U.S. patent application number 13/733867 was filed with the patent office on 2014-01-16 for solar access measurement device.
This patent application is currently assigned to SOLMETRIC CORPORATION. The applicant listed for this patent is SOLMETRIC CORPORATION. Invention is credited to Willard S. MacDonald.
Application Number | 20140016121 13/733867 |
Document ID | / |
Family ID | 38194994 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140016121 |
Kind Code |
A1 |
MacDonald; Willard S. |
January 16, 2014 |
SOLAR ACCESS MEASUREMENT DEVICE
Abstract
A Solar Access Measurement Device ("SAMD") located at a
predetermined position is disclosed. The SAMD may include a skyline
detector enabled to detect a skyline of a horizon relative to the
SAMD, an orientation determination unit enabled to determine the
orientation of the skyline detector, and a processor in signal
communication with the skyline detector and orientation
determination unit.
Inventors: |
MacDonald; Willard S.;
(Sebastopol, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SOLMETRIC CORPORATION |
Sebastopol |
CA |
US |
|
|
Assignee: |
SOLMETRIC CORPORATION
Sebastopol
CA
|
Family ID: |
38194994 |
Appl. No.: |
13/733867 |
Filed: |
January 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12952101 |
Nov 22, 2010 |
8386179 |
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13733867 |
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|
11321294 |
Dec 28, 2005 |
7873490 |
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12952101 |
|
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Current U.S.
Class: |
356/139.01 |
Current CPC
Class: |
G01S 3/7868 20130101;
G01J 1/4228 20130101; G01W 1/12 20130101; G01J 1/0266 20130101;
F24S 2201/00 20180501; G01J 1/0242 20130101; G01J 2001/4266
20130101 |
Class at
Publication: |
356/139.01 |
International
Class: |
G01J 1/02 20060101
G01J001/02 |
Claims
1. An apparatus, comprising: an image sensor enabled to capture an
image of a horizon that includes the sun; an orientation
determination unit enabled to establish an inclination of the
image; and a processor in signal communication with the image
sensor and the orientation determination unit, the processor
enabled to deduce a magnetic orientation for the image, based on
the inclination of the image, a position of the sun within the
image, a time, a date, and a location associated with the
image.
2. The apparatus of claim 1 wherein the image sensor, the
orientation determination unit and the processor are included in a
solar access measurement device.
3. The apparatus of claim 2 wherein the deduced magnetic
orientation provides a calibration for the solar access measurement
device.
4. The apparatus of claim 1 wherein the image sensor includes a
wide-angle lens that enables the image sensor to capture the image
over a semi-spherical range.
5. The apparatus of claim 1 wherein the captured image comprises
multiple images that are stitched together with software to provide
a combined image.
6. The apparatus of claim 5 further including a gyroscopic sensor
that senses motion of the image sensor relative to a reference
orientation.
7. The apparatus of claim 1 wherein the processor is further
enabled to detect a skyline within the image of the horizon,
wherein the skyline includes a boundary at which at least one solar
obstacle and the sky meet within the captured image of the
horizon.
8. The apparatus of claim 7 wherein the processor is further
enabled to determine an amount of solar radiation at the location
associated with the captured image.
9. The apparatus of claim 1 wherein the processor is further
enabled to provide one or more paths of the sun throughout a range
of times of day and days of the year for the location associated
with the captured image, and wherein the one or more paths of the
sun are superimposed on the captured image.
10. The apparatus of claim 1 wherein a GPS in signal communication
with the processor determines the location associated with the
captured image.
11. An apparatus, comprising: an image sensor enabled to capture
multiple images of a horizon that includes a skyline, wherein at
least one image of the multiple images includes the sun; an
inclinometer enabled to establish an inclination of the at least
one image that includes the sun; a timing device in signal
communication with a processor; a position locator in signal
communication with the processor; a gyroscopic sensor in signal
communication with the processor, the gyroscopic sensor sensing
motion of the image sensor relative to a reference orientation; and
wherein the processor is in signal communication with the image
sensor and the inclination detector, the processor enabled to
deduce a magnetic orientation for the image based on the
inclination of the at least one image that includes the sun, a
position of the sun within the at least one image that includes the
sun, a time and a date provided by a timing device, and a location
provided by the position locator.
12. The apparatus of claim 11 wherein the image sensor, the
inclinometer, and the processor are included in a solar access
measurement device.
13. The apparatus of claim 12 wherein the deduced magnetic
orientation provides a calibration for the solar access measurement
device.
14. The apparatus of claim 11 wherein the multiple images are
stitched together with software to provide a combined image.
15. The apparatus of claim 14 wherein the processor is further
enabled to determine a solar access based on a skyline detected
within the combined image, wherein the skyline includes a boundary
at which at least one solar obstacle and the sky meet within the
combined image.
16. The apparatus of claim 14 wherein the processor is further
enabled to provide one or more paths of the sun throughout a range
of times of day and days of the year for the location provided by
the position locator, and wherein the one or more paths of the sun
are superimposed on the combined image.
17. The apparatus of claim 14 wherein the processor is further
enabled to determine an amount of solar radiation at the location
provided by the position locator.
18. A method, comprising: capturing an image of a horizon that
includes the sun; establishing an inclination of the image; and
deducing a magnetic orientation for the image, based on the
inclination of the image, a position of the sun within the image, a
time, a date, and a location associated with the image.
19. The method of claim 18 further comprising detecting a skyline
within the captured image of the horizon.
20. The method of claim 18 further comprising determining an amount
of solar radiation at the location associated with the captured
image.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
12/952,101, filed Nov. 22, 2010, titled "SOLAR ACCESS MEASUREMENT
DEVICE";
[0002] which is a continuation of U.S. Ser. No. 11/321,294, filed
on Dec. 28, 2005, titled "SOLAR ACCESS MEASUREMENT DEVICE", which
is now U.S. Pat. No. 7,873,490, issued Jan. 18, 2011;
[0003] the contents of each of which are hereby incorporated by
reference.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] This invention relates to solar measurement equipment, and
in particular to measurement equipment capable of measuring solar
access.
