U.S. patent application number 12/885757 was filed with the patent office on 2012-03-22 for solar thermoelectric power generation system, and process for making same.
Invention is credited to Joseph C. Gombarick, JR., Gregory F. Jacobs, Ming Liang Shiao.
Application Number | 20120067391 12/885757 |
Document ID | / |
Family ID | 45816615 |
Filed Date | 2012-03-22 |
United States Patent
Application |
20120067391 |
Kind Code |
A1 |
Shiao; Ming Liang ; et
al. |
March 22, 2012 |
SOLAR THERMOELECTRIC POWER GENERATION SYSTEM, AND PROCESS FOR
MAKING SAME
Abstract
A solar thermoelectric power generation system includes roofing
products such as shingles with solar heat reflective areas and
roofing products with solar heat absorptive areas. Thermoelectric
power generating elements are provided in thermal contact with the
solar heat reflective areas and the solar heat absorptive
areas.
Inventors: |
Shiao; Ming Liang;
(Collegeville, PA) ; Jacobs; Gregory F.; (Oreland,
PA) ; Gombarick, JR.; Joseph C.; (Phoenixville,
PA) |
Family ID: |
45816615 |
Appl. No.: |
12/885757 |
Filed: |
September 20, 2010 |
Current U.S.
Class: |
136/206 ;
29/890.033 |
Current CPC
Class: |
H01L 35/30 20130101;
Y10T 29/49355 20150115 |
Class at
Publication: |
136/206 ;
29/890.033 |
International
Class: |
H01L 35/02 20060101
H01L035/02; H01L 35/34 20060101 H01L035/34 |
Claims
1. A solar thermoelectric power generation system, the system
comprising: (a) a roofing shingle including at least one solar heat
reflective area; (b) a roofing shingle including at least one solar
heat absorptive area; (c) at least one thermoelectric power
generating element in thermal contact with the at least one solar
heat reflective area and the at least one solar heat absorptive
area.
2. A solar thermoelectric power generation system according to
claim 1, the at least one thermoelectric power generating element
having a first junction in thermal contact with the at least one
solar heat reflective area and a second junction in thermal contact
with the at least one solar heat absorptive area.
3. A solar thermoelectric power generation system according to
claim 1, the system comprising a roofing shingle including both at
least one solar heat reflective area and at least one solar heat
absorptive area.
4. A solar thermoelectric power generation system according to
claim 1, the at least one solar heat reflective area differing in
E* from the at least one solar heat absorptive area no more than
10.
5. A solar thermoelectric power generation system according to
claim 4, the at least one solar heat reflective area differing in
E* from the at least one solar heat absorptive area by no more than
5.
6. A solar thermoelectric power generation system according to
claim 5, the at least one solar heat reflective area differing in
E* from the at least one solar heat absorptive area no more than
2.
7. A solar thermoelectric power generating system according to
claim 1, the system including a plurality of thermoelectric power
generating elements electrically connected in series to provide a
predefined output voltage.
8. A solar thermoelectric power generating system according to
claim 1, the solar heat reflective area including solar heat
reflective roofing granules.
9. A solar thermoelectric power generating system according to
claim 1, the solar heat absorptive area including solar heat
absorptive roofing granules.
10. A solar thermoelectric power generating system according to
claim 1, further comprising thermal insulation between the solar
heat reflective area and the solar heat absorptive area.
11. A roofing product for use in a solar thermoelectric power
generating system, the roofing shingle comprising: (a) at least one
solar heat reflective area; (b) at least one solar heat absorptive
area; (c) at least one thermoelectric power generating element in
thermal contact with the at least one solar heat reflective area
and the at least one solar heat absorptive area.
12. A roofing product for use in a solar thermoelectric power
generating system according to claim 11, the at least one
thermoelectric power generating element having a first junction in
thermal contact with the at least one solar heat reflective area
and a second junction in thermal contact with the at least one
solar heat absorptive area.
13. A roofing product for use in a solar thermoelectric power
generating system according to claim 11, the at least one solar
heat reflective area differing in E* from the at least one solar
heat absorptive area by less than 10.
14. A roofing product for use in a solar thermoelectric power
generating system according to claim 13, the at least one solar
heat reflective area differing in E* from the at least one solar
heat absorptive area by less than 5.
15. A roofing product for use in a solar thermoelectric power
generating system according to claim 14, the at least one solar
heat reflective area differing in E* from the at least one solar
heat absorptive area by less than 2.
16. A roofing product for use in a solar thermoelectric power
generating system according to claim 11, the system including a
plurality of thermoelectric power generating elements electrically
connected in series to provide a predefined output voltage.
17. A roofing product for use in a solar thermoelectric power
generating system according to claim 11, the solar heat reflective
area including solar heat reflective roofing granules.
18. A roofing product for use in a solar thermoelectric power
generating system according to claim 11, the solar heat absorptive
area including solar heat absorptive roofing granules.
19. A roofing product for use in a solar thermoelectric power
generating system according to claim 11, further comprising thermal
insulation between the solar heat reflective area and the solar
heat absorptive area.
20. A method of generating electric power, the method comprising:
(a) providing a roofing product including at least one solar heat
reflective area; (b) providing a roofing product including at least
one solar heat absorptive area; (c) providing at least one
thermoelectric element in thermal contact with the at least one
solar heat reflective area and the at least one solar heat
absorptive area; (d) exposing the roofing products to solar
radiation; and (e) drawing electric current from the at least one
thermoelectric element.
21. A method according to claim 20 wherein the at least one
thermoelectric element has a first junction in thermal contact with
the at least one solar heat reflective area and a second junction
in thermal contact with the at least one solar heat absorptive
area.
22. A process for making a solar thermoelectric power generating
system, the process comprising: (a) providing a roofing product
including at least one solar heat reflective area; (b) providing a
roofing product including at least one solar heat absorptive area;
(c) providing at least one thermoelectric element in thermal
contact with the at least one solar heat reflective area and the at
least one solar heat absorptive area; and (d) installing the
roofing products on a roof.
23. A roofing product for use in a solar thermoelectric power
generating system, the roofing product comprising: (a) a first one
solar heat reflective area having a first average solar
reflectivity, the first area being at least 5 mm.sup.2; and (b) a
second solar heat reflective area having a second average solar
reflectivity, the second area being at least 5 mm.sup.2; wherein
the difference between the first solar heat reflectivity and the
second solar heat reflectivity is at least five percent.
24. A roofing product according to claim 23 wherein the difference
between the first solar heat reflectivity and the second solar heat
reflectivity is at least ten percent.
25. A roofing product according to claim 23 wherein the difference
between the first solar heat reflectivity and the second solar heat
reflectivity is at least twenty percent.
26. A solar thermoelectric power generation system, the system
comprising: (a) an overlay for a roofing product, the overlay
including: at least one solar heat reflective area; and at least
one solar heat absorptive area; and (b) at least one thermoelectric
power generating element in thermal contact with the at least one
solar heat reflective area and the at least one solar heat
absorptive area.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a system and method for the
generation of electrical power from roofing, such as roofing
shingles, and processes for making such roofing.
[0003] 2. Brief Description of the Prior Art
[0004] The developed world is heavily dependent on fossil fuel as
an energy source for generating electricity. An unfortunate side
effect has been the production of large quantities of carbon
dioxide as a by-product, and the consequent accumulation of carbon
dioxide in the Earth's atmosphere, leading to anthropomorphic
global warming.
[0005] In North America residential roofs are most frequently
covered with bituminous roofing shingles, although other types of
roofing materials, such as slate, synthetic slate, wood such as
cedar shake, and metal such as steel, are also employed. Typical
roofing shingles based upon bitumen materials are known to absorb
significant solar heat and thus contribute to the so-called "Urban
Heat Island" effects. The Heat Island Group at the Berkeley
National Laboratory has noted that surface temperatures of a roof
can be very different due to their solar reflectance. Absorption of
heat by roofing materials not only creates higher energy demand for
HVAC systems, but also contributes to global warming. In the past
several years, many attempts have been made to make use of the
solar radiation incident on roofs, such as solar hot water systems.
Currently, solar-thermal systems are being installed on residential
roofs for water heating use. However, such systems are typically
not fully integrated into the roof system, and as a result they can
significantly negatively affect the aesthetics of a roof. Thus, it
would be advantageous to have a roof that is aesthetically pleasing
and also can generate solar power from the solar heat gain.
