Heliodon Model 126 Makes Daylight Simulation Easy

For over two decades, Auburn University professor Norbert Lechner has been teaching solar design with the help of his handcrafted, room-sized heliodon, a tool that simulates the motion of the sun relative to the Earth. Lechner is perhaps the world’s premier heliodon buff and has made a hobby of publishing and giving away do-it-yourself heliodon plans. (Lechner is also author of Heating, Cooling, Lighting; see EBN Vol. 10, No. 5.) He’s in it for ideological reasons, Lechner told EBN, “because solar responsive design is vital for a sustainable future, and solar responsive design is best learned with a heliodon.”

In Lechner’s experience, “heliodons allow the least technically inclined or interested to design with the sun,” and he believes that no architecture school or office should be without some sort of heliodon. Frustrated that, despite his encouragement, no other schools copied his own model, “I decided that I must design another one of equal conceptual clarity but that is smaller and does not have to be custom-built by each school,” he said. Lechner’s scaled-down Model 126 Heliodon, or Sun Emulator, is now available from High Precision Devices, Inc. of Boulder, Colorado.

Heliodons must represent variations in season and time of day, and often accommodate various latitudinal positions as well. They generally fall into three categories: In the first, the building model is fixed while the light source (representing the sun) rotates and tilts; in the second, the light is fixed while the model moves; and in the third, both the model and the light move. Although any of the varieties can effectively inform design decisions, the first makes the best teaching tool, because it most closely resembles the way we perceive the Earth’s motion around the sun.

Lechner’s heliodon is of the fixed-model variety. Seven parallel hoops, each supporting one lamp, simulate the 21st day of each month for any latitude on Earth at any time of day. The least expensive do-it-yourself heliodon costs about $20 in materials and can easily fit on a desk. Lechner’s manufactured, full-featured Model 126 costs just shy of $13,000 and requires the storage space of a closet: in its storage position, the Sun Emulator measures 6’ long, 6’ high, and 2’ wide (1.8 x 1.8 x 0.6 m).

According to Naomi Tepper of High Precision Devices, the first Model 126 Heliodons were custom-made in 1998 for the National Renewable Energy Laboratory (NREL) and for Professor Lechner himself. Since then, five more have been sold to universities in the U.S., Canada, and Mexico. High Precision Devices is proud to report “aha!” responses to the Sun Emulator from students and professionals alike. Tepper told EBN that 38 institutions are actively pursuing purchasing Sun Emulators. High Precision hopes that a new lease-to-own program through Wells Fargo Bank will make it easier for architecture firms to purchase them.

David Ogoli, assistant professor of architecture at Judson College, told EBN that the Model 126 is “a great teaching instrument that has generated a lot of interest among students and faculty.” Compared to other heliodons, Ogoli has found the Sun Emulator to be especially well made, attractive, and easy to use. Ogoli’s only complaint is that, due to the heliodon’s flat base, “large models have inaccurate readings at the extreme edges.” Limiting the scale of models will maintain accuracy, he noted, concluding: “Overall, the heliodon is an ‘A.’”

– JB

For more information:

High Precision Devices, Inc.
1668 Valtec Lane, Suite C
Boulder, CO 80301
303-447-2558, 303-447-2548 (fax)
www.hpd-online.com/heliodons.php

Norbert Lechner
119 Dudley Hall
Auburn University, AL 36849
334-844-5378
lechnnm@auburn.edu

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Heating, Cooling, Lighting: Design Methods for Architects, 2nd Edition EBN: From the Library - May 2001

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Books
	Heating, Cooling, Lighting: Design Methods for Architects, 3rd Edition by Norbert Lechner (2008)

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IMAGE CREDITS:
1. Source: High Precision Devices, Inc.

DISCUSSIONS There are no comments for this page yet. Log in to add comments RELATED ARTICLES Heating, Cooling, Lighting: Design Methods for Architects, 2nd Edition EBN: From the Library - May 2001 RELATED BIBLIOGRAPHY Heating, Cooling, Lighting : Design Methods for Architects, 3rd Edition by Norbert Lechner (2008) RELATED LEED CREDITS Minimum Energy Performance: Design & Construction EA Prerequisite 2 More related LEED credits RELATED GREEN DESIGN Solar Cooling Loads More related green design

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