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Cool Light on Hot Days: Fiber Optics Bring the Sun Indoors

B. THE COST-DISTANCE TRADE-OFF

by Mary-Sue Haliburton
Pure Energy Systems News
Copyright © 2005

It’s hard to think of a downside to fully natural indoor daylight – without heat or sunburn-causing UV – that doesn’t even need to use electricity.

At present there are a couple of significant shortcomings to this promising technology: the price, and the distance limit. Though cost-effective, currently-available plastic optical fibers impose a limit on transmission distance of thirty to fifty feet. Thus the benefit of optical lighting could not go beyond the one or two top floors of office buildings. At present, therefore, one- and two-storey, flat-roofed retail commercial structures are seen as having the most to gain from hybrid lighting. And there are many such buildings in every city and town.

The HSL 3000 is scheduled for release early in 2007, and is initially priced at about $8,000 USD. Even at this price the savings in energy costs are expected to offset the purchase price over time. And this price is expected come down in the usual way, as volume of sales goes up.

Though skylights are a valid option for building owners, in some cases the architecture may not permit these to be added later. Water tanks or other structures on the roof may interfere with placing the opening in the most desirable or useful location. Citing research showing that sales increase by up to forty percent in stores with natural light from skylights, Sunlight Direct’s founders believe that retailers would indeed gain more than just the saving in electricity costs from installing fiber-optic collectors. Infra-red blocking skylights are not cheap either, and entail risks such as leaks or breakage. Optical-fiber lighting offers greater flexibility of location, and ease of moving the light fixtures, should the office be rearranged.


Optical Fiber Research Continues

Dr. Earl forecasts that ongoing research on the plastic fibers will increase the carrying distance of visible light by 300%. Equipped with these hypothetical new fibers, therefore, as many as six top floors of an office or other tall building could be served with direct natural light from roof installations. Using the more pricey but longer-range glass optical fibers, this distance is already possible. However, because glass fibers cost more and are difficult to work with, using them would likely limit the market to companies with very deep pockets, or to politically- or militarily-strategic windowless or underground establishments.


Beta Testing

Beta testing of this hybrid unit was opened up as of June 2005. It should be noted that participating in official testing is expensive and involves data collection. Any interested organizations or businesses able to handle the cost, data collection and follow-up reporting are invited to examine the beta-test agreement at Sunlight Direct’s website. (Ref)


Architectural Integration

Depending on the design and orientation of a building, and the height and location of any surrounding structures, by mounting additional solar collectors on the outside walls of an office or condominium tower, it might be possible to extend hours of effective lighting to more lower floors. . For example, solar collectors might be placed at a south corner, on every floor or every second floor depending on size. From that corner they can track the sun as it moves from SE through South to SW, which would cover the hottest part of the day and until late afternoon when most people leave for the day. And on an office tower of which the SW corner is shaded by another building, morning to mid-afternoon exposure could be captured from an SE corner.

On a residential building solar collector units might be mounted at a south-west corner to take advantage of noon to evening light. Or in a condominium building, early-rising residents might choose to have either first half of the day from a SE placement, and late risers might choose the afternoon sunlight feed. Though windows are normally provided for living-rooms, in very few buildings have the architects provided a window for the kitchen, where natural light would be appreciated for breakfast or supper preparation.

In the future, we might even see buildings designed specifically with more un-shaded roof areas at different heights to make the best use of fiber-optic indoor lighting. The area served by a single HSL 3000 is about 1000 square feet. Though many small and mid-sized homes would get by with a single collector, more units would be needed on large buildings. At current pricing, this combined cost might cause many buyers to hesitate. However, as more capability, greater carrying distance, more options (see part C) and lower costs come together, the benefits may outweigh the costs.


Hybrid Systems vs. Manual Control

People already notice when outside light is diminishing and routinely turn on artificial lights as required, or for romantic purposes someone might want to let the light die down naturally. Fluorescent-hybrid lighting is not as necessary or affordable for homes or apartments. Eliminating the more complex circuitry and automatic artificial-light-intensity sensors and controllers should lower the price somewhat. A simple fiber-optic light system would suffice for a budget-conscious homeowner.

On the products page of Sun-Direct’s website, a simplified version of the solar light collector, without sensors and automatic level adjustments, is represented as suitable only for research. When asked whether the company might consider offering a simplified optical-fiber lighting setup such as this for households, Dr. Earl mentioned that it’s not only homeowners who are interested in a manually-controlled version, and not merely for financial reasons.

Some commercial building occupants have indicated a preference for a non-automatic system. These people prefer natural light that blends with the quality of light outdoors whether it is overcast or bright. “It gives a connection to the outside environment that is very pleasing,” Dr. Earl comments. “I think a simplified, lower-cost system makes a lot of sense, and would be possible.”


White LED Hybrid Lighting

One other option is being considered. Numerous homeowners have contacted Sunlight Direct to propose that fiber optics be hybridized with white LED lighting. These LEDs are being widely touted for their long life, very low power need (one half to one watt), and non-toxicity. Unlike incandescent vacuum bulbs which are illuminated by a tungsten filament made white-hot by the electrical current, all fluorescents – “full spectrum” or not – contain mercury vapour which is essential to create the glow. When a tube is broken, this mercury escapes into the room. For the same fifteen to twenty-three watts needed for one “energy-saving” fluorescent screw-in spiral light, several LED fixtures could operate day and night on energy collected by a small solar panel.

