Solar street lights are an effective outdoor lighting to illuminate the streets or any open areas through the use of solar energy. The history of street lights goes back to Greek and Roman civilizations where light primarily served the purpose of safety and security.

Oil lamps, candle lighting and gas lamp lighting were used for public street lighting before the invention of incandescent lights. Renewable energy comes from natural resources that are constantly replenished. In 1839, Alexandre Edmond Becquerel discovered the photovoltaic effect which explains how solar energy is converted into electrical energy.

Solar energy has been harnessed by humans for thousands of years and has developed over the years.

Solar street light is powered by solar panels and turned on and off automatically by sensing the nightfall and the daylight. Solar (photovoltaic) cells generate direct current by using sunlight as a source of energy. The controller in solar lights works as a regulator. It charges the battery and also controls the reverse power flow.

Batteries store the solar energy during the day to power the lights at night. With the advancement of technology, there are different types of solar street lights available in the market.

Solar street lights are the perfect cost-effective solution not only for the urban population but also for the people living in rural areas that are deprived of electricity.

Solar street lights have components such as 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 solar 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 solar 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.