  We propose a procedure for the renormalization of Casimir energy, that is
based on the implicit versions of standard steps of renormalization procedure
--- regularization, subtraction and removing the regularization. The proposed
procedure is based on the calculation of a set of convergent sums, which are
related to the original divergent sum for the non-renormalized Casimir energy.
Then one constructs a linear equations system, that connects this set of
convergent sums with the renormalized Casimir energy, which is a solution to
this equations system. This procedure slightly reduces the indeterminancy that
arises in standard procedure when we choose the particular regularization and
the explicit form of counterterm. The proposed procedure is more efficient from
the computational point of view than the standard one. It can be applied not
only for systems with the explicit transcendental equation for the spectrum,
but also for systems with the spectrum that can be obtained only numerically.
