure, and it is hereby possible to
build a large high temperature thermal energy storage device for
several hundred of MWh or even GWh at a much lower cost than known
solutions.
[0019] According to a further embodiment, the storage arrangement
comprises means for driving a flow of heat transfer fluid through
the storage arrangement. The described means for driving or for
cycling the heat transfer fluid may be e.g. at least one fan which,
without causing relevant pressure variations within the storage
arrangement, can move the heat transfer fluid through the storage
arrangement.
[0020] The storage arrangement comprises two fans, wherein with
respect to a flow direction of the heat transfer fluid within the
storage arrangement one fan is located upstream of the thermal
energy storage device and another fan is located downstream of the
thermal energy storage device. Thereby, a heat transfer flow with
only very little pressure variations can be realized.
[0021] According to a further embodiment (a) in a first operational
mode, in which the thermal energy storage device receives thermal
energy from the heat transfer fluid, the storage arrangement is
configured for circulating the heat transfer fluid in a first
direction, and (b) in a second operational mode, in which the
thermal energy storage device transfers thermal energy to the heat
transfer fluid, the storage arrangement is configured for
circulating the heat transfer fluid in a second direction being
opposite to the first direction. Thereby, a switching between the
two fundamental different operational modes of the thermal energy
storage and recovery system can be realized simply by switching the
direction of the above mentioned means for driving a flow of the
heat transfer fluid.
[0022] According to a further embodiment (a) in the first
operational mode, the charging/discharging arrangement is
configured for circulating the working fluid in a further first
direction, and (b) in the second operational mode the
charging/discharging arrangement is configured for circulating the
working fluid in a further second direction being opposite to the
first direction. This may provide the advantage that also the
charging/discharging arrangement can be easily switched between the
two operational modes simply by reversing the flow direction of the
working fluid.
[0023] According to a further embodiment, the charging/discharging
arrangement further comprises a further fluid energy machine,
wherein with respect to a flow direction of the working fluid the
fluid energy machine is located upstream of the heat exchanger and
the further fluid energy machine is located downstream of the heat
exchanger. This may provide the advantage that the thermodynamic
efficiency of the charging/discharging arrangement can be increased
significantly.
[0024] According to a further embodiment, the fluid energy machine
and the further fluid energy machine are configured such that (a)
in the first operational mode the fluid energy machine generates
thermal energy for the heat exchanger and the further fluid energy
machine receives thermal energy from the heat exchanger, wherein
the generated thermal energy is larger than the received thermal
energy, and (b) in the second operational mode the fluid energy
machine receives thermal energy from the heat exchanger and the
further fluid energy machine generates thermal energy for the heat
exchanger, wherein the received thermal energy is larger than the
generated thermal energy.
[0025] Using two separate fluid energy machines being assigned to
the charging/discharging arrangement may provide the advantage that
a highly efficient temporal heat storage and heat recovery can be
realized.
[0026] In the first operational mode (a), the fluid energy machine
is configured to act as a compressor and the further fluid energy
machine is configured to act as an expander and/or (b) in the
second operational mode the fluid energy machine is configured to
act as an expander and the further fluid energy machine is
configured to act as a compressor.
[0027] The described fluid energy machine when acting as a
compressor may be configured for an adiabatic compression of the
working fluid in order to efficiently compress the working fluid
before it is forwarded to the heat exchanger. During the first
operational mode the compression process may be optimized in order
to achieve an efficient heating up of the working fluid.
Correspondingly, the described further fluid energy machine when
acting as an expander may be configured for an adiabatic expansion
of the working fluid after having passed the heat exchanger.
[0028] According to a further embodiment, the charging/discharging
arrangement further comprises a mechanical energy transmission
arrangement, which is connected between the fluid energy machine
and the further fluid energy machine, wherein the mechanical energy
transmission arrangement is configured for directly exchanging
mechanical energy between the fluid energy machine and the further
fluid energy machine. This may provide the advantage that a highly
efficient energy storage and recovery process may be realized
because mechanical energy being generated at one of the two fluid
energy machines can be directly transferred, i.e. without any
(inefficient) energy conversion processes, to the other one of the
two fluid energy machines.