[0006] Further, recently there has been increased focus on
producing electricity from renewable energy sources, such as by
employing wind turbines, and solar-powered photovoltaic cells. The
rooftop use of photovoltaic devices to generate electrical power
and the use of solar water heating devices are well known. In
either case, the conventional appearance of roofs is ordinarily
compromised by the functional requirements of such devices. Efforts
have been made to reduce the aesthetic impact of applying
photovoltaic devices to roofing, such as disclosed, for example, in
U.S. Patent Publication No. 2008/0006323 A1.
[0007] In addition to photoelectric devices, which make use of the
incident solar energy flux to generate an electrical current
through the photovoltaic effect, efforts have been made to exploit
the thermoelectric effect to generate an electrical current from
heat generated from solar radiation incident on roofing. The
thermoelectric effect is the direct conversion of temperature
differences to electrical voltage and vice versa. A thermoelectric
device, such as a thermocouple, creates an electrical voltage when
there is a different temperature on either side of the device.
[0008] One side of a thermoelectric device can be exposed to the
sun to heat the device, while the other side can be cooled, as by
applying water for evaporative cooling, and the device can be
mounted on a roof, such as disclosed in U.S. Pat. No. 5,554,819, to
generate electricity. Solar power farms that convert solar heat
directly into electricity by using solar heat collectors to heat
liquids for power generation have been proposed. However, such
farms are typically large in scale and are not designed for
individual roofs. In addition, externally-installed small solar
power generators which can generate electrical power by heating
liquids with a solar heat concentrator to power electrical
generators have been proposed. However, they cannot be easily
integrated into roof systems, and hence are not aesthetically
pleasing. Solar radiation applied to the thermoelectric device can
be concentrated, such as by using a lens, in order to achieve a
greater temperature differential, such as disclosed in U.S. Patent
Publication No. 2009/0260667 A1, or solar heat can be transferred
to a heat storage medium so that thermoelectric power can be
provided during low sunlight periods, such as disclosed in U.S.
Pat. No. 4,251,291. Industrial scale thermoelectric solar power
systems have been proposed, such as disclosed in U.S. Pat. No.
6,313,391, and have received consideration as replacement for
fossil fuel-driven systems, as reported in Ye-Guang Deng et al.,
Journal of Renewable and Sustainable Energy, 1, 052701 (2009).
[0009] A thermoelectric roof solar heat collector has been employed
to power a ventilating fan for cooling. S. Maneewan et al. "Heat
Gain Reduction by Means of Thermoelectric Roof Solar Collector,"
Solar Energy, 78, pp. 495-503 (2005). U.S. Pat. No. 6,857,425
discloses a solar energy collector system including a thermopile
unit for generating electricity. U.S. Patent Publication No.
2008/0029146 A1 discloses a thermoelectric structure formed from a
network of wires and use of the thermoelectric structure to form a
textile structure. International Patent Publication No. WO
2007/071890 A1 discloses a thermally insulating thermoelectric
roofing element including a thermally insulating body which is
covered with pairs of interconnected elements formed from a first
and a second conductive material, such as a first and a second
conductive polymer. The conductive polymers, such as polyaniline or
polyacetylene, are doped differently. The geometry is such that
junctions are formed between the elements in each pair on opposite
sides of the thermally insulating body so that a Seeback voltage is
developed between the junctions when one side of the insulating
body is heated, as by solar radiation. Thermoelectric elements
mounted in roofing tiles are disclosed in German Patent Publication
DE 199 46 806 A1.
[0010] U.S. Pat. No. 7,241,500 discloses that the surface solar
reflectance of a roofing shingle can be varied independently of the
color, by preferentially reflecting the near infrared radiation of
solar spectrum, which contains no color information.
[0011] There is a continuing need for electric power sources that
use incident solar radiation as an energy source as a substitute
for power sources that consume non-renewable resources and produce
carbon dioxide implicated in anthropomorphic global warming.
SUMMARY OF THE INVENTION
[0012] The present invention provides a solar thermoelectric power
generation system. In one embodiment the system of the present
invention includes a roofing product, such as a roofing shingle,
roofing tile, synthetic roofing tile, or the like, including at
least one solar heat reflective area, a roofing product such as a
roofing shingle including at least one solar heat absorptive area,
and at least one thermoelectric power generating element in thermal
contact with the at least one solar heat reflective area and the at
least one solar heat absorptive area. The at least one solar heat
reflective area and the at least one solar heat adsorptive area can
be included on the same roofing product, such as on the same
roofing shingle, or they can be provided on different roofing
products. Preferably, the at least one thermoelectric power
generating element has a first junction in thermal contact with the
at least one solar heat reflective area and a second junction in
thermal contact with the at least one solar heat absorptive area.
Thus, in one aspect, the system preferably comprises a roofing
product such as a roofing shingle including both at least one solar
heat reflective area and at least one solar heat absorptive
area.
[0013] In another aspect, the at least one solar heat reflective
area and the at least one solar heat absorptive area have a similar
appearance and more preferably the same appearance. Preferably, the
at least one solar heat reflective area differs in E* from the at
least one solar heat absorptive area by no more that 10. More
preferably the at least one solar heat reflective area differs in
E* from the at least one solar heat absorptive area by no more that
5, and still more preferably by no more than 2.
[0014] Preferably, the system includes a plurality of
thermoelectric power generating elements electrically connected in
series to provide a predefined output voltage.
[0015] In another aspect of the present invention, the solar heat
reflective area preferably includes solar heat reflective roofing
granules. Further, in this aspect of the invention, the solar heat
absorptive area preferably includes solar heat absorptive roofing
granules.
[0016] In yet another aspect of the present invention, the system
further comprises thermal insulation between the solar heat
reflective area and the solar heat absorptive area.
[0017] The present invention also provides roofing products such as
roofing shingles for use in a solar thermoelectric power generating
system. The roofing products of the present invention comprise at
least one solar heat reflective area, at least one solar heat
absorptive area, and at least one thermoelectric power generating
element in thermal contact with the at least one solar heat
reflective area and the at least one solar heat absorptive area.
Preferably, the at least one thermoelectric power generating
element has a first junction in thermal contact with the at least
one solar heat reflective area and a second junction in thermal
contact with the at least one solar heat absorptive area.
Preferably, the roofing product includes both at least one solar
heat reflective area and at least one solar heat absorptive area.
Preferably, the at least one solar heat reflective area differs in
E* from the at least one solar heat absorptive area by no more that
10, more preferably by no more that 5, and still more preferably by
no more than 2.
[0018] Preferably, the system includes a plurality of
thermoelectric power generating elements electrically connected in
series to provide a predefined output voltage.
[0019] Preferably, the solar heat reflective area includes solar
heat reflective roofing granules. Preferably, the solar heat
absorptive area includes solar heat absorptive roofing
granules.
[0020] Preferably, in one aspect the solar thermoelectric power
generating system of the present invention further comprises
thermal insulation between the solar heat reflective area and the
solar heat absorptive area.
[0021] The present invention also provides a method of generating
electric power. The method comprises providing a roofing product
such as a roofing shingle, including at least one solar heat
reflective area; providing a roofing product, such as a roofing
shingle including at least one solar heat absorptive area;
providing at least one thermoelectric element in thermal contact
with the at least one solar heat reflective area and the at least
one solar heat absorptive area; exposing the roofing product to
solar radiation; and drawing electric current from the at least one
thermoelectric element. Preferably, the at least one thermoelectric
element has a first junction in thermal contact with the at least
one solar heat reflective area, and a second junction in thermal
contact with the at least one solar heat absorptive area.
[0022] In another aspect, the present invention provides a process
for a process for making a solar thermoelectric power generating
system. The process comprises providing a roofing product such as a
roofing shingle including at least one solar heat reflective area;
providing a roofing product such as a roofing shingle including at
least one solar heat absorptive area; providing at least one
thermoelectric element in thermal contact with the at least one
solar heat reflective area and the at least one solar heat
absorptive area; and installing the roofing product on a roof.
[0023] In yet another aspect, the present invention provides a
roofing product such as a roofing shingle for use in a solar
thermoelectric power generating system in which the roofing product
comprises a first solar heat reflective area having a first average
solar reflectivity, the first area being at least 5 mm.sup.2; and a
second solar heat reflective area having a second average solar
reflectivity, the second area being at least 5 mm.sup.2; wherein
the difference between the first solar heat reflectivity and the
second solar heat reflectivity is at least five percent.
Preferably, the difference between the first solar heat
reflectivity and the second solar heat reflectivity is at least ten
percent, and more preferably, at least twenty percent.
