Abstract:
Presented is a motorized roller shade that includes a flexible shade material, a rotatably supported roller tube that windingly receives the flexible shade material, one or more flexible photovoltaic cells disposed on the flexible shade material, and a motor operably engaging the roller tube to rotate the roller tube to move the flexible shade material, where the motor receives power from the one or more flexible photovoltaic cells.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates generally to roller shades, and more particularly to a motorized roller shade having photovoltaic shade material. 
         [0003]    2. Background 
         [0004]    Currently, to power the motor of a motorized roller shade, the motor must be electrically connected to AC or DC power or to one or more batteries. Connecting one or more motorized shades to AC or DC power either requires each shade motor&#39;s AC or DC adapter being plugged into a nearby outlet or having AC wires routed through walls to each shade motor. Powering a shade motor with one or more batteries requires having to replace or recharge those batteries when the batteries cease to provide power. 
       SUMMARY OF THE INVENTION 
       [0005]    It is to be understood that both the general and detailed descriptions that follow are exemplary and explanatory only and are not restrictive of the invention. 
       DISCLOSURE OF THE INVENTION 
       [0006]    In one aspect, the invention involves a roller shade. The roller shade include a flexible shade material, a roller tube configured to windingly receive the flexible shade material, and one or more flexible photovoltaic cells disposed on the flexible shade material. 
         [0007]    In one embodiment, the one or more flexible photovoltaic cells are printed directly on the flexible shade material. In another embodiment, the one or more flexible photovoltaic cells are printed onto a flexible substrate and the flexible substrate is attached to the flexible shade material. 
         [0008]    In another aspect, the invention involves a method of providing power to a roller shade motor. The method includes providing a flexible shade material, providing a rotatably supported roller tube that windingly receives the flexible shade material, disposing one or more flexible photovoltaic cells on the flexible shade material, providing a motor that operably engages the roller tube to rotate the roller tube to move the flexible shade material, establishing electrical communication between the motor and the one or more flexible photovoltaic cells, and exposing the one or more flexible photovoltaic cells to sunlight to generate electricity that powers the motor when the flexible shade material needs to be moved. 
         [0009]    In one embodiment, disposing the one or more flexible photovoltaic cells on the flexible shade material comprises printing the one or more flexible photovoltaic cells directly on the flexible shade material. In another embodiment, disposing the one or more flexible photovoltaic cells on the flexible shade material comprises printing the one or more flexible photovoltaic cells onto a flexible material and attaching the flexible material to the flexible shade material. In still another embodiment, the method further includes exposing the one or more flexible photovoltaic cells to sunlight to generate electricity that recharges one or more batteries when the flexible shade material does not need to be moved. 
         [0010]    In still another aspect, the invention involves a motorized roller shade. The motorized roller shade includes a flexible shade material, a rotatably supported roller tube windingly receiving the flexible shade material, one or more flexible photovoltaic cells disposed on the flexible shade material, and a motor operably engaging the roller tube to rotate the roller tube to move the flexible shade material, where the motor receives power from the one or more flexible photovoltaic cells. 
         [0011]    In one embodiment, the one or more flexible photovoltaic cells are printed directly on the flexible shade material. In another embodiment, the one or more flexible photovoltaic cells are printed onto a flexible material and the flexible material is attached to the flexible shade material. In still another embodiment, the motorized roller shade further includes a charge controller in electrical communication with the one or more flexible photovoltaic cells. In yet another embodiment, the motorized roller shade further includes a rechargeable battery in electrical communication with the motor and the charge controller. 
         [0012]    In another embodiment, the charge controller directs power from the one or more photovoltaic cells to the motor or to the rechargeable battery. In still another embodiment, the one or more flexible photovoltaic cells are transparent. 
         [0013]    In yet another embodiment, the motorized roller shade further includes a voltage sensor in electrical communication with the one or more flexible photovoltaic cells, where the voltage sensor measures voltage from the one or more flexible photovoltaic cells. In still another embodiment, the motorized roller shade further includes a processor or microcontroller in communication with the voltage sensor and the motor, where the processor or microcontroller controls the motor to move the flexible shade material in response to the voltage measured by the voltage sensor. 