[0006] 2. Description of the Related Art
[0007] With the advent of the modern industrialized society, there
is a constant need for energy to power the growing energy
consumption needs of the society. At present, fossil fuels are the
main source of this energy but factors such as fossil fuel deposit
scarcity, resultant pollution from burning fossil fuels, and
geopolitical factors that affect the price and availability of
fossil fuels have resulted in a need for alternative sources of
energy. An example of a popular form of alternative energy source
is solar energy.
[0008] In order to utilize solar energy, solar energy systems have
been created and designed to harness received solar radiation into
thermal or electrical energy through various means. These solar
energy systems typically include a solar energy collector to
collect the solar radiation and other components that convert the
collected solar radiation into either electrical or thermal
energy.
[0009] These solar energy systems need to be designed and installed
in locations and orientations with the highest solar radiation
exposure in order to maximize the amount of solar radiation that
may be collected by the solar energy systems. As a result, there is
a need to measure the solar radiation access at a given location
and orientation.
[0010] There exist a number of known systems for measuring solar
radiation. However, some of these systems are non-electronic
devices that have limitations in their ease of use and accuracy
because some utilize chemical processes of film exposure to store
captured images that may not be analyzed until the film is
developed, and most have alignment problems that make it difficult
to make accurate measurements. The known electronic devices
typically have limitations that include the lack of image
calibration, the need to determine coordinates that uniquely
identify the location of the device on the earth or region, the
need to be left on-site for a long period of time, an inability to
identify the skyline and open sky, and/or an inability to account
for shading.
[0011] Therefore, there is a need for a new solar radiation
measurement system that is capable of determining the solar
radiation access at a given location and orientation without having
the limitations associated with the existing known solar radiation
measurement systems.
SUMMARY OF THE INVENTION
[0012] A Solar Access Measurement Device ("SAMD") located at a
predetermined position is disclosed. The SAMD may include a skyline
detector enabled to detect a skyline of a horizon relative to the
SAMD, an orientation determination unit enabled to determine the
orientation of the skyline detector, and a processor in signal
communication with the skyline detector and orientation
determination unit. The processor may be enabled to determine the
solar access of the predetermined location by calculating the
position of the sun at different times of the day and year relative
to the skyline.
[0013] Other systems, methods and features of the invention will be
or will become apparent to one with skill in the art upon
examination of the following figures and detailed description. It
is intended that all such additional systems, methods, features and
advantages be included within this description, be within the scope
of the invention, and be protected by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention can be better understood with reference to the
following figures. The components in the figures are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. In the figures, like
reference numerals designate corresponding parts throughout the
different views.
[0015] FIG. 1 is an example of an implementation of the Solar
Access Measurement Device ("SAMD") in relation to open area and the
sun.
[0016] FIG. 2 is a block diagram of an example of an implementation
of the SAMD.
[0017] FIG. 3 is an example of a wide angle image captured with the
skyline detector of the SAMD shown in FIG. 2.
[0018] FIG. 4 shows an example of a calibration image captured by
the skyline detector of FIG. 2.
[0019] FIG. 5 shows an example of sun paths.
[0020] FIG. 6 shows an example of a superimposed sun path and
skyline image generated by the SAMD of FIG. 2
[0021] FIG. 7 shows a flowchart of an example of operation of the
SAMD shown in FIG. 2.
[0022] FIG. 8 shows an example of a "hot-spot" diagram generated by
the SAMD of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] In the following description of the preferred embodiment,
reference is made to the accompanying drawings that form a part
hereof, and which show, by way of illustration, a specific
embodiment in which the invention may be practiced. Other
embodiments may be utilized and structural changes may be made
without departing from the scope of the present invention.
[0024] A Solar Access Measurement Device ("SAMD") is disclosed. The
SAMD may be utilized as a "solar mapper" that is useful in the
design and installation of solar energy systems and a variety of
other situations where solar radiation exposure needs to be
measured, such as landscaping, architecture, ecological studies,
fisheries, forestry, golf course management, realtors/appraisers,
universities/technical schools, utility companies, etc. In general
operation, the SAMD may capture a digital image with a wide angle
lens of a skyline and measure the magnetic orientation and
inclination of the image. The SAMD may then process the image to
locate the skyline in the image and then predict the paths of the
sun throughout the day and year for the particular latitude of the
SAMD. The SAMD may then determine the amount of annual solar
radiation that will impinge the location of the SAMD.
[0025] In FIG. 1, an example of an implementation of the SAMD 100
is shown in relation to an open area and the sun 102. The open area
may include solar obstacles such as, for example, a mountain 104,
tree 106, hill, building, or other type of structure (not shown).
The open area may also include the skyline 108 that is the line
along which the surface of the earth, or solar obstacles, and the
sky appear to meet in the horizon 110 relative to the SAMD 100. In
general, the skyline 108 is the boundary between the open
unobstructed sky and any earth-bound objects and includes all
obstacles that will block the sun 102 at different times of the day
and year, such as trees, buildings and mountains. In operation, the
SAMD 100 captures an image of the horizon 110 and utilizes the
captured image of the horizon 110 to determine the solar radiation
exposure at the location of the SAMD 100.
[0026] In FIG. 2, a block diagram of an example of an
implementation of the SAMD 200 is shown. The SAMD 200 may include a
skyline detector 202, orientation determination unit 204, processor
206, memory 208, optional output device 210, optional input device
211, and optional communication bus 212. The processor 206 may be
in signal communication with the skyline detector 202, orientation
determination unit 204, memory 208, optional output device 210,
optional input device 211 and optional communication bus 212 via
signal paths 214, 216, 218, 220, 221 and 222, respectively. The
SAMD 200 may also include a GPS sensor 224.
[0027] The skyline detector 202 is a device capable of detecting
the skyline of the horizon relative to the SAMD 200. The skyline
detector 202 may be implemented in various configurations utilizing
different components.
