An intelligent digital controller can compensate for the main factors (LED ageing, temperature variations, LED manufacturing variations) that influence LED performance and light quality consistency i.e. color/intensity (Table 2).
Table 2: Factors influencing LED performance and light quality consistency
With an intelligent microcontroller it is possible to compensate for LED aging and to correct the color profile to ensure the light quality is consistent over the LED lifespan Changes in ambient temperature via a temperature sensor (low overhead function) and adjusting the LED drive to maintain light color/intensity. Also, the microcontroller can lower the light intensity or shut down LED strings if the temperature threshold is surpassed: the system monitors safe operation (and remotely communicates any problems) to ensure the lifespan of the LED is maximized.
Improved safety and efficiency
The intelligent digital controller can also improve safety and efficiency, particularly when combined with remote connectivity and sensors. Specifically, it can control when individual lights are turned off or dimmed depending on how the lights are being used. In a warehouse for example, occupancy sensors can be used to ensure that only the areas that are currently being used are illuminated, resulting in considerable energy savings. Similarly, intelligent street lighting can respond to the ambient light; turning on early in overcast conditions or remaining off for longer in bright conditions to save power.
Motion sensors can be used with a communication system to monitor evening/night traffic levels so that the street lights can be dynamically turned on and off in response to the traffic conditions. When the traffic is heavy the street lighting can be at full illumination, and when the traffic is light the street lighting illumination can be reduced, resulting in considerable cost savings. Taking the example in Figure 2, if the lights can be shut down for 25 percent of the time, this will lead to 25 percent energy savings ($68,218). Combining the savings of this intelligent operation with power supply efficiency savings, there is a substantial total annual operational saving of $101,844 (33 percent reduction).
An important feature of intelligent lighting systems is remote control. This facilitates significant improvements in quality and efficiency (and cost savings) via the automatic management of certain operations. Various remote operations, including dimming, shutoff and emergency control, are made possible by networking components and coordinating operations across the entire system. To maximize functionality, the lighting system must be able to communicate with a centralized controller. This will, for example, avoid having to adjust individual lights and allow the light intensity of the entire lighting installation to be altered from a central location.
In order to perform simple self-diagnostics, a two-way communication between each unit and the central operator is necessary. There are many established communications standards including DALI, DMX512, and KNX. This communication allows technicians to check the system remotely, and for maintenance to be initiated only when a problem has been identified by the system (i.e. a burnt out or poorly performing LED), reducing the need for scheduled maintenance. Technical problems can be identified immediately, ensuring increased operational safety. This can lead to significant savings in maintenance costs.
Several advanced features that improve efficiency and reduce operating costs are possible with remote connectivity. These include:
Dynamic control of multiple lighting installations from a single distant location Accurate tracking of power consumption Data logging of actual usage
Dynamic light control allows operators to make changes remotely to lighting schedules rather than sending a technician to the location e.g. making street light adjustments for daylight saving times. Unexpected or unscheduled lighting changes can also be made remotely. For example during a seasonal busy period in a factory the time the lights remain on can be extended temporarily, or roads can remain illuminated for longer in certain circumstances i.e. after a late-night music concert or sporting event. Direct control of street lighting can also improve safety during emergency situations.
Again, taking the street lighting example, where cities often pay a set fee for the power used to operate them, irrespective of usage, the ability to accurately track power consumption represents a major benefit and potential cost saving. An intelligent controller can measure the amount of power being consumed and communicate the data remotely to a central location. This ensures that only the actual amount of power used is paid for, which can lead to substantial savings.
The future planning of operating costs, maintenance resources, and investment is essential. Data logging of actual usage makes this task much easier and enables more sophisticated predictive diagnostics to be employed. Operators can be alerted to, and quickly solve, potential issues e.g. increased energy consumption or a rise in the number of replacement bulbs, therefore minimizing operating and maintenance expenditure.