The enormous potential power in solar energy is revealed by measurements which show that solar heat reaches the earth in the Temperate Zone at the average rate of about 4,000,000 calories per square yard per day. During the three months of greatest sunshine, an acre of land receives directly from the sun an amount of heat equivalent to burning approximately 250 tons of high-grade coal. This measurement indicates that unobstructed solar radiation, transformed completely into useful energy, would produce approximately one horsepower per square yard.
This energy determines our climates, causes winds, ocean currents, and rainfall, and produces photochemical reactions whereby a portion of the energy is stored in plants. Thus, solar energy is the ultimate source of our fuels—wood, coal, oil, and gas—as well as of power derived from wind or falling water. However, the stores of fuel energy in coal, oil, and gas, while great, are not inexhaustible. It is therefore of ultimate importance to investigate and develop alternative sources of heating and power.To read the original article: Untapped Potential | MIT Technology Review
