Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
8 Chapter 2 â Lighting Master Plan Current Guide The current AASHTO guide discusses the benefits of preparing a lighting master plan and offers general guidelines for plan implementation. The guide defines a lighting master plan as a formal arrangement between local governments and other entities within a region to coordinate and standardize the design, operation, and maintenance of public lighting. Master lighting plans can include lighting curfews and emerging electronic monitoring and control systems. Benefits of a master plan include: â¢ improving safety through the maximizing resources â¢ improving traffic flow â¢ improving driver comfort/confidence â¢ reflecting a consistent image of the local culture and tastes â¢ identifying the nature of the site (e.g., residential versus ârestaurant rowâ) â¢ managing energy use â¢ controlling sky glow and light trespass â¢ implementing lighting curfews â¢ increasing public security (other concerns may warrant immediate turning on or off) â¢ standardizing design choices â¢ coordinating maintenance â¢ coordinating maintenance specifications, such as poles, breakaway devices, and luminaires Although the 2018 AASHTO guide outlines what to consider in a master plan and the recommended participants in the process, it does not include specific considerations for SSL. SSL systems bring specific benefits and versatility to master plans and help to optimize their benefits. This chapter discusses some of those key benefits and considerations related to master planning. Considerations for Solid State Lighting Standardization of Lighting Equipment When considering implementing system-wide SSL, a benefit of the master planning process is evaluation and standardization of products to limit maintenance costs and quantities of spare parts required to keep the lighting system operational. Full system implementation generally results in a palette of products that address the needs of the lighting system often including roadway luminaires of several outputs, underpass luminaires, ornamental luminaires, pedestrian scale luminaires, and a few specialty products. Standardization however does need to be balanced with product performance for the specific installation. Maintenance benefits can sometimes be offset by improved initial performance. SSL luminaires involve added complexities because each product, even if its intended use is the same, can vary greatly between manufacturers. Often, when comparing luminaires, the luminaire classifications is Standardization of lighting products can offer maintenance, purchasing, and aesthetic advantages, varying by owner and location.
9 used to group fixtures. In Figure 6, each of the photometrics is classified as Type II, Medium Longitudinal Distribution, and both have a Backlight-Uplight-Glare (BUG) rating of B4-U0-G4. Their photometric attributes, , are quite different, and resultant roadway lighting levels, uniformity, and glare can vary by 30%. LED products vary more than HID products, which require performance-based comparative methods rather than classification-based ones. Another option is the pre-qualification of specific luminaires based on a performance comparison of typical lighting layouts. Note that pre- qualifications like these must be updated periodically because of frequent product advancements and production modifications. Figure 6. Comparison of Similarly Classified Luminaires Expected Life As noted in Chapter 1, the life expectancy of an LED is based on its lumen depreciation. Other solid state components within the fixture-like drivers also have an expected life, which often depends on the heat management in the fixture, product design, internal components, quality control, etc. IES LM- 80(Illuminating Engineering Society, 2015) prescribes the methodology for determining the estimated life of LED luminaires. The methodology contained in this guide can be used to compare different luminaires and set criteria applicable to the DOT or authority based on area climate conditions, life expectancy needs, and other factors. Product failure rates can be determined by MTBF analysis provided by the manufacturer. Product failure rates can then be determined by analyzing these factors. Adaptive Control Technologies The ability to easily control and dim LED luminaires is one of their biggest advantages over other roadway lighting sources. Dimming LED luminaires can result in additional energy savings of up to
