Feasibility study of environmental control of dairy barns using air conditioning or evaporative cooling

Many dairy producers are interested in a controlled indoor environment to maintain thermal comfort of lactating cows in the summer. Conventional air conditioning (AC) is an efficient way to cool air, but has not been used much for commercial herds due to the high capital cost and electricity usage. However, compared with the economic loss incurred by heat stress, the AC system is still a viable option to farmers. The purpose of this research was to study the energy costs and investigate the production benefits of an air conditioning system compared to an evaporative cooling (EC) system in a mechanically ventilated dairy barn. A dynamic system model was developed to simulate in-barn environmental conditions for two cooling systems in four dairy production zones characterized by climate data for major cities (Tampa, FL, Sacramento, CA, Syracuse, NY, and Madison, WI). The results show that an AC system can effectively reduce the heat stress (keeping the highest indoor temperature of 23-27.4°C) compared to the EC system (which allowed the highest indoor temperature at 26.5-31.7°C) in four locations. The electrical energy usage of the AC systems can be significantly reduced by decreasing the ventilation rate and increasing cooling capacities (73% reduction for Tampa, 30-36% reduction for the three remaining cities). This analysis addressed the importance of assessing the temperature and humidity profiles in the AC system design and can assist dairy farmers in selecting appropriate advanced cooling systems for lactating dairy barns.