Parabolic solar collector

Abstract

A passive solar collector utilizes a support constructed of precisely machined foam to simplify the construction and calibration of the reflective surface. Further improvements include sensor-based positioning, and a receiver having inflow and outflow conduits adapted to improve thermal efficiency.

What is claimed is: 
     
         1 . A parabolic solar collector, comprising:
 a parabolic reflector having a focal line or focal point;   a receiver positioned at the focal line or focal point of the reflector carrying a heat transfer fluid;   a foam base adhesively attached to and supporting the reflector, the foam base having a curved surface determining the focal line or focal point; and   a rigid cradle supporting the foam base and surrounding the receiver.   
     
     
         2 . The parabolic solar collector according to  claim 1 , wherein the foam base is formed in a shape of a parabolic trough, and the receiver is positioned along a focal line parallel to a longitudinal axis of the parabolic trough. 
     
     
         3 . The parabolic solar collector according to  claim 1 , wherein the foam base is formed in the shape of a parabolic dish, and the receiver passes through a focal point and a vertex of the parabolic dish. 
     
     
         4 . The parabolic solar collector according to  claim 1 , wherein the foam base is constructed of a foam having a density in the range of about 0.5 lb/ft 3  to about 10 lb/ft 3 . 
     
     
         5 . The parabolic solar collector according to  claim 1 , wherein the foam base is expanded polystyrene having a density in a range of about 0.9 to 2.2 lbs/ft 3 . 
     
     
         6 . The parabolic solar collector according to  claim 2 , further comprising a glass cover sealing a space above the reflector and the receiver. 
     
     
         7 . The parabolic solar collector according to  claim 6 , wherein the glass cover is low-iron glass. 
     
     
         8 . The parabolic solar collector according to  claim 6 , further comprising thermal insulation along opposite sides of the cradle extending vertically from the base to the cover. 
     
     
         9 . The parabolic solar collector according to  claim 1 , wherein the reflector is a polished aluminum sheet material. 
     
     
         10 .- 22 . (canceled) 
     
     
         23 . A method of making a parabolic solar collector, comprising the steps of:
 cutting a rigid foam material to form a foam base segment having a parabolic surface of predetermined dimensions;   assembling the base in a cradle;   adhering a reflective material on the focusing surface; and   positioning a receiver carrying a heat transfer fluid with respect to the base and cradle at the focal point or focal line of the parabolic surface, so that solar rays incident on the focusing surface are focused on the receiver.   
     
     
         24 . The method according to  claim 23 , wherein the step of cutting a rigid foam material is conducted by providing a computer aided design (CAD) file to a computer numerical control (CNC) cutting machine to form a parabolic surface. 
     
     
         25 . The method according to  claim 23 , wherein the foam is expanded polystyrene having a density of 0.90 lb/ft 3  to about 2.2 lb/ft 3 . 
     
     
         26 . The method according to  claim 24 , wherein the CNC machine is programmed to cut the curved focusing surface in the shape of a parabolic trough to form a one piece foam base.