## Comment: Re:"free" solar energy (Score 3, Interesting) 107

(sorry, lost formatting)

Let's math:

Assuming that the miles high pyramid uses free sun power to melt sand and we only need PV to power lifting the glass blocks

The great pyramid of giza is 455' tall and has 10^12 joules of potential energy (http://what-if.xkcd.com/95/)

A 2 mile high pyramid with the same dimensions is about 12x taller

If you scale up the pyramid by 12, that's 12^4x more energy (http://www.physicsforums.com/showthread.php?t=428636)

12^4*10^12 joules=2e16 joules = 5e9 kWh

Wholesale price of electricity is 5 cents per kWh

5e9 kWh *

This could easily triple depending on motor losses and other energy costs. So you could make your giant pyramid with "free" energy or you could sell the energy on the open market for almost a billion dollars