Note: Descriptions are shown in the official language in which they were submitted.
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SOLAR POWERED LAMP
[0001] This application claims the benefit of U.S. Provisional Application
No.
61/748,637, filed January 3, 2013, which is incorporated by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention is directed to a solar powered lantern having a
lighting
element powered by a rechargeable battery. The lighting element is formed
integrally with a bottle closure which can be threaded onto a discarded
plastic
bottle, such that the light emitting diodes (LEDs) of the lighting element
extend
into the bottle. A photovoltaic panel on the closure recharges the battery
during
sunlight hours.
[0003] The invention may be used to provide access to affordable light in
the developing world, and in the developed world may serve an aesthetic and/or
promotional purpose.
Description of the Related Art
[0004] More than 15 billion people in the developing world live off the
grid
without access to a reliable source of light after sunset. In many areas,
kerosene
lamps are the primary lighting source at a cost of approximately $2.50 per
month.
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These lamps have low output and can cause fire hazards and health problems.
Thus, it would be a desirable advance if "light poverty" could be addressed at
a
competitive price point with a sustainable and renewable light source.
SUMMARY OF THE INVENTION
[0005] These and other objects of the invention are achieved according to
the invention, in one aspect, with a solar powered lantern, comprising: a
translucent plastic base having a closed bottom end, a top end, and a threaded
opening at the top end. In preferred embodiments, the plastic base is a
discarded
plastic bottle such as a standard polyethylene terephthalate beverage
container,
which may be clear or colored. A threaded closure is provided mating with the
threaded opening at the top end of the base, having a flat top surface and a
photovoltaic panel arranged on the top surface. A rechargeable battery is
arranged on a side of the closure opposite the photovoltaic panel and is
connected to the photovoltaic panel. An elongated lighting element connected
to
the rechargeable battery is arranged on a side of the closure opposite the
photovoltaic panel and comprises an array of light emitting diodes (LEDs)
extending away from the top surface of the closure into the base.
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[0006] In another aspect, the lighting element is provided separately,
and
the user may adapt the lighting element in a discarded container to form a
lantern.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a perspective view of a solar lantern according to an
embodiment of the invention.
[0008] FIG. 2 depicts a lighting element according to an embodiment of
the
invention.
[0009] FIG. 3 depicts the interior of the top portion of the lighting
element
of FIG. 2.
[0010] FIG. 4 depicts the lower portion of the lighting element of FIG.
2,
comprising a tube with an elongated array of LEDs.
DETAILED DESCRIPTION OF THE INVENTION
[0011] A solar powered lantern according to the invention includes a
photovoltaic panel and a battery integrated into a cap or closure which fits
onto a
standard threaded opening of a plastic bottle, such as a conventional
polyethylene terephthalate (PET) bottle.
[0012] In the embodiment shown in FIG. 1, the lighting element 20
comprises a photovoltaic panel 30 on the top surface of the cap. The cap may
be
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approximately 55 mm in diameter, calculated to provide sufficient area so that
the photovoltaic panel can generate sufficient current to recharge the battery
for
a predetermined number of hours of operation at the desired light level, as
described below. The lighting element 20 screws onto the bottle 12 using the
same thread pattern as the original cap (in the case of a discarded and
recycled
base container), creating a water tight seal. This allows the bottle 12 to be
filled
with water to create a weighted base for the lantern. Alternatively, sand or
other
solid material may be added to the container to provide a weighted base.
Additional reflective materials may be provided in the container to increase
the
diffusivity of the light.
[0013] The lighting element 20 comprises a rechargeable battery which
powers an array of light emitting diodes (LEDs) extending into the container
12.
In the embodiment shown, four LEDs 22 are provided, however the number of
LEDs in the array may be left to the skill of the artisan to decide.
