Optimal energy saved using variable air ventilation for cold rooms

This paper determines the effect of an optimum point for energy savings between a variable air ventilation fan using variable speed drive (VSD) and a constant air ventilation evaporator fan. Each reduced speed and thus saved energy. A suitable VSD operation optimum point was determined without disturbing cold room indoor performance. The experiments were carried out in a small cold room 2.5 m long by 2.5 m wide and 3 m high, in which the VSD was mounted on a fan. Air velocity, temperature, and humidity sensors were placed in different positions inside the room and humidity, surface and centre temperature tests conducted to an optimum VSD operation point. The power consumed by the cold room under different evaporator fan speeds, was respectively: 1.319 kW at maximum fan speed, 1.296 kW at 90% fan speed, 1.282 kW at 80% fan speed, 1.271 kW at 70% fan speed, 1.264 kW at 60% fan speed, and 1.257 kW at 50% fan speed. Slowing the evaporator fan speed to optimal produced an energy saving of 26.6 kWh or 33.6% over 79 kWh or 100% of energy consumed per month by the evaporator fan supply.