U.S. patent application number 14/399745 was filed with the patent office on 2015-05-14 for thermoelectric heat pump.
This patent application is currently assigned to SHEETAK, INC.. The applicant listed for this patent is SHEETAK, INC.. Invention is credited to Uttam Ghoshal, Ayan Guha, Himanshu Pokhama.
Application Number | 20150128614 14/399745 |
Document ID | / |
Family ID | 49551237 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150128614 |
Kind Code |
A1 |
Ghoshal; Uttam ; et
al. |
May 14, 2015 |
THERMOELECTRIC HEAT PUMP
Abstract
The present disclosure is related to an apparatus for
transporting heat using a thermoelectric converter. The apparatus
may include a thermoelectric converter, such as a thin-film. The
apparatus may include a heating loop in thermal communication with
a hot side of the thermoelectric converter and a cooling loop in
thermal communication with a cold side of the thermoelectric
converter. The thermoelectric converter may include a stack of
alternating thermoelement and constricted contact layers. The
thermoelectric converter may have a counter-flow fluid loop that
moves a fluid against the temperature gradient of the
thermoelectric converter. The apparatus may be configured to
provide heating or cooling of a fluid, such as air or water. The
apparatus may include a thermal storage medium configured as a
thermal battery.
Inventors: |
Ghoshal; Uttam; (Austin,
TX) ; Guha; Ayan; (Austin, TX) ; Pokhama;
Himanshu; (Saratoga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHEETAK, INC. |
Austin |
TX |
US |
|
|
Assignee: |
SHEETAK, INC.
Austin
TX
|
Family ID: |
49551237 |
Appl. No.: |
14/399745 |
Filed: |
May 8, 2013 |
PCT Filed: |
May 8, 2013 |
PCT NO: |
PCT/US2013/040097 |
371 Date: |
November 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61644187 |
May 8, 2012 |
|
|
|
61764459 |
Feb 13, 2013 |
|
|
|
Current U.S.
Class: |
62/3.3 |
Current CPC
Class: |
F24H 4/04 20130101; F25B
21/00 20130101; H01L 35/30 20130101; Y02B 30/66 20130101; Y02B
30/00 20130101; F25B 2400/24 20130101; F25B 2321/023 20130101; F25B
2321/0252 20130101; F25B 9/14 20130101; F25B 2600/0253 20130101;
F25B 2500/13 20130101; Y02B 30/741 20130101; F25B 2321/0211
20130101; Y02B 30/70 20130101; F25B 21/04 20130101 |
Class at
Publication: |
62/3.3 |
International
Class: |
F25B 21/04 20060101
F25B021/04 |
Claims
1. A thermo electric heat pump apparatus, the apparatus comprising:
a thermoelectric converter having a hot side and a cold side, the
thermoelectric converter comprising: a thermoelectric stack of
thermoelement layers, wherein each thermoelement layer comprises at
least one thermoelement; and a first fluid loop in thermal
communication with the thermoelectric stack and configured to
deliver a first fluid to the thermoelectric stack in a positive
temperature gradient flow direction of the thermoelectric
stack.
2. The apparatus of claim 1, wherein the thermoelectric stack
further comprises: a plurality of constricted contacts layers,
wherein each of the constricted contact layers comprises at least
one constricted contact and wherein the constricted contact layers
alternate with thermoelement layers.
3. The apparatus of claim 1, wherein the thermoelectric stack
further comprises: a plurality of metal sheets, wherein the metal
sheets alternate with the thermoelectric layers, and wherein the
metal sheets are in thermal communication with the first fluid.
4. The apparatus of claim 3, further comprising: at least one fin
in thermal communication with the first fluid and at least one of
the plurality of metal sheets.
5. The apparatus of claim 1, wherein each of the at least one
thermoelement comprises at least one of: i)
Bi.sub.0.5Sb.sub.1.5Te.sub.3, ii) Zn.sub.4Sb.sub.3, iii)
CeFe.sub.3.5Co.sub.0.5Sb.sub.12, iv) Yb.sub.14MnSb.sub.11, v)
MnSi.sub.1.73, vi) NaCo.sub.2O.sub.4, vii) B-doped Si, viii)
B-doped Si.sub.0.8Ge.sub.0.2, ix) Bi.sub.2Te.sub.2.8Se.sub.0.2, x)
PbTe, xi) AgPb.sub.18SbTe.sub.20, xii) PbTe/SrTe--Na, xiii)
Ba.sub.0.08Yb.sub.0.09Co.sub.4Sb.sub.12, xiv)
Mg.sub.2Si.sub.0.4Sn.sub.0.6, xv) TiNiSn, xvi) SrTiO.sub.3, xvii)
P-doped Si, xviii) P-doped Si.sub.0.8Ge.sub.0.2, xix)
La.sub.3Te.sub.4, xx) CoSb.sub.3, xxi) Yb-doped CoSb.sub.3, xxii)
Mg.sub.2Si, xxiii) CePd.sub.3, and xxiv) YbAl.sub.3.
6. The apparatus of claim 5, wherein at least one of the at least
one thermoelement comprises at least one of: i) B-doped Si, ii)
P-doped Si, iii) CoSb.sub.3, iv) Yb-doped CoSb.sub.3, v)
Mg.sub.2Si, vi) CePd.sub.3, and vii) YbAl.sub.3.
7. The apparatus of claim 1, wherein the at least one thermoelement
comprises at least one of: an n-type thermoelement and a p-type
thermoelement.
8. The apparatus of claim 1, wherein the at least one thermoelement
comprises an n-type thermoelement and a p-type thermoelement.
9. The apparatus of claim 1, wherein the first fluid comprises at
least one of: i) water, ii) steam, iii) mineral oil, iv) terphenyl,
and v) a liquid metal.
10. The apparatus of claim 1, wherein the thermoelectric stack is
an n-type thermoelectric stack, and further comprising: a p-type
thermoelectric stack, wherein the p-type thermoelectric stack is in
thermal communication with the first fluid loop and configured to
deliver the fluid to the p-type thermoelectric stack in a positive
temperature gradient flow direction of the p-type thermoelectric
stack.
11. The apparatus of claim 1, wherein the thermoelectric stack is
an n-type thermoelectric stack and further comprising: a p-type
thermoelectric stack; and a second fluid loop in thermal
communication with the p-type thermoelectric stack and configured
to deliver a second fluid to the p-type thermoelectric stack in a
positive temperature gradient flow direction of the p-type
thermoelectric stack.
12. The apparatus of claim 1, further comprising: a hot side fluid
loop in thermal communication with the hot side; and a cold side
fluid loop in thermal communication with the cold side.
13. The apparatus of claim 12, further comprising: at least one
heat exchanger in thermal communication with the first fluid loop
and at least one of: the hot side fluid loop and the cold side
fluid loop.
14. The apparatus of claim 12, wherein one of the hot side fluid
loop and the cold side fluid loop is in thermal communication with
ambient air and the other is in thermal communication with a
heat/cold receiver.
15. The apparatus of claim 14, wherein the heat/cold receiver
comprises a third fluid in a fluid tank
16. The apparatus of claim 14, wherein the heat/cold receiver
comprises a third fluid in an interior of a compartment.
17. The apparatus of claim 1, further comprising: a housing
configured to store a third fluid; a first heat transfer device in
thermal communication with the third fluid and in thermal
communication with one of: i) the hot side and ii) the cold side;
and a second heat transfer device in thermal communication with
other of: i) the hot side and ii) the cold side, and wherein the
second heat transfer device is in thermal communication with
ambient air.
18. The apparatus of claim 17, wherein the housing is thermally
insulated.
19. The apparatus of claim 17, wherein at least one of the heat
transfer devices comprises a thermal diode.
20. The apparatus of claim 17, wherein at least one of the heat
transfer devices comprises a heat exchanger.
