Energy Efficiency at the Sir Wilfrid Laurier School Board

An informational and awareness website

Optimization of the ventilation

In large buildings, ventilation systems are required to circulate air and ensure proper indoor air quality. These ventilation systems have large fans which consume a lot of electricity.  The fans usually operate at full speed during the day and don’t have any modulation capability, meaning
they are either fully on or off.  With specialized electronics called variable speed drives (VSD), the fan speed can be modulated according to the real-time demand and occupancy levels.  By slowing the fans when demand is lower, significant energy savings can be achieved.
Fresh air requirements in a building vary according to the occupancy level and the temperature
set points. Sensors installed in the ventilation ducts can monitor the air quality in real-time. They transmit the data to the VSDs which, in turn, adjusts the fan speed by changing the amount of electric current provided to the motor. This way, the air quality is maintained at proper levels
while the fans do not circulate more air than is needed. Also, since the systems are circulating
less air, less heated air is exhausted and lost to the outdoors.  VSDs can thus greatly reduce the electricity consumption of the fan motors and also decrease the heating demand in the winter.

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