Methods and systems for starting and stopping a closed-cycle turbomachine

In a system for generating power utilizing a closed cycle with a working fluid, when the working fluid is in a supercritical state, the closed cycle including a turbomachine comprising a supercritical fluid compressor connected via a shaft to a supercritical fluid turbine, a method for starting the turbomachine comprising the steps of:

• a) charging a mass of working fluid that is not in the supercritical state in the closed cycle up to a starting mass that is greater than a design operating mass, wherein the design operating mass is the mass of working fluid in the closed cycle when operating at steady-state design point conditions;
• b) heating the working fluid;
• and
• c) venting a discharge mass of working fluid from the closed cycle at a location in the closed cycle that is on an exhaust side of the supercritical fluid turbine.