WO2014185862A1

WO2014185862A1 - All-in-one solar powered lighting device

Info

Publication number: WO2014185862A1
Application number: PCT/SG2014/000210
Authority: WO
Inventors: Robert Christoph HAENDEL; Manuel Tobias DANNER; Thomas Gunter REINDL
Original assignee: National University Of Singapore
Priority date: 2013-05-14
Filing date: 2014-05-14
Publication date: 2014-11-20

Abstract

A solar cell illumination device and a method for fabricating such device is provided. The solar cell illumination device includes one or more photovoltaic cells, one or more illumination devices, electrical circuitry and a housing having a first portion. The electrical circuitry is electrically coupled to the one or more photovoltaic cells and the one or more illumination devices. The one or more photovoltaic cells are encapsulated within environmentally protective material and physically coupled to a top side of the first portion of the housing and the one or more illumination devices and the electrical circuitry are encapsulated within environmentally protective material and physically coupled to a bottom side of the first portion of the housing.

Description

ALL-IN-ONE SOLAR POWERED LIGHTING DEVICE

PRIORITY CLAIM

[0001] The present application claims priority to US Provisional Patent Application No. 61/ 823,121, filed May 14, 2013.

FIELD OF THE INVENTION

[0002] The present invention generally relates to photovoltaic devices and microelectronic devices for operating in harsh environments, and more particularly relates to an-all-in-one solar powered lighting device and a method for fabricating such.

BACKGROUND

[0003] Most street lamps in urban areas are coupled to and receive power from an electric grid. However, in rural areas and less developed areas or new developments in urban areas, there sometimes are no readily available electricity transmission media for providing street lamp power. Stand-alone solar street lamps have been developed to fill this need. The main challenge for such "off grid" solar street lamps is exposure to different environmental conditions. Solar photovoltaic (PV) applications must overcome the problem of protecting their electrical elements from environmental conditions such as rain, heat, moisture, dust, ultraviolet exposure and sudden temperature changes.

[0004] Typical solar street lamps protect the electrical circuits separately from the PV module such as enclosing the electrical circuits in special casings. These casings, however, add a large amount of extra cost to these lamps. In addition, varying weather conditions have a great impact on reliability and life time of the electrical components of the solar system. To overcome this issue special waterproof and dustproof casings have been used. These casings add additional cost to the off grid solar lamps and add more complexity to their construction leading to less scalable and more costly devices.

[0005] Thus, what are needed are solar street lamps that overcome these drawbacks and a scalable method of fabricating such devices. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.

SUMMARY

[0006] According to the Detailed Description, a solar cell illumination device is provided. The solar cell illumination device includes one or more photovoltaic cells, one or more illumination devices, electrical circuitry and a housing having a first portion. The electrical circuitry is electrically coupled to the one or more photovoltaic cells and the one or more illumination devices. The one or more photovoltaic cells are encapsulated within environmentally protective material and physically coupled to a top side of the first portion of the housing and the one or more illumination devices and the electrical circuitry are encapsulated within environmentally protective material and physically coupled to a bottom side of the first portion of the housing.

[0007] In addition, a method for fabricating a self-contained solar cell illumination device is provided. The method includes providing a layer of housing material having a first portion and a second portion, laminating one or more photovoltaic cells to a first side of the first portion of the housing material, and laminating one or more illumination devices and electrical circuitry to a second side of the first portion of the housing material, the second side opposite the first side. The method also includes forming the second portion of the housing material into a sealable compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to illustrate various embodiments and to explain various principles and advantages in accordance with a present embodiment.

[0009] FIG. 1 depicts a side planar view of a solar cell illumination device in accordance with a present embodiment.

[0010] FIG. 2, comprising FIGs. 2A and 2B, depicts perspective views of the device of FIG. 1 in accordance with the present embodiment, wherein FIG. 2A is a bottom front right perspective view of the device and FIG. 2B is a top rear right perspective view of the device.

[0011] FIG. 3 depicts an electrical block diagram of components of the device of FIG. 1 in accordance with the present embodiment.

[0012] FIG. 4, comprising FIGs. 4A and 4B, depicts planar views of the device of FIG. 1 during fabrication in accordance with the present embodiment, wherein FIG. 4A depicts a top planar view after connection of the photovoltaic cells in accordance with the present embodiment and FIG. 4B depicts a bottom planar view after connection of the illumination module and the electrical circuitry module in accordance with the present embodiment.