[0028] As an example, the skyline detector 202 may include a
calibrated image sensor (such as, for example, a calibrated
electronic camera) having a sensor array and equipped with an
ultra-wide angle fixed focal length lens such as a "fisheye" lens
(not shown). The lens allows the image sensor to capture an image
of the surrounding structures, trees and other obstructions in a
semi-spherical range of 180 degrees in elevation (i.e., the
vertical direction) and 360 degrees in azimuth (i.e., the
horizontal direction) in relation to the SAMD 200. An ultra-wide
angle lens may also be utilized that has less than 180 degrees
degree field of view ("FOV"). In this example some of the relevant
skyline may not be captured, and a small error in the solar access
calculations may result. However, an advantage of using a lens with
less than 180 degrees field of view is that they are typically less
expensive. The skyline detector 202 may further include a processor
(not shown) and software (not shown) capable of analyzing the
captured image and locating the skyline in the captured image. It
is appreciated by those skilled in the art that the processor (not
shown) in the skyline detector 202 and the processor 206 may be the
same processor or separate processors based on design preference
for the SAMD 200.
[0029] In an example of operation, the image sensor of the skyline
detector 202 may be pointed vertically at the sky, or alternatively
in the southern direction (if the SAMD 200 is located in the
northern hemisphere) or in the northern direction (if the SAMD 200
is located in the southern hemisphere), and held level until the
image is captured. In general, the image sensor may be mounted to
an enclosure (not shown) of the SAMD 200 that defines a
predetermined pointing direction of the image sensor such that
while the enclosure is held level, the image sensor may be pointing
straight up or at another predetermined inclination relative to the
enclosure. When the image sensor is oriented vertically and the
lens has 180 degrees field of view, the resultant captured image by
the image sensor will incorporate the entire sky and skyline
through which all possible locations of the sun will occur
throughout the day and year. If the lens has less than 180 degrees
FOV or the image sensor is oriented in a direction other than
vertically, some of the relevant skyline may not be captured and a
small error in the solar access calculations may result. However,
an advantage of orienting the image sensor, for example, towards
the south (in the northern hemisphere), is that the portion of the
sky through which the "hottest" sun (i.e., the summer and midday
sun) passes is more towards the center of the lens and image
sensor. This is useful since ultra-wide angle lenses typically
compress the image around the periphery of the image and provide
more detail towards the center. More detail in the hottest region
of the sky may lead to a more accurate determination of the
location of the skyline in that region and therefore a more
accurate estimate of solar access.
[0030] The image sensor may include circuitry capable of
automatically adjusting the gain of the image sensor to accommodate
outdoor light conditions. For example, if the sun is exposed in the
field of view of the image sensor at the time the image is
captured, the sensor gain may be automatically reduced to prevent
saturation of the image sensor. Additionally, the image sensor lens
may also have a filter that reduces the amount of light that hits
the sensor array within the image sensor.
[0031] In another example, the skyline detector 202 may instead
have two or more image sensors (i.e., two electronic cameras) each
with narrow angle lenses instead of a single fisheye lens. In this
example, each of the image sensors may produce an image and all
images may be "stitched" together by software in the skyline
detector 202. The resulting stitched image would be a wide
horizontal angle image similar to an image produced with a single
fisheye wide-angle lens. Therefore, this implementation example
allows the use of standard lens in the skyline detector 202 instead
of a special purpose fisheye lens. Additionally, the use of two or
more images in this example may produce a resultant image with a
wider angle field of view than the standard fisheye lens. As an
example, if the skyline detector 202 includes two 100 degree FOV
image sensors and the first image sensor is oriented such that one
points 50 degrees off the center of the SAMD 200 and the other
image sensor is pointed 50 degrees off the center in the opposite
direction, the resulting combined image (or "stitched image") would
have a FOV of 200 degrees, which is more than a typical fish-eye
lens (which typically has 180 degree FOV).
[0032] In yet another example, the skyline detector 202 may include
a single image sensor with a narrow angle lens, for example, 45
degree FOV lens. In this example, the skyline detector 202 (or
image sensor) may be swept slowly across the skyline by the user or
with an optional sweeping device (not shown) and the skyline
detector 202 may capture multiple images while the SAMD 200 records
the orientation of the skyline detector 202 each time an image is
captured with, for example, an electronic compass and electronic
inclinometer. The software in the skyline detector 202 then
"stitches" the images together using the compass and level readings
to form a larger wide-angle image. The optional output device 210
(such as an LCD display) may display a fixed wide-angle image
centered to the south (if the SAMD 200 is located in the northern
hemisphere) or in the northern direction (if the SAMD 200 is
located in the southern hemisphere) that gets built up with each
new image capture.
[0033] In yet another example, the skyline detector 202 may include
a semispherical mirror utilized in conjunction with a narrow FOV
lens and image sensor. In an example of operation, the mirror
reflects a wide angle image of the skyline into the narrow FOV lens
of the image sensor.
[0034] In yet another example, the skyline detector 202 may include
a servo driven laser rangefinder instead of an image sensor and
lens. The laser may be directed over a broad area of the sky
pointing to all the locations where the sun will appear throughout
the day and year. The laser range finder may include a reflection
detector. The reflection detector detects when the laser is
reflected by an object in the path of the laser. The SAMD 200 then
keeps track of where objects were detected. A resulting open sky
matrix may be generated by recording all orientations of the laser
with no reflected light.
[0035] The processor ("the skyline processor") (not shown) in the
skyline detector 202 may be any device capable of analyzing the
images captured by the image sensor or reflections detected by the
laser range finder and may be the same as the processor 206. In
general, the skyline processor analyzes the captured images to
locate the skyline where the novel techniques described below may
be utilized for locating the skyline in the captured image.
Generally, these techniques produce a set of pixels that describe
where in the image the open sky is and where in the image the
obstructions are.
