Mechanism is simpler and lower in cost because it moves heat-collector pipe to stay in focus with sun, instead of moving heavy reflectors

Miller, C. G.

Stephens, J. B.

English

NASA Technical Reports Server

	September 1975
	
.	 B75-10210 
•	 .
 
NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Tehnical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Secondary Reflectors for Economical Sun-Tracking

Energy Collection System:A Concept 
Two new secondary reflectors are being proposed 
for a new Sun-tracking energy collection system [see 
NASA Tech Brief B7540209 (NPO-13579)]. The 
mechanism is simpler and lower in cost because it 
moves the heat-collector pipe to stay in focus with the 
Sun. Normally, expensive tracking mechanisms are 
used to move heavy solar energy-collecting reflectors. 
In the new configuration, solar energy is collected 
by a large main reflector installed on the ground. The 
heat-collector pipe is situated on a tracking mech-
anism above the main reflector. The secondary 
reflectors are placed adjacent to the pipe. Solar energy 
bouncing off the main reflector is focused onto the 
pipe by the secondary reflectors. These are moved 
with the pipe to track the Sunrays coming from the 
main reflector. 
Figure 1. Doubly-Curved Concave Secondary Reflectors
U...., r_.II....._..
ndary 
?ctor 
Incoming Solar Energy From

Main Reflector 
Figure 2. Bell-Shaped Secondary Reflectors 
The secondary reflectors can be configured in two 
ways. In Figure 1 the reflectors are doubly-curved 
concave strips focused onto different sections of the 
pipe. Beams coming from the main reflector are 
focused onto the pipe, forming concentrated hotspots 
to heat the fluid inside. This results in a 
higher-temperature than can be produced with 
uniformly-heated pipe. The entire configuration 
moves over the main reflector surfaces to stay in focus 
with the Sun. 
In Figure 2, two of a series of bell-shaped reflectors 
are shown. Energy entering the open mouth of a bell is 
trapped inside. The hotspots formed on the pipe can 
reradiate only through a restricted solid angle. This 
prevents heat loss from the pipe due to reradiation. 
Heat losses by convection are also prevented because 
of the geometry. Hot air in the vicinity of the pipe is 
not allowed to escape because the upper end of the 
bell is closed.
'lation 
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19750000210 2020-03-19T20:27:02+00:00Z
Note: 
Requests for further information may be directed 
to:
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NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP75-10210
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning 
nonexclusive or exclusive license for its commercial 
development should be addressed to: 
Patent Counsel 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: Charles G. Miller and

James B. Stephens of
Caltech/JPL
(NPO-13580) 
Categories: 03 (Physical Sciences) 
B75.10210	 06 (Mechanics)


Secondary reflectors for economical sun-tracking energy collection system: A concept

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