Solar Street Lights

 What are Solar Street Lights?

Solar Street Lights are a prevalent and innovative solution for illuminating public spaces sustainably and cost-effectively. Solar streetlights have photovoltaic cells responsible for converting the sunlight’s radiation into electricity. The device’s semiconductor materials facilitate the transformation of solar energy into electricity. This energy conversion process is known as the “photovoltaic effect.” 

Solar LED lights need sunlight to work, but they do not necessarily need direct sunlight. These lights can still get charged and work on cloudy days or in areas with partial shade. The solar panel will still collect energy from the sun even if it is not exposed directly. Even artificial lights can charge solar panels. 

The French scientist Edmond Becquerel recognized that solar thermal energy could be captured to generate electricity in 1839. His French compatriot Augustin Mouchot created the first solar- powered generators in the 1860s. These rudimentary generators put out enough energy to power small bulbs but weren’t solar lights as we know them today. 

American inventor Charles Fritts, in 1883, takes credit for creating the first solid solar cell, so he is perhaps the most obvious answer to ‘who invented solar lights.’ This first solar cell only had around 1% electrical efficiency; the best solar panels today can have over 20%. 

These Lights are highly energy-efficient. They utilize LEDs, known for their low energy consumption and long lifespan. LEDs transform a high percentage of electrical energy into light, minimizing wasted energy and maximizing illumination. 

One of the most significant environmental benefits of solar lights is their ability to reduce carbon emissions. Unlike grid-powered lights that rely on electricity generated from fossil fuels, These street lights harness clean and renewable energy from the sun. Rain will not damage the solar lights as they’re made to withstand rain and other weather changes. 

These Street Lights have components such as an SPV Module, charge controller unit, battery, luminary, interconnecting cables and pole. 

• Solar photovoltaic (SPV) module: is fixed on top of the pole with suitable inclination to receive maximum sunlight throughout the day. The SPV module produces suitable voltage and current, which is used to charge the battery. During the night, the lamp which is housed inside the luminary lights up by using the energy stored in the battery.
• Charge controller unit (CCU): controls the charging. Charge controller unit increases the battery life by not allowing the battery to deep discharge and overcharge. During deep discharge conditions, the CCU turns off the light, so as to stop further discharge of battery.  During overcharge conditions, CCU disconnects the solar module and prevents overcharging of the battery.
• Battery:  The energy that is generated by SPV module is stored in the battery.  This energy is used to light up the luminary during night time.  For these street lights, LiFePO4 battery is normally used, which is more compact than the battery box style fixture of traditional street light which houses Tubular Lead Acid batteries. Lithium ion battery used in these type street lights, is housed inside the luminary itself.
• Luminary:  LED lamp or fluorescent (CFL) lamp is used to provide illumination.  CCU and the battery are incorporated in the luminary itself if the battery used is lithium-ion battery.  If the battery is lead acid, only the CCU is incorporated in the luminary.  
• Interconnecting cables:  Cables are used to connect the SPV module, luminary, CCU and battery.
• Pole:  MS street light pole or GI pole is used to mount the SPV module and the luminary at a height of 4-5 meters above ground.

Solar Street Light Price in India

The product range is from 15 watts to 120 watts, and the price range is Rs. 3,999 to Rs. 32,999, including all expenses; the price mentioned is for light and accessories without poles.

You can find below the price list of a Semi Integrated Solar Street Light.

You can find below the price list of a All In One Solar Street Light.

Types of Solar Street Lights.

In India, there are three types of street lights available:

1. All in One Solar Street Light - This light is compact where all the components are housed inside a single unit.

2. Semi Integrated Solar Street Light - In this, battery, fixtures, luminary and controller are molded into a single unit and the solar panel comes as a separate unit.

Features of Solar Street Light

• Automatic:  By sensing outdoor light, most of these lights turn on and off automatically and are designed to work throughout the night with a dusk to dawn sensor feature.
• Motion sensor: With motion sensor these lights can detects motion and changes the intensity of the light. This feature helps the lights act as security lights. It also extends battery life by reducing the brightness when no motion is detected and giving 100% brightness when movement is observed.
• Timer based: To save the battery, the controller can be set to dim the lights if required.
• Energy saving and pollution reducing: Since solar lighting uses solar energy, no non-renewable energy is consumed, making it environment friendly. The biggest advantage of these lights is that they will continue to light up the area even during a power outage.
• Money saving: With no need to pay ongoing electricity charges, solar lighting will save money in the long term.
• No cable work:  No interdependency weakness, No need of foundation work of cables or electric equipment is necessary.  No need of any complicated power facilities; hence, saving both cost and labor.
• Easy maintenance:  Built-in intelligence and requires no manual operation after installation, thus making it safe and economical.
• Weatherproof:  IP65 rating waterproofing is used for the lights to withstand harsh climate changes.

Types of battery used in Solar Street Light

There are mainly three types of batteries used: lead-acid batteries, lithium-ion (Li-ion) batteries, and lithium ion phosphate (LiFePO4), the latest addition to lithium battery technology.

LiFePO4 recharges at a faster rate and offers at least 4 to 5 times the number of charge cycles than lithium-ion batteries, They have a life span 10 times longer than a traditional lead acid battery and are also lighter in weight. LiFePO4 batteries provide upper and lower voltage protection and are priced on the higher side comparatively. Lead acid batteries have large current capability and are inexpensive but demands regular maintenance with a shorter lifespan. Although lithium-ion batteries are considered to be expensive, they offer a longer life span and are almost maintenance free.

