Describe how 'steam stacking' affects turbine efficiency, and detail methods to mitigate it.

Steam stacking, in the context of geothermal power plants, refers to the accumulation of steam in the turbine casing or other parts of the steam path during startup, shutdown, or low-load operation. This accumulation happens when the steam flow is insufficient to effectively remove the steam already present in the turbine. This affects turbine efficiency primarily by causing increased back pressure on the turbine blades. The increased back pressure reduces the pressure drop across the turbine stages, which directly lowers the amount of work that can be extracted from the steam, thus reducing power output. Furthermore, steam stacking can lead to uneven temperature distribution within the turbine, causing ....