         [0014]    In another embodiment, the motor receives power from the one or more flexible photovoltaic cells only when the voltage sensor measures a voltage above a minimum threshold. In still another embodiment, the motor receives power from a rechargeable battery when the voltage sensor measures a voltage below a minimum threshold. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]    The accompanying figures further illustrate the present invention. Exemplary embodiments are illustrated in reference figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered to illustrative rather than limiting. 
           [0016]    The components in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0017]      FIG. 1A  is an illustrative isometric front view of a roller shade with photovoltaic cells disposed on the flexible shade material, according to one embodiment of the invention. 
           [0018]      FIG. 1B  is an illustrative isometric rear view of the roller shade of  FIG. 1A . 
           [0019]      FIG. 2  is an illustrative view of a photovoltaic panel connection wire routing path through a roller tube, according to one embodiment of the invention. 
           [0020]      FIG. 3  is an illustrative block diagram of a roller shade motor assembly, according to one embodiment of the invention. 
           [0021]      FIG. 4  is an illustrative flow diagram of the flow of power from the photovoltaic panel to the shade motor and battery, according to one embodiment of the invention. 
           [0022]      FIG. 5  is an illustrative circuit diagram of a photovoltaic cell and battery powered roller shade motor, according to one embodiment of the invention. 
           [0023]      FIG. 6  is an illustrative orthographic front view of a roller shade disposed in a window, according to one embodiment of the invention. 
           [0024]      FIG. 7  shows illustrative plots of sun intensity and shade height vs. time, according to one embodiment of the invention. 
           [0025]      FIG. 8  shows illustrative plots of rate of change of sun intensity and shade speed vs. time, according to one embodiment of the invention. 
           [0026]      FIG. 9  shows illustrative plots of solar voltage and smoothing function vs. time, according to one embodiment of the invention. 
           [0027]      FIG. 10  is an illustrative table of scaling data for three sun intensities, according to one embodiment of the invention. 
           [0028]      FIG. 11  is an illustrative table of the improvement in accuracy before and after the scaling factors of  FIG. 10  are applied. 
       
    
    
     LIST OF REFERENCE NUMBERS FOR THE MAJOR ELEMENTS IN THE DRAWING 
       [0029]    The following is a list of the major elements in the drawings in numerical order. 
         [0030]      100  roller shade 
         [0031]      102  flexible shade material 
         [0032]      104  rolled portion 
         [0033]      106  hembar 
         [0034]      108  roller tube 
         [0035]      110  linear portion 
         [0036]      112  front side 
         [0037]      114  rear side 
         [0038]      116  flexible photovoltaic cell 
         [0039]      118  photovoltaic panel 
         [0040]      120  interconnect wire 
         [0041]      202   a  wire 
         [0042]      202   b  wire 
         [0043]      204  through-hole 
         [0044]      206  sidewall 
         [0045]      208  bore 
         [0046]      300  shade motor assembly 
         [0047]      302  charge controller 
         [0048]      304  voltage sensor 
         [0049]      306  battery 
         [0050]      308  shade motor 
         [0051]      310  processor/microcontroller 
         [0052]      402  Voltage is created by sunlight striking the photovoltaic panel 
         [0053]      404  The voltage creates a current that flows to the charge controller 
         [0054]      406  Does the shade need to be moved? 
         [0055]      408  Power is delivered directly to the motor 
         [0056]      410  Power is directed to the float charger 
         [0057]      412  Shade finished moving? 
         [0058]      502  Schottky diode 
         [0059]      504  battery charging circuitry 
         [0060]      602  window 
         [0061]      604  windowpane 
         [0062]      606  window frame 
         [0063]      702  period of extended darkness 
         [0064]      704  shade raised an open position 
         [0065]      706  rapid increase in sun intensity 
         [0066]      708  rapid lowering of shade 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0067]    Reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. 
         [0068]    Unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. 
