Central receiver systems utilize the concept of a parabolic dish sliced into pieces and arranged flat on the ground.
The large mirror on the right of the above photo is 40 feet on a side and composed of 100 4-by-4-foot mirror panels. The surface of the mirror has been curved to produce a focused beam 8-10 feet in diameter at 800 feet. The concentration achieved is about 30 times the normal strength of the Sun or '30 suns'.
The central 250-foot tower is surrounded by 224 smaller heliostats. This installation was designed for testing thermal receivers used in producing steam for electric generation. There are four target bays where receivers can be mounted, three lower bays and a pedestal on the very top.
To offer a reference point of the amount of heat produced by the main field, with only 10% of the mirrors focused on target, it takes a mere 20 seconds to melt a 12-inch hole in a 1-inch thick sheet of steel.
A typical thermal receiver in this type of application uses molten salt to transfer heat from the boiler at the focal point to a heat transfer device where it creates dry steam for a steam generator near the base of the tower.