Small‐Scale Milk Pasteurization and Chilling Using Hybrid Solar–Thermal and Photovoltaic Systems for Off‐Grid Areas

Due to the lack of access to grid electricity, milk preservation is a significant challenge in pastoral and rural areas of most African countries, despite the large volume of milk produced. Integrating milk pasteurization and chilling with a hybrid solar–thermal and photovoltaic system can enhance milk preservation, enabling milk to reach the market and generate income for pastoral and rural communities in off‐grid areas of Africa. In this study, a MATLAB program was developed based on a transient model of a solar heating system and refrigeration system that uses a DC compressor powered by a photovoltaic panel for dynamic adaptive simulation of milk preservation temperature. The model facilitates reliable sizing of the evacuated‐tube solar collector area, the PV array, and the DC compressor capacity for pasteurization and chilling based on the given milk volume for a particular location. Moreover, the annual performance of the system with a 50‐L milk capacity at Semera, Ethiopia, was investigated. The simulation results show that milk can be effectively pasteurized at temperatures of 63°C and higher after water is heated for 30 min at 10 a.m. Consequently, in less than 3 h, the milk chilling system can lower the milk′s temperature to 4°C. During the critical month, the time required was around 3 h and 10 min. Furthermore, the results show that the refrigeration cycle′s coefficient of performance (COP) at the start of operation at 1800 rpm is 1.65. For the 24‐V compressor, the highest COP recorded was 2.16 at a maximum speed of 3600 rpm. Nevertheless, when using the same compressor model with 48 V, the COP begins to decrease as the rpm exceeds 3600 rpm and eventually reaches a maximum speed of 6500 rpm. Hence, it can be concluded that solar‐powered milk pasteurization and chiller can be used to alleviate the problem of milk preservation and market inaccessibility facing pastoralists and small‐scale dairy farms in off‐grid areas of semi‐arid tropical regions.