[0029] Specifically, in the first operational mode after having fed
compressed and hot working fluid into the heat exchanger a at least
partially cooled down compressed working fluid which is returned
from the heat exchanger can be used by the further fluid energy
machine. Thereby, the energy and in particular the mechanical
energy being left in the returned and cooled down compressed
working fluid can be extracted with the further fluid energy
machine and can be used to help driving the fluid energy machine
acting as a compressor for the working fluid being supposed to be
compressed and then being fed to the heat exchanger.
[0030] Correspondingly, in the second operational mode the fluid
energy machine which may act as a turbine is driven by the working
fluid which has been compressed before by the further fluid energy
machine and which has been heated up by the heat exchanger.
Thereby, not all the mechanic energy being generated by the fluid
energy machine acting as a turbine is used for external purposes.
Rather a portion of the generated mechanic energy is directly (i.e.
without any inefficient energy conversion) transferred to the
further fluid energy machine acting as a compressor. This
transferred mechanical energy can then be used to help driving the
compressor for the working fluid which is supposed to be fed to the
heat exchanger in order to be heated up.
[0031] The mechanical energy transmission arrangement may be
realized e.g. by means of a rotatable shaft, which connects the two
fluid energy machines with each other.
[0032] According to a further embodiment, in the first operational
mode the further fluid energy machine is configured for producing
cold when expanding the working fluid, wherein the produced cold is
useable for cooling purposes.
[0033] The cooling purposes may be for instance the operation of a
condenser, a cold storage and/or a district cooling system.
Expanding the working fluid is carried out under at least
approximately adiabatic conditions which makes the described
production of cold very effective.
[0034] According to a further embodiment, the charging/discharging
arrangement is configured in such a manner that the working fluid
when circulating through the charging/discharging arrangement
undergoes a change of its state of aggregation. Thereby, the state
of aggregation of the working fluid may change between the liquid
and the gaseous state. This may allow to increase the efficiency
for a temporal heat storage and heat recovery process being carried
out by the described thermal energy storage and recovery
system.
[0035] According to a further embodiment, the charging/discharging
arrangement is configured in such a manner that (a) in the first
operational mode the charging/discharging arrangement is configured
for acting as a heat pump and (b) in the second operational mode
the working fluid within the charging/discharging arrangement
undergoes a steam cycle. This may provide the advantage that the
thermodynamic efficiency for a temporal heat storage and heat
recovery process being carried out by the described thermal energy
storage and recovery system can be increased even further.
[0036] According to a further embodiment, the thermal energy
storage device comprises (a) a container having a first fluid
terminal for inserting the heat transfer fluid into the interior of
the container and a second fluid terminal for extracting the heat
transfer medium from the interior of the container and (b) a heat
storage material being accommodated within the container. Thereby,
the heat storage material is spatially arranged within the
container in such a manner that heat transfer fluid flowing between
the first fluid terminal and the second fluid terminal gets into
direct physical contact with the accommodated heat storage
material. This may provide the advantage that there is no need for
special pipes, in particular for steel pipes, which are used for
guiding the heat transfer fluid. Further, by ensuring a direct
physical contact between the heat transfer fluid and the heat
storage material a highly efficient thermal energy transfer between
the heat transfer fluid and the heat storage material and vice
versa can be realized.
[0037] The walls of the container may be provided with an
insulation layer comprising an insulation material that is able to
withstand temperatures above 550.degree. Celsius. The insulation
layer, which may have a thickness of between 0.5 two 2 meters, may
be arranged at the inner side and/or at the outer side of the
container walls. The insulation layer is arranged exclusively at
the inner side such that the insulation material is protected by
the container walls. The container walls may be made e.g. from
concrete.
[0038] According to a further embodiment, the heat storage material
comprises rock material and/or sand material. This may provide the
advantage that a low cost and widely available material can be used
for building up the thermal energy storage device. Thereby, local
labor and locally available heat storage material can be used such
that there is no need to transport a suitable heat storage material
over a long distance. This may be in particular advantageous if a
thermal energy storage device with a high heat storage capability
is built up.
[0039] It is mentioned that in many applications rocks may be
preferred since rocks are inexpensive and act both as heat transfer
surface and as a heat storage medium. This means that no special
heat transfer equipment is needed within in the container of the
thermal energy storage device. Due to a very large heat transfer
area the amount of heat transfer between heat transfer medium,
which may be e.g. air, and the rocks can be quite high. Further,
the heat conductance between the rocks is relatively low due to the
small area of contact between different rocks. As a consequence the
heat loss from the thermal energy storage device is relatively low
and the temperature gradient can be kept steep within the container
of the thermal energy storage device.
