Something for nothing

[Jehanne]

Please correct me if I am wrong, but, I have read that if the United States would harvest every photon of light from the Sun that such energy (in Joules) would only meet 50% of that which we consume.

I don’t think that’s correct. To meet all US energy needs would require about 21 000 square miles of solar panels (less, if the technology improves). This is tiny.

Boru

We use 93 quadrillion BTUs annually; one BTU is 1055.06 joules; a quadrillion is 10^15, and so, the US uses approximately 10^20 joules per annum:

EIA -- US energy

The Sun gives us 1360 watts per square meter.

NASA Earth Observatory

The US has 3.797 million square miles, and so,

3,797,000 square miles * (2,590,000 square meters / 1 square mile) = 9,834,230,000,000 square meters in the US, or 9.8 * 10^12 square meters.

Taking 10^20 joules / (365*24*3600 seconds) = 3.17 * 10^12 watts

Taking 3.17 * 10^12 watts / 1360 watts per square meter = 2.33 * 10^9 square meters of solar panels.

And, so, we need a few hundred million square meters of solar panels, a 100,000 km by 10,000 km array.  Not enough land, or so it appears.