  We examine a Hamiltonian system which represents an active Brownian particle
that can move against an external force by drawing energy from an internal
depot while immersed in a noisy and dissipative environment. The Hamiltonian
consists of two subsystems, one representing the active particle's motion and
the other its depot of `fuel'. We show that although the active particle loses
some of its energy to dissipation from the environment, dissipation can also
help to stabilize the dynamical process that makes the particle active.
Additionally we show how a Hamiltonian active particle can harvest energy from
its environment.
