Monday, April 26, 2010

Saving Energy in Residential Lighting: The Other Half of the Story

What is the best way to reduce the amount of electrical energy used for residential lighting? The answer is to use more efficient light sources so the light can be provided with fewer watts.

A 100 watt incandescent household bulb rated for 1,700 lumens, for example, can be replaced by a 29 watt compact fluorescent lamp (CFL) rated for the same 1,700 lumens for an energy savings of 71percent, assuming that both are burned for the same number of hours.

ENERGY = (Power) x (Time)
Reducing the power draw (watts) of a luminaire by 50 percent certainly reduces the energy used by that luminaire by 50 percent; but so does leaving the power the same and reducing the operating time by 50 percent instead.

Why, then, are lighting regulations so focused on the "Power" part of the equation rather than the "Time" part? The answer is that, so far, it is relatively easy to do, and we have not figured out a way to control - or even reliably estimate - how long a luminaire is turned on every day.

We've also been fortunate that lamp manufacturers have been able to develop ever more efficient lamps - CFLs and, now, LEDs - which can replace less-efficient incandescent bulbs.

There's also the question of certification and verification. If an electric utility is paid by regulators for reducing lighting energy use, how does that utility prove its claims?

Utilities do that now by counting the CFLs or other energy-efficient products that their customers put into service via a rebate or incentive process.

One way a portable luminaire can be certified to be energy efficient is by inspection - simply look to see if the portable luminaire has a GU-24 socket.

In California, GU-24 sockets are designated for use only with energy-efficient CFL and LED lamps. Adapters which convert the GU-24 socket to accept another type of lamp base are illegal.

New Generation of Lighting Controls
However, suppose that we could verify that a luminaire was operated for a given length of time. We know the rated wattage of the luminaire, and if we also know the time, we would know the energy used. That's the concept behind a new generation of lighting controls. Not only can they control the lighting, but they are also smart enough to know which luminaires are on and for how long.

The idea is being experimentally applied now to roadway lighting. Each luminaire is equipped with a "smart chip" and assigned an Internet address so a computer control can switch the luminaire, change its output, query the luminaire to find out if it is on or off, monitor energy use, track lamp burning hours for maintenance purposes and even report a lamp failure should the luminaire be switched on but not draw power.

Would the idea benefit the residential lighting industry? It might offer alternatives to the ever-more-stringent regulations being applied to lamps and luminaires. For example, energy savings due to dimming could be quantified since a "smart" luminaire could report the actual power draw of a dimmed lamp.

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