Thermal energy conversion method

A method for controlling inlet pressure of a pump in a closed loop thermodynamic cycle, comprising:

• circulating a working fluid in a working fluid circuit that includes the pump fluidly coupled to an expander that is operative to convert energy from the working fluid into mechanical energy, the working fluid circuit including a high pressure side and a low pressure side;
• receiving in a control system a first pressure detected at the high pressure side of the working fluid circuit via a plurality of sensors;
• receiving in the control system a second pressure detected at the low pressure side of the working fluid circuit via the plurality of sensors;
• adding or removing working fluid mass from the working fluid circuit via a mass management system based on the first pressure, the second pressure, or a combination thereof, the mass management system being connected to the working fluid circuit and having a working fluid vessel fluidly coupled to the low pressure side of the working fluid circuit, wherein one or more valves coupled to the mass management system are actuated in the control system to add or remove the working fluid mass from the working fluid circuit;
• receiving in the control system a third pressure detected in the working fluid vessel via the plurality of sensors;
• determining in the control system whether the third pressure is less than the second pressure;
• and
• adding additional working fluid to the working fluid vessel and adding working fluid mass into the low pressure side of the working fluid circuit from the working fluid vessel via the mass management system if the third pressure is less than the second pressure.