Scientific Seen

News, Commentary, and Tutorials from a Scientific Perspective

From the day I began working as a science writer (starting as a “hobby” while I was a gainfully employed optical systems research engineer) I’ve covered new breakthroughs — discoveries or inventions that have revealed or used new principles or techniques. The challenge of covering that “beat” is that the mere fact that a discovery or invention has been made says absolutely nothing about the use or application of the advance. So there’s a bit of a disconnect between news of technological or scientific progress and the availability of the fruits of that progress to a wider community. But there is a definite process that these things tend to follow: initial work–>use by a handful of specialized practitioners–>availability of the method to a technically capable general population–>accessibility to all. Of course, not all breakthroughs make it through all these stages, and one of the most fascinating aspects of following science and technology is to predict which ones will hit the big time.
Applying that model to the development of general lighting with LEDs, the first breakthrough was simply crashing through the performance, cost, and reliability (i.e., quality assurance and product validation) barriers to bring solid state lighting to market. Any walk through a big box hardware store will demonstrate that basic LED technology is now in the fourth stage of development.

Controls Adding Value

The subsequent stage is to realize even more value from LED lighting by incorporating it into an overall control system, i.e., Smart Lighting. I’d say that’s at the third stage (perhaps on the cusp of the fourth), where folks who are generally capable around technology can now incorporate advanced controls into their lighting systems. Proving the point are commercially available systems such as the Hue system from Philips bringing those capabilities to the general consumer, and companies like Redwood Systems, that offer integrated controls solutions to commercial and industrial customers.

Image of LED lights controlled by smartphone app.

Philips’ Hue system brings LED lighting control within grasp of the tech savvy. (Courtesy of Philips Communications)

Although the market penetration for LED lighting in general is still proportionally very small compared to the overall industry, that’s now a marketing challenge more than a technical one. The next wave in LED lighting is to start to apply the inherent controllability of solid state lighting to use light to define spaces and optimize suitability of illumination for any circumstance. Specifically, LEDs offer an unprecedented degree of control over the distribution, spectrum, and intensity of light in a space — including the ability to vary those parameters over time.
At the Strategies in Light Conference, Hans Nikol, VP for Strategy and Innovation at Philips Lighting, discussed how a significant percentage of the market for the Hue LED lighting system is driven by teenagers — looking to show off the cool lighting at their homespun raves (if anyone uses that word any more). But that’s not the kind of value that’s going to drive widespread adoption of solid state lighting. What’s needed is a way to identify specific benefits of lighting control — aspects of illumination that improve human health, productivity, or perhaps even some more nebulous sense of well-being.

Quantifying the Promise of LED Lighting

Lighting Research Center's Home Lighting Design Tool

Knowledge of the effects of light can help produce illumination designs that influence behavior and health. (Image courtesy of RPI’s Lighting Research Center)

Also at Strategies in Light, Mark Rea, Director of the Lighting Research Center at Rensselaer Polytechnic Institute, spoke about various ways to quantify the value added by the ability to spectrally and temporally tune illumination. He is pushing the industry to help identify quantifiable metrics that can be applied to commercial, industrial, educational, and domestic environments to present a clear story of the value of controlled illumination in those environments. Of course, identifying a metric is different from establishing the connection of that metric to human health and performance. That work is in its early stages, with the exception of a few tantalizing tidbits. But enough work has been done to understand that human well-being, alertness, and productivity are influenced by lighting choices. Although some may quibble, I’d contend that this field is still at the stage where researchers are making their fundamental discoveries, and significant expertise is necessary to investigate and apply these illumination methods. It’s also my contention that herein lies the true value of solid state lighting. Without the ability to control illumination, it didn’t make much sense (and was difficult to do anyway) to investigate the effects of various illumination levels, colors, and timing. Now those investigations are underway, and the results should drive the value of LED lighting well beyond that of simply upgrading incandescent light bulbs.


Solid-state lighting — using light emitting diodes for general illumination — offers a host of advantages over incumbent technologies. For starters, LED lighting is five times (or more) as efficient as incandescent lighting, it has no components requiring hazardous material waste provisions (as do fluorescent lamps), and LEDs instantly respond to electric current, eliminating the delays inherent in high-intensity-discharge at startup and allowing the illumination level to be controlled. And those really are just for starters, as there are many other advantages.

But LED lighting has one big disadvantage: it’s completely different from other lighting technology. For example, LEDs are generally driven with DC current as opposed to the AC that powers just about every other source. Another big difference is that LED packages themselves (the LED chip, encapsulant, and primary optics) shape and direct the light. Contrast that with the tungsten-alloy filament at the heart of an incandescent bulb. When the filament heats up it puts out light (about 5 to 10 percent of its electrical power usage) in every direction.

Manufacturers can make specialty incandescent bulbs that have internal mirrors to direct the light in a certain way, but in general, one light bulb is just like another. You can replace a Sylvania bulb with a General Electric bulb with a Phillips bulb and you can put it in a desk lamp, an outdoor sconce, or a recessed fixture. Incandescent bulbs are commodities because the physics determines how a filament works, and there’s not much any manufacturer can do do distinguish their offering from another company’s. The good part is the interchangeability; the bad part is that the light output of incandescent lamps is cut down by the fixture efficiency (the amount of light that doesn’t get where you want it to go. Because the light from the bulb itself is uncontrolled — spreading out in every direction — you can’t match a bulb to the fixture in which you’d like to put it, so light (and energy) is wasted.