[0024] In another aspect, the present invention provides a solar
thermoelectric power generation system, the system comprising an
overlay for a roofing product, such as a roofing shingle, the
overlay including at least one solar heat reflective area; and at
least one solar heat absorptive area. The system further comprises
at least one thermoelectric power generating element in thermal
contact with the at least one solar heat reflective area and the at
least one solar heat absorptive area. The overlay can be applied to
an existing roofing surface, or used to fabricate new roofing
products.
BRIEF DESCRIPTION OF THE FIGURES
[0025] FIG. 1 is a schematic representation of a first embodiment
of a thermoelectric roofing shingle according to the present
invention.
[0026] FIG. 2 is a schematic representation of a second embodiment
of a thermoelectric roofing shingle according to the present
invention.
[0027] FIG. 3 is a schematic representation of a prototype of a
third embodiment of a thermoelectric roofing shingle according to
the present invention.
[0028] FIG. 4 is a schematic representation of a fourth embodiment
of a thermoelectric roofing shingle according to the present
invention.
[0029] FIG. 5 is a schematic representation of a portion of a
thermoelectric roofing shingle according to the present invention
showing a first scheme for placement of areas of enhanced solar
heat absorption and reduced solar absorption.
[0030] FIG. 6 is a schematic representation of a portion of a
thermoelectric roofing shingle according to the present invention
showing a second scheme for placement of areas of enhanced solar
heat absorption and reduced solar absorption.
[0031] FIG. 7 is a schematic representation of a portion of a
thermoelectric roofing shingle according to the present invention
showing a third scheme for placement of areas of enhanced solar
heat absorption and reduced solar absorption.
[0032] FIG. 8 is a schematic representation of a portion of a
thermoelectric roofing shingle according to the present invention
showing a fourth scheme for placement of areas of enhanced solar
heat absorption and reduced solar absorption.
[0033] FIG. 9 is a schematic representation of a fifth embodiment
of a thermoelectric roofing shingle according to the present
invention.
[0034] FIG. 10 is a schematic representation of a sixth embodiment
of a thermoelectric roofing shingle according to the present
invention.
[0035] FIG. 11 is a schematic representation of an overlay for a
roofing shingle for providing a thermoelectric generating system
according to the present invention.
[0036] FIG. 12 is a photograph of a sample deck including
thermoelectric roofing shingles according to the present
invention.
DETAILED DESCRIPTION
[0037] The present invention provides electrical power generated
from incident solar radiation. In the present invention,
thermal-electric materials are employed to bridge roof surfaces
with different solar heat absorption or solar reflectance, but with
the same or similar appearance. Thus, adjacent surfaces on a roof
can have a significant temperature difference. In one aspect of the
present invention, areas of the roof having different solar
reflectance have different colors. In another aspect of the present
invention, areas of a roof having different solar reflectance have
the same or similar colors. By bridging these areas having
different temperatures with electrically conductive materials
connected to exhibit the Seebeck or Thomson thermoelectric effect,
electric current is generated from the difference in temperature
between the roof areas with different solar reflectance. The
electrically conductive materials can be connected, for example, in
parallel to increase current flow, or in series to increase
potential.
[0038] As used in the present specification and claims:
[0039] "Colored" means having an L* value of less than 85,
preferably less than 55, even more preferably less than 45, when
measured using a HunterLab Model Labscan XE spectrophotometer using
a 0 degree viewing angle, a 45 degree illumination angle, a 10
degree standard observer, and a D-65 illuminant. "Colored" as so
defined is intended to include relatively dark tones.
[0040] "Solar heat reflective," "infrared reflective," and "SR"
mean having enhanced reflectance in the near infrared range. When
referring to areas of roofing shingles, "solar heat reflective"
means having a greater solar heat reflectance than a shingle having
the same or similar appearance colored with conventional
pigments.
[0041] "Solar heat absorptive" means having diminished reflectance
in the near infrared range. When referring to areas of roofing
shingles, "solar heat absorptive" means having less solar heat
reflectance than a shingle having the same or similar appearance
which has enhanced solar heat reflectance. The conventional roofing
shingles are "solar heat absorptive" compared with solar heat
reflective roofing shingles.
[0042] "Thermocouple" means a pair of thermoelectric elements
having different electrical properties and electrically connected
at a working junction, such that a difference in temperature
between the working junction and other portions of the
thermoelectric element which are remote from the working junction
generates an electric potential such that when the remote portions
of the thermoelectric elements are connected in a suitable circuit,
an electric current flows.
[0043] "Thermoelectric element" means a conductor, semiconductor or
intermetallic compounds having specific electrical properties.
Examples of thermoelectric elements include N-type thermoelectric
elements and P-type thermoelectric elements. Examples of
semiconductor materials useful for forming P-type thermoelectric
elements include solid solutions of bismuth telluride and antimony
telluride. Examples of semiconductor materials useful for forming
N-type thermoelectric elements include solid solutions of bismuth
telluride and bismuth selenide.
[0044] "Thermoelectric module" means an array of thermocouples
connected electrically in series but thermally in parallel.
[0045] The strength in color space E* is defined as
E*=(L*.sup.2+a*.sup.2+b*.sup.2).sup.1/2, where L*, a*, and b* are
the color measurements for a given sample using the 1976 CIE L*a*b*
color space. The total color difference .DELTA.E* is defined as
.DELTA.E*=(.DELTA.L*.sup.2+.DELTA.a*.sup.2+.DELTA.b*.sup.2).sup.1/2
where .DELTA.L*, .DELTA.a*, and .DELTA.b* are respectively the
differences in L*, a* and b* for two different color
measurements.
[0046] In one aspect of the present invention, roof-surfacing
material, such as bituminous roofing shingles or roofing membrane,
has areas of enhanced solar heat reflectance compared with other
areas, but otherwise has the same or similar appearance. The
appearance of the roof-surfacing material is typically determined
by a number of different factors, such as the roughness of the
surface and the color of the material used to form the surface, as
well as the perception of the observer. In the case of roofing
shingles covered with roofing granules, a similar appearance can be
achieved using granules of similar size distribution and shape, and
similar colors. Roofing granules are typically colored by coating
base materials with an inorganic semi-ceramic coating containing
durable inorganic pigments such as iron oxide. Shingles may be
coated with mixtures of granules having different colors. In order
to achieve a similar appearance, areas having an enhanced solar
heat reflectance preferably differ in color space strength (E*)
from solar heat absorptive areas by no more than 10, more
preferably by no more than 5, and still more preferably by no more
than 2. In terms of hue, preferably the at least one solar heat
reflective area differs in ((a*).sup.2+(b*).sup.2).sup.1/2 (in the
L*a*b* color system) from the at least one solar heat absorptive
area by no more that 10, more preferably by no more that 5, and
still more preferably by no more than 2. Preferably, in terms of
brightness or lightness the at least one solar heat reflective area
differs in L* (in the L*a*b* color system) from the at least one
solar heat absorptive area by no more that 10. More preferably the
at least one solar heat reflective area differs in L* from the at
least one solar heat absorptive area by no more than 5, and still
more preferably by no more than 2.
[0047] Examples of roofing surfacing materials or roofing products
that can be employed in the processes and articles of the present
invention including bituminous roofing shingles, bituminous roofing
sheet materials, roofing slate, synthetic roofing tiles, ceramic
roofing tiles, cedar roofing shakes, synthetic simulated roofing
shakes, and metal roofing sheet materials.
[0048] Conventionally, roofing granules are prepared using a metal
silicate coating binder. The roofing granules of the present
invention can be prepared through traditional granule preparation
methods, such as those disclosed in U.S. Pat. No. 2,981,636,
incorporated herein by reference. Thus, in preparing roofing
granules according to the present invention, one or more exterior
coating layers can be applied to the base particles. Each such
exterior coating layer includes a suitable coating binder. The
coating binder can be an inorganic or organic material, and is
preferably formed from a polymeric organic material or a
silicaceous material, such as a metal-silicate binder, for example
an alkali metal silicate, such as sodium silicate. When a
metal-silicate binder is employed in the preparation of roofing
granules of the present invention, the binder preferably includes a
heat-reactive aluminosilicate material, such as clay, preferably,
kaolin. Alternatively, the metal silicate binder can be
insolubilized chemically by reaction with an acidic material, for
example, ammonium chloride, aluminum chloride, hydrochloric acid,
calcium chloride, aluminum sulfate, and magnesium chloride, such as
disclosed in U.S. Pat. Nos. 2,591,149, 2,614,051, 2,898,232 and
2,981,636, each incorporated herein by reference, or other acidic
material such as aluminum fluoride. In another alternative, the
binder can be a controlled-release sparingly water-soluble glass
such as a phosphorous pentoxide glass modified with calcium
fluoride, such as disclosed in U.S. Pat. No. 6,143,318,
incorporated herein by reference.
