Who: Minneapolis Department of Public Works
Project cost: $33 million
Break-even point: Five years, based on using less energy and deploying maintenance resources more effectively. Selling carbon offsets cuts payback time an additional 50%.
After years of delayed maintenance that left many streets in poor condition, Mayor R.T. Rybak launched “Access Minneapolis,” a 10-year plan that systematically reinvests in transportation to significantly reduce the city's carbon footprint.
Most plan projects are being funded with a $133 million grant from the U.S. DOT's Urban Partnership Agreement program. One involved completely redesigning and rebuilding 2.5 miles of downtown streets to move buses more efficiently, reducing emissions and enhancing safety by adding two bus-only lanes.
One requirement for urban-partnership funding is incorporating intelligent transportation technology into projects. So in addition to new streets, wider sidewalks, bus shelters, public art, and traffic signals, the city's department of public works is managing all the street lights in a 26-block radius using a “smart grid.”GETTING ONTO THE GRID
Defined by the Federal Highway Administration's Intelligent Transportation System (ITS) standard NTCIP1213, an electrical and lighting management system (ELMS) is an outgrowth of a system engineering process begun in 2003 to develop the user needs and features required in intelligent transportation electrical lighting and management systems. Eventually, the effort evolved to include roadway lighting control, ground fault detection, and revenue-grade power metering.
An ELMS of monitoring, controlling, and communicating electrical and lighting system parameters is accomplished by utilizing standards set by the National Transportation Communications for Intelligent Transportation System Protocol (NTCIP). This is a family of standards designed to achieve interoperability and interchangeability — otherwise known as “plug and play” — between electronic transportation control equipment from different manufacturers.
The protocol is the product of a standardization project led by the Joint Committee on the NTCIP, which is composed of members of the National Electrical Manufacturers Association, the American Association of State Highway and Transportation Officials (AASHTO), and the Institute of Transportation Engineers.
Last year, the U.S. Department of Energy (DOE) referenced ELMS as a standard to be supported in developing the nation's Smart Grid. The National Institute of Standards and Technology (NIST) references NTCIP 1213 in NIST Framework and Roadmap for Smart Grid Interoperability Standards as a “standard identified for implementation,” making ELMS projects eligible for the $100 million in matching funds available every year to states, utilities, and consumers through DOE.
The proposed reauthorization of U.S. DOT's surface transportation package specifically supports NTCIP 1213-compliant energy and safety applications.TOWARD ADAPTIVE LIGHTING
In Minneapolis, streetlights, electric meters, and ground fault sensors communicate real-time performance data including current, voltage, and power usage to field computers called “data loggers.”
The sensors send data via Zigbee wireless technology or over power lines using Echelon Corp.'s LonWorks networking technology (for more information, see “Control freaks,” page 40; PUBLIC WORKS December 2008).
Public works chose SmartLights software developed by Strategic Telemetry Inc. to display the data and allow engineers to monitor and set operational attributes such as extinguishing or dimming half of the street lights for half of the night. Performance parameters applied to these fixtures can be automatically overridden and commanded to full brightness from a traffic count sensor.
The department chose this first course of action — shutting off certain street-lights entirely — to extend asset life, minimize maintenance costs, and save energy. Lumen output levels of all lighting fixture technologies typically degrade up to 30% before repair or replacement. In effect, this means that from the day it's installed a new lighting system consumes up to 30% more energy and produces more light than necessary to achieve recommended minimum lighting levels.
An ELMS can command LED-equipped luminaires to “dim” — i.e., emit a fixed level of light over the life of the fixture —thereby eliminating overlighting and extending luminaire life.
Asset failures are automatically communicated to public works' 311 operators and field crews. Ideally, with prompt response from the service team, calls from residents regarding light outages, pole knockdowns, or electrical leakage conditions will occur less frequently.
The next step in the department's plan is to explore the potential of yet another protocol: NTCIP 1206.
Known as Object Definitions for Data Collection and Monitoring (DCM) Devices, this standard provides the vocabulary for commands, responses, and information necessary to monitor vehicle counts in real-time. Object definitions included in NTCIP 1213 support individual streetlight dim levels and performance characteristics.
Systems that comply with NTCIP 1206 and NTCIP 1213 use Simple Network Management Protocol (SNMP) network management software packages such as Hewlett Packard's popular Open-View suite to quickly configure system logic. This logic can retrieve traffic level; determine whether lighting is required at this traffic level; and send the appropriate on, off, or dim percent command to each circuit or individual fixture.
The standards' interoperability allows this integration with vehicle counts, as well as with other intelligent transportation subsystems including road reflectivity sensors and weather sensors. This integration of control allows engineers to illuminate roadways when traffic counts rise to levels at which AASHTO requires lighting, and allows quick extinguishment or dimming when vehicle counts fall below those levels.
— Frazer (email@example.com) is chief operating officer of Strategic Telemetry Inc., Pompano Beach, Fla.; Taillon (firstname.lastname@example.org) is manager of outdoor lighting services for Short Elliott Hendrickson Inc., Saint Paul, Minn.
Five advantages of ‘intelligent' assets
Telemetry-based advanced metering and real-time monitoring and control reduce long-term maintenance costs; enhance performance of streetlights, electric meters, and ground fault sensors; minimize liability; and implement lighting curfews to conserve energy and extend equipment life.
Other benefits of an electrical and lighting management system include:
Safety. Reduces the potential for electrical shocks to residents and employees because equipment faults are automatically detected and relayed.
Regulatory compliance. Conforms to national, state, and local laws as well as voluntary programs that improve quality of life by reducing light pollution and light trespass.
Labor efficiencies. Crews can correct outages before they happen, allowing departments to schedule maintenance much more effectively.
Energy use. Optimizes consumption by electrical and lighting devices through automated monitoring and control of devices, and implementation of light level reduction during hours of off-peak traffic levels.
All of these features can be expanded through coordination with other intelligent transportation systems such as traffic and weather sensors.