View This Issue - June 2013

Lighting industry progresses on DC-power grids that pair well with LEDs (MAGAZINE)

+++++

This article was published in the April 2013 issue of LEDs Magazine.

View the Table of Contents and download the PDF file of the complete April 2013 issue, or view the E-zine version in your browser.

+++++

There is a long-standing debate as to whether we would be better off had Tesla prevailed over Edison, and we had a DC-voltage power grid. Actually the answer isn’t clear cut, but without question a DC grid in a building can increase energy efficiency for many building systems including lighting. Indeed LEDs need DC power, so DC-powered solid-state lighting (SSL) eliminates one lossy power-conversion stage. The technology has become a reality with a proprietary scheme from Redwood Systems that’s widely available and the standardized EMerge Alliance-based products coming onto the market. Moreover, a play from the IT-centric Ethernet networking world may be waiting in the wings.

Fig. 1. An installation of JLC Tech T-Bar LED linear fixtures at AWeber Communications in Pennsylvania illustrate how DC-powered SSL products blend into the ceiling grid.
Fig. 1.
DC power can provide several benefits, starting with energy efficiency, as we will discuss later. But it offers flexibility as well, such as in flush-mount unobtrusive lighting systems including the T-Bar LED linear fixtures from JLC Tech (Fig. 1). Moreover DC-powered lighting tiles that snap into ceiling or wall grids are headed to market.

First, however, let’s step back and consider how the building industry as a whole could benefit from a DC grid – at least internal to the building. Consider the situation even in a home. Nicole Bopp, director of marketing at Nextek Power Systems, said that ultimately 80% of the watts used in the home power DC loads. Most all consumer electronics operate from DC at their core.

In a commercial building, however, the opportunity for savings are more substantial. IT data centers are a huge opportunity because all of the computer equipment could be more efficiently powered by a DC grid. Indeed there has been a movement in the computer industry over the course of the last decade to adopt DC power in the data center. The EMerge Alliance is now shepherding that movement along with supporting DC grids for lighting.

EMerge Alliance

The EMerge Alliance was founded with a broad DC mission originally, but was perhaps most identified with SSL. Brian Patterson of Armstrong World Industries and chair of the EMerge Alliance said that adoption of a DC grid is “probably going to be driven by disruptive opportunities in the playing field.” LEDs provided the alliance just such an opportunity. Most SSL products include an AC/DC power conversion as the first stage of the LED driver electronics and that is ripe for elimination in a DC world.

Patterson in fact said that it’s both energy efficiency and reliability that will ultimately drive a transition to DC in lighting. Simplifying the driver to a DC/DC stage will in many cases eliminate the need for the electrolytic capacitor that is regularly identified as the most likely failure point in an SSL product. Patterson said that the driver can match the long life of the LEDs in a DC-powered scenario. The DC transition would also increase the system-level energy efficiency that’s inherent in LED-based lighting.

It turns out, however, that there are even more reasons for considering a transition to a DC grid for lighting. The EMerge Alliance has adopted a 24V DC bus. Patterson said, “It’s a voltage that can be made very safe and is very near the use voltage of LED lighting.” In fact, electricians are not required to install the DC cable runs.

DC power sources

Two companies currently have power sources that are registered with the alliance – Nextek and Roal Electronics. Nextek calls its products Power Server Modules (PSMs), a sample of which is depicted in Fig. 2. Marketing director Bopp said, “In-conduit AC wiring is required to the PSM,” but the DC cables out of the PSM are treated essentially like computer network cables and can be connected without removing power from the system.

The DC grid can in fact be run on cables that are available from companies such as TE Connectivity or integrated directly into a dropped-ceiling grid frame such as in the DC FlexZone products from Armstrong. The Armstrong products provide connectivity in the suspended-ceiling grid with electrical connections made as you assemble the grid.