       Mode(s) for Carrying Out the Invention 
       [0069]    The present disclosure involves combining advanced photovoltaic (PV) technology with a motorized roller shade. The motorized roller shade includes a flexible shade material. This flexible shade material incorporates flexible (i.e., bendable, rollable) photovoltaic cells into or onto the flexible shade material, thereby making the flexible shade material act as a flexible photovoltaic (i.e., solar) panel 
         [0070]    Referring to  FIGS. 1A and 1B , a roller shade  100  is shown. The roller shade  100  includes a roller tube  108  and a flexible shade material  102  wound therearound creating a rolled portion  104 . The roller shade  100  further includes a hembar  106  attached to the end of a linear portion  110  of the flexible shade material  102 . The roller shade  100  further includes a one or more flexible photovoltaic cells  116 . The one or more flexible photovoltaic cells  116  are disposed on a front side  112  and/or a rear side  114  of the flexible shade material  102 , depending on the orientation of the roller shade when hung over a window. If there are two or more flexible photovoltaic cells  116  disposed on the flexible shade material  102 , the two or more flexible photovoltaic cells  116  are connected to each other, either in series or in parallel, via interconnect wires  120 . The one or more flexible photovoltaic cells  116  together on the flexible shade material  102  form a photovoltaic panel  118 . 
         [0071]    Referring to  FIG. 2 , wires  202   a  and  202   b  extend from the end of the flexible shade material  102  that is coupled to the roller tube  108  by methods known in the art. The wires  202   a  and  202   b  extend through a through-hole  204  in a sidewall  206  of the roller tube  108 , and through the bore  208  of the roller tube  108 . The wires  202   a  and  202   b  provide an electrical connection between the flexible photovoltaic cells  116  and a charge controller  302  housed in a shade motor assembly  300 . In some embodiments, a voltage sensor  304  (see  FIG. 3 ) is also housed in the shade motor assembly  300 . The wires  202   a  and  202   b  are protected by the rolled portion  104  once the flexible shade material  102  is wound around the roller tube  108 . 
         [0072]    Referring to  FIG. 3 , in one embodiment, a block diagram of the shade motor assembly  300  is shown. The shade motor assembly  300  includes the charge controller  302 , the voltage sensor  304 , a processor or microcontroller  310 , a rechargeable battery  306 , and a shade motor  308 . In various embodiments, the charge controller  302  collects the charge from the photovoltaic array  118  and charges the battery  306 , which in turn, provides power to the motor  308 ; or the charge controller  302  supplies charge directly to the motor  308 , and is discussed in further detail below. In one embodiment, the voltage sensor  304  is used to measure the voltage from the photovoltaic array  118  for the purpose of controlling the position of the roller shade  100 , and is discussed in further detail below. 
         [0073]    The flexible photovoltaic cells  116  were developed at the Massachusetts Institute of Technology. The flexible photovoltaic cells  116  (and interconnecting wires  120 ) are printed directly onto a substrate-independent surface (e.g., the flexible shade material  102 ). This printing process is accomplished by using vapors instead of liquids at temperatures less than  120  degrees Celsius. Five subsequent layers of the PV material are printed (inside a vacuum chamber) on the substrate to create an array of flexible photovoltaic cells. This process allows printing the flexible photovoltaic cells either directly onto the shade fabric, or onto a secondary flexible material that can then be attached to the flexible shade material  102  via sewing, gluing, or by other methods known in the art. 
         [0074]    Similar flexible photovoltaic cells have been produced by Ubiquitous Energy. These flexible photovoltaic cells are also transparent and are undetectable by the human eye. These photovoltaic cells involve efficient harvesting of infrared light without affecting the visible spectrum. They utilize the excitement characteristic of small band-gap molecules that leads to oscillator bunching in order to harvest the infrared light. The small band-gap allows for greater electrical conductivity, as seen in metals, but more flexibility. In addition, the electrons can now move more freely and become elevated into the conduction band with less energy. This provides efficiencies between 21% and 35%. 