[0049] The exterior coating layer or layers can contain functional
additives or fillers, such as colorant pigments, solar reflective
pigments, near infrared reflective particles, photocatalytic
particles, organic or inorganic biocides, algaecides, or other
biocides.
[0050] The base particles employed in the process of preparing the
granules of the present invention are preferably chemically inert
materials, such as inert mineral particles. The mineral particles,
which can be produced by a series of quarrying, crushing, and
screening operations, are generally intermediate between sand and
gravel in size (that is, between about 8 US mesh and 70 US mesh),
and preferably have an average particle size of from about 0.2 mm
to about 3 mm, and more preferably from about 0.4 mm to about 2.4
mm.
[0051] In particular, suitably sized particles of naturally
occurring materials such as talc, slag, granite, silica sand,
greenstone, andesite, porphyry, marble, syenite, rhyolite, diabase,
greystone, quartz, slate, trap rock, basalt, and marine shells can
be used, as well as recycled manufactured materials such as crushed
bricks, concrete, porcelain, fire clay, proppants, and the
like.
[0052] Solid and hollow glass spheres are available, for example,
from Potters Industries Inc., P.O. Box 840, Valley Forge, Pa.
19482-0840, such as SPHERIGLASS.RTM. solid "A" glass spheres
product grade 1922 having a mean size of 0.203 mm, product code
602578 having a mean size of 0.59 mm, BALLOTTINI impact beads
product grade A with a size range of 600 to 850 micrometers (U.S.
Sieve size 20-30), and QCEL hollow spheres, product code 300 with a
mean particle size of 0.090 mm. Glass spheres can be coated with a
suitable coupling agent, if desired, for better adhesion to the
binder of the coating composition. Exemplary coupling agents
include organosilanes, organotitanates, and organozirconates.
[0053] Suitable inert base particles, for example, mineral
particles with size passing #8 mesh and retaining on #70 mesh, can
be coated with a combination of a metal-silicate binder, kaolin
clay, composite nanoparticles, color pigments such as metal oxide
pigments to reach desirable colors, and biocidal particles,
followed by a heat treatment to obtain a durable coating.
[0054] When the coated granules are fired at an elevated
temperature, such as at least 800 degrees F., and preferably at
1,000 to 1,200 degrees F., the clay binder densifies to form strong
particles.
[0055] In some embodiments of the present process, the coated
granules are fired in an inert atmosphere in order to minimize
and/or control oxidation.
[0056] Examples of clays that can be employed in the process of the
present invention include kaolin, other aluminosilicate clays,
Dover clay, bentonite clay, etc.
[0057] In the alternative, a suitable silicaceous binder can be
formed from sodium silicate, modified by the addition of sodium
fluorosilicate, aluminum fluoride, and/or Portland cement.
[0058] Roofing granules of the present invention can be colored
using conventional coatings pigments. Examples of coatings pigments
that can be used include those provided by the Color Division of
Ferro Corporation, 4150 East 56th St., Cleveland, Ohio 44101, and
produced using high temperature calcinations, including PC-9415
Yellow, PC-9416 Yellow, PC-9158 Autumn Gold, PC-9189 Bright Golden
Yellow, V-9186 Iron-Free Chestnut Brown, V-780 Black, V0797 IR
Black, V-9248 Blue, PC-9250 Bright Blue, PC-5686 Turquoise, V-13810
Red, V-12600 Camouflage Green, V12560 IR Green, V-778 IR Black, and
V-799 Black.
[0059] Examples of roofing granules with high solar heat
reflectance are disclosed, for example, in U.S. Pat. Nos. 7,241,500
and 7,452,598, and U.S. Patent Publication 2006/0251807 A1, each
incorporated herein by reference. Examples of solar heat reflective
roofing membranes are disclosed, for example, in U.S. Pat. Nos.
7,422,989 and 7,592,066, and U.S. Patent Publication 2007/0054129
A1, each incorporated herein by reference.
[0060] For example, roofing granules with enhanced solar
reflectance can be formed by the combination of a binder, for
example, a metal silicate binder or polymeric binder suitable for
outdoor exposure, and special pigments that have high reflective
properties toward the solar heat radiation. Such pigments can in
some instances simultaneously serve as a colorant. Specifically,
colored, infrared-reflective pigments, such as those disclosed in
U.S. Pat. No. 6,174,360 (incorporated herein by reference) and
comprising a solid solution including iron oxide, can be employed
in producing colored infrared-reflective roofing granules of the
present invention. The colored, infrared-reflective pigment can
also comprise a near infrared-reflecting composite pigment such as
disclosed in U.S. Pat. No. 6,521,038 (incorporated herein by
reference). Composite pigments are composed of a near-infrared
non-absorbing colorant of a chromatic or black color and a white
pigment coated with the near infrared non-absorbing colorant.
[0061] In addition to, or in the alternative to, employing colored,
infrared-reflective pigments selected from the group consisting of
a solid solution including iron oxide and near infrared-reflecting
composite pigments, infrared-reflective roofing granules for use in
the present invention can be prepared using infrared-reflective
"functional" pigments. Infrared-reflective functional pigments
include light-interference platelet pigments including titanium
dioxide, light-interference platelet pigments based on metal oxide
coated-substrates, mirrorized silica pigments based upon
metal-doped silica, and alumina. Such infrared-reflective
functional pigments have been found to enhance the solar heat
reflectance when incorporated in roofing granules.
[0062] Thus, in one aspect, the present invention employs roofing
granules colored by light-interference platelet pigments and/or
infrared ("IR")-reflective color pigments to achieve higher solar
heat reflection. These "pearlescent" pigments based on metal
oxide-coated substrates allow additional solar reflection to
achieve both colors and increased solar heat reflection.
Light-interference platelet pigments based on metal oxide
coated-substrates are preferably selected from those pigments
constructed from partially opaque substrates, such as mica,
alumina, or silica, and metal-oxide coatings having
light-interference properties.
[0063] Colored infrared-reflective roofing granules can be obtained
by coating inert mineral particles with a first coating composition
including a binder and at least one reflective white pigment, and
curing the first coating composition on the inert mineral particles
to form base particles. The base particles are then coated with a
second coating composition including a binder and at least one
colorant selected from the group consisting of uv-stabilized dyes
and granule coloring pigments, and the second coating composition
is then cured. The granule coloring pigments can be conventional
granule coloring pigments based on metal oxides, or colored
infrared-reflective pigments. Optionally, the second coating
composition can include at least one infrared-reflective functional
pigment.
[0064] In yet another aspect, the present invention employs
infrared-reflective roofing granules obtained by a process
comprising providing an inert mineral particle and coating the
inert mineral particles with a first coating composition including
a base particle binder, and optionally at least one colorant
selected from the group consisting of UV-stabilized dyes and
granule coloring pigments, and curing the first coating composition
on the inert particles to form base particles. The base particles
are then coated with a second coating composition including a
coating binder, and at least one infrared-reflective functional
pigment selected from the group consisting of light-interference
platelet pigments including mica, light-interference platelet
pigments including titanium dioxide, mirrorized silica pigments
based upon metal-doped silica, and alumina, and the second coating
composition is then cured.
[0065] Furthermore, the roofing granules employed in the present
invention (including those with enhanced solar heat reflectance)
can have other functionalities, such as algaecidel,
photo-catalytic, or improved adhesion to the bitumen substrate.
[0066] In one aspect of the present invention, a first area of a
roof surface is covered with a first material having a first solar
heat reflectance and a second area of the roof surface is covered
with a second material having a second solar heat reflectance, the
first solar heat reflectance being different from the second solar
heat reflectance. The first and second areas are bridged by
thermoelectric elements, for example, a first thermoelectric
element and a second thermoelectric element, with pairs of the
first and second thermoelectric elements forming thermocouples. The
thermocouples are positioned and connected electrically such that a
difference in temperature between the first area and the second
area generates an electrical potential in the thermocouple. Thus,
electric current is generated from incident solar radiation by the
surface temperature differences between the first and second areas
of the roof surface.