[0013] And FIG. 5 depicts a side cutaway view of the device of FIG. 1 magnified to show the layers applied during fabrication in accordance with the present embodiment. [0014] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale. For example, the dimensions of some of the elements in the block diagrams or flowcharts may be exaggerated in respect to other elements to help to improve understanding of the present embodiments.

DETAILED DESCRIPTION

[0015] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. It is the intent of the present embodiment to present an all-in-one solar powered illumination device for robust operation even in harsh operating conditions such as wet environments and tropical regions and a method for fabricating such.

[0016] Referring to FIG. 1, a side planar view 100 depicts a solar cell illumination device 102 in accordance with a present embodiment. The novel all-in-one solar powered illumination device 102 could serve as a street lamp with a photovoltaic (PV) module laminated with a transparent cover on an top side 104 of the device 102 and illumination elements and electric circuitry laminated on a bottom side 106 of the device 102. An aluminum sheet or other non-resilient ruggedized material serves as a housing and is fashioned at one end into a compartment 108 for locating a battery 110 and the lamination at the other end environmentally sealing all integrated components including an optional motion sensor 112 (whose location may be anywhere on the bottom side 106 of the device 102). [0017] The all-in-one solar powered illumination device 102 having the PV module laminated together with the illumination elements and electric circuitry solves the problem of protecting the different electronic components and light emitting diodes. In addition, this robust illumination device 102 provides further cost reductions for off grid lighting devices because there is no need to have an expensive weather resistant housing for the printed circuit board. Furthermore, the housing and connection process for the electronics is integrated into the PV module during the manufacturing process, as described below, which saves additional processing costs. In the case of a solar powered street lamp, the present embodiment can provide a fully integrated solution 40% to 50% of the cost of conventional off grid solar powered street lamps.

[0018] Another advantage of the fully integrated design of the solar powered illumination device 102 is that the electronic components are better protected thereby increasing their expected life time by protecting them completely from environmental influences such as humidity and dust. While weather resistance was always achievable by typical lamination of photovoltaic cells during their manufacture, the solar powered illumination device 102 provides a long term sealing of all components (excluding the battery 110) which can achieve an extended lifetime of more than twenty years. At the same time, the solar powered illumination device 102 combines all elements into a single, more scalable device. While designed for street lighting, the solar powered illumination device 102 can also provide lighting for walkways which require less power. Utilized with motion control via the motion sensor 112, the solar powered illumination device 102 has a longer lifetime. In addition, the solar powered illumination device 102 is particularly useful for rural electrification, especially in areas where the power grid is not always on or not available at all. Also, the solar powered illumination device 102 can be used for residential lighting, signboards, and other street and house outside lighting applications.

[0019] Referring to FIG. 2, comprising FIGs. 2A and 2B, perspective views 200, 250 depict the solar powered illumination device 102. FIG. 2 A is a bottom front right perspective view 200 of the device 102 and FIG. 2B is a top rear right perspective view 250 of the device 102. One or more illumination devices 202 such as light emitting diodes (LEDs) and electrical circuitry 204 are laminated onto the bottom side of the device 102 along with the motion sensor 112. The electrical circuitry 204 includes energy management circuitry, LED driving circuitry, and a microcontroller for charge control. The motion sensor 112 provides adaptive lighting thereby increasing battery and LED lifetime.

