Network analysis of nanoscale energy conversion processes

Energy conversion in nanosized devices is studied in the framework of state-space models. We use a network representation of the underlying master equation to describe the dynamics by a graph. Particular segments of this network represent input and output processes that provide a way to introduce a coupling to several heat reservoirs and particle reservoirs. In addition, the network representation scheme allows one to decompose the stationary dynamics as cycles. The cycle analysis is a convenient tool for analyse models of machine operations, which are characterized by different nanoscale energy conversion processes. By introducing the cycle affinity, we are able to calculate the zero-current limit. The zero-current limit can be mapped to the zero-affinity limit in a network representation scheme. For example, for systems with competing external driving forces the open-circuit voltage can be determined by setting the cycle affinity zero. This framework is used to derive open-circuit voltage with respect to microscopic material energetics and different coupling to particle and temperature reservoirs.