Feasibility assessment of recovering waste heat from enclosed cattle barns for forage drying systems

Enclosed barns, designed for improving animal welfare, are energy-intensive facilities. The demand for cooling capacity to maintain animal thermal comfort escalates during the summer, and year after year, global warming creates increasingly challenging conditions for temperature control. Drying forage constitutes a second significant energy-intensive process, requiring a large amount of thermal power. This work focuses on evaluating the economic and energetic benefits of integrating the forage drying process with a low-temperature waste heat recovery system in a dairy farm. In this context, the optimal solution lies in exploiting the waste heat generated by the enclosed barn chiller as an energy source to aid forage drying, thereby maximizing energy efficiency. The system outlined here uses a hydronic system to extract excess heat from the barn and convey it to the drying process, reducing overall expenses. The results of this comprehensive technical and economic feasibility study demonstrate the viability of implementing such a heat recovery system in the facility. Notably, recovering thermal power from the barn chiller allows for saving about 30 % of the fuel dedicated to the dryer burner (between 3.5 and 5.5 kWh per day per cow depending on the ambient conditions), guaranteeing a short payback period. Moreover, the carbon footprint of the farm can be drastically reduced, cutting more than 250 kg of CO2equivalent emissions per cow each year.