U.S. patent application number 13/279475 was filed with the patent office on 2012-04-26 for dynamic switching thermoelectric thermal management systems and methods.
Invention is credited to Timothy David Sands, Yuefeng Wang.
Application Number | 20120096871 13/279475 |
Document ID | / |
Family ID | 45971803 |
Filed Date | 2012-04-26 |
United States Patent
Application |
20120096871 |
Kind Code |
A1 |
Wang; Yuefeng ; et
al. |
April 26, 2012 |
DYNAMIC SWITCHING THERMOELECTRIC THERMAL MANAGEMENT SYSTEMS AND
METHODS
Abstract
A dynamic switching thermoelectric thermal management system and
method is disclosed. The thermal management system includes a heat
dissipation device, a thermoelectric module, an ambient temperature
sensor, a heat source temperature sensor, an energy storage device
and a controller. One side of the thermoelectric module is
thermally coupled to the heat source and another side is thermally
coupled to the heat dissipation device. The controller periodically
samples the temperature sensors and dynamically switches the
thermoelectric module between a power generation mode in which the
thermoelectric module uses the temperature difference between the
heat source and ambient to charge the energy storage device, a
cooling mode in which the thermoelectric module is powered to
create a voltage difference across the thermoelectric module to
cool the heat source, and an idle mode. The thermal management
system can be integrated into a portable electronic device, for
example a portable computing device.
Inventors: |
Wang; Yuefeng; (West
Lafayette, IN) ; Sands; Timothy David; (West
Lafayette, IN) |
Family ID: |
45971803 |
Appl. No.: |
13/279475 |
Filed: |
October 24, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61405891 |
Oct 22, 2010 |
|
|
|
Current U.S.
Class: |
62/3.2 |
Current CPC
Class: |
F25B 2700/2107 20130101;
F25B 49/00 20130101; F25B 21/02 20130101; F25B 2321/021
20130101 |
Class at
Publication: |
62/3.2 |
International
Class: |
F25B 21/02 20060101
F25B021/02 |
Claims
1. A dynamic switching thermoelectric thermal management system for
coupling to a heat source, the thermal management system
comprising: a heat dissipation device; a thermoelectric module
having a first side and a second side, the first side being
thermally coupled to the heat source and the second side being
thermally coupled to the heat dissipation device; a first
temperature sensor detecting the ambient temperature of the
environment surrounding the thermal management system; a second
temperature sensor detecting a temperature for the heat source; an
energy storage device; and a controller coupled to the
thermoelectric module, the first and second temperature sensors and
the energy storage device; wherein the controller periodically
samples the first and second temperature sensors and dynamically
switches the thermoelectric module between a power generation mode
in which the thermoelectric module uses the temperature difference
between the heat source and ambient to charge the energy storage
device, a cooling mode in which the thermoelectric module is
powered to cool the heat source, and an idle mode in which the
thermoelectric module neither generates or consumes power.
2. The thermal management system of claim 1, further comprising a
heat spreader having a proximal end and a distal end, the proximal
end of the heat spreader being coupled to the heat dissipation
device and the distal end of the heat spreader being coupled to the
heat source, the first side of the thermoelectric module being
coupled to the heat spreader.
3. The thermal management system of claim 2, wherein the controller
is a programmable microchip.
4. The thermal management system of claim 2, wherein the second
temperature sensor is coupled to the distal end of the heat
spreader.
5. The thermal management system of claim 4, wherein the first
temperature sensor is coupled to the heat dissipation device.
6. The thermal management system of claim 1, wherein the heat
dissipation device is a heat sink having a plurality of fins.
7. The thermal management system of claim 1, wherein the heat
dissipation device is a liquid cooling device.
8. The thermal management system of claim 1, wherein the heat
dissipation device dissipates heat to the surrounding environment
by conduction.
9. The thermal management system of claim 1, further comprising a
fan forcing fluid over the heat dissipation device to dissipate
heat to the surrounding environment by forced convection.
10. The thermal management system of claim 1, further comprising a
pump forcing liquid over the heat dissipation device to dissipate
heat to the surrounding environment by forced convection.
