What's Worth a Spin

Earth's spin is 465.1 ms^-1. That gives a Spin Kinetic Energy of,

$SKE$ = 0.4*$\cfrac{{v}^{2}}{2}$ = 0.4*0.5*(0.4651)^(2) =  0.0433 km²s^-2

the 0.4 factor is the result of moment of inertia of  Earth modeled as a sphere, I = 0.4mr².

From,

$\triangle GPE = 3\cfrac{{g}_{e}{r}_{e}}{2}$

$\triangle GPE$ = 1.5*0.0098065*6371 = 93.716  km²s^-2

Assuming that SKE is converted from a change in total $GPE$, ie $\triangle GPE$, energy available for $RKE$ is,

$RKE$ = 93.716 - 0.0433 = 93.6727 km²s^-2

And so 

${V}_{e}$ = ( 2*93.6727 )^(0.5) = 13.69 kms^-1

Which is very much the same as calculated before, but still compared the measured speed of 29.78  kms^-1, although of the same order, is still way off.