LRC's Mark Rea discusses monetizing the benefits of SSL, and SIL Plenary

Dec. 17, 2013
The LED lighting industry needs to focus more on the benefits of solid-state lighting (SSL) technology rather than purely on energy savings, according to Strategies in Light Plenary speaker Mark Rea, as he discusses in an interview with Maury Wright in advance of the conference.

Mark Rea is the director of the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute and will present a talk entitled "Monetizing the potential benefits of solid-state lighting" at the 15th-anniversary Strategies in Light (SIL) conference that will take place in Santa Clara, CA from February 25–27, 2014. In a question and answer session, Rea previews some of the topics he will discuss at SIL, and made the point that the lighting industry need to transfer the primary focus on how solid-state lighting (SSL) deliver application-centric benefits when designed properly that will ultimately prove more important that the energy-saving and long-life benefits inherent to LED sources.

LEDs Magazine: Given all of the technology research conducted at the LRC, I was surprised to see the title of your SIL presentation. I know that the LRC has commercial partners, but I think about the center more for technical research. How did you settle on a talk based on monetizing SSL?

Mark Rea: It goes back a while. We organized a symposium called Bridges in Light in 2003. Our crystal ball identified two major revolutions in that the future of lighting would be solid-state lighting, and the importance of lighting to health. We have also been active in transportation lighting, especially in the area of dynamic street lighting where you take advantage of traffic patterns.

The theory put forward by the lighting industry on a value proposition at the time was really like stale beer. The industry was focused on a commodity business, focused on getting the price down, longer life, and lower energy. Those are all good things; no one is arguing about that. But those things are really the denominator in the value proposition. The numerator is the benefit. You are trying to do something per watt.

I've described it in prior talks as the sparkle per watt. In an application like a hotel ballroom, you can put in an energy-efficient fluorescent system. But hotels install chandeliers to create the sparkle.

The idea to focus on the numerator as well as the denominator to increase value is what I'm talking about when I mention monetizing SSL. SSL gives us degrees of freedom. And I've been working on lighting controls for a long time. Little attention has been given to this numerator and how we engineer them and quantify them. We miss the profitability if we only focus on the denominator.

LEDs Magazine: Lately, I have heard a number of people suggest that SSL is now efficient enough that we should begin sacrificing some amount of efficacy to deliver better quality products. Do you agree with that, though? Is that part of what you are suggesting?

Rea: I agree with the intent but not the phraseology. Quality is something that you can't measure. If you want to design a brighter space, you can measure and quantify it. In outdoor lighting applications, you can get 50% energy savings if you design it by brightness rather than by lumens. A cool LED light source would require 50% less power. The light level would be lower but it would be seen as equally bright by a human and be equally safe.

LEDs Magazine: So are you saying we should always use cool-white fixtures in outdoor projects?

Rea: You first of all must define what you are trying to do in a parking lot. If you want to thread a needle in a parking lot, then a lumen is probably the right metric that you want to use. Lumens per watt is exactly what you need. But if you want people to feel safe and secure, the lumen is the wrong metric to quantify the light source efficacy.

The visual system is complicated enough that we have multiple channels. In the grossest sense you've got the non-visual circadian regulating channel. You've got an acuity channel. You've got a brightness channel. You've got an off-axis vision channel. All of these things require different spectral tuning to maximize the benefits required in the application. And it's interesting that a lot of people don't realize that it takes a cooler source to make a parking lot look brighter.

But the design criterion is different if you want to light the edge of a roadway to see a deer better that might jump onto the road or to see pedestrians. The channels in the eye and the brain are different for those two visual requirements. Generally, people think about lighting as some kind of monolithic "Well, I see you or I don't see you" situation. But that's really not the way it works. It's a much more complicated network of information that we extract from the environment.

If we really want to maximize the benefits of lighting, and therefore monetize if you will, then you need to tune the spectrum and the amount to what it is you are trying to see. First you decide, what am I trying to do with my design? Then you select the criterion that represents that benefit that you are trying to accomplish. And you engineer the application in a way that everybody makes money and saves energy.

LEDs Magazine: You say that quality is hard to measure, but there are elements such as color rendering that are part of the quality story. It's been frustrating with how slow the industry has moved to adopt a better color rendering metric than CRI. What do you think about color quality in general and metrics specifically?

Rea: I'll discuss color in my talk at SIL. And I'll try to make it not like "my metric's the best." The truth is that it's going to boil down to two metrics. Any attempts to bring it down to one will fall short. We've done studies. Everybody would say that I have a 95-CRI lamp and people are going to prefer that. We have shown that if you don't also address the issue of saturation — in other words, how vivid are the hues — you will find people not preferring it. It's not that they will hate it, but they won't prefer it.

We have this second metric, the Gamut Area Index (GAI). The industry has CRI. You can talk about CQS but basically it's reshuffling that basic idea that when you change light sources the color of the object shouldn't change. But this other dimension called saturation says that you can sort of add spice to your eggs. Sometimes you can make it more vivid or less vivid. We have shown retailers and they absolutely love this two-metric system. And we've got a number of companies now beginning to build light sources of this type.

The bottom line is that it's a two-metric argument. You can argue about my second metric is better than your second metric. But it's two metrics. The second thing is we're already seeing lighting manufacturers build these light sources and we will see retailers begin to embrace this two-metric system. Stay tuned. I'll give a little high-level discussion of it at SIL and the value proposition. For instance, I talk about color rendering per watt. I don't understand why we can't use that as an efficacy measure. If that's what you want to do, if your design objective is to have good color rendering. Why do we have to go to lumens per watt?