         [0075]    In various embodiments, the charge controller  302  uses the DC output voltage of the photovoltaic panel  118  to provide the rechargeable battery  306  (e.g., either NiCd or LiFePO4) with a float-charge throughout the battery lifecycle. This allows the battery  306  to be charged at a rate similar to the rate at which it discharges. This prevents the battery  306  from being over-charged. The charge controller  302  senses when the battery  306  has a full charge and ceases all charging until the battery  306  charge falls below a specified threshold. 
         [0076]    Referring to  FIG. 4 , a flow diagram of the flow of power from the photovoltaic panel  118  to the shade motor  308  and battery  306  is shown. First, voltage is created by sunlight striking the photovoltaic panel  118  (Step  402 ). Next, the voltage creates a current that flows to the charge controller  302  (Step  404 ). A determination is then made regarding whether the roller shade  100  needs to be moved (i.e., raised or lowered) (Step  406 ). If the roller shade does not need to be moved, power is directed to the charge controller  302 , which determines if the battery  306  needs to be charged (Step  410 ). If the roller shade does need to be moved, power is delivered directly to the shade motor  308  (Step  408 ). Thereafter, the shade motor  308  is monitored to determine when it stops (i.e., when the roller shade  100  no longer needs to be moved) (Step  412 ). If the roller shade still needs to be moved, power is delivered directly to the shade motor  308  (Step  408 ). 
         [0077]    Referring to  FIG. 5 , in another embodiment, a circuit diagram of a photovoltaic cell and battery powered roller shade motor is shown. Schottky diodes  502  are used because of their low voltage drop and high recovery rate. The Schottky diodes  502  allow the shade motor  308  to be powered by either the photovoltaic panel  118  or the battery  306 , whichever produces the larger voltage. Excess voltage from the photovoltaic panel  118  is used to charge the battery  306  via the battery charging circuitry  504  (e.g., float charger). 
         [0078]    As mentioned above, in one embodiment, the battery  306  is disposed in the motor assembly  300 . In other embodiments, the battery is disposed in, or on a top of, a housing near the shade motor to reduce wire length and visibility. In still another embodiment, the battery is disposed inside the shade roller tube. 
         [0079]    Referring to  FIG. 6 , roller shade  100  with motor assembly  300  mounted in a frame  606  of a window  602  is shown. As discussed above, the roller shade  100  includes flexible shade material  102  with flexible photovoltaic cells  116  disposed thereon. Specifically, the flexible photovoltaic cells  116  are disposed on the rear surface  114  of the flexible shade material  102  and facing the windowpanes  604 . When the roller shade  100  is in a closed position (i.e., the flexible shade material  102  is unwound from the roller tube  108 ), more of the flexible photovoltaic cells receive incident sunlight. When the roller shade is in an open position (i.e., the flexible shade material is wound up around the roller tube), less of the flexible photovoltaic cells receive incident sunlight. 
         [0080]    The disclosed motorized roller shade is more efficient and more powerful than existing roller shades, is aesthetically pleasing to the end user, and provides advanced functionality using adaptive movement. The disclosed motorized roller shade is also completely self-sufficient because no external power source (and associated wiring) is required. Consequently, the disclosed motorized roller shade causes no increase in energy usage/expense. 
         [0081]    Specifically, the photovoltaic panel  118  (i.e., flexible shade fabric  102  with attached flexible photovoltaic cells  116 ) generates enough current to recharge an internal or external shade motor battery (enabling a battery lifetime of &gt;10 years), or power the shade motor directly, depending on the amount of sunlight incident on the photovoltaic panel  118 . In one embodiment, in the case of prolonged darkness (e.g., night time), in order to conserve as much battery energy as possible, the shade motor  308  receives power directly from the photovoltaic panel  118  during the day and receives power from the battery  306  only at night. If, during the day, the solar voltage does not meet or exceed a specified threshold (e.g., cloudy, rainy), then the battery  306  is used to power the shade motor  308 . 