21. The apparatus of claim 17, further comprising: a resistance
heater in thermal communication with the third fluid.
22. The apparatus of claim 17, further comprising a forced air
source in thermal communication with the second heat transfer
device.
23. The apparatus of claim 22, wherein the forced air source
comprises a fan.
24. The apparatus of claim 17, wherein a path of thermal
communication between the second heat transfer device and the
ambient air comprises: a thermal storage medium, wherein the second
heat transfer device is in thermal communication with the thermal
storage medium; a third heat transfer device in thermal
communication with the thermal storage medium; and a second
thermoelectric converter with a second hot side and a second cold
side, wherein the third heat transfer device is configured to
transmit heat between the second hot side and the thermal storage
medium.
25. The apparatus of claim 24, further comprising at least one fin
in thermal communication with the second cold side.
26. The apparatus of claim 24, further comprising a forced air
source in thermal communication with the second cold side.
27. The apparatus of claim 26, wherein the force air source
comprises a fan.
28. The apparatus of claim 24, wherein the thermal storage medium
comprises at least one of: i) water, ii) paraffin, iii) a molten
salt and iv) a reversible exothermic hydration material.
29. The apparatus of claim 17, wherein the third fluid comprises at
least one of: water and air.
30. The apparatus of claim 17, further comprising: a baffle
disposed in the housing and configured to partially separate the
third fluid into a first portion and a second portion; a second
thermoelectric converter with a second hot side and a second cold
side; a third heat transfer device in thermal communication with
the third fluid and in thermal communication with one of: i) the
second hot side and ii) the second cold side; and a fourth heat
transfer device in thermal communication with other of: i) the
second hot side and ii) the second cold side, wherein the fourth
heat transfer device is in thermal communication with ambient air,
and wherein the first heat transfer device and the third heat
transfer device vertically separated from one another within the
column.
31. An apparatus for transferring heat to a first fluid, the
apparatus comprising: a housing configured to store the first
fluid; a first heat transfer device configured to be in thermal
communication with the first fluid; a first thermoelectric
converter with a first hot side and a first cold side, wherein the
first hot side is in thermal communication with the first heat
transfer device, and wherein the first heat transfer device is
configured to transmit heat from the first hot side to the first
fluid; and a second heat transfer device in thermal communication
with the first cold side, and wherein the second heat transfer
device is in thermal communication with ambient air and configured
to transmit the cold from the first cold side to the ambient
air.
32. The apparatus of claim 31, wherein the housing is thermally
insulated.
33. The apparatus of claim 31, wherein at least one of the heat
transfer devices comprises a thermal diode.
34. The apparatus of claim 31, wherein at least one of the heat
transfer devices comprises a heat exchanger.
35. The apparatus of claim 31, further comprising: a resistance
heater in thermal communication with the first fluid.
36. The apparatus of claim 31, further comprising a forced air
source in thermal communication with the second heat transfer
device.
37. The apparatus of claim 36, wherein the forced air source
comprises a fan.
38. The apparatus of claim 31, wherein a path of thermal
communication between the second heat transfer device and the
ambient air comprises: a thermal storage medium, wherein the second
heat transfer device is in thermal communication with the thermal
storage medium; a third heat transfer device in thermal
communication with the thermal storage medium; and a second
thermoelectric converter with second hot side and a second cold
side, wherein the third heat transfer device is configured to
transmit heat from the second hot side into the thermal storage
medium.
39. The apparatus of claim 38, further comprising at least one fin
in thermal communication with the second cold side.
40. The apparatus of claim 38, further comprising a forced air
source in thermal communication with the second cold side.
41. The apparatus of claim 40, wherein the force air source
comprises a fan.
42. The apparatus of claim 38, wherein the thermal storage medium
comprises at least one of: i) water, ii) paraffin, iii) a molten
salt and iv) a reversible exothermic hydration material.
43. The apparatus of claim 31, wherein the first fluid comprises at
least one of water and air.
44. The apparatus of claim 31, further comprising: a baffle
disposed in the housing and configured to partially separate the
third fluid into a first portion and a second portion; a second
thermoelectric converter with a second hot side and a second cold
side; a third heat transfer device in thermal communication with
the third fluid and in thermal communication with one of: i) the
second hot side and ii) the second cold side; and a fourth heat
transfer device in thermal communication with other of: i) the
second hot side and ii) the second cold side, wherein the fourth
heat transfer device is in thermal communication with ambient air,
and wherein the first heat transfer device and the third heat
transfer device vertically separated from one another within the
column.
45. The apparatus of claim 31, wherein the first thermoelectric
converter is a thin-film thermoelectric converter.
46. The apparatus of claim 31, wherein the first thermoelectric
converter comprises: a thermoelectric stack of thermoelement
layers, wherein each thermoelement layer comprises at least one
thermoelement; and a first fluid loop in thermal communication with
the thermoelectric stack and configured to deliver a second fluid
to the thermoelectric stack in a positive temperature gradient flow
direction of the thermoelectric stack.
47. The apparatus of claim 46, wherein the thermoelectric stack
further comprises: a plurality of constricted contacts layers,
wherein each of the constricted contact layers comprises at least
one constricted contact and wherein the constricted contact layers
alternate with thermoelement layers.
48. The apparatus of claim 46, wherein the thermoelectric stack
further comprises: a plurality of metal sheets, wherein the metal
sheets alternate with the thermoelectric layers, and wherein the
metal sheets are in thermal communication with the second
fluid.
49. The apparatus of claim 48, further comprising: at least one fin
in thermal communication with the second fluid and at least one of
the plurality of metal sheets.
50. The apparatus of claim 46, wherein each of the at least one
thermoelement comprises at least one of: i)
Bi.sub.0.5Sb.sub.1.5Te.sub.3, ii) Zn.sub.4Sb.sub.3, iii)
CeFe.sub.3.5Co.sub.0.5Sb.sub.12, iv) Yb.sub.14MnSb.sub.11, v)
MnSi.sub.1.73, vi) NaCo.sub.2O.sub.4, vii) B-doped Si, viii)
B-doped Si.sub.0.8Ge.sub.0.2, ix) Bi.sub.2Te.sub.2.8Se.sub.0.2, x)
PbTe, xi) AgPb.sub.18SbTe.sub.20, xii) PbTe/SrTe--Na, xiii)
Ba.sub.0.08Yb.sub.0.09Co.sub.4Sb.sub.12, xiv)
Mg.sub.2Si.sub.0.4Sn.sub.0.6, xv) TiNiSn, xvi) SrTiO.sub.3, xvii)
P-doped Si, xviii) P-doped Si.sub.0.8Ge.sub.0.2, xix)
La.sub.3Te.sub.4, xx) CoSb.sub.3, xxi) Yb-doped CoSb.sub.3, xxii)
Mg.sub.2Si, xxiii) CePd.sub.3, and xxiv) YbAl.sub.3.
51. The apparatus of claim 50, wherein at least one of the at least
one thermoelement comprises at least one of: i) B-doped Si, ii)
P-doped Si, iii) CoSb.sub.3, iv) Yb-doped CoSb.sub.3, v)
Mg.sub.2Si, vi) CePd.sub.3, and vii) YbAl.sub.3.
52. The apparatus of claim 46, wherein the at least one
thermoelement comprises at least one of: an n-type thermoelement
and a p-type thermoelement.
53. The apparatus of claim 46, wherein the at least one
thermoelement comprises an n-type thermoelement and a p-type
thermoelement.
54. The apparatus of claim 46, wherein the second fluid comprises
at least one of: i) water, ii) steam, iii) mineral oil, iv)
terphenyl, and v) a liquid metal.
55. The apparatus of claim 46, wherein the thermoelectric stack is
an n-type thermoelectric stack, and further comprising: a p-type
thermoelectric stack, wherein the p-type thermoelectric stack is in
thermal communication with the first fluid loop and configured to
deliver the second fluid to the p-type thermoelectric stack in a
positive temperature gradient flow direction of the p-type
thermoelectric stack.