[0040] However, the described thermal energy storage and recovery
system makes it also possible to use sand as heat storage material.
Again, it is not necessary to use pipes for guiding the heat
transfer medium through the interior of the container. Sand may be
spatially supported by profiles which generated channels for
guiding the heat transfer medium, which may be again air, through
the interior of the container of the thermal energy storage device.
The profiles may be metal plates, e.g. made from aluminum, steel or
any other stable material, which is capable of withstanding high
temperatures and/or spatial and/or temporal temperature changes.
The profiles may be profiles known from the building industry.
[0041] In this respect it is mentioned that generally a heat
storage material having a high heat capacity in the container of
the thermal energy storage device is preferred in order to keep the
size and the price of the thermal energy storage device at a
realistic level. With the described thermal energy storage and
recovery system it is possible in an advantageous manner to avoid
heat storage material having a high heat capacity like chamotte,
magnesia, dolomite, mullite etc. which are typically not available
at every location and which are often rather costly.
[0042] According to a further embodiment, the heat storage material
comprises concrete. A thermal energy storage device based on
concrete may be in particular used in places where rocks are not
available. Instead of using only sand, which requires an
appropriate support structure within the container in order to
allow heat transfer medium to flow through the container, sand can
be used in a concrete mix in order to have fixed spatial structures
where the heat transfer medium such as air can flow around and a
direct heat transfer can be obtained.
[0043] The concrete may be formed as concrete piles distributed
within the container of the thermal energy storage device. The
concrete piles can be casted on the site using local raw material
as filler. The concrete piles can be positioned at different
patterns within the thermal storage depending on the optimum flow
patterns, heat transfer and pressure drop. The concrete solution is
in particular suitable in areas where rocks are not available.
[0044] It is mentioned that also concrete bricks may be used.
Thereby, the concrete bricks may be packed in a same manner as the
above described solution where rocks or a rock material is used as
heat storage material. The concrete bricks may be accommodated in
an appropriate bed structure.
[0045] According to a further embodiment, the heat transfer fluid
and/or the working fluid is a gas, in particular air. Thereby, it
is not necessary to use one type of gas both in the
charging/discharging arrangement and in the storage arrangement.
For instance it is possible to use Argon as the working fluid
within the charging/discharging arrangement and another type of gas
like air in the storage arrangement.
[0046] Further, as has already been mentioned above it is also
possible that the working fluid undergoes a change of its state of
aggregation. Anyway, the overall amount of gas needed for charging
the thermal energy storage device is lower than the amount of gas
used in prior art solutions for temporarily storing thermal
energy.
[0047] The aspects defined above and further aspects are apparent
from the examples of embodiment to be described hereinafter and are
explained with reference to the examples of embodiment.
BRIEF DESCRIPTION OF THE DRAWING
[0048] FIG. 1 shows a thermal energy storage and recovery system
with an air-to-air heat exchanger thermodynamically connecting a
storage arrangement with a charging/discharging arrangement.
[0049] FIG. 2 shows a thermal energy storage and recovery system
with an air-to-steam heat exchanger thermodynamically connecting a
storage arrangement with a charging/discharging arrangement.
[0050] FIGS. 3 and 4 show a thermal energy storage device working
with air at ambient pressure.
[0051] FIGS. 5, 6 and 7 show a manifold system for feeding a
gaseous heat transfer fluid into a container of a thermal energy
storage device and/or for receiving a gaseous heat transfer fluid
from a container of a thermal energy storage device.
[0052] FIG. 8 shows a thermal energy storage device using concrete
piles as a heat storage material.
[0053] FIGS. 9, 10 and 11 show a thermal energy storage device
using sand being accommodated in metal profiles as a heat storage
material.
DETAILED DESCRIPTION
[0054] The illustration in the drawing is schematically. It is
noted that in different figures, similar or identical elements are
provided with the same reference signs or with reference signs,
which are different from the corresponding reference signs only
within the first digit.
[0055] FIG. 1 shows a thermal energy storage and recovery system
100 comprising a thermodynamic storage arrangement 110 and a
thermodynamic charging/discharging arrangement 160. The thermal
energy storage and recovery system 100 further comprises an
air-to-air heat exchanger 180 which thermodynamically couples the
storage arrangement 110 with the charging/discharging arrangement
160.
