A stirling system is basically a heat engine that converts heat into some sort of mechanical work by a series of cyclical expansiona snd contractions of air or gases. Dish-Stirling Systems converts solar radiation into electrical energy. In the past 20 years, the Stirling energy system dish has held the world record in converting solar energy into electricity. In the year 2008, it achieved a new record with a 31.25% efficiency rate. This is all due to their modular design which gives them an edge in power output in both the small and large scale projects. They have thousands of dishes erected in a solar park. Two solar parks using the Stirling Energy Systems or SES systems, are currently being developed in US with a capacituy of 1.4GW.
The system consists of the following components:
In the simplest version, a Stirling engine consists of a sealed system with two cylinders (expansion and compression cylinder) filled with a working gas (helium). The pistons of these cylinders are connected to one crankshaft (The shaft for converting the up-and down piston motion into rotary). If the working gas in the expansion cylinder is heated (by the sun) it will expand due to the increasing temperature; pushes the piston down and thus induces power. Part of this power is now used to push the hot working gas from the expansion cylinder into the compression cylinder. On its way, the working gas passes through a re-generator where a major part of its heat is stored and also through a water cooled gas cooler, where it will be cooled further down. Once completely cooled in the compression cylinder, this piston will return due to the inertia of the crankshaft, and the working gas is compressed at low temperature. By reabsorbing the heat stored in the re generator the gas is pushed back into the working cylinder. On the whole, the expansion of the hot gas in the working cylinder delivers more energy than is needed for the compression of the cold gas in the compression cylinder. This surplus of energy can be used to operate an electric generator which is directly hooked to the crankshaft of the engine.
The parabolic concentrator reflects the incoming solar radiation onto a cavity receiver which is located at the concentrator ’s focal point. The solar radiation is absorbed by the heat exchanger (receiver) and thus heats the working gas (helium) of the Stirling engine to temperatures of about 650° C. This heat is converted into mechanical energy by the Stirling engine. An electrical generator, directly connected to the crankshaft of the engine, converts the mechanical energy into electricity (AC). To constantly keep the reflected radiation at the focal point during the day, a sun tracking system rotates the solar concentrator continuously about two axes to follow the daily path of the sun. The electrical output of the system is proportional to the size of the reflector, its optical losses and the efficiencies of the Stirling engine and the generator.