  We propose a cyclic refrigeration principle based on mesoscopic electron
transport. Synchronous sequential tunnelling of electrons in a
Coulomb-blockaded device, a normal metal-superconductor single-electron box,
results in a cooling power of $\sim k_{\rm B}T \times f$ at temperature $T$
over a wide range of cycle frequencies $f$. Electrostatic work, done by the
gate voltage source, removes heat from the Coulomb island with an efficiency of
$\sim k_{\rm B}T/\Delta$, where $\Delta$ is the superconducting gap. The
performance is not affected significantly by non-idealities, for instance by
offset charges. We propose ways of characterizing the system and of its
practical implementation.