[0036] For example, the image pixels of the captured image may be
scanned column by column. An intensity derivative function may be
performed on the image pixels by starting at the top of a column
and moving pixel by pixel down the column. Since the sky is much
brighter than the obstacles below the skyline, the intensity
derivative will be largest between the pixel just above the skyline
and the pixel just below. The coordinates between these pixels in
the image plane may be stored as the location of the skyline in
that column. More reliable performance may be achieved by averaging
groups of pixels and using the groups to locate the skyline. The
process may then be repeated for every column. By starting from the
top of each column, the process is more likely to succeed since
open sky will generally fill the top of the image. An estimate of
the RGB (red, green, blue) color or luminosity of the sky may be
established by scanning a predetermined area of the sky, for
example the top 20% of the image, and averaging the pixels. This
area is more likely to be open sky. This value may then be utilized
to determine, for example, if the first pixel or group of pixels in
a column is already below the skyline.
[0037] Alternatively, a two dimensional derivative may also be
utilized in which the intensity derivative is calculated along each
row as well as down each column. The result is a two-dimensional
derivative gradient from which the normal direction of the skyline
may be calculated along the skyline. An edge detection scheme may
then be utilized to locate the gradient peak. A reference
intensity/color may be established, as described above, and used to
select a threshold for doing the edge detection.
[0038] The orientation determination unit 204 is a device capable
of determining the orientation of the SAMD 200 (or the skyline
detector 202). The orientation determination unit 204 may include a
compass (not shown) and an inclinometer (not shown) both of which
may be either mechanical or electronic. The orientation
determination unit 204 may also include a GPS unit or may be in
signal communication with optional GPS sensor 224. It is
appreciated by those skilled in the art that orientation may
include a three-dimensional pointing direction and/or attitude of a
device, such as the device's pointing direction relative to the
magnetic orientation within a plane that is perpendicular to the
Earth's gravitation vector. Additionally, orientation may also
include the pointing direction of the device in both elevation,
azimuth, and two-dimension pitch relative to a level position where
the level position may be defined as being within the plane that is
perpendicular to the Earth's gravitational field.
[0039] As an example, the orientation determination unit 204 may
include a mechanical compass such as a needle in fluid that rotates
to point in the direction of magnetic north. In this example, the
SAMD 200 (or a user of the SAMD 200) points the lens of the skyline
detector 202 towards true south (in the northern hemisphere) or
true north (in the southern hemisphere) utilizing the magnetic
compass and predetermined knowledge of the magnetic declination in
that region. Alternatively, the lens of the skyline detector 202 is
pointed toward magnetic south (in the northern hemisphere) or
magnetic north (in the southern hemisphere) by using the magnetic
compass and the user inputs, into the SAMD 200, the magnetic
declination for the region and the skyline processor makes the
appropriate correction to the orientation of the captured image
digitally. The SAMD 200 may include a table of magnetic
declinations for different regions and the user would enter the
region into the SAMD 200 and the SAMD 200 would determine and
correct for the magnetic declination.
[0040] In another example, the orientation determination unit 204
may include an electronic compass. In this example, the pointing
direction need not be precisely controlled by the user. The user
points the lens of the skyline detector 202 within a designated
window, or tolerance, around true south (in the northern
hemisphere) or true north (in the southern hemisphere). For
example, the tolerance is +/-10 degrees from the desired pointing
direction. In this example, the SAMD 200 would measure the actual
pointing direction using the electronic compass at the time the
image is captured. Then the processor 206 would digitally correct
for any deviation from true south (in northern hemisphere) or true
north (in southern hemisphere) taking into account magnetic
declination. Correction may be accomplished, for example, by
transforming a digital image matrix by a correction amount or
transforming a sun path matrix where the digital image matrix and
sun path matrix are described below.
[0041] The orientation determination unit 204 may include a
mechanical dual axis inclinometer such as a bubble level, which is
a bubble inside a fluid that is centered in a small circle when the
bubble level is laying level in both axis directions. In this
example, the user would hold the SAMD 200 horizontally and
vertically level when the image is captured.
[0042] In another example, the orientation determination unit 204
may include an electronic inclinometer. In this example, the
skyline detector 202 need not be held precisely level by the user.
The user holds the SAMD 200 level to within a designated window, or
tolerance, around 0 degrees of tilt in both directions such as, for
example, +/-10 degrees from 0 degrees of tilt. In this
implementation example, orientation determination unit 204 measures
the actual dual axis tilt angles at the time the image is captured.
Then the processor 206 digitally corrects for any deviation from 0
degrees. Again, the correction may be accomplished, for example, by
transforming the digital image matrix by the correction amount or
transforming the sun path matrix.
[0043] In another example, the orientation determination unit 204
may include at least two gyroscopic or accelerometer sensors. In
this example, an initial orientation reference may be made by
orienting the SAMD 200 at a known reference orientation and
direction with known azimuth and elevation relative to the SAMD
200, such as level and toward magnetic south. Any relative motion
of the SAMD 200 with respect to the reference orientation may be
sensed by the gyroscopic sensors. As a result, the azimuth and
elevation pointing direction of the skyline detector 202 may be
determined as it is moved. In another example, the known reference
is the current location of the sun. Based on the current time of
day, day of year, latitude, and either longitude or the timezone
for the location of the SAMD 200, the azimuth and altitude of the
sun is determined. The sun is located in the image plane of the
image sensor in the skyline detector 202. This serves as the known
reference.
[0044] It is appreciated by those skilled in the art that the
orientation determination unit 204 may be an external and/or
internal device to the SAMD 200. Additionally, orientation
measurement devices such as compasses, inclinometers,
accelerometers, gyroscopes, or similar measurement sensors may also
be internal or external to the orientation determination unit 204.
As an example, a user my utilize external orientation measurement
sensors or predetermined knowledge of orientation data to manually
orient the orientation determination unit 204, skyline detector
202, and/or SAMD 200 or to manually input the user orientation
information to the orientation determination unit 204, skyline
detector 202, and/or SAMD 200.
[0045] Generally, a latitude where the data is being collected by
the SAMD 200 is needed. The latitude is preferably accurate to
within, for example, +/-0.5 degrees, but may also be within a wider
range, for example, +/-3 degrees. Small errors in latitude result
in small errors in the estimated solar access. Alternatively, a
user may enter the region of the world where the data is being
collected, for example, northern California, and the SAMD 200 may
determine the latitude from a table of regions in memory. This is
done once when the SAMD 200 is first set up and does not need to be
done again as long as the user remains in the same latitude band.