10 30%(Avrenli & Medina, 2012). The concept of dimming roadway lighting during periods of low vehicular and pedestrian activity is called adaptive lighting. Adaptive lighting control can be key to reducing the impact of an exterior lighting system on sky glow, glare, and light trespass. Although it is considered an emerging technology, it has already been effectively applied. The purpose of an adaptive lighting control system is to reduce the impact of the lighting system and save a considerable amount of energy and maintenance costs. The benefits of adaptive control can be quite different when used for highway lighting compared with street lighting and are quantified based on roadway type. Systems Roadway lighting control systems are information sharing systems that allow for both the production and consumption of data. Data can be used for energy analysis, maintenance planning, and identifying environmental conditions and system status. Data consumption activities include dimming, time-of-day control, and remote control of the lighting system. These data activities can then be divided into three functional categories: monitoring, control, and sensing. Monitoring â Ongoing data acquisition of system components â¢ Energy usage â developing a pattern of energy consumption for the lighting system allows for predictability and analysis. â¢ Operational duration â Tracking time-of-day system start-up, run time, and expected life allows for planned, preemptive rather than reactive, maintenance. â¢ System status â Provides constant updates of luminaire performance parameters. â¢ Fault notification â Interruptions in expected operation parameters create notifications and/or alarms based on severity with this also giving an accurate location of fault via global positioning system (GPS) chips within the lighting fixture control node. Control â¢ Switching â Energizing, some or all system luminaires based on time-of-day, photocell, or other scheduling criteria. â¢ Dimming â Modulating luminaire light output for energy consumption, adaptive lighting, and lumen maintenance. â¢ Constant light output (CLO) â varying luminaire output based on lumen depreciation. Sensing â¢ Internal ambient conditions â temperature detection within the luminaire can prevent failure of LED light engines. â¢ Illumination levels â current lighting conditions on the roadway through illuminance and/or luminance measurement will allow for real-time adjustment of luminaire light output. â¢ Environmental conditions â traffic data, outdoor air quality, and weather data can be obtained. â¢ Motion detection â IR, occupancy and eventually direct short range communication (DSRC) in connected vehicles. â¢ Other data can be mined with the addition of various sensors. Adaptive lighting controls save energy and extend equipment life but have their own maintenance requirements. Use depends on owner and needs.
11 These technologies are very new and have been developed by suppliers based on a perceived need with few standards and closed protocols. Although standardized protocols are being developed that will lead to interoperability between products, most systems are not yet compatible with others thus locking the owner into a specific product unless additional levels of control/software are added. Communication Protocols Communication protocols are a set of rules governing how messages and data elements are encoded and transmitted between electronic devices. The equipment at each end of a data transmission must use the same protocol to successfully communicate. The protocol is very much like human languages that have alphabet, vocabulary, and grammar rules used by everyone speaking that language. With a proprietary standard, the manufacturer owns the protocol, and the owner will be committed to a single manufacturer. Another downside of a proprietary protocol is that, if the product is discontinued or updated and is not supported by the manufacturer, then operational issues may result. Questions as to how the product will be supported if it is discontinued should be addressed along with the longevity of the manufacturer because systems are not yet interoperable. Open standard protocols allow owner control and the potential for interoperability between systems. Open protocols are updated and developed on an ongoing basis. Monitoring Center For networked controls, data from the luminaires will be collected and analyzed in a communications or monitoring center. Systems may be supplied where the data are stored and managed by the supplier via cloud networking and accessed via a web browser or perhaps stored and managed on the ownerâs network system. The cloud is where all computing resources (hardware and software) are delivered as a service over a network (typically the Internet). A decision would need to be made whether the owner wants a system that it would manage and have full control over or a cloud system that, once installed, would require no further internal resources to manage. Centrally hosted systems are typically web based with a secure login (user ID and password). Data from the control network are processed by a service provider at a central location. The cost of hosting is often scaled to suit the overall size of the system. IT infrastructure, upgrades, and support resources are often provided as part of service. Ongoing service fees (often charged) must be considered. Customer-hosted systems are typically located on the customerâs network. Servers, databases, and networks are owned and maintained by the customerâs IT resources. Upgrades and support are provided on a version-specific basis. Security concerns and ongoing service fees are thus minimized. When considering a customer-hosted system, firewall requirements and system integration should be part of the early discussions with the customerâs IT group. Networks Networked control systems conceptually consist of three interacting component sets: field devices, network infrastructure, and a central management system (CMS) (Figure 7). Although the component sets contain different types of physical devices, information is shared across the entire system. Lighting control networks can be either wireless or hard wired. Field devices always include controllers, which necessarily consume data to implement some control function according to internal programming and may also include sensors, which produce data. Multiple controllers often route data through gateways, which at a minimum act as communication bridges to outside networks but may also communicate (via cellular) directly to the CMS. Field devices may be
