Systems and methods for generating electrical power in an organic Rankine cycle (ORC) operation include one or more heat exchangers incorporated into mobile heat generation units, and which will receive a heated fluid flow from one or more heat sources, and transfer heat therefrom to a working fluid that is circulated through an ORC unit for generation of power. In embodiments, the mobile heat generation units comprise pre-packaged modules with one or more heat exchangers connected to a pump of a recirculation system, including an array of piping, such that each mobile heat generation unit can be transported to the site and installed as a substantially stand-alone module or heat generation assembly.

Embodiments of systems and methods for generating power in the vicinity of a drilling rig are disclosed. During a drilling operation, heat generated by drilling fluid flowing from a borehole, exhaust from an engine, and/or fluid from an engine's water (or other fluid) jacket, for example, may be utilized by corresponding heat exchangers to facilitate heat transfer to a working fluid. The heated working fluid may cause an ORC unit to generate electrical power.

Systems and methods for variable pressure inventory control of a closed thermodynamic cycle power generation system or energy storage system, such as a reversible Brayton cycle system, with at least a high pressure tank and an intermediate pressure tank are disclosed. Operational parameters of the system such as working fluid pressure, turbine torque, turbine RPM, generator torque, generator RPM, and current, voltage, phase, frequency, and/or quantity of electrical power generated and/or distributed by the generator may be the basis for controlling a quantity of working fluid that circulates through a closed cycle fluid path of the system.

A heat exchanger has arcuate inlet and outlet manifolds and a plurality of tube banks, each tube bank coupling one of the inlet manifold outlets to an associated one of the outlet manifold inlets. Each tube bank partially nests with one or more others of the tube banks and has: a first header coupled to the associated inlet manifold outlet and the associated the outlet manifold inlet; a second header; and a plurality of tube bundles each having a first end coupled to the associated first header and a second end coupled to the associated second header. A flowpath from the each inlet manifold outlet passes sequentially through flowpath legs formed by each of the tube bundles in the associated tube bank to exit the tube bank to the associated outlet manifold inlet.

Aspects of the invention generally provide a heat engine system and a method for activating a turbopump within the heat engine system during a start-up process. The heat engine system utilizes a working fluid circulated within a working fluid circuit for capturing thermal energy. In one exemplary aspect, a start-up process for a turbopump in the heat engine system is provided such that the turbopump achieves self-sustained operation in a supercritical Rankine cycle. Bypass and check valves of a start pump and the turbopump, a drive turbine throttle valve, and other valves, lines, or pumps within the working fluid circuit are controlled during the turbopump start-up process. A process control system may utilize advanced control techniques of the control sequence to provide a successful start-up process of the turbopump without over pressurizing the working fluid circuit or damaging the turbopump via low bearing pressure.

Aspects of the invention disclosed herein generally provide a heat engine system, a turbopump system, and methods for lubricating a turbopump while generating energy. The systems and methods provide proper lubrication and cooling to turbomachinery components by controlling pressures applied to a thrust bearing in the turbopump. The applied pressure on the thrust bearing may be controlled by a turbopump back-pressure regulator valve adjusted to maintain proper pressures within bearing pockets disposed on two opposing surfaces of the thrust bearing. Pocket pressure ratios, such as a turbine-side pocket pressure ratio (P1) and a pump-side pocket pressure ratio (P2), may be monitored and adjusted by a process control system. In order to prevent damage to the thrust bearing, the systems and methods may utilize advanced control theory of sliding mode, the multi-variables of the pocket pressure ratios P1 and P2, and regulating the bearing fluid to maintain a supercritical state.

Aspects of the invention disclosed herein generally provide a heat engine system, a turbopump system, and methods for lubricating a turbopump while generating energy. The systems and methods provide proper lubrication and cooling to turbomachinery components by controlling pressures applied to a thrust bearing in the turbopump. The applied pressure on the thrust bearing may be controlled by a turbopump back-pressure regulator valve adjusted to maintain proper pressures within bearing pockets disposed on two opposing surfaces of the thrust bearing. Pocket pressure ratios, such as a turbine-side pocket pressure ratio (P1) and a pump-side pocket pressure ratio (P2), may be monitored and adjusted by a process control system. In order to prevent damage to the thrust bearing, the systems and methods may utilize advanced control theory of sliding mode, the multi-variables of the pocket pressure ratios P1 and P2, and regulating the bearing fluid to maintain a supercritical state.

Described herein is a working fluid for a thermodynamic cycle that includes CO.sub.2 as main component and one or more of the compounds selected from the group including: TiCl.sub.4, TiBr.sub.4, SnCl.sub.4, SnBr.sub.4, VCl.sub.4, VBr.sub.4, GeCl.sub.4, metal carbonyls, by way of example Ni(CO).sub.4.

Aircraft power plants including combustion engines, and associated methods for recuperating waste heat from such aircraft power plants are described. A method includes transferring the heat rejected by the internal combustion engine to supercritical CO.sub.2 (sCO.sub.2) used as a working fluid in a heat engine. The heat engine converts at least some the heat transferred to the sCO.sub.2 to mechanical energy to perform useful work onboard the aircraft.

Systems and generating power in an organic Rankine cycle (ORC) operation to supply electrical power. In embodiments, an inlet temperature of a flow of gas from a source to an ORC unit may be determined. The source may connect to a main pipeline. The main pipeline may connect to a supply pipeline. The supply pipeline may connect to the ORC unit thereby to allow gas to flow from the source to the ORC unit. Heat from the flow of gas may cause the ORC unit to generate electrical power. The outlet temperature of the flow of the gas from the ORC unit to a return pipe may be determined. A bypass valve, positioned on a bypass pipeline connecting the supply pipeline to the return pipeline, may be adjusted to a position sufficient to maintain temperature of the flow of gas above a threshold based on the inlet and outlet temperature.