motivation - principle - [concentrator] - stirling enginereceiver - costs & markets

The concentrator supplies the fuel for the Stirling engine. It collects and focuses the solar radiation in one point. To achieve high efficiencies, the concentrator must focus as much as possible of the incident solar radiation onto the receiver of the Stirling engine. Therefor the shape of the concentrator surface may deviate only slightly from the ideal parabola. To reach a high accuracy in shape together with a rigid and light weight construction, we have developed the stretched metal membrane technology, whereby, on the front and rear side of a cylindrical housing ring, a thin - only some tenth of millimeters thick - stainless steel membrane is welded. The front membrane is deformed plastically into a paraboloid shape by applying air underpressure from inside the housing and water ballast from outside (Fig.4).
To provide the front membrane with a high reflectivity (94%) and durability thin glass mirrors are glued to surface. The completed rigid drum is then mounted on a supporting frame structure that tracks the sun biaxially azimuthal or polar by means of electric motor drives (Fig.5).

Fig.4: Shaping load case of a metal
membrane concentrator

Fig.5: Six stretched-membrane parabolic dish concentrators at the Plataforma Solar de Almeria/Spain developed by SBP:

a) Three 7,5 m concentrators, with
a) V-160 Stirling engine and polar
a) trecking (left rear);
b) Three 8,5 m concentrators with

a) V-161 Stirling engine and azimuthel
a) trecking (right front)