Clean Tech 101

Hybrid Solar Lighting - Reducing Energy Consumption of Interior Lighting


Image Credit: mr. teerapon tiuekhom/

Article updated on 12/02/2020 by Brett Smith

Developed in the mid-1990s by the Oak Ridge National Laboratory in Tennessee, hybrid solar lighting is a technology that collects sunlight and channels it to illuminate a building's interior using special fiber optics. Hybrid solar lighting offers an effective and sustainable approach to lowering energy consumption and provides benefits associated with the collection and usage of natural light.

The main goal of hybrid solar lighting is to reduce lighting costs, which can be as much as 20% of a building's overall power demand. In retail, there is a particularly high demand for lighting, with 55% to 70% of the overall power demand for a retail space typically being attributed to lighting. Much of this power demand is driven by popular tungsten-based display lights that are often used to boost sales of featured items.

Hybrid solar lighting is particularly useful in large constructions where skylights are not an option, as exterior light from windows does not penetrate far into the middle of large buildings. This kind of lighting system is becoming more popular due to lowering costs and the many benefits they provide, including lower energy usage and generation of waste heat. 
In addition to being more energy-efficient than compact fluorescent and incandescent lights, hybrid solar systems deliver essential visible light while blocking out undesirable infrared and ultraviolet light. 

How Does Hybrid Solar Lighting Work?

The solar collector is probably the most essential component of a hybrid solar lighting system. To gather sunlight throughout the day, the solar collector must track the sun as it moves across the sky. 

The sunlight collector is made up of a sizable parabolic principal mirror and a secondary mirror. The primary mirror is typically made from an aluminized plastic-based material, while the secondary mirror is usually made from borosilicate and features a dielectric surface coating that only reflects light in the visible part of the spectrum.

These mirrors are fabricated to focus the visible section of incoming solar radiation and channel this focused light into a collection of plastic optical fibers that lead down into the building. The system tracks the sun across the sky through the use of an algorithm based on the date, time, latitude and longitude.

In addition to the custom-made mirrors, every solar collector contains multiple other essential components such as optical filters, fiber optics, tracking controls, tracking hardware and mounting apparatuses for the mirrors.

Throughout the day, the mirrors send light down into fiber optic cables that are slightly thicker than standard fiber optics used for communication. The cables terminate at hybrid light fittings called luminaries. These fixtures are made to distribute light evenly and direct light as desired. Spot effects and other illumination effects can be created based on the arrangement of fibers.

The solar collector is typically mounted on top of pipes that pass from the roof of the building down into the interior. Ideally, the solar collector is located directly above the hybrid solar light fixtures. The light fixture includes a diffusing rod that distributes the incoming solar radiation. The lighting can be regulated via a conventional lighting control system.

Advantages of Hybrid Solar Lighting Systems

Hybrid solar lighting is not a relatively new idea. The idea of capturing the sun’s light and sending it down into a building had been tried in Japan in the 1970s, but that effort was limited by a lack of technology. 

The ORNL effort in the 90s was plagued by insufficient finances, and viability was only achieved after the US laboratory developed a system with light, cost-effective materials. For instance, the parabolic mirror developed by the ORNL was made from acrylic – a big improvement on the heavy glass mirror that had been used previously. Efficiency improvements over time led to enough energy savings to make a hybrid solar lighting system not only financially viable but superior to other commercial lighting systems in many respects. 

Besides energy savings, hybrid solar lighting systems generate little waste heat and produce fewer emissions than conventional lighting techniques by having a considerably lower energy demand. Recent developments in lighting technology have only made hybrid systems even more viable.

Hybrid solar lighting systems are designed to screen out light in the ultra-violet and infra-red areas of the electromagnetic spectrum. This incoming light can be used for space heating and water heating purposes. 

References and Further Reading

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