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.

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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.

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It’s interesting to watch the evolution of a technology.  I attended my first LED lighting conference in 1998 and I’ve attended at least one in every intervening year.  In those first years, Las Vegas was the primary customer.  Nowhere else was lighting such a significant expense — and such an essential part of marketing.  Higher efficiency and lower maintenance represented a huge savings for casino operators on The Strip.  But the ability of LEDs to manage the distribution of light (direct it to the consumer instead of spraying it into space) and the flexible control of LED lighting (to easily reconfigure displays) added to the energy savings to make LED lighting worth the investment.

But there’s a big difference between convincing casino operators to upgrade their high-value, high-maintenance displays and getting consumers to shell out big bucks to replace their 25-cent incandescent bulbs.  The fundamental problem is that LEDs are significantly different than their incandescent predecessors, but it’s difficult to take advantage of their new capabilities within the current infrastructure.  So people pushing for LED adoption have to limit their argument to two factors: it will save energy and it will reduce maintenance costs.  It’s kind of like arguing for replacement of horsedrawn buggies with gas-powered automobiles, but having your arguments for change limited to discussions of lower hay costs and reduced need for street cleaning.

LED lighting squeezed into a familiar incandescent bulb form factor.

LED lighting can be made to look like an incandescent bulb, but that’s like requiring a buggy whip on a Ferrari.

Even with that limited evaluation, LEDs are now well past the point where they are economically viable (after some intense political, economic, and technological growing pains), so just about any lighting project today needs to at least consider LEDs as an option, and for many developers they are the option of choice.  But now that LED general illumination is in place, system operators are realizing some other benefits.

Networked Capabilities of LED Lighting

At the LED Show (starting yesterday in — fittingly enough — Las Vegas) Kelly Cunningham of the California Lighting Technology Center (CLTC) at the University of California-Davis described a networked implementation of LED lighting control on the university’s campus.  Outdoor LED lighting at the campus is triggered by passive infrared sensors that provide little more than a simple present-or-not signal.  Even with that limited input, the control system anticipates pedestrian and cyclist movement, bringing lighting up to full brightness levels before the traffic reaches the lit area.  The ability to remotely control and instantaneously modify the illumination level of LEDs is central to the operation of this kind of system, and the immediate benefits are impressive.

For example, 100 wall packs (those curious rectangular fixtures affixed to the outside of buildings and washing the walls with light) detected only a 28 percent occupancy rate, leading to an 85 percent reduction in energy costs — over and above the reduction simply due to LED efficiency alone.  The CLTC implemented the same kind of system on a stretch of urban roadway.  Although the final report has not been released, Cunningham said the results are similar.

That’s encouraging news for the industry, because those are the kind of integrated lighting systems that insiders have been claiming would lead to additional levels of savings (and other capabilities, but that’s another story), and this provides another fairly significant example of the promise coming to fruition.  It also demonstrates another general truth: if you don’t have a capability, then you don’t have any idea what you’ll do with it; but when you develop the capability you will apply the capability in clever ways.  That’s true for networked lighting now.  In the near future, the precise control LEDs offer over color, intensity, and distribution of light will be used to modify illumination in our work and home environments to enhance our comfort and productivity in ways we can only glimpse today.

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Ran across this item at Renewable Energy World:

It wasn’t so long ago when some solar company executives – particularly those in the thin film business – dismissed the idea that innovation could still thrive in the world of crystalline silicon technology. The silicon technology was getting cheaper and factories were getting larger, and its dominance seemed unshakable, at least in the short-term. Why would anyone invest in new materials or production processes?

Turns out, a lot more can be done to chip away at the manufacturing cost. This is especially true when silicon technology companies are eager to set their products apart in a market that’s got way too many same-same solar panels.

Although Ms. Wang is certainly accurate in her reporting, I have to chuckle (metaphorically) at the “rush” to innovation. I think the rush is simply a sudden awareness (or sudden awareness of the importance) on the part of the non-technical executive offices of the need for technological innovation at the material, cell, and panel level—a process that’s been continuous for decades. For example, a year and a half ago, at Photon’s PV conference, Centrotherm discussed/announced their “turnkey” CIGS factory, allowing anyone with the required capital to produce thin film solar cells. The question then becomes, how does one distinguish oneself from the other producers?

Although the situation for silicon photovoltaics is slightly different, in that there are a few competitive approaches to cell and panel fabrication, there is not a clear differentiation in the final cost and performance numbers (or the levellized cost of ownership, as folks like to discuss nowadays). As long as there is no clear differentiator, there will continue to be a search for one.

What kind of differentiator? Well, what are the customers saying? At PV America West in March of this year, a panel discussion about the solar utility business model had absolutely no discussion of the role of technological innovation on the part of their suppliers. When presented with the question of the relative importance of technological innovation, the panel members stated that it was important, but (essentially) only in the context of decreasing costs.

Certainly this is a bit too complicated to address in a short post (it would probably be a bit too complicated to address in a non-partisan two-year congressional investigation, for that matter…), but given the disappearance or erosion of subsidies, technological innovation and its concomitant cost reductions will become even more important in the future.

So, “rush”? I can’t disagree with the sense of urgency that word implies, but technological innovation in silicon photovoltaics and related technologies is nothing new.

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A photovoltaic solar cell converts light to electricity. That is, photons — the tiniest quantity of light — transfer their energy to electrons, freeing them to move away from their home atoms. The current and voltage a solar cell can supply is not constant even when the illumination is constant. The current and voltage depend upon the resistance of the electrical load connected to the solar cell. Load lines are tools for evaluating solar cell performance for a given electrical load.

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Originally published on eHow, 2011.

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