[0056] According to the embodiment described here the storage
arrangement 110 comprises a thermal energy storage device 120
having a container 122 being filled with a non depicted heat
storage material and two fluid terminals, a first fluid terminal
122a and a second fluid terminal 122b. One fluid terminal is used
for inserting a heat transfer fluid which is circulating through
the storage arrangement 110 into the interior of the container 122
and the other fluid terminal is used for extracting the heat
transfer medium from the interior of the container 122. The storage
arrangement 110 further comprises two means for driving a flow of
heat transfer fluid. According to the embodiment described here the
first means is a first fan 141 and the second means is a second fan
142.
[0057] The charging/discharging arrangement 160 comprises two fluid
energy machines, a compressor 162 and an expander 163. Further, the
charging/discharging arrangement 160 comprises a further heat
exchanger 190 which, as will be described below in more detail, can
be used for transferring cold from a working fluid of the
charging/discharging arrangement 160 to a not depicted device using
the cold. This device may be e.g. a cold storage, a district
cooling system and/or a condenser.
[0058] The storage arrangement 110, which represents the low
pressure side of the thermal energy storage and recovery system
100, is configured in such a manner that the heat transfer fluid
circulating through the storage arrangement 110 is always at a low
pressure. According to the embodiment described here the heat
transfer fluid is air. The fans 141 and 142 are only used for
driving the air flow. They are not used for generating significant
pressure differences along the pathway of the air flow. In order to
minimize such pressure differences at least two fans 141, 142 are
used. Thereby, one fan 141 is arranged upstream of the container
122 and the other fan 142 is arranged downstream of the container
122. Specifically, the fans 141 and 142 can be located at one or
more positions for instance in front of the heat exchanger 180,
inside the thermal energy storage device 120 and/or between the
heat exchanger 180 and the thermal energy storage device 120.
[0059] The fans 141, 142 are designed to generate and maintain a
certain flow of heat transfer fluid/air through the pipe
connections, the heat exchanger 180 and the thermal energy storage
device 120. Thereby, a pressure drop within the thermal energy
storage device 120 should be taken into account when the designing
the storage arrangement 110. In this respect it is mentioned that a
pressure drop increases as the length of the thermal energy storage
device 120 goes up due to the fact the heat transfer fluid/air has
to travel through more storage material. In the end it is an
optimization problem between the storage capacity, the length and
the width of the thermal energy storage device 120, the pressure
drop, and the size of the machinery.
[0060] The depicted thermal energy storage and recovery system 100
can be operated in two different operational modes. In a first
operational mode which is depicted here both the heat transfer
fluid/the air within the storage arrangement and the working fluid
within the charging/discharging arrangement circulate in the
clockwise direction. In the first operational mode thermal energy
is produced by the compressor, which, after having been transferred
via the heat exchanger 180 to the storage arrangement 110, is
transferred to the thermal energy storage device 120. In this first
operational mode some mechanic energy, which is generated within
the expander 164 by the working fluid leaving the heat exchanger
180, can be used for supporting the compression of the working
fluid within the compressor. The expander 164 and the compressor
162 are preferably mechanical connected on the same shaft (not
depicted) in order to efficiently use the mechanic energy being
generated by the working fluid expansion for compressing the
working fluid within the compressor 162.
[0061] In order to change the operational mode of the thermal
energy storage and recovery system 100 to a second operational
mode, wherein thermal energy, which before has been stored within
the thermal energy storage device 120, is extracted from the
thermal energy storage device 120, the flow direction both of the
heat transfer fluid/air and the working fluid has to be reversed.
In the storage arrangement 110 this can be realized simply by
driving the fans 141 and 142 in the opposite direction. In the
second operational mode heat is transferred from the heat transfer
fluid via the heat exchanger 180 to the working fluid. In the
charging/discharging arrangement 160 this energy can be used in a
known manner by the fluid energy machine 162, which now works as a
turbine. Again, in order keep the working fluid circulating a part
of the mechanic energy being generated by the turbine 162 can be
used for compressing the working fluid within the fluid energy
machine 164, which now works like a compressor.
[0062] It is mentioned that instead of reversing the direction of
one fans also separate fans optimized for either charging or
discharging thermal energy can be used. The mass flow in the high
pressure side (charging/discharging arrangement) and the low
pressure side (storage arrangement) should be the same when the
same type of gas is used on both sides. The mass flow needed per
MWh when air is used is around 3 kg/s.