[0020] Ventilation openings 206, 208 are provided in the compartment 108 to provide a ventilated compartment for thermal management of the battery 110 (FIG. 1) inside. On the top side 104 of the device 102, photovoltaic (PV) cells 252 are provided as solar panels. The PV cells 252 also act as daylight sensors so that the electrical circuitry 204 can deactivate the illumination system during daylight hours and only activate the LEDs 202 at night and during low sunlight hours (e.g., very cloudy or rainy times of day). By combining the housing as a backsheet for the PV cells 252 and at the same time extending the housing so it can form the compartment 108 as a battery pack housing and using mounting openings 254 to affix the device 102 to a pole or other support significantly reduces the overall cost for the device 102. Implementing the device 102 with the LEDs 202 and a solar charge controller and utilizing batteries such as lithium or, more particularly, lithium iron phosphate (LiFeP0₄) batteries, makes the device 102 perfectly suited to be interchangeable and/or substitutable for solar street lamps currently available on the market. [0021] Referring to FIG. 3, an electrical block diagram 300 depicts key electrical components of the device 102. The electrical circuitry 204 includes power management circuits, LED driving circuits, solar charge controller circuits for the LiFeP0₄ batteries and light management system circuits (including the optional motion sensor). The electrical circuitry 204 is electrically coupled to the PV cells 252 arrayed on the top side 104 of the device 102 to receive current therefrom and using that current to charge the battery through connections 302 to the battery pack 110 (FIG. 1). The electrical circuitry 204 is also electrically coupled to the LED array 202 for driving them for illumination. In addition, the electrical circuitry 204 is electrically coupled to the motion sensor 112 for powering the motion sensor and for receiving motion detection input therefrom. The electrical circuitry 204 activates the LED array 202 in response to the motion detection input, thereby providing power conservation by only illuminating the device 102 when motion is detected nearby. Alternatively, the electrical circuitry 204 may include a dimming function that dims or brightens the lights in response to the motion detector and/or ambient light.

[0022] Referring to FIG. 4, comprising FIGs. 4A and 4B, planar views 400, 450 depict the device 102 during fabrication in accordance with the present embodiment. The top planar view 400 depicts the device 102 after physical connection of the photovoltaic cells 252 during fabrication in accordance with the present embodiment and the bottom planar view 450 depicts the device 102 after physical connection of the illumination module (the LED array 202) and the electrical circuitry 204 during fabrication in accordance with the present embodiment. The all-in-one housing depicted before fabrication of the device 102 where a first portion 402 of the housing including the PV module sealed onto the top side 104 and a printed circuit board with all electrical components including the illumination devices 202, the electrical circuitry 204 and the motion sensor 112 sealed onto the bottom side 106 and a second portion 404 of the housing for the compartment 108 are made from a single piece of rugged nonresilient housing material.

[0023] An initial step in the fabrication process in accordance with the present embodiment includes providing a layer of the rugged nonresilient housing material such as aluminum for the ruggedized housing 102. The housing material includes a first portion 402 and a second portion 404. The housing material also includes within the second portion 404 a compartment back portion 406, a compartment bottom portion 408, a compartment front portion, and side flaps 412 connected to either side of the compartment bottom portion 408 for forming compartment side portions.

[0024] A latter step in the fabrication process in accordance with the present embodiment includes forming the second portion 404 of the housing material into a sealable compartment, the compartment 108 (FIG. 1) by bending the compartment back portion 406, the compartment bottom portion 408, the compartment front portion 410 and the side flaps 412 around the battery pack 110 (FIG. 1) electrically coupled to the electrical circuitry 204. The compartment 108 is a sealable ventilated compartment with the compartment front portion 410 and the compartment bottom portion 408 having the ventilation openings 206, 208 formed therein to provide ventilation. In addition, as previously discussed, the mounting openings 254 formed in the compartment back portion 406 provide back mounting openings for mounting the device 102.

[0025] Additional photovoltaic cells 414, 416 can be mounted on the side flaps 412 for additional solar cell coverage. The battery pack 110 (FIG. 1) includes LiFeP0₄ batteries and the rugged housing material is preferably aluminum extruded to a thickness to allow bending during fabrication with relatively inexpensive bending equipment while providing a ruggedized non-resilient housing during use. The illumination devices 202 are preferably light emitting diodes (LEDs) formed in a LED array and including LEDs providing a high lumen to watt ratio.

[0026] Referring to FIG. 5, a side cutaway view 500 of the device 102 is magnified to depict the lamination process around the housing material (labeled 502) by showing the layers applied during fabrication in accordance with the present embodiment. The method for fabricating the device 102 includes laminating the PV cells 252 to the top side 104 of the first portion 402 of the housing material 502 and laminating the connections for the motion sensor 112, the LEDs 202 and the electrical circuitry 204 to the second side 106 of the first portion 404 of the housing material 502.

[0027] The laminating of the PV cells 252 to the first side 104 includes sealing a transparent cover 504 on top of the PV cells 252 to seal the PV cells 252 and a laminate 506 below the PV cells 252 to laminate the PV cells 252 to the aluminum sheet of the housing material 502. This process may also include laminating additional PV cells 414, 416 to the to the side flaps 412 is a similar manner.

