Using a range of constantly evolving technologies, solar energy, radiant light and heat from the sun have been harnessed by humans since ancient times. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass account for most of the available renewable energy in the world. The earth receives more energy from the sun in just one hour than it uses in a whole year. Only a minuscule fraction of the available solar energy is used. Solar-powered electrical generation relies on heat engines and photovoltaics.
Solar technologies are broadly characterised as either passive or active depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building towards the sun, selecting materials with favourable thermal mass or light-dispersing properties and designing spaces that naturally circulate air. Solar energy can be produced on a distributed basis, with equipment located on rooftops or on ground-mounted fixtures close to where the energy is used. Large-scale PV or concentrating solar power systems can also produce energy at a central power plant.
During the last couple of years, the price of solar cells has dived and deployment has increased significantly. While most PV solar parks are still built based on subsidised prices, solar PV power will become available to an increasing number of regions at grid parity pricing over the next few years.
Due to the rapidly diminishing margins in the industry, a number of producers are struggling. However, major strategy consultants believe that solar cell production is sustainable at higher volumes and that after a period of consolidation, surviving manufacturers will have access to an ever larger market, thus putting solar power in a better position in the future global energy mix. McKinsey expects this «non-subsidised demand» to represent 4-600 GW of solar PV over the next eight years, and grow even faster over the subsequent decades as the competitiveness of PV is further improved.
As of 2010, solar photovoltaics generates electricity in more than 100 countries and, while comprising a tiny fraction of the 4,800 GW total global power-generating capacity from all sources, it is the fastest growing power-generation technology in the world. Between 2004 and 2009, grid-connected PV capacity increased at an annual average rate of 60 per cent, to some 21 GW.