Software in the processor 206 analyzes the detected skyline and
based on the latitude, magnetic orientation (from compass), and
inclination (from inclinometer), accurately predicts the sun's
travel through the sky throughout the day and throughout the year.
The captured skyline and open sky are then overlaid on top of the
cumulative region of the sky through which the sun will pass (the
"sun paths") and the software may accurately predict when in the
day and year shadows will occur in the spot where the data was
taken.
[0046] Compass and inclination feedback may be given to the users
as they are preparing to capture the image. Then once the image is
captured, in the case of an electronic compass and electronic
inclinometer, the actual compass and inclination readings are used
to make minor corrections to the captured image or sun paths in the
case that the image sensor is not held facing directly south (in
the northern hemisphere) and/or perfectly level. The user may need
to orient the image sensor to within a designated window. This
designated window is determined by how much correction may be made
to the captured image or sun paths. In this example, the skyline
image is matched up with the predicted paths of the sun. Additional
corrections for magnetic declination may be made for the particular
region where the magnetic declination is the deviation of true
north from magnetic north.
[0047] The optional output device 210 may be any device capable of
displaying and/or outputting data related to the solar access of
the SAMD 200. As an example, the optional output device 210 may be
an image display device. The optional input device 211 may be any
device capable of allowing a user or external device (not shown) to
manually or mechanically input external information about the
location, orientation, and/or position of the SAMD 200. As an
example, the optional input device 211 may be a touchscreen or
keypad. The memory 208 may be any type of storage device or memory
that is capable or storing data or software for the processor 206
such as, for example, random access memory ("RAM"), read only
memory ("ROM"), cache memory, or hard drive. The optional
communication bus 212 is any device capable of allowing the SAMD
200 to electronically communicate information and/or data to a
storage device (not shown) external to the SAMD 200.
[0048] FIG. 3 is an example of a wide angle image 300 captured with
the skyline detector 202 of the SAMD 200. As an example, the wide
angle image 300 may include a roof 302 of a structure (not shown),
solar panels 304, trees 306, and skyline 308. In order for the
processor 206 to calculate the sun paths and overlay them on the
wide angle image 300, the skyline detector 202 is first
calibrated.
[0049] The skyline detector 202 may be calibrated by capturing an
image 400 of objects that have known azimuth and elevation angles
relative to the SAMD 200 as shown in FIG. 4. These known elevations
can be established, for example, with a calibrated transit level or
other device capable of accurately measuring the elevation and
azimuth of one location relative to another. As an example, the
skyline detector 202 may be calibrated by first making wall marks
402 on the walls 404, ceiling marks 406 on the ceiling 408 and
floor marks 410 on the floor 412 of a predefined room. Each mark
may be labeled and spaced at regular intervals of elevation and
azimuth angles. Then an image 400 may be captured with the SAMD 200
of the walls, ceiling and floor within the predefined room.
[0050] The image 400 may then be analyzed by the processor 206 or
manually by the user and each known calibration point within the
image 400 (i.e., each wall mark 402, ceiling mark 406, and floor
mark 410) may be associated with a pixel in the image 400 that
falls in the center of the calibration point. Then an interpolation
may be performed by the processor 206 to fill in the areas in
between the calibration points, and an extrapolation may be
performed to extend beyond the calibration points at the edges of
the image. The result is a calibrated image plane in which the
azimuth and elevation angles of every pixel in the calibrated image
relative to the orientation of the SAMD 200 is known.
Alternatively, the skyline detector 202 may be calibrated by
mathematically modeling the optics of the lens and image plane such
that the angular relationship between each pixel in the image plane
is known and the angular relationship between each pixel and the
enclosure of the SAMD 200 is known.
[0051] In an example of operation, the SAMD 200 may utilize a
calibration/verification technique using the sun's location in the
image plane as detected by the skyline detector 202. Generally, the
location of the sun at any given time, date, and latitude is known
from planetary motion. The sun's location may be determined from
the captured image in the skyline detector 202 combined with the
compass and inclinometer readings from the orientation
determination unit 204. If a time and date are also maintained in
the SAMD 200 by a timing device (not shown), there would be
redundant known data variables, i.e., latitude, time, date, and sun
location. It is appreciated by those skilled in the art that
generally any one of these variables could be deduced from the
other three.
[0052] It is further appreciated that the location of the sun in
the sky may be calculated from latitude on earth, time of day and
day of year from equations well known in the field of astronomy. As
an example, by calculating the location of the sun every, for
example, 30 minutes, through an entire day, a sun path may be
determined for that day. By calculating the sun paths for every day
of the year, a sun band can be determined. This band includes all
locations of the sun throughout the day and throughout the year.
The band may then be mapped into a matrix that represents where in
the image the sun paths would appear. An example of a plot 500
showing all sun paths is shown in FIG. 5. In FIG. 6, an example of
a skyline image 600 with sun path grid lines 602 superimposed on
the captured image 300 of FIG. 3 is shown. The area 604 of the sun
paths that is in open sky is shaded (as denoted by crosshatching).
From this shaded region 604 the total solar energy that will
impinge the location of the SAMD 200 may be calculated.