[0028] The laminating of the LEDs 202 and the electrical circuitry 204 to the second side 106 of the first portion 404 of the housing material 502 includes sealing/encapsulating in a laminate the LEDs 202 and the electrical circuitry 204 in laminate layers 508, 510 with the connections 302 to the battery pack 110 passing through the laminate layer 510 at via 512. An opening is formed in the laminate material for the motion sensor 112 and it is glued onto the second side 106 of the first portion 404 of the housing material 502 at a later stage of fabrication.

[0029] As mentioned before, the preferable housing material 502 is aluminum, an electrical and thermal conductive material. With the heat conductive properties of aluminum, the housing material 502 acts as a "heat sink" for the LEDs 202 which generates heat during operation. The thermal properties and the housing's heat sink capabilities are not compromised by the solar powered device's 102 exposure to the "hot" sun because the usage pattern of the LEDs 202 only operate at night and when there is no sun such that the aluminum housing material 502 is able to absorb some or all of the heat generated by the LEDs 202. In order to further electrically and thermally insulate the LEDs 202 and the electrical circuitry 204 from the electrically conductive housing material 502, these electrical components are laminated to an insulative panel 514 by the lamination layer 508 and the insulative panel 514 is laminated to the second side 106 of the first portion 404 of the housing material 502 a lamination layer 516.

[0030] The lamination layers 506, 508, 10, 516 are preferably one or more layers of ethylene vinyl acetate (EVA) having an IP67 certification (IP certification refers to Ingress Protection certification and IP 67 refers to certification of the laminate material to totally protect against dust ingress (6) and certification of the laminate material to protect against immersion in water to a depth of fifteen centimeters to one meter (7)). The electrical circuitry 204 includes an integrated circuit that can function properly even after lamination into the device 102. By choosing the right parameters for the lamination process, it is possible to fully laminate the printed circuit board on the bottom of the module and at the same time guarantee a fully functioning electrical circuit on the bottom side which is fully protected from environmental influences. The process preferably includes operating the laminator at a positive pressure of one atmosphere, a negative pressure of approximately negative one atmosphere and a temperature of approximately 140°C for ten to fifteen minutes. This optimizes the temperature and the pressure to reduce bubbles in the lamination, to make sure lamination layers are connected and to prevent damage to the electronic components. [0031] The back sheet of the module for the PV cells can be a transparent cover as described above with encapsulant in different colors or even a transparent or fully light penetrable. Alternatively, glass can be used on the top side of the module. Additionally, the housing material 502 is an aluminum sheet to ensure good mechanical stability without requiring an extra frame on the outside edges for support. The same aluminum is also used to bend the housing for the battery compartment 108 and for fixture of the device 102 to a lamp pole or other support using the mounting openings 254.

[0032] Thus, in accordance with the present embodiment, an advantageous, robust, highly-scalable, fully integrated solar cell illumination device 102 has been presented for off grid street lamp applications and other stand-alone lighting applications which overcomes the drawbacks of the prior art. The device 102 addresses both the prior art issues regarding environmental protection and also design issues. By including a complete printed circuit board of the solar street lamp circuitry 204 including solar charge controller for the LiFeP0₄ batteries and the light management system- with the motion sensor into the device 102, complete weather protection can be guaranteed in which the device 102 is able to withstand harsh environmental conditions for more than twenty years. Even the LEDs can be implemented into the solar module in order to function as an off grid solar standalone application. While exemplary embodiments have been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. For example, those skilled in the art will realize from the teachings herein that the present technology may utilize any suitable laminating chemical and process which does not degrade the electronic components. [0033] It should further be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, operation, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements and method of operation described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.

Claims

CLAIMS What is claimed is:

1. A solar cell illumination device comprising:

one or more photovoltaic cells;

one or more illumination devices;

electrical circuitry electrically coupled to the one or more photovoltaic cells and the one or more illumination devices; and

a housing having a first portion, wherein the one or more photovoltaic cells are encapsulated within environmentally protective material and physically coupled to an top side of the first portion of the housing, and wherein the one or more illumination devices and the electrical circuitry are encapsulated within environmentally protective material and physically coupled to a bottom side of the first portion of the housing.

