A comparison of low-voltage and overlay lighting control systems. White Paper

Transcription

1 A comparison of low-voltage and overlay lighting control systems White Paper

2 Contents Executive summary 2 Comparison of low-voltage and overlay control systems 3 Installation and commissioning costs 5 Reliability 6 Performance considerations 7 Capabilities 8 Conclusion 10 1

3 Owners and lessors of U.S. offices typically spend over 40 percent of their total electricity bill on lighting 1. It is now possible to achieve up to an 80 percent reduction in those costs through advanced lighting control systems and LED lighting technology 2. Almost every lighting control system available today is an overlay system. An overlay system uses either a wireless or wired network to control ac line voltage powered lights. These systems are called overlay systems because the control network is overlaid on top of the existing ac lighting power infrastructure. Low-voltage lighting control systems, in contrast, supply an intelligent low-voltage network that both powers and controls LED light fixtures in a single system, in addition to providing building intelligence. This eliminates the need for costly and inflexible line voltage installation and provides a far more efficient lighting system. This paper compares low-voltage lighting platforms to overlay systems and demonstrates their higher energy savings (averaging 75 percent), lower installation cost, flexibility to offer a broader range of functionality, and their enhanced ability to scale in larger deployments. Executive summary Many trends have recently emerged that are resulting in the increased availability and adoption of lighting control systems in office spaces. Although lighting control systems for offices have been available for over a decade, only in the past few years has there been a marked increase in the number of available solutions, due in part, to the following trends: Increasingly stringent building codes Utility incentives Rising electricity costs Growing environmental awareness LED lighting Office lighting control systems can be categorized based upon their capabilities and communications methods. Capabilities can span from deployments of discrete dimmers and closed-loop occupancy sensors to robust and centralized control systems providing occupancy sensing, daylight harvesting, light scheduling, dimming, and a host of other functions. Communications methods can be categorized as low-voltage, wireless overlay, or wired overlay as summarized in Figure 1. Lighting Control Types Low-voltage Wired Overlay (Wired and Wireless) Wired control network integrated with low-voltage dc power infrastructure Wired or wireless control network manually connected to independent ac line voltage power infrastructure Figure 1: Lighting control types Other 8% Space Heating 3% Ventilation 8% 1 - According to the Energy Information Administration, Commercial Buildings Energy Consumption Survey 2 - According to measured energy savings from Redwood System clients averaging 75% and ranging up to 92% 2

4 This white paper examines the different capabilities, trade-offs and applications of both low-voltage and overlay lighting control systems. The conclusion is that low-voltage controls are superior for applications that require a reliable and highly efficient controls solution, with measurable lighting electrical load savings of 75 percent on average, and the ability to scale across multiple commercial buildings over the enterprise. Low-voltage and wired overlay solutions are better suited for environments that are sensitive to noise, those that have high security safeguards, or those where lighting is mission critical to the tasks being performed. Wireless overlay systems on the other hand, may be suitable for smaller, non mission-critical areas or for applications where accessing wiring spaces is cost prohibitive. Comparison of low-voltage and overlay control systems Lighting Control Types Low-voltage Wired Overlay (Wired and Wireless) Wired control network integrated with low-voltage dc power infrastructure Wired or wireless control network manually connected to independent ac line voltage power infrastructure Space Heating 3% Ventilation 8% Other 8% Cooling 14% Lighting 44% Figure 3: Diagram of a wired overlay control system 24% Figure 2: 44 percent of U.S. office electricity consumption is from lighting (Source: EIA) Both low-voltage and overlay control systems are comprised of lights, sensors, a dashboard enabled device 3, and an interconnect medium. Low-voltage systems, as defined in this white paper, use a wire based communication protocol whereas wireless overlay lighting systems use a network of radio transceivers for communications. Wireless overlay controls and sensors connect to the lights using a separate wireless communications network. In these systems the ballast or driver is located either inside or nearby the light fixture. Wired overlay control systems (Figure 3) are also using line voltage ac wiring and a separate wiring network for controls. 3 - This is any device such as a PC, laptop, or handheld phone that enables programming and control of the lighting system 3

5 Cat. 5e/6/6A cable Redwood Sensors Patch Panel Redwood Engine Redwood Dimmer Figure 4: Diagram of a low-voltage system: the intelligent lighting network solution from CommScope s Redwood portfolio A low-voltage wired system such as the the Redwood intelligent lighting network solution from CommScope is not an overlay system*. The solution (shown in Figure 4) provides both power and control to the lighting fixtures exclusively over low-voltage wiring, without the use of line voltage ac wiring. Today, the installed base of low-voltage and wired overlay control systems is significantly higher than wireless overlays. This trend is expected to continue due to a number of advantages associated with wired systems. CommScope believes that among wired systems, the advantages of low-voltage control systems will result in a larger trend toward non-overlay systems. The differences in wireless overlay, wired overlay and low-voltage system approaches result in a significant disparity in terms of installation costs, measurement ability, reliability, performance and scalability. The different communication methods of each system can impact its suitability with respect to specific commercial environments and needs. Figure 5 (next page) presents a summary of the topologies and attributes of these three different lighting control systems. * The Redwood system has been deemed SELV (Safety Extra Low Voltage) under IEC

