ENERGY SAVING USING DAYLIGHT SENSORS

These are used widely for outside lights and for street lighting. However lighting technology now allows these to be used in offices as well.

If an office has windows letting in plenty of daylight, there is scope for dimming the lights. These dimming units supply a voltage to suitable lighting to maintain a constant light level. This is shown in the diagram below.

Enough daylight – lighting off

Reduced daylight – Lighting dimmed

Night – Lighting on

CASE STUDY

Saving £263 each year by using daylight sensors

In a large call centre the entire side of the building has windows which are south facing. For around 6 hours in the spring & summer and 3 hours in the autumn & winter this call centre gets enough daylight for the lights to be switched off. The power consumption of these lights was 2.5 kW.

The cost to install the light level detectors was £450

The annual savings obtained by using daylight sensors was 4.5 (average hours per day) x 5 (days per week) x 52 (weeks per year) x 2.5 (kW) x 0.09 (cost per kWh) = £263