The vacuum energy is uniform in space; therefore, the Casimir energy does not affected by the orientation of the parallel conducting plates. The surface of two hemispheres, forming a hollow conducting sphere, can be depicted as the assembly of small parallel plates with different orientations. Super positioning the effects of these parallel plates allows calculating the Casimir energy for the two hollow conducting hemispheres. The derived equation identically recovers the physical content of the fine structure constant, and reproduces its value reasonably well. This agreement indicates that the fine structure constant is a scaling factor between the photon energy with wavelength of the circumference of the sphere and the electrostatic repulsion energies for the same size of sphere. The Casimir energy for the two hollow conducting hemispheres is three times higher than the electrostatic repulsion energy of a unit charge. This energy ratio is independent from the size of the sphere. Thus the Casimir energy exceeds the repulsion energy of the electron regardless of its size, which makes a viable alternative explaining the stability of the electron. Assuming that Planck energy sets a limit on the maximum photon energy, allows calculating the diameter of the electron, which is equivalent with the Planck length.