6 Lighting Controls System Wireless Overlay Topology Wireless control network manually connected to independent ac line voltage power infrastructure Attributes - Required licensed electrician - Costs more to install/recommission than low-voltage wired system - Subject to radio interference, latency and bandwidth contention - Minimal install base limited to smaller scale deployments Wired Overlay Wired control network manually connected to independent ac line voltage power infrastructure - Required licensed electrician - Costs more to install/recommission than low-voltage wired system - No radio interference, latency or bandwidth contention Low-Voltage Wired Wired control network integrated with low-voltage dc power infrastructure - Enables simple, low-cost install using low-cost wiring - No radio interference, latency or bandwidth contention - Scalable for mission-critical performance across enterprise - Measured energy savings - Centralized driver enabales improved thermal management - Average energy savings of 75 percent compared to fluorescent options Figure 5: Lighting control systems topology and attribute comparison Installation and commissioning costs Overlays, whether wired or wireless, require traditional line voltage installations by licensed electricians and must use conduit, junction boxes, relays and separate dimming ballasts for legacy fluorescent fixtures. Some overlay systems require their controllers to be integrated into the lighting fixture, potentially voiding the lighting manufacturer s warranty. Figure 6 shows the difference in installation costs for traditional line voltage ac cabling compared to low-voltage wiring 4. Lighting can use less expensive low-voltage installers from either licensed electricians or low-voltage contractors. For new construction environments or major renovations where existing light locations need to be changed, wiring installation costs can be reduced by over 90 percent. In addition, the energy and maintenance savings associated with LED lighting can be realized over the typical 10-year lifetime of LED fixtures. Commercial LED light fixture prices are dropping dramatically, enabling payback periods of between one and five years. 4 - Prices shown are from contractor quotes gathered by Redwood Systems 5

7 Rigid Conduit with AC Line - $8/ft Flex Conduit with AC Line - $6/ft Low Voltage Wire - $0.25/ft Figure 6: Wiring installation costs Reliability Wireless overlay systems are subject to radio interference and bandwidth competition. Interference sources can include nearby wireless networks, electrical equipment, radio and television stations, amateur radios, citizens band radios and power lines. Although safeguards have been put in place in the design of wireless overlay systems, bandwidth competition can still occur between different wireless networks, resulting in higher latencies or possibly errors. In particular, there is broad spectral overlap between 2.4GHz wireless controls, including the IEEE based Zigbee standard, and commonly deployed Wi-Fi networks. The RF spectrum plot shown in Figure 7 is a graphical plot showing how much energy and at what frequency a radio operates. The X-axis shows frequency and the Y-axis is the RF energy. Because Zigbee and Wi-Fi use spread spectrum, they do not operate at a single frequency; rather they occupy bands of frequencies, which are shown by the different arches in the diagram. Wi-Fi channels are wider in frequency than Zigbee, and therefore utilize more RF spectrum per channel. Note the almost complete overlap between channel spectra. Figure 7: Spectrum overlap of 2.4GHz Zigbee and Wi-Fi 6

8 Although the Zigbee alliance has spent much time and effort implementing coexistence features such as spread spectrum signaling, the allocation of 16 non-overlapping FDMA channels, CSMA schemes, and multi-path communication capabilities, there is no guarantee of noninterference. In addition to Wi-Fi networks, there are a wide variety of other interference sources including cell phones, Bluetooth headsets, WiMax networks, microwave ovens and security cameras, to name a few. Interference and competition for bandwidth in wireless overlay control systems may cause signals to become corrupted, significantly delayed, or unable to be received, introducing erroneous control or sense information into the network. These errors may result in malfunctioning lights, or lights turned on or off regardless of the state of occupancy. Loss of productivity and repair costs may ensue. There is also the possibility of intentional interference with the lighting control system too, which could result in significant loss of productivity or possibly pose a safety issue. For office environments requiring a high degree of security, centralized wired lighting control systems provide dependable, low-latency communications that do not compete for bandwidth and are not subject to radio interference. Secure commercial environments might include corporate headquarter buildings, federal government or government contractor offices, data centers, laboratories, medical offices, hospitals, security agencies, defense agencies or defense contractors offices, city halls, municipal offices, fire and police stations, airports and other commercial office areas. Performance considerations Most overlay control systems employ a mesh or repeater-based topology. Although these topologies can enable lower transmitter power and multi-path signal propagation, they can also incur a latency penalty. In some cases, control signals can take up to 3 seconds to reach their intended receivers, creating a very noticeable delay in light functions. See Figure 8 for a graphical description. A C B Figure 8: A control signal travelling through a mesh network may incur greater than one-second latencies 7

