Digi Cellular Router Reduces Streetlamp Power Consumption
Hafslund is Norway's largest supplier of electric power and security, managing streetlights for local councils throughout the country. When government legislation required that all streetlamps containing polychlorinated biphenyls (PCBs) be replaced, it was the ideal opportunity to upgrade the streetlamp control systems. With this in mind, a new intelligent, energy-conscious project was started to find a way to monitor and control streetlamps remotely.
A state-of-the-art monitoring and control system requires reliable and cost-effective communication. GPRS was the best solution for communications based on coverage, cost and installation flexibility. Hafslund's goal was to reduce the considerable amount of power consumed by lighting roadways, as well as to increase the lifespan of the bulbs to lower maintenance costs.
More than 100 Digi TransPort GPRS cellular routers communicate with 80 to 100 streetlamps, each through an intelligent concentrator head end unit that is connected directly to the power lines from which each lamp feeds. The GPRS network is built using a private APN provided by Telenor Mobil, Norway's leading mobile operator. The Digi TransPort router detailed information about power consumption, bulb life expectancy and failure via its GPRS facility back to Hafslund's head office.
To maximize efficiency, streetlamps have been programmed to reduce their output at times when less intense lighting will still provide a good level of visibility. The system achieves this by constantly comparing the input it receives with a pre-programmed scenario and sending alarms via the GPRS.
The system also has the option to network with motion sensors that actively detect when there is no traffic and consequently no requirement for normal lighting levels. In this instance, the system signals the head end unit (which controls power levels) to reduce power levels on the appropriate lamps. This in turn instantly reduces the levels of lighting to conserve energy. Similarly, as soon as the motion sensor detects traffic again, a signal is sent to increase the lighting level.
As an energy conservation and cost savings exercise, this project has shown a 62-64% reduction in power consumption. The Digi TransPort GPRS routers provide reliable communications compared to conventional systems that just need to turn lamps on/off. Hafslund plans to apply this winning formula on a larger scale.