Desktop version

Home arrow Engineering arrow Advanced Technology for Smart Buildings

Emerging Lighting Systems

The relentless penetration of IT has a long history of changing building systems; transforming analog phones to digital phones, analog surveillance cameras to IP 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. The impetus for 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.

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. Since its inception, the wattage of PoE has increased, and is now able to provide as much as 100 Watts for some devices.

PoE has several benefits:

b It costs less: It is much less expensive to provide a PoE network port than to install conduit, wire, a backbox for an AC outlet, a transformer for conversion, and pay for an electrician. PoE significantly reduces the cost of installation and construction. As an example, Purdue University installed over 1,100 PoE wireless access points across campus, and saved $350 to $1,000 per location by not having to install typical AC power. Others have estimated that the electrical cost to provide power to a device is about $864, while the cost of a PoE network port is around $47-$175.

b PoE increases reliability: PoE centralizes power distribution. Instead of a power outlet at each local device power is now distributed from the telecom rooms. Centralized power makes it easier to provide uninterruptible and emergency power for critical hardware such as LED emergency lighting, thus increasing system reliability and uptime.

b End devices can be monitored and managed: Network switches provide management tools such as the Simple Network Management Protocol (SNMP), which allows staff to manage the end devices, including power to the end device. You can remotely turn the device on or off, change lighting levels, colors, schedules, and monitor energy consumption.

b Moves, addition, and changes are easier: PoE allows for asier building renovations and rearranging of spaces since devices only need one ca?ble. It's easier to install devices on walls or ceilings and to setup temporary installations.

b It's an international standard: PoE is marketed and deployed worldwide, allowing manufacturers to avoid supplying different power cords for different countries, and eliminating the need for installers to worry about power cords. Manufacturers, contractors, building owners and designers can deploy a uniform solution around the world.

b Less high voltage is used in the building: PoE means that more low voltage distribution is used to power devices, and less high voltage is used throughout a building. This results in a safer environment and lower power consumption.

IT-based LED lighting systems can allow for additional sensors, such as occupancy, temperature, automated daylight harvesting based on ambient light levels, and passive motion sensors, with the data points shared with other building systems where 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 can be shared with other building systems.

The use of DC is important. In most buildings, including our homes, we are surrounded by devices and equipment that internally operates on direct current (DC). We plug these devices into a typical alternating current (AC) outlet, but the AC is then converted to DC, and 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 with DC generation now utilized in many newer structures, the addition of a DC LED lighting system adds to the consideration of distributed DC power in buildings and the maximization 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).

While the approaches to IT-based LED lighting systems are sound, they do come with a few issues:

b IT contractors can certainly install an IT system, but they are neither electrical nor lighting contractors. They will need training on installing lighting fixtures and handling stringer supports, mounting downlights in ceilings, or installing ceilings supports for pendant fixtures.

b 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.

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

b Light Emitting Diodes (LED) are semiconductors. They can be configured in an analog mode to be used primarily in older lighting systems, but new systems are likely to be all digital. Digital means an infinite number of colors, scenes, brightness settings, and control. IT-based low voltage LED lighting systems provide energy efficiency, long lasting LED lights, the use of DC power, the 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 best reflect the goals of the building industry regarding building control systems.

We typically don't think of the building's envelope as having much need for automation. However the fenestrations—specifically the windows— have a critical role in relation to energy related thermal loads and lighting in building spaces. The sun provides heat and light, and affects the thermal loads and lighting levels in building spaces. The comfort and productivity of the occupants is very important including thermal comfort and visual comfort such as brightness, glare, and shadows. Attention to windows has resulted in automation of windows and window shading devices.

< Prev   CONTENTS   Source   Next >

Related topics