12 accessed and managed remotely by a CMS that consolidates and stores retrieved data and will facilitate user interaction through graphical user interfaces (GUIs), consolidates and stores retrieved data. CMS communicate to field devices through network infrastructure, consisting of one or more backhaul communication networks that may take various forms (e.g. wired, wireless, powerline communications [PLC]). Figure 7. Major Components of a Wireless Outdoor Lighting Control (Image Credit: California Lighting Technology Center, UC Davis) Network Infrastructure Wireless roadway lighting controls make use of three network topologies: mesh, star, and point-to-point (Figure 8). The point-to-point network is a component of the others, creating a bridge between network gateways or routers. Limiting factors become distance; line-of-sight; and information density, or capacity, which are resolved through frequency and network communication protocols. The frequencies used by wireless networks to communicate between the gateways and nodes are specific to the system. Some technologies offer ranges upwards of 10 miles, but most operate at significantly shorter distances.
13 Figure 8. Network Topologies Communication between the gateways and a CMS are either hard wired into the communications infrastructure or use cellular communications. In all situations, security and continuity issues of the control system must be robust and redundant. Wireless Star Network A star network is an implementation of a spoke-hub distribution paradigm found in computer networks. Messages on a star network pass through the hub, switch, or gateway before continuing to their destination. The gateway manages and controls all functions of the network. It also acts as a repeater for the data flow. The star topology reduces the impact of a line failure by connecting all systems to a central node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected. Wireless Network Security Effective control systems require multiple levels of network security, as shown in Figure 9. Figure 8. Network Security Levels Hardwire Powerline Carrier
14 PLC is a communication method that uses electrical wiring to simultaneously carry both data and alternating current (AC) (Figure 10). PLC is also known as power-line carrier, power-line digital subscriber line, mains communication, power-line telecommunications, or power-line networking. Figure 10. Powerline Communications A wide range of PLC technologies are needed for different applications, ranging from home automation to Internet access which is often called broadband over power lines. Typically, transformers prevent propagating the signal, which requires multiple technologies to form very large networks. Several difficult technical problems are common between wireless and PLC, notably those of spread- spectrum radio signals operating in a crowded environment. Radio interference, for example, has long been a concern of amateur radio groups. This is resolved using dedicated frequencies under which control systems operate. Wireless Mesh Network A mesh network is a network topology in which each node relays data for the network. This allows for redundancy and multiple pathways between the controller and the light sources or other sensors back to the gateway. Mesh networks take advantage of having many points of contact in proximity to one another allowing messages to be relayed using either a flooding technique or a routing technique. With routing, the message is propagated along a path by hopping from node to node until it reaches its destination. To ensure all its paths' availability, the network must allow for continuous connections and must reconfigure itself around broken paths, using self-healing algorithms such as Shortest Path Bridging. Self-healing allows a routing-based network to operate when a node breaks down or when a connection becomes unreliable. As a result, the network is typically quite reliable, because there is often more than one path between a source and a destination in the network. Wireless Broadband Technologies
