Outdoor lighting presents a unique set of problems and opportunities. One problem is power. While most everything in technology gets cheaper over time, running AC power lines to hundreds of outdoor lights is just as expensive and troublesome as ever, and no relief appears to be in sight. The light itself only needs to operate when the sun isn’t shining, presenting outdoor lighting designers with the opportunity to capture the sun’s energy when it’s available for use.
What is needed to complete the picture are solar arrays and rechargeable batteries to capture the sun’s energy while it shines, and then a microcontroller to dole out the battery’s stored energy to the LED lamp at night.
In summer, we can see that at a given latitude and for a given system, the energy generated by the solar cell and stored by the rechargeable battery will exceed what the LED lamp needs to provide adequate illumination. In winter, when the days are shorter and the sunlight weaker, less energy can be harvested and there will be more hours of darkness, so the availability of energy and the need for it will be more closely balanced.
Why LEDs?
For outdoor lighting, LEDs offer unique advantages. They are far more rugged than incandescent lamps or fluorescents, and need no complex and expensive electrical ballast systems as fluorescents do. They produce much more light per watt than incandescent lights can, and LEDs last longer than either of the other types.
While it can be argued that fluorescents produce more light per watt than LEDs do, because of the radiation pattern of fluorescents, much of that light will be radiated in the wrong direction, useless without the inclusion of heavy, expensive reflectors. The patterns achievable for LEDs are much more appropriate to the task at hand.
A Boon for the Third World
While these types of systems are highly useful in advanced countries, they can be absolute game changers for less-developed areas where the electric grid is both less accesible and less reliable. Because many of the effected regions lie close to the equator, they enjoy more intense sunlight than is incident in more northerly latitudes, which translates into more solar power, and more electrical power to provide more light.
The Phillips Corporation is engaged in larger scale projects to provide solar-based LED lighting for areas of up to 1,000 square meters. By the end of 2015, they will have established 140 of what they are calling “Community Light Centers” to enable community life to go on long after the early African sunset. For more temporary solutions, the company’s SPL1560 is a portable, easy to set up system that low-skilled individuals can deploy to provide 100 square meters of light anywhere it’s needed.
Solar powered lighting can be employed as a money-saving convenience in the Western World, and it can melt through an otherwise insurmountable cloud of darkness in less affluent settings. As better and better batteries are developed and deployed, the future will only become brighter.