[0067] In a presently preferred embodiment of the present
invention, the first area and second areas of the roof surface are
formed by using roofing granules having different solar heat
reflectance. Preferably, the first area is formed using roofing
granules having high solar heat reflectance, and the second area is
formed using conventional roofing granules. Alternatively, the
first area can be formed using roofing granules having high solar
heat reflectance and the second area can be formed using granules
having low solar heat reflectance. In another alternative, the
first area can be formed using conventional roofing granules and
the second area can be formed using granules having high solar heat
reflectance.
[0068] In one aspect, roofing shingles according to the present
invention comprise a first one solar heat reflective area having a
first average solar reflectivity, with the first area being at
least 5 mm.sup.2; and a second solar heat reflective area having a
second average solar reflectivity, with the second area being at
least 5 mm.sup.2; and the difference between the first solar heat
reflectivity and the second solar heat reflectivity is at least
five percent. Preferably, the difference between the first solar
heat reflectivity and the second solar heat reflectivity is at
least ten percent, and more preferably, at least twenty
percent.
[0069] In another aspect, the present invention provides a solar
thermoelectric power generation system based on an overlay for
roofing shingles. In one embodiment of this aspect of the present
invention, the overlay includes at least one solar heat reflective
area; and at least one solar heat absorptive area. At least one
thermoelectric power generating element in thermal contact with the
at least one solar heat reflective area and the at least one solar
heat absorptive area is also provided. The overlay can be applied
to the upper surface of one layer of a shingle to provide a shingle
with multiple layers to provide a desired aesthetic effect as well
as a thermoelectric power generating system. The roofing granules
selected so that the solar heat reflective area and the solar heat
absorptive area can have a similar appearance, or the granules can
be selected to provide a desired aesthetic effect. Further, the
roofing granules employed in providing the overlay can be selected
to be similar in appearance to the granules of the underlying
shingle, or they can differ in appearance, such as to provide a
desired aesthetic effect. A plurality of such overlays can be
applied to the upper surface of the preexisting shingle, and the
plurality can include overlays which are the same in size, shape
and appearance or differ in size, shape, and/or appearance to
provide desired aesthetic effects.
[0070] In another aspect, the present invention provides an overlay
for roofing materials wherein the overlay includes areas which are
more reflective than the underlying roofing material and
thermoelectric elements. In yet another aspect, the present
invention provides an overlay for roofing materials wherein the
overlay includes areas which are less reflective than the
underlying roofing material and thermoelectric elements.
[0071] In another embodiment of the present invention, the first
and second areas of the roof surface are formed by different areas
of a roofing membrane, such as roofing membranes fabricated from
compositions comprising ethylene-propylene-diene-monomer rubber
(EPDM), thermoplastic olefins (TPO), thermoplastic vulcanizates
(TPV), or polyvinyl chloride (PVC), filled with pigments and
fillers. In this embodiment, different areas of the roofing
membrane are filled with different fillers, or pigmented using
different pigments. For example, the first area of the roofing
membrane can be filled with conventional fillers and/or pigment,
while the second area can be filled with solar heat reflective
fillers and or pigment. Roofing membranes filled with solar heat
reflective filler are disclosed for example, in U.S. Patent
Publication No. 2008/0097004 A1, incorporated herein by
reference.
[0072] Examples of thermoelectric materials include metals,
semiconductors, intermetallic compounds, and electrically
conductive organic polymers. Examples of thermoelectric
semiconductor materials useful in the present invention include
those examples given in Section D, Chapters 19-34, of CRC Handbook
of Thermoelectrics (D. M. Rowe, ed., 1995, incorporated herein by
reference). Examples of thermoelectric materials include bismuth
telluride; antimony telluride; solid solutions of bismuth telluride
and antimony telluride; mixed crystals of bismuth, antimony, and
telluride; lead telluride, lead tin tellurides, alloys of silver
antimony telluride and germanium telluride, alkali silicides,
alkaline earth silicides, rare earth silicides, Group IVB
silicides, Group VB silicides, chromium silicides, molybdenum
silicides, tungsten silicides, manganese silicides, rhenium
silicides, iron silicides, ruthenium silicides, osmium silicides,
cobalt silicides such as cobalt monosilicide, rhenium silicides,
iridium silicides, nickel silicides, lead silicides, palladium
silicides, and platinum silicides; polycrystalline iron disilicide,
higher manganese silicides, silicon geranium, boron carbides,
metallic alloys, intermetallic compounds; electrically conductive
polymeric materials such as polymeric materials filled with carbon,
including conductive carbon-filled vinyl elastomer, conductive
carbon-filled nylon 12, and conductive carbon-filled polyphenylene
sulfide; polymeric materials filled with nanophase metal particles
such as disclosed in U.S. Pat. No. 5,973,050, incorporated herein
by reference; polyaniline; polypyrrole;
poly-N,N'(1,3-phenylenedimethylidyne)bis(3-ethynylaniline;
tetrathiafulvalinium tetracyanoquinodimethanide),
polyoctylthiophenes such as disclosed in U.S. Pat. No. 5,472,519
incorporated herein by reference; alternating poly(2,7-carbazole)
derivatives; alkyl and benzoyl polyindolocarbazoles and
polycarbazole derivatives; polydiindolocarbazole derivatives;
carbon nanotube-filled polymeric materials, including carbon
nanotube-filed poly(3,4-ethylenedioxythiophene) and
poly(styrenesulfonate); and the like.
[0073] Advanced thermoelectric materials are disclosed, for
example, in U.S. Patent Publication 2009/0072078 A1, incorporated
herein by reference.
[0074] In another aspect of this invention, the thermoelectric
elements are formed from metal, such as metal wire pairs joined to
one another to form a thermocouple. Preferably, the metal wire
pairs are chosen to have high Seebeck coefficients in order to
maximize the power output. Thermocouples commonly used for
temperature measurement, and the materials used for them, can be
employed in the present invention. Any junction of dissimilar
metals will produce an electric potential related to
temperature.
[0075] The roofing granules of the present invention can be used to
prepare roofing shingles. The roofing granules with different solar
heat reflectance can either be different colors or similar colors,
depending on the overall aesthetics desired for the shingles in
which the roofing granules are incorporated. Further, the roofing
granules with different solar heat reflectance can be located in
areas of the same shingle, such that the areas are adjacent to each
other. Alternatively, the roofing granules with different solar
heat reflectance can be used to prepare different shingles, and the
roofing shingles can be installed on a roof such that shingles
bearing roofing granules with different solar heat reflectance are
adjacent to one another.
[0076] The thermoelectric elements are preferably provided so that
when the shingles are installed on a roof, the thermoelectric
elements are in registration with the areas of different solar heat
reflectance, such that the thermoelectric elements bridge the areas
of different solar heat reflectance, and the working junctions of
the pairs of thermoelectric elements forming the thermocouples are
positioned within one of the areas of different solar heat
resistance. In one presently preferred embodiment of the present
invention, the thermoelectric elements are embedded on the backside
of a shingle having areas of different solar heat reflectance. In
this embodiment, each shingle is preferably provided with
connectors for electrically connecting the thermocouple(s) in the
shingle to those of another shingle. In another embodiment of the
present invention, the thermoelectric elements are embedded in or
secured to a sheet material, such as a roofing membrane or
underlayment, which is overlaid with roofing shingles having areas
of different solar heat reflectance. In this case, the sheet
material is provided with conductors electrically connecting the
thermocouple(s) underlying each shingle when the shingles are
installed over the membrane on a roof.
[0077] Thus, in one aspect of the present invention, a first type
of junction is included in a shingle construction in a first zone
having a greater solar reflectance, and a second type of junction,
analogous to a reference junction employed when a thermocouple is
used as a temperature measurement device, is included in a second
zone of the shingle construction having a lesser solar reflectance.
In ambient conditions on the roof, the temperature differential
creates a voltage potential between the two zones from which power
is collected.
[0078] It is also understood that the surface area with different
solar heat reflectance can be relatively small and distributed
throughout the shingle surface in a "power grid" format in order to
significantly increase power output.
[0079] The thermocouples in a single shingle can be connected
electrically in parallel to increase current or in series to
increase voltage, or in some other combination to achieve a desired
output profile.
[0080] The shingles employed in the present invention can be formed
using conventional techniques. In another aspect, thermally
insulating material can be added to the shingle to improve the R
value of the shingle, for example, by laminating a layer of thermal
insulation material to the underside of a conventional shingle. The
modified shingle, which is functionally similar to conventional
shingles, but includes insulating material, would shield the
underlayment below the shingles from the heating effects of the sun
and allow a greater temperature differential between the shingle
surface and the underlayment.
