Climate Change Economics - More on efficiency

Energy efficiency improvements we have been talking about involve swapping existing methods or technology for other methods or technology that provide the same service with less energy. For example, there are many alternatives to the old incandescent "lightbulb".

One of our commenters pointed out that the 20 watt CFL is not directly interchangable with a 100 watt incandescent lamp. The example was intended to show the economic advantages of an "equivalent" exchange, not necessarily to illustrate a recommended change.

There will be a whole separate series of posts on high efficiency lighting. However, for now it suffices to say that there are many applications where a fluorescent lighting fixture can be used as effectively as a higher wattage incandescent. That is because the basic measure of efficiency in a lamp, lumens per watt, is significantly higher for fluorescents.

An electric lamp can be thought of as an energy converter, converting electric energy to light energy, measured in lumens. In an incandescent, which works by heating a filament, up to 80% or more of the energy consumed by the lamp is converted to heat instead of light. A fluorescent fixture converts much more of the energy it consumes to light. Therefore, the number of lumens (amount of light output) emitted by a fluorescent is much higher than an incandescent per unit of electricity consumed.

Fluorescent lamps and fixtures (luminaires) have developed tremendously even in just the past few years. They are available in many sizes and shapes, light outputs and color temperatures (quality of light). The "flicker" and hum of the old fluorescents is gone. Today, a buyer would be hard-pressed to find an application for which a suitable fluorescent could not be found. However, certain applications require more focus or intensity or smaller size than fluorescents can provide.

In these cases, halogen lamps and fixtures are the next most efficient choice. Although they are incandescent, they have a higher lumen per watt rating than the standard incandescent light bulb. They are particularly well suited for focused, spotlight or small area illumination. They can also be run on low voltage DC, which is the native output of solar photovoltaic systems. This allows them to be designed into a home, along with solar photovoltaics, to provide off-grid lighting.