Tungsten halogen projection lamps have integral ellipsoidal reflector, and hexagonal shaped plastic Fresnel lenses. Reflector is dichroic coated to reduce infrared content of reflected radiation. Array of lamps and lenses produces uniform collimated beam having near AM2 spectrum and intensity that can be used for testing flat plate solar collectors

Curtis, H. B.

Harlamert, P., Jr.

Yass, K.

English

NASA Technical Reports Server

September 1974	 B74-10086 
•	
NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce now 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 Technical 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. 
A. Low Cost "Air Mass 2" Solar Simulator 
.
The Problem: 
Much of the development and testing of Earth based 
solar collectors has been done by exposure to the Sun 
itself. Obvious disadvantages of depending on the Sun, 
however, are limited daylight and inclement weather. One 
alternative to such dependence is to use a solar simulator 
capable of duplicating most of the Sun's characteristics as 
they might appear to a solar collector on the Earth's 
surface. On a clear day when the Sun angle is 600 from 
the zenith, the optical path of the Sun's radiation to the 
Earth's surface produces the air mass 2 (AM2) solar curve 
or spectrum. This spectrum best represents the , average 
North American sunlight. It is different from the air mass 
1 (AM 1) spectrum, when the Sun is located at its zenith 
(directly overhead), or the air mass zero (AMO) spectrum, 
which is obtained when the collector is located outside 
the atmosphere in Earth orbit. A low cost solarsimulator 
(AM2) was required for testing flat-plate solar collectors. 
Most commercial solar simulators use expensive high 
pressure arc lamps which, because of explosion possi-
bilities, require safety equipment during handling. These 
commercial units use direct current and therefore require 
separate power supplies. They also use expensive quartz 
optics. 
The Solution: 
A solar simulator constructed of low cost commercially 
available components consisting of tungsten halogen 
projection lamps each having an integral ellipsoidal reflec-
tor, and hexagonal shaped plastic Fresnel lenses. The 
reflector is dichroic coated to reduce the infrared content 
of the reflected radiation. An array of these lamps and 
lenses produces a uniform collimated beam having a near 
AM2 spectrum and intensity that can be used for testing 
flat plate solar collectors. 
How It's Done: 
A cutaway view of the simulator is shown in Figure 1. 
The simulator consists of an array of 143 tungsten 
halogen 300 watt 120V lamps, each having integral-
dichroic-coated reflectors. The square frontal section is 
covered with 143 hexagonal shaped Fresnel lenses in a 
closely fitted array. The optical axis of each lamp is 
coincident with that of its respective lens.
FIGURE 1 
Power requirements are approximately 44 kilowatts of 
120-volt, single-phase electrical power for the lamps and 
1.1 kilowatts of 208-volt, three-phase power for the 
exhauster motor. 
Power to the lamps is controlled through two switches 
at the console. Each switch operates a motor driven bank 
of autotransformers, and the output voltage of each bank 
is directed to half the lamps of the simulator. This wiring 
plan effectively divides the load between two 200-ampere 
capacity mains. Although other wiring and control 
schemes exist, this multiple autotransformer arrangement 
was used because the components were available. 
The simulator produces a uniform collimated beam 
covering an area of 1.2 x 1.2 m (4 x 4 ft). Since the 
simulator uses readily available standard components and 
is modular in design, the area coverage can be scaled up or 
down by the addition or deletion of lamp-lens combina-
tions.
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and S pace Administration. Neither the United States 	 information contained in this document, or warrants that Such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19740000086 2020-03-17T14:05:45+00:00Z
. 
FIGURE 2 
In Figure 2, the solar simulator is suspended to 
irradiate the collector on the floor below at zero incidence 
angle and at a separation distance of 4.6 m (15 ft). This 
position is adjustable through angles of 25 to 72 0 from 
the horizontal to accommodate different collector tilt 
angles. 
Notes: 
1. Capital cost of the (AM2) simulator is' less than 
$10,000/sq meter ($ l000/ft2 ) compared to costs of 
from $133,000 to $291,000/sq meter ($12,000 to 
$27,000/ft2 ) for conventional (AMO) simulators. 
2. In addition to testing flat plate collectors, the simula-
tor can also be used for testing paint, glass and other 
materials. 
3. For testing restricted to small areas, an inexpensive 
simulator using a minimum of 12 lamps (in order to 
give uniform coverage) can be constructed from ply
-wood and sheet metal. 
4. Further information is available in the following 
report: 
NASA TM-X-3059 (N74 .27719), Low-Cost, Air 
Mass 2 Solar Simulator
Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812.337-7833 
Reference: B74-10086 
5. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B74-10086 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: K. Yass, H.B. Curtis 
and P. Harlamert, Jr.
Lewis Research Center
(LEW. I 2266)
. 
B74-10086	 Category 02
0


A low cost ""Air Mass 2'' solar simulator

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