[0053] In an example of operation, once the open sky matrix has
been identified and the sun paths matrix has been calculated, the
two matrices may be analyzed by the processor 206 to generate a
third matrix representing the intersection of the open sky and the
sun band. The intersection matrix corresponds with the shaded area
604 in FIG. 6. In general, the "open sky matrix," "sun paths
matrix," and "intersection matrix" are each two-dimensional binary
arrays indexed by elevation and azimuth. A `0` in a cell of the
open sky matrix indicates that the sun is blocked (i.e., below the
skyline) at that elevation and azimuth. A `1` indicates that the
sun is not blocked and is therefore part of the open sky. A `0` in
a cell of the sun paths matrix indicates that the sun is never at
that elevation and azimuth at any time during the year. A `1`
indicates that at some time and day the sun is at that elevation
and azimuth and is therefore part of the sun paths. The
intersection matrix is the logical AND of the open sky and sun
paths matrices. This intersection matrix is further analyzed to
determine all times of day and days of year when the sun is in open
sky that is not obstructed from view at the location of the device
by some obstacle. A fourth two-dimensional matrix called the "solar
access matrix" can be generated by calculating the solar radiation
of the sun for every elevation and azimuth corresponding to a `1`
in the intersection matrix. The solar radiation is based on the
solar constant (approximately 1367 W/m.sup.2) and the angle of the
sun relative to the angle of the collector panel. The above steps
of detecting the skyline, mapping the sun paths, and calculating
the solar access for any given time period may be performed quickly
or even "instantaneously", that is, the steps all occur in simply
the amount of time required for the electronics and processors to
operate. The SAMD 200 does not need to be left out in the sun for
an extended period of time. In general, the sun does not even need
to be present in order for the SAMD 200 to measure the solar access
of the location. Modifications may be made to the data to account
for tree leaf loss. For example, evergreen trees do not loose their
leaves and so will cast the same shadows year round. Deciduous
trees may be identified by the user and can be treated differently
by the processor 206. For example, if the data was collected during
a season when the tree has little or no leaves, the processor 206
can assume shading during the leaf bearing months of the year. If
the data was collected during a season when the tree has most or
all of its leaves the processor 206 can assume less shading during
the months when the tree will loose its leaves.
[0054] The solar access matrix is a set of data that may be
formatted in many different ways. For example, it may be integrated
across time of day and day of year to get a single number that is
the cumulative annual sun exposure in W*h/m.sup.2 for the
particular location. This could then be converted to a
Kilowatt-hour (KWhr) number representing the predicted electrical
energy generation of a particular solar panel configuration, size,
and technology (e.g., Crystalline Silicon, Amorphous Silicon "Thin
film", etc). Or it may be converted to a dollar amount if Net
Metering and/or Time-of-Use metering is used to interconnect with
the utility. Further, more detailed, representations of the data
may be made. For example: a bar chart of solar radiation in each
month of the year, a recommended direction in which to move the
panels to improve production, a recommended tilt angle for the
panels, or a suggestion of obstacles to remove to improve solar
exposure (the obstacle may be identified in the skyline image and
if it's a tree, it could be trimmed). A database of average
temperatures for the region may be used in the calculation of the
power generated by the panels because panels produce different
amounts depending on their temperature.
[0055] It is appreciated by those skilled in the art that some of
the energy coming from the sun is lost due to passing through the
atmosphere and clouds. The software in the processor 206 may
correct for these effects with the clearness index ("KT") for the
given location. A database of KT values for different locations is
obtained by measuring solar radiation continuously over time and
recording the average solar energy year for year. This annual solar
radiation data is available from groups such as NREL (National
Renewable Energy Laboratory) and may be incorporated in the memory
(not shown) of the processor 206.
[0056] In operation, the SAMD 200 determines the solar access of a
location of the SAMD 200 based on a digital image taken by the SAMD
200. As an example of operation, the SAMD 200 may perform the
process described by the flowchart 700 of FIG. 7. The process
begins in step 702 and in step 704, the user may make a course
adjustment to the orientation of the SAMD 200 to within a
designated window. The SAMD 200 then captures an image with an
image sensor and establishes the latitude of the device in step
706. The SAMD 200 then locates the exposed sky in the captured
image and calculates the sun paths over one or more designated time
periods based on the latitude in step 708. Next, in step 710, the
SAMD 200 maps the sun paths onto the captured image. The process
then ends in step 712.
[0057] The process may also further include the steps of
calibrating the image plane of the image sensor of the SAMD 200
prior to making a course adjustment to the orientation of the SAMD
200; identifying where the exposed sky and the sun paths overlap;
and calculating the amount of solar energy that reaches the
location of the SAMD 200. The image plane may be calibrated by
associating each pixel or group of pixels with the azimuth and
elevation angles of the light vector passing through the lens of
the image sensor and hitting the pixel or group of pixels relative
to the orientation of the SAMD 200.
[0058] The course adjustment to the orientation of the SAMD 200 may
be an adjustment in magnetic orientation and in inclination
relative to the earth's gravity. The designated window may be
centered on the vector pointing towards magnetic south (in the
northern hemisphere) or north (in the southern hemisphere) and
perpendicular to the earth's gravitational field.
[0059] Location of the skyline in the captured image may be done by
image processing in the processor 206 or an external processor (not
shown) in signal communication via the optional communication bus
212. Generally, light areas in the top of the image are assumed to
be open sky and the boundary between the light sky and the dark
earth-bound objects is the skyline. The intersection may be found
using an intensity derivative along columns of pixels.
[0060] As an example, the orientation of the SAMD 200 may be
established simultaneously with capturing the image. The
orientation of the SAMD 200 is the magnetic orientation of the SAMD
200 and the dual axis inclination of the SAMD 200. As an
implementation example, the magnetic orientation may be measured
using an electronic compass, and the inclination is measured using
an electronic dual axis inclinometer.
[0061] The SAMD 200 may implement a method in which matrices are
used to manipulate the data. The image captured by the image sensor
can be thought of as a matrix of pixels. The pixel (i, j) is the
pixel in the i.sup.th row and j.sup.th column of the image plane. A
calibration step associates each pixel or groups of pixels with the
elevation and azimuth angles of the light ray passing through the
image sensor lens and hitting the pixel or group of pixels. The
result is the image plane calibration matrix,
IMAGE.sub.cal=(.theta..sub.c, .phi..sub.c).sub.i=1 . . . C, j=1 . .