[0081] In this case, the thermoelectric elements, such as metal
wires, extend below the non-solar heat reflective granules, through
the solar heat reflective layer and make a connection with the
underlayment or decking material, thus harnessing a greater
potential than relying only on the laminated shingle itself. In
this embodiment, the thermal differential driving the generation of
power can be in the z-direction through the plane of the roofing
product, in addition to or instead of across different areas of the
plane as described above.
[0082] In another aspect of the present invention, the
thermoelectric elements are embedded in or bonded to shingles
formed from synthetic materials such as mineral-filled polymeric
materials and shaped to simulate traditional roofing materials such
as slate, cedar shakes, tiles, or the like. Alternatively, with the
use of suitable electrical and thermal insulation, the
thermoelectric elements are bonded to the underside of metal
roofing. The upper or weather-exposed side of such shingles or
metal roofing can be coated with heat reflective and heat
absorptive material so provide thermal gradients between the
junctions of the thermoelectric elements to provide electrical
power.
[0083] Referring now to the figures in which like reference
numerals represent like elements in each of the several views,
there is shown in FIG. 1, a schematic representation of a first
embodiment of a thermoelectric roofing shingle 10 according to the
present invention. The shingle 10 includes three tabs 12 separated
by cutouts 14 extending from a head lap portion 16 and a strip of
sealant material 18 for adhering the tabs of an overlying shingle
(not shown) to the shingle 10 when installing the shingles on a
roof deck. The tabs 12 include two outer tabs 20 and an inner tab
22. The outer tabs 20 are covered with a first type of roofing
granules 24, and the inner tab is coated with a second type of
roofing granule 26. Processes for delivering different types of
roofing granules to different areas of a roofing membrane are
disclosed, for example, in U.S. Patent Publications 2009/0151288
A1, 2009/0110818 A1, 2006/0260731 A1, and 2005/0235599 A1, each
incorporated herein by reference. The first type of roofing granule
24 is coated with a conventional non-solar heat reflective coating
material thus forming non-solar heat reflecting granules, while the
second type of roofing granule 26 is coated with a solar heat
reflective coating material thus forming solar heat reflecting
granules. However, the granule coatings are selected to make the
outer tabs 20 and the inner tab 22 to have a very similar
appearance and substantially the same color. In the alternative,
the granule coatings can be selected to provide tabs with colors in
a similar color family (such as complementary colors) or different
colors such as contrasting colors, depending on the visual effect
desired. A first thermoelectric element 30 formed from an n-type
semiconductor materiel bridges one of the outer tabs 20 and the
inner tab 22 and a second thermoelectric element 32 formed from a
p-type semiconductor material bridges the second outer tabs 20 and
the inner tab 22, and the first and second thermoelectric elements
30, 32 are in electrical contact with one another at a junction
(not shown) positioned under the inner tab 22, and the other ends
of the first and second thermoelectric elements 30, 32 are
electrically connected to a load 34. When exposed to solar
radiation, the non-solar heat reflective granules 24 absorb solar
heat to a greater extent than the solar heat reflective granules
26, so that a temperature difference is created between the inner
tab 22 and the outer tabs 20, which in turn creates an electrical
potential difference between the junction between the
thermoelectric elements 30, 32 under or within the inner tab 22,
and the opposite ends of the thermoelectric elements 30, 32 under
the outer tabs 20, driving an electric current to flow through the
load 34.
[0084] FIG. 2 is a schematic representation of a second embodiment
of a thermoelectric roofing shingle 40 according to the present
invention. The shingle 40 includes three tabs 42 separated by
cutouts 44 extending from a head lap portion 46 and a strip of
sealant material 48 for adhering the tabs of an overlying shingle
(not shown). The tabs 42 include two outer tabs 50 and an inner tab
52. The outer tabs 50 are covered with a first type of roofing
granules 54 and the inner tab is coated with a second type of
roofing granule 56. The first type of roofing granule 54 is coated
with a conventional non-solar heat reflective coating material thus
forming non-solar heat reflecting granules, while the second type
of roofing granule 56 is coated with a solar heat reflective
coating material thus forming solar heat reflecting granules. In
this case, the granule coatings differ significantly in appearance
and contribute to a decorative effect. A pair of thermocouples 58
bridges the outer tabs 50 and inner tab 52. Each thermocouple 58
includes a first wire 60 formed from a first metal and a second
wire 62 formed from a second metal. The first and second wires 60,
62 are connected under the outer tabs 50 at a first or hot junction
66 and under the inner tab 52 to form a second or cold junction 68,
while the ends of the two thermocouples 58 are electrically
connected in parallel to drive a load (not shown). When exposed to
solar radiation, the non-solar heat reflective granules 54 absorb
solar heat to a greater extent than the solar heat reflective
granules 56, so that a temperature difference is created between
the inner tab 52 and the outer tabs 50, which in turns creates an
electrical potential difference between the hot junctions 66 and
the cold junctions 68, driving an electric current to flow through
the load.
[0085] FIG. 3 is a schematic representation of a prototype of a
third embodiment of a thermoelectric roofing shingle 70 according
to the present invention. The shingle 70 is formed from an
underlying base shingle 71 to which is laminated a partially
overlying section 73 formed from a second shingle material. The
resulting laminated shingle 70 includes three tabs 72 separated by
cutouts 74 extending from a head lap portion 76 and a strip of
sealant material 78 for adhering the tabs of an overlying shingle
(not shown). The tabs 72 include two outer tabs 80 and an inner tab
82. The inner tab 82 and the adjacent area of the head lap portion
76 are overlaid with the congruent section 73 of a second layer of
shingle material. The base shingle 71 is covered with a first type
of roofing granules 84 and the overlying laminated section 73 is
covered with a second type of roofing granule 86. In this case the
second type of roofing granule 86 is coated with a conventional
non-solar heat reflective coating material thus forming non-solar
heat reflecting granules, while the first type of roofing granule
86 is coated with a solar heat reflective coating material thus
forming solar heat reflecting granules. A plurality of
thermoelectric modules 90 are placed under the section 73 of the
shingle with low solar heat reflectance. The modules 90 are
connected electrically with a suitable conductor 92 to a bus bar 94
at which electrical potential measurements can be made. When
exposed to solar radiation, the non-solar heat reflective granules
86 absorb solar heat to a greater extent than the solar heat
reflective granules 84. However, in this embodiment, heat is
transferred in the z-direction reflecting the construction of the
thermoelectric modules employed, and the potential measured depends
on the extent to which heat is dissipated from the "cold" end of
the modules.
[0086] FIG. 4 is a schematic representation of a fourth embodiment
of a thermoelectric roofing shingle 100 according to the present
invention. The shingle 100 includes three tabs 102 separated by
cutouts 104 extending from a head lap portion 106 and a strip of
sealant material 108 for adhering the tabs of an overlying shingle
(not shown). The tabs 102 include two outer tabs 110 and an inner
tab 112. The outer tabs 110 are covered with a first type of
roofing granules 114 and the inner tab 112 is coated with a second
type of roofing granule 116. A layer of thermal insulation 120 is
positioned under the inner tab 112. The first type of roofing
granule 114 is coated with a conventional non-solar heat reflective
coating material thus forming non-solar heat reflecting granules,
while the second type of roofing granule 116 is coated with a solar
heat reflective coating material thus forming solar heat reflecting
granules. A pair of thermocouples 118 bridges the outer tabs 110
and the inner tab 112. Each thermocouple 118 includes a first wire
130 formed from a first metal and a second wire 132 formed from a
second metal. The first and second wires 130, 132 are connected
under the outer tabs 110 at a first or hot junction 136 and under
insulation layer 120 under the inner tab 112 to form a second or
cold junction 138, while the ends of the two thermocouples 118 are
electrically connected in parallel to drive a load (not shown).
When exposed to solar radiation, the non-solar heat reflective
granules 114 absorb solar heat to a greater extent than the solar
heat reflective granules 116, so that a temperature difference is
created between the inner tab 112 and the outer tabs 110, which in
turns creates an electrical potential difference between the hot
junctions 136 and the cold junctions 138 under the insulation layer
120 under the inner tab 112, driving an electric current to flow
through the load.
