The incandescent light bulb has been with us for over a century.  It has served us well.  It is cheap to manufacture, uses readily available and benign materials, and gives off a pleasingly warm light.  The incandescent bulb’s biggest shortcoming is energy inefficiency in the visible spectrum.   However, that is not nearly as bad as some would make it out to be.  The rest of the energy that is not visible to us can help heat our homes in the colder months – which can be for most of the year in Northern climates.  Nevertheless, there has been a worldwide push to replace the incandescent bulb with something more energy efficient.  In the US, this push comes from a government mandate that, in effect, makes it illegal to sell incandescent bulbs of certain wattage ratings.  Over time, this mandate has been designed to broaden and encompass an ever-larger portion of the lighting product market. 

For the last decade or so, the only economically viable alternative to the incandescent bulb has been the CCFL.  While these “squiggly” tubes have been adopted by consumers to a limited degree, they do not produce as pleasing a light as traditional bulbs, are temperature sensitive, do not turn on to full brightness instantly, and often cannot be used in light fixtures that incorporate dimming capability.  Because of these performance limitations and the CCFLs higher cost, some consumers have decided to “stock-up” on incandescent bulbs, before they are taken off the market, instead of making the transition to the more efficient CCFL lamps.

Recently, this less-than-desirable transition process has taken a new direction toward a better alternative – one that will not require the force of a government edict to implement.  Over the last year or two, LEDs have evolved to become a strong competitor to CCFLs and are beginning to overwhelm the “squiggly” lamp technology.  LED lamps can now produce a light that is more pleasing, the brightness can be varied as desired, lifetimes are projected to be ten years or more, and costs are coming down to make them affordable for most consumers.  Thus, over the next few years, we can expect to see broad acceptance and implementation of LED technology for both commercial and residential applications. 

With this accelerating trend, life now gets quite interesting.   An LED normally operates with a voltage of approximately 3 volts.  For continuous operation, this voltage can be DC or for pulsed operation is can be just about any pulse width or waveform as long as the desired light output is achieved.  Since the turn-on characteristic of an LED is that of a forward-biased diode, once the threshold voltage is reached any additional voltage causes the current to increase exponentially.  Thus, for proper power management, the LED must be operated as a current-controlled device.  So how does all this match up with the currently available 110 volt AC that we find in every home and business in the USA and, with minor variations, in every home and business worldwide?   Obviously, not well. 

To make an LED plug-compatible with a 110 volt AC socket, each light “bulb” has to have its own power supply that converts the available AC voltage to something lower and reduces the reverse voltage to a safe level for the LEDs – typically connected in series or in series-parallel strings.  There also has to be circuitry to provide current control to keep the LEDs’ light emission at the desired level.  Thus, what we have ended up with is that each light “bulb” contains not only one or more LEDs as the light source but also comes complete with a power supply having many additional electronic components.  What a clumsy way to increase lighting efficiency!  

If we could go back about a hundred years and start all over again, we would perhaps think about this and develop a lighting system that provides voltages more compatible with what LEDs need.   However, with the existing 110 volt AC (or similar) so deeply imbedded in every home and business can such a change even be contemplated?  Or is there perhaps some hybrid solution?  Could we consider a combination of AC and DC power in each new home constructed?  What would it take to retrofit existing homes, schools, and businesses?

Alternating Current energy delivery with voltages in the 100 – 200 volt range has certainly proven its value for well over a century.  And it continues to be the best source of power for many electrical appliances, motors, and other devices.  It would thus appear that we could use a new approach predominantly for lighting.  Perhaps, the answer is to add a fourth wire to the typical three-wire system used currently in home and business wiring.  That would allow for the addition of a DC component in the range of perhaps 12 to 40 volts.  Then a central power supply could be added to the entry distribution panel that would still use the 220 volts AC typical in the US.   The result would be a significant reduction in the complexity of each LED light source with a consequential increase in reliability and reduction in cost. 

What would it take to make this happen?  Most likely it will take the push from another government mandate.  And to get such a mandate it will take many years.  It will require that a plethora of self interests be evaluated and resolved.  But perhaps with some patience and good technical guidance from the engineering community we could see such a change begin to take shape in the next two to three decades.  In the meantime, we will have to get by with the less desirable solution of power supplies built into each light “bulb” – with the consequences of higher cost and lower reliability.

Have you started the conversion process to LED lighting in a serious way in your home or business yet?   We are still in the early stages but the process is accelerating.  I would be interested to hear from you if you think there is a different or more fundamental change in the wind in how we will power the lighting of our homes and businesses in the future.  You may reach me directly from this site, by e-mail at silzars@attglobal.net, or by telephone at 425-898-9117.