. R. (.theta..sub.c, .phi..sub.c).sub.ij is an elevation and
azimuth angle pair defining a vector relative to the three degree
orientation of the SAMD 200 O=(.THETA.,.PHI.,.GAMMA.).sub.device,
where .THETA. is the elevation offset angle defined as the angle of
deviation of the pointing direction of the SAMD 200 from the plane
that is normal to the direction of the earth's gravitational field
vector (i.e., deviation from level front to back). .PHI. is the
azimuth offset angle defined as the angle of deviation of the
pointing direction of the SAMD 200 from magnetic south (in the
northern hemisphere) or north (in the southern hemisphere) where
rotation is about the axis that is equivalent to the earth's
gravitational field vector. F is the horizon offset angle defined
as the deviation about the axis of the pointing direction of the
SAMD 200 of the plane of the SAMD 200 from the plane that is normal
to the direction of the earth's gravitational field vector (i.e.,
deviation from level side to side). The calibration is made for
each pixel by iterating for i=1 to R and j=1 to C, where R is the
total number of rows, and C the total number of columns, in the
image plane. Alternatively, groups of pixels are calibrated.
[0062] Next a course adjustment is made by the user to the
orientation vector O of the SAMD 200 to within a designated window
around (0,0,0). (0,0,0) represents a known orientation, for example
due south, and level relative to the earth's gravitational field
along two axes. Next an image is captured.
[0063] As an example, the designated window may be wide, for
example +/-10 degrees. In this example, simultaneously with
capturing the image, the actual orientation may be measured, for
example, with an electronic compass and electronic inclinometer. In
another example, a mechanical compass and bubble level may be used
by the user to orient the SAMD 200 within the designated window and
the designated window may be narrow, for example, +/-2 degrees in
all axes. In this case, deviation in orientation from (0,0,0)
results in error in the outcome of estimate of solar radiation.
Alternatively, only the compass is electronic and the inclinometer
is mechanical or only the inclinometer is electronic and the
compass is mechanical. In either of these cases, the axis measured
by the electronic sensor may have a wide designated window.
[0064] Next, the current image plane azimuth/elevation matrix,
IMAGE=(.theta., .phi.).sub.i=1 . . . C, j=1 . . . R is calculated
from the calibration matrix, IMAGE.sub.cal, and the orientation
vector of the SAMD 200, O. (.theta., .phi.).sub.ij is the elevation
and azimuth angles relative to the vector that is pointing south
(in the northern hemisphere) or north (in the southern hemisphere)
and normal to the gravitational field vector (i.e., level). IMAGE
is calculated by transforming the IMAGE.sub.cal matrix by the
orientation O. For example, if the O=(1, -2, 0), then
IMAGE=(.theta., .phi.).sub.ij=(.theta..sub.c,
.phi..sub.c).sub.ij-(1, -2).
[0065] Next the captured image is mapped to the image plane
azimuth/elevation matrix IMAGE by associating pixel.sub.i,j in the
image with (.theta., .phi.).sub.ij. Then the exposed sky is located
within the captured image as described earlier. Then the located
skyline is used to define a subset SKY of matrix IMAGE consisting
of all pixels representing exposed sky.
[0066] Next the latitude of the SAMD 200 is entered by the user, or
alternatively it may be measured with an optional GPS sensor 224.
The sun paths are calculated throughout the day and year. The sun
paths are then mapped onto the matrix IMAGE, defining a subset SUN
of the matrix IMAGE that represents locations of the sun within the
image plane throughout the day and year.
[0067] Next a matrix EXPOSURE is defined and calculated as the
intersection of the matrices SUN and SKY. A weighed integration of
the matrix EXPOSURE across rows and columns is performed to obtain
the total solar energy that hits the location. Weighting may be,
for example, based on solar intensity for elevation and azimuth,
average weather patterns, clearness index (KT), orientation of
exposed surface, etc.
[0068] In one example of operation, a system installer maps out an
area quickly by taking multiple samples in different locations. The
SAMD 200 may instantly calculate the total power generation for
each location on, for example, a roof-top or ground site and then
records the GPS coordinates if an optional GPS sensor 224 is
utilized in the SAMD 200. The software then interpolates in between
the data points to predict solar exposure in areas between the
sample locations. The software may then show the "hottest" area of
the proposed system (i.e., the area with the greatest solar
access). The software may also show where the shadows will mostly
fall and may suggest, for example, the optimal configuration of the
panels of a solar collection system.
[0069] Interpolation and extrapolation of solar access in between
and beyond a sparse set of samples is done by the processor 206,
which records the elevation and azimuth angles of each distinctive
obstruction that makes up the skyline. By locating the same
obstacle in images from different perspectives, the software may
utilize triangulation to get distances to obstructions. Then
shadowing in between and beyond sample locations may be
predicted.
[0070] An example of what the display might show after 6 sample
points have been taken indicating the six vertices of the proposed
system layout is shown in FIG. 8 where each data point is generated
by the process described above (i.e., detecting the skyline,
calculating the total solar energy, etc). Alternatively, the user
may take samples on a rough grid across the roof or area of the
proposed installation, and the software may show the optimal
location for the solar panels.
[0071] As another example, the SAMD 200 may map a potential
installation area with a boundary and show the potential solar
radiation as described above, but without the optional GPS sensor
224. In this example, a starting reference point may first be
established and a reading taken. Then a user may pace in a
direction, incrementing a counter via a four-way joystick type
button in the direction the user is pacing with each pace. Then
another sample may be taken. Next the user paces in another
direction. The SAMD 200 may then keep track of the approximate
position of the SAMD 200 utilizing dead-reckoning. The pace
distance may be "calibrated" by the user measuring the approximate
length of a pace and entering it into the SAMD 200 with the
optional input device 211. Alternatively, the X-Y distance from the
reference to each point may be measured (such as with a measuring
tape) and entered into the SAMD 200. Alternatively, the SAMD 200
may include a dual axis accelerometer or gyroscopic sensor (not
shown) that allows the SAMD 200 to utilize dead-reckoning (after a
reference location is first established) based on integrating the
gyroscopic or accelerometer readings to track the movement of the
SAMD 200 and determine the location of the SAMD 200 relative to the
reference location.
[0072] In another example of operation, the calibrated image plane
may be used as an electronic transit level. A transit level may be
utilized in construction to determine the azimuth and elevation
angle of something or somewhere in a construction site. The user
looks through an eye piece and positions the cross hairs on the
point of interest then azimuth and elevation can be read off.
