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Biel Hospital Centre, Switzerland: Presence-dependent lighting control and LEDs reduce energy consumption by 82 percent

The circulation areas of the Hospital Centre in Biel, Switzerland, were originally conventional lighting using compact fluorescent lamps in continuous operation and have been refitted with Ledvance LED panels and Theben presence detectors. Every presence detector controls lighting groups with 2-4 LED lamps in each. The result: an 82% energy saving compared to the previous lighting, with an increase in lighting strength from 40 to over 200 lux. 54% of these savings can be attributed to presence-dependent lighting control.

Task

  • A sustainable reduction in the energy consumption of the lighting

 

Solution

  • Presence-dependent lighting control by using Theben presence detectors
  • LED panels instead of conventional compact fluorescent lamps

In Switzerland, 8 billion Swiss francs are spent on electrical energy every year. Around 12 percent of this is for lighting, which corresponds to 7 billion kilowatt hours. Thanks to efficient LED lamps, effective sensors and optimum daylight supply, electricity consumption for lighting can be reduced by at least 50% – with a simultaneous gain in light intensity and comfort.

Based on the "Davos Light Agreement" in September 2018, the SLG (Swiss Light Society) together with numerous partners launched the "energylight" programme. In the context of "energylight", projects are realised that contribute to the use of the large energy saving potential in lighting (3.5 TWh/a).

Case study: Biel Hospital Centre

The Biel Hospital Centre is one of 6 case studies in the "energylight" project "SensoLight". The aim is to demonstrate the effective energy-saving potential of intelligent lighting systems compared to conventional lighting with standard sensor technology and to prove this metrologically. An earlier measurement in a parking garage in the city of Zurich showed an effective saving of over 90%.

As part of the "SensoLight" project, case studies will be carried out from various applications that are of particular interest for intelligent lighting. This includes parking garages, circulation areas in residential buildings and care facilities, classrooms, industrial halls and other types of buildings. The results of the case studies will be summarised in a report and guide for planners and used as a basis for information events and training. The association of sensor manufacturers sensNORM is a partner of the "SensoLight" project.

The circulation areas of the hospital centre in Biel were refitted from conventional lighting with compact fluorescent lamps in continuous operation to LED panels with sensors and very short time delays. For the measurement, a corridor in the basement of 352 m² was selected. From the corridor, where also patient beds are made available, the adjoining doors lead to the examination and surgery rooms. It is thus a sensitive main thoroughfare in a hospital.

 

Situation of the previously installed lighting

The old lighting in the circulation areas was fitted with compact fluorescent lamps of 13 watts. These lights burned at full power around the clock. Including the ballast, the power consumption was 14.6 watts. With a total of 55 lamps, this resulted in an installed power of 803 watts. The lighting strength during operation was 40 lux on average.

Situation of the new installed lighting

The new lighting is equipped with 22 LED panels from Ledvance. The measured power at full load is 33 watts. During operation, it is set to a maximum of 16.7 watts (50%). The orientation light is 10% of the maximum luminous flux, having a power consumption of 4.8 watts.

The LED lamps are divided into 10 groups of 2 to 4 lamps each. Each group is individually controlled by a theRonda presence detector from Theben, with the presence detectors switching each individual light group from orientation light (10%) to basic light (50% of the installed power) depending on presence. After only 10 seconds without presence, each group goes back to orientation light. On an average day, the light switches on and off around 350 times – that's over 120,000 switching cycles a year.

The luminous flux output of the lamps, the time delay of the lamps, and the orientation light are programmed via "theSenda Plug" smartphone app together with theSenda B remote control.

 

Bottom line: less power consumption and higher lighting strength

Compared to the previous lighting, 82% of energy is saved (incl. power consumption of presence detectors) – with an increase in lighting strength from 40 to over 200 lux. 54% of the savings are due to lighting control, while 46% can be attributed to the higher efficiency of LED lamps. While the previous lighting was well above the limit of the SIA 387/4 standard, the new lighting is below the target value for hospital corridors.

The setting of the presence detectorsmay be classified as very advanced for this type of usage and can be used as an example for other hospitals.

 

Theben products used: