4/ You are operating a fan with the characteristics shown in thefigure below. The 25 kW fan currently operates continuously at fullspeed with the flow reduced to 90% of its rated capacity usingdownstream dampers. An evaluation reveals that there is inadequatefresh air being introduced into the building during the day, andtoo much is supplied at night. The flow rate needs to increase to100% from 7am to 7pm, and can be reduced to 50% at night. Whatwould be the CHANGE in energy costn per year if this change wasdone using either downstream dampers, or using a 97% efficient VSD?
ηmot = 0.96 at the nominal speed
ηmot = 0.94 at 90% of the nominal speed
ηmot = 0.89 at 50% of the nominal speed
Electricity costs $0.15/kWh, no impact on demand charges
