Parabolic trough
The parabolic trough is a parabolic shaped trough. In the section perpendicular to the channel axis, the concave borderline is a parabola.
Compared to the parabolic mirror , which is limited by a paraboloid of revolution , it can be designed as a simply curved concave mirror with which incident plane waves are reflected in such a way that they run towards a line ( focal line ).
When used as a light mirror, a parabolic trough has similar properties to a cylindrical lens .
Focus property of parabolic surfaces
A parabola can be defined as follows :
"A parabola is the geometric location of all points P, whose distance to a special fixed point - the focal point F - is the same as that to a special straight line - the guide line l." (See graphic)
The perpendicular PG is the tangent to the parabola at point P. It forms the same angle with the ray PF and the perpendicularly incident ray, so it reflects the latter in the direction of F, the focal point.
Moving a parabola along a straight line perpendicular to the plane containing it creates the inner surface of a parabolic trough.
application
Incident parallel rays are focused in a line, or rays emerging from this line are emitted in parallel.
Solar panels
Parabolic troughs are used in parabolic trough power plants as solar collectors for bundling rays in a line. There is a pipe concentric to the focal line, in which a heat transfer medium such. B. Oil, is heated by the sun . In contrast to the mostly biaxially mounted parabolic mirror, when solar energy is used, the parabolic trough is only tracked in one axis to the elevation angle of the sun; this is easier to implement and therefore cheaper to purchase and maintain.
to shine
Reflectors in luminaires are often parabolic troughs if an elongated lamp is used. A parallel alignment of rays emanating from a line takes place.
Flashing lights that are bundled in this way (mostly in the vertical) are not only found in photography , they can also be found in the light bars of vehicles used by the police , fire brigades and rescue services .
Web links
- ParabolaTool - program for calculating the shape of a parabolic trough