Matching the Light Source to the Task

What if, though, you could buy a different light bulb for every fixture, one tailored to minimize wasted energy for that one particular application? It would be expensive. And every few months or so it would burn out and you’d need to run down to the hardware store and buy a replacement bulb (selecting from the scores your retailer would need to keep in stock). So that’s not really a viable solution for incandescent bulbs. But it is for LEDs.
One of the advantages alluded to above is that LEDs can last a really long time (there are some issues with exactly how long, but that’s for another day). Long lifetime means that it’s reasonable to select an LED lighting solution specific to each application — because you won’t need to change it out for 5, 10, perhaps even 20 years or more. In practice, it’s a little more complicated than that because there’s not just one LED that will go in every desk lamp or cove light. Every luminaire (light fixture) manufacturer selects and arranges LEDs in a different fashion. So if you really want to optimize LED lighting you have to buy an entire fixture. It’s still a money-saving proposition (it’s not uncommon for industrial customers to get payback times of anywhere from a few years to several months), but it creates a dilemma for LED lighting.

LED lighting can be forced into an Edison-Screw bulb.  Image from U.S. Department of Energy.

LED lighting can be forced into a traditional incandescent bulb shape — but should it be?
Image from U.S. Department of Energy.

Retrofit or Redesign?

LED lighting manufacturers have two choices: they can make fixtures that optimize the distribution of light to fully take advantage of the new capabilities offered by solid-state lighting, or they can design retrofit bulbs that can be put into place as one-for-one replacements of existing incandescent or fluorescent fixtures. At last week’s LED Show the dilemma was (quite literally) on display. The purists argue that forcing LEDs to mimic (crappy) incandescent or fluorescent sources will set the industry back because customers will see energy savings, but not much more of the advantages of LED lighting. The retrofit folks argue that the replacement bulb solution lowers the barriers to entry, giving LEDs an absolutely necessary foothold into the general illumination market. At times, there’s some visible contempt expressed on one side or the other.

The logical path (one that’s already being played out) seems to be that retrofit solutions get LEDs in the door, where they then get to display some of their other advantages. Those bonus advantages then create showcase solutions that become selling points for designs that fully embrace the LED lighting solution.


Architects like solid-state lighting, but they’ve been burned by extravagant performance claims. DOE’s Next Generation Luminaire™ program eases the problem.
Patricia Glasow is one of the principals in the architectural lighting design firm Auerbach Glasow French. She’s designed and managed lighting projects throughout North America, Europe, and Asia. Glasow spoke at Strategies in Light (SIL), an annual conference on the status of and prospects for the solid-state lighting industry, held in Santa Clara, California, from February 22 to 24, 2011. In the last few years Glasow has noticed a trend: architects on every project are asking for solid-state lighting.

And why shouldn’t they? Solid-state lighting is ten times more efficient than incandescent lighting and light-emitting diodes can last 50,000 hours. So what’s the problem? Scott Riesebosch, president of CRS Electronics, an LED lighting manufacturer, said the problem with LEDs is neither the technology nor the cost. He taught a session on designing LED fixtures, also at the SIL conference. “The real problem,” he said, “is extravagant marketing claims.”

An Interplay of Systems
The problem has been a growing concern for the industry. LED lighting is based on LED semiconductor chips themselves, mounted on a carrier that defines a mechanical, electrical, and thermal interface…

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Originally published at Suite 101, 5 MAR 2011


Getting energy from the sun is an age-old dream. Now improvements in design, manufacturing, and deployment processes are turning that dream into reality.
The world is drenched in sunlight, an energy source that should remain at its current level for at least the next few billion years, so it shouldn’t be a surprise that an industry has grown around the promise of converting sunlight directly to electricity.

The devices doing that conversion are known as photovoltaic (PV) cells, and hundreds of players in the PV field converged on San Francisco in mid-February, 2011 to discuss the current state of the industry.

They came for a set of one-day conferences highlighting different aspects of PV technology, part of the “Solar Terawatt Series” sponsored by PHOTON International. The presenters painted a picture of a technology that is scaling up to meet energy needs today while at the same time researchers are making fundamental improvements to the design and manufacturing process of PV systems.

Originally published at Suite101, 2 MAR 2011


R&D in solid-state lighting (SSL) reduces future energy demands. The Department of Energy, in collaboration with industry, guides the development of SSL.
Solid state lighting (SSL) is the heir apparent to the general lighting crown. More energy efficient than its incandescent and fluorescent predecessors, SSL can take a huge bite out of the more than 765 Terawatt-hours (765 million-million Watt-hours) the United States burns each year on industrial, commercial, outdoor, and residential lighting.

Although fundamental physics makes SSL the most energy efficient lighting choice, scientific and engineering challenges limit its adoption. That’s why the Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) organizes an annual conference focussed on setting research and development (R&D) priorities for maturing SSL technology.

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Originally published at Suite101, 9 FEB 2011