[0063] The heat exchanger 180, the fans 141 and 142 and the thermal
energy storage device are preferably connected to each other by
insulated steel pipes. Alternatively, the heat exchanger 180 can be
located inside the thermal energy storage device 120 at a hot end
in such a way that a leakage from the heat exchanger 180 stays
inside the thermal energy storage device 120.
[0064] It is an important aspect of the thermal energy storage and
recovery system 100 described in this document that the thermal
energy storage device 120 works at ambient pressure so there is no
need for a pressurized storage vessel. The thermal energy storage
device 120 has a number of inlets and outlets located at each end
which enables a flow of heat transfer fluid/air through the
container 122 of the thermal energy storage device 120. The thermal
energy storage device 120 may contain storage material like rocks,
sand, concrete or similar cheap and easy available storage
material.
[0065] In FIG. 1 there are depicted appropriate values for the
operational parameters pressure p and temperature T within the
thermal energy storage and recovery system 100 when being operated
in the first operational mode. Since theses values and their
thermodynamic relevance are well known for a skilled person, no
further details are given in this description.
[0066] It is mentioned that the described thermal energy storage
and recovery system 100 is aimed for storing tenth and preferably
hundreds of MWh in form of thermal energy using rocks, sand or
similar material as thermal storage material. As a consequence the
volume of heat storage material being accommodated within the
container 122 is relatively high and the dimensions of the thermal
energy storage device 120 are considerable. The described thermal
energy storage and recovery system 100 makes it economical feasible
to build a large thermal energy storage devices 120 using known
building materials such as concrete, steel and/or local storage
material such as rocks or sand. Local contractors can be used for
the construction work of the thermal energy storage device 120
since normal materials and principles can be used for the
construction.
[0067] The described thermal energy storage and recovery system 100
makes it possible to avoid storage of pressurized gas inside the
thermal energy storage device 120. The volume of pressurized gas
needed in the system 100 is considerably lower than in known
solutions where the volume between the walls in the thermal energy
storage device 120 and the heat storage material is filled with the
gas at high pressure. Large volume of heavy gas types like argon
stored in vessels is also a potential safety hazard due to the fact
that Argon is heavier than air and force oxygen to rise in case of
an unwanted leakage.
[0068] FIG. 2 shows a thermal energy storage and recovery system
200 with an air-to-steam heat exchanger 280 thermodynamically
connecting a storage arrangement 110 a charging/discharging
arrangement 260. Compared to the system 100 shown in FIG. 1 the
system 200 comprises the same storage arrangement 110 at the low
pressure side. In FIG. 2 the charging/discharging arrangement 260
is illustrated in the second operational mode, i.e. stored thermal
energy is retrieved from the thermal energy storage device 100 and
converted to mechanic energy.
[0069] As can be seen from FIG. 2, the charging/discharging
arrangement 260, which represents the steam side of the thermal
energy storage and recovery system 200, comprises a pump 265 for
feeding liquid working fluid (e.g. water) to the heat exchanger
280. After having received thermal energy from the heat transfer
fluid/air of the storage arrangement 110 the working fluid
evaporates such that water steam is generated. The thermal energy
being included in the water steam is then used in a known manner in
a steam turbine 266 in order to generate mechanical energy.
According to the embodiment described here this mechanical energy
is used at least partially for operating an electric generator 269.
The cooled down steam leaving the steam turbine 266 is then
condensed in a condenser 267, which is connected to the pump in
order to close the water-steam cycle.
[0070] It is mentioned that in FIG. 1 the heat transfer fluid/the
air (a) is inserted into the thermal energy storage device 120 via
the first fluid terminal 122a being located at the hot end of the
container 122 and is leaving the thermal energy storage device 120
via the second fluid terminal 122b being located at the cold end of
the container 122. By contrast thereto, in FIG. 2 the heat transfer
fluid/the air (a) is inserted into the thermal energy storage
device 120 via the second fluid terminal 122b being located at the
cold end of the container 122 and is leaving the thermal energy
storage device 120 via the first fluid terminal 122a being located
at the hot end of the container 122. Therefore, the effective
thermodynamic flow direction of the heat transfer fluid/air in the
storage arrangement 110 shown in FIG. 1 is different from the
effective thermodynamic flow direction of the heat transfer
fluid/air in the storage arrangement 110 shown in FIG. 2.
[0071] Descriptive speaking, the stored thermal energy is recovered
by a flow of heat transfer fluid/air in the direction shown in FIG.
