Help the Planet: What is Hybrid Solar Lighting?

Posted by RealEstateRama

May 14, 2008

Hybrid solar lighting (HSL) technology – a technology capable of collecting sunlight and distributing it, via optical fibers, into the interior of a building. This technology provides an exciting new means of reducing energy consumption while also delivering significant ancillary benefits associated with natural lighting in commercial buildings. Hybrid solar lighting has the potential to significantly reduce energy consumption for retailers while also maintaining, or exceeding, the lighting quality requirements of a retail environment.

Traditional solar panels are able to utilize approximately 15% of the sunlight they receive, and standard light bulbs lose the bulk of their energy in the form of heat — the end result is a total efficiency of about 2% of the original sunlight. By contrast, hybrid solar lighting systems are able to utilize as much as 50% of the original sunlight.

One of the major components of a hybrid solar lighting system is the sunlight collector. The sunlight collector consists of a large parabolic primary mirror and a segmented secondary mirror designed to focus the visible portion of sunlight into a bundle of plastic optical fibers. In addition to the mirrors, each collector includes two-axis tracking hardware, electronic tracking controls, optical filters, and mounting hardware for the mirrors and optical fibers. Each collector is mounted on a 4 inch schedule 40 pipe that penetrates the building roof, secured to the substructure, and is preferably centered above the 8 to 10 light fixtures to which it supplies light. Each light fixture consists of a traditional 2×4 foot light fixture containing 4 fluorescent lamps. The fixture is slightly modified to accommodate a sunlight diffusing rod (as shown in previous figure) that spatially distributes the sunlight similar to co-located electric lamps. A custom-designed control system and conventional electronic dimming ballasts are used to regulate the electric lights and reduce the electric lighting load. Each system covers approximately 1000 sq. ft. and is expected to displace approximately 2 kW of electric lighting. In addition to the energy savings, hybrid lighting offers other value propositions such as the potential of improved lighting quality and worker productivity, visual connection with the outside world, and the future possibility of increased sales. It will also reduce the roof penetration from 1250 to 50 linear feet and virtually eliminate additional HVAC loads attributable to skylights.

In commercial buildings, lighting consumes more electric energy than any other building end-use. Lighting one and two story buildings accounts for more than a quarter of all electricity consumed for commercial use in the United States. Typically, less than 25% of that energy actually produces light; the rest generates heat that increased the need for air-conditioning. Unlike conventional electric lamps, HSL systems produce little waste heat. Using sunlight directly avoid the conversion less of energy to illumination with the associated waste heat generation.

HSL delivers the benefits of natural lighting without the disadvantages of conventional daylighting technologies (such as windows or skylights). Although skylights have been around for many decades and function as a simple means of bringing natural light into a building, they can have a number of drawbacks that can limit their application. These can include:

- Significant source of heat loss or heat gain
- Can constrain design of building shape and orientation
- Difficult\Complicated to specify
- Point of condensation
- Uncontrolled, uneven illumination
- Susceptible to water leakage
- Susceptible to ventilation leakage
- Not appropriate for low ceilings
- Difficult to relocate or reconfigure
- Suitable for downlighting only (i.e. N/A to directional lighting or uplighting)
- Does not maximize the use of available sunlight
- A source of light pollution at night
- Cannot be easily turned off
- Security concerns

Hybrid Solar Lighting delivers natural light into a building interior without any of the above mentioned disadvantages. Independent cost and performance models suggest the overall affordability of solar energy could be doubled or tripled using this new hybrid approach.

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