  We propose a simple protocol exploiting the thermalization of a
$\textit{storage}$ bipartite system $S$ to extract work from a
$\textit{resource}$ system $R$. The protocol is based on a recent work
definition involving only a single bath. A general description of the protocol
is provided without specifying the characteristics of $S$. We quantify both the
extracted work and the ideal efficiency of the process also giving maximum
bounds for them. Then, we apply the protocol to two cases: two interacting
qubits and the Rabi model. In both cases, for very strong couplings, an
extraction of work comparable with the bare energies of the subsystems of $S$
is obtained and its peak is reached for finite values of the bath temperature,
$T$. We finally show, in the Rabi model at $T=0$, how to transfer the work
stored in $S$ to an external device, permitting thus a cyclic implementation of
the whole work-extraction protocol. Our proposal makes use of simple operations
not needing fine control.
