The total solar energy absorbed by the Earths’ surface is approximately 3,850,000 exajoules (EJ) per year. This is more energy in one hour than the world uses in one year. Solar power is the conversion of sunlight into electricity. This can be done either directly using photovoltaics, or solar cells, which convert light into an electric current using the photoelectric effect. The total installed photovoltaic capacity has multiplied by a factor of 100 in 14 years, reaching 178GW in 2014.
The foremost advantage of solar power is that, once installed, is that no greenhouse gases are released. Also, using the energy of the sun is free, but solar energy is an intermittent energy source, as it is not available at night or on cloudy days. This makes energy storage an important issue in order to provide the continuous availability of energy. Thus, all available output must be taken and either stored for when it can be used, or transported to where it can be used. Currently, this is very costly. Another disadvantage, though minor, is the visual impact of solar farms.
Solar power is the least efficient of all forms of renewable energy, ranging from 4-22% efficiency of electricity generation. However, as the technology progresses, this is likely to improve. The capital costs of installing a solar plant are also very high, and solar photovoltaic generation is one of the most expensive forms of power, at $0.13/kWh as of 2015. Although, it is assumed that this price will fall over time.