11. The thermal management system of claim 1, wherein the energy
storage device is a battery.
12. The thermal management system of claim 1, wherein the energy
storage device powers the thermoelectric module during cooling
mode.
13. The thermal management system of claim 1, further comprising a
portable electronic device into which the thermal management system
is integrated.
14. The thermal management system of claim 13, wherein the portable
electronic device is a portable computing device.
15. A method for controlling a dynamic switching thermoelectric
thermal management system that includes a thermoelectric module
having a first side thermally coupled to a heat source and a second
side thermally coupled to a heat dissipation device, the method
comprising: monitoring a heat source temperature of the heat
source; monitoring an ambient temperature of the ambient
environment surrounding the thermal management system; dissipating
heat from the heat source using the heat dissipation device; when
the heat source temperature is greater than the ambient temperature
and less than a critical working temperature, putting the thermal
management system in a power generation mode for charging an energy
storage device using the temperature difference across the
thermoelectric module; and when the heat source temperature is
greater than the critical working temperature, putting the thermal
management system in a cooling mode for cooling the heat source
using a voltage difference across the thermoelectric module.
16. The method of claim 15, wherein the energy storage device is
used to create the voltage difference across the thermoelectric
module when the thermal management system is in the cooling
mode.
17. The method of claim 16, further comprising conducting heat from
the heat source to the thermoelectric module through a heat
spreader that includes a proximal end coupled to the first side of
the thermoelectric module and a distal end coupled to the heat
source.
18. The method of claim 17, wherein the temperature sensor for
monitoring the heat source temperature is coupled to the distal end
of the heat spreader.
19. The method of claim 18, wherein the temperature sensor for
monitoring the ambient temperature monitors the temperature near
the heat dissipation device.
20. The method of claim 19, wherein the heat source temperature and
the ambient temperature are monitored periodically.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/405,891, filed on Oct. 22, 2010, entitled
"Dynamic Switching Thermoelectric Thermal Management Systems and
Methods" which is incorporated herein by reference.
BACKGROUND AND SUMMARY
[0002] This invention relates to a dynamic switching thermal
management system and more particularly to a temperature
controlling system using a thermoelectric module and an energy
storage device.
[0003] For most heat generating systems, a large fraction of energy
is dissipated as waste heat. As a result, the temperatures of the
heat sources in the system are elevated. Most of these heat sources
need passive or powered heat dissipation devices to extract the
waste heat and maintain the critical components of the system
within a desired temperature range. Moreover, the powered cooling
devices need additional energy to operate.
[0004] Prior systems have used a fan driven heat sink assembly that
includes a fan assembly mounted on a heat sink. The heat sink has a
solid flat base and a plurality of spaced cooling fins, and the fan
provides forced air convective heat transfer on the surfaces of the
heat exchanger. Other systems have used a thermoelectric heat pump
that is resistant to thermal stresses incurred during thermal
cycling between cold and hot temperatures. Other alternative
thermal management systems include water cooling circulation
systems with pipes to spread the heat of a heat source.
[0005] The waste heat can provide a source of energy recovery as
well. The temperature difference between the hot heat sources and
the cold ambient makes thermoelectric power generation possible.
The temperature difference can creates an electric potential
difference in thermoelectric materials. If an external load is
connected, the thermoelectric material can serve as a power source
in the completed circuit. During thermoelectric power generation,
the temperature of the heat source will be raised compared to its
temperature without the power generation device. In certain
scenarios, heat generating systems can work in elevated temperature
ranges; eliminating the need to further cool the heat sources down.
However, if the desired operating temperature range is exceeded,
the performance of the system may be compromised.
[0006] It would be desirable to have a thermal management system
that can recover energy from the waste heat of a system and that
can control the heat source temperature to maintain the desired
operating conditions for the system.
[0007] Thermoelectric effects include the direct conversion of
temperature differences to electric potential differences (Seebeck
effect) and electric potential differences to temperature
differences (Peltier effect). The names are derived from the
independent discoveries of French physicist Jean Charles Athanase
Peltier and Estonian-German physicist Thomas Johann Seebeck. In
1821, Seebeck found that if two dissimilar metals are connected and
there is a temperature difference across the junction, a voltage
will develop across the junction. The Seebeck effect forms the
basis of the power generation function of a thermoelectric device.
