Improving the energy efficiency and milk quality with CO2 refrigeration systems with heat recovery on New Zealand dairy farms.

At the average New Zealand dairy farm about 6,131 litres of milk is produced daily on average from 420 cows over a 300 day period. The cows are dry for about 8-10 weeks during May to July. The warm milk from the cow is pumped into a tank with a part refrigerated wall and slowly cooled with an agitator providing movement of the milk past the cooled tank wall.
It is proposed that a small CO2 system with heat recovery produces chilled and hot water at low off peak electricity rates. Chilled water equal to 1.5 times the daily milk production is stored, as is hot water for daily CIP and general cleaning.
During milking the milk is cooled very quickly to a temperature not exceeding 7°C before it enters the storage tank. Below 7°C salmonella and E-coli do not grow. In addition to enhanced food safety, other benefits of the proposed CO2 refrigeration technology are improved product quality, reduced energy consumption and costs, and reduced direct and indirect Global Warming Emissions.