  This paper proposes a framework for the procurement of flexibility reserve
from aggregated storage fleets. It allows for arbitrary tree structures of
aggregation hierarchy, as well as easily implementable disaggregation via
broadcast dispatch. By coupling discharge and recovery modes, the proposed
framework enables full-cycle capacity to be procured ahead of real time, with
guaranteed recovery and exact accounting for losses. The set of feasible
discharging requests is exactly encoded, so that there is no reduction in the
ability to meet discharging signals, and recovery capabilities are parametrised
as a single virtual battery. Included in this paper is a numerical
demonstration of the construction of the constituent curves of the framework
and the approach is also benchmarked against relevant alternatives.
