Partly due to rising environmental concerns and the increasing cost of energy, the industrialized world is now replacing billions of conventional incandescent light fixtures. While a significant percentage of these applications are moving to compact fluorescent lamps (CFL), the concerns over the mercury content of the CFLs as well as the potential for even greater energy savings are causing more and more users to move to solid-state lighting. The observed lower than advertised lifetime of the CFL is also a concern. The newest light-emitting diode (LED) lights consume approximately 80% less energy than incandescent lamps and contain no toxic materials.

The PIL75U-C-DT series 75W LED driver from Power Partners has constant output current.
LED lamps and related hardware typically cost more than other current technologies. This goes for incandescent (lowest cost) as well as CFL (higher cost) technologies. In almost every business case, to justify the additional cost of the new lighting technology, the decision hinges on two key parameters of the product — improved energy savings and lower maintenance costs. There are two key components of the energy savings. The first is the resulting savings of the lighting technology alone, expressed in lumens/watts of power consumed to produce a known amount of light. This includes the power conversion efficiency of the power electronics, or LED driver, when taking the incoming AC power and eventually converting it to useful light. The second is the ability to change, or lower, the light output of the fixture based on the ambient light conditions.

As the ambient light increases — from the sun, for example — the need for additional light from the fixture can decrease. Keeping a light on full-power all the time may not be necessary, and is wasteful from an energy consumption standpoint. Conversely, in dark areas, there may be little light required to illuminate the object to be seen, thus requiring less light from the fixture under darker conditions. A good example of this is when the dashboard lights on a car are dimmed when the headlights are turned on. The cabin ambient light is considered lower if the headlights are required. Additional efficiencies — besides the pure power conversion efficiencies — can be had with some intelligent control over the lighting fixture based on its real-time environmental ambient lighting conditions. For the light fixture, this means some method of dimming the light output is required.

For maintenance cost considerations, again there are two factors — the lifetime specification of the fixture, and the cost to change the bulb in the fixture. For example, the 60-W bulb in a reading light costs almost nothing to change, but how about a street light? A licensed electrician with a bucket truck is required to change that bulb. So, while the maintenance cost of a reading light bulb change is next to nothing, the maintenance cost to change a streetlight can be $900. The driving force to solid-state lighting is the energy savings over other technologies. The maintenance costs are more of a factor with larger, higher-end fixtures as in street lights.

It has already been stated that solid-state lighting will yield approximately an 80% savings over incandescent technologies. So, how does reliability and lifetime affect the cost of solid-state lighting over incandescent? Solidstate lighting technology is currently performing at an average lifetime of 50k hours, or approximately five years of 100% usage. That means that each fixture will be expected to last five years if on 100% of the time. Many fixtures now are claiming ten year lifetimes. Street lights can often be found burned out or flickering. This is a critical safety area, and requires a licensed electrician with a bucket truck to change.

In conclusion, the energy savings, reliability, and lower maintenance costs all add up to the benefits of solid-state lighting. The negatives are really the initial cost or investment. For comparison, the typical solar energy installation takes about ten years to pay for itself. Solid-state lighting has an return on investment of much less than ten years, more likely six months to one year. Power Partners’ PIL series of LED driver power supplies are an integral part of the solid-state lighting solution. From 25 W to 300 W, efficiencies to 95% offer UL8750-approved power supplies for the next generation in lighting solutions.

Are we ready for the $30 solid-state lightbulb yet? Maybe not, but as prices drop for solidstate lighting devices, the general public will start to use them. The green movement, if you will, is not going away. It makes sense to save what natural resources we have while here on Earth. Power Partners' LED drivers coupled with state-of-the-art lighting engines are ready to be part of this revolution.

Lighting Technology Magazine

This article first appeared in the August, 2011 issue of Lighting Technology Magazine.

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