Fig. 2. Nextek Power Server Modules supply 16 DC channels, each capable of handling 100W.
Fig. 2.
The flexible connection scheme means that office spaces and lighting products can be easily rearranged as the need arises. Last summer, we ran an article about a DC-powered installation in a conference room at Paramount Pictures. Osram Sylvania and Rensselaer Polytechnic Institute’s Lighting Research Center (LRC) worked together on the project. The LRC has long championed the concept of lighting tiles that can be snapped into a grid, offering a simple way to reconfigure lighting.

Of course, a DC installation does have to account for the total load connected to a power source so there will always be some needed expertise in partitioning a DC system. The Roal Safe Energy Server SES400 has four output channels, each rated at 100W (Fig. 3). Nextek’s PSMs have 16 100W channels.

DC for legacy or SSL

The DC scheme can actually be used with legacy or LED lighting, although you can power far more fixtures in the SSL case. Nextek’s Bopp said that even fluorescent lighting can be operated more efficiently on a DC grid. She said that a typical electronic AC ballast does a conversion to DC and then a second conversion to high-frequency AC. Nextek offers a number of ballasts that can convert fluorescent fixtures to DC operation. Still Bopp said that in the case of typical T5 fluorescents, each PSM channel can only power two fixtures.

With many SSL products operating down in the 10W range, you can in some cases connect 9 to 10 fixtures on one PSM channel. Nextek recommends that you keep cable runs to 30–40 ft, meaning that one PSM can serve a radius as large as 80 ft. With florescent lighting, Bopp said you can typically service 1000 ft2 with one PSM, and in the case of SSL, that number goes to 2000-3000 ft2 because of the more efficient fixtures.

You may wonder why the EMerge Alliance adopted an architecture that still requires AC distribution to all areas of the building. The primary reason is logistics and compatibility with legacy technologies, although there are also some benefits in terms of ease of use with solar systems.

In reality, the EMerge standard does support DC-powered room-level power sources. Indeed, Nextek offers AC-powered PSMs, DC-powered PSMs, and models that accept either type of power. Patterson of the Alliance said the organization attempted to support architectures that range from a direct conversion to DC at the 13.2- or 16-kV pole to hybrid approaches where the DC conversion is done close to a system such as lighting.

In the case of solar, the Nextek product that supports AC and DC inputs comes into play. Bopp said that it can run on a DC input from solar panels during the day and seamlessly transition to AC power as the sun sets. Support for such a solar system is yet another selling point for DC grids. When the output of solar panels has to be inverted to AC, there is yet another efficiency loss.

EMerge obstacles

Given the benefits of DC, it’s a fair question to ask why the EMerge technology has not thus far taken off. About the building industry, Patterson said, “Nobody likes to be first.” But in fairness, there just has not been a sufficient choice of products available in the EMerge case. That’s changed rapidly in the past few months, according to Patterson. Indeed the registered products list is getting quite long (www.emergealliance.org/Products/RegisteredProducts.aspx).

Fig. 3. The Roal Electronics Safe Energy Server is a four-channel low-voltage DC power source.
Fig. 3.
Osram Sylvania has a number of registered products, including the RLC22 recessed LED fixture (Fig. 4) that won Next Generation Luminaires’ recognition in the 2012 indoor competition. There is also a product from Philips Lighting on the registered list. Moreover, Osram Sylvania, Philips Lighting, and GE Lighting have all announced that they are working with Armstrong on FlexZone-compatible products. There are other companies such as Lunera Lighting that have announced EMerge-compliant fixtures, but that aren’t yet on the registered products list.

EMerge-compatible products can be recessed or even flush-mounted to a ceiling. For example, the previously-mentioned T-Bar LED linear fixtures from JLC Tech can be flush-mounted to the metal rail of a drop ceiling. Armstrong has demonstrated how even track lighting heads can connect directly to the FlexZone system.

Redwood Systems

Long term, EMerge technology may become the predominant DC-powered approach, especially considering the pledged support from major lighting companies and the fact that it is an open standard. However, there are other challengers. Redwood Systems, for instance, has been selling its Redwood Building Performance Lighting Platform for several years.

