Solar power is by far the Earth's most available energy source, easily capable of providing many times the total current energy demand. Covering 4% of the world's desert area with photovoltaics could supply all of the world's electricity. The Gobi Desert alone could supply almost all of the world's total energy demand. Solar power is an intermittent energy source, meaning that solar power is not available at all times, and is normally supplemented by storage or another energy source, for example with wind power and hydropower.
Sunlight can be converted directly into electricity using Photovoltaics(PV), or indirectly with concentrated solar power (CSP), which normally focuses the sun's energy to boil water which is then used to provide power, and other technologies, such as the sterling engine dishes which use a sterling cycle engine to power a generator. Photovoltaics were initially used to power small and medium-sized applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array.
The only significant problem with solar power is installation cost, although cost has been decreasing due to the learning curve. Developing countries in particular may not have the funds to build solar power plants, although small solar applications are now replacing other sources in the developing world.