56. The apparatus of claim 46, wherein the thermoelectric stack is
an n-type thermoelectric stack and further comprising: a p-type
thermoelectric stack; and a second fluid loop in thermal
communication with the p-type thermoelectric stack and configured
to deliver a third fluid to the p-type thermoelectric stack in a
positive temperature gradient flow direction of the p-type
thermoelectric stack.
57. A thermoelectric heat pump apparatus, the apparatus comprising:
a plurality of thermoelectric converters, each having a hot side
and a cold side and comprising: a stack of thermoelement layers,
wherein each thermoelement layer comprises at least one
thermoelement; and a first fluid loop in thermal communication with
the plurality of stacks and configured to deliver a first fluid to
the stacks in a positive temperature gradient flow direction.
58. The apparatus of claim 57, wherein the plurality of
thermoelectric converters comprises a first thermoelectric
converter and a second thermoelectric converter, and the first
fluid loop is configured to recirculate a first part of the fluid
from the cold side of the first thermoelectric through the first
thermoelectric converter and to circulate a second part of the
fluid from the cold side of the first thermoelectric to the cold
side of the second thermoelectric converter.
59. The apparatus of claim 58, further comprising: at least one
heat exchanger in thermal communication with the first fluid loop
and a heat transfer device.
60. The apparatus of claim 59, wherein the heat transfer device is
a second fluid loop.
61. The apparatus of claim 59, wherein the heat transfer device
comprises a thermal diode.
62. An apparatus for moving heat relative to a first fluid, the
apparatus comprising: a housing configured to store the first
fluid; a first heat exchanger loop in thermal communication with
the first fluid and configured to move a first heat transfer fluid;
a second heat exchanger loop in thermal communication with ambient
air and configured to move a second heat transfer fluid; and a
thermoelectric converter with a hot side and a cold side, wherein
the hot side is in thermal communication with one of the first heat
exchanger loop and the second heat exchanger loop and the cold side
is in thermal communication with the other of the first heat
exchanger loop and the second heat exchanger loop.
63. The apparatus of claim 62, wherein the housing is thermally
insulated.
64. The apparatus of claim 62, wherein at least one of the heat
exchanger loops is in thermal communication with a heat
exchanger.
65. The apparatus of claim 62, further comprising: a resistance
heater in thermal communication with the first fluid.
66. The apparatus of claim 62, further comprising a forced air
source in thermal communication with at least one of the heat
exchanger loops.
67. The apparatus of claim 66, wherein the forced air source
comprises a fan.
68. The apparatus of claim 62, further comprising: a thermal
storage medium, wherein the first heat exchanger loop is in thermal
communication with the thermal storage medium.
69. The apparatus of claim 68, wherein the thermal storage medium
comprises at least one of: i) water, ii) paraffin, iii) a molten
salt and iv) a reversible exothermic hydration material.
70. The apparatus of claim 62, wherein the first fluid comprises at
least one of: water and air.
71. The apparatus of claim 62, wherein the thermoelectric converter
is a thin-film thermoelectric converter.
72. The apparatus of claim 62, wherein the thermoelectric converter
comprises: a thermoelectric stack of thermoelement layers, wherein
each thermoelement layer comprises at least one thermoelement; and
a first counter-flow fluid loop in thermal communication with the
thermoelectric stack and configured to deliver a first counter-flow
fluid to the thermoelectric stack in a positive temperature
gradient flow direction of the thermoelectric stack.
73. The apparatus of claim 72, wherein the thermoelectric stack
further comprises: a plurality of constricted contacts layers,
wherein each of the constricted contact layers comprises at least
one constricted contact and wherein the constricted contact layers
alternate with thermoelement layers.
74. The apparatus of claim 72, wherein the thermoelectric stack
further comprises: a plurality of metal sheets, wherein the metal
sheets alternate with the thermoelectric layers, and wherein the
metal sheets are in thermal communication with the first
counter-flow fluid.
75. The apparatus of claim 74, further comprising: at least one fin
in thermal communication with the first counter-flow fluid and at
least one of the plurality of metal sheets.
76. The apparatus of claim 72, wherein each of the at least one
thermoelement comprises at least one of: i)
Bi.sub.0.5Sb.sub.1.5Te.sub.3, ii) Zn.sub.4Sb.sub.3, iii)
CeFe.sub.3.5Co.sub.0.5Sb.sub.12, iv) Yb.sub.14MnSb.sub.11, v)
MnSi.sub.1.73, vi) NaCo.sub.2O.sub.4, vii) B-doped Si, viii)
B-doped Si.sub.0.8Ge.sub.0.2, ix) Bi.sub.2Te.sub.2.8Se.sub.0.2, x)
PbTe, xi) AgPb.sub.18SbTe.sub.20, xii) PbTe/SrTe--Na, xiii)
Ba.sub.0.08Yb.sub.0.09Co.sub.4Sb.sub.12, xiv)
Mg.sub.2Si.sub.0.4Sn.sub.0.6, xv) TiNiSn, xvi) SrTiO.sub.3, xvii)
P-doped Si, xviii) P-doped Si.sub.0.8Ge.sub.0.2, xix)
La.sub.3Te.sub.4, xx) CoSb.sub.3, xxi) Yb-doped CoSb.sub.3, xxii)
Mg.sub.2Si, xxiii) CePd.sub.3, and xxiv) YbAl.sub.3.
77. The apparatus of claim 76, wherein at least one of the at least
one thermoelement comprises at least one of: i) B-doped Si, ii)
P-doped Si, iii) CoSb.sub.3, iv) Yb-doped CoSb.sub.3, v)
Mg.sub.2Si, vi) CePd.sub.3, and vii) YbAl.sub.3.
78. The apparatus of claim 72, wherein the at least one
thermoelement comprises at least one of: an n-type thermoelement
and a p-type thermoelement.
79. The apparatus of claim 72, wherein the at least one
thermoelement comprises an n-type thermoelement and a p-type
thermoelement.
80. The apparatus of claim 72, wherein the first counter-flow fluid
comprises at least one of: i) water, ii) steam, iii) mineral oil,
iv) terphenyl, and v) a liquid metal.
81. The apparatus of claim 72, wherein the thermoelectric stack is
an n-type thermoelectric stack, and further comprising: a p-type
thermoelectric stack, wherein the p-type thermoelectric stack is in
thermal communication with the first counter-flow fluid loop and
configured to deliver the first counter-flow fluid to the p-type
thermoelectric stack in a positive temperature gradient flow
direction of the p-type thermoelectric stack.
82. The apparatus of claim 72, wherein the thermoelectric stack is
an n-type thermoelectric stack and further comprising: a p-type
thermoelectric stack; and a second counter-flow fluid loop in
thermal communication with the p-type thermoelectric stack and
configured to deliver a second counter-flow fluid to the p-type
thermoelectric stack in a positive temperature gradient flow
direction of the p-type thermoelectric stack.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Provisional U.S.
Patent Application No. 61/644,187, filed May 8, 2012, and
Provisional U.S. Patent Application No. 61/764,459, filed Feb. 13,
2013, both of which are hereby incorporated by reference in their
entirety.
BACKGROUND OF THE DISCLOSURE
[0002] 1. Field of the Disclosure
[0003] The present disclosure relates to an apparatus and method
for heat transfer using a thermoelectric device, and, in
particular, pumping heat.
[0004] 2. Description of the Related Art
[0005] Space heating and cooling is the largest energy end use in
homes, and water heating is the second largest energy end use in
homes. Almost every household has at least one water heater, and
about 10 percent of households replace their water heaters every
year. Gas water heaters require a gas source, which is not always
available. More than half of the water heaters are electrically
powered. Most electric water heaters are inefficient and expensive
to operate due to their resistive element heating design. An
alternative to gas and electric heating and cooling, both for water
and interiors is a heat pump-based heating and/or cooling
system.