The Redwood platform is far more than a DC power-distribution system. In aggregate, the platform includes application and commissioning software for adaptive control of the lighting system along with a DC-based power-distribution engine that also carries the control commands to fixtures and light- or occupancy-sensor data, and luminaire operational data, from fixtures to the centralized system.

Fig. 4. The Osram Sylvania RLC22 recessed LED fixture is on the EMerge Alliance registered products list.
Fig. 4.
The Redwood Engine (Fig. 5) is a box-level product that powers the cable runs and looks much more like computer networking equipment than a power supply. Like EMerge technology, the Redwood platform relies on low-voltage Class-2 wiring that does not require an electrician for installation.

Redwood is working to create a partner network of luminaire makers that support the technology. For example, MaxLite and Lunera have previously announced compatible products. Redwood also supports non-compatible fixtures, including those based on legacy sources, such as fluorescent lamps, via relay-based control boxes.

The Redwood value proposition is ultimately centered on energy efficiency combining inherently-efficient SSL products, controls to dim or turn lights off when they aren’t required, and the more efficient DC distribution. A key advantage for the company is the inherent inclusion of controls. The EMerge Alliance doesn’t explicitly address controls. Nextek, for example, sells wireless controls that are essentially separate from the DC power grid.


Retrofit costs Fluorescent AC LED PoE LED
Fixture $200 $350 $350
Dimming ballast/lamp $70
Fixture install and ballast $250 $250 $50
PoE wiring/labor $150
PoE port $75
Controls/sensors $200 $200 $60
Total $720 $800 $685

Table 1. Power over Ethernet could lower the cost of controllable lighting

Redwood Systems has completed major projects for a number of high-profile customers. For example, the Volkswagen Electronics Research Laboratory in Belmont, CA, uses Redwood technology, and the lighting is controllable via smartphone apps. The SAP Labs facility in Palo Alto, CA, uses Redwood technology and the company said it delivers $80,000 in operational savings each year.

Power over Ethernet

While the Redwood technology utilizes Cat-5/6 cables (Ethernet cables) to deliver power to fixtures, the Redwood system is proprietary. But there is the potential going forward to use Ethernet products designed for networking to power SSL fixtures. The network industry has developed an extension to Ethernet called Power over Ethernet (PoE) that was designed to allow an Ethernet cable to carry both power and data. The original intent of the technology was powering remote network devices. For example, an Ethernet cable could both power a Wi-Fi access point and provide the data connection between the corporate network and the access point. PoE was envisioned to support such remote devices where ready access to AC wiring wasn’t available.

At the recent Strategies in Light conference, Chris Isaacson, CEO and CTO of NuLEDs, made a presentation on IT networked lighting systems. Isaacson foresees integrating lighting with the IT infrastructure and inherently making every light fixture intelligent.

From a technology perspective, PoE could certainly power SSL products. The first-generation IEEE 802.3af specification makes almost 13W available to an end device – certainly enough to power many SSL fixtures. The more recent 802.3at PoE+ spec makes 25.5W available to the end device, and that’s enough power for most indoor SSL products other than high-bay lighting.

Isaacson sees the situation improving even further. He said the new Universal PoE (UPoE) standard being pushed by network-equipment vendor Cisco will again double the available power. By 2014, a single UPoE Ethernet cable will be able to power two LED troffers with the continuing ramp in LED efficacy, according to Isaacson.

Fig. 5. Redwood Systems’ Engine both distributes DC power and transmits control data over low-voltage wiring.
Fig. 5.
Indeed Isaacson painted a rosy picture for PoE. He said LEDs alone provide 30% in energy savings over legacy lighting. Using DC power ups that to 55%. Inherent network controls would bring the total to 80% savings. And Isaacson asserted that the technology would cost less than fluorescent or AC-powered LED lighting if the cost of controls is factored into the equation (see Table 1).

