California Lighting Technology Center - Solatube Product Development

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Solatube Product Development

Tubular Daylighting Devices (TDDs) capture light through a dome on a building's rooftop and channel the light into the building through a reflective tube, effectively bringing daylight into the building's interior spaces. Today's commercially available TDD products are so effective that the amount of daylight reaching the diffuser can create visual discomfort, called "discomfort glare" or "glare."

For this project, CLTC researchers partnered with TDD manufacturer Solatube International Inc. to develop a reduced-glare, direct/indirect diffuser option for TDDs. CLTC's role in the project included the following tasks:

Measured and analyzed the performance of current Solatube TDDs that use direct diffusers
Discussed desired performance characteristics and criteria for improved direct/indirect diffuser options
Developed and tested a procedure for simulating proposed diffuser designs using HDR imaging and ray-tracing software
Measured and evaluated Solatube prototypes
Recommended further development and testing of the most promising new diffuser design


Solatube TDD brings light into an office		Solatube diffuser

Solatube TDD dome on a roof		Several Solatubes on building's roof

Objectives / Goals:

Develop conceptual, commercially available, direct/indirect TDD diffuser options for detailed photometric analysis
Produce two or three commercially viable diffuser options for prototyping, physical testing, and evaluation using performance criteria established by the project team and advisory committee
Develop one commercially viable product solution and perform detailed photometric testing and analysis to develop the photometric data required to support and launch the diffuser option to the general public
Produce design guidelines to support the application and use, by architecture and lighting design practitioners, of the new, commercially viable diffuser option

Results: The new Solatube prototype diffuser represents a step toward meeting the project design specifications, but it still produces glare. Tests of the prototype revealed visual performance that exceeded the desired glare constraints of the project. However, with continued refinement of the early prototype designs, these issues easily could be addressed.

The inherent variability in light direction and intensity makes consistent optical control of daylight difficult and requires complex optical design and components. Solatube attempted to address these design issues by exploring changes in the TDD light engine collection and transportation, and enhanced optical diffuser technologies. Several diffuser designs were produced for physical evaluation. While the technology is promising, the project's timeframe did not allow for the significant evolution required to bring products to market.

Status: At the conclusion to this project, Solatube developed direct/indirect diffuser designs that have commercialization potential, but further refinement is needed to develop products suitable for widespread application. While true direct/indirect diffusers have not been commercially produced, other advancements developed during this project were successfully launched and commercialized in 2008.

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Project Resources

For more information on this technology, please view the following documents:

Solatube Technical Brief (PDF)

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