[0006] In the instance of a water heater, typical heat pumps use a
compressor to pump heat from ambient air to the water. However, the
choice of refrigerants for compressor heat pumps is limited by the
refrigerants' critical temperature. High temperature refrigerants,
such as R134A, may operate with a critical temperature of 100
degrees Celsius at 4 Bar, or R410A with a critical temperature of
70 degrees Celsius. Since the water is commonly heated to about 70
degrees Celsius, the refrigerants must be compressed at
temperatures near their critical temperatures, a process that
requires more energy as the critical temperature is approached. The
compressor needs to compress at a significantly higher pressure for
the refrigerant to change phase and results in loss of energy
efficiency. In most cases, the compressor-based heat pump water
heaters are supplemented with a strip heater (resistive heater) to
attain the high temperature delivery requirements of the water
heater, and results in an overall decrease of system Coefficient of
Performance (COP). Secondly, the variable speed compressors that
can operate at these high water delivery temperatures are too
expensive. The retail price of commercially-available 50 gallon
water heaters is typically US$1700, compared to only US$350 for the
same capacity strip heater based product. This cost difference of
almost US$1400 implies the payback period is typically over 4 years
(based on DoE's ENEGRY STAR estimated energy savings of
approximately US$300 per year). As a result of this large
difference between the initial price of a resistive heater based
water heater and the heat pump water heater, the penetration rate
of heat pump water heaters into the water heater market has been
very low. What is needed is a cost effective heat pump that
operates efficiently at the desired temperatures, such as for high
hot water delivery temperatures.
BRIEF SUMMARY OF THE DISCLOSURE
[0007] In aspects, the present disclosure is related to an
apparatus and method for transferring heat, and, in particular, a
pumping of heat using a thermoelectric generator.
[0008] One embodiment according to the present disclosure includes
a thermoelectric heat pump apparatus, the apparatus comprising: a
thermoelectric converter having a hot side and a cold side, the
thermoelectric converter comprising: a thermoelectric stack of
thermoelement layers, wherein each thermoelement layer comprises at
least one thermoelement; and a first fluid loop in thermal
communication with the thermoelectric stack and configured to
deliver a first fluid to the thermoelectric stack in a positive
temperature gradient flow direction of the thermoelectric stack.
The thermoelectric stack may include one or more of: a plurality of
constricted contacts layers, wherein each of the constricted
contact layers comprises at least one constricted contact and
wherein the constricted contact layers alternate with thermoelement
layers, and a plurality of metal sheets, wherein the metal sheets
alternate with the thermoelectric layers, and wherein the metal
sheets are in thermal communication with the first fluid, either
directly or via heat conducting fins.
[0009] The thermoelements may be comprised of high power factor
materials such as: i) Bi.sub.0.5Sb.sub.1.5Te.sub.3, ii)
Zn.sub.4Sb.sub.3, iii) CeFe.sub.3.5Co.sub.0.5Sb.sub.12, iv)
Yb.sub.14MnSb.sub.11, v) MnSi.sub.1.73, vi) NaCo.sub.2O.sub.4, vii)
B-doped Si, viii) B-doped Si.sub.0.8Ge.sub.0.2, ix)
Bi.sub.2Te.sub.2.8Se.sub.0.2, x) PbTe, xi) AgPb.sub.18SbTe.sub.20,
xii) PbTe/SrTe--Na, xiii) Ba.sub.0.08Yb.sub.0.09Co.sub.4Sb.sub.12,
xiv) Mg.sub.2Si.sub.0.4Sn.sub.0.6, xv) TiNiSn, xvi) SrTiO.sub.3,
xvii) P-doped Si, xviii) P-doped Si.sub.0.8Ge.sub.0.2, xix)
La.sub.3Te.sub.4, xx) CoSb.sub.3, xxi) Yb-doped CoSb.sub.3, xxii)
Mg.sub.2Si, xxiii) CePd.sub.3, and xxiv) YbAl.sub.3. In some
aspects, the thermoelements may be comprised of high power factor
materials with high thermal conductivity such as: i) B-doped Si,
ii) P-doped Si, iii) CoSb.sub.3, iv) Yb-doped CoSb.sub.3, v)
Mg.sub.2Si, vi) CePd.sub.3, and vii) YbAl.sub.3. The thermoelements
may be n-type or p-type and, sometimes, pairs n-type and p-type
materials. The first fluid may include one or more of: i) water,
ii) steam, iii) mineral oil, iv) terphenyl, and v) a liquid metal.
In aspects where a thermoelectric stack is made of a single type of
thermoelectric material, a second stack of the complementing type
(p-type for n-type, and vise versa) may be used with a shared or
separate fluid loop.
[0010] The thermoelectric heat pump apparatus may include a hot
side fluid loop in thermal communication with the hot side and a
cold side fluid loop in thermal communication with the cold side.
One or more heat exchangers may be in thermal communication with
the hot/cold side fluid loops. One of the hot/cold fluid loops may
be in thermal communication with ambient while the other is in
thermal communication with a receiver of heat/cold, such as a tank
or compartment.
[0011] The receiver of the heat/cold may be a fluid stored in
housing and one or more heat transfer devices may be used to move
heat between the fluid and the ambient air. The apparatus may
include a thermal storage medium configured to be "charged" with
heat/cold so that heat movement may continue when the
thermoelectric converter is not operating or to supplement
operation of the thermoelectric converter. The thermal storage
medium may be associated with one or more additional heat transfer
devices and thermoelectric converters to move heat between the
thermal storage medium and ambient. The thermal storage medium may
include one or more of: i) water, ii) paraffin, iii) a molten salt
and iv) a reversible exothermic hydration material.
[0012] In some aspects, the housing may further include a baffle
disposed in the housing and configured to partially separate the
third fluid into a first portion and a second portion; a second
thermoelectric converter with a second hot side and a second cold
side; a third heat transfer device in thermal communication with
the third fluid and in thermal communication with one of: i) the
second hot side and ii) the second cold side; and a fourth heat
transfer device in thermal communication with other of: i) the
second hot side and ii) the second cold side, wherein the fourth
heat transfer device is in thermal communication with ambient air,
and wherein the first heat transfer device and the third heat
transfer device vertically separated from one another within the
column.
[0013] Another embodiment according to the present disclosure may
include an apparatus for transferring heat to a first fluid, the
apparatus comprising: a housing configured to store the first
fluid; a first heat transfer device configured to be in thermal
communication with the first fluid; a first thermoelectric
converter with a first hot side and a first cold side, wherein the
first hot side is in thermal communication with the first heat
transfer device, and wherein the first heat transfer device is
configured to transmit heat from the first hot side to the first
fluid; and a second heat transfer device in thermal communication
with the first cold side, and wherein the second heat transfer
device is in thermal communication with ambient air and configured
to transmit the cold from the first cold side to the ambient
air.
[0014] Another embodiment according to the present disclosure may
include a thermoelectric heat pump apparatus, the apparatus
comprising: a plurality of thermoelectric converters, each having a
hot side and a cold side and comprising: a stack of thermoelement
layers, wherein each thermoelement layer comprises at least one
thermoelement; and a first fluid loop in thermal communication with
the plurality of stacks and configured to deliver a first fluid to
the stacks in a positive temperature gradient flow direction. The
plurality of thermoelectric converters may comprise a first
thermoelectric converter and a second thermoelectric converter, and
the first fluid loop is configured to recirculate a first part of
the fluid from the cold side of the first thermoelectric through
the first thermoelectric converter and to circulate a second part
of the fluid from the cold side of the first thermoelectric to the
cold side of the second thermoelectric converter. The
thermoelectric heat pump apparatus may include at least one heat
exchanger in thermal communication with the first fluid loop and a
heat transfer device, and that heat transfer device may include one
or more of: a second fluid loop and a thermal diode.
