  We discuss the time-convolutionless (TCL) projection operator approach to
transport in closed quantum systems. The projection onto local densities of
quantities such as energy, magnetization, particle number, etc. yields the
reduced dynamics of the respective quantities in terms of a systematic
perturbation expansion. In particular, the lowest order contribution of this
expansion is used as a strategy for the analysis of transport in "modular"
quantum systems corresponding to quasi one-dimensional structures which consist
of identical or similar many-level subunits. Such modular quantum systems are
demonstrated to represent many physical situations and several examples of
complex single-particle models are analyzed in detail. For these quantum
systems lowest order TCL is shown to represent an efficient tool which also
allows to investigate the dependence of transport on the considered length
scale. To estimate the range of validity of the obtained equations of motion we
extend the standard projection to include additional degrees of freedom which
model non-Markovian effects of higher orders.