2. Thereby, heat transfer fluid/air at ambient temperature is blown
or sucked through the thermal energy storage device 120 whereby
transfer fluid/air is heated up by heat transfer from the hot heat
storage material. The transfer fluid/air leaves the thermal energy
storage device 120 at a temperature corresponding to the
temperature level in the hot end of the container 122 preferably
around 550.degree. C. The temperature level corresponds to the
temperature level used in steam cycles in thermal power plants.
Subsequently, the heated up heat transfer fluid/air is let through
the heat exchanger 280 in order to generate steam of the working
fluid within the charging/discharging arrangement 260. The steam is
hereafter fed into the steam turbine 266 that is coupled to the
electric generator 269 for the production of electrical power.
[0072] It is mentioned that the described "steam discharge
solution" can piggy back on existing thermal power plants (nuclear,
coal etc.) where existing machinery such as the condenser, steam
turbine or boiler can be reused. Furthermore, the cold produced by
the expanded air in the charging cycle can be used to lower the
temperature in the condenser for improving the overall efficiency
of the thermal power plant or for saving water for cooling. Lower
temperature in condenser results in larger pressure drops over the
steam turbine whereby overall efficiency of the plant is
increased.
[0073] It is further mentioned that traditional thermal power
plants use a huge amount of water for cooling purposes in the
condenser. Air cooled condensers are becoming standard in newer
plants in order to reduce the massive amount of water used in the
water cooled condenser. The cold produced in the expander 164
(shown in FIG. 1) can improve the situation both for water cooled
and direct air cooled condensers.
[0074] FIGS. 3 and 4 show a thermal energy storage device 320
working with air at ambient pressure. Within a container 322 of the
thermal energy storage device 320 there is provided a cheap and
widely available storage material such as sand, rocks or other
geological materials available in the respective area. Long and
costly transportation of storage material can hereby be
avoided.
[0075] According to the embodiment described here an outer wall 327
of the container 322 is made of concrete. At the inside the
container wall 327 is insulated by a 0.5 to 2 meter thick layer of
insulation material 328 that is able to withstand temperatures
above 550C.
[0076] An internal support structure can be used to keep the heat
storage material in place without compressing the porous insulation
material. For instance, a metal mesh or inner walls can be used to
keep rocks in place.
[0077] The floor in the container 322 can be build up by reinforced
concrete with porous insulation material below. Alternatively, it
is possible to place the heat storage material directly on top of
the insulation material.
[0078] Insulation material like LECA .RTM. can be used for this
purpose. LECA.RTM. is burned clay that is burned until all organic
material is evaporated and the clay expands and forms small balls
which are porous having insulation properties. Rocks and sand can
be put directly on top of the insulation without compressing,
reducing or crunching the insulation properties.
[0079] The storage unit can be located above ground or sunken into
the ground.
[0080] Also the thermal energy storage device 320 shown in FIGS. 3
and 4 comprises a first fluid terminal 322a and a second fluid
terminal 322b for receiving respectively for emitting heat transfer
fluid/air. In order to minimize the flow resistance the first fluid
terminal 322a is connected to an outer manifold system 323a with
which the flow of heat transfer fluid/air is distributed into
different spatially separated channels. Accordingly, also the
second fluid terminal 322b is connected to an outer manifold system
323b. Further, the interior of the container 325 representing the
heat storage region of the container 322 comprises an inner
manifold system 326b for spatially distributing the flow of heat
transfer fluid/air into a wide region (when heat transfer fluid/air
is inserted into the container via the manifold system 326b) or for
spatially merging various spatially distributed flow paths of heat
transfer fluid air into one common flow path (when heat transfer
fluid/air is emitted from the container via the manifold system
326b).
[0081] FIGS. 5, 6 and 7 show a manifold system 426 for feeding a
gaseous heat transfer fluid into a container of a thermal energy
storage device and/or for receiving a gaseous heat transfer fluid
from a container of a thermal energy storage device. The manifold
system 426 depicted best in FIG. 7 comprises an inlet/outlet pipe
426-1 and a plurality of distribution pipes 426-2. Further, a
plurality of funnels 426-3 is associated with each distribution
pipe 426-2.
