In order to compare the energy advantage of AQUAFAN with conventional cooling towers (WCN), we have to take a look at these systems in practical operational conditions. Installation are required to deliver design conditions for maximum performance which rarely occurs in practical situations for HVAC (coinciding of Maximum Wet Bulb Temp and Maximum Heat Load).
Basing on the average WBT over the year as published by ASHRAE and assuming a heat load averaging 80%, we will compare the practical operations of AQUAFAN and conventional cooling towers. At design conditions, AQUAFAN consumes energy close to that of a comparable conventional cooling tower. The cooling tower is only one item in a cooling water system. The cooling water pumps and fans take care of water and air circulation and, by doing so, consume energy. A cooling tower is designed to give maximum ambient temperature (WBT or wet bulb temperature). However, this wet bulb temperature is not reached for a great part of the year.
The table shows the energy comparison for the total system of pump and fan energy in conventional. The consumption at 100, 80 and 60% heat load against the average WBT is projected for the AQUAFAN operating in combination with a VFD-equipped pump and a conventional WCD cooling tower equipped with VFD at the fan motor.Using 80% heat load as a fair and safe estimation of the real situation, the calculation model demonstrates considerable energy savings of AQUAFAN.
In situations where the cooling demand is around 75% of the design conditions, AQUAFAN cooling towers use 50% less energy compared to conventional cooling towers. During practical operations, the VFD-equipped AQUAFAN start saving energy by adjusting the amount of cooling water to the variable conditions. When the cooling water coming out of the condenser is below set temperature, the water flow will be reduced resulting in reduced fan speed as well. Savings are exponentially increased with decreasing cooling demands as pump energy consumptions are a cubic law of the pump volume.