Application of solar thermal heating and cooling energy to dairy processes: a case study

The dairy industry is one of the growing sectors in the food industry with significant thermal energy demand for their processes and temperature requirement of maximum 200 ℃. The use of solar energy for those process will reduce the fossil fuel dependency, greenhouse gas emission, environmental pollution and help to meet emission targets. Therefore, this study investigates the thermal requirements of a dairy company and provides a schematic of two integration concepts between the solar thermal energy system and their processes which are through the common energy supply line and inlets of individual processes. The study involves a case study that uses natural gas-powered boilers, and electrical powered chiller, ice banks and refrigerators to meet heating and cooling energy demand for the processes such as pasteurisation, fermentation and cold milk tanks. The overall energy consumption of the dairy processes is 1315 kWh at the full capacity operation, of which 1195 kWh can be theoretically replaced by the solar thermal energy. The temperature requirements of the processes are between 0 ℃ and 4 ℃ for cooling, and 170 ℃ for the heating. These thermal requirements can be met by using either parabolic trough or linear Fresnel solar thermal collectors along with thermal energy storage. The solar thermal energy integration concepts developed at supply level and process level use steam drum and absorption chiller to transfer the solar energy to the processes. The supply level integration has more advantages due to its easier control over the conventional and solar energy systems.