Abstract: A method, and associated apparatus, for generating power from medium temperature heat sources in the range of 200° to 700° C. with improved efficiency compared to systems operating on a Rankine cycle in which the working fluid is condensed at the same temperature. Water is heated in a boiler (11) with heat from the heat source A, (22) which may be a stream of exhaust gases (22), in order to generate wet steam having a dryness fraction in the range of 0.10 to 0.90 (10% to 90% dry). The wet steam is expanded to generate power in a positive displacement steam expander (21) such as a twin screw expander. The expanded steam is condensed at a temperature in the range of 70° C. to 120° C., and the condensed steam is returned to the boiler. The expanded steam may be condensed in the boiler of an Organic Rankine Cycle (22) to provide additional power, or by heat exchange with a heater of a heating system to provide a Combined Heat and cycle, thereby further improving the cycle efficiency.

Abstract: A screw machine for use with a working fluid with a liquid phase present comprises rotors having meshed, lubricated helical formations. The rotors have an ‘N’ profile as disclosed in WO 97/43550. In use, lubrication of the helical formations of the rotors and optionally of the rotor bearings is achieved substantially exclusively with the liquid phase of the working fluid.

Abstract: A vapour power generating system including a closed circuit for a working fluid, and includes a heat exchanger assembly for heating the fluid under pressure with heat from the source, a separator for separating the vapour phase of the heated fluid from the liquid phase thereof, an expander for expanding the vapour to generate power, a condenser for condensing the outlet fluid from the expander, a feed pump for returning condensed fluid from the condenser to the heater and a return path for returning the liquid phase from the separator to the heater. The liquid phase of the working fluid contains a lubricant which lubricant is soluble or miscible in the liquid phase and a bearing supply path is arranged to deliver liquid phase pressurised by the feed pump to at least one bearing for a rotary element of the expander.

Abstract: A vapor power generating system for generating power by using heat from a source of heat. The system has a closed circuit for a working fluid, and includes a heat exchanger assembly (1) for heating the fluid under pressure with heat from the source, a separator (8) for separating the vapor phase of the heated fluid from the liquid phase thereof, an expander (14) for expanding the vapor to generate power, a condenser (17) for condensing the outlet fluid from the expander (14), a feed pump (F) for returning condensed fluid from the condenser (17) to the heater and a return path for returning the liquid phase from the separator to the heater. The liquid phase of the working fluid contains a lubricant which lubricant is soluble or miscible in the liquid phase and a bearing supply path (21) is arranged to deliver liquid phase pressurized by the feed pump (F) to at least one bearing for a rotary element of the expander.

Abstract: A method, and associated apparatus, for generating power from medium temperature heat sources in the range of 200° to 700° C. with improved efficiency compared to systems operating on a Rankine cycle in which the working fluid is condensed at the same temperature. Water is heated in a boiler (11) with heat from the heat source A, (22) which may be a stream of exhaust gases (22), in order to generate wet steam having a dryness fraction in the range of 0.10 to 0.90 (10% to 90% dry). The wet steam is expanded to generate power in a positive displacement steam expander (21) such as a twin screw expander. The expanded steam is condensed at a temperature in the range of 70° C. to 120° C., and the condensed steam is returned to the boiler. The expanded steam may be condensed in the boiler of an Organic Rankine Cycle (22) to provide additional power, or by heat exchange with a heater of a heating system to provide a Combined Heat and cycle, thereby further improving the cycle efficiency.

Abstract: A vapour power generating system for generating power by using heat from a source of heat. The system has a closed circuit for a working fluid, and includes a heat exchanger assembly (1) for heating the fluid under pressure with heat from the source, a separator (8) for separating the vapour phase of the heated fluid from the liquid phase thereof, an expander (14) for expanding the vapour to generate power, a condenser (17) for condensing the outlet fluid from the expander (14), a feed pump (F) for returning condensed fluid from the condenser (17) to the heater and a return path for returning the liquid phase from the separator to the heater. The liquid phase of the working fluid contains a lubricant which lubricant is soluble or miscible in the liquid phase and a bearing supply path (21) is arranged to deliver liquid phase pressurised by the feed pump (F) to at least one bearing for a rotary element of the expander.

Abstract: An apparatus is provided for deriving mechanical power from expansion of a working fluid, other than water, from a liquid state at a first pressure to vapour at a second, lower pressure, which apparatus includes positive displacement machinery, wherein the in-built volumetric expansion ratio of the positive displacement machinery is between 10 and 50% of the overall volume ratio of expansion experienced by the fluid in the pressure reduction between the entry and the exit of the machinery.