[0015] Another embodiment according to the present disclosure
includes an apparatus for moving heat relative to a first fluid,
the apparatus comprising: a housing configured to store the first
fluid; a first heat exchanger loop in thermal communication with
the first fluid and configured to move a first heat transfer fluid;
a second heat exchanger loop in thermal communication with ambient
air and configured to move a second heat transfer fluid; and a
thermoelectric converter with a hot side and a cold side, wherein
the hot side is in thermal communication with one of the first heat
exchanger loop and the second heat exchanger loop and the cold side
is in thermal communication with the other of the first heat
exchanger loop and the second heat exchanger loop.
[0016] Examples of the more important features of the disclosure
have been summarized rather broadly in order that the detailed
description thereof that follows may be better understood and in
order that the contributions they represent to the art may be
appreciated. There are, of course, additional features of the
disclosure that will be described hereinafter and which will form
the subject of the claims appended hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] For a detailed understanding of the present disclosure,
reference should be made to the following detailed description of
the embodiments, taken in conjunction with the accompanying
drawings, in which like elements have been given like numerals,
wherein:
[0018] FIG. 1 a schematic thermoelectric fluid heater according to
one embodiment of the present disclosure;
[0019] FIG. 2 is a schematic of a thermoelectric fluid heater with
resistive heating element according to one embodiment of the
present disclosure;
[0020] FIG. 3 is a schematic of a thermoelectric fluid heater with
a thermal battery according to one embodiment of the present
disclosure;
[0021] FIG. 4 is a schematic of a thermoelectric fluid heater with
a thermal battery with fluid loops to transport heat according to
one embodiment of the present disclosure;
[0022] FIG. 5 is a schematic of a thermoelectric fluid heater with
convection induced by thermoelectric converters according to one
embodiment of the present disclosure;
[0023] FIG. 6 is a schematic of a thermoelectric converter
apparatus with a counter-flow fluid loop adjacent to the apparatus
according to one embodiment of the present disclosure;
[0024] FIG. 7 is a schematic of a thermoelectric converter
apparatus with a counter-flow fluid loop flow path through the
thermoelements according to one embodiment of the present
disclosure;
[0025] FIG. 8 is a 3-D perspective view of a single type
thermoelement stack with a counter-flow fluid through the
thermoelements according to one embodiment of the present
disclosure;
[0026] FIG. 9A is a schematic of an air heater using a
thermoelectric converter apparatus according to one embodiment of
the present disclosure;
[0027] FIG. 9B is a schematic of a water heater using a
thermoelectric converter apparatus according to one embodiment of
the present disclosure; and
[0028] FIG. 10 is a schematic of a cooling system using a
thermoelectric converter apparatus according to one embodiment of
the present disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0029] Generally, the present disclosure relates to an apparatus
and method for transferring heat, and, in particular, pumping heat
with a thermoelectric converter. The present disclosure is
susceptible to embodiments of different forms. They are shown in
the drawings, and herein will be described in detail, specific
embodiments of the present disclosure with the understanding that
the present disclosure is to be considered an exemplification of
the principles of the present disclosure and is not intended to
limit the present disclosure to that illustrated and described
herein.
[0030] The optimum COP for a thermoelectric converter for cooling
operation is defined as the ratio of heat pumped from the cold side
to hot side of the cooler to the input electrical power. The
optimal COP is determined by the following relationship:
COP opt = ( T .DELTA. T ) [ 1 + ZT avg - T h / T c 1 + ZT avg + 1 ]
##EQU00001##
where T.sub.c and T.sub.h are the temperatures of the cold side and
hot side respectively, ZT is a dimensionless parameter known as
figure-of-merit, which combines the thermoelectric properties of
the material, T.sub.avg=(T.sub.c+T.sub.h)/2 and
.DELTA.T=T.sub.h-T.sub.c.
[0031] The heat rejected by the thermoelectric converter into the
fluid Q.sub.f depends on the input electrical power (P.sub.elec) as
follows:
Q.sub.f=P.sub.elec(1+COP.sub.opt)
These equations may be used to estimate the heat pump requirements
for heating a fluid, such as water or air, to a target delivery
temperature.
[0032] FIG. 1 shows a schematic of an apparatus 100 for heating a
fluid 160 according to one embodiment of the present disclosure.
The apparatus 100 may include a housing 110 designed to store the
fluid 160. The fluid 160 may be a liquid or a gas. The fluid 160
may include, but is not limited to, one or more of: water,
paraffin, air, and petroleum fractions. The housing 110 may include
a structural layer 116, such as stainless steel or ceramic, that
will not be corroded or degraded by the fluid 160. The housing 110
may include a tank or other structure that forms a compartment or
chamber to hold the fluid 160. The housing 110 may also include
thermal insulation 118. The housing 110 may include an inlet 114
and an outlet 112 for the fluid 160 to enter and leave the housing
110. A heat transfer device 120 may be disposed in the housing 110
such that the heat transfer device 120 is in thermal, and often
physical, communication with the fluid 160. Heat fins 122 may be
attached to the heat transfer device 160 to increase the
distribution of heat from the heat transfer device 120 into the
fluid 160. The heat transfer device 120 may be any suitable device
configured to transport heat energy including, but not limited to,
one or more of: i) a heat pipe, ii) a thermosyphon, iii) a thermal
diode, and iv) a heat exchanger. The heat transfer device 120 may
be in thermal connection with a hot side 132 of a thermoelectric
converter 130. The thermoelectric converter 130 may be configured
to produce a temperature differential between the hot side 132 and
a cold side 134 in response to electrical power received from a
power source 170. The thermoelectric converter 130 may be a
thin-film thermoelectric device. In some embodiments, the
thermoelectric converter 130 may include multiple thermoelectric
devices in parallel and/or series configuration. In some other
embodiments, the thermoelectric converter 130 may comprises of
cascaded or segmented thermoelectric devices. The thermoelectric
converter 130 may be disposed in the housing 110 such that the hot
side 132 is inside the thermal insulation 118 and the cold side 134
is outside of the thermal insulation 118. A heat transfer device
140 may be disposed in thermal communication with the cold side 134
to move heat into the cold side 134 of the thermoelectric converter
from the ambient The heat transfer device 140 may include fins 142
configured to gather heat from the ambient air. In some
embodiments, the ambient air may be moved through the fins 142 by a
forced air supply 150, such as a fan.
[0033] As would be understood by a person of ordinary skill in the
art with the benefit of the present disclosure, there may be a
variety of embodiments in keeping with the design shown in FIG. 1.
For example, in an aspect of air heating, the housing 110 may be
the walls, floor, and ceiling of a room that hold a volume of air
to be heated. In some embodiments, the housing 110 may not be
enclosing, such as in the case of a vat. In some embodiments, one
or more of the heat transfer devices 120, 140 may be optional, and
the fins 122, 142 may be in thermal communication with the hot and
cold sides 132, 134, respectively. While the thermoelectric
converter 130 is shown as singular and disposed at the bottom of
the housing 110, this is exemplary and illustrative only, as there
may be multiple thermoelectric converters 130 and the
thermoelectric converters 130 may be disposed anywhere within the
housing 110 so long as heat may be transferred between the inside
and the outside of the housing 110. The thermoelectric converters
130 may be staged in series or parallel or both as desired to
provide a specified heat differential or amount of heat flow
between the fluid 160 and the ambient air.
[0034] FIG. 2 shows a schematic of an apparatus 200 for heating a
fluid 160 according to another embodiment of the present
disclosure. The apparatus 200 includes the elements of apparatus
100 in FIG. 1 and, additionally, includes a resistive heating
element 210. The resistive heating element 210 may receive
electricity from the power source 170 (connections between the
power source and the resistive heating element not shown). The
resistive heating element 210 may be configured to supplement the
heat energy being provided to the fluid 160 by the thermoelectric
converter 130. The resistive heating element 210 is configured to
provide heat to the fluid 160 independently or in combination with
the thermoelectric converter 130. In some embodiments, the
thermoelectric converter can heat and maintain the fluid 160 at a
pre-determined temperature and the resistive heater can be used
only when a higher fluid temperature is desired.