[0082] Descriptive speaking, a thermal energy storage device in
accordance with an embodiment comprises inlets/outlets at each end
that enable the flow of heat transfer fluid/air through the
container 322. Each end is covered with outlets/inlets in order to
utilize the heat storage material at each end. The inlets/outlets
may be formed as feed inlets in order to reduce
turbulences/pressure drops at the inlets and to catch the heat
transfer fluid/air and in order to reduce unwanted pressure drops
at the outlets.
[0083] FIG. 8 shows a thermal energy storage device 520 using
concrete piles 540 as a heat storage material. Also the thermal
energy storage device 520 comprises a container 522. At a first end
of the container 522 there is provided a first fluid terminal 522a
being associated with a first outer manifold system 523a. At a
second end of the container 522 there is provided a second fluid
terminal 522b being associated with a second outer manifold system
523b.
[0084] The concrete piles 540 are arranged in a parallel
orientation with respect to each other. In order to allow for a
flow of heat transfer fluid/air through the container 522 the
concrete piles 540 are spatially distributed such that they are
spatially separated from each other. Thereby, the dimensions
denominated in the right part of FIG. 8 showing an enlarged view of
the upper right corner of the container 522 are given in
millimeters. It is mentioned that these dimensions are given only
as an example and that of course also other dimensions are
possible.
[0085] Further, the concrete piles 540 can be casted on the site of
erection of the thermal energy storage device 520 using local raw
material as filler. The concrete piles 540 can be positioned at
different patterns within the thermal energy storage device 520
depending on the optimum flow patterns, heat transfer and pressure
drop. The concrete piles 540 might be optionally perforated by one
or more holes for increasing the heat transfer between the outside
and the inside of the concrete piles 540. The described concrete
solution is in particular suitable in areas where rocks are not
available as heat storage material.
[0086] FIGS. 9, 10 and 11 show a thermal energy storage device 620
using sand as heat storage material. As can be seen from the
various illustrations given in these Figures, the thermal energy
storage device 620 comprises a container 622. In the upper right
illustration in FIG. 6 an inner manifold system 626 can be
seen.
[0087] Within the container 622 there are provided a plurality of
support devices 670 each carrying a certain amount of sand 675.
According to the embodiment described here the support devices are
lengthy metal profiles 670 each being bended along the longitudinal
direction of the profiles 670. The sand 675 in located in a lower
channel formed by the profiles 670. Above the lower channel there
is a free space 676 which represents an upper channel which during
operation of the thermal energy storage device 620 is used for a
flow of heat transfer fluid.
[0088] The thermal energy storage and recovery system described in
this document makes it possible to decouple the charging and the
discharging of a thermal energy storage device by using a heat
exchanger between a high pressure side and a low pressure
respectively a steam side. It is hereby possible to have different
charge and discharge rates for the thermal energy storage device
due to the fact that different machinery may be used for the
charging and the discharging. For instance it is possible to
discharge the thermal energy storage device at a faster rate than
it was charged or vice versa.
[0089] It is mentioned that also other discharge configurations are
possible. For instance it is possible to discharge using compressed
air that is heated up by the hot air from the thermal energy
storage device using the heat exchanger. The heated up and
compressed air may be let through an air turbine in order to
produce electrical energy. Further, the outlet air from such an air
turbine may be used directly or indirectly by a heat exchanger to
cool the surrounding air in one or more rooms, e.g. for air
conditioning purposes inside one or more buildings. This also
increases the total efficiency of the described thermal energy
storage and recovery system.
[0090] In the following there is given as an example some technical
data for a thermal energy storage plant having a storage capacity
of 48 MW for 10 days. As a heat storage material a material having
a porosity of 40% may be used. This means that at ambient pressure
of around 1 bar the heat storage material comprises 40% Vol. air
and 60% Vol. heat storage material. The necessary air mass flow may
be 137.76 kg/s (air is the heat transfer fluid). This means that
for one MW an air mass flow of 2.87 kg/s is necessary. The size of
the stones being used as the porous heat storage stones may be 0.05
m. The size of the whole thermal energy storage device may be 10 m
height.times.425 m wide.times.30 m long. The thermal energy storage
device is wider than it is long in order to decrease pressure
drops. A calculated pressure drop of the air flowing through the
thermal energy storage device may be (only) 0.69 mbar.
[0091] It should be noted that the term "comprising" does not
exclude other elements or steps and the use of articles "a" or "an"
does not exclude a plurality. Also elements described in
association with different embodiments may be combined. It should
also be noted that reference signs in the claims should not be
construed as limiting the scope of the claims.
* * * * *