A number of studies have shown that the Kalina cycle, using an ammonia-water mixture, can reach higher efficiencies than the normal steam Rankine cycle. In this paper, the Kalina cycle, with a gas turbine topping cycle is applied to cogeneration for district heating. Since the district heating temperatures vary with the heat demand over the year, this application may prove to be especially suitable for the Kalina cycle with its many degrees of freedom in the condensation system.
A theoretical comparison between different bottoming cycles producing heat for a typical Scandinavian district heating network has been carried out. The Kalina cycle, the Rankine cycle with a mixture of ammonia and water as the working fluid and the normal single pressure steam Rankine cycle are compared. It is shown that a simple Rankine cycle with an ammonia-water mixture as the working fluid produces more heat and power than the steam Rankine cycle. The best results, however, are obtained for the Kalina cycle, which generates considerably higher heat and power output than the steam Rankine cycle.