         [0082]    Because the photovoltaic cells  116  are printed directly on the flexible shade material  102 , the photovoltaic cells  116  are unobtrusive. The photovoltaic cells  116  cover the entire flexible shade material  102 , which allows for a larger contact surface (as compared with conventional solar panels) for incident sunlight to power the shade motor  308  and/or charge the shade motor battery  306 . Additionally, because the photovoltaic panel  118  has a large contact surface area, greater electricity production can be achieved in comparison to conventional photovoltaic cells. 
         [0083]    Referring again to  FIG. 3 , in another embodiment, as mentioned above, the voltage sensor  304  is in electrical communication with the photovoltaic array  118  and is used to measure/monitor the voltage from the photovoltaic array  118 . The measured voltage is proportional to the suns intensity and can be scaled and used to control the shade motor  308  to move the roller shade  100  to a specific height. The voltage sensor  304  communicates with the processor or microcontroller  310  to control the shade motor  308  to automatically move the shade in response to the intensity of the light incident on the photovoltaic array  118 . 
         [0084]    As the intensity of sun decreases, the output voltage of the photovoltaic panel  118  decreases. The voltage decrease is sensed by the voltage sensor  304 . The voltage sensor  304  reports the voltage decrease to the processor or microcontroller  310 , which in turn controls the shade motor  308  to raise the shade  100  based on a particular voltage threshold (i.e., sun intensity) and duration at that voltage threshold. 
         [0085]    As the intensity of the sun increases, the voltage output of the photovoltaic panel  118  increases. The voltage increase is sensed by the voltage sensor  304 . The voltage sensor  304  reports the voltage increase to the processor or microcontroller  310 , which in turn controls the shade motor  308  to lower the shade  100  based on a particular voltage threshold (i.e., sun intensity) and duration at that voltage threshold. 
         [0086]    Referring to  FIG. 7 , example plots of sun intensity vs. time and shade height vs. time are shown. According to sun intensity vs. time plot, the sun intensity remains below a certain threshold for an extended period of time  702  (e.g., night time). The voltage sensor  304  reports this voltage to the microcontroller  310 , which raises the shade  100  in response thereto  704 . At some time thereafter, the sun&#39;s intensity drastically increases above the certain threshold  706  (e.g., sunrise). The voltage sensor  304  reports this drastic voltage increase to the microcontroller  310 , which rapidly lowers the shade  100  in response thereto  708 . 
         [0087]    While roller shade  100  is in motion, reading of output voltage is suspended until the shade has stopped moving and can adjust itself for the new reading based on the how much of the photovoltaic panel  118  surface area is now hidden on the roller tube  108 . 
         [0088]    Referring to  FIG. 8 , plots of rate of change of sun intensity and shade speed vs. time are shown. According to the plots, it can be seen that the shade speed increases or decreases proportionally as the rate of change of sun&#39;s intensity increases or decreases. 
         [0089]    In other embodiments, the sensor/processor/microcontroller will move the shade according to sensitivity levels set by the user. In other embodiments, a smoothing function (See  FIG. 9 ) is used to smooth out peaks and troughs in the photovoltaic cell voltage from the photovoltaic panel  118 . 
         [0090]    In still other embodiments, a manual or override mode is included for situations where the user does not want the shades to move automatically in response to sun intensity, such as when privacy is required. The user may also schedule times when to use automatic mode or manual mode. 
         [0091]    In another embodiment, a scaling/weighting factor is used to account for differing output voltages due to dynamic shade position. This allows for a correct voltage output based upon the actual light intensity, and not the perceived voltage output dictated by the position of the shade and its photon striking area. More specifically, instances occur where the sun may be shinning extremely bright, but only a small area of a photovoltaic cell  116  receives incident photons. In this situation, the output voltage will be relatively low compared to when the full area of a photovoltaic cell  116  receives (is struck by) the same intensity of light. Additionally, if the shade is fully down, due to the increased photovoltaic cell surface area, even low intensity sunlight will still produce a relatively large voltage, which can be higher than the output voltage produced when high intensity sunlight is incident on a small area of the photovoltaic cell. This issue causes a problem with the sensor determining where to put the shade. In order to compensate for these differing output voltages so that the shade is moved to the correct position, a voltage scaling algorithm/factor is used, which takes into account the current position of the shade and the relative sun intensity. 
