Power flash cycles (PFC) are a generalization of trilateral cycles (TLC) in which the compressed liquid is heated up to its boiling point and then performs a flash expansion during which it delivers power. The end point of the expansion may be in the wet vapour region (TLC) or in the dry vapour region. Here model results are presented for PFC-systems including the heat transfer to and from the cycles with aromates, siloxanes, and alkanes as working fluids. Optimization criterion is the exergy efficiency for power production at different pairs of heat carrier and cooling agent inlet temperatures ranging from (350 degrees C, 62 degrees C) to (150 degrees C, 15 degrees C). Comparisons with TLC for water, organic Rankine cycles (ORC) and water Clausius-Rankine cycles are made. General findings are that PFC has higher power production efficiencies than ORC but larger volume flows at the expander outlet. Moreover, TLC with water have in all cases the highest or nearly highest power production efficiencies. The disadvantage of water are the large outlet volume flows at low temperatures. For these cases alkanes like cyclopentane are to be preferred in PFC which can have significantly smaller outlet volume flows and rather high power production efficiencies. (C) 2012 Elsevier Ltd. All rights reserved.