Open access publications in the SLU publication database

The Swedish animal production have potential to save 4-9 million € per year in electric energy for lighting. Two light pipe system, Solatube® and Velux® were installed in identical pig stables to determine if required light intensity, Daylight Autonomy (DA) and reduced consumption of electricity for lighting could be met. The of light intensity requirement for pigs are at least 40 lux for a minimum period of 8 hours/day (EU directive). According to the Swedish Board of Agriculture pig stables should have windows or other means of daylight inlets. Wide buildings dominate animal production, but windows have limited effect to bring daylight to rear spaces in deep buildings while the window area is relative small and far away. For growing animals, like pigs and poultry, needing insulated buildings, the new daylight systems could mean an increased use of natural daylight. Three light sensors continuesly measured the daylight received in each stable relative to an outdoor sensor. If the horizontal illuminance at pig height went below 40 lux during 08.00-16.00, an on/off sensor turned on the lighting and the electricity consumption was recorded. Data analysis was carried out on a monthly basis, where the condition for a value to be recorded as a DA value was that the electrical consumption should be zero. Daylight Factor (DF) was measured in a 9 point grid at two levels. The mean annual DA were 48 and 55% for Velux and Solatube respectively. Solatube light pipes delivered significantly more DA hours than Velux. The most common frequency range for both stables were from 0-160 lux, corresponding to approx. 82 and 83% of the daylight time for Velux and Solatube, respectively. DF differencies were received at 1.5 m above floor level. Solatube had a more homogeneous DF values distribution (0.05-0.59), which implies a more effective light diffusion. The results show that considerable electric energy savings could be achieved in animal production by use of lightpipes in farm buildings. Lightpipes could offer energy savings in corridors and toilets for humans especially if combined with dimmable daylight-linked electric lighting systems.