The vapour generator (or boiler) consists of a coiled copper tube through which a pressurised working fluid runs. The coil is immersed in an insulated tank containing hot water provided by either an electric resistance heater which is housed within the tank, or by the optional solar energy collector mounted in a suitable position outside.
The vapour produced then flows through a convergent- divergent nozzle and impinges on the blades of a single stage impulse turbine. The turbine is mounted on the condenser and the exhaust vapour from it passes directly over the water-cooled coil. The condenser, which has a high strength glass shell, is partly flooded to provide the working fluid with a few degrees of sub-cooling. The working fluid is chosen for its low pressure-temperature characteristics allowing safe operation in glass.
An internal fixed speed positive displacement pump draws condensed solvent from the bottom of the condenser and delivers it, via a control valve and flow meter, to the vapour generator for re-evaporation.
A small quantity of lubricating oil mixed with the working fluid and is separated from the high-pressure vapour line and fed to the turbine bearings.
Maximum power is obtained at about 15,000 rev.min-1. A simple band brake dynamometer applies and measures the resisting torque to the turbine shaft. An optical sensor senses the rotational speed of the turbine, and this is displayed on a digital meter.