Types of light source used in Solar Street Light

LED, CFL and sodium vapor lights are used.  LED offers higher luminosity and lower energy consumption; hence they are used most commonly in these type of lights.  CFL uses low pressure mercury vapor gas and the power consumption is more compared to LED lights. Sodium vapor lamps are gas-discharge lights and considered high efficient lights but offers only monochromatic color and also produces more heat than LED Technology.

Types of lighting fixture used in Solar Street Light

Cobra head style fixtures are the most commonly used fixture. Now with advancing LED technology, there are many decorative, lighter in weight and less bulkier fixtures available.   For durability, the housing used for lighting fixture is ABS plastic or aluminum.

Types of controller used in Solar Street Light

PWM or MPPT controller is used in these street lights.  With a pulse width monitor (PWM) controller, the panel voltage drops to match the battery voltage, more battery reserve capacity, longer battery life, etc.   With maximum power point tracking (MPPT) controller, the solar panel can operate at its maximum power point and generate more power. MPPT controllers are regarded as expensive compared to PWM controllers because of their ability to produce more power with the same number of solar modules than a PWM controller.

Types of solar panel used in Solar Street Light

Solar LED street lights either have a mono-crystalline solar panel or a polycrystalline solar panel.  Mono-crystalline solar panels are made of pure silicon cells that generate higher efficiency.  Poly-crystalline solar panel is the traditional solar panel which is commonly used and less expensive.

Working principle

Solar lights function based on the simple principle of photovoltaic effect.  During the day, the photovoltaic cells (solar cells) in solar panels convert the solar energy into electrical energy.  This energy is stored in the battery.  The controller helps in charging the battery and regulating the voltage.  At night, the solar lamp draws the current from the battery and starts to illuminate the light source from dusk to dawn.

MNRE standards in Solar Street Lights

According to The Ministry of New and Renewable Energy, there are four models of White-LED (W-LED) based Solar Street Lighting Systems.

Model-I

• Lead acid battery is used.
• The street light operates from dusk to dawn at full brightness.
• PV module: Crystalline silicon solar cells, output of 40 Wp under Standard Test Condition, certificate of testing conforming to IEC 61215 Edition II/ BIS 14286 from an NABL or IECQ accredited Laboratory.
• Battery: Lead acid tubular flooded or tubular GEL/VRLA, 12V – 40 AH @ C/10
• Light source: White light emitting diode, 7 watt
• Electronic efficiency: Minimum 85% total.

Model-II

• Lead acid battery is used.
• The street light operates from dusk to dawn, the first four hours at full brightness and then at a lower level; with the help of motion sensor, light glows to full brightness only in case of movement and then dims down automatically after some time.
• PV module: Crystalline silicon solar cells, output of 30 Wp under Standard Test Condition, certificate of testing conforming to IEC 61215 Edition II / BIS 14286 from an NABL or IECQ accredited Laboratory.
• Battery:  Lead acid tubular flooded or tubular GEL/VRLA, 12V – 20 AH @ C/20
• Light source: White light emitting diode, 7 watt
• Electronic efficiency: Minimum 85% total.

Model-III

• Lithium Ferro phosphate battery is used.
• The street light operates from dusk to dawn at full brightness.
• PV module: Crystalline silicon solar cells, output of 40 Wp under Standard Test Condition, certificate of testing conforming to IEC 61215 Edition II / BIS 14286 from an NABL or IECQ accredited Laboratory.
• Battery: Minimum 160 Wh Lithium Ferro phosphate battery
• Light source: White light emitting diode, 7 watt
• Electronic efficiency: Minimum 85% total.

Model-IV

• Lithium Ferro phosphate battery is used.
• The street light operates from dusk to dawn, the first four hours at full brightness and rest of the time, at a lower level; in case of movement, the light gives out full brightness and then comes back to lower level automatically.
• PV module: Crystalline silicon solar cells, output of 30 Wp under Standard Test Condition, certificate of testing conforming to IEC 61215 Edition II / BIS 14286 from an NABL or IECQ accredited Laboratory.
• Light source:  White light emitting diode, 7 watt
• Electronic efficiency: Minimum 90% total.

Also, there are technical specifications provided by MNRE for quality, warranty, operation and maintenance.

How to install Solar Street Lights

Appropriate safety guidelines should be followed during installation.  The ground chosen should be flat without any inclination.  The basic tools used for installing the lights are wrench, hoisting mechanism (pulling the pole upright with a crane or using manual assistance depending on the weight of the pole), screwdrivers, spanner and Allen key.  A complete street light kit comes with solar panel, light fixture, lamp pole, battery and controller.  The LED light and the solar panel can be secured to the pole when the pole is still on the ground.  The installation position must create a suitable angle for the solar panel to be faced in the right direction to get maximum sunlight.  The pole used must be strong as there are components mounted on top of the pole and wind resistance is also a factor.  The lights should be secured to the ground as per the instructions given by the manufacturer.  It is important to install the light in a shadow free area where direct sunlight is available throughout the day.

Maintenance of Solar Street Lights

Although maintenance is very low, the solar panels should be cleaned off dust particles.  The cleaner the panel the better the efficiency will be.  Clean solar panels guarantee longevity of the panels.  Check the wires on a regular basis to look for chewed wires and conduit.  Also, inspect the fixture for any problems from vandalism, weather or wildlife.  Solar panels are designed with a tilt to avoid water stagnation during rain.  IP65 waterproofing is used to withstand tough climatic conditions.  The solar panels should be out of shade to provide maximum brightness.  Trim down the tree branches, if any, covering the light.  The solar panel can be cleaned using a soft bristled brush or cloth with mild shampoo or detergent. You can also hose off the panels to wash off any dirt or dust.  Ensure not to scratch the glass during cleaning.

Solar Street Lights – FAQ

It is only rational to have a lot of queries before switching to solar energy. Here we are listing out answers to the most commonly asked questions.