Kalina cycle

The Kalina cycle is a thermodynamic cycle for converting thermal energy to mechanical power which utilizes working fluid comprised of at least two different components and a ratio between those components is varied in different parts of the system to increase thermodynamical reversibility and therefore increase overall thermodynamic efficiency. There are multiple variants of Kalina cycle systems specifically applicable for different types of heat sources. Several proof of concept power plants using the kalina have already been built.

The Kalina cycle was invented by the Russian engineer Aleksandr Kalina

The Kalina cycle engine, which is at least 10 percent more efficient than the other heat engines, is simple in design and can use readily available, off-the-shelf components. This new technology is similar to the Rankine cycle except that it heats two fluids, such as ammonia and water, instead of one. Instead of being discarded as waste at the turbine exhaust, the dual component vapor (70% ammonia, 30% water) enters a distillation subsystem. This subsystem creates three additional mixtures. One is a 40/60 mixture, which can be completely condensed against normal cooling sources. After condensing, it is pumped to a higher pressure, where it is mixed with a rich vapor produced during the distillation process. This recreates the 70/30 working fluid. The elevated pressure completely condenses the working fluid and returns it to the boiler to complete the cycle. The mixture's composition varies throughout the cycle. The advantages of this process include variable temperature boiling and condensing, and a high level of recuperation.

The U.S. Department of Energy completed a power plant using a Kalina cycle engine in 1991, at the Energy Technology Engineering Center in Canoga Park, California. The power plant may also improve heat engine efficiency through better thermodynamic matching in the boiler and distillation subsystem, and through recuperation of the heat from the turbine exhaust. Data from the early operating trials confirmed the principle of the Kalina Cycle technology. The technology is now being used in geothermal power plants.