Moreover, if you think about monetizing lighting, and that's the theme of my talk, then you have to think differently about controls. We tend to think of dimming as a controls strategy and of course that's the old way of thinking, focused on saving energy and watts. You could have a control where you increase or decrease the saturation in your lighting source depending on what you want to achieve.

Culturally, people from different regions of the world prefer different saturation of vividness in the objects that they are illuminating. The Nordic countries prefer less saturation. Places like India prefer much more saturated colors. Why do we to have to place a dimmer on light level? Why don't we give a device that changes the saturation in a light? For example, you might change the saturation for a party.

The opportunities for business are in the numerator of that value proposition, the benefits that you deliver. Otherwise it's just a fight over price. It's the benefit divided by cost. We spent a lot of time talking about cost. It's time we started quantifying the benefits. We've seen a backlash from designers not talking about quality. The problem is you can't engineer quality. You have to measure something to build it.

LEDs Magazine: What about trading efficacy to lessen glare in outdoor applications? We've seen a trend in some outdoor fixtures where diffuser and reflector technologies are coming back in place of fixture designs that exposed the LEDs. There is a quality angle to that because it makes for a more enjoyable experience for pedestrians. And there is a safety issue as well.

Rea: True. But how do you measure it? How do you know you achieved it? How can you accurately say I've delivered 20% less glare? You could sort of wave your hands and say, "Well, I diffused the source." Okay, that's good. But I find it a little bit disingenuous to say, "Well, I'm disregarding what you measure for something I say is higher quality." You are not really engineering it now. Now you are talking about personalities of the lighting designers. I'm not arguing they are wrong. It's easy to criticize, but if you engineer it and sell it, how are you going to deliver what you say you are going to deliver?

LEDs Magazine: What about the BUG (backlight, uplight, and glare) ratings? There is a glare specification as part of those ratings.

Rea: Well, yes and no. But glare is notoriously difficult to measure. You are talking about no consensus. That's a contentious discussing and that has to be socialized in a standards body. Again, you need to be able to quantify what we are talking about. There are two types of glare. Disability glare, where you have contrast reduction, and that's pretty straightforward and relatively easy to measure. But what people are really talking about is the discomfort glare.

We have our version of metrics for that and there are several others. I see a lot of people talking about it. But I don't see a lot of traction, not nearly so much as with color rendering, with coming to a consensus on what glare is. The problem is that the metric changes depending on how close you are to the fixture. We can get a pretty good projection when you are a long way from the fixture. But generally what people are objecting to is standing under a luminaire and look up into the fixtures. That's a harder quantification problem. We have an approximation, but I'm not altogether happy with our own metric in that regard. And I don't see much systematic, organized discussion on that.

With regards to our conversation, we have a lot of opinions. But we don't have an organized way to address some of these benefit metrics. It's a negative benefit for glare. But it has the same basic principles that one could apply. It seems to me that an important next step is to have more meaningful discussions on what is glare and how to measure it.

LEDs Magazine: You said light and health was one of the opportunities you identified early on. Where does that opportunity stand in near-term commercial viability and revenue potential?

Rea: That's a really good question, and I get asked that often. We just came back from Sweden and we have a project with Sweden called the Healthy Home. Energy has always been a significant concern for them because they don't have a lot of generating capacity. But they have a whole culture that is interested in light, particularly this time of the year. I was there in Stockholm where it gets dark at 3:30 in the afternoon. What they appreciate, and if you go back to my numerator and value proposition, is that we don't want to save so much energy so that we deprive ourselves of light.

We're working now with a lighting architect to design a Healthy Home in which the technology we've been developing, this personal light exposure device, becomes something that's with you at all times of the day. When you come home you download the information to control the lighting system in a home. It will also give you a recipe for what you need the next day. If you want to get up an hour earlier than normal, for example, it will give you a recipe for how to do that the next day.

The real missing piece of this light and health issue is that you have to get the measurement of your own light exposure before you can really engineer what you need to do. In broad terms, blue light in the morning and yellow light at night are good ideas but again that becomes very qualitative and difficult to deliver accurately. The difference between someone sitting at a computer all day compared to someone working outdoors on a construction project means vastly different scenarios in what you need in terms of light exposure.

We are working on what I think is the key missing piece, and that is the personal light exposure device, that talks to something in your home, which in turn provides the best light you can have without wasting energy. That's really what this Healthy Home project is about. So there is a lot of excitement in Sweden, but it's only a country of 9 million. But they are very enchanted with this idea of the Healthy Home — how can I save energy and how can I provide myself with good light?

What we have found in Sweden is that the concept of people being grumpy in winter is accurate and light related. But this is the first time anyone has quantified it and measured it. We can talk about these things. But if you can't measure it, you really can't do much about it.

The device measures light level, spectrum, duration, and the time of day you had the exposure. You have to keep track of all of this data to be able to accurately predict how the next light exposure will impact you. And that's really the central issue. You can't keep track of it yourself.

We're always about ten years ahead of commercial technology as a research organization, and that's my projection for when you will see the type of products that I'm talking about. The other enabling device is the smartphone that will provide a platform to do these things. That could mean that it comes together faster than ten years. But as a lighting community, we don't deal much with personal sensors. That's not part of our culture. We have to embrace that to really do a meaningful job of light and health.