In 1834, Peltier discovered the inverse Seebeck effect where if a
current is flowing through two dissimilar metals connected at a
junction, a temperature gradient will develop across the junction,
which leads to a heat flux. The Peltier effect forms the basis of
the cooling function of a thermoelectric device. In the 1900's,
researchers found efficient thermoelectric materials that possess
large Seebeck coefficients (S), high electrical conductivity
(.sigma.) and low thermal conductivity (.kappa.). The performance
(i.e., efficiency of Seebeck or Peltier effect) of thermoelectric
materials can be expressed in terms of a dimensionless figure of
merit (ZT), where Z is given by Z=S.sup.2.sigma./.kappa., and T is
temperature. Now, a thermoelectric device utilizing properly doped
semiconductor materials can provide high performance either in
Seebeck power generation or Peltier cooling. The device usually
includes dozens of p and n type semiconductor legs connected
electrically in series and thermally in parallel, sandwiched
between two plates made of a material that is an electrical
insulator with high thermal conductivity. It normally has two power
wires, the "+" and "-" connectors. When applying a voltage on the
wires, it works in Peltier cooling mode, which pumps heat from one
side to the other. When connecting the two power wires to an energy
storage device and applying a temperature difference across the two
sides, it works in Seebeck power generation mode, which generates
electricity.
[0008] A solid state dynamic switching thermal management system is
described herein. An exemplary embodiment of the system includes a
heat spreader, a thermoelectric module, a heat dissipation device,
an energy storage device, two temperature sensors, and a
programmable microchip. The heat spreader is coupled to a heat
source that is under the thermal management of the dynamic
switching system. The heat spreader carries heat away from the heat
source. One of the temperature sensors detects the temperature of
the heat source, and the other temperature sensor detects the
temperature of the ambient environment around the heat dissipation
device. One side of the thermoelectric module is thermally coupled
to the heat spreader, and the other side of the thermoelectric
module is thermally coupled to the heat dissipation device. The
thermoelectric module switches between power generation (Seebeck
power generation function) and cooling (Peltier cooling function).
The programmable microchip is coupled to the thermoelectric module,
the two temperature sensors and the energy storage device. The
microchip periodically samples the two temperature sensors,
controls the system temperatures and controls powering of the
cooling function.
[0009] A dynamic switching thermoelectric thermal management system
for coupling to a heat source is disclosed. This embodiment of the
thermal management system includes a heat dissipation device, a
thermoelectric module, first and second temperature sensors, an
energy storage device and a controller. The thermoelectric module
includes a first side thermally coupled to the heat source and a
second side thermally coupled to the heat dissipation device. The
first temperature sensor detects the ambient temperature of the
environment surrounding the thermal management system, and the
second temperature sensor detects a temperature for the heat
source. The controller is coupled to the thermoelectric module, the
first and second temperature sensors and the energy storage device.
The controller periodically samples the first and second
temperature sensors and dynamically switches the thermoelectric
module between a power generation mode, a cooling mode, and an idle
mode. In the power generation mode, the thermoelectric module uses
the temperature difference between the heat source and ambient to
charge the energy storage device. In the cooling mode, the
thermoelectric module is powered to create a voltage difference
across the thermoelectric module to cool the heat source. In the
idle mode, the thermoelectric module neither generates nor consumes
power. The thermal management system can be integrated into a
portable electronic device, for example the thermal management
system can be integrated into a portable computing device.
[0010] The thermal management system can include a heat spreader
with a proximal end coupled to the heat dissipation device and a
distal end coupled to the heat source, the first side of the
thermoelectric module being coupled to the heat spreader. The
controller can be a programmable microchip. The second temperature
sensor can be coupled to the distal end of the heat spreader. The
first temperature sensor can be coupled to the heat dissipation
device. The energy storage device can be a battery. The energy
storage device can power the thermoelectric module during cooling
mode.