Reliability and PoE availability

Still, there are questions about PoE. Our computer networks are very reliable, but our lights always work so long as the AC power is on. It’s not clear that PoE could deliver the expected level of reliability relative to our experience with AC-powered lighting. When asked about reliability, Isaacson said you could mix lighting connections on multiple switches to assure that a single network switch failure would only impact a part of a building’s lighting.

Moreover, Isaacson discussed the prevalence of Ethernet in the corporate world as part of the justification for the concept. But most installed Ethernet does not include PoE support today. The existing infrastructure isn’t ready for lighting. But Isaacson sees PoE costs dropping and says that as long as the powered ports in a switch are utilized, then the economics will work. He said NuLEDs hope to launch a pilot project this summer with a Fortune 100 company.

DC bears watching

What is increasingly clear, however, is that the lighting world will have a brush with DC power, whether the technology is one we covered here or another system entirely. DC could remain a niche offering, or it could become predominant. SSL product manufacturers and lighting designers would be well advised to play close attention.

Consider research conducted last year by Carnegie Mellon University. The university reported that a DC grid would save $24,000 per year in a 48,000-ft2 building lit by LEDs. Moreover, adding solar power to the equation would increase the savings by $5,000 more. Those numbers are over and above the baseline savings afforded by LED sources.

Patterson of the EMerge Alliance is also predicting big things for DC as this year unfolds. He said, “At Lightfair some companies will announce universal luminaires that can work from AC or DC.” Moreover, he said that many of the registered-compliant products are now truly commercially available and not just being made in pilot quantities.

You will also start to see real case studies based on EMerge Alliance technology in the coming months. For example, a recently opened PNC Bank office in Fort Lauderdale, FL, is among the first net-positive bank branches that can generate more energy than it uses via solar panels. The news stories about the building focused on the solar angle, but an EMerge-compliant DC grid is a major part of the underlying story. We hope to bring you more details on the project and others soon.



Did You Like this Article? Get All the LEDS Magazine News Delivered to Your Inbox.

Subscribe to the magazine or email newsletter today at no cost and receive the latest news and information.

 Subscribe Now
RELATED NEWS & ARTICLES
SIL STRIKING POINT: Connected lighting panel will debate protocols

SIL STRIKING POINT: Connected lighting panel will debate protocols

Strategies in Light (SIL) conference co-chair and Strategies Unlimited research director PHILIP SMALLWOOD drives home that wireless standard protocols are reaching a critical decision point in this rundown of the connected...

Competing wireless standards will wed at CES, SSL may benefit

Competing wireless standards will wed at CES, SSL may benefit

Networking technology has become increasingly important in LED-based lighting, but the SSL sector is hampered by the lack of interoperable standards and the Consumer Electronics Show should see progress on that conundrum.

Cypress launches a 1A LED driver IC for auto applications

Cypress launches a 1A LED driver IC for auto applications

The buck-topology driver from Cypress Semiconductor can operate at switching frequencies in excess of 2 MHz, which means that the driver electronics can fit a tiny footprint with small magnetic components.

Osram uses CES as a venue to expand Lightify networked lighting portfolio

Osram uses CES as a venue to expand Lightify networked lighting portfolio

The Lightify family of networked lighting products will get several new members at the Consumer Electronics Show this week, including outdoor RGB strips, and wireless switch and plug products.

LIFX cuts price - again - on color-changing LED lamp

LIFX cuts price - again - on color-changing LED lamp

Not long ago the smart lamp was $100. Now it’s set at $50.

British LED specialist teams with IBM Watson for IoT

British LED specialist teams with IBM Watson for IoT

PhotonStar is the latest solid-state lighting company to join forces with an IT powerhouse.

Philips Lighting delivers LED art/light panels, adds SSL partners

Philips Lighting delivers LED art/light panels, adds SSL partners (UPDATED)

LED panels can be integrated into various designs in the built environment, while new Philips partners add colorful relationships with Hue and additional connected lighting.

