Solar Lighting – An Off-Grid Lighting Solution
Solar lighting is an off-grid lighting solution that can save energy, reduce electricity rates and help combat rising global energy prices. It is also a great option for remote areas that don’t have access to centralized power infrastructure.
A solar light consists of a light fixture, solar panels, batteries and a charge controller. All these components must work together to ensure optimal energy harvesting, battery usage and compliance.
Solar Panels
You’ve seen solar panels before – they’re on the roofs of Google, Apple, and other corporations. And they’re also in calculators and many other products. Solar panels (or photovoltaic cells) absorb sunlight during daylight hours and generate direct current electricity. Those electrons flow through a circuit to power devices and provide energy for your home.
A solar panel has semiconductor layers of different materials that SOLAR LIGHTING energise when hit by photons from the sun. Each layer has specific electronic properties that energise when hit – it’s called the photoelectric effect.
When sunlight hits a solar cell, its energy breaks apart electron-hole pairs within the semiconductor. The free electrons are sent to the positive side of the cell, and the holes to the negative. Conductors attached to each cell then create an electric field, which causes electrons to flow through the circuit and produce electricity. Multiple solar cells are wired together and grouped into modules, which can then be grouped into larger systems called solar arrays.
Most residential solar panel systems are made of crystalline silicon, which has the best efficiency and power production. But there are other options too. Thin-film panels use amorphous silicon or cadmium-telluride, and are manufactured by spraying or depositing the material in thin layers on a glass surface. These panels are less efficient, but they’re easier and cheaper to manufacture.
Batteries
The batteries in solar lighting systems store the energy produced by the solar panels so that the lights can operate at night and during times of low sunlight. Without batteries, solar lights would not be able to work at all. Batteries vary in size and type depending on the system’s needs. For example, larger batteries will have a longer power capacity and can be better suited to areas with extreme weather conditions or long periods of cloud cover.
Most modern solar lighting systems use rechargeable nickel cadmium batteries that are similar in size to AA batteries. During the day, solar cells convert sunlight to charge the batteries. When the sun goes down, photoreceptors in the lights sense the absence of sunlight and start supplying electricity to the LED. This process shuts off automatically at daybreak.
Some solar lights require a separate battery controller, while others have this circuity built into the solar panel itself. A charge controller helps regulate the energy flow around the battery to prevent overcharging and over-discharging. It also sends signals to the light fixture to turn it on and off as needed.
Charge Controller
A solar charge controller is an important piece of equipment in any small to medium solar lighting system. It connects directly between the battery and solar panel, and regulates the amount of current flowing into the battery and out to the load. It also controls the charging process, and displays information about your solar system and battery.
Without a solar charge controller, a solar panel would overcharge a battery by producing too much voltage to be processed. This could damage the battery or even explode it! Charge controllers prevent this by regulating the amount of current flowing from the solar panels to the battery and stopping any backflow of electricity at night.
Simple PWM (Pulse Width Modulation) solar charge controllers connect directly between the battery and the solar panels. They use a basic rapid switch that opens and closes rapidly to modulate the battery charging current. This outdoor solar lights for house pulls the solar panel voltage down away from its optimum operating voltage (Vmp) to match the battery charge (absorption) voltage, which significantly reduces the power output of the panels.
MPPT solar charge controllers, on the other hand, take advantage of the varying amounts of sunlight (irradiance) that hits the solar panel throughout the day and convert the solar array voltage to the optimum combination of voltage and current for maximum power generation. This increases the solar energy available to your battery bank by up to 30% compared with simple PWM controllers.
Light Fixture
Solar lights can be placed to highlight attractive garden features like flower beds, trees or sculptures. Strings of solar lights can add a festive touch to patios or porches and are also effective at lighting walkways, driveways and steps for improved safety. They can be used to illuminate water elements such as pools or fountains and even to light up decorative features like fire pits, bird baths and urns. Some models use a realistic flickering “flame” to mimic the look of real candles or torches and provide a safer alternative.
Because solar lights depend on sunlight to function, they may not be suitable for dark or shaded areas. They can also be affected by cloudy or rainy days, when they won’t receive enough sun to charge.
The solar panels on the lamp capture photons from the sun and knock loose electrons in a special band gap within the panel, creating an electrical charge that moves through the circuitry and into the battery. The battery converts and stores the chemical energy as DC power until needed, at which time it powers the LED bulb to emit light. It’s a self-contained, carbon-free electricity source that eliminates the need to connect to a power grid, making it ideal for locations and purposes where conventional utility electricity isn’t available or practical.
