Solar dish/engine systems use a dish-shaped collection of mirrors to collect and focus the sun's energy onto a power conversion unit, located at the focal point of the dish. The dish structure must track the sun continuously to reflect the beam into the thermal receiver. Dish/engine systems are still in development, although a number of dish/engine prototypes have been built as part of the continuing research program.
The power conversion unit includes a thermal receiver and an engine/generator. The thermal receiver absorbs the concentrated solar energy and transfers the heat to the engine/generator. A thermal receiver can be a bank of tubes with a cooling fluid, usually hydrogen or helium, which is the heat transfer medium and also the working fluid for an engine. Thermal receivers may also use "heat pipes"—devices that contain a fluid that boils on the hot end and then condenses against the cool end, transferring the heat to the engine.
The engine/generator system takes the heat from the thermal receiver and produces electricity. The most common type of heat engine used in dish-engine systems is the Stirling engine. A Stirling engine uses heat to expand the fluid, which moves a piston, which in turn is used to drive a generator and produce electrical power. In addition to the Stirling engine, microturbines and concentrating photovoltaic receivers are also being evaluated as possible future power conversion unit technologies