SIL STRIKING POINT: Strategies in Light 2016 to feature advanced LED lighting concepts

SIL STRIKING POINT: Strategies in Light 2016 to feature advanced LED lighting concepts

Using LED lighting as a ‘building block’ for new architectural designs is a hot topic of conversation between conference co-chair BOB STEELE and EOIN BILLINGS, who will present at SIL 2016 along with partner Duncan Jackson...

Connected lighting from UK startup amBX allows dynamic illumination at London conference center

Connected lighting from UK startup amBX allows dynamic illumination at London conference center

The 'Light-Scene Engine' supports a mix of 16 million colors for variable color schemes and features wireless controls.

It’s official: Philips, Cisco join forces to sell connected lighting

It’s official: Philips, Cisco join forces to sell connected lighting

The two companies confirm their Power over Ethernet collaboration. Philips also strikes IoT deals with SAP, Bosch.

Digital control in LED drivers delivers better dimming in lamps

Digital control in LED drivers delivers better dimming in lamps (MAGAZINE)

Scott Brown describes the dimming challenge in LED lamps that are connected to phase-cut dimmers and details the basis for digital control techniques that can enable flicker-free performance in SSL applications.

LED- and SSL-centric products shine in a techno-savvy gift list

LED- and SSL-centric products shine in a techno-savvy gift list (MAGAZINE)

Around the world, visions of brightly colored packages and tantalizing treats run through our minds. But in this case, Maury Wright and Carrie Meadows look toward the techies, the trend-spotters, and some folks too hip for...

GE taps IBM exec for new IoT lighting and energy unit

GE taps IBM exec for new IoT lighting and energy unit (UPDATED)

Former vice president of the Watson cloud computing services group will lead the digital charge at GE's Current.

Princeton retrofits Jadwin Gym with LED sports lighting and wireless controls

Princeton retrofits Jadwin Gym with LED lighting and wireless controls

Ivy League school updates its 250,000-square-foot athletic facility with 839 Hubbell SSL fixtures and deploys the company's wiSCAPE network control system.

Understand the lighting flicker frustration

Understand the lighting flicker frustration (MAGAZINE)

Lighting control manufacturers are committed to reducing flicker, improving LED performance, and providing commercial customers with comfortable, efficient lighting and control solutions, but Ethan Biery explains that the ...

Connected LED lighting dominates SALC, but focus is services

Connected LED lighting dominates SALC, but focus is services (MAGAZINE)

The annual IES Street and Area Lighting Conference featured a comprehensive set of presentations on topics ranging from new recommended practices to dirt depreciation, but as Maury Wright reports, the major theme was netwo...

Philips, Cisco on brink of connected lighting partnership

Philips, Cisco on brink of connected lighting partnership

An announcement by the companies is expected next week, and should include Power over Ethernet.

Digital SSL’s mega disruptor will be Power over Ethernet

Digital SSL's mega disruptor will be Power over Ethernet (MAGAZINE)

Power over Ethernet distributes DC power over inexpensive data cables instead of costly conventional lines, threatening utilities, electricians, and contracting firms, explains Mark Halper. Meanwhile, the technology turns ...

Digital Lumens adds emergency lighting to LED luminaires and control suite

Digital Lumens adds emergency lighting to LED luminaires and control suite

Battery backup for luminaires will combine with new capabilities in the LightRules software management platform, allowing companies to install a single lighting system in industrial and warehouse settings with requisite em...

Aurora regroups, forms an Internet-connected lighting division

Aurora regroups, forms an Internet-connected lighting division

LED lamp and luminaire specialist folds its Microlights unit, readies a new “Lighting 3.0” entity to leverage Gooee IoT technology.

TOPIC INDEX

CURRENT ISSUE



CONNECT WITH US

                

SOCIAL ACTIVITY

SUBMISSIONS

Have a press release or other announcement you'd like to share?

Submit Announcement

Miss a webcast? Watch it in the archives

Copyright © 2007-2015. PennWell Corporation, Tulsa, OK. All Rights Reserved.