[0087] FIG. 5 is a schematic representation of a fifth embodiment
of a thermoelectric roofing shingle 140 according to the present
invention. The shingle 140 includes a plurality of tabs 142
separated by cutouts (not shown) extending from a head lap portion
(not shown). In this embodiment, each of the tabs 142 is covered
with two types of roofing granules arranged in parallel alternating
strips 144, 146, extending vertically or perpendicular to the long
axis of the shingle 140. A first type of roofing granules covers
one set of strips 144 and a second type of roofing granule covers
the second set of strips 146. The first type of roofing granule is
coated with a conventional non-solar heat reflective coating
material thus forming non-solar heat reflecting granules to give
solar heat absorptive strips 144, while the second type of roofing
granule is coated with a solar heat reflective coating material
thus forming solar heat reflecting granules to give solar heat
reflective strips 146. Thermoelectric elements (not shown) are
positioned underneath the tab 142 bridging the boundaries formed by
the heat absorptive strips 144 and the solar heat reflective strips
146 and are connected to provide an electric current. The coatings
for the first and second types of roofing granules are selected to
provide a similar visual appearance.
[0088] FIG. 6 is a schematic representation of a sixth embodiment
of a thermoelectric roofing shingle 150 according to the present
invention. The shingle 150 includes a plurality of tabs 152
separated by cutouts (not shown) extending from a head lap portion
(not shown). In this embodiment, each of the tabs 152 is covered
with two types of roofing granules arranged in a checkerboard
pattern of generally rectangular areas 154, 156. A first type of
roofing granules covers one set of areas 154 and a second type of
roofing granule covers the second set of areas 156. The first type
of roofing granule is coated with a conventional non-solar heat
reflective coating material thus forming non-solar heat reflecting
granules to give solar heat absorptive areas 154, while the second
type of roofing granule is coated with a solar heat reflective
coating material thus forming solar heat-reflecting granules to
give solar heat reflective areas 156. A plurality of thermocouples
(not shown) are positioned underneath the tab 152 bridging the
boundaries formed by the heat absorptive areas 154 and the solar
heat reflective areas 156 and connected to provide an electric
current. The coatings for the first and second types of roofing
granules are selected to provide a nearly identical visual
appearance.
[0089] FIG. 7 is a schematic representation of a fifth embodiment
of a thermoelectric roofing shingle 160 according to the present
invention. The shingle 160 includes a plurality of tabs 162
separated by cutouts (not shown) extending from a head lap portion
(not shown). In this embodiment, each of the tabs 162 is covered
with two types of roofing granules arranged in parallel alternating
strips 164, 166, running horizontally, or parallel to the long axis
of the shingle 160. A first type of roofing granules covers one set
of strips 164 and a second type of roofing granule covers the
second set of strips 166. The first type of roofing granule is
coated with a conventional non-solar heat reflective coating
material thus forming non-solar heat reflecting granules to give
solar heat absorptive strips 164, while the second type of roofing
granule is coated with a solar heat reflective coating material
thus forming solar heat-reflecting granules to give solar heat
reflective strips 166. Thermoelectric elements (not shown) are
positioned underneath the tab 162 bridging the boundaries formed by
the heat absorptive strips 164 and the solar heat reflective strips
166 and are connected to provide an electric current. The coatings
for the first and second types of roofing granules are selected to
provide a similar visual appearance.
[0090] FIG. 8 is a schematic representation of a sixth embodiment
of a thermoelectric roofing shingle 170 according to the present
invention. The shingle 170 includes an upper layer 172 and a
coextensive lower layer 174 adhered to the upper layer 172 by
suitable means, such as by an adhesive material (not shown). The
upper layer 172 has a series of generally trapezoidal cutouts 176
formed in the lower portion thereof such that the upper surface of
the lower layer 174 is visible through the cutouts 176 forming
generally trapezoidal areas 178, and such that the a plurality of
generally trapezoidal tabs 180 are formed in the upper layer 172 in
between the cutouts 176. In this embodiment, the lower or tab
portion of the upper layer 172 of the shingle 170 is covered with a
first type of granule 182, and the lower layer 174 is covered with
a second type of granule 184. The upper or head lap portion of the
upper layer 182 is covered with a third type of granule 186. The
second type of roofing granule is coated with a conventional
non-solar heat reflective coating material thus forming non-solar
heat reflecting granules to give solar heat absorptive areas 178,
while the first type of roofing granule is coated with a solar heat
reflective coating material thus forming solar heat reflecting
granules to give solar heat reflective tabs 180. Thermoelectric
elements (not shown) are positioned underneath lower layer 174 and
bridge the boundaries 188 between the solar heat reflective tabs
180 and the solar heat absorptive exposed areas 178 of the lower
layer 174 and are connected to provide an electric current. The
coatings for the first and second types of roofing granules are
selected to provide a similar visual appearance. The optional third
type of granule 186 can be coated with a conventional coating
material to reduce manufacturing cost, since the head lap portion
of the shingle 170 is covered by the lower portion of another
shingle when the shingle 170 is installed on a roof.
[0091] FIG. 9 is a schematic representation of a seventh embodiment
of a thermoelectric roofing shingle 260 according to the present
invention. The shingle 260 includes a plurality of tabs 262
separated by cutouts (not shown) extending from a head lap portion
(not shown). In this embodiment, each of the tabs 262 is covered
with two types of roofing granules arranged in a checkerboard
pattern of generally rectangular areas 264, 266. A first type of
roofing granules covers one set of areas 264 and a second type of
roofing granule covers the second set of areas 266. The first type
of roofing granule is coated with a conventional non-solar heat
reflective coating material thus forming non-solar heat reflecting
granules to give solar heat absorptive areas 264, while the second
type of roofing granule is coated with a solar heat reflective
coating material thus forming solar heat reflecting granules to
give solar heat reflective areas 266. As can be seen in the cutaway
portion of the figure, a plurality of thermoelectric units 274 are
mounted on an underlying base sheet 272 and together comprise a
circuit layer 270. Each of the thermoelectric units 274 include
n-type element 276 and a p-type element 278, which bridge the
boundaries formed by the heat absorptive areas 264 and the solar
heat reflective areas 266. The n-type elements 276 and the p-type
elements 278 are connected under the solar heat absorptive areas
264 to give "hot" junctions 280 and under the solar heat reflective
areas 266 to give "cold" junctions 282. The thermoelectric units
274 are connected by suitable electric leads 284 to provide an
electric current. The coatings for the first and second types of
roofing granules are selected to provide a nearly identical visual
appearance.
[0092] FIG. 10 is a schematic representation of an eighth
embodiment of a thermoelectric roofing shingle 300 according to the
present invention. The shingle 300 includes a plurality of tabs 302
separated by cutouts (not shown) extending from a head lap portion
(not shown). In this embodiment, each of the tabs 302 is covered
with two types of roofing granules arranged in a checkerboard
pattern of generally rectangular areas 304, 306. A first type of
roofing granules covers one set of areas 304 and a second type of
roofing granule covers the second set of areas 306. The first type
of roofing granule is coated with a conventional non-solar heat
reflective coating material thus forming non-solar heat reflecting
granules to give solar heat absorptive areas 304, while the second
type of roofing granule is coated with a solar heat reflective
coating material thus forming solar heat reflecting granules to
give solar heat reflective areas 306. As can be seen in the cutaway
portion of the figure, a plurality of thermoelectric units 314 are
mounted on an underlying base sheet 312 and together comprise a
circuit layer 310. A layer of thermal insulation 330 is positioned
under the solar heat reflective area 306 and over the respective
portions of the thermoelectric units 314. Each of the
thermoelectric units 314 includes n-type element 316 and a p-type
element 318, which bridge the boundaries formed by the heat
absorptive areas 304 and the solar heat reflective areas 306. The
n-type elements 316 and the p-type elements 318 are connected under
the solar heat absorptive areas 304 to give "hot" junctions 320 and
under the solar heat reflective areas 306 to give "cold" junctions
322. The thermoelectric units 314 are connected by suitable
electrical leads 324 to provide an electric current. The coatings
for the first and second types of roofing granules are selected to
provide a nearly identical visual appearance.
