Solar street lights consist of 5 main parts: solar panel, lighting fixture, rechargeable battery, controller, and pole. Solar panels convert solar energy to electricity which charges the battery during the day. The battery then powers an LED lamp in the lighting fixture at night. Controller regulates charging and lighting. Solar street lights were installed in the Sundarbans Tiger Reserve in India to provide lighting while reducing costs and maintenance compared to grid-connected street lights.
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SOLAR LED STREET LIGHT
3. Introduction
Solar street lights are raised light sources which are powered
by photovoltaic panels generally mounted on the lighting structure. The
photovoltaic panels charge a rechargeable battery, which powers
a fluorescent or LED lamp during the night.
Types:
Each street light can have its own photo voltaic panel,
independent of other street lights. Alternately, a number of panels can be
installed as a central power source on a separate location and supply power
to a number of street lights.
Implementation in the Sunderbans:
Solar street lights were installed
in the Sundarban Tiger Reserve (STR) in August 2008 and April 2009 with
assistance from the Forest Protection Committee and the STR officials.
Each household in the region were provided with a home light connection
by the WWF so that the people feel responsible for the security of the
installed solar street lights.
4. Features
Most solar panels turn on and turn off automatically by
sensing outdoor light using a light source . Solar streetlights are
designed to work throughout the night. Many can stay lit for more
than one night if the sun is not available for a couple of days. Older
models included lamps that were not fluorescent or LED. Solar
lights installed in windy regions are generally equipped with flat
panels to better cope with the winds.
Latest designs use wireless technology and fuzzy
control theory for battery management. The street lights using this
technology can operate as a network with each light having the
capability of performing on or off the network.
5. Components
Solar street lights consist of 5
main
parts :
Solar Panel
Lighting Fixture
Rechargeable Battery
Controller
Pole
6. Componets Description
Solar Panel:
Solar panel is one of the most important parts of solar street lights, as solar
panel will convert solar energy into electricity. There are 2 types of solar
panel: mono-crystalline and poly-crystalline. Conversion rate of mono-
crystalline solar panel is much higher than poly-crystalline.
Lighting Fixture:
LED is usually used as lighting source of modern solar street light, as the
LED will provide much higher Lumens with lower energy consumption. The
energy consumption of LED fixture is at least 50% lower than HPS fixture
which is widely used as lighting source in Traditional street lights. LEDs lack
of warm up time also allows for use of motion detectors for additional
efficiency gains.
7. Rechargeable Battery[edit]
Battery will store the electricity from solar panel during the day and provide energy to the
fixture during night. The life cycle of the battery is very important to the lifetime of the
light and the capacity of the battery will affect the backup days of the lights. There are
usually 2 types of batteries: Gel Cell Deep Cycle Battery and Lead Acid Battery and many
more.
Controller[edit]
Controller is also very important for solar street light. A controller will usually decide to
switch on /off charging and lighting. Some modern controllers are programmable so that
user can decide the appropriate change of charging, lighting ,dimming and also for timing.
Pole[edit]
Strong Poles are necessary to all street lights, especially to solar street lights as there are
often components mounted on the top of the pole: fixtures, panels and sometimes
batteries. However, in some newer designs, the PV panels and all electronics are integrated
in the pole itself. Wind resistance is also a factor..
10. Components Required
Rectifier power supply (Step down
transformer [1A], Diodes-4,
Capacitor-470μF)
LDR
Resistors (56KΩ,100Ω)
Transistor BC187 x 2
6V or 12V Relay
Bulb
11. Working of Automatic Street Light
Circuit
The bulb should remain OFF during daytime and turn ON
automatically during night.
The unique property of light depended resistor is utilized here. LDR is
a variable resistor which has very low resistance in the presence of
light and very high resistance in the absence of light.
In this circuit, we create a potential divider network with an ordinary
resistor in one arm and a LDR on the other arm.
According to Ohm’s law (V=IR), voltage drop across the resistor
increases when its resistance increases.
Here the drop across LDR varies with changes in light intensity. That is
voltage drop across the LDR is minimum in the presence of light and
maximum in the absence of light.
One end of the LDR is connected to the base of a BC 187 transistor. At
night, the drop is very high (> 0.6V) and it is sufficient to turn on the
transistor.
When the first transistor is ON next one will also turn ON. Thus the
relay coil energizes and the bulb will glow.
12. Advantages
1. Solar street lights are independent of the utility grid . Hence, the
operation costs are minimized.
2. Solar street lights require much less maintenance compared to
conventional street lights.
3. Since external wires are eliminated, risk of accidents is minimized.
4. This is a non polluting source of electricity
5. Separate parts of solar system can be easily carried to the remote areas
13. Disadvantages
1. Initial investment is higher compared to conventional street lights.
2. Risk of theft is higher as equipment costs are comparatively higher.
3. Snow or dust, combined with moisture can accumulate on horizontal
PV-panels and reduce or even stop energy production.
4. Rechargeable batteries will need to be replaced several times over the
lifetime of the fixtures adding to the total lifetime cost of the light.
5. The charge and discharge cycle of the battery is also very important considering
the overall cost of the project.