February 2014

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Lighting Up LEDs

“Out with the Romex Wire: In with Category 6 Cable”

Jim Sinopoli
Jim Sinopoli PE,
Managing Principal,
Smart Buildings LLC

Contributing Editor

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Graphic 1The relentless penetration of IT has a long history of changing building systems; transforming analog phones to digital phones, changing analog surveillance cameras, IP-enabled access control, IPTV as well as a host of other systems. The next building system to transform to an IT structure is low voltage LED systems; it’s been in the making for a few years and led by some of the innovative companies and early adopters. It’s now at the point that where we can project that the IT structure for LED lighting systems will become the new norm.

The impetus for such an IT structure is linked to the fact that LEDs are low voltage light sources. One way of providing low voltage is installing AC power and converting it to DC; this will work but adds costs, additional points of failure and generates additional unwanted heat.

Graphic 2 Meanwhile, the IT industry has been providing low voltage DC power via Power over Ethernet (PoE) for over a decade. In 2003 an IEEE standard was published allowing low voltage power, 48 VDC, to be transmitted over an Ethernet Category 5 Twisted Pair cable. With the initial standard, the maximum that can be delivered to a powered Ethernet device is 15.4 watts, which is sufficient to power many low powered devices. A second standard, known as “PoE Plus” offers higher power levels (25.5 W of power) although still within the low voltage range. (One of the main reasons for the PoE plus was the need to provide enough power to surveillance cameras with pan, tilt, and zoom capabilities.)  Tech giant Cisco introduced a 60W power over Ethernet a few years ago.

PoE has several benefits:

This type of lighting system can allow for additional sensors, such as occupancy, temperature, automated daylight harvesting based on ambient light levels, and passive motion sensors, with all the data points shared with other building systems as appropriate. With the data from the lighting system and the building BMS, there is opportunity to create a rules-based lighting system, similar to HVAC’s fault detection and diagnostic rules, where real time lighting and environmental data can be used to optimize the lighting system or shared with other building systems.

Graphic 3 The use of DC is important. In most buildings, including our homes, we are surrounded by devices and equipment that internally operate on Direct Current (DC). We plug these devices into a typical Alternating Current (AC) outlet, and then AC is then converted to DC, each conversion creates an energy loss. In addition many newly constructed buildings are deploying renewable energy sources such as solar or wind which can generate DC power. With the large number of DC powered devices in buildings and DC generation now utilized in many newer structures, the addition of a DC LED lighting system adds the ability to distribute DC power in buildings and maximize of the use of DC power generated by renewables.

Researchers at Carnegie Mellon University have published a paper evaluating the cost of energy for lighting systems and concluded that a DC grid is far less expensive powering LED lighting. Researchers say DC power could save $24,000 a year in a 48,000-ft2 building lit by solid-state lighting (SSL).

DC infrastructure is getting traction. My colleague, Andres Szmulewicz, predicts that in less than 10 years we will have laptops and even PCs that plug into high power DC ports like smart phones or tablets do today. We are already seeing PoE to USB adapters built into face plates to provide USB ports for charging electronics.

While the approach to LED lighting systems is sound, it does come with a few issues:

Graphic 4 First, IT contractors can certainly install an IT system, but they are neither electrical nor lighting contractors. They will need training on installing lighting fixtures. Can they handle ceiling stringer supports, mount downlights in ceilings or install ceilings supports for pendant fixtures,?

Can IT understand required light levels, light distribution, contrast, color rending, luminous flux, luminous intensity and the lighting needs of particular spaces?  IT contractors may need to partner with a lighting company or develop in-house expertise. For a typical lighting control company, the reverse may be true, that is the lighting companies will need to team with an IT contractor or develop internal IT resources.

Also, many times a lighting system for new construction may go beyond just a lighting system to a comprehensive solution incorporating motorized shading and sensors for sun tracking and thermal loads. These systems have to be integrated in a way to optimize the thermal load from the windows with shades as not to have the HVAC system start cooling, as well as optimize occupant light levels. That type of complexity is way beyond simply providing low voltage DC to an LED.

Graphic 5 Light Emitting Diodes (LEDs) are semiconductors. They can be configured in an analog mode to be used primarily in the older lighting systems, but new systems are likely to be all digital. Digital means an infinite number of colors, scenes and brightness settings and control. IT based low voltage LED lighting systems combine energy efficiency, long lasting LED lights, the use of DC power, an opportunity for additional sensors and data points to assist in managing the building’s performance, and leveraging the IT network to deploy the lighting systems. The low voltage LED lighting system seems to reflect almost everything the building industry has been talking about regarding building control systems. It will be a monumental move that is more likely to spark additional innovation.

What’s not to like?

For more information about smart buildings, technology design or to schedule a Continuing Education program for your office write us at info@smart-buildings.com.

All photos are courtesy of Google and/or Bing images.


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