[0093] FIG. 11 is a schematic representation of a thermoelectric
overlay 350 for application to a shingle (not shown) to provide for
thermoelectric power generation. The overlay 350 is covered with
two types of roofing granules arranged in generally rectangular
areas 354, 356. A first type of roofing granules covers one area
354 and a second type of roofing granule covers the second area
356. The first type of roofing granule is coated with a
conventional non-solar heat reflective coating material thus
forming non-solar heat reflecting granules to give a solar heat
absorptive area 354, while the second type of roofing granule is
coated with a solar heat reflective coating material thus forming
solar heat reflecting granules to give a solar heat reflective area
356. As can be seen in the cutaway portion of the figure, a
plurality of thermoelectric units 364 are mounted on an underlying
base sheet 362 and together comprise a circuit layer 360. A layer
of thermal insulation 380 is positioned under the solar heat
reflective area 356 and over the respective portions of the
thermoelectric units 364. Each of the thermoelectric units 364
includes n-type element 366 and a p-type element 368, which bridge
the boundaries formed by the heat absorptive area 354 and the solar
heat reflective area 356. The n-type elements 366 and the p-type
elements 368 are connected under the solar heat absorptive areas
354 to give "hot" junctions 370 and under the solar heat reflective
areas 356 to give "cold" junctions 372. The thermoelectric units
364 are connected by suitable electrical leads 374 to provide an
electric current. The coatings for the first and second types of
roofing granules are selected to provide a nearly identical visual
appearance. The thermoelectric overlay 350 or a plurality of such
overlays can be applied to the upper surface of a shingle (not
shown) or to the surface of a previously installed shingles on a
roof (not shown) by suitable means such as by application of a
suitable adhesive and the electric leads 374 can be connected with
other such overlays to provide enhanced electric power from the
interconnected array of overlays 350.
[0094] The roofing granules of the present invention can be
employed in the manufacture of roofing products, such as asphalt
shingles and bituminous membranes, using conventional roofing
production processes. Typically, bituminous roofing products are
sheet goods that include a non-woven base or scrim formed of a
fibrous material, such as a glass fiber scrim. The base is coated
with one or more layers of a bituminous material such as asphalt to
provide water and weather resistance to the roofing product. One
side of the roofing product is typically coated with mineral
granules to provide durability, reflect heat and solar radiation,
provide aesthetic effects, and to protect the bituminous binder
from environmental degradation. The roofing granules of the present
invention can be embedded in the surface of such bituminous roofing
products using conventional methods.
[0095] Bituminous roofing products are typically manufactured in
continuous processes in which a continuous substrate sheet of a
fibrous material such as a continuous felt sheet or glass fiber mat
is immersed in a bath of hot, fluid bituminous coating material so
that the bituminous material saturates the substrate sheet and
coats at least one side of the substrate. Roofing granules are then
distributed over selected portions of the top of the sheet, and the
bituminous material serves as an adhesive to bind the roofing
granules to the sheet when the bituminous material has cooled. The
reverse side of the substrate sheet can then be coated with an
anti-stick material such as a suitable mineral powder or a fine
sand. The sheet can then be cut into conventional shingle sizes and
shapes (such as one foot by three feet rectangles), slots can be
cut in the shingles to provide a plurality of "tabs" for ease of
installation and aesthetic effect, additional bituminous adhesive
can be applied in strategic locations and covered with release
paper to provide for securing successive courses of shingles during
roof installation, and the finished shingles can be packaged. More
complex methods of shingle construction can also be employed, such
as building up multiple layers of sheet in selected portions of the
shingle to provide an enhanced visual appearance, or to simulate
other types of roofing products. Alternatively, the sheet can be
formed into membranes or roll goods for commercial or industrial
roofing applications.
[0096] The bituminous material used in manufacturing roofing
products according to the present invention is derived from a
petroleum-processing by-product such as pitch, "straight-run"
bitumen, or "blown" bitumen. The bituminous material can be
modified with extender materials such as oils, petroleum extracts,
and/or petroleum residues. The bituminous material can include
various modifying ingredients such as polymeric materials, such as
SBS (styrene-butadiene-styrene) block copolymers, resins,
flame-retardant materials, oils, stabilizing materials, anti-static
compounds, and the like. Preferably, the total amount by weight of
such modifying ingredients is not more than about 15 percent of the
total weight of the bituminous material. The bituminous material
can also include amorphous polyolefins, up to about 25 percent by
weight. Examples of suitable amorphous polyolefins include atactic
polypropylene, ethylene-propylene rubber, etc. Preferably, the
amorphous polyolefins employed have a softening point of from about
130 degrees C. to about 160 degrees C. The bituminous composition
can also include a suitable filler, such as calcium carbonate,
talc, carbon black, stone dust, or fly ash, preferably in an amount
from about 10 percent to 70 percent by weight of the bituminous
composite material.
[0097] The following examples are provided to better disclose and
teach processes and compositions of the present invention. They are
for illustrative purposes only, and it must be acknowledged that
minor variations and changes can be made without materially
affecting the spirit and scope of the invention as recited in the
claims that follow.
Example 1
[0098] A thermoelectric shingle was constructed by using a standard
Star White 3-tab shingle (XT25 available from CertainTeed Corp.,
Oxford, N.C.) as the base of high solar heat reflectance surface
(Avg. SR=28% measured according to ASTM C1549). A 6'' width section
of shingle in Moire Black color (XT25 also from CertainTeed) was
then laminated on top of the high SR shingle to form the upper
surface of low solar reflectance (Avg. SR=3.7% according to ASTM
C1549). Five thermo-electric modules (C-AA-300 from Tellurex,
Traverse City, Mich.) were then placed underneath the top shingle
of low solar reflectance. The thermoelectric modules were then
connected in series by connecting the wires from the module and
then connecting to a bus bar as final terminal for powder
generation monitoring. A schematic diagram of the thermoelectric
shingle is shown in FIG. 3.
[0099] The thermoelectric shingle was then applied to a 1/4''
plywood sheet and was then placed outside with a south facing
exposure and 12/12 slope. The power output was then recorded by a
Fluke 189 RMS multimeter, along with surface temperatures and
weather conditions. The results are listed in Table 1. As can be
seen, the thermoelectric shingle was found to consistently generate
power according to the temperature difference between the top layer
of low SR and bottom layer of high SR in outdoor, roof-like
condition.
[0100] The same thermo-electric shingle was also tested inside a
lab by placing it under a light booth to heat up the surface. The
light booth is constructed in-house by placing four 50 W flood
lights (Philips DuraMax R50 flood light bulb) in a stand with
dimensions of 12''W.times.12''L.times.16''H. The surface
temperatures, voltage output, and testing conditions were recorded
and listed in Table 1 also. As can be seen, the shingle was found
to be able to produce stable power for relatively long duration,
with a consistent surface temperature difference under lab
conditions.
TABLE-US-00001 TABLE 1 Surface Run temperatures Power No. Location
Low SR High SR output, VDC Test conditions 1 Outdoor Avg. 100 Avg.
88.5 0.113-0.14 Cloudy, with deg. F. deg. F. ~50 percent cloud
cover, light wind, air temp 70 deg. F. 2 Indoor Avg. 110 Avg. 99
0.185-0.189 Indoor room deg. F. deg. F. conditions
Example 2
[0101] A thermoelectric shingle sample deck with shingles having
similar colors was constructed using commercially available
shingles that have different solar reflectivity to generate
temperature differences for power generation. The thermoelectric
shingle deck was constructed in the configuration shown in FIG. 3,
and a photograph of the actual sample deck is shown in FIG. 12. The
sample deck consists of shingles with averaged solar reflectance of
28% and color of L*=41.44, a*=9.24, b*=15.82 (Landmark Solaris in
Reshawn Shake color, commercially available from CertainTeed Corp)
as the cool surface; and shingles with averaged solar reflectance
of 11.4% with a color of L*=38.14, a*=7.79, b*=15.68 (Landmark
shingle in Reshawn Shake color, commercially available from
CertainTeed Corp.) as the hot surface. The sample deck has a
uniform color appearance with the color difference DE*<5 unit.
The thermoelectric circuit was constructed in the same way as in
Example 1 and is shown schematically in FIG. 3. The sample deck was
then placed outside into direct sun on a flat surface without any
shading. The weather was sunny with scattered cloud and the air
temperature was 79.degree. F. (26 degrees C.) according to local
weather station data at the time of experimentation. The result of
the experiment is provided in Table 2.
TABLE-US-00002 TABLE 2 Surface Run temperatures Power No. Location
Low SR High SR output, V.sub.DC Test conditions 1 Outdoor
135.8.degree. F. 110.5.degree. F. 0.417 Sunny with scattered cloud,
light wind, air T = 79.degree. F. 2 Outdoor 135.1.degree. F.
116.degree. F. 0.336 Indoor room conditions
[0102] Various modifications can be made in the details of the
various embodiments of the processes, compositions and articles of
the present invention, all within the scope and spirit of the
invention and defined by the appended claims.
* * * * *