[0035] FIG. 3 shows a schematic of another apparatus 300 for
heating the fluid 160 according to another embodiment of the
present disclosure. The apparatus 300 may include elements from
apparatus 100 shown in FIG. 1. The apparatus 300 may include a
thermal storage medium 310 that may be stored in a housing 320. The
thermal storage medium 310 (such as a thermal battery) may include
substances with high heat capacity that remain liquid in the
operating temperature range of the fluid 160, including, but not
limited to, one or more of: water, paraffin, and molten salts. In
some embodiments, the thermal storage medium 310 may include
substances suitable for a reversible exothermic chemical reaction.
The thermal storage medium 310 may be selected based on the heating
temperature range selected for the desired fluid 160. The heat
transfer device 140 may be in thermal communication with the
thermal storage medium 310. Heat may be supplied from the thermal
storage medium 310 through the heat transfer device 140 to the cold
side 134 of the thermoelectric converter 130. Another heat transfer
device 330 may be disposed in thermal communication with the
thermal storage medium 310 and configured to transport heat into
the thermal storage medium 310. The heat transfer device 330 may be
in thermal communication with a hot side 342 of another
thermoelectric converter 340. The heat transfer device 330 may
include fins 332 configured to distribute heat into the thermal
storage medium 310. A cold side 344 of the thermoelectric converter
340 may be in thermal communication with the ambient air to gather
heat. Fins 350 in thermal communication with the cold side 344 may
be used to increase the surface area of ambient air to increase
heat gathering. In some embodiments, heat gathering may be increase
using the forced air supply 150. The thermoelectric converter 340
may charge the thermal storage medium 310 while the thermoelectric
converter 130 moves heat from the storage medium to the fluid 160.
The heat transfer device 330 may be diodic in nature, which allows
the heat to predominately move in one direction from the hot side
342 to the thermal storage medium 330.
[0036] FIG. 4 shows a schematic of an apparatus 400 for heating
fluid 160 according to another embodiment of the present
disclosure. A heat exchanger 410 may be disposed in thermal
communication with the fluid 160 to convey heat into the fluid 160.
The heat exchanger 410 may receive heat from a first pumped loop
420 containing a heat transfer fluid, such as water or oil. The
first pumped loop 420 may be in thermal communication with a hot
side 432 of a thermoelectric converter 430, which is configured to
supply heat to the first pumped loop 420. A cold side 434 of the
thermoelectric converter 430 may be in thermal communication with a
second pumped loop 440 that is configured to transport heat to the
cold side 434 from an ambient air heat exchanger 450. In some
embodiments, a forced air source 460 may enhance the transfer of
heat from the ambient air into the ambient air heat exchanger 450.
In some embodiments, the first pumped loop 420 may circulate
through thermal storage medium 310 (such as a thermal battery) via
a heat exchanger loop 470. The thermal storage medium 310 may be
configured to store or release heat into the first pumped loop 420
as is required to provide the desired temperature for the fluid
160. In some embodiments, the housing 320 may be at least partially
enclosed by thermal insulation 480.
[0037] Some embodiments of apparatus 400 may be configured to
operate in at least three different modes. In a first mode, the
thermoelectric converter 130 may move heat to the fluid 160. In a
second mode, the thermoelectric converter 130 may move heat to the
thermal storage medium 310. In a third mode, the thermal storage
medium 310 may be used to move heat to the fluid 160. In the third
mode, the thermoelectric converter 130 and the second pumped loop
may not be operating. One or more valves and/or pumps in the pumped
loops 420, 440 may be configured to for performance of each of the
three modes.
[0038] Although the embodiments shown above depict only a single
thermoelectric heat pump, in practice the design may include
multiple thermoelectric heat pumps connected thermally in parallel
and electrically in series or parallel or series/parallel
configuration (depending upon the desired voltage-current
characteristics). Also there are many different types of heat
exchangers that can be incorporated. An exemplary heat exchanger
may include a counter flow configuration of fluid flow.
[0039] FIG. 5 shows a schematic of a fluid heating apparatus 500
configured to incorporate convection induced mass flow in the fluid
160 to facilitate heat pumping according to one embodiment of the
present disclosure. The apparatus 500 may include several elements
of apparatus 100 shown in FIG. 1. An inlet conduit 514 may be
disposed to provide the fluid 160 into the bottom of the housing
110. Since the incoming fluid through the conduit 514 is colder,
this configuration supports natural convection in the chamber. The
housing 110 may be at least partially partitioned by a baffle 510
to form a column 520 of the fluid 160 between the baffle 510 and a
wall of the housing 110. One or more thermoelectric converters 130
may be disposed in the housing 110 and configured to pump heat into
the fluid 160 through heat transfer devices 120 and fins 122. The
heat transfer devices 120 and fins 122 may be disposed in the
column 120. Some fluids, such as water, change density with changes
in temperature. The heat added to the fluid 160 from the heat
transfer devices 120 and fins 122 will cause the local temperature
of the fluid 160 to increase and induce movement in the fluid 160
due to density changes. The baffle 510 may channel this induced
movement into a direction along the column 520. With multiple
thermoelectric converters 130 pumping heat into heat transfer
devices 120 and fins 122 in thermal communication with the column
520, a flow (due to the changes in density of the fluid 160) may
produce circulation throughout the fluid 160 within the housing
110.
[0040] In some embodiments, the heat transfer device 120 or the
fins 122 may be optional. In the inlet pipe 514 is shown delivering
fluid at the bottom of the baffle 510, however, this is exemplary
and illustrative only, as the inlet pipe 514 may deliver fluid
anywhere in the housing 110, such as at the top of the baffle 510.
As one of ordinary skill in the art would understand with the
benefit of the present disclosure, apparatus 500 may be modified to
transfer heat out of the fluid 160, in which case, the fluid
circulation path would be reversed as the cooled fluid would sink
rather than rise. In such cases, multiple thermoelectric converters
may be removing heat from the fluid 160 to the ambient (instead as
pumping heat into the fluid) thus causing the coldest and the
densest portions of the fluid 160 to settle in the bottom of the
apparatus 110.
[0041] A person of ordinary skill in the art with the benefit of
the present disclosure would understand that by reversing the heat
flow of some of the elements, the direction of heat pumping may be
reversed to cause a cooling of the fluid 160. In a cooling
configuration, the thermal storage medium 310 may include materials
that are suitable for an appropriate temperature range for cooling
the fluid 160.
[0042] In some aspects, the thermoelectric converter 130 may
include its own fluid loop, herein referred to as a counter-flow
fluid loop. The counter-flow fluid loop may be circulated by a
mechanical or electromagnetic pump system, which may be selected
based on the counter-flow fluid used in the loop. The application
of the counter-flow fluid is to reduce phonon conduction in
thermoelements of the thermoelectric device, wherein counter-flow
refers to a flow in the direction of a positive temperature
gradient. The coupled fluid flow may alter the temperature and heat
flow profiles of a thermoelectric device without affecting electron
transport. This alteration may increase the efficiency of the
counter-flow thermoelectric devices (FLO-TEs).
[0043] The counter-flow includes a fluid in thermal communication
with the thermoelements. Suitable counter-flow fluids have good
heat capacity, good thermal conductance, and low viscosity.
Exemplary and non-limiting counter-flow fluids may include water,
an ethylene glycol-water mixture, mineral oil, terphenyl, and
liquid metal. The counter-flow fluid may be selected depending on
the application of the thermoelectric device and other limitations,
such as operating temperature ranges.
