Aneco friendly solar pv milk chiller operated with dc compressor

Abstract

India is one of the leading milk producing nations, which produced 187.7 million tonnes of milk in the year 2018-19. As per the Food and Agriculture Organization (FAO) and WHO regulations, milk has to be chilled to 4-5 -3 hours after milking, in order to control the microbial count in the raw milk and to maintain the quality of the raw milk. Refrigeration is the exclusive means to preserve milk. Owing to no/intermittent grid power supply in rural villages of India, milk chilling by refrigeration is hampered. This issue can be addressed by using solar PV powered refrigeration. Considering the scenario of a small milk farmer where 10 liters of milk was collecting in the morning and 10 liters in the evening, a milk chiller of 20 liters capacity was built to operate using DC compressors to utilize solar PV output instead of conventional energy and an Ice Bank Tank (IBT) was used instead of batteries. Two hermetically sealed DC compressors BD35F and BD35K operating with HFC-134a and HC-600a refrigerants were used with individual refrigerant circuits. The use of two compressors enabled the operation of at least one compressor when the solar insolation was low or during overcast conditions. Initially a milk chiller with a vertical milk tank surrounded with an IBT of 14 liters capacity was fabricated and tested. The vertical milk chiller had some drawbacks namely temperature variation in the IBT along the height resulting in non-uniform milk cooling. To circumvent the temperature gradient in the vertical direction, the milk chiller was made to be horizontal with a larger IBT of 40 liters capacity to store more cold energy. The milk chiller was subjected to capillary tube length optimisation and refrigerant charge optimisation for both the HFC-134a and the HC-600a circuitsiv independently. newline