Heat engine and heat to electricity systems and methods with working fluid mass management control

A heat engine system, comprising:

• a working fluid circuit configured to circulate a working fluid through a high pressure side and a low pressure side of the working fluid circuit, wherein the working fluid comprises carbon dioxide;
• a heat exchanger fluidly coupled to the working fluid circuit, configured to be fluidly coupled to and in thermal communication with a heat source, and configured to transfer thermal energy from the heat source to the working fluid within the high pressure side of the working fluid circuit;
• an expander fluidly coupled to the working fluid circuit between the low pressure side and the high pressure side and disposed downstream of the heat exchanger in the working fluid circuit;
• a recuperator fluidly coupled to the low pressure side and the high pressure side of the working fluid circuit and configured to transfer thermal energy between the low pressure side and the high pressure side;
• a cooler fluidly coupled to the working fluid circuit, disposed downstream of the recuperator, and configured to control a temperature of the working fluid in the low pressure side;
• a pump fluidly coupled to the working fluid circuit between the low pressure side and the high pressure side, disposed downstream of the cooler, and configured to circulate the working fluid through the working fluid circuit;
• and
• a mass management system fluidly coupled to the working fluid circuit and configured to regulate a pressure and an amount of the working fluid within the working fluid circuit, the mass management system further comprises:
• a mass control tank fluidly coupled to the working fluid circuit;
• and
• a control system communicably coupled to the working fluid circuit at a first sensor disposed upstream of an inlet of the pump and at a second sensor disposed downstream of an outlet of the pump, and communicably coupled to the mass control tank at a third sensor disposed either within or adjacent the mass control tank.

A method for regulating a pressure and an amount of a working fluid in a thermodynamic cycle, comprising:

• placing a thermal energy source in thermal communication with a heat exchanger disposed within a working fluid circuit, the working fluid circuit containing the working fluid and having a high pressure side and a low pressure side, and the working fluid comprises carbon dioxide;
• circulating the working fluid through the working fluid circuit with a pump;
• expanding the working fluid in an expander to generate mechanical energy;
• sensing operating parameters of the working fluid circuit with first and second sensor sets communicably coupled to a control system, wherein the first sensor set is configured to sense at least one of an inlet pressure and an inlet temperature proximate an inlet of the pump, and the second sensor set is configured to sense at least one of an outlet pressure and an outlet temperature proximate an outlet of the pump;
• extracting the working fluid from the working fluid circuit at a first tie-in point on the working fluid circuit and transferring the working fluid to a mass control tank fluidly coupled to the first tie-in point;
• and
• injecting the working fluid from the mass control tank into the working fluid circuit via a second tie-in point on the working fluid circuit while increasing a suction pressure of the pump.