[0044] Many thermoelectric materials are selected for their high ZT
values, where ZT=.sigma.S.sup.2T/.lamda., and .sigma.S.sup.2 is
referred to as the power factor of the thermoelectric material,
while .lamda. is the thermal conductivity of the material. Thus, in
order to have a high ZT, typical thermoelectric materials must have
a high enough power factor to offset the thermal conductivity
component. The FLO-TE is not limited by the thermoelectric
figure-of-merit ZT, and, thus, may attain efficiencies approaching
the Carnot limit.
[0045] The performance of FLO-TE devices may be understood though
the effect of several dimensionless parameters on thermoelectric
device performance. The first dimensional parameter is:
.beta.=.rho.vcel/.lamda.={dot over (m)}c/k
where .rho. is density, v is velocity, c is heat capacity of the
counter-flow fluid, l is length of the TE stack, .lamda. is thermal
conductivity of the TE stack, {dot over (m)} is the mass flow rate
of the counter-flow fluid and k is the thermal conductance of a
stack of TE modules. When .beta.>2, there may be significant
reduction of the phonon conduction. When .beta.>2, the
coefficient of performance fl of the FLO-TE device is given by
.eta. = J qc J qh - J qc .apprxeq. T c .DELTA. T + JI .sigma. S = T
c .DELTA. T + IR S ( 1 ) ##EQU00002##
where J.sub.qc and J.sub.qh are the heat flux density at the cold
and hot ends of the device, T.sub.c is the temperature at the cold
end, .DELTA.T is the temperature differential across the FLO-TE,
.sigma. is the electrical conductivity of the TE material, S is the
Seebeck coefficient of the thermoelectric material, R is the
electrical resistance of the stack of TE module, and I is the
current through the stack of the TE module. As would be understood
by a person of ordinary skill in the art with the benefit of the
present disclosure, the FLO-TE material may include a substance
that is selected on the basis of power factor and that has a high
thermal conductivity, since the effects of the phonon conduction
are mitigated when .beta.>2. For example, ytterbium aluminate
(YbAl.sub.3) has a high power factor but also a high thermal
conductivity. When .beta.>2, the thermal conductivity of
YbAl.sub.3 decreases in the FLO-TE, and, now YbAl.sub.3 is quite
suitable for use as a thermoelectric material because of its high
ZT value when .beta.>2. Typical thin-film thermoelectric
materials may include, but are not limited to, the materials listed
in Table 1.
TABLE-US-00001 TABLE 1 P-Type Thermoelectric N-Type Thermoelectric
Operating Temperature Material Material (degrees C.)
Bi.sub.0.5Sb.sub.1.5Te.sub.3 Bi.sub.2Te.sub.2.8Se.sub.0.2 -50 to
250 Zn.sub.4Sb.sub.3 PbTe 250 to 450 AgPb.sub.18SbTe.sub.20
PbTe/SrTe--Na CeFe.sub.3.5Co.sub.0.5Sb.sub.12
Ba.sub.0.08Yb.sub.0.09Co.sub.4Sb.sub.12 400 to 650
Yb.sub.14MnSb.sub.11 Mg.sub.2Si.sub.0.4Sn.sub.0.6 500 to 700
MnSi.sub.1.73 TiNiSn NaCo.sub.2O.sub.4 SrTiO.sub.3 B-doped Si
P-doped Si 600 to 1000 B-doped Si.sub.0.8Ge.sub.0.2 P-doped
Si.sub.0.8Ge.sub.0.2 La.sub.3Te.sub.4
Exemplary FLO-TE materials may include the materials in Table 1,
and, additionally, the high power factor materials such as, but not
limited to, the materials listed in Table 2.
TABLE-US-00002 TABLE 2 P-Type Thermoelectric N-Type Thermoelectric
Operating Temperature Material Material (degrees C.) B-doped Si
P-doped Si 0 to 1000 CoSb.sub.3 Yb-doped CoSb.sub.3 200 to 650
Mg.sub.2Si 400 to 700 CePd.sub.3 YbAl.sub.3 0 to 1000
[0046] For small currents (I.fwdarw.0), the COP
.eta. .fwdarw. T c .DELTA. T = .eta. C ##EQU00003##
the Carnot COP, such that the COP may vary as a function of current
I. Current I may be expressed in terms of COP as
I = ( .eta. c - .eta. .eta. ) S .DELTA. T R = .gamma. S .DELTA. T R
( 2 ) .gamma. = ( .eta. c - .eta. .eta. ) ( 3 ) ##EQU00004##
[0047] An important dimensionless parameter .THETA. that defines
the performance of FLO-TE heat pump is the ratio of thermoelectric
(Peltier) cooling Q.sub.c to the heat moved by the fluid Q.sub.f,
which may be expressed as:
.THETA. = Q c Q f = SIT c m . c .DELTA. T = .gamma. .beta. ( ZT c )
( 4 ) ##EQU00005##
[0048] .THETA. can be modified (refined) to include the effect of
imperfect coupling between the fluid and the stack of TE modules. A
refined parameter .THETA..sub.x can be expressed as:
.THETA. x = Q c Q f = SIT c e f m . c .DELTA. T = .gamma. e f
.beta. ( ZT c ) = .THETA. e f ( 5 ) ##EQU00006##
where e.sub.f is the effectiveness of the heat exchange between the
stack of TE modules and the fluid. .THETA..sub.x may be of
particular importance for refrigeration applications. An exemplary
set of dimensionless parameters values for operation at 40% of
Carnot COP of FLO-TE heat pump are as follows:
TABLE-US-00003 .eta. = 0.4.eta..sub.c .beta. = 2.0 .gamma. = 1.5
ZT.sub.c = 2 .THETA. = 1.5 .THETA..sub.x = 2.0
[0049] FIG. 6 shows a schematic of a thermoelectric apparatus 600
according to one embodiment of the present disclosure. The
apparatus 600 may include a thermoelectric stack 610 of alternating
thermoelements 630 and heat conducting layers 620. In some
embodiments, the heat conducting layers 620 may be optional. Each
of the thermoelements 630 has a hot side and a cold side, and the
thermoelements 630 are arranged in series along the thermoelectric
stack 610, such that the thermoelectric stack 610 is in thermal
communication with a hot side thermal conductor 612 and a cold side
thermal conductor 614. The hot and cold side heat conductors 612,
614, may be comprised of any suitable good thermal conductor
material, such as a metal or a ceramic. The hot side heat conductor
612 and the cold side heat conductor 614 may include openings 616
and 618, respectively that are configured to receive additional
fluid flow loops, including additional heat exchangers to move heat
into and out of the counter-flow fluid.
[0050] Each of the thermoelements 630 is configured to generate a
temperature differential in response to received electrical energy.
The thermoelements 630 include n-type thermoelements 632 and a
p-type thermoelements 634, which may be paired and disposed on a
metal layer 636. In some embodiments, there may be multiple pairs
of thermoelements 630. In some embodiments, some of the pairs 632,
634 may be segmented, that is one pair may be composed of materials
configured to operate in a first temperature range and another pair
may be composed of materials to operate at a second temperature
range. For example, a segmented thermoelectric stack may be
configured to operate one series of pairs (at least one per layer)
in a temperature range of 250-450 degrees Celsius and another
series of pairs in a temperature range of 400-650 degrees
Celsius.
[0051] The heat conducting layers 620 may be disposed between the
thermoelement layers 630 and provide heat transfer between
thermoelement layers 630 as well as to provide thermal coupling
between the thermoelements and counter-flow fluid. The heat
conducting layers 630 may be a thin metal sheet. A fluid loop 640
carrying a counter-flow fluid 650 that may flow along the
thermoelectric stack 610 and be in thermal communication with the
thermoelectric stack 610. The direction of the fluid flow is along
the positive temperature gradient, that is against (counter) to the
direction of phonon (lattice) conduction in the thermoelectric
stack, which is from the cold side 614 to the hot side 612, thus
the fluid is referred to as the counter-flow fluid 650.
