What is Solar Energy

Solar power is the technology of obtaining usable energy from the light of the Sun. Solar energy has been used in many traditional technologies for centuries and has come into widespread use where other power supplies are absent, such as in remote locations and in space.

Photovoltaics, or PV for short, is a solar power technology that uses solar cells or solar photovoltaic arrays to convert energy from the sun into electricity. Photovoltaics is also the field of study relating to this technology.

Solar cells produce direct current electricity from the sun’s rays, which can be used to power equipment or to recharge a battery. Many pocket calculators incorporate a solar cell.

When more power is required than a single cell can deliver, cells are generally grouped together to form “PV modules” that may in turn be arranged in “solar arrays” which are sometimes ambiguously referred to as solar panels. Such solar arrays have been used to power orbiting satellites and other spacecraft and in remote areas as a source of power for applications such as roadside emergency telephones, remote sensing, and cathodic protection of pipelines. The continual decline of manufacturing costs (dropping at 3 to 5% a year in recent years) is expanding the range of cost-effective uses including roadsigns, home power generation and even grid-connected electricity generation.

Large-scale incentive programs, offering financial incentives like the ability to sell excess electricity back to the public grid ("feed-in"), have greatly accelerated the pace of solar PV installations in Spain, Germany, Japan, the United States, Australia, South Korea, Italy, Greece, France, China and other countries.

PV in Buildings

Solar arrays are increasingly incorporated into new domestic and industrial buildings as a principal or ancillary source of electrical power. Typically, an array is incorporated into the roof or walls of a building, roof tiles can now even be purchased with an integrated PV cell. Arrays can also be retrofitted into existing buildings; in this case they are usually fitted on top of the existing roof structure. Alternatively, an array can be located separately from the building but connected by cable to supply power for the building.

Where a building is at a considerable distance from the public electricity supply (or grid) - in remote or mountainous areas – PV may be the only possibility for generating electricity, or PV may be used together with wind and/or hydroelectric power. In such off-grid circumstances batteries are usually used to store the electric power. However, the largest installations are grid-connected systems (see table below). These systems are connected to the utility grid through a direct current to alternating current (DC-AC) inverter. When the load required in the building is more than that supplied by the PV array then electricity will be drawn from the grid; conversely when the PV array is generating more power than is needed in the building then electricity will be exported to the grid. Batteries are not required and standard AC electrical equipment may be used.*