Anyway, with rising petroleum costs, (please note the sharp drop in gas prices which corresponded to a drop in the price of crude oil when the United States declined to elect another hawkish president in November 2008. The war drums are being beaten again over Iran, and look! Crude oil just peaked at $114 / barrel), it gets one thinking about what it would take to completely get off natural gas and depend only on solar power.
This is going to be a bit more complicated than some of the previous ones, so I'm going to do this in parts. In this one, I'm going to tackle how much solar energy reaches the Earth.
Okay, we'll start with finding out how much energy the sun emits.
Solar luminosity (the amount of energy emitted by the sun) is about 3.8e26 Watts.
If the Earth is, on average, 1.5e11 meters (one astronomical unit) from the sun, we can use the equation for the surface area of a sphere to find out how much area that energy spreads out at our radius from the sun:
A = 4 * π * r²
= 4 * (3.14) * (1.5e11 m)²
A = 2.8e23 m²
Now for how much of that the Earth takes up. The diameter of Earth is, on average (Earth is not a perfect sphere, but we'll cheat and say that it is) 12,742 km. So the radius would then be about 6,371,000 m, and with the equation for area of a circle (A = π*r²), the area it would present to the sun would be about 1.3e14m². Divide the two areas and you get that Earth gets about
Amount of solar energy that reaches Earth:
Cross-sectional area of Earth
Energy of the Sun * --------------------------------
Area of Earth's Orbital Sphere
1.3e14 m²
(3.8e26 W) * ----------- ≈ 1.8e17 W
2.8e23 m²So the Earth receives about 1.8e17 W of heat from Earth.
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