9 Systems employ centralized and remote power supply racks that are located in utility closets, away from the LED lighting fixtures. By centralizing the power supply, fan cooling can be conducted, which is not inside the fixture due to the creation of audible noise in the work environment. Inclusion of a fan in every light fixture would prove cost prohibitive. Fan cooling ensures that the power supplies and their heat-sensitive components, such as transistors and capacitors stay well within their thermal ratings. When power supplies are integrated within the LED fixture, operating temperatures can sometimes exceed maximum ratings resulting in reduced fixture lifetimes, diminished light output, or even worse, early failures. Another benefit of the centralized and remote power supply is the reduction of multiple points of failure to one, enabling service in one, non-disruptive location: the utility closet. Care must be taken when evaluating the energy efficiency potential of control systems. For example, to save on equipment and installation costs, some controls vendors may recommend applying a sparse network of sensors with controls applied to clusters of lights. In these cases, fine-grain dimming is compromised and the energy savings will not be as substantial as having individual sensors and controls associated with every light. These implementations are also harder to commission and recommission if the space is repurposed. Capabilities It is beneficial to implement the lighting system to employ sensors not only to detect occupancy, but also to directly measure power usage and temperature. Direct measurement of power enables the quantification of actual energy savings. The ability to detect temperature enables the integration of the lighting system with HVAC controls, to modulate heating based upon both occupancy and temperature. Best practice is to request and carefully review documented case studies to verify energy savings claims. A number of controls systems providers have not established long track records and do not have sufficient data to back-up their claims. In many cases, these vendors will produce reports that are based upon estimates as opposed to hard data collected by the system. If the provider does not have a system capable of granular power measurement, actual energy savings cannot be reported. Systems capable of gathering real-time energy usage and historic reporting are superior for this reason, and in the case of CommScope s Redwood intelligent lighting network solution, can easily validate its industry-best average of 75 percent in lighting energy savings. In fact, a recent analysis of five customers showed that lighting energy could be reduced by 75 to 93 percent from a preexisting baseline 5. Overlay systems, because they do not directly supply the power to the fixtures, must rely upon estimates instead of actual measured energy consumption. Aesthetics are another consideration when evaluating systems. Many systems use large, saucer shaped sensors that protrude from the ceiling or from suspended fixtures. They often are a different color from the ceiling or fixture and are unsightly. Control systems that take advantage of the latest sensor technology and employ aesthetic design techniques provide discrete sensors that are installed almost flush with the ceiling, or that are well integrated into suspended fixtures. 5 - Refer to the Energy Savings Case Study Paper Aug 2012 for more information 8

10 Lighting control systems should be easy to integrate with other systems, including building automation systems, HVAC control, conference room scheduling software, or custom reporting dashboards. Ease of integration not only results in reduced commissioning costs, but also enables new capabilities that increase energy savings and improve productivity. When integrated with HVAC systems, lighting system sensors can provide data that can be used to turn off heat or air conditioning to unoccupied areas, or modulate their output based upon more accurate and granular temperature measurements. Occupancy sensors can also provide real-time occupancy data to conference room scheduling systems, enabling workers to quickly see on a visual map which rooms are available. An easy to use, fully featured web-based API and/or BACnet protocol support can significantly facilitate integration. Although low-voltage and wired overlay systems have significant advantages over wireless overlay systems, there are applications where a wireless overlay system may be more suitable. In projects where there is very limited capital budget, lighting quality and degree of control are less important, and sustainability is not a factor, wireless overlay solutions may be more appropriate such as with garage retrofits. In such cases, ensure that the costs of commissioning and maintenance are included in the budget. Attribute Low- Voltage Wired Overlay Wireless Overlay Benefits Occupany, daylighting & dimming controls Provides baseline energy savings capabilities Zero bandwidth contention Higher performance improved reliability No radio interference Improved reliability Enables mission-critical operations Low latency Reduces delays Installed base of numerous 250K+ sq ft deployments Track record of enterprise level scalability Exclusively low-voltage Low installation cost Easy to recommission Centralized power source Better thermal management Measured energy savings Reports actual savings No estimations required 75% average energy Figure 9: Lighting control systems - comparison of benefits Industry-best average savings savings on electrical load 9

11 Conclusion Low-voltage control systems have superior benefits for commercial spaces being newly constructed or that are undergoing renovation that desire a reliable, highly energy efficient controls solution. In particular, Low-voltage solutions, such as the CommScope s Redwood intelligent lighting network solution shown in Figure 9, offer the advantages of low installation cost, easy recommissioning, better thermal management, low latency, superior reliability, increased scalability and an average of 75 percent energy savings on lighting electrical load. Wireless overlay systems, on the other hand, may be suitable for smaller, non-critical environments, or for areas where the installation of low-voltage wiring is not possible. Visit our website or contact your local CommScope representative for more information CommScope, Inc. All rights reserved. All trademarks identified by or are registered trademarks or trademarks, respectively, of CommScope, Inc. This document is for planning purposes only and is not intended to modify or supplement any specifications or warranties relating to CommScope products or services. WP EN (05/14)