[0052] The thermal communication between the counter-flow fluid 650
and the thermoelements 630 may be enhanced by disposing optional
fins 660 on the heat conducting layers 620. The fins 660 may extend
into the counter-flow fluid 650. In some embodiments, the heat
conducting layers 620 may extend into the counter-flow fluid 650.
The counter-flow fluid 650 may be any suitable heat transfer fluid,
including, but not limited to, one or more of: water, ethylene
glycol-water mixtures, mineral oil, terphenyl, and a liquid metal.
The counter-flow fluid 650 may absorb heat while traveling from the
cold side to the hot side of the thermoelements 630. Some of the
heat stored in the counter-flow fluid 630 may be transferred to the
hot side of the thermoelement 630 or to the heat conducting layer
620/fin 660 associated with the thermoelement 630.
[0053] FIG. 7 shows a schematic of another FLO-TE based apparatus
700 according to one embodiment of the present disclosure. The
apparatus 700 has many of the same elements as apparatus 600 of
FIG. 6; however, apparatus 700 includes a thermoelectric stack pair
710 that is configured so that the flow path is through the center
of the thermoelements 720 of the thermoelectric stack pair 710. The
thermoelectric stack pair may include a plurality of thermoelements
720, where one side of the thermoelectric stack pair 710 is made up
of n-type thermoelements 720n and the other side of the
thermoelectric stack pair 710 is made up of p-type thermoelements
720p. The thermoelements 720 may alternate with one or more
constricted contacts 730 disposed between adjacent layers of
thermoelements 720. Both 720p and 720a elements are disposed on
thermally conducting substrates which are stacked on one another.
These substrates are in direct contact with the counter-flow fluid,
which flows through the center of the thermoelectric stack, thereby
achieving efficient thermal coupling between the fluid and
thermoelements.
[0054] FIG. 8 shows a three-dimensional perspective of another
thermoelectric stack 800 for the apparatus 700. The thermoelements
720 may be stacked with alternating constricted contacts 730 in the
thermoelectric stack 800. The thermoelements 720 are shown as
ring-type, however, this is exemplary and illustrative, as the
thermoelements 720 may have other shapes, such as cubic,
rectangular solids, ovoid, etc. The thermoelements 720 may be all
n-type or all p-type. If the thermoelectric stack 800 is n-type,
then a complementing p-type thermoelectric stack may be paired with
the thermoelectric stack 800 to enhance performance. As shown, the
cylindrical shape of thermoelectric stack 800 allows counter-flow
fluid to pass through and/or around the thermoelectric stack 800.
The counter-flow fluid of thermoelectric stack 800 may circulate
independently from the counter-flow fluid of a complementing
thermoelectric stack.
[0055] FIG. 9A shows a schematic of an air heater 900 according to
one embodiment of the present disclosure. The air heater 900 may
include a heat pump 910. The heat pump 910 may include a FLO-TE
apparatus 700 (or an apparatus 600) that is thermal communication
with a counter-flow fluid loop 920. The cold side of the apparatus
700 may be in thermal communication with a fluid loop 930
configured to move heat from the ambient into the apparatus 700.
The fluid loop 930 may be in thermal communication with ambient air
and receive heat from the ambient air. The hot side of the
apparatus 700 may be in thermal communication with a fluid loop 940
that is configured to transport heat from the hot side of the
FLO-TE apparatus into a compartment 950 or other volume to be
heated. An optional heat exchanger 960 may be configured to
transfer heat between the section of the counter-flow fluid loop
920 entering the cold side of the apparatus 700 and the fluid loop
930. Another optional heat exchanger 970 may be configured to
transfer heat between section of the counter-flow fluid loop 920
leaving the hot side of the apparatus 700 and the fluid loop
940.
[0056] FIG. 9B shows a schematic of a water heater 980 according to
one embodiment of the present disclosure. The water heater 980 may
have substantially the same elements and configuration as the air
heater 900; however, the water heater 980 may include a water tank
990. The fluid loop 940 may be configured to pass through at least
part of the water tank 990 in order to convey heat to the water
contained therein. In one embodiment, the water tank is insulated
such that leakage to ambient of the thermal energy deposited in the
water is reduced.
[0057] FIG. 10 shows a schematic of a cooling system 1000 according
to one embodiment of the present disclosure. As one of ordinary
skill in the art would understand with the benefit of the present
disclosure, cooling may be achieved by reversing the heat flow
direction of a heating apparatus. The cooling system 1000 may
include a heat pump 1010, which comprises a counter-flow fluid loop
1020 and a FLO-TE apparatus 700a. The first stage FLO-TE apparatus
700a may be supplemented by additional FLO-TE apparatus 700b, 700c.
The number of supplementing FLO-TE apparatuses 700b, 700c may be
selected for the heat pump 1010 based on power and temperature
requirements for the heat pump 1010 as well as the parameters 3 and
.THETA..sub.x of the FLO-TE apparatuses 700b, 700c. The heat pump
1010 may be in thermal communication with a fluid 1050 to be cooled
through a heat transfer loop 1030. The heat pump 1010 may also be
in thermal communication with ambient air temperature through
another heat transfer loop 1040. Heat may be pumped from the hot
sides of the one or more apparatuses 700 to the heat transfer 1040
configured to transport heat away from the hot sides, while heat
may be pumped into the cold sides of the one or more apparatuses
700 through from the fluid loop 1030 configured to transport heat
from the fluid 1050. The fluid 1050 may be identical to suitable
substances for the fluid 160.
[0058] The first stage apparatus 700a may cool the counter-flow
fluid due to the temperature differential across the apparatus
700a, which has a hot side in thermal communication with ambient
temperature. The cooled output of cold side of the apparatus 700a
may be partially recirculated through the first stage apparatus
700a from cold side to hot side and partially circulated though a
cold side of the supplementing apparatus 700b. The, now colder
counter-flow fluid entering the cold side of the apparatus 700b may
be further cooled by apparatus 700b and again partially
recirculated through the apparatus 700b and partially circulated to
an additional supplementing apparatus 700c. The final supplementing
apparatus 700c will circulated the remaining counter-flow fluid
through the final supplementing apparatus 700c from cold side to
hot side. The use of two supplementing apparatuses 700b, 700c is
exemplary and illustrative only, as the loop configuration and
number of supplementing apparatuses may be modified to accommodate
desired efficiency, temperature differential, heat pumping, and
cost parameters. A heat exchanger 1060 may be in thermal
communication with the heat transfer loop 1030 and the counter-flow
fluid loop 1020 to remove heat from the fluid 1050. Additional heat
exchangers 1060a, 1060b, 1060c corresponding to recirculation loops
from apparatuses 700a, 700b, 700c may be used to further extract
heat from the fluid 1050. A heat exchanger 1070 may be used to
remove heat from the counter-flow fluid loop 1020 to ambient.
Additional heat exchangers (not shown) in thermal communication
with the heat transfer loop 1040 and corresponding to the
apparatuses 700 may be used to increase the heat pumping to
ambient. It must be noted that .THETA..sub.x>1.0 for the cascade
cooling so that each stage has enough cooling power to provide cold
fluid to the next stage and its own flow channel. The cascade
design can have single-stage if the temperature differentials are
small or multiple stages for large temperature differentials.
[0059] While the disclosure has been described with reference to
exemplary embodiments, it will be understood that various changes
may be made and equivalents may be substituted for elements thereof
without departing from the scope of the disclosure. In addition,
many modifications will be appreciated to adapt a particular
instrument, situation or material to the teachings of the
disclosure without departing from the essential scope thereof.
Therefore, it is intended that the disclosure not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this disclosure, but that the disclosure will include
all embodiments falling within the scope of the appended
claims.
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