Solar energy is energy that is generated by the sun and is also referred to as solar power. The heat and light generated by the sun warms the earth and sustains all plant and animal life (1). Every hour the energy beamed on to earth by the sun is more than enough to satisfy global energy needs for a year (2). This energy travels through space from the sun in waves of electromagnetic radiation such as gamma rays, ultraviolet rays and infra-red rays. Earth is protected from the full force of these solar rays by the atmosphere (3). The rays that do make it through are more than enough to provide for all of humanity’s energy needs (4). These rays can be harnessed as free energy by using one of the three main types of solar energy systems; passive, active and photovoltaic.
Passive systems do not use any external energy source to function. Clever design takes advantage of local climates to heat structures during winter and reflect heat in summer (5). This can be achieved by using double-glazed, south-facing glass windows to collect energy and a rooms interior mass to store it (6). The ancient Greek and early Chinese used passive systems in their architecture (7).
Active systems use additional electric or mechanical devices to power a fan or pump which actively converts solar energy into other useable forms of energy such as heat or electricity (8). This type of system is commonly used to heat water, over 90% of homes in Israel and Cyprus use solar powered domestic hot-water systems (9).
Photovoltaic cells, commonly called solar cells, are non-mechanical devices that convert sunlight directly into electricity (10). Solar panels are created using multiple solar cells. These panels can be used to provide electricity, hot water and heat to homes and businesses. On a smaller scale solar cells can power wristwatches and calculators (11). Large scale installations such as Solar Star in California supply 255,000 homes with power (12). Photovoltaic cells are commonly used with active systems.