|A Power Authority rooftop solar system, one of the world's largest, atop the Gun Hill Road Bus Depot.|
First developed in the mid-1950s, photovoltaic cells have become popular for a wide variety of applications where no other electricity source is available. In developing countries, they're used for water pumping and irrigation, communications and village power. Other uses include marine navigation signals and security lighting in remote areas.
The worldwide market for photovoltaic systems has increased by 15 to 20 percent a year in the last decade, as their cost has become more competitive with traditional, grid-connected electricity supplies. The data on photovoltaics we're compiling today will help expand the use of this technology tomorrow.
Photovoltaic systems convert sunlight directly into electricity, using panels made of wafers or thin films of semiconductor materials such as silicon. These systems are totally non-polluting and silent, have no moving parts and are highly reliable. Since they consume no fuel and are nearly maintenance-free, their operating costs are negligible.
In addition, they produce the greatest amount of power on long, hot summer days, when demand and the cost of power are highest. Besides offering energy-efficiency and environmental advantages, solar electric systems help local economies by creating jobs as development and manufacturing opportunities increase.