2. The solar cell illumination device in accordance with Claim 1 wherein the environmentally protective material encapsulating the one or more photovoltaic cells is integrally connected to the environmentally protective material encapsulating the one or more illumination devices and the electrical circuitry.

3. The solar cell illumination device in accordance with any of the preceding claims wherein the environmentally protective material comprises laminate.

4. The solar cell illumination device in accordance with any of the preceding claims wherein the housing comprises a second portion including a compartment, and wherein a battery coupled to the electrical circuitry is located in the compartment of the second portion.

5. The solar cell illumination device in accordance with Claim 4 wherein the compartment comprises a ventilated compartment and the second portion of the housing comprises one or more openings for ventilation.

6. The solar cell illumination device in accordance with either Claim 4 or Claim 5 wherein the battery is a lithium-type battery.

7. The solar cell illumination device in accordance with any of the preceding claims wherein the housing comprises a rugged non-resilient material.

8. The solar cell illumination device in accordance with Claim 7 wherein the rugged non-resilient material is electrically conductive, the solar cell illumination device further comprising an electrically insulative plate encapsulated within environmentally protective material and physically coupled between the bottom side of the first portion of the housing and the one or more illumination devices and the electrical circuitry.

9. The solar cell illumination device in accordance with either Claim 7 or Claim 8 wherein the rugged non-resilient material comprises aluminum.

10. The solar cell illumination device in accordance with any of the preceding claims wherein the one or more illumination devices comprise one or more light emitting diodes.

11. The solar cell illumination device in accordance with any of the preceding claims wherein the electrical circuitry comprises power management circuitry.

12. The solar cell illumination device in accordance with any of the preceding claims further comprising a motion sensor electrically coupled to the electrical circuitry and physically coupled to the bottom side of the first portion of the housing.

13. A method for fabricating a self-contained solar cell illumination device, the method comprising:

providing a layer of housing material having a first portion and a second portion;

laminating one or more photovoltaic cells to a first side of the first portion of the housing material;

laminating one or more illumination devices and electrical circuitry to a second side of the first portion of the housing material, the second side opposite the first side; and .

forming the second portion of the housing material into a sealable compartment.

14. The method in accordance with Claim 13 wherein the step of providing a layer of housing material comprises providing a layer of housing material having the second portion comprising a compartment back portion, a compartment bottom portion and a compartment front portion, the second portion further comprising two side flaps connected to either side of the compartment bottom portion for forming compartment side portions.

15. The method in accordance with Claim 14 wherein the step of forming the second portion into the sealable compartment comprises bending the compartment back portion, the compartment bottom portion, the compartment front portion and the compartment side portions around a battery electrically coupled to the electrical circuitry.

16. The method in accordance with either Claim 14 or Claim 15 wherein the compartment front portion and the compartment bottom portion have ventilation openings formed therein, and wherein the step of forming the second portion into the sealable compartment comprises forming the second portion into a sealable ventilated compartment.

17. The method in accordance with any of Claims 14 to 16 wherein the step of laminating one or more photovoltaic cells to the first side of the first portion of the housing material comprises laminating one or more photovoltaic cells to the first side of the first portion of the housing material and to the two side flaps of the second portion of the housing material.

18. The method in accordance with any of Claims 14 to 17 wherein the compartment back portion has mounting openings formed therein, and wherein the step of forming the second portion into the sealable compartment comprises forming the second portion into a sealable compartment with back mounting openings for mounting the self-contained solar cell illumination device.

19. The method in accordance with any of Claims 13 to 18 wherein the step of laminating the one or more illumination devices and the electrical circuitry to the second side of the first portion of the housing material comprises laminating the one or more illumination devices, the electrical circuitry and a motion sensor electrically coupled to the electrical circuitry to the second side of the first portion of the housing material.

20. The method in accordance with any of Claims 13 to 19 wherein the housing material comprises electrically conductive housing material, the method further comprising laminating an insulative panel to the second side of the first portion of the housing material, and wherein the step of laminating the one or more illumination devices and the electrical circuitry to the second side of the first portion of the housing material comprises laminating the one or more illumination devices and the electrical circuitry to the insulative panel laminated to the second side of the first portion of the housing material.