Although a single LED is small, a Fresnel lens can spread its light outward. Or several LEDs can be mounted in the same fixture, angled in different directions for more diffused lighting. Again, as long as the power comes from the sun, the LEDs need not be automatically controlled in co-ordination with the daily sunlight cycle. Instead, people will want to have a choice of either always-on hallway and bathroom lights, or track lighting and other fixtures that are switched for manual control – or perhaps some of each. All LED fixtures should be designed so that more can be wired in as new requirements arise.

Sunlight Direct has proposed another joint project to Oak Ridge Laboratories to develop a hybrid system with white LEDs. If funding is approved, this will be underway later in 2005. Even if a homeowner does not opt for fiber-optic collector at this time, being able to install white-LED fixtures wired to a solar panel would be a welcome interim choice. It would be ideal if such off-grid lighting linked to a solar panel were designed to be integrated with the fiber-optic light at a later date when the price comes down.


Installation and Fire Safety

The company originally planned to offer units with do-it-yourself installation, expecting the price to be initially about $5000. Those who are technically adept would not blink an eye at this, but some less-than-handy homeowners are likely to hesitate. Given that the visual light from even one fiber is capable of boiling water, there might be a fire hazard from broken fibers if the work is incorrectly or carelessly done, or if a later home renovator were to cut across the installed fibers. This risk would be expected to be more serious once connecting IR fibers to a water-heating system is involved.

Even if homeowners were to install this system “at own risk”, the company’s reputation would still be affected if the system does not function as it should due to errors made by incompetent installers (either oneself or others). Further, litigation would inevitably arise if fires were to occur. In answer to a question about providing instructions and perhaps certification courses to train technicians in the proper handling of Sunlight Direct products, Dr. Earl said that the future Canadian partners would be responsible for installations. Similar arrangements are being negotiated with American companies as well.

Although Sunlight Direct has not specified the cost of installation – other than to imply that it would involve extra money you would not be paying if doing it yourself – having professionals do the work would obviously add to the price of the system. Basing a rough guess on the rates charged by other professional trades, this could amount to an additional $1000 or more, depending on the size of the house and the number of areas to be lighted. But the safety factor may make this worth the extra cost.

Rather than installation cost, it is the fire-safety issue that is delaying release of the home systems until 2008.

“Our biggest concern about the residential systems is that [they need] to be installed properly to ensure safe and optimal operation (or at least this is true given the current HSL design). We are trying to modify the current design to actually eliminate some of these concerns by having inherent safety features built in.” (Ref.)

These changes include modifying the mirror so that it focuses sunlight only when aligned to the sun within five degrees, avoiding excess concentration of heat. It is not clear why five degrees would be significant. Enclosing the vulnerable fibers in a fireproof conduit might be more to the point. The company’s researchers are also working on a “breaker” that would automatically stop the sunlight from being brought in if an optical fiber were to be broken. If it can be reliably implemented, an automatic breaker would be a worthwhile fail-safe against inadvertent damage to the fiber-optic lines.


Functionality vs. Aesthetics Trade-Off

Other issues may arise as homeowners consider whether to invest in fiber optic lighting. The presence of shade trees tall enough to overhang the roof can block reception of light in the mirrors. Dr. Earl agrees that trees are a valuable addition to landscaping, and strongly endorses their environmental contribution of restoring oxygen to the air and preventing heat buildup in the home receiving this natural shade.

However, he emphasizes that although a mounting system can be devised to place the collector at the peak of the roof and up to six feet above it, some landscaping changes may be essential. For example, nearby trees may have to be pruned, preferably by a competent arborist. Also, it would be necessary to calculate the angle of the sun, as the length of the cast shadow will increase later in the fall and winter when the sun is lower in the sky. In the case of deciduous trees, this factor is less important since in most of Canada and the northern states, this type of tree sheds its foliage by the end of October or early November, and the thin upper twigs won’t cast significant shadows. For several weeks before and after the winter solstice, the sun is too low in the sky to provide much energy anyway.

Some homeowners may not like the utilitarian look of the mirror on the roof, though most people don’t worry about the appearance of satellite TV receivers. Dr. Earl says that about 50% of people are very worried about how something looks, and the other half of the population doesn’t care at all. Sunlight Direct is considering various sculptural modifications of their product to appeal to the esthetes in the market. Presumably, solar collectors could be created with decorative themes like those used for weathervanes, or in abstract shapes. Designer solar collectors could even be licensed to third-party companies, and marketed to high-end consumers and social climbers.

However, fussing over the look of the system seems frivolous. Personally speaking, I would not care to spend extra to have anything other than the bottom-line scientific hardware on the roof. Others have water-pipe arrays and satellite dishes, so why not a bare-bones sunlight collector? If fortunate enough to be able to afford solar direct lighting, why would anyone hide the energy-saving technology? At least some environmentalists might consider it a badge of honour to display a sunlight-collector mirror – alongside their solar panel and perhaps a home-made windmill.

Everyone will be better off if even ten percent of homes and commercial buildings are outfitted with HSL systems, due to relieving stress on the grid at peak times. As the quality of optical fibers improves, and unit costs come down, we should expect to see wider adoption of non-electrical sunlight systems.

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Page posted by SDA July 26, 2005
Last updated July 27, 2005