[0014] A "U-shaped" wire handle 40 acts as both a carrying handle and
ON/OFF switch. As shown in FIG. 3, a printed circuit board (PCB) 33 provides
the
circuitry to power the array of LEDs at different power levels and to power
different LEDs in the array. Small embossed tabs on the cap allow the
handle/switch 40 to click into three positions. In a first position on one
side, the
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lantern is off, while in the second position (vertical, for example) the
lantern is
FULL ON (all four LEDs lighted at full intensity). When the handle is at a
third
position, opposite the first position, the two LEDs opposite the handle are
ON,
creating a project specific task light that has the same irradiance as the
FULL ON
mode, but with twice the battery lifetime. The battery operation time at FULL
ON
mode with a full battery charge is preferably greater than 1 hour, more
preferably
greater than 2 hours and still more preferably 4 hours or greater.
[0015] The selection of the brightness of the LED array is also left to
the
skill of the artisan, and is preferably greater than 10 lumens, and more
preferably 20 lumens or greater. To meet the majority of international
standards (Lighting Africa, United Nations UNDESA, Nigeria SONCAP, etc.) it
may be preferable to achieve a minimum of 20 lumens in the FULL ON
condition. Using this design point, an exemplary but non-limiting
specification for the battery capacity and the solar panel capacity are set
forth in Tabled 1-3. This example is based on the production of 20 lumens
using four (4) LEDs, with a target operability of 4 hours per day. This
results in a design which requires approximately 1 watt-hour of energy to be
collected (by the solar panel) and stored (in the battery) as set forth in
Tables 1-3 below.
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TABLE 1
Lighting Element Design
#of LEDs 4
Correlated Color Temperature 6500 ol<
LED Current 20 nnA
Total Current (FULL Power) 80 nnA
LED Vforward 3.1 V
Total Wattage 0.248 W
Lumens/Watt 82 Inn/W
Total Lumen Output (Lantern Mode) 20.336 Inn
Total Lumen Output (Task Light Mode) 10.168 Inn
Desired Hours @ Full Intensity 4 hours
Energy Required (Watt-hrs) 0.992 W-hr
The photovoltaic panel is then designed to collect this amount of enery as
follows:
TABLE 2
PV Solar Panel
Power Density 0.115 nnW/nnnn2
Voltage per Cell 0.5 V
Number of Cells Required 8
Voc 4V
Vop (85% of Voc) 3.4 V
Number of Charge Hours 6.7 hrs
Total Watt-hr Density 0.00077 W-hr/nnnn2
PV Surface Area Required 1287.5 nnnn2
Linear Length (Square) 35.9 nnnn2
Diagonal Length 50.7 nnnn2
Array Configuration (8 cells): 2x4 Array
Individual Cell Size (x 8 pieces): 18x9 mm
Total Array Power 148.1 nnW
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[0016] In order to generate this amount of energy, using standard
polycrystaline photovoltaic cells the photovoltaic panel must have almost 1300
mm2 of surface area, yielding a 36x36mm square collection area, or diagonal
dimension of 51nnnn. In the selected design, the diameter of the cap is 55mm.
This solar panel may be made of eight (8) photovoltaic chips arranged in a 2 x
4
array, each photovoltaic chip being 9 x 18 mm in size, to provide ease of
handling
and limit breakage.
[0017] This collected solar energy is then stored in a rechargeable,
replaceable battery rated at 2000 charging cycles, such as an N-type LiFePO4
battery with 350nnA-hr capacity. This battery can be fully charged by the
solar
panel in under 8 hours, and will provide more than the desired 4 hours of use
at
full intensity in the lantern mode. In the task lighting mode the battery will
provide about 9 hours of light.
TABLE 3
Storage Reservoir
Battery Type: LiFePO4 N-size, (1)11.5 x 49nrirn
Battery Current Capacity: 350 nriA-hr
Nominal Voltage: 3.2 V
Battery Power Capacity: 1.1 W-hr
Light Lifetime (Full Power) 4.5 hr
Light Lifetime (Half Power) 9.0 Hr
Charge Time Required 7.6 Hr
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[0018] The cap may be made of an injection molded plastic (such as
acrylonitrile butadiene styrene (ABS) or equivalent) that provides the
structure for
the solar panel, the handle, the bottle threads, the lamp/battery assembly,
and a
tube containing the LED array. As shown in FIG. 3 and FIG 4, on one end of the
handle the switch assembly is attached to the underside of the solar panel
PCB.
