On the Horizon and Here Today: LED Alternatives to Linear Fluorescents

March 6, 2008 in Cool Stuff, Ecology News

By Glenn Hasek

 03/04/2008

 

 A cut-away of a lamp from ilumisys

 NATIONAL REPORT—In meeting rooms, back of house and other areas of your hotel, chances are great that you are using T-12 fluorescent lamps or the more efficient T-8s to illuminate large spaces. At least two companies—ilumisys, Inc. in Troy, Mich., and LEDdynamics, Inc. in Randolph, Vt.—are trying to replace these linear fluorescents with LED alternatives that are more energy efficient and safer for the environment. Fluorescent tubes include mercury and despite recycling efforts, 500 million to 600 million lamps end up in landfills each year. LED alternatives do not include mercury.“LED lamps also last longer, which means you throw away less waste,” says Dave Simon, president of ilumisys. “They are, on average, 10 percent more efficient, are dimmable, and can interface with smart building and HVAC systems.”

While not significantly more energy efficient than their fluorescent counterparts today, linear LED lamps are expected to be three times more efficient in the next five years. They currently cost more than fluorescents but once labor and waste reduction is factored in, they begin to make sense, especially for high locations that are difficult to access.

Simon’s company has installed its new products in batches of hundreds at several pilot sites. The LED lamps are “drop in” replacements for fluorescents and are compatible with standard, ballast-equipped fluorescent light fixtures. Similarly, lamps produced by LEDdynamics are also compatible with standard fixtures.

LED Light is More Direct

Linear LED lamps perform somewhat differently than their fluorescent counterparts in that they produce a directed, rather than a disbursed light.

“They need to be aimed properly,” Simon says. “Color temperature options can vary from very warm to classic harsh blue light. LEDs don’t put out radiant light. They produce less heat than fluorescents. The heat that is generated is produced through the connection to the circuit board. The more light per watt, the less heat that is generated.”

So far, ilumisys has primarily been generating 48-inch lamps as replacements for T-8s and T-12s. LEDdynamics is also producing 48-inch lamps. The lamps are recyclable, flicker free and can last 10 years.

Late last year, ilumisys was presented with the Michigan Economic Development Corp.’s first award for outstanding diversification achievement in alternative energy companies. The company was selected as the small business winner. Also last year, LEDdynamics received the Popular Science “Best of 2007 Innovation Award”—in the Green Tech category—for the EverLED-TR product line.

According to the U.S. Department of Energy, energy consumption for lighting could be reduced by more than 20 percent by 2020 through the use of solid state LED-based lighting.

Go to ilumisys and LEDdynamics.

Glenn Hasek can be reached at editor@greenlodgingnews.com.

THE DOUBLE-ENVELOPE HOUSE

February 26, 2008 in Architecture News, Cool Stuff, Ecology News

Mother Earth News Original Article                                                                                  

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Few new housing designs have drawn as much attention—or caused as much controversy—as has the double envelope. Pioneered in 1977 by Lee Porter Butler and Tom Smith in a house near Lake Tahoe, California (see

MOTHER NO. 56, page 120), the two-shell concept has gained an enthusiastic following. At the same time, however, the theory behind the thermal envelope has created a stir among solar designers.

When the Smith house was built, the dynamics of its performance were completely theoretical. No one had carefully instrumented such a building, and—accordingly—many architects and engineers reserved their acclaim . . . pending the availability of data on the efficiency of distribution and storage of the solar heat taken in through the home’s large south facing glass area.

Today there are hundreds of double envelope houses around the country, and the performance of the concept has been well documented. Very few experts now question the fact that thermal-envelope buildings are quite efficient … but the quibbling over why they work and about how well they compare with other passive designs, continues.

A REVIEW OF THE THEORY

The “collector” system for a thermal envelope house is a heat-producing sun space (which can, in many climates, double as a year-round greenhouse). It’s the method by which the sun space is incorporated into the structure’s heating system that sets this sort of dwelling apart from other solar-heated houses.

As the term “double envelope” implies, such a building is actually a house within a house. The exterior shell is load-bearing, and generally has a minimum of R-19 insulation. Between the outer and inner skins lies an air space (usually at least a foot wide) which extends from the east to the west end of the house along the roof line and the north wall. The inner wall is generally thinner—since the small temperature difference between the building’s interior and the air space requires less insulation—and supports only the structure of the living space. The passageway between the two walls is linked to the greenhouse by a crawl space or basement, which feeds air up through gaps in the boards of the solarium floor

The circulation of air through the envelope is entirely passive. The system takes advantage of the fact that warm air is less dense (and therefore more buoyant, since gravity’s influence is reduced) than is cold air. Sun-heated currents rise in the greenhouse and enter the envelope at the room’s peak … while the air between the shells—and particularly that along the north wall—loses heat and falls. The solar-heated air is then pulled through the passageway and the subfloor area, and returns to the sun space from below

Furthermore, as the air passes through the subfloor area, some of the heat it still holds is absorbed by the surrounding earth, rock, and/or masonry. These massive materials take in and store the warmth as long as they’re cooler than the circulating air. During the evening, however, the storage temperature may actually exceed that of the circulating air … which causes the thermal mass to give up heat.

A double envelope also taps its storage passively by reversing the convective loop. During the night the structure’s greatest heat loss is through the expanse of glass in the sun space. That cooling causes air to fall to the floor of the greenhouse, while the (relatively) warmer air of the storage area rises and is forced up the north wall cavity. The continual imbalance in pressure then keeps the loop flowing.

In the summertime, however, the sun space is likely to gain far too much solar energy . . . despite the fact that the tilted glass is oriented to admit winter—but not summer—sun. To prevent overheating, vents are usually set into the roof peak of an envelope house, allowing the rising hot air to escape. And in some designs, “cool pipes” (air intake tubes buried in the ground . . . see the article on page 128 for a fuller explanation of this system) are linked to the crawl space so that earth temperature air can be drawn in and distributed through the envelope.

The energy-saving capabilities of the envelope design are numerous. For one thing, a great deal of solar heat is taken in through the greenhouse, and at least some excess warmth is stored in the crawl space for use during the night or on cloudy days. Consequently, most double envelope houses require very little backup heat. In fact, they often satisfy 80% (or more) of their thermal needs directly from the sun.

Now there’s no question that a large part of the energy efficiency of such structures does result from their thick insulation. The two shells and large air gap produce a total R-value that typically exceeds 30! In addition, the double walls reduce infiltration (direct air leakage) to the living space and dramatically improve the thermal resistance of any north-facing windows … because of the roughly 12″-wide air space. (In fact, that gap can, in effect, increase window Rvalue by as much as 4 . . . without producing the condensation that tends to be a problem in conventional multipane windows.)

Another thermal benefit of the envelope concept shows up in the form of comfort. Because the air circulating inside the envelope is significantly warmer than that outdoors, the difference in temperature (or At, in heating engineers’ lingo) between the living area and the air passage is relatively small. Thus the heat loss for the inner wall is less than that of an equivalent insulative fraction of a single wall whose total Rvalue equals the double envelope’s. As a result, the surfaces of the envelope’s interior walls remain warmer than would equally insulated single-layer walls.

Envelope home residents also enjoy pleasantly stable humidity through the winter, since moist greenhouse atmosphere is continually circulated through the air space and can be admitted to the living quarters by cracking a door or window. (In the summer, however, excess humidity—and heat—is vented at the sunspace peak.) Furthermore, the constant but gentle and silent circulation of air prevents stagnation and lends a balmy feeling to the interior environment.

Article continues here