15 Broadband technologies are typically either 3G/4G cellular (and entering 5G) or wi-fi types of systems. These types of systems offer direct cloud-based communications to the system controller and are sometimes considered when looking at urban networks investigating Smart City technologies where a large amount of data must be transmitted and shared networks are considered. Cellular systems are also considered for remote areas where data networks are not available. Control System Limiting Factors Review of the constraints in the various network topology yields the following observations: â¢ Powerline systems provide good results when on closed or proprietary distribution systems (e.g. tunnels) and are generally high security. â¢ Star networks offer long distances but can require additional centralized distribution gateways in large areas. â¢ Proprietary networks generate ongoing operational costs, beyond those required for system maintenance, and are dependent on vendor technology and continued corporate financial stability. With the increased cost, comes increased signal reliability and network security. â¢ Mesh networks provide multiple pathways for data transfer, optimizing response time and balancing information flow across system. â¢ Hybrid network topologies take advantage of the long distance node to gateway relationship where line of sight (LOS) is unobstructed and mesh relationships in areas where LOS distances are limited by obstructions. Fewer gateways are required for the hybrid system as a result. â¢ System commissioning requires each unit to identify itself and be tied to a specific location for asset management. Connection nodes having GPS can self-locate simplifying the commissioning process regardless of network protocol used. Review of the constraints inherent in the method of communication yields the following observations: â¢ Powerline carriers can be hampered by both continuity and fidelity issues that are the result of broken connections/splices and interference ânoiseâ (motor starts, ups, transmission harmonics) masking the carrier signal. â¢ Networks working on RF bands are limited in distance to line of sight. Those using the 2.4 Ghz are additionally subject to interference from other wireless networks as this is the frequency of most wireless and streaming services. â¢ Cellular based networks can remove the need for gateway but are subject to the limitations and additional costs of cellular access. Measuring Power Usage Taking advantage of power saving from dimming lights through adaptive controls can help offset system costs. Many roadway lights in North America are supplied power on an unmetered (flat rate) basis. For unmetered roadway lights, some adaptive systems could provide an accurate measurement of power consumption. The power consumption monitoring of these adaptive systems should, however, not be confused with a âutility grade meter,â which may have very specific regulatory requirements and recalibration requirements that go beyond the capability of an adaptive system.
16 If accepted by power utilities as an accurate means to measure power consumption, owners could be billed for power used, taking full advantage of energy saved. The use of power consumption measurement as part of adaptive controls could put an end to the shortcomings of the flat rate system and make the full financial benefits of dimming available to owners. Issues will include accuracy of the power consumption measurement system (defined by utility and their regulatory body), audit process, who maintains the data, and questions related to how data is presented and used for billing. The use of roadway lighting power consumption measurements as part of an adaptive control system will need to be discussed and agreed upon by the local power utility. A typical power measurement system may require re-calibration and validation via utility grade check meters. Even if not acceptable to the local utility, power consumption monitoring can be used to track power costs for comparison to utility flat rate billing. Smart City Integration Selection of an adaptive lighting system framework will generally be a balance between needs and cost. These systems, however, are part of the framework of Smart City technologies and will need to be integrated into the Autonomous and Connected Vehicle framework that those systems enter use. Some authorities are considering communications/data backhaul networks to incorporate various systems on a single network. Others are looking for available bandwidth on adaptive control networks for connecting Internet of Things (IoT) devices that may not have large bandwidth requirements depending on their function. The selection of the best technology should consider not only the lighting needs but future ITS, A/CV, and monitoring systems. Key Issues for SSL to Consider in a Lighting Master Plan â¢ Select an adaptive lighting technology that meets the needs of the project in terms of operations, maintenance considerations, and future needs. â¢ Investigate integration and shared use with Smart City, ITS, C/AV, and IoT devices. â¢ Select a palette of luminaires that meets the needs of the project in terms of color, glare, luminaire/pole style, maintenance, aesthetics, and roadside safety. â¢ Standardize products and, where possible, reduce inventory. â¢ Consider maintenance and operations limitations. â¢ Identify areas with environmental sensitivity. â¢ Evaluate the development of adaptive lighting through dimming and CLO. â¢ Consider metering of power consumption within energy provider regulations. â¢ Consider in-house IT structures and systems compatibility and develop a long-term IT planning strategy.