A solar lamp, also called a solar light or solar lantern, is a lighting system made up of an LED lamp, solar panels, a battery, a charge controller, and sometimes an inverter. The lamp uses electricity stored in batteries, which are charged by solar panels that convert sunlight into energy.

Solar-powered lights can replace other light sources, such as candles or kerosene lamps. Solar lamps cost less to operate than kerosene lamps because sunlight is free, while fuel for kerosene lamps must be bought. Also, solar lamps do not create indoor air pollution, unlike kerosene lamps. However, solar lamps usually cost more at first and depend on weather conditions to function properly.

Solar lamps used in rural areas often can provide electricity for other devices, such as charging cell phones. The cost of solar lamps has decreased in recent years because the parts used to make them are now produced in larger quantities.

History

Some solar panels use monocrystalline silicon or polycrystalline silicon. Newer solar panels use thin-film solar cells. Modern solar cells were first made in 1954 at Bell Labs. Improvements in how well solar cells convert light to electricity, along with better manufacturing methods and lower costs from producing large amounts, have led to growth in solar power use around the world.

The first patent for a solar light was filed by Maurice E. Paradise in 1955. By 2016, LED lamps used about 10% of the energy needed by incandescent lamps. Better production methods for LED lamps have led to more people using them instead of older lighting.

Components

Most solar panels are made from single crystalline silicon, a special type of material. When sunlight hits a solar cell, it creates an electric current in the connected circuit. This process is called the photoelectric effect. Photovoltaic systems change the energy from sunlight directly into electricity.

Solar panels have layers of different materials, starting with glass, then encapsulate, crystalline cells, back sheet, junction box, and finally a frame. The encapsulate prevents moisture and other harmful substances from entering, which could cause problems.

A battery is usually placed inside a metal or plastic case. Inside the case are parts called electrodes, including cathodes and anodes, where chemical reactions happen. A separator is between the cathode and anode. It stops the electrodes from reacting at the same time but allows electrical charge to move freely between them. A collector then sends the charge from the battery to outside.

Batteries in solar lamps often use gel electrolyte technology, which works well when used a lot over time. This helps the battery function in very hot or cold temperatures. These batteries may also use lead-acid, nickel metal hydride, nickel cadmium, or lithium.

This part of the lamp stores energy from the solar panel and provides power when needed at night, when there is no sunlight.

In general, the efficiency of converting sunlight into electricity is limited by physical reasons. About 24% of sunlight with long wavelengths is not absorbed. Around 33% is lost as heat to the environment, and additional losses are about 15-20%. Only 23% of sunlight is absorbed, which shows why a battery is an important part of a solar lamp.

This section manages the entire system to protect the battery’s charge. It ensures that, even in extreme weather or large temperature changes, the battery does not overcharge or over-discharge, which could damage it further.

This section also includes parts like a light controller, time controller, sound sensor, temperature compensation, lighting protection, reverse polarity protection, and AC transfer switches. These parts help important backup devices work properly during power outages.

Working principles

LED lights are used because they are very efficient at producing light and last a long time. When controlled by a DC charge controller, these lights use non-contact control to turn on automatically when it is dark and turn off during the day. Sometimes, they also work with time controllers to set specific times for the lights to turn on and off automatically.

Benefits

Solar lamps are easier to install and maintain because they do not need electricity cables. They help owners save money on maintenance and electricity bills. Solar lamps can also be used in places without an electrical grid or in remote areas that lack reliable electricity. More than 1 billion people worldwide do not have access to electric lighting, which can make it harder to escape poverty.

Solar energy depends on weather conditions and may not work as well on cloudy, rainy days, or during winter. When households switch from kerosene lamps to solar lamps, they avoid health risks caused by kerosene smoke. Kerosene can harm the lungs and cause indoor pollution, which has been linked to health problems. However, solar panels are made from silicon and other toxic materials, such as lead, which can be hard to dispose of safely.

Solar lamps help improve education for students in homes without electricity. For example, when the nonprofit Unite to Light gave solar lamps to schools in a remote area of Kwa Zulu Natal, South Africa, test scores and pass rates increased by more than 30%. The extra light allowed students to study longer after dark.

A 2017 study in areas of northern Bangladesh without electricity found that using solar lanterns reduced household spending, increased the time children spent studying at home, and improved school attendance. However, the study did not find a large improvement in students’ overall academic performance.

Uses

These lights offer a simple and affordable method to light streets at night without requiring electricity from power grids, making them useful for both people walking and drivers. Each light in a system may have its own solar panel, or a single large solar panel and battery can power several lights together.

Small solar lights are used by homeowners to create soft lighting in gardens. These lights come in different shapes and sizes, such as lights for paths and lights that focus on specific areas.

In rural India, solar lights, often called solar lanterns, are replacing kerosene lamps and other low-cost lighting options. These lights use either LEDs or CFLs and are especially helpful in areas where electricity is not easily available. They improve living conditions by providing reliable lighting.

Africa has the lowest electricity access rate globally, with only 40% of people having access to electricity. Solar lights have helped many regions in Africa by providing lighting for homes and streets. Poor lighting at night can be dangerous, but solar lights make roads and paths safer, reducing accidents.

In marine environments, LED solar lights are being used as replacements for traditional lights. Boats and sailing often take place in remote areas where power is hard to obtain, making solar lighting a practical and self-sufficient choice.

Economics

American investors are trying to create a solar lantern that costs $10 per unit to replace kerosene lamps. Solar home lighting systems can be costly to buy. Organizations that provide off-grid solar lighting use special payment plans, like the Pay-As-You-Go model, which allows people to power their homes by making small monthly payments. Today, more than 40% of all off-grid solar lighting sales in Sub-Saharan Africa are made through PayGo. In Kenya, nearly 50% of these sales use this method, and in Rwanda, about 65% of sales are done through PayGo.