         [0092]    Referring to  FIG. 10 , an example of above-mentioned factor-based scaling implementation is shown. Three intensities are shown: the actual sun&#39;s intensity, the perceived intensity without a scaling factor, and the output intensity given by the voltage sensor after the scaling factor is implemented. Each of the intensities is ranked based upon their relative intensity descending between 1 and 10. Then, both the BEFORE and AFTER factor rankings are compared to the ACTUAL ranking. Referring to  FIG. 11 , a table of the improvement in accuracy (any number within 0.4 of a ratio of 1) before and after the scaling factor is applied is shown. 
         [0093]    In other embodiments, a supplemental shade sensor is used to measure the sun&#39;s intensity when the shade is fully up (i.e., completely raised). All voltage measurements (external and shade fabric) are calibrated to mesh seamlessly. 
         [0094]    In still another embodiment, instead of a supplemental external sensor, an optical “eye” mounted on the underside of the shade compartment is used to scan below the window to measure the intensity of sun passing through the glass. This allows for the photovoltaic panel to be completely rolled up and stored out of the way; requires no external sensor on a window or roof; and provides a more accurate depiction of the actual solar intensity passing through the window. 
         [0095]    In another embodiment, there are three sensitivity levels used by the sun intensity sensor to dictate movement of shade. These sensitivity levels include high, medium, and low. At the high sensitivity level, the shade will move up and down parallel to the sun&#39;s intensity in a first predetermined time interval (e.g., every 1 minute). During drastic increases and decreases in the sun&#39;s intensity, the shade will move immediately. The smoothing function described above is still applied, but much more frequent shade movement is seen at this sensitivity. At the medium sensitivity level, the shade will move up and down parallel to the sun&#39;s intensity in a second predetermined time interval (e.g., every 30 minutes). During drastic increases in the sun&#39;s intensity, the shade will move down. The shade will move up only during prolonged drastic decreases in the sun&#39;s intensity. The smoothing function described above is still applied, and a normal amount of shade movement is seen at this intensity. At the low sensitivity level, the shade will move up and down parallel to the sun&#39;s intensity in a third predetermined time interval (e.g., every 1 hour). Only during drastic prolonged increases and decreases in the sun&#39;s intensity will the shade move. The smoothing function described above is still applied, but much less frequent shade movement is seen at this sensitivity. The shade is more sensitive to moving down compared to moving up. A down-only mode can be activated to only move the shade down based upon larger solar intensities. 
         [0096]    In still another embodiment, the intensity of the sun and the percent change in the intensity of the sun is used to dictate motor speed. Depending on the sensitivity level set, the shade will move at specific intervals throughout the day. When the shade is required to move, the shade motor controller (e.g., processor, microcontroller) queries the sensor for an intensity level. This intensity level will correspond to a predetermined shade level set by the installer. If the new intensity level is 10% greater than the previous intensity level, the shade motor shall move 10% faster, and so on, up to the shade motor&#39;s maximum predetermined speed limit The percent increase in sun intensity will directly correlate to the shade motor speed. If there is a decrease in intensity, the shade motor will move at normal speed. If the percent change in the sun intensity is low, the shade will move a much slower rate. This will allow the quietest and most undetectable shade movement. All regular shade movements executed using the quietest setting on the shade motor. If the percent change in sun intensity is large, the shade motor speeds up to ensure that the high intensity sun is shining through the window for a minimal amount of time. 
         [0097]    In yet another embodiment, since the sun&#39;s intensity and the output voltage of a photovoltaic cell are linearly related, a simple factor based system is used. The base point of the output voltage is the voltage generated when the shade is fully down. All voltages are then scaled accordingly to that value; with each specific height level assigned a specific multiplying factor. 
       Alternate Embodiments 
       [0098]    Variations, modifications, and other implementations of what is described herein may occur to those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, the invention is not to be defined only by the preceding illustrative description.