[0011] The heat dissipation device can be, for example, a heat sink
having a plurality of fins or a liquid cooling device. The heat
dissipation device can dissipate heat to the surrounding
environment by conduction. The thermal management system can
include a fan for forcing fluid over the heat dissipation device to
dissipate heat to the surrounding environment by forced convection.
The thermal management system can include a pump forcing liquid
over the heat dissipation device to dissipate heat to the
surrounding environment by forced convection.
[0012] A method is disclosed for controlling a dynamic switching
thermoelectric thermal management system that includes a
thermoelectric module having a first side thermally coupled to a
heat source and a second side thermally coupled to a heat
dissipation device. The method includes monitoring a temperature of
the heat source; monitoring a temperature of the ambient
environment surrounding the thermal management system; and
dissipating heat from the heat source using the heat dissipation
device. When the heat source temperature is greater than the
ambient temperature and less than a critical working temperature,
the method includes putting the thermal management system in a
power generation mode for charging an energy storage device using
the temperature difference across the thermoelectric module. When
the heat source temperature is greater than the critical working
temperature, the method includes putting the thermal management
system in a cooling mode for cooling the heat source using a
voltage difference across the thermoelectric module. The energy
storage device can be used to create the voltage difference across
the thermoelectric module when the thermal management system is in
the cooling mode. The method can also include conducting heat from
the heat source to the thermoelectric module through the heat
spreader, where the heat spreader includes a proximal end coupled
to the first side of the thermoelectric module and a distal end
coupled to the heat source. The temperature sensor for monitoring
the heat source temperature can be coupled to the distal end of the
heat spreader. The temperature sensor for monitoring the ambient
temperature can monitor the temperature near the heat dissipation
device. The heat source temperature and ambient temperature can be
monitored periodically.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 shows an exploded illustration of the components of
an exemplary embodiment of a thermoelectric thermal management
system;
[0014] FIG. 2 shows a flow chart of an exemplary embodiment of a
dynamic switching function algorithm which can control a
thermoelectric thermal management system; and
[0015] FIG. 3 shows a graph of an estimate of the maximum power
density that an ideal dynamic switching thermoelectric module can
produce in a laptop application.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0016] For the purposes of promoting an understanding of the
principles of the novel technology, reference will now be made to
the embodiments described herein and illustrated in the drawings
and specific language will be used to describe the same. It will
nevertheless be understood that no limitation of the scope of the
novel technology is thereby intended, such alterations and further
modifications in the illustrated devices and methods, and such
further applications of the principles of the novel technology as
illustrated therein being contemplated as would normally occur to
one skilled in the art to which the novel technology relates.
[0017] FIG. 1 illustrates an exemplary embodiment of a
thermoelectric thermal management system. The components in FIG. 1
are not necessarily drawn to scale, the emphasis instead being to
clearly illustrate the principles of the embodiment of the
thermoelectric thermal management system. This embodiment of the
thermal management system includes a heat spreader 10, a
thermoelectric module 20, a heat dissipation device 30, an energy
storage device 40, an ambient temperature sensor 50, a heat source
temperature sensor 52, and a programmable microchip 60. The heat
spreader 10 is thermally coupled to a heat source 70 that is under
the thermal management of the dynamic switching system. The heat
spreader 10 carries heat away from the heat source 70. One side of
the thermoelectric module 20 is thermally coupled to the heat
spreader 10, and another side of the thermoelectric module 20 is
thermally coupled to the heat dissipation device 30. The
thermoelectric module 20 switches between power generation (Seebeck
working mode) and cooling (Peltier working mode). The thermal
coupling can be done using heat conductive materials, for example a
thermal adhesive, between of the surfaces of the components to be
thermally coupled. The ambient temperature sensor 50 detects the
ambient temperature of the air or other working fluid in which the
system is situated. The heat source temperature sensor 52 detects
the temperature of the heat source. The programmable microchip 60
is coupled to the thermoelectric module 20, the two temperature
sensors 50 and 52, and the energy storage device 40. The microchip
60 periodically samples the two temperature sensors 50 and 52,
controls the system temperatures and controls powering of the
cooling function.
