Fiber Optics for Daylighting
Interior Lighting: Fiber Optic Daylighting w/Daylight Harvesting Controls vs. Fluorescent Lighting Without Controls
Use of fiber optic cables to convey daylight into a building's interior from sun-tracking rooftop collectors that use parabolic mirrors or Fresnel lenses.
Synopsis:
Fiber optic daylighting systems include a collector, reflectors, filters, lenses to direct light to the fiber optic cables and a fixture to distribute the light. The daylight is gathered and concentrated by collectors using parabolic mirrors or Fresnel lenses that track the sun as it moves through the sky. UV and IR light is filtered as the visible light is collected and transmitted into the building. The system may provide stand-alone daytime lighting or be part of a hybrid solar lighting system that is integrated with electric lighting and controls to make the same fixtures usable at times of low or no daylight.
A separate but related technology is remote source lighting, which also includes light pipes. Unlike direct skylights, they do not transmit heat or UV radiation. How far the light can be transported depends on the quality of the materials used and the wavelength of the light transmitted. Some early failures were due to thermal impacts, but new, efficient systems are operating at 65% to 75% of their theoretical limit, depending on the mirror efficiencies at a specific location.
Costs have suppressed adoption of this technology in the United States compared to some Asian and European locations, and the main providers of this technology are from those regions. As energy costs increase, this may be a more attractive system, but at the same time, the use of occupancy sensors and emergency of LED lighting technologies have greatly reduced lighting energy costs and the potential energy savings that can be obtained by fiber optic daylighting approaches. Simpler daylighting approaches include re-directing window films and use of a tubular skylight with a prismatic diffuser at the end of a short light pipe. The skylight is effective for low buildings with a large footprint such as warehouses, workshops, and retail spaces. A thermal break is provided to prevent condensation and thermal losses.
Energy Savings: 70%
Energy Savings Rating: Not rated.
What's this?
| Level | Status | Description |
| 1 | Concept not validated | Claims of energy savings may not be credible due to lack of documentation or validation by unbiased experts. |
| 2 | Concept validated: | An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles. |
| 3 | Limited assessment | An unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline. |
| 4 | Extensive assessment | Additional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions. |
| 5 | Comprehensive analysis | Results of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications. |
| 6 | Approved measure | Protocols for technology application are established and approved. |
Simple Payback, New Construction (years): 117.5
What's this?
Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:
Simple Payback = Incremental First Cost / Annual Savings
The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.
For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.
For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.
Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.
The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.