A Minute of Sun Delivers A Year of Energy
One horsepower is what it takes to lift 550 lbs one foot in a second (550 ft lbs per second or 33,000 ft lbs per minute). So horsepower is a way we measure an amount of work done in a specific period of time.
Some scientist recently calculated that the sun delivers continuously to Earth the equivalent of 30,000 horsepower per inhabitant. So, if we could harness our own share of the sun's power, we each could lift 500 tons straight up at 11 miles per hour. Or 50 tons at 110 miles per hour! Obviously, no single individual could ever use all "his or her share" of this power.
Since one horsepower is about three quarters of a kilowatt, 30,000 horsepower is about 23,000 KW. Roughly speaking, using 10 cents as the price of a kilowatt-hour, our "share" of the sun's power has an economic value of $2300 an hour, or $20 million a year.
Looked at still another way, one minute of the sun's energy hitting Earth is enough to provide all our current energy needs for an entire year.
Or still another way, a ten-by-ten mile square of the desert in the Southwest could generate all the electricity needs of this country, using current technology (and leaving aside transmitting it to where it is needed).
So, the sun is truly a bountiful, and a completely non-polluting, energy source, and our challenge is to find good ways to harness it.
Worth noting, as well, is that all our current sources of energy (except nuclear and geothermal) are various forms of solar energy. Fossil fuels are hydrocarbons, chemically transformed over the ages, from carbohydrates photosynthesized by the sun. Wind is solar generated. Hydroelectric power derives from water lifted by the sun and deposited as rain or snow. So, our quest to "mine" solar energy in new ways is part of a continuum starting when Man built his first fire.
Man has captured solar energy in small ways for a long time. It started with facing windows to the South to warm a building, or exposing blackened pipes and containers to direct sunlight to heat water for washing up. Then solar collectors, with mirrors to focus more of the sun's energy on the target, were developed. Now, highly sophisticated arrays of mirrors collect and focus enough energy to turn water into high temperature vapor and drive turbines that generate industrial quantities of electricity. These units are getting cheaper all the time, but both in terms of capital and operating costs, they cannot yet compete with pulverized coal-fired electric plants, unless the imputed costs of CO2 emissions are included. More on costs later.