ENVIRONMENTAL AND ENERGY SAVINGS WITH
GREENSTREET
Studies show that changing to modern luminaries, effective lights with controllable electronic ballast combined with a system for “intelligent street lighting” can result in reduce as much as a 65 percent reduction in energy consumption. Generally, the reduced energy consumption stems from dimming lights to levels sufficient for the circumstances. Below are some examples of how significant energy savings can be achieved from different scenarios. The requirements for lighting levels depend mostly on conditions such as daylight, traffic intensity and weather conditions. These are conditions which vary throughout the day depending on time, season and location. The following generalised example based on pre-defined times with changing lighting levels works to show some of the opportunities. The example is built based on real data where the lighting under certain conditions can be to high, - or worse - too low. However, we’d like to point out that while the use of fixed lighting levels under pre-defined times is a good start, but not an optimal solution.
INSTEAD OF LETTING THE LIGHTS BURN 100% UNDER THE PREDEFINED PERIOD THE LIGHTING IS DIMMED… Energy consumption without dimming: 600 000 kWh When a lighting system is modernised it is rarely an optimal configuration. The most common power levels are 50W, 70W, 100W, 150W as well as 250 W. As there is frequently not a comparable lighting source a light with a higher power is often chosen. Through having a dimmable system, this excess power can be compensated for through consistently dimming surplus lighting and at the same time meet lighting requirements. This is done in conjunction with operational configuration and is mostly handled automatically by the system. DIMMING BASED ON TRAFFIC CONDITIONS
Assumtions
Number of lights:
1000
Lamp power:
150
Burning time
4000 (620 h+ 620 h+ 2760 h)
Dimming levels:
100%, 70%, 35%
Energy consumption with dimming: 308 000 kWh
Total annual savings: 292 000 kWh (appro49 %)DIMMING AS COMPENSATION FOR EXCESS POWER
The strength of a light is reduced with age, which is why lighting systems are built to give appropriate lighting levels at the end of the life of a lighting source. This can result in new lamps being intentionally stronger than required, and providing too strong light during the first years of the life cycle. Depending on the luminaries, lighting source and the age of the lighting source, it can give as much as 20 percent too much light in the first year. By using a dimmable lighting system, this excess power can be taken into consideration to create a constant lighting level over the entire burning time of the lights. A time adjusted dimming configuration results in significant economic savings even without adjusting the lighting levels according to external conditions. In addition to the above example, by converting cost savings resulting from reduced energy consumption to tonnes of carbon dioxide, dimming results in environmental benefits. There is a number of advantages which have a direct impact on the environment. Some of the most prominent are: In a city environment there is sometimes what is called light pollution. Light pollution means that public outdoor lighting is experienced as disruptive by the people who live close to the lighting source. By using individual dimming, the lighting strength of chosen lights can be adapted at particular times of day to acceptable levels. In addition to the positive impact energy savings have on the environment, the increased burning hours from each individual light reduce the frequency of light changes, which in turn also result in reduced environmental impact. It also contributes to a positive environment and maintenance as the burning hours of the lights are increased and light pollution is reduced. The lighting requirements are not the same in fine weather with dry road conditions and low traffic intensity. Through using vehicle traffic counters, detectors for weather and slippery conditions, the system can be further optimised for energy savings and increased safety. DIMNING FÖR ATT FÖRLÄNGA LAMPANS LIVSLÄNGD
ESTIMATED LIGHTING REDUCTION
The diagram shows the light reduction curve for a HPS light. To meet the required 14.000 lumen at the end of the life of the lap, the light must average roughly 16.000 lumen at the start. The inefficiency of the “excess lighting” is represented by the green triangle in the above diagram. Through “dimming away” this excess lighting a saving of up to 15 percent can be achieved for a 150W HPS light.
DIMMING TO ACHIEVE POSITIVE ENVIRONMENTAL SAVINGS