Solar lights are a very common and highly versatile solution for providing free outdoor lighting, particularly during summer and lighter parts of the year, but also potentially throughout the winter. They are typically low-cost, require virtually zero maintenance and are free to operate.
In addition, they provide attractive aesthetic benefits as well as serving highly functional purposes, doing so at performance levels that come near to rivalling traditional filament lighting. In a nutshell, they are both decorative and provide valuable safety and security benefits.
What Are Solar Lights?
Solar lights are lights made for outdoor use and powered by solar energy during daylight hours, for use during nighttime. Because they are solar powered, they operate independently of the electricity wiring for the home or building where they are used.
How Do Solar Lights Work?
Solar lights consist of five components:
- A small solar panel
- A rechargeable battery
- A group of LED lights
- A light sensor
- An on-off switch
The Solar Panel
The small solar panel contains a number of photovoltaic (PV) cells. These cells – like all photovoltaic/ PV cells – contain light-sensitive materials that convert sunlight into small amounts of electrical current. The sunlight does not necessarily have to be direct, or at least, it does not need to be direct all the time, but direct sunlight is by far best for optimum results.
The Rechargeable Battery
This resulting electrical current is sent to the rechargeable battery, normally a nickel–metal hydride battery (abbreviated NiMH), which are better suited than normal NiCad batteries for repeated rechargeable operations. The battery stores the electricity generated by the solar panel for later use, during night time.
The general guidance is that these batteries can be expected to last two years (approximately 600 charging cycles). For this reason, it is essential to ensure that solar lights have removable batteries (the cheapest models may not).
Light-emitting diode (LED) lights are highly efficient miniature lightbulbs that are far more efficient than traditional filament bulbs, and last much longer (typically up to 10,000 hours, compared to the typical 3,000 life of filament bulbs). These qualities, plus their bright light makes them particularly well suited for outdoor solar lights for nighttime use.
The light sensor incorporated with a solar light is technically known as a photo resistor. This sensor switches on the solar light when daylight fades to darkness, and switches off the solar light when daylight returns. In addition, this part of the solar light typically incorporates a sensor known as a charge controller, which ensures that the rechargeable batteries do not exceed their maximum safe charging levels in cases of prolonged or exceptionally strong sunlight.
Given the presence of the light sensor, it may not seem obvious why an on-off switch would be useful. The reason is that there may be times when it is desirable to keep the lights switched off, for example, to preserve battery power (and let it fully recharge before using again).
Advantages and Limitations of Solar Lights
- Operate on clean, natural energy, with no external electricity used
- Virtually no maintenance required (apart from battery replacement approximately every two years), so in combination with no electricity costs, solar lights operate at zero cost
- Can be very inexpensive to purchase (depending on specifications)
- Year-round operation (performance will depend on specifications)
- Safe for use in rain and snow
- Dependent on plentiful direct sunlight (as with all solar energy generation)
- Will not match the performance of the best lights connected to the electricity grid
- Depending on the specifications, may not be able to provide light throughout the full hours of darkness during winter
Typical Uses for Solar Lights
Solar lights can be used in a variety of ways, limited only by imagination and personal preference. Uses broadly fit into two these categories:
- Safety and security
Decorative Solar Lights
Very often, solar lights are used as decorative features in outdoor gardens and around lawns, either on a permanent basis, or for special functions (family gatherings etc.).
Solar Lights for Safety and Security
Most solar lights are used to light pathways, so inherently provide a safety function, even if they are also seen as decorative. In addition, solar lights can be mounted overhead and used to light particular areas for safe nighttime passage. And solar lights are also a viable solution for home and building security lighting.
Other Considerations for Solar Lights
Number of LEDs
More LEDs does not necessarily mean better. For one thing, the more LEDs in a given solar light, the faster it will consume electricity. A more useful approach is to ‘right size’ solar lights for where they will be used, taking into account the required area of coverage and hours of operation. A knowledgeable solar light reseller can advise, based on specific requirements.
Solar Lights in Poor Weather
Because solar lights are designed for outdoor use, they are perfectly safe to use in rainy and even snowy conditions.
Solar Lights Designed for Winter Use
There are premium solar lights that are designed to work in lower daylight conditions. Although more costly than typical solar lights, this winter variety will deliver far superior performance under conditions where days are short, nights are long and sunlight is in lower supply.
Using Solar Lights in Daytime
In general, solar lights will not operate during daytime, because the light sensor will not activate the LED’s. Even if that were not the case, this would rarely if ever serve a useful purpose – hence this design limitation (if it can be referred to as such).
Using Solar Lights Indoors
In theory, solar lights can work indoors, as long as they are being charged by sunlight that can reach them during daylight. This assumes, of course, that the room in question does not already have traditional lighting in place that may be a better solution.
Solar Light Safety
Since solar lights use LED’s, they run at far cooler temperatures than traditional filament lights. Therefore, they are far safer in environments where there are children and pets.
Key references for this article:
- How Do Solar Lights Work? – festive-lights.com
- The Real Truth About Solar Lights – lights4fun.co.uk
- Solar Light FAQ’s – festive-lights.com
Georg Kogler is the Managing Director of GK Electrics GmbH based in Liebenfels, Carinthia, Austria. GK-Electrics is a company specializing in the development and installation of individual photovoltaic solutions. GK-Electrics focuses on the design and implementation of individual photovoltaic systems for industry, trade and private households.
- Glühbirne: Sergey Nivens | Shutterstock.com