[0018] The temperature sensors 50 and 52 can be coupled the
microchip 60 with signal cables. The ambient temperature sensor 50
can be connected to a surface of the heat dissipation device 30
that is exposed to the ambient environment where the ambient
temperature sensor 50 can have convective heat transfer with the
ambient working fluid, for example air. Alternatively, the ambient
temperature sensor 50 can be coupled to another surface where the
ambient temperature sensor 50 is exposed to the ambient temperature
of the environment. The heat source temperature sensor 52 can be
connected to the heat spreader 10 adjacent to the heat source 70,
or can be connected to the surface of the heat source 70, or can
otherwise be located within the generally isothermal area of the
temperature of the heat source 70.
[0019] The arrow 80 indicates that a fluid, such as air or water,
can be moved across the heat dissipation device 30 to dissipate
heat using forced convection. Alternatively, conduction or other
methods can be used to dissipate the heat.
[0020] The heat spreader 10 can be made of any heat conducting
materials, heat pipes or other heat conducting devices with phase
transformation mechanism. The temperature difference between the
two ends of the heat spreader 10 should be smaller than the
temperature of the heat source 70.
[0021] The heat dissipation device 30 is illustrated as a heat sink
with a plurality of fins. Other configurations of heat dissipation
devices can be used. The heat dissipation device 30 can be made of
any type of heat conducting materials or liquid cooling devices.
The interaction of the heat dissipation device 30 and the
surrounding environment working fluid can be conduction, free
convection or forced convection, for example forced air flow by a
powered fan or forced water flow by a pump.
[0022] The thermoelectric module 20 can be connected by power cords
to the microchip 60. The microchip 60 controls the temperature
detection of the two temperature sensors 50 and 52, and also
controls the switching between Seebeck power generation mode and
Peltier cooling mode of the thermoelectric module 20.
[0023] The energy storage device 40 can be a battery, a capacitor
or other energy storage mechanism that can store electrical energy
temporarily or long term. The energy storage device 40 can be the
main electrical power source of the heat generating system. The
energy storage device 40 is under control of the microchip 60 to be
charged by the thermoelectric module 20 or to power the cooling
function of thermoelectric module 20.
[0024] The Seebeck power generation function can recover waste heat
energy, and the solid state Peltier cooling function can enhance
the cooling efficiency for heat sources. These will give an overall
energy benefit for any thermal system, especially for portable
electronic devices.
[0025] FIG. 2 shows an exemplary flow chart 200 for the control of
a dynamic switching function of a thermoelectric thermal management
system.
[0026] At block 210 the heat generating system starts which can
signal the start of the thermal management system. As the heat
generating system operates, the heat source 70 starts generating
heat and raising its surface temperature. At block 220, the
microchip 60 detects the heat source temperature Th and the ambient
temperature Ta. The heat source temperature Th can be detected
using the heat source temperature sensor 52, and the ambient
temperature Ta can be detected using the ambient temperature
sensors 50.
[0027] At block 230, the system determines whether Th is below a
critical working temperature Tcw for the heat generation system 70.
The critical working temperature is a temperature beyond which the
system will need extra cooling to lower the operating temperature
and maintain desired performance. The critical working temperature
may be a temperature recommended by the manufacturer of the heat
generating system 70. If Th is below the critical working
temperature Tcw, control passes to block 240, otherwise control
passes to block 250.
[0028] At block 240, the system determines whether Th is equal to
or greater than Ta. If Th is equal to or greater than Ta, the
process proceeds to block 260 where the Seebeck power generation
function is implemented and Th will slowly increase. In the
embodiment of FIG. 1, the microchip 60 can connect the
thermoelectric module 20 to the energy storage device 40. Because
of the temperature difference between Th and Ta, a fraction of the
waste heat dissipated through the thermoelectric module 20 can be
converted into electricity to charge the energy storage device 40.
Under the Seebeck power generation function, the system proceeds to
block 270 at stable operation.
