Insolation variation in March in Daggett, Calif. (top), and areas where insolation exceeds that of Daggett, Calif. (bottom). Click image to enlarge.
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Today, the per capita energy use ranges from1,000 kWh/yr in Africa to 16,000 kWh/yr in Canada. Therefore, if the collection and conversion system is assumed to be 10% efficient, and the solar energy is collected in a high insolation region, the per capita collector area required to meet the total energy needs of the globe would range from 2.5 m2 for people living in Africa to 40 m2 in Canada.
On the same basis, the collector area required to meet today’s total energy use of mankind can be estimated to be about 3% to 5% of the area of the Sahara. Assuming that the yearly solar energy collected by each square meter of collector area is 3,000 kWh, knowing that a square kilometer (km2) is a million square meters, and that each kWh equals 3413 BTUs, the collector area needed to collect each Q is 100 km.
Land occupies 150 million km2, the oceans occupy 361 km2. Therefore the Sahara covers 1.6% of the total surface area of the globe. Including the oceans, the total high insolation area on the planet is more than 25 times that of the Sahara. Therefore to collect the global energy use today, 40,000 km2 needs to be covered. Because the Sahara’s area is 9 million km2, 4.44% of its area would need to be covered.
Naturally the total area of high insolation on earth is much larger than that of the Sahara, and solar energy can be collected not only on solid ground, but also on floating islands in the oceans.
Next time, I will discuss the methods available to convert this solar energy to electricity.