In some embodiments, the heat transfer structures are straight fins that define two electrochemical chambers adjacent to one another, which are each divided by ion-transfer membranes positioned therein to create a first channel and a second channel in each electrochemical chamber. In some embodiments, the electrochemical chambers allow flow of the first electrochemical fluid in the first channel and the second electrochemical fluid in the second channel. In other examples, at least part of the heat transfer structure may be curved or have a curved portion. For example, a first heat transfer structure may be curved relative to another heat transfer structure such that the cross-sectional area of a channel varies in a flow direction of the electrochemical fluid. In at least one embodiment, the cross-sectional area of a channel increases in the direction of flow to decrease the velocity of the electrochemical fluid through the channel. In at least one embodiment, the cross-sectional area of a channel decreases in the direction of flow to increase the velocity of the electrochemical fluid through the channel.