[0029] At block 230, if Th is equal to or above the critical
working temperature then the process proceeds to block 250 to
implement the Peltier cooling function. In this case, the heat
source 70 needs extra cooling to lower its temperature and to
maintain a desired performance. In the embodiment of FIG. 1, the
microchip 60 can connect the thermoelectric module 20 to the energy
storage device 40 so that the energy storage device 40 can provide
power to the thermoelectric module 20. Under the Peltier cooling
function, the system proceeds to block 270 at stable operation.
[0030] At block 240, if Th is less than Ta then the process
proceeds to block 270 since the heat source 70 is still cool enough
to operate without the Peltier cooling function and there is no
temperature difference to generate power for the Seebeck power
generation function. This usually happens when the heat source 70
is idle or during the initial start-up of the system.
[0031] From block 270, the system continues to block 280 where it
determines whether to shutdown or to continue operation. At block
280, if the system receives a shutdown command then the system
proceeds to block 290 and shuts down. If the system has not
received a shut down command then, to realize the dynamic switching
mechanism, control passes back to block 220 where the microchip 60
will sample the heat source and ambient temperatures, Th and Ta,
from the temperature sensors 50 and 52 in a real-time or periodic
manner. The sampling interval can range from substantially
continuously, to seconds, to minutes, to hours, depending on the
power of the heat source 70 and the heat capacity of the heat
spreader 10.
[0032] As an example, a laptop or portable device application can
utilize thin profile generators with relatively high heat transfer
coefficients and the possibility of dynamic switching between
Peltier and Seebeck modes. Because most electronic devices run
within a certain temperature range, it is often not necessary to
cool it down further. When a dynamic switching thermoelectric
module as described above is installed on the heat pipes or heat
exchanger surface near the processing units, the thermoelectric
module can scavenge the waste heat to power a battery or a cooling
device if the processing unit is idle and has an operating
temperature higher than the ambient. If the processing unit is
operating and generating a great amount of heat, the thermoelectric
module can be used to cool the heat source. The response time of
the system can be in the range from seconds to hours, thus the
temperature of the processing units can be maintained below a
maximum value as the laptop or portable device cycles in and out of
computationally intense periods. The laptop or portable device with
the thermoelectric module will have an overall energy saving
benefit and can cool the device more efficiently and quietly.
[0033] An estimate can be made of the maximum power density a
dynamic switching thermoelectric module can produce in a laptop.
Assuming that the thermoelectric system has the properties shown in
the following table, the power density versus thickness of the
thermoelectric module is shown in FIG. 3\
TABLE-US-00001 Known parameter Value Seebeck Coefficient -3e-4 V/K
Thermal conductivity 1.2 W/mK Electrical conductivity 1.1e5 s/m
Fraction of coverage 10% Hot side temperature (heat pipes)
60.degree. C. Cold side temperature (Air) 20.degree. C. Heat
transfer coefficient of hot side 1000 W/m.sup.2K Heat transfer
coefficient of cold side 300 W/m.sup.2K
The maximum power density is 1.9e3 W/m.sup.2, which means by using
a 3 cm by 3 cm thermoelectric module, the power generation would be
1.71 W. If the dynamic switching system has 80% time in power
generation mode and 20% in cooling mode, in principle, the 1.71 W
should be enough to power a conventional cooling fan for laptops
which consume approximately 1 W for all the operation time. The
remaining energy may be enough for powering cooling mode power
consumption which is approximately 1.4 W. The excessive energy
produced would be approximately
1.71 W*80%-1 W*100%-1.4 W*20%=0.088 W.
This excess energy could be used to power LED indicators or to back
charge to the main battery.
[0034] The dynamic switching thermoelectric system may enhance the
efficiency and stability of a heat generating system. The
thermoelectric thermal management system can be solid-state without
moving parts, which can lead to a more reliable and quiet
operation. It is apparent that various changes or modification can
be made to the dynamic switching system without deviating from the
original spirit of the invention. While exemplary embodiments
incorporating the principles of the present invention have been
disclosed hereinabove, the present invention is not limited to the
disclosed embodiments. Instead, this application is intended to
cover any variations, uses, or adaptations of the invention using
its general principles. Further, this application is intended to
cover such departures from the present disclosure as come within
known or customary practice in the art to which this invention
pertains.
* * * * *