Solar energy has the potential to be the ultimate source of powersolar energy produces less than 1% of the power used for generating electricity in the world today. for all of civilization for all of humankind's foreseeable future. It is clean. abundant, and free. Yet
One of the reasons for the relatively small significance of solar energy in the power market is the intermittent nature of sunlight. Solar energy is not directly available at night and drops significantly during cloudy conditions. The electric grid, however, needs consistent and reliable sources of electricity to meet the needs of a complex, demanding civilization. Solar energy can be made more reliable by various supplementary methods and by coupling it with other, backup sources of power, but the task of providing a continuous flow of electricity strictly from solar sources is not yet complete. The details of this problem are discussed in the Reliability challenge.
Another problem in providing solar power in the USA is the lack of a completed electric grid, particularly in the relatively remote areas of the country where the most intense, most consistent solar radiation occurs. These areas include, in the case of the USA, several states in the Southwest. Even if large solar farms were built in these locations and massive amounts of electricity were generated, there is presently not a sufficient portion of the national electric grid extending into those locations to gather and feed that electricity to the locations across the country where it could be used. The details of this problem are described in the Grid Connection challenge.