Alternatively the user moves an object until it reaches a desired
azimuth or elevation be setting the transit level to the desired
angles and moving the object until it comes in view in the eye
piece. The SAMD 200 may be utilized in a similar fashion by
capturing an image of the scene. The user may then query the
azimuth or elevation angle of a point in the image by clicking on
it or in some other way telling the software which pixel
corresponds to the location of interest, and the SAMD 200 reports
back the angles. Alternatively, the desired angles are entered into
the SAMD 200 and a box or cross hair appears in the image at the
location entered. The user then moves the object until it is inside
the box or on the cross hairs in the image. In this example, the
SAMD 200 captures a new image each time the object is moved.
[0073] In yet another example of operation, the SAMD 200 may be
used to position satellite antennas. When directing an antenna at a
geosynchronous satellite, it is desirable to have the dish both
point in the direction of the satellite and avoid obstructions
between the dish and the satellite. In this example, the SAMD 200
may include a skyline detector 202, compass and inclinometer, and a
database of azimuth and elevation angles of all known satellites.
The skyline detector may locate the skyline in the direction of the
satellite and the SAMD 200 may determine the intersection of any
obstacles with the line of site between the dish and the satellite.
As a result, the SAMD 200 may provide a figure of merit to the user
for a particular desired location of the dish and suggest a
direction in which to move the dish. Alternatively, the optional
output device 210 (such as image display) may show an image of the
skyline and superimposed on the image the optional output device
210 may show the location of the satellite. The user may then see
in the optional output device 210 where the satellite is being
obstructed. Because many home owners prefer satellite dishes to be
out of view, it is often necessary to balance between strong signal
reception and aesthetics and the SAMD 200 may help optimize this
tradeoff.
[0074] In another example of operation, the SAMD 200 may include
software and/or a database of plants and their preferred light
conditions. Different plants and trees grow best with different
amounts of daily, monthly, or yearly sunlight. In this example, the
SAMD 200 may be utilized by landscapers and landscape architects to
choose the plants and trees for a location in a garden or yard. The
amount of sun that hits a particular location is dramatically
affected by the shading characteristics of that location. The SAMD
200 may measure the amount of sun access at a location taking into
account shading and suggest plants that would grow best.
[0075] In another example of operation, the SAMD 200 may be
interfaced to a three-dimensional computer-aided design ("3D CAD")
software system. The solar access data may be integrated with the
CAD drawings for a new house or building. The user may then
simulate how sunlight will interact with the new structure. For
example if there is a large tree in front of the house, it may be
determined if that tree will block morning sun in the winter. Then
the house design may be modified if different lighting is desired.
This is also useful for architects integrating passive solar design
aspects into the house. In this design methodology, solar heating
of floors, walls, etc is considered in the building design to
optimize heating the house in the winter and cooling the house in
the summer. Again the combined solar radiation data in the 3D CAD
model may be used to modify the design to optimize different
aspects of the structures interaction with the sun.
[0076] In another example of operation, the SAMD 200 may measure
ambient light (as opposed to just direct sunlight). This is useful
for planning new construction in which it is desirable to optimize
natural lighting inside the building. The skyline is captured and
the open sky is identified. The amount of ambient light is measured
by integrating over the open sky region. In the planning of a new
building in, for example, a crowded urban site, it may be desirable
to know the ambient light exposure that would be received at
different levels of a new building. Hence, if an
interpolation/extrapolation scheme is used to fill in exposure data
in between data points, as an example, this may be done in three
dimensions as opposed to two dimensions as described earlier. The
third dimension will be in the elevation direction to give data for
different floor levels of the new building.
[0077] In another example of operation, the SAMD 200 may include a
processor operable to identify windows in a captured image take
from inside a house. The SAMD 200 may then calculate the amount of
sun that enters through the window. This SAMD 200 may be used by
realtors showing a house to a potential buyer that is interested in
how much sun enters the house and at what time of day and year.
[0078] Persons skilled in the art will understand and appreciate,
that one or more processes, sub-processes, or process steps
described may be performed by hardware and/or software.
Additionally, the process described above may be implemented
completely in software that would be executed within a
microprocessor, general-purpose processor, combination of
processors, digital signal processor ("DSP"), and/or application
specific integrated circuit ("ASIC"). If the process is performed
by software, the software may reside in software memory in the
memory 208, processor 206, skyline detector 202 processor, an
external processor (not shown) in signal communication with the
optional communication bus 212, or combination. The software in
software memory may include an ordered listing of executable
instructions for implementing logical functions (i.e., "logic" that
may be implemented either in digital form such as digital circuitry
or source code or in analog form such as analog circuitry or an
analog source such an analog electrical, sound or video signal),
and may selectively be embodied in any computer-readable medium for
use by or in connection with an instruction execution system,
apparatus, or device, such as a computer-based system,
processor-containing system, or other system that may selectively
fetch the instructions from the instruction execution system,
apparatus, or device and execute the instructions. In the context
of this document, a "machine-readable medium", and/or
"computer-readable medium" is any means that may contain, store,
communicate, propagate, or transport the program for use by or in
connection with the instruction execution system, apparatus, or
device. The computer-readable medium may selectively be, for
example but not limited to, an electronic, magnetic, optical,
electromagnetic, infrared, or semiconductor system, apparatus, or
device. More specific examples, but nonetheless a non-exhaustive
list, of computer-readable media would include the following: an
electrical connection (electronic) having one or more wires; a
portable computer diskette (magnetic); a random access memory
("RAM") (electronic); a read-only memory ("ROM") (electronic); an
erasable programmable read-only memory ("EPROM" or Flash memory)
(electronic); an optical fiber (optical); and a portable compact
disc read-only memory ("CDROM") (optical).
[0079] It will be understood that the foregoing description of
numerous implementations has been presented for purposes of
illustration and description. It is not exhaustive and does not
limit the claimed inventions to the precise forms disclosed.
Modifications and variations are possible in light of the above
description or may be acquired from practicing the invention. The
claims and their equivalents define the scope of the invention.
* * * * *