The lap/battery assembly sits in a slot within solar panel PCB and is soldered
in
place to form the electrical connections.
[0019] The standard 3-postion switch is mounted on the bottom side of the
photovoltaic panel. Two small injection molded parts (ABS or equivalent) form
the switch mechanism. The first is the "saddle" which is fitted over the
switch.
The "lever" attaches to the wire handle and allows the switch to be turned to
the
first side, vertical and second side positions. A rectangular shape on the end
of
the wire keeps the lever from slipping.
[0020] The PCB may include a switch, a current limiting resistor for the
LEDs,
a dark current diode to prevent the panel from discharging the battery, and a
simple battery charger chip to protect the battery. While other electronics
may
be employed, this minimal configuration provides for a low manufacturing cost.
[0021] As shown in FIG. 4 optical tube 24 houses the LED array 22 and
battery 43. The tube 24 is provided a waterproof seal for these elements using
a
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small o-ring 44 at the top of the tube. This also provides the mechanical
element
that holds the tube in place inside the cap. Thus, the tube may be removed
from
the cap for replacement of the battery. When a new battery is inserted, the
tube
may be plugged back into the cap and snapped into place.
[0022] The optical tube is an injection molded part (clear ABS or
equivalent)
that provides refractive and reflective elements near the LEDs. These elements
are designed to capture the light emitted from each LED and redirect the light
downwards to create a uniform disk of light about 1 meter in diameter (when in
the lantern mode).
[0023] The LED array and battery are assembled with a basic fiberglass PCB
33 with a rectangular shape cut in the middle to house the battery. The LEDs
are
mounted on both sides of the board. The card edge style terminations on the
end
of the PCB 33 are right angle soldered directly to the photovoltaic panel and
provide the connections for the battery and for the LEDs.
[0024] In embodiments, the lantern may be provided with a power
management circuit to correspond with a daytime/nighttime usage scheme. A
cycle consists of 2 phases. The cycle starts during the morning time which is
the
charging phase. Followed by the nighttime/lighting phase during which the
stored
energy is utilized. When the sun comes up, sunlight falling on the
photovoltaic
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panel is converted to electric energy in the form of a direct current. The
direct
current generated charges the battery with the aid of the power management
circuit. The battery stores the electric energy for later use when the sun
goes
down or when the ambient light intensity drops below 5-15 Lux. A light sensor
may be provided to detect light intensity for this purpose. During the morning
time the light intensity switch will ensure that the circuit connecting the
battery
to the LEDs is open. This will prevent the battery from being drained by the
LEDs
to save all the energy produced for use when it is needed. When the sun goes
down the ambient light intensity will drop. Once the photovoltaic panel is no
longer producing significant electric energy, the light intensity sensor will
turn Off
the charging circuit and turn ON the LEDs' circuit, which functionality may
also be
complemented with a switch operation.
[0025] The battery, power management circuit, LED array, photovoltaic
panel and light sensor may be wired together to form two circuits that share
the
same battery, power management circuit and light sensor. The first circuit
connects the photovoltaic panel to the battery through the power management
circuit and the light sensor. The second circuit connects the battery, light
sensor
and the LED array. The light sensor ensures that only one of the two circuits
is
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closed depending on the ambient light flux. Using this daytime/nighttime usage
scheme, the lantern could effectively be positioned
[0026] The foregoing description of the preferred embodiments is not to be
deemed limiting of the invention, which is defined in the appended claims.
Sufficient information is provided in the foregoing that the skilled artisan
may
practice variants of the embodiments described without departing from the
scope
of the invention. Features described in connection with one embodiment, and
dependent claims described in connection with one independent claim maybe
combined with each other, with other embodiments, and with other independent
claims without departing from the scope of the invention.
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