30 May 2006

Energy Conservation

Energy production is centralized and engineers have made power plants very efficient. There is only so much more that can be squeezed out of that part of the larger power system. Energy conservation, in contrast, has considerable room for improvement.

Consider the question of household and commercial lighting (paid registration may be required):

In the United States, for instance, $55 billion worth of electricity—some 22 percent of the nation's total—goes annually to light homes and businesses. That sum is roughly equivalent to the output of 100 large power plants. Pollution associated with the energy needed for lighting is also large: Annually, about 450 million tons of carbon dioxide and 3 million tons of smog-generating nitrogen oxides and sulfur dioxide.


Step one is converting from high wattage conventional bulbs to lower wattage alternatives. The flourescent bulb in my office, for example, draws 26 watts and provides the same level of illumination as a 100 watt conventional bulb.

Incandescent bulbs, including halogen types, are energy hogs: Typically emitting as light only 5 percent of the energy they use, they convert the rest to heat. Because incandescent bulbs are cheap, their light can seem less expensive than a fluorescent tube's. However, incandescents put out only 15 to 20 lumens per watt, less than one-quarter the output of fluorescent tubes. And an incandescent lasts only about 750 hours, some 8 percent of the typical fluorescent tube's life.


Organic and non-organic LEDs (light emitting diodes) are another story. Currently they are a niche application. Traffic lights and automobile tail lights are two of the biggest uses. But, they have great potential.

LEDs are already in the efficiency range of fluorescent tubes, and researchers predict that they'll ultimately deliver about 150 lumens per watt in commercial applications throughout a projected lifetime of at least 70,000 hours. Smaller than a fingernail, these solid-state devices directly convert about 20 percent of the incoming electrical energy to light. They dissipate the rest as heat, although they don't become hot to the touch.


Let's review:

Incandesent Lights 750 hours, 15-20 lumens per watt
Flourescent lights 6,000 hours, 60-80 lumens per watt
LEDs 70,000 hours, 150 lumens per watt (projected potential)

OLEDs can be made to be flexible, and LEDs work well with task lighting that lights only the area where you need light, rather than an entire room, and are well suited to low voltage, off the grid applications.

Another development uses fiber optic fibers to deliver outside sunlight to interior spaces, with each fiber carrying the equivalent of a 30 watt incandescent bulb of sunlight.

The bottom line is the new lighting technologies, most of which are actually cheaper in total non-energy costs than conventional systems as well, could reduce U.S. demand for electricity by the equivalent of 80-90 power plants worth.

This isn't the only area where major gains can be secured with energy conservation. In dry climates, favoring evaporative coolers over conventional air conditioning can save an immense amount of electricity. Improved building insulation cuts both air conditioning costs and heating costs. One area window installer was willing to guarantee in writing that my home heating costs would fall 50% in the first year after they were installed, if I replaced my single pane, metal framed windows with their product. Improved clothing washers, dishwashers and more efficient water heating systems of various kinds all reduce water heating costs. And, of course, more fuel efficient choices of commuting vehicles can have an immense impact.

Certainly, there is room for improvement on the supply side of energy policy, as well as the demand side. But, while we are increasingly seeing diminishing returns in new oil exploration efforts, as the easier to exploit reservoirs are depleted (oil shale, one commonly discussed exploration alternative has less energy per volume than breakfast cereal), conservation gains look like a more promising focus for our policy efforts.

2 comments:

Jon W. said...

While there are economic and environmental reasons to prefer fluorescent to incandescent, a lot of people (myself included) prefer the light from the latter, especially halogens. Also, keep in mind that frequent on/off cycles can lower the expected life of a fluorescent bulb.

Andrew Oh-Willeke said...

True enough. This is one of the big attractions of LEDs. LEDs are particularly desirable in applications like stop lights because they handle the on/off cycle so well. And, I think the quality of the light that they produce is better than flourescent.