Very shallow geothermal system to improve the energy efficiency in dairy barns

In cow barns, milk cooling is a crucial activity to guarantee the product safety. This operation is performed at every milking and is highly energy consuming. A few farms in the Mediterranean region installed pre-cooling systems taking advantage of free heat exchange between the milk and the low-temperature water taken from well or aqueducts and used for cow drinking and soaking. Ideally, this system can both reduce the milk temperature before the refrigerator intake and at the same time rise the water temperature. This latter aspect plays an important role, avoiding health risks and production losses, since low temperatures often discourage the animals from drinking. Since milking is performed twice a day in limited time in barns equipped with milking parlor, the system shall face two main goals to be effective: to avoid water waste and to keep water temperature between milking. This work presents a system integrating water-milk heat exchangers with a very shallow geothermal system. A newly developed geo-exchanger, designed with double circuit spirals, can exchange the milk heat partially with the ground and partially with a second fluid (cow drinking and soaking water). Moreover, it can keep the water at the proper temperature for hours taking advantage of ground thermal characteristics. The study shows that the proposed system enhances the milk-water free cooling performance, rises and keeps the water temperature, and, if properly sized, avoids water wasted. The study is applied on a case study barn located in Bologna countryside (Italy) and based on experimental data achieved from a thermal response test campaign carried on a shallow geothermal system in the University laboratories.